Strong-field ionization of clusters using two-cycle pulses at 1.8 μm

PubMed Central

Schütte, Bernd; Ye, Peng; Patchkovskii, Serguei; Austin, Dane R.; Brahms, Christian; Strüber, Christian; Witting, Tobias; Ivanov, Misha Yu.; Tisch, John W. G.; Marangos, Jon P.

2016-01-01

The interaction of intense laser pulses with nanoscale particles leads to the production of high-energy electrons, ions, neutral atoms, neutrons and photons. Up to now, investigations have focused on near-infrared to X-ray laser pulses consisting of many optical cycles. Here we study strong-field ionization of rare-gas clusters (103 to 105 atoms) using two-cycle 1.8 μm laser pulses to access a new interaction regime in the limit where the electron dynamics are dominated by the laser field and the cluster atoms do not have time to move significantly. The emission of fast electrons with kinetic energies exceeding 3 keV is observed using laser pulses with a wavelength of 1.8 μm and an intensity of 1 × 1015 W/cm2, whereas only electrons below 500 eV are observed at 800 nm using a similar intensity and pulse duration. Fast electrons are preferentially emitted along the laser polarization direction, showing that they are driven out from the cluster by the laser field. In addition to direct electron emission, an electron rescattering plateau is observed. Scaling to even longer wavelengths is expected to result in a highly directional current of energetic electrons on a few-femtosecond timescale. PMID:28009012

Carrier-envelope phase-dependent ionization of Xe in intense, ultrafast (two-cycle) laser fields

NASA Astrophysics Data System (ADS)

Vasa, Parinda; Dharmadhikari, Aditya K.; Mathur, Deepak

2018-01-01

We report an experimental study that shows the dependence of the tunnel ionization of Xe by two-cycle, intense, near infrared light on the carrier-envelope-phase (CEP) of incident laser pulses. At low values of the optical field (E), the ionization yield is found to be maximum for cos-like pulses; the CEP dependence of the ion yield becomes stronger for higher charge states. At higher E-values, the CEP dependence either washes out or flips. A simple phenomenological model is used to confirm that our results fall within the ambit of the current understanding of ionization dynamics in strong, ultrashort optical fields. In the observed tunnel ionization of Xe, CEP effects appear to persist for longer, eight-cycle, pulses. Electron rescattering is observed to play a relatively unimportant role in the observed CEP dependence. These results provide fresh perspectives in the ionization mechanisms of multielectron systems in the few-cycle regime.

Waveform control of orientation-dependent ionization of DCl in few-cycle laser fields.

PubMed

Znakovskaya, I; von den Hoff, P; Schirmel, N; Urbasch, G; Zherebtsov, S; Bergues, B; de Vivie-Riedle, R; Weitzel, K-M; Kling, M F

2011-05-21

Strong few-cycle light fields with stable electric field waveforms allow controlling electrons on time scales down to the attosecond domain. We have studied the dissociative ionization of randomly oriented DCl in 5 fs light fields at 720 nm in the tunneling regime. Momentum distributions of D(+) and Cl(+) fragments were recorded via velocity-map imaging. A waveform-dependent anti-correlated directional emission of D(+) and Cl(+) fragments is observed. Comparison of our results with calculations indicates that tailoring of the light field via the carrier envelope phase permits the control over the orientation of DCl(+) and in turn the directional emission of charged fragments upon the breakup of the molecular ion. © The Owner Societies 2011

Multi-millijoule few-cycle mid-infrared pulses through nonlinear self-compression in bulk

PubMed Central

Shumakova, V.; Malevich, P.; Ališauskas, S.; Voronin, A.; Zheltikov, A. M.; Faccio, D.; Kartashov, D.; Baltuška, A.; Pugžlys, A.

2016-01-01

The physics of strong-field applications requires driver laser pulses that are both energetic and extremely short. Whereas optical amplifiers, laser and parametric, boost the energy, their gain bandwidth restricts the attainable pulse duration, requiring additional nonlinear spectral broadening to enable few or even single cycle compression and a corresponding peak power increase. Here we demonstrate, in the mid-infrared wavelength range that is important for scaling the ponderomotive energy in strong-field interactions, a simple energy-efficient and scalable soliton-like pulse compression in a mm-long yttrium aluminium garnet crystal with no additional dispersion management. Sub-three-cycle pulses with >0.44 TW peak power are compressed and extracted before the onset of modulation instability and multiple filamentation as a result of a favourable interplay between strong anomalous dispersion and optical nonlinearity around the wavelength of 3.9 μm. As a manifestation of the increased peak power, we show the evidence of mid-infrared pulse filamentation in atmospheric air. PMID:27620117

Coherent control of high-order-harmonic generation via tunable plasmonic bichromatic near fields in a metal nanoparticle

NASA Astrophysics Data System (ADS)

Yang, Wen-Xing; Xie, Xiao-Tao; Chen, Ai-Xi; Huang, Ziwen; Lee, Ray-Kuang

2016-05-01

We present a theoretical investigation of high-order-harmonic generation (HHG) via bichromatic plasmonic near fields with metal nanoparticles. Bichromatic plasmonic near fields, which depend on temporal waveform synthesis, are generated when a metallic nanoparticle subjected to a moderate-intensity (<1012W /cm2 ) bichromatic few-cycle pulse. By means of a windowed Fourier transform of the time-dependent acceleration, we show that the differences in energies and level crossing between the adiabatic states of a two-level Hamiltonian are responsible for the cutoff energy of harmonics. Thus, we can manipulate the adiabatic states, and consequently the HHG spectra, by means of the bichromatic plasmonic near fields. In contrast to the case of a monochromatic field alone, a significant cutoff extension can be achieved via optimization of the bichromatic few-cycle pulse. Moreover, the supercontinuum in the bichromatic field shows a higher energy spectrum along with a broader bandwidth, which is beneficial for the efficient generation of broadband-isolated ultrashort extreme ultraviolet pulses from few-cycle laser fields.

From few-cycle femtosecond pulse to single attosecond pulse-controlling and tracking electron dynamics with attosecond precision

NASA Astrophysics Data System (ADS)

Wang, He

The few-cycle femtosecond laser pulse has proved itself to be a powerful tool for controlling the electron dynamics inside atoms and molecules. By applying such few-cycle pulses as a driving field, single isolated attosecond pulses can be produced through the high-order harmonic generation process, which provide a novel tool for capturing the real time electron motion. The first part of the thesis is devoted to the state of the art few-cycle near infrared (NIR) laser pulse development, which includes absolute phase control (carrier-envelope phase stabilization), amplitude control (power stabilization), and relative phase control (pulse compression and shaping). Then the double optical gating (DOG) method for generating single attosecond pulses and the attosecond streaking experiment for characterizing such pulses are presented. Various experimental limitations in the attosecond streaking measurement are illustrated through simulation. Finally by using the single attosecond pulses generated by DOG, an attosecond transient absorption experiment is performed to study the autoionization process of argon. When the delay between a few-cycle NIR pulse and a single attosecond XUV pulse is scanned, the Fano resonance shapes of the argon autoionizing states are modified by the NIR pulse, which shows the direct observation and control of electron-electron correlation in the temporal domain.

Carrier-envelope phase dependence of the directional fragmentation and hydrogen migration in toluene in few-cycle laser fields.

PubMed

Li, Hui; Kling, Nora G; Förg, Benjamin; Stierle, Johannes; Kessel, Alexander; Trushin, Sergei A; Kling, Matthias F; Kaziannis, Spyros

2016-07-01

The dissociative ionization of toluene initiated by a few-cycle laser pulse as a function of the carrier envelope phase (CEP) is investigated using single-shot velocity map imaging. Several ionic fragments, CH3 (+), H2 (+), and H3 (+), originating from multiply charged toluene ions present a CEP-dependent directional emission. The formation of H2 (+) and H3 (+) involves breaking C-H bonds and forming new bonds between the hydrogen atoms within the transient structure of the multiply charged precursor. We observe appreciable intensity-dependent CEP-offsets. The experimental data are interpreted with a mechanism that involves laser-induced coupling of vibrational states, which has been found to play a role in the CEP-control of molecular processes in hydrocarbon molecules, and appears to be of general importance for such complex molecules.

Influence of the carrier-envelope phase of few-cycle pulses on ponderomotive surface-plasmon electron acceleration.

PubMed

Irvine, S E; Dombi, P; Farkas, Gy; Elezzabi, A Y

2006-10-06

Control over basic processes through the electric field of a light wave can lead to new knowledge of fundamental light-matter interaction phenomena. We demonstrate, for the first time, that surface-plasmon (SP) electron acceleration can be coherently controlled through the carrier-envelope phase (CEP) of an excitation optical pulse. Analysis indicates that the physical origin of the CEP sensitivity arises from the electron's ponderomotive interaction with the oscillating electromagnetic field of the SP wave. The ponderomotive electron acceleration mechanism provides sensitive (nJ energies), high-contrast, single-shot CEP measurement capability of few-cycle laser pulses.

Generation of coherent terahertz radiation in ultrafast laser-gas interactionsa)

NASA Astrophysics Data System (ADS)

Kim, Ki-Yong

2009-05-01

The generation of intense terahertz radiation in ultrafast laser-gas interactions is studied on a basis of transient electron current model. When an ultrashort pulse laser's fundamental and its second harmonic fields are mixed to ionize a gas, a nonvanishing, directional photoelectron current can be produced, which simultaneously emits terahertz radiation in the far field. Here, the generation mechanism is examined with an analytic derivation and numerical simulations, in which tunneling ionization and subsequent electron motion in the combined laser field play a key role. In the simulations, three types of laser-gas interactions are considered: (i) mixing the fundamental and its second harmonic fields, (ii) mixing nonharmonic, two-color fields, and (iii) focusing single-color, few-cycle pulses. In these interactions, terahertz generation and other nonlinear effects driven by the transient current are investigated. In particular, anticorrelation between terahertz and second (or third) harmonic generation is observed and analyzed.

Attosecond control of electronic processes by intense light fields.

PubMed

Baltuska, A; Udem, Th; Uiberacker, M; Hentschel, M; Goulielmakis, E; Gohle, Ch; Holzwarth, R; Yakovlev, V S; Scrinzi, A; Hänsch, T W; Krausz, F

2003-02-06

The amplitude and frequency of laser light can be routinely measured and controlled on a femtosecond (10(-15) s) timescale. However, in pulses comprising just a few wave cycles, the amplitude envelope and carrier frequency are not sufficient to characterize and control laser radiation, because evolution of the light field is also influenced by a shift of the carrier wave with respect to the pulse peak. This so-called carrier-envelope phase has been predicted and observed to affect strong-field phenomena, but random shot-to-shot shifts have prevented the reproducible guiding of atomic processes using the electric field of light. Here we report the generation of intense, few-cycle laser pulses with a stable carrier envelope phase that permit the triggering and steering of microscopic motion with an ultimate precision limited only by quantum mechanical uncertainty. Using these reproducible light waveforms, we create light-induced atomic currents in ionized matter; the motion of the electronic wave packets can be controlled on timescales shorter than 250 attoseconds (250 x 10(-18) s). This enables us to control the attosecond temporal structure of coherent soft X-ray emission produced by the atomic currents--these X-ray photons provide a sensitive and intuitive tool for determining the carrier-envelope phase.

Dynamics of light-field control of molecular dissociation at the few-cycle limit.

PubMed

Tong, X M; Lin, C D

2007-03-23

We studied the laser-molecule interaction dynamics that leads to the asymmetric D+ ion ejection in the dissociative ionization of D2 molecules observed recently in Kling et al. [Science 312, 246 (2006)10.1126/science.1126259]. By changing the carrier-envelope phase, we showed that the asymmetry is a consequence of manipulating the initial ionization and the rescattering of the electrons within one optical cycle of the laser. The result illustrates the feasibility of coherent control of reaction dynamics at the attosecond time scale.

Passive and hybrid mode locking in multi-section terahertz quantum cascade lasers

NASA Astrophysics Data System (ADS)

Tzenov, P.; Babushkin, I.; Arkhipov, R.; Arkhipov, M.; Rosanov, N.; Morgner, U.; Jirauschek, C.

2018-05-01

It is believed that passive mode locking is virtually impossible in quantum cascade lasers (QCLs) because of too fast carrier relaxation time. Here, we revisit this possibility and theoretically show that stable mode locking and pulse durations in the few cycle regime at terahertz (THz) frequencies are possible in suitably engineered bound-to-continuum QCLs. We achieve this by utilizing a multi-section cavity geometry with alternating gain and absorber sections. The critical ingredients are the very strong coupling of the absorber to both field and environment as well as a fast absorber carrier recovery dynamics. Under these conditions, even if the gain relaxation time is several times faster than the cavity round trip time, generation of few-cycle pulses is feasible. We investigate three different approaches for ultrashort pulse generation via THz quantum cascade lasers, namely passive, hybrid and colliding pulse mode locking.

Carrier-envelope phase dependence of the directional fragmentation and hydrogen migration in toluene in few-cycle laser fields

PubMed Central

Li, Hui; Kling, Nora G.; Förg, Benjamin; Stierle, Johannes; Kessel, Alexander; Trushin, Sergei A.; Kling, Matthias F.; Kaziannis, Spyros

2016-01-01

The dissociative ionization of toluene initiated by a few-cycle laser pulse as a function of the carrier envelope phase (CEP) is investigated using single-shot velocity map imaging. Several ionic fragments, CH3+, H2+, and H3+, originating from multiply charged toluene ions present a CEP-dependent directional emission. The formation of H2+ and H3+ involves breaking C-H bonds and forming new bonds between the hydrogen atoms within the transient structure of the multiply charged precursor. We observe appreciable intensity-dependent CEP-offsets. The experimental data are interpreted with a mechanism that involves laser-induced coupling of vibrational states, which has been found to play a role in the CEP-control of molecular processes in hydrocarbon molecules, and appears to be of general importance for such complex molecules. PMID:26958589

Effect of the carrier-envelope phase of the driving laser field on the high-order harmonic attosecond pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng Zhinan; Li Ruxin; Yu Wei

2003-01-01

The effect of the carrier-envelope phase of a few-cycle driving laser field on the generation and measurement of high-order harmonic attosecond pulses is investigated theoretically. We find that the position of the generated attosecond soft-x-ray pulse in the cutoff region is locked to the oscillation of the driving laser field, but not to the envelope of the laser pulse. This property ensures the success of the width measurement of an attosecond soft-x-ray pulse based on the cross correlation between the attosecond pulse and its driving laser pulse [M. Hentschel et al., Nature (London) 414, 509 (2001)]. However, there still existsmore » a timing jitter of the order of tens of attoseconds between the attosecond pulse and its driving laser field. We also propose a method to detect the carrier-envelope phase of the driving laser field by measuring the spatial distribution of the photoelectrons induced by the attosecond soft-x-ray pulse and its driving laser pulse.« less

Progress in Attosecond Metrology

NASA Astrophysics Data System (ADS)

Kienberger, R.; Krausz, F.

Fundamental processes in atoms, molecules, as well as condensed matter are triggered or mediated by the motion of electrons inside or between atoms. Electronic dynamics on atomic length scales tends to unfold within tens to thousands of attoseconds (1 as = 10-18 s). Recent breakthroughs in laser science are now opening the door to watching and controlling these hitherto inaccessible microscopic dynamics. The key to accessing the attosecond time domain is the control of the electric field of (visible) light, which varies its strength and direction within less than a femtosecond (1 fs = 1000 as). Atoms exposed to a few oscillation cycles of intense laser light are able to emit a single XUV burst lasting less than 1 fs. Full control of the evolution of the electromagnetic field in laser pulses comprising a few wave cycles have recently allowed the reproducible generation and measurement of isolated 250-as XUV pulses, constituting the shortest reproducible events and fastest measurement to date. These tools have enabled us to visualize the oscillating electric field of visible light with an attosecond "oscilloscope" and observing the motion of electrons in and around atoms in real time. Recent experiments hold promise for the development of an attosecond hard X-ray source, which may pave the way toward 4D electron imaging with subatomic resolution in space and time.

Transition of recollision trajectories from linear to elliptical polarization

DOE PAGES

Li, Yingbin; Yu, Benhai; Tang, Qingbin; ...

2016-03-15

Using a classical ensemble method, we revisit the topic of recollision and nonsequential double ionization with elliptically polarized laser fields. We focus on how the recollision mechanism transitions from short trajectories with linear polarization to long trajectories with elliptical polarization. Furthermore, we propose how this transition can be observed by measuring the carrier-envelop-phase dependence of the correlated electron momentum spectra using currently available few-cycle laser pulses.

Plasmon-shaped polarization gating for high-order-harmonic generation

NASA Astrophysics Data System (ADS)

Wang, Feng; He, Lixin; Chen, Jiawei; Wang, Baoning; Zhu, Xiaosong; Lan, Pengfei; Lu, Peixiang

2017-12-01

We present a plasmon-shaped polarization gating for high-order-harmonic generation by using a linearly polarized laser field to illuminate two orthogonal bow-tie nanostructures. The results show that when these two bow-tie nanostructures have nonidentical geometrical sizes, the transverse and longitudinal components of the incident laser field will experience different phase responses, thus leading to a time-dependent ellipticity of laser field. For the polarizing angle of incident laser field in the range from 45∘ to 60∘, the dominant harmonic emission is gated within the few optical cycles where the laser ellipticity is below 0.3. Then sub-50-as isolated attosecond pulses (IAPs) can be generated. Such a plasmon-shaped polarization gating is robust for IAP generation against the variations of the carrier-envelope phases of the laser pulse. Moreover, by changing the geometrical size of one of the bow-tie nanostructures, the electron dynamics can be effectively controlled and the more efficient supercontinuum as well as IAP can be generated.

Analytical description of generation of the residual current density in the plasma produced by a few-cycle laser pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silaev, A. A., E-mail: silaev@appl.sci-nnov.ru; Vvedenskii, N. V., E-mail: vved@appl.sci-nnov.ru; University of Nizhny Novgorod, Nizhny Novgorod 603950

2015-05-15

When a gas is ionized by a few-cycle laser pulse, some residual current density (RCD) of free electrons remains in the produced plasma after the passage of the laser pulse. This quasi-dc RCD is an initial impetus to plasma polarization and excitation of the plasma oscillations which can radiate terahertz (THz) waves. In this work, the analytical model for calculation of RCD excited by a few-cycle laser pulse is developed for the first time. The dependences of the RCD on the carrier-envelope phase (CEP), wavelength, duration, and intensity of the laser pulse are derived. It is shown that maximum RCDmore » corresponding to optimal CEP increases with the laser pulse wavelength, which indicates the prospects of using mid-infrared few-cycle laser pulses in the schemes of generation of high-power THz pulses. Analytical formulas for optimal pulse intensity and maximum efficiency of excitation of the RCD are obtained. Basing on numerical solution of the 3D time-dependent Schrödinger equation for hydrogen atoms, RCD dependence on CEP is calculated in a wide range of wavelengths. High accuracy of analytical formulas is demonstrated at the laser pulse parameters which correspond to the tunneling regime of ionization.« less

Carrier-Envelope Phase Effects in Plasma-Based Electron Acceleration with Few-Cycle Laser Pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nerush, E. N.; Kostyukov, I. Yu.

2009-07-17

Carrier-envelope phase effects during the interaction of relativistically intense few-cycle laser pulses with a plasma are studied in the 'bubble' regime when an electron cavity (bubble) is formed behind the pulse. We show that for few-cycle laser pulses the cavity shape becomes asymmetric and depends strongly on the carrier-envelope phase. The carrier-envelope phase varies when the laser pulse propagates in plasma, which causes transverse oscillations of the cavity. Furthermore, the beam of electrons trapped by the cavity becomes modulated in the polarization plane. To describe these effects we derive an analytical model extended beyond the ponderomotive approximation. The degree ofmore » plasma cavity asymmetry as a function of the laser-plasma parameters is calculated. The obtained results are verified by particle-in-cell simulations.« less

High-order harmonic generation by atoms in a few-cycle laser pulse: Carrier-envelope phase and many-electron effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frolov, M. V.; Manakov, N. L.; Silaev, A. A.

2011-02-15

Analytic formulas describing high-order harmonic generation (HHG) by atoms in a short laser pulse are obtained quantum mechanically in the tunneling limit. These results provide analytic expressions of the three-step HHG scenario, as well as of the returning electron wave packet, in a few-cycle pulse. Our results agree well with those of numerical solutions of the time-dependent Schroedinger equation for the H atom, while for Xe they predict many-electron atomic dynamics features in few-cycle HHG spectra and significant dependence of these features on the carrier-envelope phase of a laser pulse.

High-order harmonic generation driven by inhomogeneous plasmonics fields spatially bounded: influence on the cut-off law

NASA Astrophysics Data System (ADS)

Neyra, E.; Videla, F.; Ciappina, M. F.; Pérez-Hernández, J. A.; Roso, L.; Lewenstein, M.; Torchia, G. A.

2018-03-01

We study high-order harmonic generation (HHG) in model atoms driven by plasmonic-enhanced fields. These fields result from the illumination of plasmonic nanostructures by few-cycle laser pulses. We demonstrate that the spatial inhomogeneous character of the laser electric field, in a form of Gaussian-shaped functions, leads to an unexpected relationship between the HHG cutoff and the laser wavelength. Precise description of the spatial form of the plasmonic-enhanced field allows us to predict this relationship. We combine the numerical solutions of the time-dependent Schrödinger equation (TDSE) with the plasmonic-enhanced electric fields obtained from 3D finite element simulations. We additionally employ classical simulations to supplement the TDSE outcomes and characterize the extended HHG spectra by means of their associated electron trajectories. A proper definition of the spatially inhomogeneous laser electric field is instrumental to accurately describe the underlying physics of HHG driven by plasmonic-enhanced fields. This characterization opens up new perspectives for HHG control with various experimental nano-setups.

Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Guangjin, E-mail: guangjin.ma@mpq.mpg.de; Max-Planck-Institut für Quantenoptik, D-85748 Garching; Dallari, William

2015-03-15

We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach.

Monolithic carrier-envelope phase-stabilization scheme.

PubMed

Fuji, Takao; Rauschenberger, Jens; Apolonski, Alexander; Yakovlev, Vladislav S; Tempea, Gabriel; Udem, Thomas; Gohle, Christoph; Hänsch, Theodor W; Lehnert, Walter; Scherer, Michael; Krausz, Ferenc

2005-02-01

A new scheme for stabilizing the carrier-envelope (CE) phase of a few-cycle laser pulse train is demonstrated. Self-phase modulation and difference-frequency generation in a single periodically poled lithium niobate crystal that transmits the main laser beam allows CE phase locking directly in the usable output. The monolithic scheme obviates the need for splitting off a fraction of the laser output for CE phase control, coupling into microstructured fiber, and separation and recombination of spectral components. As a consequence, the output yields 6-fs, 800-nm pulses with an unprecedented degree of short- and long-term reproducibility of the electric field waveform.

Efficient generation of ultra-intense few-cycle radially polarized laser pulses.

PubMed

Carbajo, Sergio; Granados, Eduardo; Schimpf, Damian; Sell, Alexander; Hong, Kyung-Han; Moses, Jeffrey; Kärtner, Franz X

2014-04-15

We report on efficient generation of millijoule-level, kilohertz-repetition-rate few-cycle laser pulses with radial polarization by combining a gas-filled hollow-waveguide compression technique with a suitable polarization mode converter. Peak power levels >85  GW are routinely achieved, capable of reaching relativistic intensities >10(19)  W/cm2 with carrier-envelope-phase control, by employing readily accessible ultrafast high-energy laser technology.

Communication: XFAIMS—eXternal Field Ab Initio Multiple Spawning for electron-nuclear dynamics triggered by short laser pulses

DOE PAGES

Mignolet, Benoit; Curchod, Basile F. E.; Martinez, Todd J.

2016-11-17

Attoscience is an emerging field where attosecond pulses or few cycle IR pulses are used to pump and probe the correlated electron-nuclear motion of molecules. We present the trajectory-guided eXternal Field Ab Initio Multiple Spawning (XFAIMS) method that models such experiments “on-the-fly,” from laser pulse excitation to fragmentation or nonadiabatic relaxation to the ground electronic state. For the photoexcitation of the LiH molecule, we show that XFAIMS gives results in close agreement with numerically exact quantum dynamics simulations, both for atto- and femtosecond laser pulses. As a result, we then show the ability of XFAIMS to model the dynamics inmore » polyatomic molecules by studying the effect of nuclear motion on the photoexcitation of a sulfine (H 2CSO).« less

High-flux soft x-ray harmonic generation from ionization-shaped few-cycle laser pulses

PubMed Central

Brahms, Christian; Gregory, Andrew; Tisch, John W. G.; Marangos, Jon P.

2018-01-01

Laser-driven high-harmonic generation provides the only demonstrated route to generating stable, tabletop attosecond x-ray pulses but has low flux compared to other x-ray technologies. We show that high-harmonic generation can produce higher photon energies and flux by using higher laser intensities than are typical, strongly ionizing the medium and creating plasma that reshapes the driving laser field. We obtain high harmonics capable of supporting attosecond pulses up to photon energies of 600 eV and a photon flux inside the water window (284 to 540 eV) 10 times higher than previous attosecond sources. We demonstrate that operating in this regime is key for attosecond pulse generation in the x-ray range and will become increasingly important as harmonic generation moves to fields that drive even longer wavelengths. PMID:29756033

The effect of dynamical Bloch oscillations on optical-field-induced current in a wide-gap dielectric

NASA Astrophysics Data System (ADS)

Földi, P.; Benedict, M. G.; Yakovlev, V. S.

2013-06-01

We consider the motion of charge carriers in a bulk wide-gap dielectric interacting with a few-cycle laser pulse. A semiclassical model based on Bloch equations is applied to describe the emerging time-dependent macroscopic currents for laser intensities close to the damage threshold. At such laser intensities, electrons can reach edges of the first Brillouin zone even for electron-phonon scattering rates as high as those known for SiO2. We find that, whenever this happens, Bragg-like reflections of electron waves, also known as Bloch oscillations, affect the dependence of the charge displaced by the laser pulse on its carrier-envelope phase.

Quasi-monoenergetic proton acceleration from cryogenic hydrogen microjet by ultrashort ultraintense laser pulses

NASA Astrophysics Data System (ADS)

Sharma, A.; Tibai, Z.; Hebling, J.; Fülöp, J. A.

2018-03-01

Laser-driven proton acceleration from a micron-sized cryogenic hydrogen microjet target is investigated using multi-dimensional particle-in-cell simulations. With few-cycle (20-fs) ultraintense (2-PW) laser pulses, high-energy quasi-monoenergetic proton acceleration is predicted in a new regime. A collisionless shock-wave acceleration mechanism influenced by Weibel instability results in a maximum proton energy as high as 160 MeV and a quasi-monoenergetic peak at 80 MeV for 1022 W/cm2 laser intensity with controlled prepulses. A self-generated strong quasi-static magnetic field is also observed in the plasma, which modifies the spatial distribution of the proton beam.

The interaction of excited atoms and few-cycle laser pulses

PubMed Central

Calvert, J. E.; Xu, Han; Palmer, A. J.; Glover, R. D.; Laban, D. E.; Tong, X. M.; Kheifets, A. S.; Bartschat, K.; Litvinyuk, I. V.; Kielpinski, D.; Sang, R. T.

2016-01-01

This work describes the first observations of the ionisation of neon in a metastable atomic state utilising a strong-field, few-cycle light pulse. We compare the observations to theoretical predictions based on the Ammosov-Delone-Krainov (ADK) theory and a solution to the time-dependent Schrödinger equation (TDSE). The TDSE provides better agreement with the experimental data than the ADK theory. We optically pump the target atomic species and measure the ionisation rate as the a function of different steady-state populations in the fine structure of the target state which shows significant ionisation rate dependence on populations of spin-polarised states. The physical mechanism for this effect is unknown. PMID:27666403

The interaction of excited atoms and few-cycle laser pulses.

PubMed

Calvert, J E; Xu, Han; Palmer, A J; Glover, R D; Laban, D E; Tong, X M; Kheifets, A S; Bartschat, K; Litvinyuk, I V; Kielpinski, D; Sang, R T

2016-09-26

This work describes the first observations of the ionisation of neon in a metastable atomic state utilising a strong-field, few-cycle light pulse. We compare the observations to theoretical predictions based on the Ammosov-Delone-Krainov (ADK) theory and a solution to the time-dependent Schrödinger equation (TDSE). The TDSE provides better agreement with the experimental data than the ADK theory. We optically pump the target atomic species and measure the ionisation rate as the a function of different steady-state populations in the fine structure of the target state which shows significant ionisation rate dependence on populations of spin-polarised states. The physical mechanism for this effect is unknown.

Carrier-envelope phase-dependent high harmonic generation in the water window using few-cycle infrared pulses.

PubMed

Ishii, Nobuhisa; Kaneshima, Keisuke; Kitano, Kenta; Kanai, Teruto; Watanabe, Shuntaro; Itatani, Jiro

2014-01-01

High harmonic generation (HHG) using waveform-controlled, few-cycle pulses from Ti:sapphire lasers has opened emerging researches in strong-field and attosecond physics. However, the maximum photon energy of attosecond pulses via HHG remains limited to the extreme ultraviolet region. Long-wavelength light sources with carrier-envelope phase stabilization are promising to extend the photon energy of attosecond pulses into the soft X-ray region. Here we demonstrate carrier-envelope phase-dependent HHG in the water window using sub-two-cycle optical pulses at 1,600 nm. Experimental and simulated results indicate the confinement of soft X-ray emission in a single recombination event with a bandwidth of 75 eV around the carbon K edge. Control of high harmonics by the waveform of few-cycle infrared pulses is a key milestone to generate soft X-ray attosecond pulses. We measure a dependence of half-cycle bursts on the gas pressure, which indicates subcycle deformation of the waveform of the infrared drive pulses in the HHG process.

Carrier-envelope phase-dependent high harmonic generation in the water window using few-cycle infrared pulses

PubMed Central

Ishii, Nobuhisa; Kaneshima, Keisuke; Kitano, Kenta; Kanai, Teruto; Watanabe, Shuntaro; Itatani, Jiro

2014-01-01

High harmonic generation (HHG) using waveform-controlled, few-cycle pulses from Ti:sapphire lasers has opened emerging researches in strong-field and attosecond physics. However, the maximum photon energy of attosecond pulses via HHG remains limited to the extreme ultraviolet region. Long-wavelength light sources with carrier-envelope phase stabilization are promising to extend the photon energy of attosecond pulses into the soft X-ray region. Here we demonstrate carrier-envelope phase-dependent HHG in the water window using sub-two-cycle optical pulses at 1,600 nm. Experimental and simulated results indicate the confinement of soft X-ray emission in a single recombination event with a bandwidth of 75 eV around the carbon K edge. Control of high harmonics by the waveform of few-cycle infrared pulses is a key milestone to generate soft X-ray attosecond pulses. We measure a dependence of half-cycle bursts on the gas pressure, which indicates subcycle deformation of the waveform of the infrared drive pulses in the HHG process. PMID:24535006

53 W average power few-cycle fiber laser system generating soft x rays up to the water window.

PubMed

Rothhardt, Jan; Hädrich, Steffen; Klenke, Arno; Demmler, Stefan; Hoffmann, Armin; Gotschall, Thomas; Eidam, Tino; Krebs, Manuel; Limpert, Jens; Tünnermann, Andreas

2014-09-01

We report on a few-cycle laser system delivering sub-8-fs pulses with 353 μJ pulse energy and 25 GW of peak power at up to 150 kHz repetition rate. The corresponding average output power is as high as 53 W, which represents the highest average power obtained from any few-cycle laser architecture so far. The combination of both high average and high peak power provides unique opportunities for applications. We demonstrate high harmonic generation up to the water window and record-high photon flux in the soft x-ray spectral region. This tabletop source of high-photon flux soft x rays will, for example, enable coherent diffractive imaging with sub-10-nm resolution in the near future.

Method to generate a pulse train of few-cycle coherent radiation

DOE PAGES

Garcia, Bryant; Hemsing, Erik; Raubenheimer, Tor; ...

2016-09-06

We develop a method to generate a long pulse train of few-cycle coherent radiation by modulating an electron beam with a high power laser. The large energy modulation disperses the beam in a radiating undulator and leads to the production of phase-locked few-cycle coherent radiation pulses. These pulses are produced at a high harmonic of the modulating laser, and are longitudinally separated by the modulating laser wavelength. Here, we discuss an analytical model for this scheme and investigate the temporal and spectral properties of this radiation. This model is compared with numerical simulation results using the unaveraged code Puffin. Wemore » examine various harmful effects and how they might be avoided, as well as a possible experimental realization of this scheme.« less

Laser-plasma accelerator-based single-cycle attosecond undulator source

NASA Astrophysics Data System (ADS)

Tibai, Z.; Tóth, Gy.; Nagyváradi, A.; Sharma, A.; Mechler, M. I.; Fülöp, J. A.; Almási, G.; Hebling, J.

2018-06-01

Laser-plasma accelerators (LPAs), producing high-quality electron beams, provide an opportunity to reduce the size of free-electron lasers (FELs) to only a few meters. A complete system is proposed here, which is based on FEL technology and consists of an LPA, two undulators, and other magnetic devices. The system is capable to generate carrier-envelope phase stable attosecond pulses with engineered waveform. Pulses with up to 60 nJ energy and 90-400 attosecond duration in the 30-120 nm wavelength range are predicted by numerical simulation. These pulses can be used to investigate ultrafast field-driven electron dynamics in matter.

Enhancing the intense field control of molecular fragmentation.

PubMed

Anis, Fatima; Esry, B D

2012-09-28

We describe a pump-probe scheme with which the spatial asymmetry of dissociating molecular fragments-as controlled by the carrier-envelope phase of an intense few-cycle laser pulse-can be enhanced by an order of magnitude or more. We illustrate the scheme using extensive, full-dimensional calculations for dissociation of H(2)(+) and include the averaging necessary for comparison with experiment.

Attosecond XUV absorption spectroscopy of doubly excited states in helium atoms dressed by a time-delayed femtosecond infrared laser

NASA Astrophysics Data System (ADS)

Yang, Z. Q.; Ye, D. F.; Ding, Thomas; Pfeifer, Thomas; Fu, L. B.

2015-01-01

In the present paper, we investigate the time-resolved transient absorption spectroscopy of doubly excited states of helium atoms by solving the time-dependent two-electron Schrödinger equation numerically based on a one-dimensional model. The helium atoms are subjected to an extreme ultraviolet (XUV) attosecond pulse and a time-delayed infrared (IR) few-cycle laser pulse. A superposition of doubly excited states populated by the XUV pulse is identified, which interferes with the direct ionization pathway leading to Fano resonance profiles in the photoabsorption spectrum. In the presence of an IR laser, however, the Fano line profiles are strongly modified: A shifting, splitting, and broadening of the original absorption lines is observed when the XUV attosecond pulse and infrared few-cycle laser pulse overlap in time, which is in good agreement with recent experimental results. At certain time delays, we observe symmetric Lorentz, inverted Fano profiles, and even negative absorption cross sections indicating that the XUV light can be amplified during the interaction with atoms. We further prove that the above pictures are general for different doubly excited states by suitably varying the frequency of the IR field to coherently couple the corresponding states.

Waveform-controlled terahertz radiation from the air filament produced by few-cycle laser pulses.

PubMed

Bai, Ya; Song, Liwei; Xu, Rongjie; Li, Chuang; Liu, Peng; Zeng, Zhinan; Zhang, Zongxin; Lu, Haihe; Li, Ruxin; Xu, Zhizhan

2012-06-22

Waveform-controlled terahertz (THz) radiation is of great importance due to its potential application in THz sensing and coherent control of quantum systems. We demonstrated a novel scheme to generate waveform-controlled THz radiation from air plasma produced when carrier-envelope-phase (CEP) stabilized few-cycle laser pulses undergo filamentation in ambient air. We launched CEP-stabilized 10 fs-long (~1.7 optical cycles) laser pulses at 1.8 μm into air and found that the generated THz waveform can be controlled by varying the filament length and the CEP of driving laser pulses. Calculations using the photocurrent model and including the propagation effects well reproduce the experimental results, and the origins of various phase shifts in the filament are elucidated.

Spatio-temporal characterisation of a 100 kHz 24 W sub-3-cycle NOPCPA laser system

NASA Astrophysics Data System (ADS)

Witting, Tobias; Furch, Federico J.; Vrakking, Marc J. J.

2018-04-01

In recent years, OPCPA and NOPCPA laser systems have shown the potential to supersede Ti:sapphire plus post-compression based laser systems to drive next generation attosecond light sources via direct amplification of few-cycle pulses to high pulse energies at high repetition rates. In this paper, we present a sub 3-cycle, 100 kHz, 24 W NOPA laser system and characterise its spatio-temporal properties using the SEA-F-SPIDER technique. Our results underline the importance of spatio-temporal diagnostics for these emerging laser systems.

Isotope Exchange in Oxide Catalyst

NASA Technical Reports Server (NTRS)

Hess, Robert V.; Miller, Irvin M.; Schryer, David R.; Sidney, Barry D.; Wood, George M., Jr.; Hoyt, Ronald F.; Upchurch, Billy T.; Brown, Kenneth G.

1987-01-01

Replacement technique maintains level of CO2/18 in closed-cycle CO2 lasers. High-energy, pulsed CO2 lasers using rare chemical isotopes must be operated in closed cycles to conserve gas. Rare isotopes operated in closed cycles to conserve gas. Rare isotopes as CO2/18 used for improved transmission of laser beam in atmosphere. To maintain laser power, CO2 must be regenerated, and O2 concentration kept below few tenths of percent. Conditions achieved by recombining CO and O2.

Generating coherent broadband continuum soft-x-ray radiation by attosecond ionization gating.

PubMed

Pfeifer, Thomas; Jullien, Aurélie; Abel, Mark J; Nagel, Phillip M; Gallmann, Lukas; Neumark, Daniel M; Leone, Stephen R

2007-12-10

The current paradigm of isolated attosecond pulse production requires a few-cycle pulse as the driver for high-harmonic generation that has a cosine-like electric field stabilized with respect to the peak of the pulse envelope. Here, we present simulations and experimental evidence that the production of high-harmonic light can be restricted to one or a few cycles on the leading edge of a laser pulse by a gating mechanism that employs time-dependent ionization of the conversion medium. This scheme enables the generation of broadband and tunable attosecond pulses. Instead of fixing the carrier-envelope phase to produce a cosine driver pulse, the phase becomes a control parameter for the center frequency of the attosecond pulse. A method to assess the multiplicity of attosecond pulses in the pulse train is also presented. The results of our study suggest an avenue towards relaxing the requirement of few-cycle pulses for isolated attosecond pulse generation.

Determination of the absolute carrier-envelope phase by angle-resolved photoelectron spectra of Ar by intense circularly polarized few-cycle pulses

NASA Astrophysics Data System (ADS)

Fukahori, Shinichi; Ando, Toshiaki; Miura, Shun; Kanya, Reika; Yamanouchi, Kaoru; Rathje, Tim; Paulus, Gerhard G.

2017-05-01

The angle-resolved photoelectron spectra of Ar are recorded using intense circularly polarized near-infrared few-cycle laser pulses, and the effect of the depletion of Ar atoms by the ionization and the effect of the Coulombic potential are examined by the classical trajectory Monte Carlo simulations. On the basis of the comparison between the experimental and theoretical photoelectron spectra, a procedure for estimating the absolute carrier-envelope phase (CEP) of the few-cycle laser pulses interacting with atoms and molecules is proposed. It is confirmed that the absolute CEP can securely be estimated without any numerical calculations once the angular distribution of the yield of photoelectrons having the kinetic energy larger than 30 eV is measured with the peak laser intensity in the range between 1 ×1014 and 5 ×1014W /c m2 .

Quantum entanglement in strong-field ionization

NASA Astrophysics Data System (ADS)

Majorosi, Szilárd; Benedict, Mihály G.; Czirják, Attila

2017-10-01

We investigate the time evolution of quantum entanglement between an electron, liberated by a strong few-cycle laser pulse, and its parent ion core. Since the standard procedure is numerically prohibitive in this case, we propose a method to quantify the quantum correlation in such a system: we use the reduced density matrices of the directional subspaces along the polarization of the laser pulse and along the transverse directions as building blocks for an approximate entanglement entropy. We present our results, based on accurate numerical simulations, in terms of several of these entropies, for selected values of the peak electric-field strength and the carrier-envelope phase difference of the laser pulse. The time evolution of the mutual entropy of the electron and the ion-core motion along the direction of the laser polarization is similar to our earlier results based on a simple one-dimensional model. However, taking into account also the dynamics perpendicular to the laser polarization reveals a surprisingly different entanglement dynamics above the laser intensity range corresponding to pure tunneling: the quantum entanglement decreases with time in the over-the-barrier ionization regime.

Frequency-chirp rates of harmonics driven by a few-cycle pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murakami, M.; Mauritsson, J.; Gaarde, M.B.

2005-08-15

We present numerical calculations of the time-frequency characteristics of cutoff harmonics generated by few-cycle laser pulses. We find that for driving pulses as short as three optical cycles, the adiabatic prediction for the harmonic chirp rate is very accurate. This negative chirp is so large that the resulting bandwidth causes substantial overlap between neighboring harmonics, and the harmonic phase therefore appears to not vary in time or frequency. By adding a compensating positive chirp to the driving pulse, which reduces the harmonic bandwidth and allows for the appearance of the negative chirp, we can measure the harmonic chirp rates. Wemore » also find that the positive chirp on the driving pulse causes the harmonics to shift down in frequency. We show that this counterintuitive result is caused by the change in the strong field continuum dynamics introduced by the variation of the driving frequency with time.« less

Spatial distribution on high-order-harmonic generation of an H2+ molecule in intense laser fields

NASA Astrophysics Data System (ADS)

Zhang, Jun; Ge, Xin-Lei; Wang, Tian; Xu, Tong-Tong; Guo, Jing; Liu, Xue-Shen

2015-07-01

High-order-harmonic generation (HHG) for the H2 + molecule in a 3-fs, 800-nm few-cycle Gaussian laser pulse combined with a static field is investigated by solving the one-dimensional electronic and one-dimensional nuclear time-dependent Schrödinger equation within the non-Born-Oppenheimer approximation. The spatial distribution in HHG is demonstrated and the results present the recombination process of the electron with the two nuclei, respectively. The spatial distribution of the HHG spectra shows that there is little possibility of the recombination of the electron with the nuclei around the origin z =0 a.u. and equilibrium internuclear positions z =±1.3 a.u. This characteristic is irrelevant to laser parameters and is only attributed to the molecular structure. Furthermore, we investigate the time-dependent electron-nuclear wave packet and ionization probability to further explain the underlying physical mechanism.

Nonlinear pulse compression stage delivering 43-W few-cycle pulses with GW peak-power at 2-μm wavelength

NASA Astrophysics Data System (ADS)

Gebhardt, Martin; Gaida, Christian; Heuermann, T.; Stutzki, F.; Jauregui, C.; Antonio-Lopez, J.; Schüuzgen, A.; Amezcua-Correa, R.; Tünnermann, A.; Limpert, J.

2018-02-01

In this contribution we demonstrate the nonlinear pulse compression of an ultrafast thulium-doped fiber laser down to 14 fs FWHM duration (sub-3 optical cycles) at a record average power of 43 W and 34.5 μJ pulse energy. To the best of our knowledge, we present the highest average power few-cycle laser source at 2 μm wavelength. This performance level in combination with GW-class peak power makes our laser source extremely interesting for driving high-harmonic generation or for generating mid-infrared frequency combs via intra-pulse frequency down-conversion at an unprecedented average power. The experiments were enabled by an ultrafast thulium-doped fiber laser delivering 110 fs pulses at high repetition rates, and an argon gas-filled antiresonant hollow-core fiber (ARHCF) with excellent transmission and weak anomalous dispersion, leading to the self-compression of the pulses. We have shown that ARHCFs are well-suited for nonlinear pulse compression around 2 μm wavelength and that this concept features excellent power handling capabilities. Based on this result, we discuss the next steps for energy and average power scaling including upscaling the fiber dimensions in order to fully exploit the capabilities of our laser system, which can deliver several GW of peak power. This way, a 100 W-class laser source with mJ-level few-cycle pulses at 2 μm wavelength is feasible in the near future.

Enhanced coherent Thomson scattering in the few-cycle regime.

PubMed

Hu, Ke; Wu, Hui-Chun

2016-10-01

We study x-ray production by coherent nonlinear Thomson scattering of few-cycle laser pulses from relativistic electron sheets. For an electron sheet thicker than the wavelength of the x-ray, the scattering efficiency is found to increase by two orders of magnitude for single-cycle laser pulses, as compared with longer pulses. This enhancement is attributed to the suppression of the destructive interference during the scattering process, as well as the frequency downshift related to the ultrabroad spectra of single-cycle pulses. The x-ray amplitude in this nonadiabatic regime is calculated and agrees with that from the particle-in-cell simulation. These results can be useful for designing more intense, shorter attosecond x-ray sources.

Electro-optic sampling of near-infrared waveforms

NASA Astrophysics Data System (ADS)

Keiber, Sabine; Sederberg, Shawn; Schwarz, Alexander; Trubetskov, Michael; Pervak, Volodymyr; Krausz, Ferenc; Karpowicz, Nicholas

2016-03-01

Access to the complete electric field evolution of a laser pulse is essential for attosecond science in general, and for the scrutiny and control of electron phenomena in solid-state physics specifically. Time-resolved field measurements are routine in the terahertz spectral range, using electro-optic sampling (EOS), photoconductive switches and field-induced second harmonic generation. EOS in particular features outstanding sensitivity and ease of use, making it the basis of time-resolved spectroscopic measurements for studying charge carrier dynamics and active optical devices. In this Letter, we show that careful optical filtering allows the bandwidth of this technique to be extended to wavelengths as short as 1.2 μm (230 THz) with half-cycle durations 2.3 times shorter than the sampling pulse. In a proof-of-principle application, we measure the influence of optical parametric amplification (OPA) on the electric field dynamics of a few-cycle near-infrared (NIR) pulse.

Carrier-envelope phase control of carrier-wave Rabi flopping in asymmetric semiparabolic quantum well.

PubMed

Zhang, Chaojin; Song, Xiaohong; Yang, Weifeng; Xu, Zhizhan

2008-02-04

We investigate the carrier-wave Rabi flopping effects in an asymmetric semiparabolic semiconductor quantum well (QW) with few-cycle pulse. It is found that higher spectral components of few-cycle ultrashort pulses in the semiparabolic QW depend crucially on the carrier-envelope phase (CEP) of the few-cycle ultrashort pulses: continuum and distinct peaks can be achieved by controlling the CEP. Our results demonstrate that by adjusting the CEP of few-cycle ultrashort pulses, the intersubband dynamics in the asymmetric semiparabolic QW can be controlled in an ultrashort timescale with moderate laser intensity.

On-target diagnosing of few-cycle pulses by high-order-harmonic generation

NASA Astrophysics Data System (ADS)

Brambila, Danilo S.; Husakou, Anton; Ivanov, Misha; Zhavoronkov, Nickolai

2017-12-01

We propose an approach to determine the residual phase distortion directly in the interaction region of few-cycle laser radiation with a gaseous target. We describe how the spectra of the generated high harmonics measured as a function of externally introduced dispersion into the driving few-cycle laser pulse can be used to decode small amounts of second- and third-order spectral phase, including the sign. The diagnosis is based on the analysis of several key features in the high-harmonic spectrum: the depth of spectral modulation, the position of the cutoff, and the symmetry of the spectrum with respect to the introduced dispersion. The approach is applicable to pulses without carrier-envelope phase (CEP) stabilization. Surprisingly, we find that for nearly-single-cycle pulses with nonstabilized CEP, deep spectral modulations in the harmonic spectra emerge for positively rather than negatively chirped pulses, in contrast to the case of CEP-stabilized pulses.

Attosecond-recollision-controlled selective fragmentation of polyatomic molecules.

PubMed

Xie, Xinhua; Doblhoff-Dier, Katharina; Roither, Stefan; Schöffler, Markus S; Kartashov, Daniil; Xu, Huailiang; Rathje, Tim; Paulus, Gerhard G; Baltuška, Andrius; Gräfe, Stefanie; Kitzler, Markus

2012-12-14

Control over various fragmentation reactions of a series of polyatomic molecules (acetylene, ethylene, 1,3-butadiene) by the optical waveform of intense few-cycle laser pulses is demonstrated experimentally. We show both experimentally and theoretically that the responsible mechanism is inelastic ionization from inner-valence molecular orbitals by recolliding electron wave packets, whose recollision energy in few-cycle ionizing laser pulses strongly depends on the optical waveform. Our work demonstrates an efficient and selective way of predetermining fragmentation and isomerization reactions in polyatomic molecules on subfemtosecond time scales.

Quantum simulation of ultrafast dynamics using trapped ultracold atoms.

PubMed

Senaratne, Ruwan; Rajagopal, Shankari V; Shimasaki, Toshihiko; Dotti, Peter E; Fujiwara, Kurt M; Singh, Kevin; Geiger, Zachary A; Weld, David M

2018-05-25

Ultrafast electronic dynamics are typically studied using pulsed lasers. Here we demonstrate a complementary experimental approach: quantum simulation of ultrafast dynamics using trapped ultracold atoms. Counter-intuitively, this technique emulates some of the fastest processes in atomic physics with some of the slowest, leading to a temporal magnification factor of up to 12 orders of magnitude. In these experiments, time-varying forces on neutral atoms in the ground state of a tunable optical trap emulate the electric fields of a pulsed laser acting on bound charged particles. We demonstrate the correspondence with ultrafast science by a sequence of experiments: nonlinear spectroscopy of a many-body bound state, control of the excitation spectrum by potential shaping, observation of sub-cycle unbinding dynamics during strong few-cycle pulses, and direct measurement of carrier-envelope phase dependence of the response to an ultrafast-equivalent pulse. These results establish cold-atom quantum simulation as a complementary tool for studying ultrafast dynamics.

High-power multi-megahertz source of waveform-stabilized few-cycle light

PubMed Central

Pronin, O.; Seidel, M.; Lücking, F.; Brons, J.; Fedulova, E.; Trubetskov, M.; Pervak, V.; Apolonski, A.; Udem, Th.; Krausz, F.

2015-01-01

Waveform-stabilized laser pulses have revolutionized the exploration of the electronic structure and dynamics of matter by serving as the technological basis for frequency-comb and attosecond spectroscopy. Their primary sources, mode-locked titanium-doped sapphire lasers and erbium/ytterbium-doped fibre lasers, deliver pulses with several nanojoules energy, which is insufficient for many important applications. Here we present the waveform-stabilized light source that is scalable to microjoule energy levels at the full (megahertz) repetition rate of the laser oscillator. A diode-pumped Kerr-lens-mode-locked Yb:YAG thin-disk laser combined with extracavity pulse compression yields waveform-stabilized few-cycle pulses (7.7 fs, 2.2 cycles) with a pulse energy of 0.15 μJ and an average power of 6 W. The demonstrated concept is scalable to pulse energies of several microjoules and near-gigawatt peak powers. The generation of attosecond pulses at the full repetition rate of the oscillator comes into reach. The presented system could serve as a primary source for frequency combs in the mid infrared and vacuum UV with unprecedented high power levels. PMID:25939968

Attosecond-controlled photoemission from metal nanowire tips in the few-electron regime

NASA Astrophysics Data System (ADS)

Ahn, B.; Schötz, J.; Kang, M.; Okell, W. A.; Mitra, S.; Förg, B.; Zherebtsov, S.; Süßmann, F.; Burger, C.; Kübel, M.; Liu, C.; Wirth, A.; Di Fabrizio, E.; Yanagisawa, H.; Kim, D.; Kim, B.; Kling, M. F.

2017-03-01

Metal nanotip photoemitters have proven to be versatile in fundamental nanoplasmonics research and applications, including, e.g., the generation of ultrafast electron pulses, the adiabatic focusing of plasmons, and as light-triggered electron sources for microscopy. Here, we report the generation of high energy photoelectrons (up to 160 eV) in photoemission from single-crystalline nanowire tips in few-cycle, 750-nm laser fields at peak intensities of (2-7.3) × 1012 W/cm2. Recording the carrier-envelope phase (CEP)-dependent photoemission from the nanowire tips allows us to identify rescattering contributions and also permits us to determine the high-energy cutoff of the electron spectra as a function of laser intensity. So far these types of experiments from metal nanotips have been limited to an emission regime with less than one electron per pulse. We detect up to 13 e/shot and given the limited detection efficiency, we expect up to a few ten times more electrons being emitted from the nanowire. Within the investigated intensity range, we find linear scaling of cutoff energies. The nonlinear scaling of electron count rates is consistent with tunneling photoemission occurring in the absence of significant charge interaction. The high electron energy gain is attributed to field-induced rescattering in the enhanced nanolocalized fields at the wires apex, where a strong CEP-modulation is indicative of the attosecond control of photoemission.

Free-beam soliton self-compression in air

NASA Astrophysics Data System (ADS)

Voronin, A. A.; Mitrofanov, A. V.; Sidorov-Biryukov, D. A.; Fedotov, A. B.; Pugžlys, A.; Panchenko, V. Ya; Shumakova, V.; Ališauskas, S.; Baltuška, A.; Zheltikov, A. M.

2018-02-01

We identify a physical scenario whereby soliton transients generated in freely propagating laser beams within the regions of anomalous dispersion in air can be compressed as a part of their free-beam spatiotemporal evolution to yield few-cycle mid- and long-wavelength-infrared field waveforms, whose peak power is substantially higher than the peak power of the input pulses. We show that this free-beam soliton self-compression scenario does not require ionization or laser-induced filamentation, enabling high-throughput self-compression of mid- and long-wavelength-infrared laser pulses within a broad range of peak powers from tens of gigawatts up to the terawatt level. We also demonstrate that this method of pulse compression can be extended to long-range propagation, providing self-compression of high-peak-power laser pulses in atmospheric air within propagation ranges as long as hundreds of meters, suggesting new ways towards longer-range standoff detection and remote sensing.

Direct longitudinal laser acceleration of electrons in free space

NASA Astrophysics Data System (ADS)

Carbajo, Sergio; Nanni, Emilio A.; Wong, Liang Jie; Moriena, Gustavo; Keathley, Phillip D.; Laurent, Guillaume; Miller, R. J. Dwayne; Kärtner, Franz X.

2016-02-01

Compact laser-driven accelerators are pursued heavily worldwide because they make novel methods and tools invented at national laboratories widely accessible in science, health, security, and technology [V. Malka et al., Principles and applications of compact laser-plasma accelerators, Nat. Phys. 4, 447 (2008)]. Current leading laser-based accelerator technologies [S. P. D. Mangles et al., Monoenergetic beams of relativistic electrons from intense laser-plasma interactions, Nature (London) 431, 535 (2004); T. Toncian et al., Ultrafast laser-driven microlens to focus and energy-select mega-electron volt protons, Science 312, 410 (2006); S. Tokita et al. Single-shot ultrafast electron diffraction with a laser-accelerated sub-MeV electron pulse, Appl. Phys. Lett. 95, 111911 (2009)] rely on a medium to assist the light to particle energy transfer. The medium imposes material limitations or may introduce inhomogeneous fields [J. R. Dwyer et al., Femtosecond electron diffraction: "Making the molecular movie,", Phil. Trans. R. Soc. A 364, 741 (2006)]. The advent of few cycle ultraintense radially polarized lasers [S. Carbajo et al., Efficient generation of ultraintense few-cycle radially polarized laser pulses, Opt. Lett. 39, 2487 (2014)] has ushered in a novel accelerator concept [L. J. Wong and F. X. Kärtner, Direct acceleration of an electron in infinite vacuum by a pulsed radially polarized laser beam, Opt. Express 18, 25035 (2010); F. Pierre-Louis et al. Direct-field electron acceleration with ultrafast radially polarized laser beams: Scaling laws and optimization, J. Phys. B 43, 025401 (2010); Y. I. Salamin, Electron acceleration from rest in vacuum by an axicon Gaussian laser beam, Phys. Rev. A 73, 043402 (2006); C. Varin and M. Piché, Relativistic attosecond electron pulses from a free-space laser-acceleration scheme, Phys. Rev. E 74, 045602 (2006); A. Sell and F. X. Kärtner, Attosecond electron bunches accelerated and compressed by radially polarized laser pulses and soft-x-ray pulses from optical undulators, J. Phys. B 47, 015601 (2014)] avoiding the need of a medium or guiding structure entirely to achieve strong longitudinal energy transfer. Here we present the first observation of direct longitudinal laser acceleration of nonrelativistic electrons that undergo highly directional multi-GeV /m accelerating gradients. This demonstration opens a new frontier for direct laser-driven particle acceleration capable of creating well collimated and relativistic attosecond electron bunches [C. Varin and M. Piché, Relativistic attosecond electron pulses from a free-space laser-acceleration scheme, Phys. Rev. E 74, 045602 (2006)] and x-ray pulses [A. Sell and F. X. Kärtner, Attosecond electron bunches accelerated and compressed by radially polarized laser pulses and soft-x-ray pulses from optical undulators, J. Phys. B 47, 015601 (2014)].

Carrier-envelope phase-dependent atomic coherence and quantum beats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu Ying; State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071; Yang Xiaoxue

2007-07-15

It is shown that the carrier-envelope phase (CEP) of few-cycle laser pulses has profound effects on the bound-state atomic coherence even in the weak-field regime where both tunneling and multiphoton ionization hardly take place. The atomic coherence thus produced is shown to be able to be mapped onto the CEP-dependent signal of quantum beats (and other quantum-interference phenomena) and hence might be used to extract information about and ultimately to measure the carrier-envelope phase.

Laser-Induced Linear-Field Particle Acceleration in Free Space.

PubMed

Wong, Liang Jie; Hong, Kyung-Han; Carbajo, Sergio; Fallahi, Arya; Piot, Philippe; Soljačić, Marin; Joannopoulos, John D; Kärtner, Franz X; Kaminer, Ido

2017-09-11

Linear-field particle acceleration in free space (which is distinct from geometries like the linac that requires components in the vicinity of the particle) has been studied for over 20 years, and its ability to eventually produce high-quality, high energy multi-particle bunches has remained a subject of great interest. Arguments can certainly be made that linear-field particle acceleration in free space is very doubtful given that first-order electron-photon interactions are forbidden in free space. Nevertheless, we chose to develop an accurate and truly predictive theoretical formalism to explore this remote possibility when intense, few-cycle electromagnetic pulses are used in a computational experiment. The formalism includes exact treatment of Maxwell's equations and exact treatment of the interaction among the multiple individual particles at near and far field. Several surprising results emerge. We find that electrons interacting with intense laser pulses in free space are capable of gaining substantial amounts of energy that scale linearly with the field amplitude. For example, 30 keV electrons (2.5% energy spread) are accelerated to 61 MeV (0.5% spread) and to 205 MeV (0.25% spread) using 250 mJ and 2.5 J lasers respectively. These findings carry important implications for our understanding of ultrafast electron-photon interactions in strong fields.

Simultaneous generation of sub-5-femtosecond 400  nm and 800  nm pulses for attosecond extreme ultraviolet pump-probe spectroscopy.

PubMed

Chang, Hung-Tzu; Zürch, Michael; Kraus, Peter M; Borja, Lauren J; Neumark, Daniel M; Leone, Stephen R

2016-11-15

Few-cycle laser pulses with wavelengths centered at 400 nm and 800 nm are simultaneously obtained through wavelength separation of ultrashort, spectrally broadened Vis-NIR laser pulses spanning 350-1100 nm wavelengths. The 400 nm and 800 nm pulses are separately compressed, yielding pulses with 4.4 fs and 3.8 fs duration, respectively. The pulse energy exceeds 5 μJ for the 400 nm pulses and 750 μJ for the 800 nm pulses. Intense 400 nm few-cycle pulses have a broad range of applications in nonlinear optical spectroscopy, which include the study of photochemical dynamics, semiconductors, and photovoltaic materials on few-femtosecond to attosecond time scales. The ultrashort 400 nm few-cycle pulses generated here not only extend the spectral range of the optical pulse for NIR-XUV attosecond pump-probe spectroscopy but also pave the way for two-color, three-pulse, multidimensional optical-XUV spectroscopy experiments.

Universal route to optimal few- to single-cycle pulse generation in hollow-core fiber compressors.

PubMed

Conejero Jarque, E; San Roman, J; Silva, F; Romero, R; Holgado, W; Gonzalez-Galicia, M A; Alonso, B; Sola, I J; Crespo, H

2018-02-02

Gas-filled hollow-core fiber (HCF) pulse post-compressors generating few- to single-cycle pulses are a key enabling tool for attosecond science and ultrafast spectroscopy. Achieving optimum performance in this regime can be extremely challenging due to the ultra-broad bandwidth of the pulses and the need of an adequate temporal diagnostic. These difficulties have hindered the full exploitation of HCF post-compressors, namely the generation of stable and high-quality near-Fourier-transform-limited pulses. Here we show that, independently of conditions such as the type of gas or the laser system used, there is a universal route to obtain the shortest stable output pulse down to the single-cycle regime. Numerical simulations and experimental measurements performed with the dispersion-scan technique reveal that, in quite general conditions, post-compressed pulses exhibit a residual third-order dispersion intrinsic to optimum nonlinear propagation within the fiber, in agreement with measurements independently performed in several laboratories around the world. The understanding of this effect and its adequate correction, e.g. using simple transparent optical media, enables achieving high-quality post-compressed pulses with only minor changes in existing setups. These optimized sources have impact in many fields of science and technology and should enable new and exciting applications in the few- to single-cycle pulse regime.

Rectifying the Optical-Field-Induced Current in Dielectrics: Petahertz Diode.

PubMed

Lee, J D; Yun, Won Seok; Park, Noejung

2016-02-05

Investigating a theoretical model of the optical-field-induced current in dielectrics driven by strong few-cycle laser pulses, we propose an asymmetric conducting of the current by forming a heterojunction made of two distinct dielectrics with a low hole mass (m_{h}^{*}≪m_{e}^{*}) and low electron mass (m_{e}^{*}≪m_{h}^{*}), respectively. This proposition introduces the novel concept of a petahertz (10^{15}  Hz) diode to rectify the current in the petahertz domain, which should be a key ingredient for the electric signal manipulation of future light-wave electronics. Further, we suggest the candidate dielectrics for the heterojunction.

Coherent control of ultrafast optical four-wave mixing with two-color {omega}-3{omega} laser pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serrat, Carles

2005-08-15

A theoretical investigation on the coherent control of optical transient four-wave mixing interactions in two-level systems with two intense few-cycle propagating laser pulses of central angular frequencies {omega} and 3{omega} is reported. By numerically solving the full Maxwell-Bloch equations beyond the slowly varying envelope and rotating-wave approximations in the time domain, the nonlinear coupling to the optical field at frequency 5{omega} is found to depend critically on the initial relative phase {phi} of the propagating pulses: the coupling is enhanced when the pulses interfere constructively in the center ({phi}=0), while it is nearly suppressed when they are out of phasemore » ({phi}={pi})« less

Ultrafast Modulation and Switching of Quantum-Well Lasers using Terahertz Fields

NASA Technical Reports Server (NTRS)

Ning, Cun-Zheng; Hughes, S.; Citrin, D.; Saini, Subhash (Technical Monitor)

1998-01-01

Modulation and switching of semiconductor lasers are important for laser-based information technology. Typically the speed of modulation and switching is limited by interband processes such as stimulated and spontaneous recombinations which occur on a nanosecond time scale. This is why the diode laser modulation has been restricted to tens of GHz. Modulation at higher speed is highly desirable as the information technology enters into the so-called tera-era. In this paper, we study the possibility of utilizing THz-field-induced plasma heating to modulate quantum-well lasers. This is a timely study since, with the advancement of THz solid-state sources and free-electron lasers, THz physics and related technology is currently coming out of its infancy. The investigation of interplaying THz and optical fields is also of intruiging fundamental interest. First, we introduce theoretical plasma heating results for the quantum-well optical amplifier in the presense of an intense half-cycle THz pulse. The heated carrier distributions are then utilized to calculate the THz-pulse-induced change in refractive index and gain profile. Since the electron-hole-plasma is heated using intraband transitions, we circumvent the usual complications due to an overall change in density, and the nonlinear recovery is governed solely by the carrier-LO-phonon interactions, typically 5 ps for a complete recovery. This procedure implies THz and sub-THz switching and recovery rates, respectively; using either gain modulation or index modulation. Plasma heating via steady-state THz fields is also studied. Finally, numerical simulation of a coupled set of equations to investigate the THz modulation based on a simplified model for quantum-well lasers is presented. Our results show that a semiconductor laser can be modulated at up to 1 THz with little distortion with a THz field amplitude at the order of a few kV/cm. Laser responses to a change in THz frequency will be shown. Constraints, practicalities, and applications will be discussed.

Isolated few-cycle radiation from chirped-pulse compression of a superradiant free-electron laser

DOE PAGES

Huang, Yen -Chieh; Zhang, Zhen; Chen, Chia -Hsiang; ...

2015-08-31

When a short electron bunch traverses an undulator to radiate a wavelength longer than the bunch length, intense superradiance from the electron bunch can quickly deplete the electron’s kinetic energy and lead to generation of an isolated chirped radiation pulse. Here, we develop a theory to describe this novel chirped pulse radiation in a superradiant free-electron laser and show the opportunity to generate isolated few-cycle high-power radiation through chirped-pulse compression after the undulator. The theory is completely characterized by how fast the electron energy is depleted for a given length of an undulator. We further present two design examples atmore » the THz and extreme-ultraviolet wavelengths and numerically generate isolated three- and nine-cycle radiation pulses, respectively.« less

Few-cycle pulse generation in an x-ray free-electron laser.

PubMed

Dunning, D J; McNeil, B W J; Thompson, N R

2013-03-08

A method is proposed to generate trains of few-cycle x-ray pulses from a free-electron laser (FEL) amplifier via a compact "afterburner" extension consisting of several few-period undulator sections separated by electron chicane delays. Simulations show that in the hard x ray (wavelength ~0.1 nm; photon energy ~10 keV) and with peak powers approaching normal FEL saturation (GW) levels, root mean square pulse durations of 700 zs may be obtained. This is approximately two orders of magnitude shorter than that possible for normal FEL amplifier operation. The spectrum is discretely multichromatic with a bandwidth envelope increased by approximately 2 orders of magnitude over unseeded FEL amplifier operation. Such a source would significantly enhance research opportunity in atomic dynamics and push capability toward nuclear dynamics.

Hybrid Er/Yb fibre laser system for generating few-cycle 1.6 to 2.0 {mu}m pulses optically synchronised with high-power pulses near 1 {mu}m

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrianov, A V; Anashkina, E A; Murav'ev, S V

2013-03-31

This paper presents the concept of fibre laser system design for generating optically synchronised femtosecond pulses at two, greatly differing wavelengths and reports experimental and numerical simulation studies of nonlinear conversion of femtosecond pulses at 1.5 {mu}m wavelength in a dispersion-shifted fibre, with the generation of synchronised pulses in the ranges 1.6 - 2 and 1 - 1.1 {mu}m. We describe a three-stage high-power fibre amplifier of femtosecond pulses at 1 {mu}m and a hybrid Er/Yb fibre laser system that has enabled the generation of 12 fs pulses with a centre wavelength of 1.7 {mu}m, synchronised with high-power (microjoule level)more » 250 fs pulses at 1.03 {mu}m. (extreme light fields and their applications)« less

Laser Cooling the Diatomic Molecule CaH

NASA Astrophysics Data System (ADS)

Velasquez, Joe, III; Di Rosa, Michael

2014-06-01

To laser-cool a species, a closed (or nearly closed) cycle is required to dissipate translational energy through many directed laser-photon absorption and subsequent randomly-directed spontaneous emission events. Many atoms lend themselves to such a closed-loop cooling cycle. Attaining laser-cooled molecular species is challenging because of their inherently complex internal structure, yet laser-cooling molecules could lead to studies in interesting chemical dynamics among other applications. Typically, laser-cooled atoms are assembled into molecules through photoassociation or Feschbach resonance. CaH is one of a few molecules whose internal structure is quite atom-like, allowing a nearly closed cycle without the need for many repumping lasers. We will also present our work-to-date on laser cooling this molecule. We employ traditional pulsed atomic/molecular beam techniques with a laser vaporization source to generate species with well-defined translational energies over a narrow range of velocity. In this way, we can apply laser-cooling to most species in the beam along a single dimension (the beam's axis). This project is funded by the LDRD program of the Los Alamos National Laboratory.

High duty cycle far-infrared germanium lasers

NASA Astrophysics Data System (ADS)

Chamberlin, Danielle Russell

The effects of crystal geometry, heat transport, and optics on high duty cycle germanium hole population inversion lasers are investigated. Currently the laser's low duty cycle limits its utility for many applications. This low duty cycle is a result of the combination of the large electrical input power necessary and insufficient heat extraction. In order to achieve a continuous-wave device, the input power must be decreased and the cooling power increased. In order to improve laser efficiency and lower the input power, the effect of laser crystal geometry on the electric field uniformity is considered. Geometries with d/L>>1 or <<1 are shown to have improved electric field uniformity, where d is the distance between electrical contacts and L is the length in the direction of the Hall electric field. A geometry with d/L>>1 is shown to decrease the threshold voltage for lasing. Laser crystals with the traditional contact geometry have been compared to a new, planar contact design with both electrical contacts on the same side of the laser crystal. This new geometry provides a large d/L ratio while also allowing effective heat sinking. A pure, single-crystal silicon heat sink is developed for planar contact design lasers, which improves the duty cycle tenfold. For the traditional contact design, copper heat sinks are developed that demonstrate cooling powers up to 10 Watts. The effects of thermal conductivity, surface area, and interfacial thermal resistance on the heat transport are compared. To improve the cavity quality, thereby allowing for smaller crystal volumes, new optical designs are investigated. A vertical cavity structure is demonstrated for the planar contact structure using strontium titanate single crystals as mirrors. A mode-selecting cavity is implemented for the traditional contact design. The spectra of small-volume, near-threshold lasers are measured. In contrast to the emission of larger lasers, these lasers emit within narrow frequency peaks that do not shift smoothly with magnetic field. The details of the emission are shown to strongly depend on the optical cavity. A record duty cycle of 5% is achieved using a laser of dimensions 0.80 x 3 x 11 mm3 with the traditional contact geometry, improved copper heat sinks, and carefully etched crystal surfaces.

Next Generation Driver for Attosecond and Laser-plasma Physics.

PubMed

Rivas, D E; Borot, A; Cardenas, D E; Marcus, G; Gu, X; Herrmann, D; Xu, J; Tan, J; Kormin, D; Ma, G; Dallari, W; Tsakiris, G D; Földes, I B; Chou, S-W; Weidman, M; Bergues, B; Wittmann, T; Schröder, H; Tzallas, P; Charalambidis, D; Razskazovskaya, O; Pervak, V; Krausz, F; Veisz, L

2017-07-12

The observation and manipulation of electron dynamics in matter call for attosecond light pulses, routinely available from high-order harmonic generation driven by few-femtosecond lasers. However, the energy limitation of these lasers supports only weak sources and correspondingly linear attosecond studies. Here we report on an optical parametric synthesizer designed for nonlinear attosecond optics and relativistic laser-plasma physics. This synthesizer uniquely combines ultra-relativistic focused intensities of about 10 20  W/cm 2 with a pulse duration of sub-two carrier-wave cycles. The coherent combination of two sequentially amplified and complementary spectral ranges yields sub-5-fs pulses with multi-TW peak power. The application of this source allows the generation of a broad spectral continuum at 100-eV photon energy in gases as well as high-order harmonics in relativistic plasmas. Unprecedented spatio-temporal confinement of light now permits the investigation of electric-field-driven electron phenomena in the relativistic regime and ultimately the rise of next-generation intense isolated attosecond sources.

Photonic Magnetic Field Sensor

NASA Astrophysics Data System (ADS)

Wyntjes, Geert

2002-02-01

Small, in-line polarization rotators or isolators to reduce feedback in fiber optic links can be the basis for excellent magnetic field sensors. Based on the giant magneto-optical (GMO) or Faraday effect in iron garnets, they with a magnetic field of a few hundred Gauss, (20 mT) for an interaction length for an optical beam of a few millimeters achieve a polarization rotation or phase shift of 45 deg (1/8 cycle). When powered by a small laser diode, with the induced linear phase shift recovered at the shot noise limit, we have demonstrated sensitivities at the 3.3 nT/Hz1/2 level for frequencies from less than 1 Hz to frequencies into the high kHz range. Through further improvements; an increase in interaction length, better materials and by far the greatest factor, the addition of a flux concentrator, sensitivities at the pT/Hz1/2 level appear to be within reach. We will detail such a design and discuss the issues that may limit achieving these goals.

Few-cycle pulse laser induced damage threshold determination of ultra-broadband optics.

PubMed

Kafka, Kyle R P; Talisa, Noah; Tempea, Gabriel; Austin, Drake R; Neacsu, Catalin; Chowdhury, Enam A

2016-12-12

A systematic study of few-cycle pulse laser induced damage threshold (LIDT) determination was performed for commercially-available ultra-broadband optics, (i.e. chirped mirrors, silver mirrors, beamsplitters, etc.) in vacuum and in air, for single and multi-pulse regime (S-on-1). Multi-pulse damage morphology at fluences below the single-pulse LIDT was studied in order to investigate the mechanisms leading to the onset of damage. Stark morphological contrast was observed between multi-pulse damage sites formed in air versus those in vacuum. One effect of vacuum testing compared to air included suppression of laser-induced periodic surface structures (LIPSS) formation, possibly influenced by a reduced presence of damage debris. Another effect of vacuum was occasional lowering of LIDT, which appears to be due to the stress-strain performance of the coating design during laser irradiation and under the external stress of vacuum ambience. A fused silica substrate is also examined, and a non-LIPSS nanostructuring is observed on the surface. Possible mechanisms are discussed.

Laser-Induced Linear-Field Particle Acceleration in Free Space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wong, Liang Jie; Hong, Kyung -Han; Carbajo, Sergio

Linear-field particle acceleration in free space (which is distinct from geometries like the linac that requires components in the vicinity of the particle) has been studied for over 20 years, and its ability to eventually produce high-quality, high energy multi-particle bunches has remained a subject of great interest. Arguments can certainly be made that linear-field particle acceleration in free space is very doubtful given that first-order electron-photon interactions are forbidden in free space. Nevertheless, we chose to develop an accurate and truly predictive theoretical formalism to explore this remote possibility when intense, few-cycle electromagnetic pulses are used in a computationalmore » experiment. The formalism includes exact treatment of Maxwell’s equations and exact treatment of the interaction among the multiple individual particles at near and far field. Several surprising results emerge. We find that electrons interacting with intense laser pulses in free space are capable of gaining substantial amounts of energy that scale linearly with the feld amplitude. For example, 30keV electrons (2.5% energy spread) are accelerated to 61MeV (0.5% spread) and to 205MeV (0.25% spread) using 250 mJ and 2.5J lasers respectively. Furthermore, these findings carry important implications for our understanding of ultrafast electron-photon interactions in strong fields.« less

Laser-Induced Linear-Field Particle Acceleration in Free Space

DOE PAGES

Wong, Liang Jie; Hong, Kyung -Han; Carbajo, Sergio; ...

2017-09-11

Linear-field particle acceleration in free space (which is distinct from geometries like the linac that requires components in the vicinity of the particle) has been studied for over 20 years, and its ability to eventually produce high-quality, high energy multi-particle bunches has remained a subject of great interest. Arguments can certainly be made that linear-field particle acceleration in free space is very doubtful given that first-order electron-photon interactions are forbidden in free space. Nevertheless, we chose to develop an accurate and truly predictive theoretical formalism to explore this remote possibility when intense, few-cycle electromagnetic pulses are used in a computationalmore » experiment. The formalism includes exact treatment of Maxwell’s equations and exact treatment of the interaction among the multiple individual particles at near and far field. Several surprising results emerge. We find that electrons interacting with intense laser pulses in free space are capable of gaining substantial amounts of energy that scale linearly with the feld amplitude. For example, 30keV electrons (2.5% energy spread) are accelerated to 61MeV (0.5% spread) and to 205MeV (0.25% spread) using 250 mJ and 2.5J lasers respectively. Furthermore, these findings carry important implications for our understanding of ultrafast electron-photon interactions in strong fields.« less

Terahertz emission from ultrafast ionizing air in symmetry-broken laser fields

NASA Astrophysics Data System (ADS)

Kim, Ki-Yong; Glownia, James H.; Taylor, Antoinette J.; Rodriguez, George

2007-04-01

A transient photocurrent model is developed to explain coherent terahertz emission from air irradiated by a symmetry-broken laser field composed of the fundamental and its second harmonic laser pulses. When the total laser field is asymmetric across individual optical cycles, a nonvanishing electron current surge can arise during optical field ionization of air, emitting a terahertz electromagnetic pulse. Terahertz power scalability is also investigated, and with optical pump energy of tens of millijoules per pulse, peak terahertz field strengths in excess of 150 kV/cm are routinely produced.

Terahertz emission from ultrafast ionizing air in symmetry-broken laser fields.

PubMed

Kim, Ki-Yong; Glownia, James H; Taylor, Antoinette J; Rodriguez, George

2007-04-16

A transient photocurrent model is developed to explain coherent terahertz emission from air irradiated by a symmetry-broken laser field composed of the fundamental and its second harmonic laser pulses. When the total laser field is asymmetric across individual optical cycles, a nonvanishing electron current surge can arise during optical field ionization of air, emitting a terahertz electromagnetic pulse. Terahertz power scalability is also investigated, and with optical pump energy of tens of millijoules per pulse, peak terahertz field strengths in excess of 150 kV/cm are routinely produced.

Dependence of the correlated-momentum patterns in double ionization on the carrier-envelope phase and intensity of a few-cycle laser pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xin, G. G.; Ye, D. F.; Graduate School, China Academy of Engineering Physics, Beijing 100088

2010-12-15

In the present paper, we investigate the correlated electron emission of atoms irradiated by a few-cycle laser pulse, with emphasis on the correlated longitudinal momentum spectra. We find that the spectra show clear v-shaped structures, in analogy to what was observed recently in long-pulse experiments. Moreover, the patterns of the spectra depend sensitively on the carrier-envelope phase as well as the laser intensity. The v-shaped structure is more pronounced at lower and higher intensities and becomes obscure at medium intensity. At a lower intensity, upon change of the phase from 0 to {pi}/2, the v-shaped structure shifts from the firstmore » quadrant to the third quadrant and the ratios between the double ionization yields in the first and third quadrants are found to increase by a few orders of magnitude. The semiclassical rescattering model is exploited in the preceding calculations and the underlying mechanisms are uncovered by analyzing the subcycle dynamics of classical trajectories.« less

Circularly polarized few-cycle optical rogue waves: rotating reduced Maxwell-Bloch equations.

PubMed

Xu, Shuwei; Porsezian, K; He, Jingsong; Cheng, Yi

2013-12-01

The rotating reduced Maxwell-Bloch (RMB) equations, which describe the propagation of few-cycle optical pulses in a transparent media with two isotropic polarized electronic field components, are derived from a system of complete Maxwell-Bloch equations without using the slowly varying envelope approximations. Two hierarchies of the obtained rational solutions, including rogue waves, which are also called few-cycle optical rogue waves, of the rotating RMB equations are constructed explicitly through degenerate Darboux transformation. In addition to the above, the dynamical evolution of the first-, second-, and third-order few-cycle optical rogue waves are constructed with different patterns. For an electric field E in the three lower-order rogue waves, we find that rogue waves correspond to localized large amplitude oscillations of the polarized electric fields. Further a complementary relationship of two electric field components of rogue waves is discussed in terms of analytical formulas as well as numerical figures.

Path length and spectrum of single-cycle mid-IR light bullets in transparent dielectrics

NASA Astrophysics Data System (ADS)

Chekalin, S. V.; Kompanets, V. O.; Dormidonov, A. E.; Kandidov, V. P.

2018-04-01

Filamentation of femtosecond laser radiation with a wavelength of 800 – 3900 nm and a power slightly exceeding the critical self-focusing power is studied using the spectral method and the method of laser coloration in LiF crystal. It is found that the length of a filament formed in the single-pulse regime increases with increasing excitation wavelength from a few tens of micrometres at 80 nm to hundreds of micrometres at 3900 nm. In the spectral region of anomalous group velocity dispersion, starting from 2600 nm, the initially smooth luminescence profile of the long-lived induced colour centres acquires a periodic structure, demonstrating the formation of a light bullet with a duration of about one cycle of the light field oscillation and a diameter smaller than 10 μm. The path length of such bullets does not exceed 0.5 mm in the single-pulse regime and 2.7 mm in the waveguide regime. A consequence of periodic modulation of the bullet light field in the process of propagation, observed experimentally and confirmed by calculations, is the appearance of sidebands near the excitation wavelength, as well as the appearance of visible spectral components in the supercontinuum radiation, whose angular divergence increases with increasing wavelength.

Measuring the absolute carrier-envelope phase of many-cycle laser fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tzallas, P.; Skantzakis, E.; Charalambidis, D.

2010-12-15

The carrier-envelope phase (CEP) of high-peak-power, many-cycle laser fields becomes a crucial parameter when such fields are used, in conjunction with polarization gating techniques, in isolated attosecond (asec) pulse generation. However, its measurement has not been achieved so far. We demonstrate a physical process sensitive to the CEP value of such fields and describe a method for its online shot-to-shot monitoring. This work paves the way for the exploitation of energetic isolated asec pulses in studies of nonlinear extreme ultraviolet (XUV) processes and XUV-pump-XUV-probe experiments with asec resolutions.

Bandwidth tunable THz wave generation in large-area periodically poled lithium niobate.

PubMed

Zhang, Caihong; Avetisyan, Yuri; Glosser, Andreas; Kawayama, Iwao; Murakami, Hironaru; Tonouchi, Masayoshi

2012-04-09

A new scheme of optical rectification (OR) of femtosecond laser pulses in a periodically poled lithium niobate (PPLN) crystal, which generates high energy and bandwidth tunable multicycle THz pulses, is proposed and demonstrated. We show that the number of the oscillation cycles of the THz electric field and therefore bandwidth of generated THz spectrum can easily and smoothly be tuned from a few tens of GHz to a few THz by changing the pump optical spot size on PPLN crystal. The minimal bandwidth is 17 GHz that is smallest ever of reported in scheme of THz generation by OR at room temperature. Similar to the case of Cherenkov-type OR in single-domain LiNbO₃, the spectrum of THz generation extends from 0.1 THz to 3 THz when laser beam is focused to a size close to half-period of PPLN structure. The energy spectral density of narrowband THz generation is almost independent of the bandwidth and is typically 220 nJ/THz for ~1 W pump power at 1 kHz repetition rate.

Optimal generation of spatially coherent soft X-ray isolated attosecond pulses in a gas-filled waveguide using two-color synthesized laser pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Cheng; Hong, Kyung -Han; Lin, C. D.

2016-12-08

Here, we numerically demonstrate the generation of intense, low-divergence soft X-ray isolated attosecond pulses in a gas-filled hollow waveguide using synthesized few-cycle two-color laser waveforms. The waveform is a superposition of a fundamental and its second harmonic optimized such that highest harmonic yields are emitted from each atom. We then optimize the gas pressure and the length and radius of the waveguide such that bright coherent high-order harmonics with angular divergence smaller than 1 mrad are generated, for photon energy from the extreme ultraviolet to soft X-rays. By selecting a proper spectral range enhanced isolated attosecond pulses are generated. Wemore » study how dynamic phase matching caused by the interplay among waveguide mode, neutral atomic dispersion, and plasma effect is achieved at the optimal macroscopic conditions, by performing time-frequency analysis and by analyzing the evolution of the driving laser’s electric field during the propagation. Our results, when combined with the on-going push of high-repetition-rate lasers (sub- to few MHz’s) may eventually lead to the generation of high-flux, low-divergence soft X-ray tabletop isolated attosecond pulses for applications.« less

Femtosecond time-domain observation of atmospheric absorption in the near-infrared spectrum

NASA Astrophysics Data System (ADS)

Hammond, T. J.; Monchocé, Sylvain; Zhang, Chunmei; Brown, Graham G.; Corkum, P. B.; Villeneuve, D. M.

2016-12-01

As light propagates through a medium, absorption caused by electronic or rovibrational transitions is evident in the transmitted spectrum. The incident electromagnetic field polarizes the medium and the absorption is due to the imaginary part of the linear susceptibility. In the time domain, the field establishes a coherence in the medium that radiates out of phase with the initial field. This coherence can persist for tens of picoseconds in atmospheric molecules such as H2O . We propagate a few-cycle laser pulse centered at 1.8 μ m through the atmosphere and measure the long-lasting molecular coherence in the time domain by high-order harmonic cross correlation. The measured optical free-induction decay of the pulse is compared with a calculation based on the calculated rovibrational spectrum of H2O absorption.

Origin of double-line structure in nonsequential double ionization by few-cycle laser pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Cheng, E-mail: huangcheng@swu.edu.cn; Zhong, Mingmin; Wu, Zhengmao

2016-07-28

We investigate nonsequential double ionization (NSDI) of molecules by few-cycle laser pulses at the laser intensity of 1.2–1.5 × 10{sup 14} W/cm{sup 2} using the classical ensemble model. The same double-line structure as the lower intensity (1.0 × 10{sup 14} W/cm{sup 2}) is also observed in the correlated electron momentum spectra for 1.2–1.4 × 10{sup 14} W/cm{sup 2}. However, in contrast to the lower intensity where NSDI proceeds only through the recollision-induced double excitation with subsequent ionization (RDESI) mechanism, here, the recollision-induced excitation with subsequent ionization (RESI) mechanism has a more significant contribution to NSDI. This indicates that RDESI ismore » not necessary for the formation of the double-line structure and RESI can give rise to the same type of structure independently. Furthermore, we explore the ultrafast dynamics underlying the formation of the double-line structure in RESI.« less

Laser Resurfacing: Full Field and Fractional.

PubMed

Pozner, Jason N; DiBernardo, Barry E

2016-07-01

Laser resurfacing is a very popular procedure worldwide. Full field and fractional lasers are used in many aesthetic practices. There have been significant advances in laser resurfacing in the past few years, which make patient treatments more efficacious and with less downtime. Erbium and carbon dioxide and ablative, nonablative, and hybrid fractional lasers are all extremely effective and popular tools that have a place in plastic surgery and dermatology offices. Copyright © 2016 Elsevier Inc. All rights reserved.

Electron Dynamics in Nanostructures in Strong Laser Fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kling, Matthias

2014-09-11

The goal of our research was to gain deeper insight into the collective electron dynamics in nanosystems in strong, ultrashort laser fields. The laser field strengths will be strong enough to extract and accelerate electrons from the nanoparticles and to transiently modify the materials electronic properties. We aimed to observe, with sub-cycle resolution reaching the attosecond time domain, how collective electronic excitations in nanoparticles are formed, how the strong field influences the optical and electrical properties of the nanomaterial, and how the excitations in the presence of strong fields decay.

Few-cycle carrier envelope phase-dependent stereo detection of electrons.

PubMed

Verhoef, Aart J; Fernández, Alma; Lezius, Matthias; O'Keeffe, Kevin; Uiberacker, Matthias; Krausz, Ferenc

2006-12-01

The spatial distribution of electrons emitted from atoms by few-cycle optical fields is known to be dependent on the carrier envelope phase, i.e., the phase of the field with respect to the pulse envelope. With respect to Paulus et al. [Phys. Rev. Lett.91, 253004 (2003)] we propose a greatly simplified device to measure and control the carrier envelope phase of few-cycle pulses with an accuracy of better than pi/10 based on this principle. We compared different schemes to control the carrier envelope phase of our pulses.

A Maxwell-Schrödinger solver for quantum optical few-level systems

NASA Astrophysics Data System (ADS)

Fleischhaker, Robert; Evers, Jörg

2011-03-01

The msprop program presented in this work is capable of solving the Maxwell-Schrödinger equations for one or several laser fields propagating through a medium of quantum optical few-level systems in one spatial dimension and in time. In particular, it allows to numerically treat systems in which a laser field interacts with the medium with both its electric and magnetic component at the same time. The internal dynamics of the few-level system is modeled by a quantum optical master equation which includes coherent processes due to optical transitions driven by the laser fields as well as incoherent processes due to decay and dephasing. The propagation dynamics of the laser fields is treated in slowly varying envelope approximation resulting in a first order wave equation for each laser field envelope function. The program employs an Adams predictor formula second order in time to integrate the quantum optical master equation and a Lax-Wendroff scheme second order in space and time to evolve the wave equations for the fields. The source function in the Lax-Wendroff scheme is specifically adapted to allow taking into account the simultaneous coupling of a laser field to the polarization and the magnetization of the medium. To reduce execution time, a customized data structure is implemented and explained. In three examples the features of the program are demonstrated and the treatment of a system with a phase-dependent cross coupling of the electric and magnetic field component of a laser field is shown. Program summaryProgram title: msprop Catalogue identifier: AEHR_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHR_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 507 625 No. of bytes in distributed program, including test data, etc.: 10 698 552 Distribution format: tar.gz Programming language: C (C99 standard), Mathematica, bash script, gnuplot script Computer: Tested on x86 architecture Operating system: Unix/Linux environment RAM: Less than 30 MB Classification: 2.5 External routines: Standard C math library, accompanying bash script uses gnuplot, bc (basic calculator), and convert (ImageMagick) Nature of problem: We consider a system of quantum optical few-level atoms exposed to several near-resonant continuous-wave or pulsed laser fields. The complexity of the problem arises from the combination of the coherent and incoherent time evolution of the atoms and its dependence on the spatially varying fields. In systems with a coupling to the electric and magnetic field component the simultaneous treatment of both field components poses an additional challenge. Studying the system dynamics requires solving the quantum optical master equation coupled to the wave equations governing the spatio-temporal dynamics of the fields [1,2]. Solution method: We numerically integrate the equations of motion using a second order Adams predictor method for the time evolution of the atomic density matrix and a second order Lax-Wendroff scheme for iterating the fields in space [3]. For the Lax-Wendroff scheme, the source function is adapted such that a simultaneous coupling to the polarization and the magnetization of the medium can be taken into account. Restrictions: The evolution of the fields is treated in slowly varying envelope approximation [2] such that variations of the fields in space and time must be on a scale larger than the wavelength and the optical cycle. Propagation is restricted to the forward direction and to one dimension. Concerning the description of the atomic system, only a finite number of basis states can be treated and the laser-driven transitions have to be near-resonant such that the rotating-wave approximation can be applied [2]. Unusual features: The program allows the dipole interaction of both the electric and the magnetic component of a laser field to be taken into account at the same time. Thus, a system with a phase-dependent cross coupling of electric and magnetic field component can be treated (see Section 4.2 and [4]). Concerning the implementation of the data structure, it has been optimized for faster memory access. Compared to using standard memory allocation methods, shorter run times are achieved (see Section 3.2). Additional comments: Three examples are given. They each include a readme file, a Mathematica notebook to generate the C-code form of the quantum optical master equation, a parameter file, a bash script which runs the program and converts the numerical data into a movie, two gnuplot scripts, and all files that are produced by running the bash script. Running time: For the first two examples the running time is less than a minute, the third example takes about 12 minutes. On a Pentium 4 (3 GHz) system, a rough estimate can be made with a value of 1 second per million grid points and per field variable.

Visualizing and Steering Dissociative Frustrated Double Ionization of Hydrogen Molecules

NASA Astrophysics Data System (ADS)

Zhang, Wenbin; Yu, Zuqing; Gong, Xiaochun; Wang, Junping; Lu, Peifen; Li, Hui; Song, Qiying; Ji, Qinying; Lin, Kang; Ma, Junyang; Li, Hanxiao; Sun, Fenghao; Qiang, Junjie; Zeng, Heping; He, Feng; Wu, Jian

2017-12-01

We experimentally visualize the dissociative frustrated double ionization of hydrogen molecules by using few-cycle laser pulses in a pump-probe scheme, in which process the tunneling ionized electron is recaptured by one of the outgoing nuclei of the breaking molecule. Three internuclear distances are recognized to enhance the dissociative frustrated double ionization of molecules at different instants after the first ionization step. The recapture of the electron can be further steered to one of the outgoing nuclei as desired by using phase-controlled two-color laser pulses. Both the experimental measurements and numerical simulations suggest that the Rydberg atom is favored to emit to the direction of the maximum of the asymmetric optical field. Our results on the one hand intuitively visualize the dissociative frustrated double ionization of molecules, and on the other hand open the possibility to selectively excite the heavy fragment ejected from a molecule.

Isolated attosecond pulses in the water window

NASA Astrophysics Data System (ADS)

Chang, Zenghu

Millijoule level, few-cycle, carrier-envelope phase (CEP) stable Ti:Sapphire lasers have been the workhorse for the first generation attosecond light sources in the last decade. The spectral range of isolated attosecond pulses with sufficient photon flux for time-resolved pump-probe experiments has been limited to extreme ultraviolet (10 to 150 eV). The shortest pulses achieved are 67 as. The center wavelength of Ti:Sapphire lasers is 800 nm. It was demonstrated in 2001 that the cutoff photon energy of the high harmonic spectrum can be extended by increasing the center wavelength of the driving lasers. In recent years, mJ level, two-cycle, carrier-envelope phase stabilized lasers at 1.6 to 2.1 micron have been developed by compressing pulses from Optical Parametric Amplifiers with gas-filled hollow-core fibers or by implementing Optical Parametric Chirped Pulse Amplification (OPCPA) techniques. Recently, when long wavelength driving was combined with polarization gating, isolated soft x-rays in the water window (280-530 eV) were generated in our laboratory. The number of x-ray photons in the 120-400 eV range is comparable to that generated with Ti:Sapphire lasers in the 50 to 150 eV range. The yield of harmonic generation depends strongly on the ellipticity of the driving fields, which is the foundation of polarization gating. When the width of the gate was set to less than one half of the laser cycle, a soft x-ray supercontinuum was generated. The intensity of the gated x-ray spectrum is sensitive to the carrier-envelope phase of the driving laser, which indicates that single isolated attosecond pulses were generated. The ultrabroadband isolated x-ray pulses with 53 as duration were characterized by attosecond streaking measurements. This work has been supported by the DARPA PULSE program (W31P4Q1310017); the Army Research Office (W911NF-14-1-0383, W911NF-15-1- 0336); the Air Force Office of Scientific Research (FA9550-15-1-0037, FA9550-16-1-0149), and NSF 1506345.

Transient Absorption of Attosecond Pulses by He Atoms in Presence of Near-Infrared Laser Fields: A TDDFT Analysis of Sub-Cycle Temporal Structures

NASA Astrophysics Data System (ADS)

Heslar, John; Telnov, Dmitry; Chu, Shih-I.

2013-05-01

We study transient absorption of extreme ultraviolet (XUV) attosecond pulses in presence of near-infrared (NIR) laser fields by analyzing the population and photon emission of excited atomic energy levels. We consider He atoms and apply a self-interaction-free fully ab initio time-dependent density functional theory (TDDFT). Our method is based on the Krieger-Li-Iafrate (KLI) treatment of the optimized effective potential and incorporates explicitly the self-interaction correction. We focus on the sub-cycle (with respect to NIR field) temporal behavior of the population of the excited energy levels and related dynamics of photon emission. We observe and identify sub-cycle shifts in the photon emission spectrum as a function of the time delay between the XUV and NIR pulses. In the region where the two pulses overlap, the photon emission peaks have an oscillatory structure with a period of 1.3 fs, which is half of the NIR laser optical cycle. Such a structure was also observed in recent experiments on transient absorption. This work was partially supported by DOE and by MOE-NSC-NTU-Taiwan.

Effects of laser-polarization and wiggler magnetic fields on electron acceleration in laser-cluster interaction

NASA Astrophysics Data System (ADS)

Singh Ghotra, Harjit; Kant, Niti

2018-06-01

We examine the electron dynamics during laser-cluster interaction. In addition to the electrostatic field of an individual cluster and laser field, we consider an external transverse wiggler magnetic field, which plays a pivotal role in enhancing the electron acceleration. Single-particle simulation has been presented with a short pulse linearly polarized as well as circularly polarized laser pulses for electron acceleration in a cluster. The persisting Coulomb field allows the electron to absorb energy from the laser field. The stochastically heated electron finds a weak electric field at the edge of the cluster from where it is ejected. The wiggler magnetic field connects the regions of the stochastically heated, ejected electron from the cluster and high energy gain by the electron from the laser field outside the cluster. This increases the field strength and hence supports the electron to meet the phase of the laser field for enhanced acceleration. A long duration resonance appears with an optimized magnetic wiggler field of about 3.4 kG. Hence, the relativistic energy gain by the electron is enhanced up to a few 100 MeV with an intense short pulse laser with an intensity of about 1019 W cm‑2 in the presence of a wiggler magnetic field.

Isolated-attosecond-pulse generation from asymmetric molecules with an {omega}+2{omega}/3 multicycle two-color field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Qianguang; Department of Physics, Xiaogan University, Xiaogan 432000; Hong Weiyi

2010-05-15

The high harmonic generation from asymmetric molecules with an {omega}+2{omega}/3 multicycle bichromatic laser pulse has been investigated. It is shown that the ionization asymmetry in consecutive half optical cycles for asymmetric molecules is further enhanced since the 2{omega}/3 control laser pulse further enhances the amplitude of the ionization peak at the center of the laser pulse. The 2{omega}/3 control laser pulse also significantly enlarges the difference of the photon energies emitted from the ejected electron in the half optical cycle at the central laser pulse and its next half optical cycle. In addition, a broadband supercontinuum is produced in themore » plateau of the spectrum, from which an isolated 90-as pulse can be directly obtained.« less

Laser waveform control of extreme ultraviolet high harmonics from solids.

PubMed

You, Yong Sing; Wu, Mengxi; Yin, Yanchun; Chew, Andrew; Ren, Xiaoming; Gholam-Mirzaei, Shima; Browne, Dana A; Chini, Michael; Chang, Zenghu; Schafer, Kenneth J; Gaarde, Mette B; Ghimire, Shambhu

2017-05-01

Solid-state high-harmonic sources offer the possibility of compact, high-repetition-rate attosecond light emitters. However, the time structure of high harmonics must be characterized at the sub-cycle level. We use strong two-cycle laser pulses to directly control the time-dependent nonlinear current in single-crystal MgO, leading to the generation of extreme ultraviolet harmonics. We find that harmonics are delayed with respect to each other, yielding an atto-chirp, the value of which depends on the laser field strength. Our results provide the foundation for attosecond pulse metrology based on solid-state harmonics and a new approach to studying sub-cycle dynamics in solids.

Laser chirp effect on femtosecond laser filamentation generated for pulse compression.

PubMed

Park, Juyun; Lee, Jae-Hwan; Nam, Chang H

2008-03-31

The influence of laser chirp on the formation of femtosecond laser filamentation in Ar was investigated for the generation of few-cycle high-power laser pulses. The condition for the formation of a single filament has been carefully examined using 28-fs laser pulses with energy over 3 mJ. The filament formation and output spectrum changed very sensitively to the initial laser chirp and gas pressure. Much larger spectral broadening was obtained with positively chirped pulses, compared to the case of negatively chirped pulses that generated much longer filament, and compressed pulses of 5.5 fs with energy of 0.5 mJ were obtained from the filamentation of positively chirped 30-fs laser pulses in a single Ar cell.

Influence of external magnetic field on laser-induced gold nanoparticles fragmentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serkov, A. A.; The Federal State Educational Institution of Higher Professional Education, “Moscow Institute of Physics and Technology; Rakov, I. I.

Laser-assisted fragmentation is an efficient method of the nanoparticles size and morphology control. However, its exact mechanisms are still under consideration. One of the remaining problems is the plasma formation, inevitably occurring upon the high intensity laser irradiation. In this Letter, the role of the laser-induced plasma is studied via introduction of high-intensity external magnetic field (up to 7.5 T). Its presence is found to cause the plasma emission to start earlier regarding to a laser pulse, also increasing the plume luminosity. Under these conditions, the acceleration of nanoparticles fragmentation down to a few nanometers is observed. Laser-induced plasma interaction withmore » magnetic field and consequent energy transfer from plasma to nanoparticles are discussed.« less

Relativistic Acceleration of Electrons Injected by a Plasma Mirror into a Radially Polarized Laser Beam.

PubMed

Zaïm, N; Thévenet, M; Lifschitz, A; Faure, J

2017-09-01

We propose a method to generate femtosecond, relativistic, and high-charge electron bunches using few-cycle and tightly focused radially polarized laser pulses. In this scheme, the incident laser pulse reflects off an overdense plasma that injects electrons into the reflected pulse. Particle-in-cell simulations show that the plasma injects electrons ideally, resulting in a dramatic increase of charge and energy of the accelerated electron bunch in comparison to previous methods. This method can be used to generate femtosecond pC bunches with energies in the 1-10 MeV range using realistic laser parameters corresponding to current kHz laser systems.

Laser-induced extreme magnetic field in nanorod targets

NASA Astrophysics Data System (ADS)

Lécz, Zsolt; Andreev, Alexander

2018-03-01

The application of nano-structured target surfaces in laser-solid interaction has attracted significant attention in the last few years. Their ability to absorb significantly more laser energy promises a possible route for advancing the currently established laser ion acceleration concepts. However, it is crucial to have a better understanding of field evolution and electron dynamics during laser-matter interactions before the employment of such exotic targets. This paper focuses on the magnetic field generation in nano-forest targets consisting of parallel nanorods grown on plane surfaces. A general scaling law for the self-generated quasi-static magnetic field amplitude is given and it is shown that amplitudes up to 1 MT field are achievable with current technology. Analytical results are supported by three-dimensional particle-in-cell simulations. Non-parallel arrangements of nanorods has also been considered which result in the generation of donut-shaped azimuthal magnetic fields in a larger volume.

Attosecond control of electrons emitted from a nanoscale metal tip.

PubMed

Krüger, Michael; Schenk, Markus; Hommelhoff, Peter

2011-07-06

Attosecond science is based on steering electrons with the electric field of well controlled femtosecond laser pulses. It has led to the generation of extreme-ultraviolet pulses with a duration of less than 100 attoseconds (ref. 3; 1 as = 10(-18) s), to the measurement of intramolecular dynamics (by diffraction of an electron taken from the molecule under scrutiny) and to ultrafast electron holography. All these effects have been observed with atoms or molecules in the gas phase. Electrons liberated from solids by few-cycle laser pulses are also predicted to show a strong light-phase sensitivity, but only very small effects have been observed. Here we report that the spectra of electrons undergoing photoemission from a nanometre-scale tungsten tip show a dependence on the carrier-envelope phase of the laser, with a current modulation of up to 100 per cent. Depending on the carrier-envelope phase, electrons are emitted either from a single sub-500-attosecond interval of the 6-femtosecond laser pulse, or from two such intervals; the latter case leads to spectral interference. We also show that coherent elastic re-scattering of liberated electrons takes place at the metal surface. Owing to field enhancement at the tip, a simple laser oscillator reaches the peak electric field strengths required for attosecond experiments at 100-megahertz repetition rates, rendering complex amplified laser systems dispensable. Practically, this work represents a simple, extremely sensitive carrier-envelope phase sensor, which could be shrunk in volume to about one cubic centimetre. Our results indicate that the attosecond techniques developed with (and for) atoms and molecules can also be used with solids. In particular, we foresee subfemtosecond, subnanometre probing of collective electron dynamics (such as plasmon polaritons) in solid-state systems ranging in scale from mesoscopic solids to clusters and to single protruding atoms. ©2011 Macmillan Publishers Limited. All rights reserved

Modeling Gravitational Radiation Waveforms from Black Hole Mergers

NASA Technical Reports Server (NTRS)

Baker, J. G.; Centrelia, J. M.; Choi, D.; Koppitz, M.; VanMeter, J.

2006-01-01

Gravitational radiation from merging binary black hole systems is anticipated as a key source for gravitational wave observations. Ground-based instruments, such as the Laser Interferometer Gravitational-wave Observatory (LIGO) may observe mergers of stellar-scale black holes, while the space-based Laser Interferometer Space Antenna (LISA) observatory will be sensitive to mergers of massive galactic-center black holes over a broad range of mass scales. These cataclysmic events may emit an enormous amount of energy in a brief time. Gravitational waves from comparable mass mergers carry away a few percent of the system's mass-energy in just a few wave cycles, with peak gravitational wave luminosities on the order of 10^23 L_Sun. Optimal analysis and interpretation of merger observation data will depend on developing a detailed understanding, based on general relativistic modeling, of the radiation waveforms. We discuss recent progress in modeling radiation from equal mass mergers using numerical simulations of Einstein's gravitational field equations, known as numerical relativity. Our simulations utilize Adaptive Mesh Refinement (AMR) to allow high-resolution near the black holes while simultaneously keeping the outer boundary of the computational domain far from the black holes, and making it possible to read out gravitational radiation waveforms in the weak-field wave zone. We discuss the results from simulations beginning with the black holes orbiting near the system's innermost stable orbit, comparing the recent simulations with earlier "Lazarus" waveform estimates based on an approximate hybrid numerical/perturbative technique.

Few-cycle attosecond pulse chirp effects on asymmetries in ionized electron momentum distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng Liangyou; Tan Fang; Gong Qihuang

2009-07-15

The momentum distributions of electrons ionized from H atoms by chirped few-cycle attosecond pulses are investigated by numerically solving the time-dependent Schroedinger equation. The central carrier frequency of the pulse is chosen to be 25 eV, which is well above the ionization threshold. The asymmetry (or difference) in the yield of electrons ionized along and opposite to the direction of linear laser polarization is found to be very sensitive to the pulse chirp (for pulses with fixed carrier-envelope phase), both for a fixed electron energy and for the energy-integrated yield. In particular, the larger the pulse chirp, the larger themore » number of times the asymmetry changes sign as a function of ionized electron energy. For a fixed chirp, the ionized electron asymmetry is found to be sensitive also to the carrier-envelope phase of the few-cycle pulse.« less

Non-iterative characterization of few-cycle laser pulses using flat-top gates.

PubMed

Selm, Romedi; Krauss, Günther; Leitenstorfer, Alfred; Zumbusch, Andreas

2012-03-12

We demonstrate a method for broadband laser pulse characterization based on a spectrally resolved cross-correlation with a narrowband flat-top gate pulse. Excellent phase-matching by collinear excitation in a microscope focus is exploited by degenerate four-wave mixing in a microscope slide. Direct group delay extraction of an octave spanning spectrum which is generated in a highly nonlinear fiber allows for spectral phase retrieval. The validity of the technique is supported by the comparison with an independent second-harmonic fringe-resolved autocorrelation measurement for an 11 fs laser pulse.

The impact of the carrier envelope phase-dependence on system and laser parameters

NASA Astrophysics Data System (ADS)

Reinhard, P.-G.; Suraud, E.; Meier, C.

2018-01-01

We investigate, from a theoretical perspective, photoemission of electrons induced by ultra-short infrared pulses covering only a few photon cycles. In particular, we investigate the impact of the carrier envelope phase of the laser pulse which plays an increasingly large role for decreasing pulse length. As key observable we look at the asymmetry of the angular distribution as function of kinetic energy of the emitted electrons. The focus of the present study lies on the system dependence of the reaction. To this end, we study two very different systems in comparison, an Ar atom and the Na{}9+ cluster. The study employs a fully quantum-mechanical description of electron dynamics at the level of time-dependent density functional theory. We find a sensitive dependence on the system which can be related to the different spectral response properties. Results can be understood from an interplay of the ponderomotive motion driven by the external photon field and dynamical polarization of the system.

Three dimensional α-tunneling in intense laser fields

NASA Astrophysics Data System (ADS)

Kis, Daniel P.; Szilvasi, Reka

2018-04-01

The width and life-time of the quasibound state of the α cluster in intense monochromatic electromagnetic (laser) field are discussed in details. The laser modified three dimensional potential barrier felt by the α particle is investigated analytically in long wave approximation and zero-order approximations with some different nuclear models: Coulomb potential with rectangular well, and with Woods-Saxon type potential. We show that the circularly polarized electromagnetic field and the special parameters of the nuclear potentials determine an enhancement of the decay probability, so the life-time of the quasibound state decreases in few times compared to the case of free field.

High-energy vacuum birefringence and dichroism in an ultrastrong laser field

NASA Astrophysics Data System (ADS)

Meuren, Sebastian; Bragin, Sergey; Keitel, Christoph H.; di Piazza, Antonino

2017-10-01

The interaction between real photons in vacuum is a long-standing prediction of quantum electrodynamics, which has never been observed experimentally. Upcoming 10 PW laser systems like the Extreme Light Infrastructure (ELI) will provide laser pulses with unprecedented intensities. If combined with highly energetic gamma photons - obtainable via Compton backscattering from laser-wakefield accelerated electron beams - the QED critical field becomes accessible. In we have derived how a generally polarized probe photon beam is influenced by both vacuum birefringence and dichroism in a strong linearly polarized plane-wave laser field. We put forward an experimental scheme to measure these effects in the nontrivial high-energy regime, where the QED critical field is reached and the Euler-Heisenberg approximation, valid for low-frequency electromagnetic fields, breaks down. Our results suggest the feasibility of verifying/rejecting the QED prediction for vacuum birefringence/dichroism at the 3 σ confidence level on the time scale of a few days at several upcoming laser facilities. Now at Princeton University, Princeton, NJ.

Study of the field-sequential modulation of Nd:YVO4/MgO:PPLN based intra-cavity frequency doubling green laser

NASA Astrophysics Data System (ADS)

Zhang, Bin; Gan, Yi; Xu, Chang-Qing

2018-06-01

The field sequential modulation of a Nd:YVO4/MgO:PPLN intra-cavity, frequency doubling green laser was studied. The modulation frequency was set at 1 kHz and the duty cycle was changed from 20% to CW operation. It was shown that the quasi-phase matched (QPM) temperature decreases with an increase of the modulation duty cycle, and in turn causing the peak efficiency to rise. It was found that the temperature change in MgO:PPLN and the thermal lens effect in Nd:YVO4 crystal were the respective origins of these observed experimental phenomena.

Temporally resolved proton radiography of rapidly varying electric and magnetic fields in laser-driven capacitor coil targets

NASA Astrophysics Data System (ADS)

Morace, A.; Santos, J. J.; Bailly-Grandvaux, M.; Ehret, M.; Alpinaniz, J.; Brabetz, C.; Schaumann, G.; Volpe, L.

2017-02-01

Understanding the dynamics of rapidly varying electromagnetic fields in intense short pulse laser plasma interactions is of key importance to understand the mechanisms at the basis of a wide variety of physical processes, from high energy density physics and fusion science to the development of ultrafast laser plasma devices to control laser-generated particle beams. Target normal sheath accelerated (TNSA) proton radiography represents an ideal tool to diagnose ultrafast electromagnetic phenomena, providing 2D spatially and temporally resolved radiographs with temporal resolution varying from 2-3 ps to few tens of ps. In this work we introduce the proton radiography technique and its application to diagnose the spatial and temporal evolution of electromagnetic fields in laser-driven capacitor coil targets.

Compositional and Microstructural Evolution of Olivine Under Multiple-Cycle Pulsed Laser Irradiation as Revealed by FIB/Field-Emission TEM

NASA Technical Reports Server (NTRS)

Christoffersen, R.; Loeffler, M. J.; Dukes, C. A.; Keller, L. P.; Baragiola, R. A.

2016-01-01

The use of pulsed laser irradiation to simulate the short duration, high-energy conditions characteristic of micrometeorite impacts is now an established approach in experimental space weathering studies. The laser generates both melt and vapor deposits that contain nanophase metallic Fe (npFe(sup 0)) grains with size distributions and optical properties similar to those in natural impact-generated melt and vapor deposits. There remains uncertainty, however, about how well lasers simulate the mechanical work and internal (thermal) energy partitioning that occurs in actual impacts. We are currently engaged in making a direct comparison between the products of laser irradiation and experimental/natural hypervelocity impacts. An initial step reported here is to use analytical SEM and TEM is to attain a better understanding of how the microstructure and composition of laser deposits evolve over multiple cycles of pulsed laser irradiation.

Effect of Nd:YAG and CO2 Laser Irradiation on Prevention of Enamel Demineralization in Orthodontics: In Vitro Study.

PubMed

Paulos, Renato Siva; Seino, Priscila Yumi; Fukushima, Karen Akemi; Marques, Marcia Martins; de Almeida, Fernanda Campos Sousa; Ramalho, Karen Muller; de Freitas, Patricia Moreira; Brugnera, Aldo; Moreira, Maria Stella

2017-05-01

The aim of this study was to investigate Nd:YAG and CO 2 laser effects in the prevention of demineralization in deeper layers of enamel via successive acid challenge cycles. Lasers are promising in the prevention of enamel demineralization around the orthodontic brackets; however, there are very few studies that evaluate if the effects of treatment could be extended after successive acid challenge cycles due to permanent enamel structural alterations. Human enamel samples were divided into five groups (n = 12): G1-application of 1.23% acidulated fluoride phosphate gel (AFP, control); G2-Nd:YAG laser irradiation (0.6 W, 84.9 J/cm 2 , 10 Hz, 110 μs, contact mode); G3-Nd:YAG laser irradiation associated with AFP; G4-CO 2 laser irradiation (0.5 W, 28.6 J/cm 2 , 50 Hz, 5 μs, and 10 mm focal distance); and G5-CO 2 laser irradiation associated with AFP. The samples were submitted to successive acid challenge cycles. Quantitative light-induced fluorescence and scanning electron microscopy were used to assess enamel demineralization. The data were statistically compared (α = 5%). G1: 50.87 ± 4.57; G2: 47.72 ± 2.87; G3: 50.96 ± 4.01; G4: 28.21 ± 2.19; and G5: 30.13 ± 6.38. The CO 2 laser groups had significantly lower mineral losses than those observed in all other groups after successive acid challenge cycles. Only the CO 2 laser (10.6 μm) irradiation prevents enamel demineralization around the orthodontic brackets even after exposure to successive acid challenges. The CO 2 laser at 10.6 μm showed a deeper effect in enamel regarding caries prevention.

High power CO2 coherent ladar haven't quit the stage of military affairs

NASA Astrophysics Data System (ADS)

Zhang, Heyong

2015-05-01

The invention of the laser in 1960 created the possibility of using a source of coherent light as a transmitter for a laser radar (ladar). Coherent ladar shares many of the basic features of more common microwave radars. However, it is the extremely short operating wavelength of lasers that introduces new military applications, especially in the area of missile identification, space target tracking, remote rang finding, camouflage discrimination and toxic agent detection. Therefore, the most popular application field such as laser imaging and ranging were focused on CO2 laser in the last few decades. But during the development of solid state and fiber laser, some people said that the CO2 laser will be disappeared and will be replaced by the solid and fiber laser in the field of military and industry. The coherent CO2 laser radar will have the same destiny in the field of military affairs. However, to my opinion, the high power CO2 laser will be the most important laser source for laser radar and countermeasure in the future.

Development of Rust Stripping System using High Power Laser

NASA Astrophysics Data System (ADS)

Shirakawa, Kazuomi; Ohashi, Katsuaki; Ashidate, Shuichi; Kurosawa, Kiyoshi; Nakayama, Michio; Uchida, Yutaka; Nobusada, Yuuji

The repainting cycle depends on removal of rust in maintenance of outdoor steel-frame structural facilities. However existing stripping process, which is usually made by hands with brushes, cannot strip the rust completely in maintenance of power transmission towers, for example. To solve this problem, we investigated laser fluence and pulse width for removal of rust using DPSSL (Diode Pumped Solid State Laser), and selected optimum laser supply. Then we checked the effect of laser stripping on prolongation of the repainting cycle compared with the conventional stripping process. Utilizing results of the research, we developed rust stripping system using DPSSL. From the results of field trial of rust removal operation using this system at high places of a power transmission tower, possibility of practical use of the system for the maintenance was confirmed.

Concepts for laser beam parameter monitoring during industrial mass production

NASA Astrophysics Data System (ADS)

Harrop, Nicholas J.; Maerten, Otto; Wolf, Stefan; Kramer, Reinhard

2017-02-01

In today's industrial mass production, lasers have become an established tool for a variety of processes. As with any other tool, mechanical or otherwise, the laser and its ancillary components are prone to wear and ageing. Monitoring of these ageing processes at full operating power of an industrial laser is challenging for a range of reasons. Not only the damage threshold of the measurement device itself, but also cycle time constraints in industrial processing are just two of these challenges. Power measurement, focus spot size or full beam caustic measurements are being implemented in industrial laser systems. The scope of the measurement and the amount of data collected is limited by the above mentioned cycle time, which in some cases can only be a few seconds. For successful integration of these measurement systems into automated production lines, the devices must be equipped with standardized communication interfaces, enabling a feedback loop from the measurement device to the laser processing systems. If necessary these measurements can be performed before each cycle. Power is determined with either static or dynamic calorimetry while camera and scanning systems are used for beam profile analysis. Power levels can be measured from 25W up to 20 kW, with focus spot sizes between 10μm and several millimeters. We will show, backed by relevant statistical data, that defects or contamination of the laser beam path can be detected with applied measurement systems, enabling a quality control chain to prevent process defects.

Laser materials processing of complex components: from reverse engineering via automated beam path generation to short process development cycles

NASA Astrophysics Data System (ADS)

Görgl, Richard; Brandstätter, Elmar

2017-01-01

The article presents an overview of what is possible nowadays in the field of laser materials processing. The state of the art in the complete process chain is shown, starting with the generation of a specific components CAD data and continuing with the automated motion path generation for the laser head carried by a CNC or robot system. Application examples from laser cladding and laser-based additive manufacturing are given.

Generation and manipulation of attosecond light pulses

NASA Astrophysics Data System (ADS)

Gaarde, Mette

2006-05-01

Attosecond pulses of light can be generated in the extremely non-linear interactions between an ultrashort, intense laser pulse and a gas of atoms, via the process of high harmonic generation [1,2]. In one approach, a number of odd harmonics of rougly equal strength are combined to form a train of sub-femtosecond pulses. If the harmonics are locked in phase to each other, the train will consist of the emission of one attosecond pulse every half cycle of the driving laser field [1,3]. It is in general not trivial to ensure that the harmonics are phase-locked as they are generated with intrinsically different phases. These phases originate in the strong field dynamics of the light-matter interaction [4].We will discuss different ways of generating and manipulating attosecond pulses via high harmonic generation. We will show how the harmonics can be phase-locked and better synchronized so as to form optimal pulse trains [3]. We will also show that it is possible to generate trains of pulses separated by a full laser cycle, by combining the driving laser field with its second harmonic [5]. The strong field continuum dynamics driven by the two-color field is very different from that of the one-color field and varies strongly with the delay between the two laser fields [6]. (1) P. M. Paul et al, Science 292, 1689 (2001).(2) M. Hentschel et al, Nature 414, 509 (2001).(3) R. Lopez-Martens et al, PRL 94, 033001 (2005).(4) P. Antoine, A. L'Huillier, and M. Lewenstein, PRL 77, 1234 (1996).(5) J. Mauritsson et al, in preparation (2006).(6) M. B. Gaarde et al, in preparation (2006).

Electron emission perpendicular to the polarization direction in laser-assisted XUV atomic ionization

NASA Astrophysics Data System (ADS)

Gramajo, A. A.; Della Picca, R.; Arbó, D. G.

2017-08-01

We present a theoretical study of ionization of the hydrogen atom due to an XUV pulse in the presence of an infrared (IR) laser with both fields linearly polarized in the same direction. In particular, we study the energy distribution of photoelectrons emitted perpendicularly to the polarization direction. As we previously showed in Gramajo et al. [Phys. Rev. A 94, 053404 (2016), 10.1103/PhysRevA.94.053404] for parallel emission, by means of a very simple semiclassical model which considers electron trajectories born at different ionization times, the electron energy spectrum can be interpreted as the interplay of intra- and intercycle interferences. However, contrary to the case of parallel emission the intracycle interference pattern stems from the coherent superposition of four electron trajectories giving rise to (i) interference of electron trajectories born during the same half cycle (intra-half-cycle interference) and (ii) interference between electron trajectories born during the first half cycle with those born during the second half cycle (inter-half-cycle interference). The intercycle interference is responsible for the formation of the sidebands. We also show that the destructive inter-half-cycle interference for the absorption and emission of an even number of IR laser photons is responsible for the characteristic sidebands in the perpendicular direction separated by twice the IR photon energy. This contrasts with the emission along the polarization axis (all sideband orders are present) since intra-half-cycle interferences do not exist in that case. The intracycle interference pattern works as a modulation of the sidebands and, in the same way, it is modulated by the intra-half-cycle interference pattern. We analyze the dependence of the energy spectrum on the laser intensity and the time delay between the XUV pulse and the IR laser. Finally, we show that our semiclassical simulations are in very good agreement with quantum calculations within the strong-field approximation and the numerical solution of the time-dependent Schrödinger equation, giving rise to nonzero emission, in contraposition to other theories.

Rabi oscillations in extreme ultraviolet ionization of atomic argon

NASA Astrophysics Data System (ADS)

Flögel, Martin; Durá, Judith; Schütte, Bernd; Ivanov, Misha; Rouzée, Arnaud; Vrakking, Marc J. J.

2017-02-01

We demonstrate Rabi oscillations in nonlinear ionization of argon by an intense femtosecond extreme ultraviolet (XUV) laser field produced by high-harmonic generation. We monitor the formation of A r2 + as a function of the time delay between the XUV pulse and an additional near-infrared (NIR) femtosecond laser pulse, and show that the population of an A r+* intermediate resonance exhibits strong modulations both due to an NIR laser-induced Stark shift and XUV-induced Rabi cycling between the ground state of A r+ and the A r+* excited state. Our experiment represents a direct experimental observation of a Rabi-cycling process in the XUV regime.

Recent Developments in Microwave Ion Clocks

NASA Astrophysics Data System (ADS)

Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

We review the development of microwave-frequency standards based on trapped ions. Following two distinct paths, microwave ion clocks have evolved greatly in the last twenty years since the earliest Paul-trap-based units. Laser-cooled ion frequency standards reduce the second-order Doppler shift from ion micromotion and thermal secular motion achieving good signal-to-noise ratios via cycling transitions where as many as ~10^8 photons per second per ion may be scattered. Today, laser-cooled ion standards are based on linear Paul traps which hold ions near the node line of the trapping electric field, minimizing micromotion at the trapping-field frequency and the consequent second-order Doppler frequency shift. These quadrupole (radial) field traps tightly confine tens of ions to a crystalline single-line structure. As more ions are trapped, space charge forces some ions away from the node-line axis and the second-order Doppler effect grows larger, even at negligibly small secular temperatures. Buffer-gas-cooled clocks rely on large numbers of ions, typically ~10^7, optically pumped by a discharge lamp at a scattering rate of a few photons per second per ion. To reduce the second-order Doppler shift from space charge repulsion of ions from the trap node line, novel multipole ion traps are now being developed where ions are weakly bound with confining fields that are effectively zero through the trap interior and grow rapidly near the trap electrode ``walls''.

Imaging ultrafast dynamics of molecules with laser-induced electron diffraction.

PubMed

Lin, C D; Xu, Junliang

2012-10-14

We introduce a laser-induced electron diffraction method (LIED) for imaging ultrafast dynamics of small molecules with femtosecond mid-infrared lasers. When molecules are placed in an intense laser field, both low- and high-energy photoelectrons are generated. According to quantitative rescattering (QRS) theory, high-energy electrons are produced by a rescattering process where electrons born at the early phase of the laser pulse are driven back to rescatter with the parent ion. From the high-energy electron momentum spectra, field-free elastic electron-ion scattering differential cross sections (DCS), or diffraction images, can be extracted. With mid-infrared lasers as the driving pulses, it is further shown that the DCS can be used to extract atomic positions in a molecule with sub-angstrom spatial resolution, in close analogy to the standard electron diffraction method. Since infrared lasers with pulse duration of a few to several tens of femtoseconds are already available, LIED can be used for imaging dynamics of molecules with sub-angstrom spatial and a few-femtosecond temporal resolution. The first experiment with LIED has shown that the bond length of oxygen molecules shortens by 0.1 Å in five femtoseconds after single ionization. The principle behind LIED and its future outlook as a tool for dynamic imaging of molecules are presented.

Fast Ignition Thermonuclear Fusion: Enhancement of the Pellet Gain by the Colossal-Magnetic-Field Shells

NASA Astrophysics Data System (ADS)

Stefan, V. Alexander

2013-10-01

The fast ignition fusion pellet gain can be enhanced by a laser generated B-field shell. The B-field shell, (similar to Earth's B-field, but with the alternating B-poles), follows the pellet compression in a frozen-in B-field regime. A properly designed laser-pellet coupling can lead to the generation of a B-field shell, (up to 100 MG), which inhibits electron thermal transport and confines the alpha-particles. In principle, a pellet gain of few-100s can be achieved in this manner. Supported in part by Nikola Tesla Labs, Stefan University, 1010 Pearl, La Jolla, CA 92038-1007.

High-power parametric amplification of 11.8-fs laser pulses with carrier-envelope phase control.

PubMed

Zinkstok, R Th; Witte, S; Hogervorst, W; Eikema, K S E

2005-01-01

Phase-stable parametric chirped-pulse amplification of ultrashort pulses from a carrier-envelope phase-stabilized mode-locked Ti:sapphire oscillator (11.0 fs) to 0.25 mJ/pulse at 1 kHz is demonstrated. Compression with a grating compressor and a LCD shaper yields near-Fourier-limited 11.8-fs pulses with an energy of 0.12 mJ. The amplifier is pumped by 532-nm pulses from a synchronized mode-locked laser, Nd:YAG amplifier system. This approach is shown to be promising for the next generation of ultrafast amplifiers aimed at producing terawatt-level phase-controlled few-cycle laser pulses.

Excitation of H+2 with one-cycle laser pulses: shaped post-laser-field electronic oscillations, generation of higher- and lower-order harmonics

NASA Astrophysics Data System (ADS)

Paramonov, Guennaddi K.; Kühn, Oliver; Bandrauk, André D.

2017-08-01

Non-Born-Oppenheimer quantum dynamics of H+2 excited by shaped one-cycle laser pulses linearly polarised along the molecular axis have been studied by the numerical solution of the time-dependent Schrödinger equation within a three-dimensional model, including the internuclear separation, R, and the electron coordinates z and ρ. Laser carrier frequencies corresponding to the wavelengths λl = 25 nm through λl = 400 nm were used and the amplitudes of the pulses were chosen such that the energy of H+2 was close to its dissociation threshold at the end of any laser pulse applied. It is shown that there exists a characteristic oscillation frequency ωosc ≃ 0.2265 au (corresponding to the period of τosc ≃ 0.671 fs and the wavelength of λosc ≃ 201 nm) that manifests itself as a 'carrier' frequency of temporally shaped oscillations of the time-dependent expectation values ⟨z ⟩ and ⟨∂V/∂z ⟩ that emerge at the ends of the laser pulses and exist on a timescale of at least 50 fs. Time-dependent expectation values ⟨ρ⟩ and ⟨∂V /∂ρ⟩ of the optically passive degree of freedom, ρ, demonstrate post-laser-field oscillations at two basic frequencies ωρ1 ≈ ωosc and ωρ2 ≈ 2ωosc. Power spectra associated with the electronic motion show higher- and lower-order harmonics with respect to the driving field.

Photoassociation dynamics driven by a modulated two-color laser field

NASA Astrophysics Data System (ADS)

Zhang, Wei; Zhao, Ze-Yu; Xie, Ting; Wang, Gao-Ren; Huang, Yin; Cong, Shu-Lin

2011-11-01

Photoassociation (PA) dynamics of ultracold cesium atoms steered by a modulated two-color laser field E(t)=E0f(t)cos((2π)/(Tp)-φ)cos(ωLt) is investigated theoretically by numerically solving the time-dependent Schrödinger equation. The PA dynamics is sensitive to the phase of envelope (POE) φ and the period of the envelope Tp, which indicates that it can be controlled by varying POE φ and period Tp. Moreover, we introduce the time- and frequency-resolved spectrum to illustrate how the POE φ and the period Tp influence the intensity distribution of the modulated laser pulse and hence change the time-dependent population distribution of photoassociated molecules. When the Gaussian envelope contains a few oscillations, the PA efficiency is also dependent on POE φ. The modulated two-color laser field is available in the current experiment based on laser mode-lock technology.

Ionization, photoelectron dynamics and elastic scattering in relativistic, ultra-strong field

NASA Astrophysics Data System (ADS)

Luo, Sui

Ultrastrong laser-matter interaction has direct bearing to next generation technologies including plasma acceleration, laser fusion and attosecond X-ray generation. The commonly known physics in strong field becomes different as one progress to ultrastrong field. The works presented in this dissertation theoretically study the influence of relativistic effect and magnetic component of the laser field on the ionization, photoelectron dynamics and elastic scattering processes. The influence of magnetic component (B laser) of circularly polarized (CP) ultrastrong fields (up to3 x 1022 W/cm2) on atomic bound state dynamics is investigated. The Poincare plots are used to find the changes in trajectory energies are on the order of a few percent for intensities up to1 x 1022 W/cm2. It is found that at intensities where ionization approaches 50% for the bound state, the small changes from Blaser of the circular polarized light can actually result in a several-fold decrease in ionization probability. The force on the bound electron exerted by the Lorentz force from B laser is perpendicular to the rotating plane of the circular polarized light, and this nature makes those trajectories which are aligned away from the minimum in the potential barrier stabilized against tunneling ionization. Our results provide a classical understanding for ionization in ultrastrong fields and indicate that relativistic effects in ultrastrong field ionization may most easily be seen with CP fields. The photoelectron energy spectra from elastic rescattering in ultrastrong laser fields (up to 2x1019 W/cm2) is studied by using a relativistic adaption of a semi-classical three-step recollision model. The Hartree-Fock scattering potentials are used in calculating the elastic rescattering for both hydrogenlike and noble gas species. It is found that there is a reduction in elastic rescattering for intensities beyond 6 x 1016 W/cm2 when the laser Lorentz deflection of the photoelectron exceeds its wave-function spread. A relativistic rescattering enhancement occurs at 2 x 1018 W/cm2, commensurate with relativistic motion of a classical electron in a single field cycle. The good comparison between the results with available experiments suggests the theory approach is well suited to modeling scattering in the ultrastrong intensity regime. We investigate the elastic scattering process as it changes from strong to ultrastrong fields with the photoelectron angular distributions from Ne, Ar, and Xe. Noble gas species with Hartree-Fock scattering potentials show a reduction in elastic rescattering with the increasing energy of ultrastrong fields. It is found that as one increases the returning photoelectron energy, rescattering becomes the dominating mechanism behind the yield distribution as the emission angle for all the species extends from 0° to 90°. The relativistic effects and the magnetic field do not change the angular distribution until one is well into the Gamma r "1 regime where the Lorentz defection significantly reduces the yield. As we proceed to the highest energy, the angular emission range narrows as the mechanism changes over to backscattering into narrow angles along the electric field.

Mechanically delaminated few layered MoS2 nanosheets based high performance wire type solid-state symmetric supercapacitors

NASA Astrophysics Data System (ADS)

Krishnamoorthy, Karthikeyan; Pazhamalai, Parthiban; Veerasubramani, Ganesh Kumar; Kim, Sang Jae

2016-07-01

Two dimensional nanostructures are increasingly used as electrode materials in flexible supercapacitors for portable electronic applications. Herein, we demonstrated a ball milling approach for achieving few layered molybdenum disulfide (MoS2) via exfoliation from their bulk. Physico-chemical characterizations such as X-ray diffraction, field emission scanning electron microscope, and laser Raman analyses confirmed the occurrence of exfoliated MoS2 sheets with few layers from their bulk via ball milling process. MoS2 based wire type solid state supercapacitors (WSCs) are fabricated and examined using cyclic voltammetry (CV), electrochemical impedance spectroscopy, and galvanostatic charge discharge (CD) measurements. The presence of rectangular shaped CV curves and symmetric triangular shaped CD profiles suggested the mechanism of charge storage in MoS2 WSC is due to the formation of electrochemical double layer capacitance. The MoS2 WSC device delivered a specific capacitance of 119 μF cm-1, and energy density of 8.1 nW h cm-1 with better capacitance retention of about 89.36% over 2500 cycles, which ensures the use of the ball milled MoS2 for electrochemical energy storage devices.

Controllable Terahertz Radiation from a Linear-Dipole Array Formed by a Two-Color Laser Filament in Air.

PubMed

Zhang, Zhelin; Chen, Yanping; Chen, Min; Zhang, Zhen; Yu, Jin; Sheng, Zhengming; Zhang, Jie

2016-12-09

We demonstrate effective control on the carrier-envelope phase and angular distribution as well as the peak intensity of a nearly single-cycle terahertz pulse emitted from a laser filament formed by two-color, the fundamental and the corresponding second harmonics, femtosecond laser pulses propagating in air. Experimentally, such control has been performed by varying the filament length and the initial phase difference between the two-color laser components. A linear-dipole-array model, including the descriptions of both the generation (via laser field ionization) and propagation of the emitted terahertz pulse, is proposed to present a quantitative interpretation of the observations. Our results contribute to the understanding of terahertz generation in a femtosecond laser filament and suggest a practical way to control the electric field of a terahertz pulse for potential applications.

Laser-driven electron beam acceleration and future application to compact light sources

NASA Astrophysics Data System (ADS)

Hafz, N.; Jeong, T. M.; Lee, S. K.; Pae, K. H.; Sung, J. H.; Choi, I. W.; Yu, T. J.; Jeong, Y. U.; Lee, J.

2009-07-01

Laser-driven plasma accelerators are gaining much attention by the advanced accelerator community due to the potential these accelerators hold in miniaturizing future high-energy and medium-energy machines. In the laser wakefield accelerator (LWFA), the ponderomotive force of an ultrashort high intensity laser pulse excites a longitudinal plasma wave or bubble. Due to huge charge separation, electric fields created in the plasma bubble can be several orders of magnitude higher than those available in conventional microwave and RF-based accelerator facilities which are limited (up to ˜100 MV/m) by material breakdown. Therefore, if an electron bunch is injected into the bubble in phase with its field, it will gain relativistic energies within an extremely short distance. Here, in the LWFA we show the generation of high-quality and high-energy electron beams up to the GeV-class within a few millimeters of gas-jet plasmas irradiated by tens of terawatt ultrashort laser pulses. Thus we realize approximately four orders of magnitude acceleration gradients higher than available by conventional technology. As a practical application of the stable high-energy electron beam generation, we are planning on injecting the electron beams into a few-meters long conventional undulator in order to realize compact X-ray synchrotron (immediate) and FEL (future) light sources. Stable laser-driven electron beam and radiation devices will surely open a new era in science, medicine and technology and will benefit a larger number of users in those fields.

Ultracold Anions for High-Precision Antihydrogen Experiments

NASA Astrophysics Data System (ADS)

Cerchiari, G.; Kellerbauer, A.; Safronova, M. S.; Safronova, U. I.; Yzombard, P.

2018-03-01

Experiments with antihydrogen (H ¯) for a study of matter-antimatter symmetry and antimatter gravity require ultracold H ¯ to reach ultimate precision. A promising path towards antiatoms much colder than a few kelvin involves the precooling of antiprotons by laser-cooled anions. Because of the weak binding of the valence electron in anions—dominated by polarization and correlation effects—only few candidate systems with suitable transitions exist. We report on a combination of experimental and theoretical studies to fully determine the relevant binding energies, transition rates, and branching ratios of the most promising candidate La- . Using combined transverse and collinear laser spectroscopy, we determined the resonant frequency of the laser cooling transition to be ν =96.592 713 (91 ) THz and its transition rate to be A =4.90 (50 )×104 s-1 . Using a novel high-precision theoretical treatment of La- we calculated yet unmeasured energy levels, transition rates, branching ratios, and lifetimes to complement experimental information on the laser cooling cycle of La- . The new data establish the suitability of La- for laser cooling and show that the cooling transition is significantly stronger than suggested by a previous theoretical study.

Ultracold Anions for High-Precision Antihydrogen Experiments.

PubMed

Cerchiari, G; Kellerbauer, A; Safronova, M S; Safronova, U I; Yzombard, P

2018-03-30

Experiments with antihydrogen (H[over ¯]) for a study of matter-antimatter symmetry and antimatter gravity require ultracold H[over ¯] to reach ultimate precision. A promising path towards antiatoms much colder than a few kelvin involves the precooling of antiprotons by laser-cooled anions. Because of the weak binding of the valence electron in anions-dominated by polarization and correlation effects-only few candidate systems with suitable transitions exist. We report on a combination of experimental and theoretical studies to fully determine the relevant binding energies, transition rates, and branching ratios of the most promising candidate La^{-}. Using combined transverse and collinear laser spectroscopy, we determined the resonant frequency of the laser cooling transition to be ν=96.592 713(91)  THz and its transition rate to be A=4.90(50)×10^{4}  s^{-1}. Using a novel high-precision theoretical treatment of La^{-} we calculated yet unmeasured energy levels, transition rates, branching ratios, and lifetimes to complement experimental information on the laser cooling cycle of La^{-}. The new data establish the suitability of La^{-} for laser cooling and show that the cooling transition is significantly stronger than suggested by a previous theoretical study.

Terahertz Radiation from Laser Created Plasma by Applying a Transverse Static Electric Field

NASA Astrophysics Data System (ADS)

Fukuda, Takuya; Katahira, Koji; Yugami, Noboru; Sentoku, Yasuhiko; Sakagami, Hitoshi; Nagatomo, Hideo

2016-10-01

Terahertz (THz) radiation, which is emitted in narrow cone in the forward direction from laser created plasma has been observed by N.Yugami et al.. Additionally, Löffler et al. have observed that a significantly increased THz emission intensity in the forward direction when the transverse static electric field is applied to the plasma. The purpose of our study is to derive the mechanism of the THz radiation from laser created plasma by applying the transverse static electric field. To study the radiation mechanism, we conducted 2D-PIC simulation. With the static electric field of 10 kV/cm and gas density of 1020 cm-3, we obtain 1.2 THz single cycle pulse radiation, whose intensity is 1.3 ×105 W/cm2. The magnetic field called ``picket fence mode'' is generated in the laser created plasma. At the boundary surface between the plasma and vacuum, the magnetic field is canceled because eddy current flows. We conclude that the temporal behavior of the magnetic field at the boundary surface radiates the THz wave.

Phase control of attosecond pulses in a train

NASA Astrophysics Data System (ADS)

Guo, Chen; Harth, Anne; Carlström, Stefanos; Cheng, Yu-Chen; Mikaelsson, Sara; Mårsell, Erik; Heyl, Christoph; Miranda, Miguel; Gisselbrecht, Mathieu; Gaarde, Mette B.; Schafer, Kenneth J.; Mikkelsen, Anders; Mauritsson, Johan; Arnold, Cord L.; L'Huillier, Anne

2018-02-01

Ultrafast processes in matter can be captured and even controlled by using sequences of few-cycle optical pulses, which need to be well characterized, both in amplitude and phase. The same degree of control has not yet been achieved for few-cycle extreme ultraviolet pulses generated by high-order harmonic generation (HHG) in gases, with duration in the attosecond range. Here, we show that by varying the spectral phase and carrier-envelope phase (CEP) of a high-repetition rate laser, using dispersion in glass, we achieve a high degree of control of the relative phase and CEP between consecutive attosecond pulses. The experimental results are supported by a detailed theoretical analysis based upon the semi-classical three-step model for HHG.

Coherent control in simple quantum systems

NASA Technical Reports Server (NTRS)

Prants, Sergey V.

1995-01-01

Coherent dynamics of two, three, and four-level quantum systems, simultaneously driven by concurrent laser pulses of arbitrary and different forms, is treated by using a nonperturbative, group-theoretical approach. The respective evolution matrices are calculated in an explicit form. General aspects of controllability of few-level atoms by using laser fields are treated analytically.

Generation of 70-fs pulses at 286 μm from a mid-infrared fiber laser

NASA Astrophysics Data System (ADS)

Woodward, R. I.; Hudson, D. D.; Fuerbach, A.; Jackson, S. D.

2017-12-01

We propose and demonstrate a simple route to few-optical-cycle pulse generation from a mid-infrared fiber laser through nonlinear compression of pulses from a holmium-doped fiber oscillator using a short length of chalcogenide fiber and a grating pair. Pulses from the oscillator with 265-fs duration at 2.86 {\\mu}m are spectrally broadened through self-phase modulation in step-index As2S3 fiber to 141-nm bandwidth and then re-compressed to 70 fs (7.3 optical cycles). These are the shortest pulses from a mid-infrared fiber system to date, and we note that our system is compact, robust, and uses only commercially available components. The scalability of this approach is also discussed, supported by numerical modeling.

Brijuni Conference (10th), Imaging in Space and Time. Held in Brijuni, Croatia on 28 August-1 September 2006

DTIC Science & Technology

2006-09-01

Solitons in Photonic Lattices 9.40-10.00 discussion 10.00-10.40 S. Tsai: Imaging the quantum coherence: Readout for superconducting multi-qubit system...dynamics in the few-cycle pulse limit 11.40-11.50 discussion 11.50-12.10 T. Ban: Manipulations of the atom velocity with femtosecond laser frequency comb...Conference X, Brijuni, Croatia, 28.08.-01.09.2006. MANIPULATION OF THE ATOM VELOCITY WITH FEMTOSECOND LASER FREQUENCY COMB Ticijana Ban, D. Aumiler, H

Beam collimation and energy spectrum compression of laser-accelerated proton beams using solenoid field and RF cavity

NASA Astrophysics Data System (ADS)

Teng, J.; Gu, Y. Q.; Zhu, B.; Hong, W.; Zhao, Z. Q.; Zhou, W. M.; Cao, L. F.

2013-11-01

This paper presents a new method of laser produced proton beam collimation and spectrum compression using a combination of a solenoid field and a RF cavity. The solenoid collects laser-driven protons efficiently within an angle that is smaller than 12 degrees because it is mounted few millimeters from the target, and collimates protons with energies around 2.3 MeV. The collimated proton beam then passes through a RF cavity to allow compression of the spectrum. Particle-in-cell (PIC) simulations demonstrate the proton beam transport in the solenoid and RF electric fields. Excellent energy compression and collection efficiency of protons are presented. This method for proton beam optimization is suitable for high repetition-rate laser acceleration proton beams, which could be used as an injector for a conventional proton accelerator.

Controlling successive ionic layer absorption and reaction cycles to optimize silver nanoparticle-induced localized surface plasmon resonance effects on the paper strip

NASA Astrophysics Data System (ADS)

Lee, Jae-Chul; Kim, Wansun; Park, Hun-Kuk; Choi, Samjin

2017-03-01

This study investigates why a silver nanoparticle (SNP)-induced surface-enhanced Raman scattering (SERS) paper chip fabricated at low successive ionic layer absorption and reaction (SILAR) cycles leads to a high SERS enhancement factor (7 × 108) with an inferior nanostructure and without generating a hot spot effect. The multi-layered structure of SNPs on cellulose fibers, verified by magnified scanning electron microscopy (SEM) and analyzed by a computational simulation method, was hypothesized as the reason. The pattern of simulated local electric field distribution with respect to the number of SILAR cycles showed good agreement with the experimental Raman intensity, regardless of the wavelength of the excitation laser sources. The simulated enhancement factor at the 785-nm excitation laser source (2.8 × 109) was 2.5 times greater than the experimental enhancement factor (1.1 × 109). A 532-nm excitation laser source exhibited the highest maximum local electric field intensity (1.9 × 1011), particularly at the interparticle gap called a hot spot. The short wavelength led to a strong electric field intensity caused by strong electromagnetic coupling arising from the SNP-induced local surface plasmon resonance (LSPR) effects through high excitation energy. These findings suggest that our paper-based SILAR-fabricated SNP-induced LSPR model is valid for understanding SNP-induced LSPR effects.

Uniform laser-driven relativistic electron layer for coherent Thomson scattering.

PubMed

Wu, H-C; Meyer-ter-Vehn, J; Fernández, J; Hegelich, B M

2010-06-11

A novel scheme is proposed to generate uniform relativistic electron layers for coherent Thomson backscattering. A few-cycle laser pulse is used to produce the electron layer from an ultrathin solid foil. The key element of the new scheme is an additional foil that reflects the drive-laser pulse, but lets the electrons pass almost unperturbed. Making use of two-dimensional particle-in-cell simulations and well-known basic theory, it is shown that the electrons, after interacting with both the drive and reflected laser pulses, form a very uniform flyer freely cruising with a high relativistic γ factor exactly in the drive-laser direction (no transverse momentum). It backscatters the probe light with a full Doppler shift factor of 4γ(2). The reflectivity and its decay due to layer expansion are discussed.

The suppression of radiation reaction and laser field depletion in laser-electron beam interaction

NASA Astrophysics Data System (ADS)

Ong, J. F.; Moritaka, T.; Takabe, H.

2018-03-01

The effects of radiation reaction (RR) have been studied extensively by using the interaction of ultraintense lasers with a counter-propagating relativistic electron. At the laser intensity at the order of 1023 W/cm2, the effects of RR are significant in a few laser periods for a relativistic electron. However, a laser at such intensity is tightly focused and the laser energy is usually assumed to be fixed. Then, the signal of RR and energy conservation cannot be guaranteed. To assess the effects of RR in a tightly focused laser pulse and the evolution of the laser energy, we simulated this interaction with a beam of 109 electrons by means of a Particle-In-Cell method. We observe that the effects of RR are suppressed due to the ponderomotive force and accompanied by a non-negligible amount of laser field energy reduction. This is because the ponderomotive force prevents the electrons from approaching the center of the laser pulse and leads to an interaction at the weaker field region. At the same time, the laser energy is absorbed through ponderomotive acceleration. Thus, the kinetic energy of the electron beam has to be carefully selected such that the effects of RR become obvious.

EDITORIAL: Focus on Attosecond Physics

NASA Astrophysics Data System (ADS)

Bandrauk, André D.; Krausz, Ferenc; Starace, Anthony F.

2008-02-01

Investigations of light-matter interactions and motion in the microcosm have entered a new temporal regime, the regime of attosecond physics. It is a main 'spin-off' of strong field (i.e., intense laser) physics, in which nonperturbative effects are fundamental. Attosecond pulses open up new avenues for time-domain studies of multi-electron dynamics in atoms, molecules, plasmas, and solids on their natural, quantum mechanical time scale and at dimensions shorter than molecular and even atomic scales. These capabilities promise a revolution in our microscopic knowledge and understanding of matter. The recent development of intense, phase-stabilized femtosecond (10-15 s) lasers has allowed unparalleled temporal control of electrons from ionizing atoms, permitting for the first time the generation and measurement of isolated light pulses as well as trains of pulses on the attosecond (1 as = 10-18 s) time scale, the natural time scale of the electron itself (e.g., the orbital period of an electron in the ground state of the H atom is 152 as). This development is facilitating (and even catalyzing) a new class of ultrashort time domain studies in photobiology, photochemistry, and photophysics. These new coherent, sub-fs pulses carried at frequencies in the extreme ultraviolet and soft-x-ray spectral regions, along with their intense, synchronized near-infrared driver waveforms and novel metrology based on sub-fs control of electron-light interactions, are spawning the new science of attosecond physics, whose aims are to monitor, to visualize, and, ultimately, to control electrons on their own time and spatial scales, i.e., the attosecond time scale and the sub-nanometre (Ångstrom) spatial scale typical of atoms and molecules. Additional goals for experiment are to advance the enabling technologies for producing attosecond pulses at higher intensities and shorter durations. According to theoretical predictions, novel methods for intense attosecond pulse generation may in future involve using overdense plasmas. Electronic processes on sub-atomic spatio-temporal scales are the basis of chemical physics, atomic, molecular, and optical physics, materials science, and even some life science processes. Research in these areas using the new attosecond tools will advance together with the ability to control electrons themselves. Indeed, we expect that developments will advance in a way that is similar to advances that have occurred on the femtosecond time scale, in which much previous experimental and theoretical work on the interaction of coherent light sources has led to the development of means for 'coherent control' of nuclear motion in molecules. This focus issue of New Journal of Physics is centered on experimental and theoretical advances in the development of new methodologies and tools for electron control on the attosecond time scale. Topics such as the efficient generation of harmonics; the generation of attosecond pulses, including those having only a few cycles and those produced from overdense plasmas; the description of various nonlinear, nonperturbative laser-matter interactions, including many-electron effects and few-cycle pulse effects; the analysis of ultrashort propagation effects in atomic and molecular media; and the development of inversion methods for electron tomography, as well as many other topics, are addressed in the current focus issue dedicated to the new field of 'Attosecond Physics'. Focus on Attosecond Physics Contents Observing the attosecond dynamics of nuclear wavepackets in molecules by using high harmonic generation in mixed gases Tsuneto Kanai, Eiji J Takahashi, Yasuo Nabekawa and Katsumi Midorikawa Core-polarization effects in molecular high harmonic generation G Jordan and A Scrinzi Interferometric autocorrelation of an attosecond pulse train calculated using feasible formulae Y Nabekawa and K Midorikawa Attosecond pulse generation from aligned molecules—dynamics and propagation in H2+ E Lorin, S Chelkowski and A D Bandrauk Broadband generation in a Raman crystal driven by a pair of time-delayed linearly chirped pulses Miaochan Zhi and Alexei V Sokolov Ultrafast nanoplasmonics under coherent control Mark I Stockman Attosecond pulse carrier-envelope phase effects on ionized electron momentum and energy distributions: roles of frequency, intensity and an additional IR pulse Liang-You Peng, Evgeny A Pronin and Anthony F Starace Angular encoding in attosecond recollision Markus Kitzler, Xinhua Xie, Stefan Roither, Armin Scrinzi and Andrius Baltuska Polarization-resolved pump-probe spectroscopy with high harmonics Y Mairesse, S Haessler, B Fabre, J Higuet, W Boutu, P Breger, E Constant, D Descamps, E Mével, S Petit and P Salières Macroscopic effects in attosecond pulse generation T Ruchon, C P Hauri, K Varjú, E Mansten, M Swoboda, R López-Martens and A L'Huillier Monitoring long-term evolution of molecular vibrational wave packet using high-order harmonic generation M Yu Emelin, M Yu Ryabikin and A M Sergeev Intense single attosecond pulses from surface harmonics using the polarization gating technique S G Rykovanov, M Geissler, J Meyer-ter-Vehn and G D Tsakiris Imaging of carrier-envelope phase effects in above-threshold ionization with intense few-cycle laser fields M F Kling, J Rauschenberger, A J Verhoef, E Hasović, T Uphues, D B Milošević, H G Muller and M J J Vrakking Self-compression of optical laser pulses by filamentation A Mysyrowicz, A Couairon and U Keller Towards efficient generation of attosecond pulses from overdense plasma targets N M Naumova, C P Hauri, J A Nees, I V Sokolov, R Lopez-Martens and G A Mourou Quantum-path control in high-order harmonic generation at high photon energies Xiaoshi Zhang, Amy L Lytle, Oren Cohen, Margaret M Murnane and Henry C Kapteyn Time-resolved mapping of correlated electron emission from helium atom in an intense laser pulse C Ruiz and A Becker Pump and probe ultrafast electron dynamics in LiH: a computational study M Nest, F Remacle and R D Levine Exploring intense attosecond pulses D Charalambidis, P Tzallas, E P Benis, E Skantzakis, G Maravelias, L A A Nikolopoulos, A Peralta Conde and G D Tsakiris Attosecond timescale analysis of the dynamics of two-photon double ionization of helium Emmanuel Foumouo, Philippe Antoine, Henri Bachau and Bernard Piraux Generation of tunable isolated attosecond pulses in multi-jet systems V Tosa, V S Yakovlev and F Krausz Electron wavepacket control with elliptically polarized laser light in high harmonic generation from aligned molecules Y Mairesse, N Dudovich, J Levesque, M Yu Ivanov, P B Corkum and D M Villeneuve Tracing non-equilibrium plasma dynamics on the attosecond timescale in small clusters Ulf Saalmann, Ionut Georgescu and Jan M Rost Ionization in attosecond pulses: creating atoms without nuclei? John S Briggs and Darko Dimitrovski Angular distributions in double ionization of helium under XUV sub-femtosecond radiation P Lambropoulos and L A A Nikolopoulos Potential for ultrafast dynamic chemical imaging with few-cycle infrared lasers Toru Morishita, Anh-Thu Le, Zhangjin Chen and C D Lin Attosecond electron thermalization in laser-induced nonsequential multiple ionization: hard versus glancing collisions X Liu, C Figueira de Morisson Faria and W Becker Ion-charge-state chronoscopy of cascaded atomic Auger decay Th Uphues, M Schultze, M F Kling, M Uiberacker, S Hendel, U Heinzmann, N M Kabachnik and M Drescher Measurement of electronic structure from high harmonic generation in non-adiabatically aligned polyatomic molecules N Kajumba, R Torres, Jonathan G Underwood, J S Robinson, S Baker, J W G Tisch, R de Nalda, W A Bryan, R Velotta, C Altucci, I Procino, I C E Turcu and J P Marangos Wavelength dependence of sub-laser-cycle few-electron dynamics in strong-field multiple ionization O Herrwerth, A Rudenko, M Kremer, V L B de Jesus, B Fischer, G Gademann, K Simeonidis, A Achtelik, Th Ergler, B Feuerstein, C D Schröter, R Moshammer and J Ullrich Attosecond metrology in the few-optical-cycle regime G Sansone, E Benedetti, C Vozzi, S Stagira and M Nisoli Attosecond x-ray pulses produced by ultra short transverse slicing via laser electron beam interaction A A Zholents and M S Zolotorev

Phase- and intensity-resolved measurements of above threshold ionization by few-cycle pulses

NASA Astrophysics Data System (ADS)

Kübel, M.; Arbeiter, M.; Burger, C.; Kling, Nora G.; Pischke, T.; Moshammer, R.; Fennel, T.; Kling, M. F.; Bergues, B.

2018-07-01

We investigate the carrier-envelope phase (CEP) and intensity dependence of the longitudinal momentum distribution of photoelectrons resulting from above threshold ionization of argon by few-cycle laser pulses. The intensity of the pulses with a center wavelength of 750 nm is varied in a range between 0.7 × 1014 and 5.5× {10}14 {{W}} {cm}}-2. Our measurements reveal a prominent maximum in the CEP-dependent asymmetry at photoelectron energies of 2 U P (U P being the ponderomotive potential), that is persistent over the entire intensity range. Further local maxima are observed around 0.3 and 0.8 U P. The experimental results are in good agreement with theoretical results obtained by solving the three-dimensional time-dependent Schrödinger equation. We show that for few-cycle pulses, the amplitude of the CEP-dependent asymmetry provides a reliable measure for the peak intensity on target. Moreover, the measured asymmetry amplitude exhibits an intensity-dependent interference structure at low photoelectron energy, which could be used to benchmark model potentials for complex atoms.

Excited-state vibronic wave-packet dynamics in H2 probed by XUV transient four-wave mixing

NASA Astrophysics Data System (ADS)

Cao, Wei; Warrick, Erika R.; Fidler, Ashley; Leone, Stephen R.; Neumark, Daniel M.

2018-02-01

The complex behavior of a molecular wave packet initiated by an extreme ultraviolet (XUV) pulse is investigated with noncollinear wave mixing spectroscopy. A broadband XUV pulse spanning 12-16 eV launches a wave packet in H2 comprising a coherent superposition of multiple electronic and vibrational levels. The molecular wave packet evolves freely until a delayed few-cycle optical laser pulse arrives to induce nonlinear signals in the XUV via four-wave mixing (FWM). The angularly resolved FWM signals encode rich energy exchange processes between the optical laser field and the XUV-excited molecule. The noncollinear geometry enables spatial separation of ladder and V- or Λ-type transitions induced by the optical field. Ladder transitions, in which the energy exchange with the optical field is around 3 eV, appear off axis from the incident XUV beam. Each vibrationally revolved FWM line probes a different part of the wave packet in energy, serving as a promising tool for energetic tomography of molecular wave packets. V- or Λ-type transitions, in which the energy exchange is well under 1 eV, result in on-axis nonlinear signals. The first-order versus third-order interference of the on-axis signal serves as a mapping tool of the energy flow pathways. Intra- and interelectronic potential energy curve transitions are decisively identified. The current study opens possibilities for accessing complete dynamic information in XUV-excited complex systems.

The beat in laser-accelerated ion beams

NASA Astrophysics Data System (ADS)

Schnürer, M.; Andreev, A. A.; Abicht, F.; Bränzel, J.; Koschitzki, Ch.; Platonov, K. Yu.; Priebe, G.; Sandner, W.

2013-10-01

Regular modulation in the ion velocity distribution becomes detectable if intense femtosecond laser pulses with very high temporal contrast are used for target normal sheath acceleration of ions. Analytical and numerical analysis of the experimental observation associates the modulation with the half-cycle of the driving laser field period. In processes like ion acceleration, the collective and laser-frequency determined electron dynamics creates strong fields in plasma to accelerate the ions. Even the oscillatory motion of electrons and its influence on the acceleration field can dominate over smoothing effects in plasma if a high temporal contrast of the driving laser pulse is given. Acceleration parameters can be directly concluded out of the experimentally observed modulation period in ion velocity spectra. The appearance of the phenomenon at a temporal contrast of ten orders between the intensity of the pulse peak and the spontaneous amplified emission background as well as remaining intensity wings at picosecond time-scale might trigger further parameter studies with even higher contrast.

From quantum transitions to electronic motions

NASA Astrophysics Data System (ADS)

Krausz, Ferenc

2017-01-01

Laser spectroscopy and chromoscopy permit precision measurement of quantum transitions and captures atomic-scale dynamics, respectively. Frequency- and time-domain metrology ranks among the supreme laser disciplines in fundamental science. For decades, these fields evolved independently, without interaction and synergy between them. This has changed profoundly with controlling the position of the equidistant frequency spikes of a mode-locked laser oscillator. By the self-referencing technique invented by Theodor Hänsch, the comb can be coherently linked to microwaves and used for precision measurements of energy differences between quantum states. The resultant optical frequency synthesis has revolutionized precision spectroscopy. Locking the comb lines to the resonator round-trip frequency by the same approach has given rise to laser pulses with controlled field oscillations. This article reviews, from a personal perspective, how the bridge between frequency- and time-resolved metrology emerged on the turn of the millennium and how synthesized several-cycle laser fields have been instrumental in establishing the basic tools and techniques for attosecond science.

Real-time spectral interferometry probes the internal dynamics of femtosecond soliton molecules

NASA Astrophysics Data System (ADS)

Herink, G.; Kurtz, F.; Jalali, B.; Solli, D. R.; Ropers, C.

2017-04-01

Solitons, particle-like excitations ubiquitous in many fields of physics, have been shown to exhibit bound states akin to molecules. The formation of such temporal soliton bound states and their internal dynamics have escaped direct experimental observation. By means of an emerging time-stretch technique, we resolve the evolution of femtosecond soliton molecules in the cavity of a few-cycle mode-locked laser. We track two- and three-soliton bound states over hundreds of thousands of consecutive cavity roundtrips, identifying fixed points and periodic and aperiodic molecular orbits. A class of trajectories acquires a path-dependent geometrical phase, implying that its dynamics may be topologically protected. These findings highlight the importance of real-time detection in resolving interactions in complex nonlinear systems, including the dynamics of soliton bound states, breathers, and rogue waves.

Saturable nonlinear dielectric waveguide with applications to broad-area semiconductor lasers.

PubMed

Mehuys, D; Mittelstein, M; Salzman, J; Yariv, A

1987-11-01

Self-focusing in a passive dielectric waveguide with a saturable nonlinearity is studied. The eigensolutions constitute a good approximation to the lateral modes of broad-area semiconductor lasers under low-duty-cycle pulsed conditions. The laser modes are predicted to consist of adjacent filaments coupled in phase, leading to a single-lobed far field, and to be stable with increased current injection above saturation intensity. The ultimate filament spacing is inversely proportional to the threshold gain, and thus wider filaments are expected in low-threshold broad-area lasers.

The Laser Cooling and Magneto-Optical Trapping of the YO Molecule

NASA Astrophysics Data System (ADS)

Yeo, Mark

Laser cooling and magneto-optical trapping of neutral atoms has revolutionized the field of atomic physics by providing an elegant and efficient method to produce cold dense samples of ultracold atoms. Molecules, with their strong anisotropic dipolar interaction promises to unlock even richer phenomenon. However, due to their additional vibrational and rotational degrees of freedom, laser cooling techniques have only been extended to a small set of diatomic molecules. In this thesis, we demonstrate the first magneto-optical trapping of a diatomic molecule using a quasi-cycling transition and an oscillating quadrupole magnetic field. The transverse temperature of a cryogenically produced YO beam was reduced from 25 mK to 10 mK via doppler cooling and further reduced to 2 mK with the addition of magneto-optical trapping forces. The optical cycling in YO is complicated by the presence of an intermediate electronic state, as decays through this state lead to optical pumping into dark rotational states. Thus, we also demonstrate the mixing of rotational states in the ground electronic state using microwave radiation. This technique greatly enhances optical cycling, leading to a factor of 4 increase in the YO beam fluorescence and is used in conjunction with a frequency modulated and chirped continuous wave laser to longitudinally slow the YO beam. We generate YO molecules below 10 m/s that are directly loadable into a three-dimensional magneto-optical trap. This mixing technique provides an alternative to maintaining rotational closure and should extend laser cooling to a larger set of molecules.

Photoassociation dynamics driven by a modulated two-color laser field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Wei; Zhao Zeyu; Xie Ting

2011-11-15

Photoassociation (PA) dynamics of ultracold cesium atoms steered by a modulated two-color laser field E(t)=E{sub 0}f(t)cos((2{pi}/T{sub p})-{phi})cos({omega}{sub L}t) is investigated theoretically by numerically solving the time-dependent Schroedinger equation. The PA dynamics is sensitive to the phase of envelope (POE) {phi} and the period of the envelope T{sub p}, which indicates that it can be controlled by varying POE {phi} and period T{sub p}. Moreover, we introduce the time- and frequency-resolved spectrum to illustrate how the POE {phi} and the period T{sub p} influence the intensity distribution of the modulated laser pulse and hence change the time-dependent population distribution of photoassociatedmore » molecules. When the Gaussian envelope contains a few oscillations, the PA efficiency is also dependent on POE {phi}. The modulated two-color laser field is available in the current experiment based on laser mode-lock technology.« less

Development of high-average-power DPSSL with high beam quality

NASA Astrophysics Data System (ADS)

Nakai, Sadao; Kanabe, Tadashi; Kawashima, Toshiyuki; Yamanaka, Masanobu; Izawa, Yasukazu; Nakatuka, Masahiro; Kandasamy, Ranganathan; Kan, Hirofumi; Hiruma, Teruo; Niino, Masayuki

2000-08-01

The recent progress of high power diode laser is opening new fields of laser and its application. We are developing high average power diode pumped solid state laser DPSSL for laser fusion power plant, for space propulsion and for various applications in industry. The common features or requirements of our High Average-power Laser for Nuclear-fusion Application (HALNA) are large pulse energy with relatively low repetition of few tens Hz, good beam quality of order of diffraction limit and high efficiency more than 10%. We constructed HALNA 10 (10J X 10 Hz) and tested the performance to clarify the scalability to higher power system. We have obtained in a preliminary experiment a 8.5 J output energy at 0.5 Hz with beam quality of 2 times diffraction limited far-field pattern.

Laser-driven strong magnetostatic fields with applications to charged beam transport and magnetized high energy-density physics

NASA Astrophysics Data System (ADS)

Santos, J. J.; Bailly-Grandvaux, M.; Ehret, M.; Arefiev, A. V.; Batani, D.; Beg, F. N.; Calisti, A.; Ferri, S.; Florido, R.; Forestier-Colleoni, P.; Fujioka, S.; Gigosos, M. A.; Giuffrida, L.; Gremillet, L.; Honrubia, J. J.; Kojima, S.; Korneev, Ph.; Law, K. F. F.; Marquès, J.-R.; Morace, A.; Mossé, C.; Peyrusse, O.; Rose, S.; Roth, M.; Sakata, S.; Schaumann, G.; Suzuki-Vidal, F.; Tikhonchuk, V. T.; Toncian, T.; Woolsey, N.; Zhang, Z.

2018-05-01

Powerful nanosecond laser-plasma processes are explored to generate discharge currents of a few 100 kA in coil targets, yielding magnetostatic fields (B-fields) in excess of 0.5 kT. The quasi-static currents are provided from hot electron ejection from the laser-irradiated surface. According to our model, which describes the evolution of the discharge current, the major control parameter is the laser irradiance Ilasλlas2 . The space-time evolution of the B-fields is experimentally characterized by high-frequency bandwidth B-dot probes and proton-deflectometry measurements. The magnetic pulses, of ns-scale, are long enough to magnetize secondary targets through resistive diffusion. We applied it in experiments of laser-generated relativistic electron transport through solid dielectric targets, yielding an unprecedented 5-fold enhancement of the energy-density flux at 60 μm depth, compared to unmagnetized transport conditions. These studies pave the ground for magnetized high-energy density physics investigations, related to laser-generated secondary sources of radiation and/or high-energy particles and their transport, to high-gain fusion energy schemes, and to laboratory astrophysics.

On the Acceleration and Transport of Electrons Generated by Intense Laser-Plasma Interactions at Sharp Interfaces

NASA Astrophysics Data System (ADS)

May, Joshua Joseph

The continued development of the chirped pulse amplification technique has allowed for the development of lasers with powers of in excess of 10 15W, for pulse lengths with durations of between .01 and 10 picoseconds, and which can be focused to energy densities greater than 100 giga-atmospheres. When such lasers are focused onto material targets, the possibility of creating particle beams with energy fluxes of comparable parameters arises. Such interactions have a number of theorized applications. For instance, in the Fast Ignition concept for Inertial Confinement Fusion [1], a high-intensity laser efficiently transfers its energy into an electron beam with an appropriate spectra which is then transported into a compressed target and initiate a fusion reaction. Another possible use is the so called Radiation Pressure Acceleration mechanism, in which a high-intensity, circularly polarized laser is used to create a mono-energetic ion beam which could then be used for medical imaging and treatment, among other applications. For this latter application, it is important that the laser energy is transferred to the ions and not to the electrons. However the physics of such high energy-density laser-matter interactions is highly kinetic and non-linear, and presently not fully understood. In this dissertation, we use the Particle-in-Cell code OSIRIS [2, 3] to explore the generation and transport of relativistic particle beams created by high intensity lasers focused onto solid density matter at normal incidence. To explore the generation of relativistic electrons by such interactions, we use primarily one-dimensional (1D) and two-dimensional (2D), and a few three-dimensional simulations (3D). We initially examine the idealized case of normal incidence of relatively short, plane-wave lasers on flat, sharp interfaces. We find that in 1D the results are highly dependent on the initial temperature of the plasma, with significant absorption into relativistic electrons only possible when the temperature is high in the direction parallel to the electric field of the laser. In multi-dimensions, absorption into relativistic electrons arises independent of the initial temperature for both fixed and mobile ions, although the absorption is higher for mobile ions. In most cases however, absorption remains at 100s of percent, and as such a standing wave structure from the incoming and reflected wave is setup in front of the plasma surface. The peak momentum of the accelerated electrons is found to be 2 a0mec, where a 0 = eA0/mec 2 is the normalized vector potential of the laser in vacuum, e is the electron charge, me is the electron mass, and c is the speed of light. We consider cases for which a0 > 1. We therefore call this the 2 a0 acceleration process. Using particle tracking, we identify the detailed physics behind the 2a0 process and find it is related to the standing wave structure of the fields. We observe that the particles which gain energy do so by interacting with the laser electric field within a quarter wavelength of the surface where it is at an anti-node (it is a node at the surface). We find that only particles with high initial momentum - in particular high transverse momentum - are able to navigate through the laser magnetic field as its magnitude decreases in time each half laser cycle (it is an anti-node at the surface) to penetrate a quarter wavelength into the vacuum where the laser electric field is large. For a circularly polarized laser the magnetic field amplitude never decreases at the surface, instead its direction simply rotates. This prevents electrons from leaving the plasma and they therefore cannot gain energy from the electric field. (Abstract shortened by ProQuest.).

Laser-induced asymmetric faceting and growth of a nano-protrusion on a tungsten tip

NASA Astrophysics Data System (ADS)

Yanagisawa, Hirofumi; Zadin, Vahur; Kunze, Karsten; Hafner, Christian; Aabloo, Alvo; Kim, Dong Eon; Kling, Matthias F.; Djurabekova, Flyura; Osterwalder, Jürg; Wuensch, Walter

2016-12-01

Irradiation of a sharp tungsten tip by a femtosecond laser and exposed to a strong DC electric field led to reproducible surface modifications. By a combination of field emission microscopy and scanning electron microscopy, we observed asymmetric surface faceting with sub-ten nanometer high steps. The presence of faceted features mainly on the laser-exposed side implies that the surface modification was driven by a laser-induced transient temperature rise on a scale of a couple of picoseconds in the tungsten tip apex. Moreover, we identified the formation of a nano-tip a few nanometers high located at one of the corners of a faceted plateau. The results of simulations emulating the experimental conditions are consistent with the experimental observations. The presented technique would be a new method to fabricate a nano-tip especially for generating coherent electron pulses. The features may also help to explain the origin of enhanced field emission, which leads to vacuum arcs, in high electric field devices such as radio-frequency particle accelerators.

Laser-driven strong magnetostatic fields with applications to charged beam transport and magnetized high energy-density physics

NASA Astrophysics Data System (ADS)

Santos, Joao

2017-10-01

Powerful laser-plasma processes are explored to generate discharge currents of a few 100 kA in coil targets, yielding magnetostatic fields (B-fields) in the kTesla range. The B-fields are measured by proton-deflectometry and high-frequency bandwidth B-dot probes. According to our modeling, the quasi-static currents are provided from hot electron ejection from the laser-irradiated surface, accounting for the space charge neutralization and the plasma magnetization. The major control parameter is the laser irradiance Iλ2 . The B-fields ns-scale is long enough to magnetize secondary targets through resistive diffusion. We applied it in experiments of laser-generated relativistic electron transport into solid dielectric targets, yielding an unprecedented enhancement of a factor 5 on the energy-density flux at 60 µm depth, compared to unmagnetized transport conditions. These studies pave the ground for magnetized high-energy density physics investigations, related to laser-generated secondary sources of radiation and/or high-energy particles and their transport, to high-gain fusion energy schemes and to laboratory astrophysics. We acknowledge funding from French National Agency for Research (ANR), Grant TERRE ANR-2011-BS04-014, and from EUROfusion Consortium, European Union's Horizon 2020 research and innovation programme, Grant 633053.

Editorial special issue on "Laser Doppler vibrometry"

NASA Astrophysics Data System (ADS)

Vanlanduit, Steve; Dirckx, Joris

2017-12-01

The invention of the laser in 1960 has opened up many opportunities in the field of measurement science and technology. Just a few years after the invention of the laser, a novel fluid flow measurement technique based on the Doppler effect was introduced: at that moment the laser Doppler anemometer or shortly LDA [1] was born. The technique enabled fluid velocity measurement by using the light of a He-Ne beam which was scattered by very small polystyrene spheres entrained in the fluid. Later on, in the late nineteen seventees it was recognized that the detection of the Doppler frequency shift that occurs when light is scattered by a moving surface can also be used to measure the vibration velocity of an object. The instrument to perform these vibration measurements was called the laser Doppler vibrometer or LDV [2]. In the last decades several technological advances were made in the field of laser Doppler vibrometry. The result is that nowadays, velocity measurements of fluids (using LDA) and vibrating objects (using LDV) are performed in many challenging applications in different fields (microelectronics, civil structures, biomedical engineering, material science, etc.).

Double optical gating of high-order harmonic generation with carrier-envelope phase stabilized lasers.

PubMed

Mashiko, Hiroki; Gilbertson, Steve; Li, Chengquan; Khan, Sabih D; Shakya, Mahendra M; Moon, Eric; Chang, Zenghu

2008-03-14

We demonstrated a novel optical switch to control the high-order harmonic generation process so that single attosecond pulses can be generated with multiple-cycle pulses. The technique combines two powerful optical gating methods: polarization gating and two-color gating. An extreme ultraviolet supercontinuum supporting 130 as was generated with neon gas using 9 fs laser pulses. We discovered a unique dependence of the harmonic spectra on the carrier-envelope phase of the laser fields, which repeats every 2 pi radians.

Double Optical Gating of High-Order Harmonic Generation with Carrier-Envelope Phase Stabilized Lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mashiko, Hiroki; Gilbertson, Steve; Li, Chengquan

2008-03-14

We demonstrated a novel optical switch to control the high-order harmonic generation process so that single attosecond pulses can be generated with multiple-cycle pulses. The technique combines two powerful optical gating methods: polarization gating and two-color gating. An extreme ultraviolet supercontinuum supporting 130 as was generated with neon gas using 9 fs laser pulses. We discovered a unique dependence of the harmonic spectra on the carrier-envelope phase of the laser fields, which repeats every 2{pi} radians.

Biomedical applications of laser spectroscopy

NASA Astrophysics Data System (ADS)

Svanberg, Sune

1999-07-01

Very soon after the invention of the laser, the use of the thermal effects of the radiation was introduced. Such techniques have been refined and the laser is now routinely used for treatment in many specialities. Photodynamic therapy (PDT) is a non-thermal modality employing the combination of a tumor-seeking agent and activating laser light. During the last 15 years laser spectroscopic techniques have also been developed providing powerful means for non-intrusive medical diagnostics of tissue in real time. At the beginning only few groups were involved in exploratory work, but successively the field has developed now to occupy a large number of research teams, which meet at large specialized conferences. We will here consider three aspects of laser diagnostics: fluorescence, Raman and near-IR, and elastic scattering spectroscopy, and we will also briefly discuss PDT. The activity in the field is very extensive, and rather than trying to give a full overview, illustrations from work performed at the Lund University Medical Laser Center will be given.

Maximizing energy deposition by shaping few-cycle laser pulses

NASA Astrophysics Data System (ADS)

Gateau, Julien; Patas, Alexander; Matthews, Mary; Hermelin, Sylvain; Lindinger, Albrecht; Kasparian, Jérôme; Wolf, Jean-Pierre

2018-07-01

We experimentally investigate the impact of pulse shape on the dynamics of laser-generated plasma in rare gases. Fast-rising triangular pulses with a slower decay lead to early ionization of the gas and depose energy more efficiently than their temporally reversed counterparts. As a result, in both argon and krypton, the induced shockwave as well as the plasma luminescence are stronger. This is due to an earlier availability of free electrons to undergo inverse Bremsstrahlung on the pulse trailing edge. Our results illustrate the ability of adequately tailored pulse shapes to optimize the energy deposition in gas plasmas.

Femtosecond few- to single-electron point-projection microscopy for nanoscale dynamic imaging

PubMed Central

Bainbridge, A. R.; Barlow Myers, C. W.; Bryan, W. A.

2016-01-01

Femtosecond electron microscopy produces real-space images of matter in a series of ultrafast snapshots. Pulses of electrons self-disperse under space-charge broadening, so without compression, the ideal operation mode is a single electron per pulse. Here, we demonstrate femtosecond single-electron point projection microscopy (fs-ePPM) in a laser-pump fs-e-probe configuration. The electrons have an energy of only 150 eV and take tens of picoseconds to propagate to the object under study. Nonetheless, we achieve a temporal resolution with a standard deviation of 114 fs (equivalent to a full-width at half-maximum of 269 ± 40 fs) combined with a spatial resolution of 100 nm, applied to a localized region of charge at the apex of a nanoscale metal tip induced by 30 fs 800 nm laser pulses at 50 kHz. These observations demonstrate real-space imaging of reversible processes, such as tracking charge distributions, is feasible whilst maintaining femtosecond resolution. Our findings could find application as a characterization method, which, depending on geometry, could resolve tens of femtoseconds and tens of nanometres. Dynamically imaging electric and magnetic fields and charge distributions on sub-micron length scales opens new avenues of ultrafast dynamics. Furthermore, through the use of active compression, such pulses are an ideal seed for few-femtosecond to attosecond imaging applications which will access sub-optical cycle processes in nanoplasmonics. PMID:27158637

Pulse sequences for efficient multi-cycle terahertz generation in periodically poled lithium niobate.

PubMed

Ravi, Koustuban; Schimpf, Damian N; Kärtner, Franz X

2016-10-31

The use of laser pulse sequences to drive the cascaded difference frequency generation of high energy, high peak-power and multi-cycle terahertz pulses in cryogenically cooled (100 K) periodically poled Lithium Niobate is proposed and studied. Detailed simulations considering the coupled nonlinear interaction of terahertz and optical waves (or pump depletion), show that unprecedented optical-to-terahertz energy conversion efficiencies > 5%, peak electric fields of hundred(s) of mega volts/meter at terahertz pulse durations of hundred(s) of picoseconds can be achieved. The proposed methods are shown to circumvent laser induced damage limitations at Joule-level pumping by 1µm lasers to enable multi-cycle terahertz sources with pulse energies > 10 milli-joules. Various pulse sequence formats are proposed and analyzed. Numerical calculations for periodically poled structures accounting for cascaded difference frequency generation, self-phase-modulation, cascaded second harmonic generation and laser induced damage are introduced. The physics governing terahertz generation using pulse sequences in this high conversion efficiency regime, limitations and practical considerations are discussed. It is shown that varying the poling period along the crystal length and further reduction of absorption can lead to even higher energy conversion efficiencies >10%. In addition to numerical calculations, an analytic formulation valid for arbitrary pulse formats and closed-form expressions for important cases are presented. Parameters optimizing conversion efficiency in the 0.1-1 THz range, the corresponding peak electric fields, crystal lengths and terahertz pulse properties are furnished.

Symmetry of Carrier-Envelope Phase Difference Effects in Strong-Field, Few-Cycle Ionization of Atoms and Molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martiny, Christian Per Juul; Madsen, Lars Bojer

2006-09-01

In few-cycle pulses, the exact value of the carrier-envelope phase difference (CEPD) has a pronounced influence on the ionization dynamics of atoms and molecules. We show that, for atoms in circularly polarized light, a change in the CEPD is mapped uniquely to an overall rotation of the system, and results for arbitrary CEPD are obtained by rotation of the results from a single calculation with fixed CEPD. For molecules, this is true only for linear molecules aligned parallel with the propagation direction of the field. The effects of CEPD are classified as geometric or nongeometric. The observations are exemplified bymore » strong-field calculations on hydrogen.« less

Sensitive frequency dependence of the carrier-envelope phase effect on bound-bound transitions: An interference perspective

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng Dian; Fu Panming; Wang Bingbing

2010-11-15

We investigate numerically with Hylleraas coordinates the frequency dependence of the carrier-envelope phase (CEP) effect on bound-bound transitions of helium induced by an ultrashort laser pulse of a few cycles. We find that the CEP effect is very sensitive to the carrier frequency of the laser pulse, occurring regularly even at far-off-resonance frequencies. By analyzing a two-level model, we find that the CEP effect can be attributed to the quantum interference between neighboring multiphoton transition pathways, which is made possible by the broadened spectrum of the ultrashort laser pulse. A general picture is developed along this line to understand themore » sensitivity of the CEP effect to the laser's carrier frequency. Multilevel influence on the CEP effect is also discussed.« less

An international review of laser Doppler vibrometry: Making light work of vibration measurement

NASA Astrophysics Data System (ADS)

Rothberg, S. J.; Allen, M. S.; Castellini, P.; Di Maio, D.; Dirckx, J. J. J.; Ewins, D. J.; Halkon, B. J.; Muyshondt, P.; Paone, N.; Ryan, T.; Steger, H.; Tomasini, E. P.; Vanlanduit, S.; Vignola, J. F.

2017-12-01

In 1964, just a few years after the invention of the laser, a fluid velocity measurement based on the frequency shift of scattered light was made and the laser Doppler technique was born. This comprehensive review paper charts advances in the development and applications of laser Doppler vibrometry (LDV) since those first pioneering experiments. Consideration is first given to the challenges that continue to be posed by laser speckle. Scanning LDV is introduced and its significant influence in the field of experimental modal analysis described. Applications in structural health monitoring and MEMS serve to demonstrate LDV's applicability on structures of all sizes. Rotor vibrations and hearing are explored as examples of the classic applications. Applications in acoustics recognise the versatility of LDV as demonstrated by visualisation of sound fields. The paper concludes with thoughts on future developments, using examples of new multi-component and multi-channel instruments.

Relativistic charged particle ejection from optical lattice

NASA Astrophysics Data System (ADS)

Frolov, E. N.; Dik, A. V.; Dabagov, S. B.

2018-03-01

We have analyzed relativistic (~ MeV) electron ejection from potential channels of standing laser wave taking into account both rapid and averaged oscillations within the region of declining field of standing wave. We show that only a few last rapid oscillations can define transverse speed and, therefore, angle at which a particle leaves standing wave. This conclusion might drastically simplify numerical simulations of charged particles channeling and accompanying radiation in crossed lasers field. Moreover, it might provide a valuable information for estimation of charged particle beams parameters after their interaction with finite standing wave.

FPGA based demodulation of laser induced fluorescence in plasmas

NASA Astrophysics Data System (ADS)

Mattingly, Sean W.; Skiff, Fred

2018-04-01

We present a field programmable gate array (FPGA)-based system that counts photons from laser-induced fluorescence (LIF) on a laboratory plasma. This is accomplished with FPGA-based up/down counters that demodulate the data, giving a background-subtracted LIF signal stream that is updated with a new point as each laser amplitude modulation cycle completes. We demonstrate using the FPGA to modulate a laser at 1 MHz and demodulate the resulting LIF data stream. This data stream is used to calculate an LIF-based measurement sampled at 1 MHz of a plasma ion fluctuation spectrum.

Optical nucleation of bubble clouds in a high pressure spherical resonator.

PubMed

Anderson, Phillip; Sampathkumar, A; Murray, Todd W; Gaitan, D Felipe; Glynn Holt, R

2011-11-01

An experimental setup for nucleating clouds of bubbles in a high-pressure spherical resonator is described. Using nanosecond laser pulses and multiple phase gratings, bubble clouds are optically nucleated in an acoustic field. Dynamics of the clouds are captured using a high-speed CCD camera. The images reveal cloud nucleation, growth, and collapse and the resulting emission of radially expanding shockwaves. These shockwaves are reflected at the interior surface of the resonator and then reconverge to the center of the resonator. As the shocks reconverge upon the center of the resonator, they renucleate and grow the bubble cloud. This process is repeated over many acoustic cycles and with each successive shock reconvergence, the bubble cloud becomes more organized and centralized so that subsequent collapses give rise to stronger, better defined shockwaves. After many acoustic cycles individual bubbles cannot be distinguished and the cloud is then referred to as a cluster. Sustainability of the process is ultimately limited by the detuning of the acoustic field inside the resonator. The nucleation parameter space is studied in terms of laser firing phase, laser energy, and acoustic power used.

High-resolution measurements of the spatial and temporal evolution of megagauss magnetic fields created in intense short-pulse laser-plasma interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatterjee, Gourab, E-mail: gourab@tifr.res.in; Singh, Prashant Kumar; Adak, Amitava

A pump-probe polarimetric technique is demonstrated, which provides a complete, temporally and spatially resolved mapping of the megagauss magnetic fields generated in intense short-pulse laser-plasma interactions. A normally incident time-delayed probe pulse reflected from its critical surface undergoes a change in its ellipticity according to the magneto-optic Cotton-Mouton effect due to the azimuthal nature of the ambient self-generated megagauss magnetic fields. The temporal resolution of the magnetic field mapping is typically of the order of the pulsewidth, limited by the laser intensity contrast, whereas a spatial resolution of a few μm is achieved by this optical technique. High-harmonics of themore » probe can be employed to penetrate deeper into the plasma to even near-solid densities. The spatial and temporal evolution of the megagauss magnetic fields at the target front as well as at the target rear are presented. The μm-scale resolution of the magnetic field mapping provides valuable information on the filamentary instabilities at the target front, whereas probing the target rear mirrors the highly complex fast electron transport in intense laser-plasma interactions.« less

Generation of Raman lasers from nitrogen molecular ions driven by ultraintense laser fields

NASA Astrophysics Data System (ADS)

Yao, Jinping; Chu, Wei; Liu, Zhaoxiang; Xu, Bo; Chen, Jinming; Cheng, Ya

2018-03-01

Atmospheric lasing has aroused much interest in the past few years. The ‘air–laser’ opens promising potential for remote chemical sensing of trace gases with high sensitivity and specificity. At present, several approaches have been successfully implemented for generating highly coherent laser beams in atmospheric condition, including both amplified-spontaneous emission, and narrow-bandwidth stimulated emission in the forward direction in the presence of self-generated or externally injected seed pulses. Here, we report on generation of multiple-wavelength Raman lasers from nitrogen molecular ions ({{{N}}}2+), driven by intense mid-infrared laser fields. Intuitively, the approach appears problematic for the small nonlinear susceptibility of {{{N}}}2+ ions, whereas the efficiency of Raman laser can be significantly promoted in near-resonant condition. More surprisingly, a Raman laser consisting of a supercontinuum spanning from ∼310 to ∼392 nm has been observed resulting from a series near-resonant nonlinear processes including four-wave mixing, stimulated Raman scattering and cross phase modulation. To date, extreme nonlinear optics in molecular ions remains largely unexplored, which provides an alternative means for air–laser-based remote sensing applications.

Enhanced relativistic harmonics by electron nanobunching

NASA Astrophysics Data System (ADS)

an der Brügge, D.; Pukhov, A.

2010-03-01

It is shown that when a few-cycle, relativistically intense, p-polarized laser pulse is obliquely incident on overdense plasma, the surface electrons may form ultrathin, highly compressed layers with a width of a few nanometers. These electron "nanobunches" emit synchrotron radiation coherently. We calculate the one-dimensional synchrotron spectrum analytically and obtain a slowly decaying power law with an exponent of 4/3 or 6/5. This is much flatter than the 8/3 power of the Baeva-Gordienko-Pukhov spectrum, produced by a relativistically oscillating bulk skin layer. The synchrotron spectrum cutoff frequency is defined either by the electron relativistic γ-factor or by the thickness of the emitting layer. In the numerically demonstrated, locally optimal case, the radiation is emitted in the form of a single attosecond pulse, which contains almost the entire energy of the full optical cycle.

Compact 200 kHz HHG source driven by a few-cycle OPCPA

NASA Astrophysics Data System (ADS)

Harth, Anne; Guo, Chen; Cheng, Yu-Chen; Losquin, Arthur; Miranda, Miguel; Mikaelsson, Sara; Heyl, Christoph M.; Prochnow, Oliver; Ahrens, Jan; Morgner, Uwe; L'Huillier, Anne; Arnold, Cord L.

2018-01-01

We present efficient high-order harmonic generation (HHG) based on a high-repetition rate, few-cycle, near infrared (NIR), carrier-envelope phase stable, optical parametric chirped pulse amplifier (OPCPA), emitting 6 fs pulses with 9 μJ pulse energy. In krypton, we reach conversion efficiencies from the NIR to the extreme ultraviolet (XUV) radiation pulse energy on the order of ˜10-6 with less than 3 μJ driving pulse energy. This is achieved by optimizing the OPCPA for a spatially and temporally clean pulse and by a specially designed high-pressure gas target. In the future, the high efficiency of the HHG source will be beneficial for high-repetition rate two-colour (NIR-XUV) pump-probe experiments, where the available pulse energy from the laser has to be distributed economically between pump and probe pulses.

Partially coherent isodiffracting pulsed beams

NASA Astrophysics Data System (ADS)

Koivurova, Matias; Ding, Chaoliang; Turunen, Jari; Pan, Liuzhan

2018-02-01

We investigate a class of isodiffracting pulsed beams, which are superpositions of transverse modes supported by spherical-mirror laser resonators. By employing modal weights that, for stationary light, produce a Gaussian Schell-model beam, we extend this standard model to pulsed beams. We first construct the two-frequency cross-spectral density function that characterizes the spatial coherence in the space-frequency domain. By assuming a power-exponential spectral profile, we then employ the generalized Wiener-Khintchine theorem for nonstationary light to derive the two-time mutual coherence function that describes the space-time coherence of the ensuing beams. The isodiffracting nature of the laser resonator modes permits all (paraxial-domain) calculations at any propagation distance to be performed analytically. Significant spatiotemporal coupling is revealed in subcycle, single-cycle, and few-cycle domains, where the partial spatial coherence also leads to reduced temporal coherence even though full spectral coherence is assumed.

Controlling electron quantum paths for generation of circularly polarized high-order harmonics by H2+ subject to tailored (ω , 2 ω ) counter-rotating laser fields

NASA Astrophysics Data System (ADS)

Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

2018-04-01

Recently, studies of high-order harmonics (HHG) from atoms driven by bichromatic counter-rotating circularly polarized laser fields as a source of coherent circularly polarized extreme ultraviolet (XUV) and soft-x-ray beams in a tabletop-scale setup have received considerable attention. Here, we demonstrate the ability to control the electron recollisions giving three returns per one cycle of the fundamental frequency ω by using tailored bichromatic (ω , 2 ω ) counter-rotating circularly polarized laser fields with a molecular target. The full control of the electronic pathway is first analyzed by a classical trajectory analysis and then extended to a detailed quantum study of H2+ molecules in bichromatic (ω , 2 ω ) counter-rotating circularly polarized laser fields. The radiation spectrum contains doublets of left- and right-circularly polarized harmonics in the XUV ranges. We study in detail the below-, near-, and above-threshold harmonic regions and describe how excited-state resonances alter the ellipticity and phase of the generated harmonic peaks.

Proposed Laser-driven, Dielectric Microstructure Few-cm Long Undulator for Attosecond Coherent X-rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plettner, T; Byer, R.L.; /Stanford U., Ginzton Lab.

This article presents the concept of an all-dielectric laser-driven undulator for the generation of coherent X-rays. The proposed laser-driven undulator is expected to produce internal deflection forces equivalent to a several-Tesla magnetic field acting on a speed-of-light particle. The key idea for this laser-driven undulator is its ability to provide phase synchronicity between the deflection force and the electron beam for a distance that is much greater than the laser wavelength. The potential advantage of this undulator is illustrated with a possible design example that assumes a small laser accelerator which delivers a 2 GeV, 1 pC, 1 kHz electronmore » bunch train to a 10 cm long, 1/2 mm period laser-driven undulator. Such an undulator could produce coherent X-ray pulses with {approx}10{sup 9} photons of 64 keV energy. The numerical modeling for the expected X-ray pulse shape was performed with GENESIS, which predicts X-ray pulse durations in the few-attosecond range. Possible applications for nonlinear electromagnetic effects from these X-ray pulses are briefly discussed.« less

High-Energy Vacuum Birefringence and Dichroism in an Ultrastrong Laser Field

NASA Astrophysics Data System (ADS)

Bragin, Sergey; Meuren, Sebastian; Keitel, Christoph H.; Di Piazza, Antonino

2017-12-01

A long-standing prediction of quantum electrodynamics, yet to be experimentally observed, is the interaction between real photons in vacuum. As a consequence of this interaction, the vacuum is expected to become birefringent and dichroic if a strong laser field polarizes its virtual particle-antiparticle dipoles. Here, we derive how a generally polarized probe photon beam is influenced by both vacuum birefringence and dichroism in a strong linearly polarized plane-wave laser field. Furthermore, we consider an experimental scheme to measure these effects in the nonperturbative high-energy regime, where the Euler-Heisenberg approximation breaks down. By employing circularly polarized high-energy probe photons, as opposed to the conventionally considered linearly polarized ones, the feasibility of quantitatively confirming the prediction of nonlinear QED for vacuum birefringence at the 5 σ confidence level on the time scale of a few days is demonstrated for upcoming 10 PW laser systems. Finally, dichroism and anomalous dispersion in vacuum are shown to be accessible at these facilities.

Attosecond nanoscale near-field sampling

DOE PAGES

Forg, B.; Schotz, J.; SuBmann, F.; ...

2016-05-31

The promise of ultrafast light-field-driven electronic nanocircuits has stimulated the development of the new research field of attosecond nanophysics. An essential prerequisite for advancing this new area is the ability to characterize optical near fields from light interaction with nanostructures, with sub-cycle resolution. Here we experimentally demonstrate attosecond near-field retrieval for a tapered gold nanowire. Furthermore, by comparison of the results to those obtained from noble gas experiments and trajectory simulations, the spectral response of the nanotaper near field arising from laser excitation can be extracted.

Light-field-driven currents in graphene

NASA Astrophysics Data System (ADS)

Higuchi, Takuya; Heide, Christian; Ullmann, Konrad; Weber, Heiko B.; Hommelhoff, Peter

2017-10-01

The ability to steer electrons using the strong electromagnetic field of light has opened up the possibility of controlling electron dynamics on the sub-femtosecond (less than 10-15 seconds) timescale. In dielectrics and semiconductors, various light-field-driven effects have been explored, including high-harmonic generation, sub-optical-cycle interband population transfer and the non-perturbative change of the transient polarizability. In contrast, much less is known about light-field-driven electron dynamics in narrow-bandgap systems or in conductors, in which screening due to free carriers or light absorption hinders the application of strong optical fields. Graphene is a promising platform with which to achieve light-field-driven control of electrons in a conducting material, because of its broadband and ultrafast optical response, weak screening and high damage threshold. Here we show that a current induced in monolayer graphene by two-cycle laser pulses is sensitive to the electric-field waveform, that is, to the exact shape of the optical carrier field of the pulse, which is controlled by the carrier-envelope phase, with a precision on the attosecond (10-18 seconds) timescale. Such a current, dependent on the carrier-envelope phase, shows a striking reversal of the direction of the current as a function of the driving field amplitude at about two volts per nanometre. This reversal indicates a transition of light-matter interaction from the weak-field (photon-driven) regime to the strong-field (light-field-driven) regime, where the intraband dynamics influence interband transitions. We show that in this strong-field regime the electron dynamics are governed by sub-optical-cycle Landau-Zener-Stückelberg interference, composed of coherent repeated Landau-Zener transitions on the femtosecond timescale. Furthermore, the influence of this sub-optical-cycle interference can be controlled with the laser polarization state. These coherent electron dynamics in graphene take place on a hitherto unexplored timescale, faster than electron-electron scattering (tens of femtoseconds) and electron-phonon scattering (hundreds of femtoseconds). We expect these results to have direct ramifications for band-structure tomography and light-field-driven petahertz electronics.

Light-field-driven currents in graphene.

PubMed

Higuchi, Takuya; Heide, Christian; Ullmann, Konrad; Weber, Heiko B; Hommelhoff, Peter

2017-10-12

The ability to steer electrons using the strong electromagnetic field of light has opened up the possibility of controlling electron dynamics on the sub-femtosecond (less than 10 -15 seconds) timescale. In dielectrics and semiconductors, various light-field-driven effects have been explored, including high-harmonic generation, sub-optical-cycle interband population transfer and the non-perturbative change of the transient polarizability. In contrast, much less is known about light-field-driven electron dynamics in narrow-bandgap systems or in conductors, in which screening due to free carriers or light absorption hinders the application of strong optical fields. Graphene is a promising platform with which to achieve light-field-driven control of electrons in a conducting material, because of its broadband and ultrafast optical response, weak screening and high damage threshold. Here we show that a current induced in monolayer graphene by two-cycle laser pulses is sensitive to the electric-field waveform, that is, to the exact shape of the optical carrier field of the pulse, which is controlled by the carrier-envelope phase, with a precision on the attosecond (10 -18 seconds) timescale. Such a current, dependent on the carrier-envelope phase, shows a striking reversal of the direction of the current as a function of the driving field amplitude at about two volts per nanometre. This reversal indicates a transition of light-matter interaction from the weak-field (photon-driven) regime to the strong-field (light-field-driven) regime, where the intraband dynamics influence interband transitions. We show that in this strong-field regime the electron dynamics are governed by sub-optical-cycle Landau-Zener-Stückelberg interference, composed of coherent repeated Landau-Zener transitions on the femtosecond timescale. Furthermore, the influence of this sub-optical-cycle interference can be controlled with the laser polarization state. These coherent electron dynamics in graphene take place on a hitherto unexplored timescale, faster than electron-electron scattering (tens of femtoseconds) and electron-phonon scattering (hundreds of femtoseconds). We expect these results to have direct ramifications for band-structure tomography and light-field-driven petahertz electronics.

The Role of the CO2 Laser and Fractional CO2 Laser in Dermatology

PubMed Central

Omi, Tokuya; Numano, Kayoko

2014-01-01

Background: Tremendous advances have been made in the medical application of the laser in the past few decades. Many diseases in the dermatological field are now indications for laser treatment that qualify for reimbursement by many national health insurance systems. Among laser types, the carbon dioxide (CO2) laser remains an important system for the dermatologist. Rationale: The lasers used in photosurgery have wavelengths that differ according to their intended use and are of various types, but the CO2 laser is one of the most widely used lasers in the dermatology field. With its wavelength in the mid-infrared at 10,600 nm, CO2 laser energy is wellabsorbed in water. As skin contains a very high water percentage, this makes the CO2 laser ideal for precise, safe ablation with good hemostasis. In addition to its efficacy in ablating benign raised lesions, the CO2 laser has been reported to be effective in the field of esthetic dermatology in the revision of acne scars as well as in photorejuvenation. With the addition of fractionation of the beam of energy into myriad microbeams, the fractional CO2 laser has offered a bridge between the frankly full ablative indications and the nonablative skin rejuvenation systems of the 2000s in the rejuvenation of photoaged skin on and off the face. Conclusions: The CO2 laser remains an efficient, precise and safe system for the dermatologist. Technological advances in CO2 laser construction have meant smaller spot sizes and greater precision for laser surgery, and more flexibility in tip sizes and protocols for fractional CO2 laser treatment. The range of dermatological applications of the CO2 laser is expected to continue to increase in the future. PMID:24771971

The Role of the CO2 Laser and Fractional CO2 Laser in Dermatology.

PubMed

Omi, Tokuya; Numano, Kayoko

2014-03-27

Tremendous advances have been made in the medical application of the laser in the past few decades. Many diseases in the dermatological field are now indications for laser treatment that qualify for reimbursement by many national health insurance systems. Among laser types, the carbon dioxide (CO2) laser remains an important system for the dermatologist. The lasers used in photosurgery have wavelengths that differ according to their intended use and are of various types, but the CO2 laser is one of the most widely used lasers in the dermatology field. With its wavelength in the mid-infrared at 10,600 nm, CO2 laser energy is wellabsorbed in water. As skin contains a very high water percentage, this makes the CO2 laser ideal for precise, safe ablation with good hemostasis. In addition to its efficacy in ablating benign raised lesions, the CO2 laser has been reported to be effective in the field of esthetic dermatology in the revision of acne scars as well as in photorejuvenation. With the addition of fractionation of the beam of energy into myriad microbeams, the fractional CO2 laser has offered a bridge between the frankly full ablative indications and the nonablative skin rejuvenation systems of the 2000s in the rejuvenation of photoaged skin on and off the face. The CO2 laser remains an efficient, precise and safe system for the dermatologist. Technological advances in CO2 laser construction have meant smaller spot sizes and greater precision for laser surgery, and more flexibility in tip sizes and protocols for fractional CO2 laser treatment. The range of dermatological applications of the CO2 laser is expected to continue to increase in the future.

High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter

PubMed Central

Green, B.; Kovalev, S.; Asgekar, V.; Geloni, G.; Lehnert, U.; Golz, T.; Kuntzsch, M.; Bauer, C.; Hauser, J.; Voigtlaender, J.; Wustmann, B.; Koesterke, I.; Schwarz, M.; Freitag, M.; Arnold, A.; Teichert, J.; Justus, M.; Seidel, W.; Ilgner, C.; Awari, N.; Nicoletti, D.; Kaiser, S.; Laplace, Y.; Rajasekaran, S.; Zhang, L.; Winnerl, S.; Schneider, H.; Schay, G.; Lorincz, I.; Rauscher, A. A.; Radu, I.; Mährlein, S.; Kim, T. H.; Lee, J. S.; Kampfrath, T.; Wall, S.; Heberle, J.; Malnasi-Csizmadia, A.; Steiger, A.; Müller, A. S.; Helm, M.; Schramm, U.; Cowan, T.; Michel, P.; Cavalleri, A.; Fisher, A. S.; Stojanovic, N.; Gensch, M.

2016-01-01

Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. We benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution. PMID:26924651

High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter

DOE PAGES

Green, B.; Kovalev, S.; Asgekar, V.; ...

2016-02-29

Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields andmore » the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. In conclusion, we benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution.« less

Effects of the Carrier-Envelope Phase in the Multiphoton Ionization Regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakajima, Takashi; Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581; Watanabe, Shuntaro

2006-06-02

We theoretically investigate the effects of the carrier-envelope phase of few-cycle laser pulses in the multiphoton ionization regime. For atoms with low ionization potential, total ionization yield barely exhibits phase dependence, as expected. However, population of some bound states clearly shows phase dependence. This implies that the measurement of the carrier-envelope phase would be possible through the photoemission between bound states without energy-and-angle-resolved photoelectron detection. The considered scheme could be particularly useful to measure the carrier-envelope phase for a light source without an amplifier, such as a laser oscillator, which cannot provide sufficient pulse energy to induce tunneling ionization.

Surface morphology correlated with field emission properties of laser irradiated nickel

NASA Astrophysics Data System (ADS)

Jalil, S. A.; Bashir, S.; Akram, M.; Ahmed, Q. S.; Haq, F. U.

2017-08-01

The effect of laser fluence on the surface morphology and field emission properties of nickel (Ni) has been investigated. Circular shaped Ni targets are irradiated with Nd:YAG laser (1064 nm, 10 Hz, 10 ns) at various fluences ranging from 5.2 to 26 J/cm2 in air. For low fluence ranging from 5.2 to 10.4 J/cm2, SEM analysis reveals the growth of unorganized channels, grains, droplets, and ridges. Whereas, at moderate fluence of 15.6 J/cm2, the formation of ridges and cones along with few number of holes are observed. However, at high fluence regime ranging from 20 to 26 J/cm2, a sharp transition in morphology from ridges to holes has been observed. The laser structured Ni targets are also investigated for field emission properties by recording their I-V characteristics and Fowler-Nordheim (F-N) plots. The enhancement in field emission factor (β) and the reduction in turn on field are found to be dependent upon the laser fluence and morphology of the grown structures. For samples treated at low and moderate fluences, the growth of cones, channels and ridges is responsible for enhancement of β factor ranging from 121 to 178. Whereas, for samples treated at high fluence region, the formation of pores and holes is responsible for significant field convergence and consequently resulting in substantial enhancement in β factor to 276.

Generation of µW level plateau harmonics at high repetition rate.

PubMed

Hädrich, S; Krebs, M; Rothhardt, J; Carstens, H; Demmler, S; Limpert, J; Tünnermann, A

2011-09-26

The process of high harmonic generation allows for coherent transfer of infrared laser light to the extreme ultraviolet spectral range opening a variety of applications. The low conversion efficiency of this process calls for optimization or higher repetition rate intense ultrashort pulse lasers. Here we present state-of-the-art fiber laser systems for the generation of high harmonics up to 1 MHz repetition rate. We perform measurements of the average power with a calibrated spectrometer and achieved µW harmonics between 45 nm and 61 nm (H23-H17) at a repetition rate of 50 kHz. Additionally, we show the potential for few-cycle pulses at high average power and repetition rate that may enable water-window harmonics at unprecedented repetition rate. © 2011 Optical Society of America

Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments

NASA Astrophysics Data System (ADS)

Théberge, Francis; Daigle, Jean-François; Kieffer, Jean-Claude; Vidal, François; Châteauneuf, Marc

2017-01-01

Recent works on plasma channels produced during the propagation of ultrashort and intense laser pulses in air demonstrated the guiding of electric discharges along the laser path. However, the short plasma lifetime limits the length of the laser-guided discharge. In this paper, the conductivity and lifetime of long plasma channels produced by ultrashort laser pulses is enhanced efficiently over many orders of magnitude by the electric field of a hybrid AC-DC high-voltage source. The AC electric pulse from a Tesla coil allowed to stimulate and maintain the highly conductive channel during few milliseconds in order to guide a subsequent 500 times more energetic discharge from a 30-kV DC source. This DC discharge was laser-guided over an air gap length of two metres, which is more than two orders of magnitude longer than the expected natural discharge length. Long plasma channel induced by laser pulses and stimulated by an external high-voltage source opens the way for wireless and efficient transportation of energetic current pulses over long air gaps and potentially for guiding lightning.

Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments

PubMed Central

Théberge, Francis; Daigle, Jean-François; Kieffer, Jean-Claude; Vidal, François; Châteauneuf , Marc

2017-01-01

Recent works on plasma channels produced during the propagation of ultrashort and intense laser pulses in air demonstrated the guiding of electric discharges along the laser path. However, the short plasma lifetime limits the length of the laser-guided discharge. In this paper, the conductivity and lifetime of long plasma channels produced by ultrashort laser pulses is enhanced efficiently over many orders of magnitude by the electric field of a hybrid AC-DC high-voltage source. The AC electric pulse from a Tesla coil allowed to stimulate and maintain the highly conductive channel during few milliseconds in order to guide a subsequent 500 times more energetic discharge from a 30-kV DC source. This DC discharge was laser-guided over an air gap length of two metres, which is more than two orders of magnitude longer than the expected natural discharge length. Long plasma channel induced by laser pulses and stimulated by an external high-voltage source opens the way for wireless and efficient transportation of energetic current pulses over long air gaps and potentially for guiding lightning. PMID:28053312

Bound-Electron Nonlinearity Beyond the Ionization Threshold.

PubMed

Wahlstrand, J K; Zahedpour, S; Bahl, A; Kolesik, M; Milchberg, H M

2018-05-04

We present absolute space- and time-resolved measurements of the ultrafast laser-driven nonlinear polarizability in argon, krypton, xenon, nitrogen, and oxygen up to ionization fractions of a few percent. These measurements enable determination of the strongly nonperturbative bound-electron nonlinear polarizability well beyond the ionization threshold, where it is found to remain approximately quadratic in the laser field, a result normally expected at much lower intensities where perturbation theory applies.

Bound-Electron Nonlinearity Beyond the Ionization Threshold

NASA Astrophysics Data System (ADS)

Wahlstrand, J. K.; Zahedpour, S.; Bahl, A.; Kolesik, M.; Milchberg, H. M.

2018-05-01

We present absolute space- and time-resolved measurements of the ultrafast laser-driven nonlinear polarizability in argon, krypton, xenon, nitrogen, and oxygen up to ionization fractions of a few percent. These measurements enable determination of the strongly nonperturbative bound-electron nonlinear polarizability well beyond the ionization threshold, where it is found to remain approximately quadratic in the laser field, a result normally expected at much lower intensities where perturbation theory applies.

Lasers for Frontier Spectroscopy

NASA Astrophysics Data System (ADS)

Baldacchini, Giuseppe

The first laser has been invented in 1960 by using the red light from a ruby crystal, and since then the laser field exploded almost exponentially, and thousands of different materials, in the state of solids, liquids, vapors, gases, plasmas, and elementary particles have lased up to now from less than I Å to more than 1 mm. Many of them have been used with outstanding results both in basic science, and in industrial and commercial applications, by changing for ever the same lifestyle of humankind. As far as spectroscopy is concerned, the laser light has started an unprecedented revolution because of its unique properties as monochromaticity, coherence, power, brightness and short-pulse regime, unrivaled by any other natural and artificial light source. Spectroscopy applications increased qualitatively and quantitatively with the laser sources themselves, and they are still proceeding in parallel with the moving of the laser field towards new territories. Apart the opening up of new regions of the electromagnetic spectrum, like the terahertz gap, and the outstanding increase of the output power which is giving rise to completely new spectroscopic effects, the improvement of laser sources and auxiliary equipment is producing a growth of traditional laser spectroscopy with superior resolution and sensitivity. Moreover, spectroscopic techniques and laser light contributed to the development of new chemical and physical processes which have been used to fabricate photonic materials with new spectroscopic properties enriching the laser field itself, in a virtuous cycle spectroscopy→aser→material and back to spectroscopy with no end in sight.

Atmospheric methane measurement instrument using a Zeeman-split He-Ne laser

NASA Technical Reports Server (NTRS)

Mcmanus, J. Barry; Kebabian, Paul L.; Kolb, Charles E.

1989-01-01

The construction of an atmospheric methane measurement instrument based on a Zeeman-split IR He-Ne laser is reported. The laser has a tranverse magnetic field over about 2/3 of its gain length and can oscillate at an (unsplit) frequency (2947.91/cm) centered on a methane absorption line, or on either of two frequencies split by + or - 0.055/cm from the center, with low CH4 absorption. The laser is tuned to dwell sequentially at each frequency, giving two differential absorption measurements in each 46-ms tuning cycle. Atmospheric measurements are made using two multiple pass absorption cells, one with fast (0.75-s) and one with slow (5-s) flow response times. Fluctuations in ambient CH4 of about 20-ppb (rms, 1-s averaging) are detected, with interference fringe effects the dominant noise source. The instrument has operated in a field experiment (NASA GTE/ABLE-3A) in Alaska.

Dramatic enhancement of supercontinuum generation in elliptically-polarized laser filaments

PubMed Central

Rostami, Shermineh; Chini, Michael; Lim, Khan; Palastro, John P.; Durand, Magali; Diels, Jean-Claude; Arissian, Ladan; Baudelet, Matthieu; Richardson, Martin

2016-01-01

Broadband laser sources based on supercontinuum generation in femtosecond laser filamentation have enabled applications from stand-off sensing and spectroscopy to the generation and self-compression of high-energy few-cycle pulses. Filamentation relies on the dynamic balance between self-focusing and plasma defocusing – mediated by the Kerr nonlinearity and multiphoton or tunnel ionization, respectively. The filament properties, including the supercontinuum generation, are therefore highly sensitive to the properties of both the laser source and the propagation medium. Here, we report the anomalous spectral broadening of the supercontinuum for filamentation in molecular gases, which is observed for specific elliptical polarization states of the input laser pulse. The resulting spectrum is accompanied by a modification of the supercontinuum polarization state and a lengthening of the filament plasma column. Our experimental results and accompanying simulations suggest that rotational dynamics of diatomic molecules play an essential role in filamentation-induced supercontinuum generation, which can be controlled with polarization ellipticity. PMID:26847427

Optical spectroscopy using gas-phase femtosecond laser filamentation.

PubMed

Odhner, Johanan; Levis, Robert

2014-01-01

Femtosecond laser filamentation occurs as a dynamic balance between the self-focusing and plasma defocusing of a laser pulse to produce ultrashort radiation as brief as a few optical cycles. This unique source has many properties that make it attractive as a nonlinear optical tool for spectroscopy, such as propagation at high intensities over extended distances, self-shortening, white-light generation, and the formation of an underdense plasma. The plasma channel that constitutes a single filament and whose position in space can be controlled by its input parameters can span meters-long distances, whereas multifilamentation of a laser beam can be sustained up to hundreds of meters in the atmosphere. In this review, we briefly summarize the current understanding and use of laser filaments for spectroscopic investigations of molecules. A theoretical framework of filamentation is presented, along with recent experimental evidence supporting the established understanding of filamentation. Investigations carried out on vibrational and rotational spectroscopy, filament-induced breakdown, fluorescence spectroscopy, and backward lasing are discussed.

Strong sub-terahertz surface waves generated on a metal wire by high-intensity laser pulses

PubMed Central

Tokita, Shigeki; Sakabe, Shuji; Nagashima, Takeshi; Hashida, Masaki; Inoue, Shunsuke

2015-01-01

Terahertz pulses trapped as surface waves on a wire waveguide can be flexibly transmitted and focused to sub-wavelength dimensions by using, for example, a tapered tip. This is particularly useful for applications that require high-field pulses. However, the generation of strong terahertz surface waves on a wire waveguide remains a challenge. Here, ultrafast field propagation along a metal wire driven by a femtosecond laser pulse with an intensity of 1018 W/cm2 is characterized by femtosecond electron deflectometry. From experimental and numerical results, we conclude that the field propagating at the speed of light is a half-cycle transverse-magnetic surface wave excited on the wire and a considerable portion of the kinetic energy of laser-produced fast electrons can be transferred to the sub-surface wave. The peak electric field strength of the surface wave and the pulse duration are estimated to be 200 MV/m and 7 ps, respectively. PMID:25652694

Crack-free conditions in welding of glass by ultrashort laser pulse.

PubMed

Miyamoto, Isamu; Cvecek, Kristian; Schmidt, Michael

2013-06-17

The spatial distribution of the laser energy absorbed by nonlinear absorption process in bulk glass w(z) is determined and thermal cycles due to the successive ultrashort laser pulse (USLP) is simulated using w(z) based on the transient thermal conduction model. The thermal stress produced in internal melting of bulk glass by USLP is qualitatively analyzed based on a simple thermal stress model, and crack-free conditions are studied in glass having large coefficient of thermal expansion. In heating process, cracks are prevented when the laser pulse impinges into glass with temperatures higher than the softening temperature of glass. In cooling process, shrinkage stress is suppressed to prevent cracks, because the embedded molten pool produced by nonlinear absorption process behaves like an elastic body under the compressive stress field unlike the case of CW-laser welding where the molten pool having a free surface produced by linear absorption process is plastically deformed under the compressive stress field.

Attosecond Pulse Carrier-Envelope Phase Effects: Roles of Frequency, Intensity and an Additional IR Pulse

NASA Astrophysics Data System (ADS)

Pronin, Evgeny A.; Peng, Liang-You; Starace, Anthony F.

2008-05-01

The effects of the carrier-envelope phase (CEP) of a few-cycle attosecond pulse on ionized electron momentum and energy spectra are analyzed, both with and without an additional few-cycle IR pulse [1, 2]. In the absence of an IR pulse, the CEP-induced asymmetries in the ionized electron momentum distributions are shown to vary as the 3/2 power of the attosecond pulse intensity. These asymmetries are also found to satisfy an approximate scaling law involving the frequency and intensity of the attosecond pulse. In the presence of even a very weak IR pulse, the attosecond pulse CEP-induced asymmetries are found to be significantly augmented. In addition, for higher IR laser intensities, we observe for low electron energies peaks separated by the IR photon energy in one electron momentum direction along the laser polarization axis; in the opposite direction, we find structured peaks that are spaced by twice the IR photon energy. Possible physical mechanisms for such asymmetric, low-energy structures in the ionized electron momentum distribution are proposed. Our results are based on single-active-electron solutions of the 3D TDSE for H and He. [1] Peng LY, Pronin EA, and Starace AF, New J. Phys. 10, xxx (2008); [2] Peng LY, Starace AF, Phys. Rev. A 76, 043401 (2007)

Noncollinear wave mixing of attosecond XUV and few-cycle optical laser pulses in gas-phase atoms: Toward multidimensional spectroscopy involving XUV excitations

NASA Astrophysics Data System (ADS)

Cao, Wei; Warrick, Erika R.; Fidler, Ashley; Neumark, Daniel M.; Leone, Stephen R.

2016-11-01

Ultrafast nonlinear spectroscopy, which records transient wave-mixing signals in a medium, is a powerful tool to access microscopic information using light sources in the radio-frequency and optical regimes. The extension of this technique towards the extreme ultraviolet (XUV) or even x-ray regimes holds the promise to uncover rich structural or dynamical information with even higher spatial or temporal resolution. Here, we demonstrate noncollinear wave mixing between weak XUV attosecond pulses and a strong near-infrared (NIR) few-cycle laser pulse in gas phase atoms (one photon of XUV and two photons of NIR). In the noncollinear geometry the attosecond and either one or two NIR pulses interact with argon atoms. Nonlinear XUV signals are generated in a spatially resolved fashion as required by phase matching. Different transition pathways can be identified from these background-free nonlinear signals according to the specific phase-matching conditions. Time-resolved measurements of the spatially gated XUV signals reveal electronic coherences of Rydberg wave packets prepared by a single XUV photon or XUV-NIR two-photon excitation, depending on the applied pulse sequences. These measurements open possible applications of tabletop multidimensional spectroscopy to the study of dynamics associated with valence or core excitation with XUV photons.

Effect of laser parameters on the microstructure of bonding porcelain layer fused on titanium

NASA Astrophysics Data System (ADS)

Chen, Xiaoyuan; Guo, Litong; Liu, Xuemei; Feng, Wei; Li, Baoe; Tao, Xueyu; Qiang, Yinghuai

2017-09-01

Bonding porcelain layer was fused on Ti surface by laser cladding process using a 400 W pulse CO2 laser. The specimens were studied by field-emission scanning electron microscopy, X-ray diffraction and bonding tests. During the laser fusion process, the porcelain powders were heated by laser energy and melted on Ti to form a chemical bond with the substrate. When the laser scanning speed decreased, the sintering temperature and the extent of the oxidation of Ti surface increased accordingly. When the laser scanning speed is 12.5 mm/s, the bonding porcelain layers were still incomplete sintered and there were some micro-cracks in the porcelain. When the laser scanning speed decreased to 7.5 mm/s, vitrified bonding porcelain layers with few pores were synthesized on Ti.

Quantum and semiclassical physics behind ultrafast optical nonlinearity in the midinfrared: the role of ionization dynamics within the field half cycle.

PubMed

Serebryannikov, E E; Zheltikov, A M

2014-07-25

Ultrafast ionization dynamics within the field half cycle is shown to be the key physical factor that controls the properties of optical nonlinearity as a function of the carrier wavelength and intensity of a driving laser field. The Schrödinger-equation analysis of a generic hydrogen quantum system reveals universal tendencies in the wavelength dependence of optical nonlinearity, shedding light on unusual properties of optical nonlinearities in the midinfrared. For high-intensity low-frequency fields, free-state electrons are shown to dominate over bound electrons in the overall nonlinear response of a quantum system. In this regime, semiclassical models are shown to offer useful insights into the physics behind optical nonlinearity.

Water-cooled hard-soldered kilowatt laser diode arrays operating at high duty cycle

NASA Astrophysics Data System (ADS)

Klumel, Genady; Karni, Yoram; Oppenhaim, Jacob; Berk, Yuri; Shamay, Moshe; Tessler, Renana; Cohen, Shalom; Risemberg, Shlomo

2010-04-01

High brightness laser diode arrays are increasingly found in defense applications either as efficient optical pumps or as direct energy sources. In many instances, duty cycles of 10- 20 % are required, together with precise optical collimation. System requirements are not always compatible with the use of microchannel based cooling, notwithstanding their remarkable efficiency. Simpler but effective solutions, which will not involve high fluid pressure drops as well as deionized water, are needed. The designer is faced with a number of challenges: effective heat removal, minimization of the built- in and operational stresses as well as precise and accurate fast axis collimation. In this article, we report on a novel laser diode array which includes an integral tap water cooling system. Robustness is achieved by all around hard solder bonding of passivated 940nm laser bars. Far field mapping of the beam, after accurate fast axis collimation will be presented. It will be shown that the design of water cooling channels , proper selection of package materials, careful design of fatigue sensitive parts and active collimation technique allow for long life time and reliability, while not compromising the laser diode array efficiency, optical power density ,brightness and compactness. Main performance characteristics are 150W/bar peak optical power, 10% duty cycle and more than 50% wall plug efficiency with less than 1° fast axis divergence. Lifetime of 0.5 Gshots with less than 10% power degradation has been proved. Additionally, the devices have successfully survived harsh environmental conditions such as thermal cycling of the coolant temperature and mechanical shocks.

Dunes and microdunes on Venus: Why were so few found in the Magellan data?

NASA Technical Reports Server (NTRS)

Weitz, Catherine M.; Plaut, Jeffrey J.; Greeley, Ronald; Saunders, R. Steven

1994-01-01

A search through cycle 1, 2, and 3 Magellan radar data covering 98% of the surface of Venus revealed very few dunes. Only two possible dune fields and several areas that may contain microdunes smaller than the resolution of the images (75 m) were identified. The Aglaonice dune field was identified in the cycle 1 images by the specular returns characteristic of dune faces oriented perpendicular to the radar illumination. Cycle 1 and 2 data of the Fortuna-Meshkenet dune field indicate that there has been no noticeable movement of the dunes over an 8-month period. The dunes, which are oriented both parallel and perpendicular to the radar illumination, appear to be dark features on a brighter substrate. Bright and dark patches that were visible in either cycle 1 or 2 data, but not both, allowed identification of several regions in the southern part of Venus that may contain microdunes. The microdunes are associated with several parabolic crater deposits in the region and are probably similar to those formed in wind tunnel experiments under Venus-like conditions. Bragg scattering and/or subpixel relfections from the near-normal face on asymmetric microdunes may account for these bright and dark patches. Look-angle effects and the lack of sufficient sand-size particles seem to be most likely reasons so few dunes were identified in Magellan data. Insufficient wind speeds, thinness of sand cover, and difficulty in identifying isolated dunes may also be contributors to the scarcity of dunes.

Dunes and Microdunes on Venus: Why Were So Few Found in the Magellan Data?

NASA Technical Reports Server (NTRS)

Weitz, Catherine M.; Plaut, Jeffrey J.; Greeley, Ronald; Saunders, R. Steven

1994-01-01

A search through cycle 1, 2, and 3 Magellan radar data covering 98% of the surface of Venus revealed very few dunes. Only two possible dune fields and several areas that may contain microdunes smaller than the resolution of the images (75 m) were identified. The Aglaonice dune field was identified in the cycle I images by the specular returns characteristic of dune faces oriented perpendicular to the radar illumination. Cycle 1 and 2 data of the Fortuna-Meshkenet dune field indicate that there has been no noticeable movement of the dunes over an 8-month period. The dunes, which are oriented both parallel and perpendicular to the radar illumination, appear to be dark features on a brighter substrate. Bright and dark patches that were visible in either cycle 1 or 2 data, but not both, allowed identification of several regions in the southern part of Venus that may contain microdunes. The microdunes are associated with several parabolic crater deposits in the region and are probably similar to those formed in wind tunnel experiments under Venus-like conditions. Bragg scattering and/or subpixel reflections from the near-normal face on asymmetric microdunes may account for these bright and dark patches. Look-angle effects and the lack of sufficient sand-size particles seem to be the most likely reasons so few dunes were identified in Magellan data. Insufficient wind speeds, thinness of sand cover, and difficulty in identifying isolated dunes may also be contributors to the scarcity of dunes.

High-energy electron emission from metallic nano-tips driven by intense single-cycle terahertz pulses

PubMed Central

Li, Sha; Jones, R. R.

2016-01-01

Electrons ejected from atoms and subsequently driven to high energies in strong laser fields enable techniques from attosecond pulse generation to imaging with rescattered electrons. Analogous processes govern strong-field electron emission from nanostructures, where long wavelength radiation and large local field enhancements hold the promise for producing electrons with substantially higher energies, allowing for higher resolution time-resolved imaging. Here we report on the use of single-cycle terahertz pulses to drive electron emission from unbiased nano-tips. Energies exceeding 5 keV are observed, substantially greater than previously attained at higher drive frequencies. Despite large differences in the magnitude of the respective local fields, we find that the maximum electron energies are only weakly dependent on the tip radius, for 10 nm

Alternative laser system for cesium magneto-optical trap via optical injection locking to sideband of a 9-GHz current-modulated diode laser.

PubMed

Diao, Wenting; He, Jun; Liu, Zhi; Yang, Baodong; Wang, Junmin

2012-03-26

By optical injection of an 852-nm extended-cavity diode laser (master laser) to lock the + 1-order sideband of a ~9-GHz-current-modulated diode laser (slave laser), we generate a pair of phase-locked lasers with a frequency difference up to ~9-GHz for a cesium (Cs) magneto-optical trap (MOT) with convenient tuning capability. For a cesium MOT, the master laser acts as repumping laser, locked to the Cs 6S₁/₂ (F = 3) - 6P₃/₂ (F' = 4) transition. When the + 1-order sideband of the 8.9536-GHz-current-modulated slave laser is optically injection-locked, the carrier operates on the Cs 6S₁/₂ (F = 4) - 6P₃/₂ (F' = 5) cooling cycle transition with -12 MHz detuning and acts as cooling/trapping laser. When carrying a 9.1926-GHz modulation signal, this phase-locked laser system can be applied in the fields of coherent population trapping and coherent manipulation of Cs atomic ground states.

Probing electron delays in above-threshold ionization

DOE PAGES

Zipp, Lucas J.; Natan, Adi; Bucksbaum, Philip H.

2014-11-21

Recent experiments have revealed attosecond delays in the emission of electrons from atoms ionized by extreme UV light, offering a glimpse into the ultrafast nature of light-induced electron dynamics. In this work, we extend these measurements to the strong-field above-threshold ionization (ATI) regime, by measuring delays in the photoemission of electrons from argon in the presence of an intense laser field. We probe the ATI process with a weak coherent reference, at half the laser frequency. The interfering ionization signal reveals the relative spectral phase of adjacent ATI channels, with an equivalent resolution of a few attoseconds. These relative delaysmore » depend on the strong field, and approach zero at higher intensity. Our phase measurements of ATI electrons show how strong fields alter ionization dynamics in atoms.« less

Nondegenerate parametric generation of 2.2-mJ, few-cycle 2.05-μm pulses using a mixed phase matching scheme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Guibao; Wandel, Scott F.; Jovanovic, Igor, E-mail: ijovanovic@psu.edu

2014-02-15

We describe the production of 2.2-mJ, ∼6 optical-cycle-long mid-infrared laser pulses with a carrier wavelength of 2.05 μm in a two-stage β-BaB{sub 2}O{sub 4} nondegenerate optical parametric amplifier design with a mixed phase matching scheme, which is pumped by a standard Ti:sapphire chirped-pulse amplification system. It is demonstrated that relatively high pulse energies, short pulse durations, high stability, and excellent beam profiles can be obtained using this simple approach, even without the use of optical parametric chirped-pulse amplification.

Quantum control of molecular fragmentation in strong laser fields

NASA Astrophysics Data System (ADS)

Zohrabi, Mohammad

Present advances in laser technology allow the production of ultrashort (<˜5 fs, approaching single cycle at 800 nm), intense tabletop laser pulses. At these high intensities laser-matter interactions cannot be described with perturbation theory since multiphoton processes are involved. This is in contrast to photodissociation by the absorption of a single photon, which is well described by perturbation theory. For example, at high intensities (<˜5x1013 W/cm2) the fragmentation of molecular hydrogen ions has been observed via the absorption of three or more photons. In another example, an intriguing dissociation mechanism has been observed where molecular hydrogen ions seem to fragment by apparently absorbing no photons. This is actually a two photon process, photoabsorption followed by stimulated emission, resulting in low energy fragments. We are interested in exploring these kinds of multiphoton processes. Our research group has studied the dynamics and control of fragmentation induced by strong laser fields in a variety of molecular targets. The main goal is to provide a basic understanding of fragmentation mechanisms and possible control schemes of benchmark systems such as H2+. This knowledge is further extended to more complex systems like the benchmark H3+ polyatomic and other molecules. In this dissertation, we report research based on two types of experiments. In the first part, we describe laser-induced fragmentation of molecular ion-beam targets. In the latter part, we discuss the formation of highly-excited neutral fragments from hydrogen molecules using ultrashort laser pulses. In carrying out these experiments, we have also extended experimental techniques beyond their previous capabilities. We have performed a few experiments to advance our understanding of laser-induced fragmentation of molecular-ion beams. For instance, we explored vibrationally resolved spectra of O2+ dissociation using various wavelengths. We observed a vibrational suppression effect in the dissociation spectra due to the small magnitude of the dipole transition moment, which depends on the photon energy --- a phenomenon known as Cooper minima. By changing the laser wavelength, the Cooper minima shift, a fact that was used to identify the dissociation pathways. In another project, we studied the carrier-envelope phase (CEP) dependences of highly-excited fragments from hydrogen molecules. General CEP theory predicts a CEP dependence in the total dissociation yield due to the interference of dissociation pathways differing by an even net number of photons, and our measurements are consistent with this prediction. Moreover, we were able to extract the difference in the net number of photons involved in the interfering pathways by using a Fourier analysis. In terms of our experimental method, we have implemented a pump-probe style technique on a thin molecular ion-beam target and explored the feasibility of such experiments. The results presented in this work should lead to a better understanding of the dynamics and control in molecular fragmentation induced by intense laser fields.

An assessment of laser velocimetry in hypersonic flow

NASA Technical Reports Server (NTRS)

1992-01-01

Although extensive progress has been made in computational fluid mechanics, reliable flight vehicle designs and modifications still cannot be made without recourse to extensive wind tunnel testing. Future progress in the computation of hypersonic flow fields is restricted by the need for a reliable mean flow and turbulence modeling data base which could be used to aid in the development of improved empirical models for use in numerical codes. Currently, there are few compressible flow measurements which could be used for this purpose. In this report, the results of experiments designed to assess the potential for laser velocimeter measurements of mean flow and turbulent fluctuations in hypersonic flow fields are presented. Details of a new laser velocimeter system which was designed and built for this test program are described.

Optical Frequency Stabilization and Optical Phase Locked Loops: Golden Threads of Precision Measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taubman, Matthew S.

Stabilization of lasers through locking to optical cavities, atomic transitions, and molecular transitions has enabled the field of precision optical measurement since shortly after the invention of the laser. Recent advances in the field have produced an optical clock that is orders of magnitude more stable than those of just a few years prior. Phase locking of one laser to another, or to a frequency offset from another, formed the basis for linking stable lasers across the optical spectrum, such frequency chains exhibiting progressively finer precision through the years. Phase locking between the modes within a femtosecond pulsed laser hasmore » yielded the optical frequency comb, one of the most beautiful and useful instruments of our time. This talk gives an overview of these topics, from early work through to the latest 1E-16 thermal noise-limited precision recently attained for a stable laser, and the ongoing quest for ever finer precision and accuracy. The issues of understanding and measuring line widths and shapes are also studied in some depth, highlighting implications for servo design for sub-Hz line widths.« less

Attosecond nanoscale near-field sampling

PubMed Central

Förg, B.; Schötz, J.; Süßmann, F.; Förster, M.; Krüger, M.; Ahn, B.; Okell, W. A.; Wintersperger, K.; Zherebtsov, S.; Guggenmos, A.; Pervak, V.; Kessel, A.; Trushin, S. A.; Azzeer, A. M.; Stockman, M. I.; Kim, D.; Krausz, F.; Hommelhoff, P.; Kling, M. F.

2016-01-01

The promise of ultrafast light-field-driven electronic nanocircuits has stimulated the development of the new research field of attosecond nanophysics. An essential prerequisite for advancing this new area is the ability to characterize optical near fields from light interaction with nanostructures, with sub-cycle resolution. Here we experimentally demonstrate attosecond near-field retrieval for a tapered gold nanowire. By comparison of the results to those obtained from noble gas experiments and trajectory simulations, the spectral response of the nanotaper near field arising from laser excitation can be extracted. PMID:27241851

Performance tests of the 5 TW, 1 kHz, passively CEP-stabilized ELI-ALPS SYLOS few-cycle laser system (Conference Presentation)

NASA Astrophysics Data System (ADS)

Stanislauskas, Tomas; Budriūnas, Rimantas; Veitas, Gediminas; Gadonas, Darius; Adamonis, Jonas; Aleknavičius, Aidas; Masian, Gžegož; Kuprionis, Zenonas; Hoff, Dominik; Paulus, Gerhard G.; Börzsönyi, Ádám.; Toth, Szabolcs; Kovacs, Mate; Csontos, János; López-Martens, Rodrigo; Osvay, Károly

2017-05-01

ELI-ALPS in Hungary, one of the three pillars of the Extreme Light Infrastructure, aims at providing diverse light sources, including energetic attosecond pulses at the highest possible repetition rates. One of the main laser systems for driving plasma and gas-based HHG stages, is a state-of-the-art 1 kHz few-cycle laser called SYLOS. Targeted pulse parameters are an energy of 100 mJ and a duration shorter than two optical cycles (<6 fs), with outstanding energy, phase and pointing stability as well as high spatiotemporal quality. The first phase of the laser system has already set a new standard in kHz laser system engineering and technology. The performance and reliability of the SYLOS laser have been consistently tested over the course of a six-month trial period. During this time the system was running at least 8 hours a day at full power for more than 5 months. The current output parameters are 5 TW peak power, 45 mJ pulse energy with 9 fs duration and 300 mrad CEP stability, while the spectrum spans over 300 nm around 840 nm central wavelength. The layout follows the general scheme NOPCPA architecture with a passively CEP-stabilized front-end. The pulses are negatively chirped for the amplification process and compressed by a combination of large aperture bulk glass blocks and positively chirped mirrors under vacuum conditions at the output. During the trial period, the laser system demonstrated outstanding reliability. Daily startup and shutdown procedures take only a few minutes, and the command-control system enables pulse parameters to be modified instantly. Controlling the delays of individual NOPCPA stages makes it possible to tailor the output spectrum of the pulses and tune the central wavelength between 770 nm and 940 nm. We performed several experimental tests to find out the pulse characteristics. Pulse duration was verified with Wizzler, chirp-scan, autocorrelation methods and a stereo-ATI independently. All of them confirmed the sub-9 fs pulse duration. We recorded the long-term waveform and pointing stabilities of the beam in order to find out the effect of the temperature load on optical elements. Excluding a short initial warm up time, stable signals were observed in general. The in-loop and out-of-loop CEP stability was cross-checked between f-to-2f and stereo-ATI devices. Moreover, the inherent CEP stability of the system without feedback loop was also found to be surprisingly robust thanks to the passive CEP stabilization of the front-end. The polarization contrast was better than 1000:1. The temporal contrast was also measured independently with Sequoia and Tundra cross-correlators, and on the ns scale with a fast photodiode and GHz oscilloscope as well. Results showed that the pulse pedestal generally consists of parametric superfluorescence below the 1E-7 level and about 100 ps long, well in accordance with the pump duration. Delaying the pump pulse allows us to shift the seed pulse to the front and reach a pre-pulse pedestal below 1E-11 at 30 ps before the pulse peak. Detailed findings on all the examined pulse characteristics of the SYLOS laser will be reported in this presentation.

Toward Generation of High Power Ultrafast White Light Laser Using Femtosecond Terawatt Laser in a Gas-Filled Hollow-Core Fiber

NASA Astrophysics Data System (ADS)

Tawfik, Walid

2015-06-01

In this work, we could experimentally achieved the generation of white-light laser pulses of few-cycle fs pulses using a neon-filled hollow-core fiber. The observed pulses reached 6-fs at at repetition rate of 1 kHz using 2.5 mJ of 31 fs femtosecond pulses. The pulse compressing achieved by the supercontinuum produced in static neon-filled hollow fibers while the dispersion compensation is achieved by five pairs of chirped mirrors. We showed that gas pressure can be used to continuously vary the bandwidth from 350 nm to 900 nm. Furthermore, the applied technique allows for a straightforward tuning of the pulse duration via the gas pressure whilst maintaining near-transform-limited pulses with constant output energy, thereby reducing the complications introduced by chirped pulses. Through measurements of the transmission through the fiber as a function of gas pressure, a high throughput exceeding 60% was achieved. Adaptive pulse compression is achieved by using the spectral phase obtained from a spectral phase interferometry for direct electric field reconstruction (SPIDER) measurement as feedback for a liquid crystal spatial light modulator (SLM). The spectral phase of these supercontinua is found to be extremely stable over several hours. This allowed us to demonstrate successful compression to pulses as short as 5.2 fs with controlled wide spectral bandwidth, which could be used to excite different states in complicated molecules at once.

Probing different regimes of strong field light-matter interaction with semiconductor quantum dots and few cavity photons

NASA Astrophysics Data System (ADS)

Hargart, F.; Roy-Choudhury, K.; John, T.; Portalupi, S. L.; Schneider, C.; Höfling, S.; Kamp, M.; Hughes, S.; Michler, P.

2016-12-01

In this work we present an extensive experimental and theoretical investigation of different regimes of strong field light-matter interaction for cavity-driven quantum dot (QD) cavity systems. The electric field enhancement inside a high-Q micropillar cavity facilitates exceptionally strong interaction with few cavity photons, enabling the simultaneous investigation for a wide range of QD-laser detuning. In case of a resonant drive, the formation of dressed states and a Mollow triplet sideband splitting of up to 45 μeV is measured for a mean cavity photon number < {n}c> ≤slant 1. In the asymptotic limit of the linear AC Stark effect we systematically investigate the power and detuning dependence of more than 400 QDs. Some QD-cavity systems exhibit an unexpected anomalous Stark shift, which can be explained by an extended dressed 4-level QD model. We provide a detailed analysis of the QD-cavity systems properties enabling this novel effect. The experimental results are successfully reproduced using a polaron master equation approach for the QD-cavity system, which includes the driving laser field, exciton-cavity and exciton-phonon interactions.

Optical gating and streaking of free electrons with sub-optical cycle precision

PubMed Central

Kozák, M.; McNeur, J.; Leedle, K. J.; Deng, H.; Schönenberger, N.; Ruehl, A.; Hartl, I.; Harris, J. S.; Byer, R. L.; Hommelhoff, P.

2017-01-01

The temporal resolution of ultrafast electron diffraction and microscopy experiments is currently limited by the available experimental techniques for the generation and characterization of electron bunches with single femtosecond or attosecond durations. Here, we present proof of principle experiments of an optical gating concept for free electrons via direct time-domain visualization of the sub-optical cycle energy and transverse momentum structure imprinted on the electron beam. We demonstrate a temporal resolution of 1.2±0.3 fs. The scheme is based on the synchronous interaction between electrons and the near-field mode of a dielectric nano-grating excited by a femtosecond laser pulse with an optical period duration of 6.5 fs. The sub-optical cycle resolution demonstrated here is promising for use in laser-driven streak cameras for attosecond temporal characterization of bunched particle beams as well as time-resolved experiments with free-electron beams. PMID:28120930

Dipole-resonance assisted isomerization in the electronic ground state using few-cycle infrared pulses.

PubMed

Skocek, Oliver; Uiberacker, Christoph; Jakubetz, Werner

2011-06-30

A computational investigation of HCN → HNC isomerization in the electronic ground state by one- and few-cycle infrared pulses is presented. Starting from a vibrationally pre-excited reagent state, isomerization yields of more than 50% are obtained using single one- to five-cycle pulses. The principal mechanism includes two steps of population transfer by dipole-resonance (DR), and hence, the success of the method is closely linked to the polarity of the system and, in particular, the stepwise change of the dipole moment from reactant to transition state and on to products. The yield drops massively if the diagonal dipole matrix elements are artificially set to zero. In detail, the mechanism includes DR-induced preparation of a delocalized vibrational wavepacket, which traverses the barrier region and is finally trapped in the product well by DR-dominated de-excitation. The excitation and de-excitation steps are triggered by pulse lobes of opposite field direction. As the number of optical cycles is increased, the leading field lobes prepare a vibrational superposition state by off-resonant ladder climbing, which is then subjected to the three steps of the principal isomerization mechanism. DR excitation is more efficient from a preformed vibrational wavepacket than from a molecular eigenstate. The entire process can be loosely described as Tannor-Kosloff-Rice type transfer mechanism on a single potential surface effected by a single pulse, individual field lobes assuming the roles of pump- and dump-pulses. Pre-excitation to a transient wavepacket can be enhanced by applying a separate, comparatively weak few-cycle prepulse, in which the prepulse prepares a vibrational wavepacket. The two-pulse setup corresponds to a double Tannor-Kosloff-Rice control scheme on a single potential surface.

Development and performance of a laser heterodyne spectrometer using tunable semiconductor lasers as local oscillators

NASA Technical Reports Server (NTRS)

Glenar, D.; Kostiuk, T.; Jennings, D. E.; Mumma, M. J.

1980-01-01

A diode laser based IR heterodyne spectrometer for laboratory and field use was developed for high efficiency operation between 7.5 and 8.5 microns. The local oscillator is a PbSSe tunable diode laser kept continuously at operating temperatures of 12-60 K using a closed cycle cooler. The laser output frequency is controlled and stabilized using a high precision diode current supply, constant temperature controller, and a shock isolator mounted between the refrigerator cold tip and the diode mount. Single laser modes are selected by a grating placed in the local oscillator beam. The system employs reflecting optics throughout to minimize losses from internal reflection and absorption, and to eliminate chromatic effects. Spectral analysis of the diode laser output between 0 and 1 GHz reveals excess noise at many diode current settings, which limits the infrared spectral regions over which useful heterodyne operation can be achieved. System performance has been studied by making heterodyne measurements of etalon fringes and several Freon 13 (CF3Cl) absorption lines against a laboratory blackbody source. Preliminary field tests have also been performed using the Sun as a source.

Magnetic plasma confinement for laser ion source.

PubMed

Okamura, M; Adeyemi, A; Kanesue, T; Tamura, J; Kondo, K; Dabrowski, R

2010-02-01

A laser ion source (LIS) can easily provide a high current beam. However, it has been difficult to obtain a longer beam pulse while keeping a high current. On occasion, longer beam pulses are required by certain applications. For example, more than 10 micros of beam pulse is required for injecting highly charged beams to a large sized synchrotron. To extend beam pulse width, a solenoid field was applied at the drift space of the LIS at Brookhaven National Laboratory. The solenoid field suppressed the diverging angle of the expanding plasma and the beam pulse was widened. Also, it was observed that the plasma state was conserved after passing through a few hundred gauss of the 480 mm length solenoid field.

Plasma Chemistry Processes in the Closed Cycle EDL.

DTIC Science & Technology

1979-07-01

chemistry. The present study is mainly concerned with plasma by-products and, to some degree, with initial impurities and their influence on laser...performance. The plasma chemistry important in the formation of these by-products has been studied in greatest detail for He/N 2 /C0 2 mixtures loaded by...cases for two closed cycle EDL devices currently under development. The study includes the effects on performance of variations in the electric field

Advances in High Energy Solid-State 2-micron Laser Transmitter Development for Ground and Airborne Wind and CO2 Measurements

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Chen, Songsheng; Kavaya, Michael J.; Trieu, Bo; Bai, Yingxin; Petzar, Paul; Modlin, Edward A.; Koch, Grady;

Progress on High-Energy 2-micron Solid State Laser for NASA Space-Based Wind and Carbon Dioxide Measurements

NASA Technical Reports Server (NTRS)

Singh, Upendra N.

2011-01-01

Sustained research efforts at NASA Langley Research Center during last fifteen years have resulted in significant advancement of a 2-micron diode-pumped, solid-state laser transmitter for wind and carbon dioxide measurements from ground, air and space-borne platforms. Solid-state 2-micron laser is a key subsystem for a coherent Doppler lidar that measures the horizontal and vertical wind velocities with high precision and resolution. The same laser, after a few modifications, can also be used in a Differential Absorption Lidar system for measuring atmospheric CO2 concentration profiles. Researchers at NASA Langley Research Center have developed a compact, flight capable, high energy, injection seeded, 2-micron laser transmitter for ground and airborne wind and carbon dioxide measurements. It is capable of producing 250 mJ at 10 Hz by an oscillator and one amplifier. This compact laser transmitter was integrated into a mobile trailer based coherent Doppler wind and CO2 DIAL system and was deployed during field measurement campaigns. This paper will give an overview of 2-micron solid-state laser technology development and discuss results from recent ground-based field measurements.

From Protist to Proxy: Dinoflagellates as signal carriers for past climate and carbon cycling

NASA Astrophysics Data System (ADS)

Sluijs, A.; Reichart, G. J.; Hoins, M.; Waal, D. V. D.; Rost, B.; Roij, L. V.

2016-12-01

The (paleo)ecology of dinoflagellates and their organic dinocysts that preserve in sediments are often employed as tracers of past ocean conditions, such as temperature, productivity, ocean circulation, salinity, and sea ice, for the late Triassic to the Modern. Over the past decade, such reconstructions, which are based on empirical information as well as extensive studies of modern systems, have made dinocyst paleoecology a pivotal tool that is complementary to other microfossil groups and (in)organic geochemical techniques. Building on this work, we have carried out culturing experiments to quantify and physiologically underpin CO2-dependent carbon isotope fractionation of several species of dinoflagellates. This work indicates potential for a new CO2 proxy based on fossil dinoflagellate cysts. Moreover, we developed a laser ablation nano combustion gas chromatography isotope ratio mass spectrometry (LA-nC-GC-IRMS) setup capable of measuring δ13C of organic particles of only 40 nanograms of carbon, with accuracy and precision of at most 0.4‰. This allows for the analyses of single to a few dinocyst specimens, setting the stage for a whole new research field investigating variability within populations of dinocysts, but also of pollen and other small scale carbon particles in geology, biology and other research fields. We present the first dinocyst δ13C results of the new method from modern systems and in the paleo-domain, particularly related to marine carbon cycling and CO2.

High passive CEP stability from a few-cycle, tunable NOPA-DFG system for observation of CEP-effects in photoemission.

PubMed

Vogelsang, Jan; Robin, Jörg; Piglosiewicz, Björn; Manzoni, Cristian; Farinello, Paolo; Melzer, Stefan; Feru, Philippe; Cerullo, Giulio; Lienau, Christoph; Groß, Petra

2014-10-20

The investigation of fundamental mechanisms taking place on a femtosecond time scale is enabled by ultrafast pulsed laser sources. Here, the control of pulse duration, center wavelength, and especially the carrier-envelope phase has been shown to be of essential importance for coherent control of high harmonic generation and attosecond physics and, more recently, also for electron photoemission from metallic nanostructures. In this paper we demonstrate the realization of a source of 2-cycle laser pulses tunable between 1.2 and 2.1 μm, and with intrinsic CEP stability. The latter is guaranteed by difference frequency generation between the output pulse trains of two noncollinear optical parametric amplifier stages that share the same CEP variations. The CEP stability is better than 50 mrad over 20 minutes, when averaging over 100 pulses. We demonstrate the good CEP stability by measuring kinetic energy spectra of photoemitted electrons from a single metal nanostructure and by observing a clear variation of the electron yield with the CEP.

Focusing and transport of high-intensity multi-MeV proton bunches from a compact laser-driven source

NASA Astrophysics Data System (ADS)

Busold, S.; Schumacher, D.; Deppert, O.; Brabetz, C.; Frydrych, S.; Kroll, F.; Joost, M.; Al-Omari, H.; Blažević, A.; Zielbauer, B.; Hofmann, I.; Bagnoud, V.; Cowan, T. E.; Roth, M.

2013-10-01

Laser ion acceleration provides for compact, high-intensity ion sources in the multi-MeV range. Using a pulsed high-field solenoid, for the first time high-intensity laser-accelerated proton bunches could be selected from the continuous exponential spectrum and delivered to large distances, containing more than 109 particles in a narrow energy interval around a central energy of 9.4 MeV and showing ≤30mrad envelope divergence. The bunches of only a few nanoseconds bunch duration were characterized 2.2 m behind the laser-plasma source with respect to arrival time, energy width, and intensity as well as spatial and temporal bunch profile.

One step synthesis of porous graphene by laser ablation: A new and facile approach

NASA Astrophysics Data System (ADS)

Kazemizadeh, Fatemeh; Malekfar, Rasoul

2018-02-01

Porous graphene (PG) was obtained using one step laser process. Synthesis was carried out by laser ablation of nickel-graphite target under ultra-high flow of argon gas. The field emission scanning electron microscopy (FE-SEM) results showed the formation of a porous structure and the transmission electron microscopy (TEM) revealed that the porosity of PGs increase under intense laser irradiation. Structural characterization study using Raman spectroscopy, X-ray powder diffraction (XRD) and selected area electron diffraction (SAED) technique showed that the obtained PGs display high crystalline structure in the form of few layer rhombohedral graphitic arrangement that can be interpreted as the phase prior to the formation of other carbon nanostructures.

Laser characterization of electric field oscillations in the Hall thruster breathing mode

NASA Astrophysics Data System (ADS)

Young, Christopher; Lucca Fabris, Andrea; MacDonald-Tenenbaum, Natalia; Hargus, William, Jr.; Cappelli, Mark

2016-10-01

Hall thrusters are a mature technology for space propulsion applications that exhibit a wide array of dynamic behavior, including plasma waves, instabilities and turbulence. One common low frequency (10-50 kHz) discharge current oscillation is the breathing mode, a cycle of neutral propellant injection, strong ionization, and ion acceleration by a steep potential gradient. A time-resolved laser-induced fluorescence diagnostic non-intrusively captures this propagating ionization front in the channel of a commercial BHT-600 Hall thruster manufactured by Busek Co. Measurements of ion velocity and relative ion density (using the 5 d[ 4 ] 7 / 2 - 6 p[ 3 ] 5 / 2 Xe II transition at 834.95 nm, vacuum) reveal a dynamic electric field structure traversing the channel throughout the breathing mode cycle. This work is sponsored by the U.S. Air Force Office of Scientific Research, with Dr. M. Birkan as program manager. C.Y. acknowledges support from the DOE NSSA Stewardship Science Graduate Fellowship under contract DE-FC52-08NA28752.

Recollision induced excitation-ionization with counter-rotating two-color circularly polarized laser field

NASA Astrophysics Data System (ADS)

Ben, Shuai; Guo, Pei-Ying; Pan, Xue-Fei; Xu, Tong-Tong; Song, Kai-Li; Liu, Xue-Shen

2017-07-01

Nonsequential double ionization of Ar by a counter-rotating two-color circularly polarized laser field is theoretically investigated. At the combined intensity in the "knee" structure range, the double ionization occurs mainly through recollision induced excitation followed by subsequent ionization of Ar+∗ . By tracing the history of the recollision trajectories, we explain how the relative intensity ratio of the two colors controls the correlated electron dynamics and optimizes the ionization yields. The major channels contributing to enhancing the double ionization are through the elliptical trajectories with smaller travel time but not through the triangle shape or the other long cycle trajectories. Furthermore, the correlated electron dynamics could be limited to the attosecond time scale by adjusting the relative intensity ratio. Finally, the double ionization from doubly excited complex at low laser intensity is qualitatively discussed.

Effect of Moisture Content of Paper Material on Laser Cutting

NASA Astrophysics Data System (ADS)

Stepanov, Alexander; Saukkonen, Esa; Piili, Heidi; Salminen, Antti

Laser technology has been used in industrial processes for several decades. The most advanced development and implementation took place in laser welding and cutting of metals in automotive and ship building industries. However, there is high potential to apply laser processing to other materials in various industrial fields. One of these potential fields could be paper industry to fulfill the demand for high quality, fast and reliable cutting technology. Difficulties in industrial application of laser cutting for paper industry are associated to lack of basic information, awareness of technology and its application possibilities. Nowadays possibilities of using laser cutting for paper materials are widened and high automation level of equipment has made this technology more interesting for manufacturing processes. Promising area of laser cutting application at paper making machines is longitudinal cutting of paper web (edge trimming). There are few locations at a paper making machine where edge trimming is usually done: wet press section, calender or rewinder. Paper web is characterized with different moisture content at different points of the paper making machine. The objective of this study was to investigate the effect of moisture content of paper material on laser cutting parameters. Effect of moisture content on cellulose fibers, laser absorption and energy needed for cutting is described as well. Laser cutting tests were carried out using CO2 laser.

Integrating solids and gases for attosecond pulse generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hammond, T. J.; Monchoce, Sylvain; Zhang, Chunmei

Here, control of the field of few-cycle optical pulses has had an enormous impact on attosecond science. Subcycle pulses open the potential for non-adiabatic phase matching while concentrating the electric field so it can be used most efficiently. However, subcycle field transients have been difficult to generate. We exploit the perturbative response of a sub-100 µm thick monocrystalline quartz plate irradiated by an intense few-cycle 1.8 µm pulse, which creates a phase-controlled supercontinuum spectrum. Within the quartz, the pulse becomes space–time coupled as it generates a parallel second harmonic. Vacuum propagation naturally leads to a subcycle electric-field transient whose envelopemore » is sculpted by the carrier envelope phase of the incident radiation. We show that a second medium (either gas or solid) can generate isolated attosecond pulses in the extreme ultraviolet region. With no optical elements between the components, the process is scalable to very high energy pulses and allows the use of diverse media.« less

Integrating solids and gases for attosecond pulse generation

DOE PAGES

Hammond, T. J.; Monchoce, Sylvain; Zhang, Chunmei; ...

2017-08-21

Here, control of the field of few-cycle optical pulses has had an enormous impact on attosecond science. Subcycle pulses open the potential for non-adiabatic phase matching while concentrating the electric field so it can be used most efficiently. However, subcycle field transients have been difficult to generate. We exploit the perturbative response of a sub-100 µm thick monocrystalline quartz plate irradiated by an intense few-cycle 1.8 µm pulse, which creates a phase-controlled supercontinuum spectrum. Within the quartz, the pulse becomes space–time coupled as it generates a parallel second harmonic. Vacuum propagation naturally leads to a subcycle electric-field transient whose envelopemore » is sculpted by the carrier envelope phase of the incident radiation. We show that a second medium (either gas or solid) can generate isolated attosecond pulses in the extreme ultraviolet region. With no optical elements between the components, the process is scalable to very high energy pulses and allows the use of diverse media.« less

Laser beam shaping for biomedical microscopy techniques

NASA Astrophysics Data System (ADS)

Laskin, Alexander; Kaiser, Peter; Laskin, Vadim; Ostrun, Aleksei

2016-04-01

Uniform illumination of a working field is very important in optical systems of confocal microscopy and various implementations of fluorescence microscopy like TIR, SSIM, STORM, PALM to enhance performance of these laser-based research techniques. Widely used TEM00 laser sources are characterized by essentially non-uniform Gaussian intensity profile which leads usually to non-uniform intensity distribution in a microscope working field or in a field of microlenses array of a confocal microscope optical system, this non-uniform illumination results in instability of measuring procedure and reducing precision of quantitative measurements. Therefore transformation of typical Gaussian distribution of a TEM00 laser to flat-top (top hat) profile is an actual technical task, it is solved by applying beam shaping optics. Due to high demands to optical image quality the mentioned techniques have specific requirements to a uniform laser beam: flatness of phase front and extended depth of field, - from this point of view the microscopy techniques are similar to holography and interferometry. There are different refractive and diffractive beam shaping approaches used in laser industrial and scientific applications, but only few of them are capable to fulfil the optimum conditions for beam quality required in discussed microscopy techniques. We suggest applying refractive field mapping beam shapers πShaper, which operational principle presumes almost lossless transformation of Gaussian to flat-top beam with flatness of output wavefront, conserving of beam consistency, providing collimated low divergent output beam, high transmittance, extended depth of field, negligible wave aberration, and achromatic design provides capability to work with several lasers with different wavelengths simultaneously. The main function of a beam shaper is transformation of laser intensity profile, further beam transformation to provide optimum for a particular technique spot size and shape has to be realized by an imaging optical system which can include microscope objectives and tube lenses. This paper will describe design basics of refractive beam shapers and optical layouts of their applying in microscopy systems. Examples of real implementations and experimental results will be presented as well.

Capillary Absorption Spectrometer for 13C Isotopic Composition of Pico to Subpico Molar Sample Quantities

NASA Astrophysics Data System (ADS)

Moran, J.; Kelly, J.; Sams, R.; Newburn, M.; Kreuzer, H.; Alexander, M.

2011-12-01

Quick incorporation of IR spectroscopy based isotope measurements into cutting edge research in biogeochemical cycling attests to the advantages of a spectroscopy versus mass spectrometry method for making some 13C measurements. The simple principles of optical spectroscopy allow field portability and provide a more robust general platform for isotope measurements. We present results with a new capillary absorption spectrometer (CAS) with the capability of reducing the sample size required for high precision isotopic measurements to the picomolar level and potentially the sub-picomolar level. This work was motivated by the minute sample size requirements for laser ablation isotopic studies of carbon cycling in microbial communities but has potential to be a valuable tool in other areas of biological and geological research. The CAS instrument utilizes a capillary waveguide as a sample chamber for interrogating CO2 via near IR laser absorption spectroscopy. The capillary's small volume (~ 0.5 mL) combined with propagation and interaction of the laser mode with the entire sample reduces sample size requirements to a fraction of that accessible with commercially available IR absorption including those with multi-pass or ring-down cavity systems. Using a continuous quantum cascade laser system to probe nearly adjacent rovibrational transitions of different isotopologues of CO2 near 2307 cm-1 permits sample measurement at low analyte pressures (as low as 2 Torr) for further sensitivity improvement. A novel method to reduce cw-fringing noise in the hollow waveguide is presented, which allows weak absorbance features to be studied at the few ppm level after averaging 1,000 scans in 10 seconds. Detection limits down to the 20 picomoles have been observed, a concentration of approximately 400 ppm at 2 Torr in the waveguide with precision and accuracy at or better than 1 %. Improvements in detection and signal averaging electronics and laser power and mode quality are anticipated to reduce the required samples size to a 100-200 femtomoles of carbon. We report the application of the CAS system to a Laser Ablation-Catalytic-Combustion (LA-CC) micro-sampler system for selectively harvesting detailed sections of a solid surface for 13C analysis. This technique results in a three order of magnitude sensitivity improvement reported for our isotope measurement system compared to typical IRMS, providing new opportunities for making detailed investigations into wide ranges of microbial, physical, and chemical systems. The CAS is interfaced directly to the LA CC system currently operating at a 50 μm spatial resolution. We demonstrate that particulates produced by a Nd:YAG laser (λ=266nm) are isotopically homogenous with the parent material as measured by both IRMS and the CAS system. An improved laser ablation system operating at 193 nm with a spatial resolution of 2 microns or better is under development which will demonstrate the utility of the CAS system for sample sizes too low for IRMS. The improved sensitivities and optimized spatial targeting of such a system could interrogate targets as detailed as small cell clusters or intergrain organic deposits and could enhance ability to track biogeochemical carbon cycling.

Semimetallization of dielectrics in strong optical fields

PubMed Central

Kwon, Ojoon; Paasch-Colberg, Tim; Apalkov, Vadym; Kim, Bum-Kyu; Kim, Ju-Jin; Stockman, Mark I.; Kim, D.

2016-01-01

At the heart of ever growing demands for faster signal processing is ultrafast charge transport and control by electromagnetic fields in semiconductors. Intense optical fields have opened fascinating avenues for new phenomena and applications in solids. Because the period of optical fields is on the order of a femtosecond, the current switching and its control by an optical field may pave a way to petahertz optoelectronic devices. Lately, a reversible semimetallization in fused silica on a femtosecond time scale by using a few-cycle strong field (~1 V/Å) is manifested. The strong Wannier-Stark localization and Zener-type tunneling were expected to drive this ultrafast semimetallization. Wider spread of this technology demands better understanding of whether the strong field behavior is universally similar for different dielectrics. Here we employ a carrier-envelope-phase stabilized, few-cycle strong optical field to drive the semimetallization in sapphire, calcium fluoride and quartz and to compare this phenomenon and show its remarkable similarity between them. The similarity in response of these materials, despite the distinguishable differences in their physical properties, suggests the universality of the physical picture explained by the localization of Wannier-Stark states. Our results may blaze a trail to PHz-rate optoelectronics. PMID:26888147

Semimetallization of dielectrics in strong optical fields

DOE PAGES

Kwon, Ojoon; Paasch-Colberg, Tim; Apalkov, Vadym; ...

2016-02-18

At the heart of ever growing demands for faster signal processing is ultrafast charge transport and control by electromagnetic fields in semiconductors. Intense optical fields have opened fascinating avenues for new phenomena and applications in solids. Because the period of optical fields is on the order of a femtosecond, the current switching and its control by an optical field may pave a way to petahertz optoelectronic devices. Lately, a reversible semimetallization in fused silica on a femtosecond time scale by using a few-cycle strong field (~1 V/Å) is manifested. The strong Wannier-Stark localization and Zener-type tunneling were expected to drivemore » this ultrafast semimetallization. Wider spread of this technology demands better understanding of whether the strong field behavior is universally similar for different dielectrics. Here we employ a carrier-envelope-phase stabilized, few-cycle strong optical field to drive the semimetallization in sapphire, calcium fluoride and quartz and to compare this phenomenon and show its remarkable similarity between them. The similarity in response of these materials, despite the distinguishable differences in their physical properties, suggests the universality of the physical picture explained by the localization of Wannier-Stark states. Lastly, our results may blaze a trail to PHz-rate optoelectronics.« less

Semimetallization of dielectrics in strong optical fields.

PubMed

Kwon, Ojoon; Paasch-Colberg, Tim; Apalkov, Vadym; Kim, Bum-Kyu; Kim, Ju-Jin; Stockman, Mark I; Kim, D

2016-02-18

At the heart of ever growing demands for faster signal processing is ultrafast charge transport and control by electromagnetic fields in semiconductors. Intense optical fields have opened fascinating avenues for new phenomena and applications in solids. Because the period of optical fields is on the order of a femtosecond, the current switching and its control by an optical field may pave a way to petahertz optoelectronic devices. Lately, a reversible semimetallization in fused silica on a femtosecond time scale by using a few-cycle strong field (~1 V/Å) is manifested. The strong Wannier-Stark localization and Zener-type tunneling were expected to drive this ultrafast semimetallization. Wider spread of this technology demands better understanding of whether the strong field behavior is universally similar for different dielectrics. Here we employ a carrier-envelope-phase stabilized, few-cycle strong optical field to drive the semimetallization in sapphire, calcium fluoride and quartz and to compare this phenomenon and show its remarkable similarity between them. The similarity in response of these materials, despite the distinguishable differences in their physical properties, suggests the universality of the physical picture explained by the localization of Wannier-Stark states. Our results may blaze a trail to PHz-rate optoelectronics.

Studies in Above- and Below-Threshold Harmonics in Argon with an Infrared Femtosecond Laser

NASA Astrophysics Data System (ADS)

Chew, Andrew; Yin, Yanchun; Li, Jie; Ren, Xiaoming; Cunningham, Eric; Wu, Yi; Chang, Zenghu

2016-05-01

We investigate and compare the above- and below-threshold harmonics in Argon gas using our recently-developed 1 kHz, two-cycle (11.4 fs), 3mJ, and carrier-envelope-phase(CEP)-stable laser at 1.6 μm. Such ultraviolet pulses can serve as pump or probe for studying dynamics in atoms and molecules. Unlike high harmonics with photon energy well above the ionization potential, the mechanism for generating harmonics near the ionization threshold is still under intense investigation. Previous work by Chini et al. on below-threshold harmonics was done using a 0.8 μm few-cycle Ti:Sapphire spectrally-broadened source with energy up to 300 μJ. It has been predicted by theory that free-free transitions dominate the below threshold harmonic generation as the laser wavelength increase from near infrared to mid-infrared. We are therefore interested in investigating how using a longer wavelength laser might lead to changes to the behavior of below-threshold harmonics when we vary various parameters. We report the π-periodity CEP dependence and ellipticity dependence of the above- and below-threshold harmonics. This material was based on work supported by National Science Foundation (1068604), Army Research Office (W911NF-14-1-0383), Air Force Office of Scientific Research (FA9550-15-1-0037) and the DARPA PULSE program by a Grant from AMRDEC (W31P4Q1310017).

Disentangling Intracycle Interferences in Photoelectron Momentum Distributions Using Orthogonal Two-Color Laser Fields

NASA Astrophysics Data System (ADS)

Xie, Xinhua; Wang, Tian; Yu, ShaoGang; Lai, XuanYang; Roither, Stefan; Kartashov, Daniil; Baltuška, Andrius; Liu, XiaoJun; Staudte, André; Kitzler, Markus

2017-12-01

We use orthogonally polarized two-color (OTC) laser pulses to separate quantum paths in the multiphoton ionization of Ar atoms. Our OTC pulses consist of 400 and 800 nm light at a relative intensity ratio of 10 ∶1 . We find a hitherto unobserved interference in the photoelectron momentum distribution, which exhibits a strong dependence on the relative phase of the OTC pulse. Analysis of model calculations reveals that the interference is caused by quantum pathways from nonadjacent quarter cycles.

Towards a petawatt-class few-cycle infrared laser system via dual-chirped optical parametric amplification.

PubMed

Fu, Yuxi; Midorikawa, Katsumi; Takahashi, Eiji J

2018-05-16

Expansion of the wavelength range for an ultrafast laser is an important ingredient for extending its range of applications. Conventionally, optical parametric amplification (OPA) has been employed to expand the laser wavelength to the infrared (IR) region. However, the achievable pulse energy and peak power have been limited to the mJ and the GW level, respectively. A major difficulty in the further energy scaling of OPA results from a lack of suitable large nonlinear crystals. Here, we circumvent this difficulty by employing a dual-chirped optical parametric amplification (DC-OPA) scheme. We successfully generate a multi-TW IR femtosecond laser pulse with an energy of 100 mJ order, which is higher than that reported in previous works. We also obtain excellent energy scaling ability, ultrashort pulses, flexiable wavelength tunability, and high-energy stability, which prove that DC-OPA is a superior method for the energy scaling of IR pulses to the 10 J/PW level.

Frequency-domain nonlinear optics in two-dimensionally patterned quasi-phase-matching media.

PubMed

Phillips, C R; Mayer, B W; Gallmann, L; Keller, U

2016-07-11

Advances in the amplification and manipulation of ultrashort laser pulses have led to revolutions in several areas. Examples include chirped pulse amplification for generating high peak-power lasers, power-scalable amplification techniques, pulse shaping via modulation of spatially-dispersed laser pulses, and efficient frequency-mixing in quasi-phase-matched nonlinear crystals to access new spectral regions. In this work, we introduce and demonstrate a new platform for nonlinear optics which has the potential to combine these separate functionalities (pulse amplification, frequency transfer, and pulse shaping) into a single monolithic device that is bandwidth- and power-scalable. The approach is based on two-dimensional (2D) patterning of quasi-phase-matching (QPM) gratings combined with optical parametric interactions involving spatially dispersed laser pulses. Our proof of principle experiment demonstrates this technique via mid-infrared optical parametric chirped pulse amplification of few-cycle pulses. Additionally, we present a detailed theoretical and numerical analysis of such 2D-QPM devices and how they can be designed.

Field demonstration of an eight-element fiber laser hydrophone array

NASA Astrophysics Data System (ADS)

Foster, Scott; Tikhomirov, Alexei; Harrison, Joanne; van Velzen, John

2014-05-01

We have developed an 8-element fibre laser seabed array demonstrating state-of-the art performance characteristics for a fibre laser sensing system and highlighting the advantage this technology provides in the underwater sensing domain. The system employs sea-state-zero sensitivity hydrophones with a flat acoustic response over a bandwidth exceeding 5kHz and very low inertial sensitivity. The system contains no outboard electronics and few metal components making it extremely light, compact, and low complexity. The array may be deployed up to 4 km from a land or sea based platform to a depth of up to 80m. Power delivery and telemetry for all 8 sensors is achieved via a single 2mm diameter optical fibre cable weighing less than 5kg per km. We report here results of the first field trials of this system.

Prototype laser-diode-pumped solid state laser transmitters

NASA Technical Reports Server (NTRS)

Kane, Thomas J.; Cheng, Emily A. P.; Wallace, Richard W.

1989-01-01

Monolithic, diode-pumped Nd:YAG ring lasers can provide diffraction-limited, single-frequency, narrow-linewidth, tunable output which is adequate for use as a local oscillator in a coherent communication system. A laser was built which had a linewidth of about 2 kHz, a power of 5 milliwatts, and which was tunable over a range of 30 MHz in a few microseconds. This laser was phase-locked to a second, similar laser. This demonstrates that the powerful technique of heterodyne detection is possible with a diode-pumped laser used as the local oscillator. Laser diode pumping of monolithic Nd:YAG rings can lead to output powers of hundreds of milliwatts from a single laser. A laser was built with a single-mode output of 310 mW. Several lasers can be chained together to sum their power, while maintaining diffraction-limited, single frequency operation. This technique was demonstrated with two lasers, with a total output of 340 mW, and is expected to be practical for up to about ten lasers. Thus with lasers of 310 mW, output of up to 3 W is possible. The chaining technique, if properly engineered, results in redundancy. The technique of resonant external modulation and doubling is designed to efficiently convert the continuous wave, infrared output of our lasers into low duty-cycle pulsed green output. This technique was verified through both computer modeling and experimentation. Further work would be necessary to develop a deliverable system using this technique.

Defining photon channels in strong-field physics: the photon-phase Fourier representation

NASA Astrophysics Data System (ADS)

Zeng, Shuo; Zohrabi, Mohammad; Berry, Ben; Ablikim, Utuq; Kling, Nora; Severt, Travis; Jochim, Bethany; Carnes, Kevin; Ben-Itzhak, Itzik; Esry, Brett

2014-05-01

In strong-field physics, complex atomic and molecular dynamics can be steered by the carrier-envelope phase (CEP). The general theory formulated in Refs., provides a rigorous foundation upon which this understanding might be built. By recognizing the underlying periodicity of the time-dependent Schrödinger equation--and thus its solutions--in the CEP, all CEP effects can be understood as the interference of different photon channels. We will show that this understanding can be turned around to extract information on the photon channel by examining the CEP dependence. In particular, by taking the Fourier transform with respect to the CEP, photon channel information can be extracted from both theory and experiment. Through several examples, we will also show that this technique can be applied to any system and provides knowledge of the net numbers of photons absorbed--even in few-cycle pulses--that is not available in any other way. This work was supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy under Grant No. DE-FG02-86ER13491. The PULSAR laser was provided by Grant No. DE-FG02-09.

Accelerating Into the Future: From 0 to GeV in a Few Centimeters (LBNL Summer Lecture Series)

ScienceCinema

Leemans, Wim [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Accelerator and Fusion Research Division (AFRD) and Laser Optics and Accelerator Systems Integrated Studies (LOASIS)

2018-05-04

Summer Lecture Series 2008: By exciting electric fields in plasma-based waveguides, lasers accelerate electrons in a fraction of the distance conventional accelerators require. The Accelerator and Fusion Research Division's LOASIS program, headed by Wim Leemans, has used 40-trillion-watt laser pulses to deliver billion-electron-volt (1 GeV) electron beams within centimeters. Leemans looks ahead to BELLA, 10-GeV accelerating modules that could power a future linear collider.

Accelerating Into the Future: From 0 to GeV in a Few Centimeters (LBNL Summer Lecture Series)

ScienceCinema

Leemans, Wim [LOASIS Program, AFRD

2017-12-09

July 8, 2008 Berkeley Lab lecture: By exciting electric fields in plasma-based waveguides, lasers accelerate electrons in a fraction of the distance conventional accelerators require. The Accelerator and Fusion Research Division's LOASIS program, headed by Wim Leemans, has used 40-trillion-watt laser pulses to deliver billion-electron-volt (1 GeV) electron beams within centimeters. Leemans looks ahead to BELLA, 10-GeV accelerating modules that could power a future linear collider.

Polar Field Reversals and Active Region Decay

NASA Astrophysics Data System (ADS)

Petrie, Gordon; Ettinger, Sophie

2017-09-01

We study the relationship between polar field reversals and decayed active region magnetic flux. Photospheric active region flux is dispersed by differential rotation and turbulent diffusion, and is transported poleward by meridional flows and diffusion. We summarize the published evidence from observation and modeling of the influence of meridional flow variations and decaying active region flux's spatial distribution, such as the Joy's law tilt angle. Using NSO Kitt Peak synoptic magnetograms covering cycles 21-24, we investigate in detail the relationship between the transport of decayed active region flux to high latitudes and changes in the polar field strength, including reversals in the magnetic polarity at the poles. By means of stack plots of low- and high-latitude slices of the synoptic magnetograms, the dispersal of flux from low to high latitudes is tracked, and the timing of this dispersal is compared to the polar field changes. In the most abrupt cases of polar field reversal, a few activity complexes (systems of active regions) are identified as the main cause. The poleward transport of large quantities of decayed trailing-polarity flux from these complexes is found to correlate well in time with the abrupt polar field changes. In each case, significant latitudinal displacements were found between the positive and negative flux centroids of the complexes, consistent with Joy's law bipole tilt with trailing-polarity flux located poleward of leading-polarity flux. The activity complexes of the cycle 21 and 22 maxima were larger and longer-lived than those of the cycle 23 and 24 maxima, and the poleward surges were stronger and more unipolar and the polar field changes larger and faster. The cycle 21 and 22 polar reversals were dominated by only a few long-lived complexes whereas the cycle 23 and 24 reversals were the cumulative effects of more numerous, shorter-lived regions. We conclude that sizes and lifetimes of activity complexes are key to understanding the diversity of polar reversals.

Progress in coherent laser radar

NASA Technical Reports Server (NTRS)

Vaughan, J. M.

1986-01-01

Considerable progress with coherent laser radar has been made over the last few years, most notably perhaps in the available range of high performance devices and components and the confidence with which systems may now be taken into the field for prolonged periods of operation. Some of this increasing maturity was evident at the 3rd Topical Meeting on Coherent Laser Radar: Technology and Applications. Topics included in discussions were: mesoscale wind fields, nocturnal valley drainage and clear air down bursts; airborne Doppler lidar studies and comparison of ground and airborne wind measurement; wind measurement over the sea for comparison with satellite borne microwave sensors; transport of wake vortices at airfield; coherent DIAL methods; a newly assembled Nd-YAG coherent lidar system; backscatter profiles in the atmosphere and wavelength dependence over the 9 to 11 micrometer region; beam propagation; rock and soil classification with an airborne 4-laser system; technology of a global wind profiling system; target calibration; ranging and imaging with coherent pulsed and CW system; signal fluctuations and speckle. Some of these activities are briefly reviewed.

Electric field-induced coherent control in GaAs: polarization dependence and electrical measurement [Invited].

PubMed

Wahlstrand, J K; Zhang, H; Choi, S B; Sipe, J E; Cundiff, S T

2011-11-07

A static electric field enables coherent control of the photoexcited carrier density in a semiconductor through the interference of one- and two-photon absorption. An experiment using optical detection is described. The polarization dependence of the signal is consistent with a calculation using a 14-band k · p model for GaAs. We also describe an electrical measurement. A strong enhancement of the phase-dependent photocurrent through a metal-semiconductor-metal structure is observed when a bias of a few volts is applied. The dependence of the signal on bias and laser spot position is studied. The field-induced enhancement of the signal could increase the sensitivity of semiconductor-based carrier-envelope phase detectors, useful in stabilizing mode-locked lasers for use in frequency combs.

Single-cycle Optical Pulses and Isolated Attosecond Pulse Generation

DTIC Science & Technology

2012-02-29

picosecond green light from a frequency-doubled hybrid cryogenic Yb:YAG laser system,” 36 UFO /HFSW 2009 (Arcachon, France, Aug. 31-Sept. 4, 2009...High Fields Short Wavelength,” ( UFO VII – HFSW XIII), Arcachon, France, August 31 – September 4, 2009 (invited). 25) Kyung-Han Hong, Juliet Gopinath

Investigating tunneling process of atom exposed in circularly polarized strong-laser field

NASA Astrophysics Data System (ADS)

Yuan, MingHu; Xin, PeiPei; Chu, TianShu; Liu, HongPing

2017-03-01

We propose a method for studying the tunneling process by analyzing the instantaneous ionization rate of a circularly polarized laser. A numerical calculation shows that, for an atom exposed to a long laser pulse, if its initial electronic state wave function is non-spherical symmetric, the delayed phase shift of the ionization rate vs the laser cycle period in real time in the region close to the peak intensity of the laser pulse can be used to probe the tunneling time. In this region, an obvious time delay phase shift of more than 190 attoseconds is observed. Further study shows that the atom has a longer tunneling time in the ionization under a shorter wavelength laser pulse. In our method, a Wigner rotation technique is employed to numerically solve the time-dependent Schrödinger equation of a single-active electron in a three-dimensional spherical coordinate system.

High-energy electron emission from metallic nano-tips driven by intense single-cycle terahertz pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Sha; Jones, R. R.

Electrons ejected from atoms and subsequently driven to high energies in strong laser fields enable techniques from attosecond pulse generation to imaging with rescattered electrons. Analogous processes govern strong-field electron emission from nanostructures, where long wavelength radiation and large local field enhancements hold the promise for producing electrons with substantially higher energies, allowing for higher resolution time-resolved imaging. Here we report on the use of single-cycle terahertz pulses to drive electron emission from unbiased nano-tips. Energies exceeding 5 keV are observed, substantially greater than previously attained at higher drive frequencies. Despite large differences in the magnitude of the respective localmore » fields, we find that the maximum electron energies are only weakly dependent on the tip radius, for 10 nm« less

High-energy electron emission from metallic nano-tips driven by intense single-cycle terahertz pulses

DOE PAGES

Li, Sha; Jones, R. R.

2016-11-10

Electrons ejected from atoms and subsequently driven to high energies in strong laser fields enable techniques from attosecond pulse generation to imaging with rescattered electrons. Analogous processes govern strong-field electron emission from nanostructures, where long wavelength radiation and large local field enhancements hold the promise for producing electrons with substantially higher energies, allowing for higher resolution time-resolved imaging. Here we report on the use of single-cycle terahertz pulses to drive electron emission from unbiased nano-tips. Energies exceeding 5 keV are observed, substantially greater than previously attained at higher drive frequencies. Despite large differences in the magnitude of the respective localmore » fields, we find that the maximum electron energies are only weakly dependent on the tip radius, for 10 nm« less

Electron scattering by molecules. II - Experimental methods and data

NASA Technical Reports Server (NTRS)

Trajmar, S.; Chutjian, A.; Register, D. F.

1983-01-01

Experimental techniques for measuring electron-molecule collision cross sections are briefly summarized. A survey of the available experimental cross section data is presented. The emphasis here is on elastic scattering, rotational, vibrational and electronic excitations, total electron scattering, and momentum transfer in the few eV to few hundred eV impact energy range. Reference is made to works concerned with high energy electron scattering, innershell and multi-electron excitations, conicidence methods and electron scattering in laser fields.

Real-time observation of valence electron motion.

PubMed

Goulielmakis, Eleftherios; Loh, Zhi-Heng; Wirth, Adrian; Santra, Robin; Rohringer, Nina; Yakovlev, Vladislav S; Zherebtsov, Sergey; Pfeifer, Thomas; Azzeer, Abdallah M; Kling, Matthias F; Leone, Stephen R; Krausz, Ferenc

2010-08-05

The superposition of quantum states drives motion on the atomic and subatomic scales, with the energy spacing of the states dictating the speed of the motion. In the case of electrons residing in the outer (valence) shells of atoms and molecules which are separated by electronvolt energies, this means that valence electron motion occurs on a subfemtosecond to few-femtosecond timescale (1 fs = 10(-15) s). In the absence of complete measurements, the motion can be characterized in terms of a complex quantity, the density matrix. Here we report an attosecond pump-probe measurement of the density matrix of valence electrons in atomic krypton ions. We generate the ions with a controlled few-cycle laser field and then probe them through the spectrally resolved absorption of an attosecond extreme-ultraviolet pulse, which allows us to observe in real time the subfemtosecond motion of valence electrons over a multifemtosecond time span. We are able to completely characterize the quantum mechanical electron motion and determine its degree of coherence in the specimen of the ensemble. Although the present study uses a simple, prototypical open system, attosecond transient absorption spectroscopy should be applicable to molecules and solid-state materials to reveal the elementary electron motions that control physical, chemical and biological properties and processes.

Designing and testing a laser-based vibratory sensor

NASA Astrophysics Data System (ADS)

Nath, G.

2018-04-01

Sensor technology has proved its importance, not only in the range of few-meter applications in different fields, but in micro, nano, atomic and sub-atomic-sized objects. The present work describes the designing of a laser-based vibratory sensor using a He-Ne laser as the signal source. The received characteristics of the signal are mainly the frequency and amplitude of the vibration from which the physical parameters such as energy, power and absorption coefficients of the material are determined, which enables us to provide information of the hidden target or object. This laboratory-designed sensor finds application in different local phenomena as well as laboratory practical activity for students.

Frequency modulation of high-order harmonic generation in an orthogonally polarized two-color laser field.

PubMed

Li, Guicun; Zheng, Yinghui; Ge, Xiaochun; Zeng, Zhinan; Li, Ruxin

2016-08-08

We have experimentally investigated the frequency modulation of high-order harmonics in an orthogonally polarized two-color laser field consisting of a mid-infrared 1800nm fundamental pulse and its second harmonic pulse. It is demonstrated that the high harmonic spectra can be fine-tuned as we slightly change the relative delay of the two-color laser pulses. By analyzing the relative frequency shift of each harmonic at different two-color delays, the nonadiabatic spectral shift induced by the rapid variation of the intensity-dependent intrinsic dipole phase can be distinguished from the blueshift induced by the change of the refractive index during self-phase modulation (SPM). Our comprehensive analysis shows that the frequency modulation pattern is a reflection of the average emission time of high-order harmonic generation (HHG), thus offering a simple method to fine-tune the spectra of the harmonics on a sub-cycle time scale.

Applications of laser-induced periodic surface structures (LIPSS)

NASA Astrophysics Data System (ADS)

Bonse, Jörn; Kirner, Sabrina V.; Höhm, Sandra; Epperlein, Nadja; Spaltmann, Dirk; Rosenfeld, Arkadi; Krüger, Jörg

2017-02-01

Laser-induced periodic surface structures (LIPSS, ripples) are a universal phenomenon that can be observed on almost any material after the irradiation by linearly polarized laser beams, particularly when using ultrashort laser pulses with durations in the picosecond to femtosecond range. During the past few years significantly increasing research activities have been reported in the field of LIPSS, since their generation in a single-step process provides a simple way of nanostructuring and surface functionalization towards the control of optical, mechanical or chemical properties. In this contribution current applications of LIPSS are reviewed, including the colorization of technical surfaces, the control of surface wetting, the tailoring of surface colonization by bacterial biofilms, and the improvement of the tribological performance of nanostructured metal surfaces.

Generation of single attosecond pulse within one atomic unit by using multi-cycle inhomogeneous polarization gating technology in bowtie-shaped nanostructure

NASA Astrophysics Data System (ADS)

Feng, Liqiang; Liu, Hang

2018-04-01

The generations of high-order harmonic spectra and single attosecond pulses (SAPs) driven by the multi-cycle inhomogeneous polarization gating (PG) technology in the bowtie-shaped nanostructure have been theoretically investigated. It is found that by setting the bowtie-shaped nanostructure along the driven laser polarization direction, not only the extension of the harmonic cutoff can be achieved, caused by the surface plasmon polaritons, but also the modulations of the harmonics can be decreased, caused by the PG technology and the inhomogeneous effect. As a result, the contribution of the harmonic plateau is only from one harmonic emission peak with the dominant short quantum path. Further, by properly adding a half-cycle pulse into the driven laser field, the harmonic emission process can be precisely controlled in the half-cycle duration and a supercontinuum with the bandwidth of 263 eV can be obtained. Finally, by directly superposing the harmonics from this supercontinuum, a SAP with the full width at half maximum of 23 as can be obtained, which is shorter than one atomic unit.

Solid hydrogen target for laser driven proton acceleration

NASA Astrophysics Data System (ADS)

Perin, J. P.; Garcia, S.; Chatain, D.; Margarone, D.

2015-05-01

The development of very high power lasers opens up new horizons in various fields, such as laser plasma acceleration in Physics and innovative approaches for proton therapy in Medicine. Laser driven proton acceleration is commonly based on the so-called Target Normal Sheath Acceleration (TNSA) mechanisms: a high power laser is focused onto a solid target (thin metallic or plastic foil) and interact with matter at very high intensity, thus generating a plasma; as a consequence "hot" electrons are produced and move into the forward direction through the target. Protons are generated at the target rear side, electrons try to escape from the target and an ultra-strong quasi-electrostatic field (~1TV/m) is generated. Such a field can accelerate protons with a wide energy spectrum (1-200 MeV) in a few tens of micrometers. The proton beam characteristics depend on the laser parameters and on the target geometry and nature. This technique has been validated experimentally in several high power laser facilities by accelerating protons coming from hydrogenated contaminant (mainly water) at the rear of metallic target, however, several research groups are investigating the possibility to perform experiments by using "pure" hydrogen targets. In this context, the low temperature laboratory at CEA-Grenoble has developed a cryostat able to continuously produce a thin hydrogen ribbon (from 40 to 100 microns thick). A new extrusion concept, without any moving part has been carried out, using only the thermodynamic properties of the fluid. First results and perspectives are presented in this paper.

Remote monitoring of the earthquake cycle using satellite radar interferometry.

PubMed

Wright, Tim J

2002-12-15

The earthquake cycle is poorly understood. Earthquakes continue to occur on previously unrecognized faults. Earthquake prediction seems impossible. These remain the facts despite nearly 100 years of intensive study since the earthquake cycle was first conceptualized. Using data acquired from satellites in orbit 800 km above the Earth, a new technique, radar interferometry (InSAR), has the potential to solve these problems. For the first time, detailed maps of the warping of the Earth's surface during the earthquake cycle can be obtained with a spatial resolution of a few tens of metres and a precision of a few millimetres. InSAR does not need equipment on the ground or expensive field campaigns, so it can gather crucial data on earthquakes and the seismic cycle from some of the remotest areas of the planet. In this article, I review some of the remarkable observations of the earthquake cycle already made using radar interferometry and speculate on breakthroughs that are tantalizingly close.

Ytterbium-doped fiber laser passively mode locked by few-layer Molybdenum Disulfide (MoS2) saturable absorber functioned with evanescent field interaction

PubMed Central

Du, Juan; Wang, Qingkai; Jiang, Guobao; Xu, Changwen; Zhao, Chujun; Xiang, Yuanjiang; Chen, Yu; Wen, Shuangchun; Zhang, Han

2014-01-01

By coupling few-layer Molybdenum Disulfide (MoS2) with fiber-taper evanescent light field, a new type of MoS2 based nonlinear optical modulating element had been successfully fabricated as a two-dimensional layered saturable absorber with strong light-matter interaction. This MoS2-taper-fiber device is not only capable of passively mode-locking an all-normal-dispersion ytterbium-doped fiber laser and enduring high power laser excitation (up to 1 W), but also functions as a polarization sensitive optical modulating component (that is, different polarized light can induce different nonlinear optical response). Thanks to the combined advantages from the strong nonlinear optical response in MoS2 together with the sufficiently-long-range interaction between light and MoS2, this device allows for the generation of high power stable dissipative solitons at 1042.6 nm with pulse duration of 656 ps and a repetition rate of 6.74 MHz at a pump power of 210 mW. Our work may also constitute the first example of MoS2-enabled wave-guiding photonic device, and potentially give some new insights into two-dimensional layered materials related photonics. PMID:25213108

Ultrafast monoenergetic electron source by optical waveform control of surface plasmons.

PubMed

Dombi, Péter; Rácz, Péter

2008-03-03

We propose coherent control of photoelectron acceleration at metal surfaces mediated by surface plasmon polaritons. A high degree of spectral and spatial control of the emission process can be exercised by amplitude and phase controlling the optical waveform (including the carrier-envelope phase) of the plasmon generating few-cycle laser pulse. Numerical results show that the emitted electron beam is highly directional and monoenergetic suggesting applications in contemporary ultrafast methods where ultrashort, well-behaved electron pulses are required.

Molybdenum oxide nanocolloids prepared by an external field-assisted laser ablation in water

NASA Astrophysics Data System (ADS)

Spadaro, Salvatore; Bonsignore, Martina; Fazio, Enza; Cimino, Francesco; Speciale, Antonio; Trombetta, Domenico; Barreca, Francesco; Saija, Antonina; Neri, Fortunato

2018-01-01

he synthesis of extremely stable molybdenum oxide nanocolloids by pulsed laser ablation was studied. This green technique ensures the formation of contaminant-free nanostructures and the absence of by-products. A focused picosecond pulsed laser beam was used to ablate a solid molybdenum target immersed in deionized water. Molybdenum oxide nearly spherical nanoparticles with dimensions within few nanometers (20-100 nm) are synthesized when the ablation processes were carried out, in water, at room temperature and 80°C. The application of an external electric field during the ablation process induces a nanostructures reorganization, as indicated by Scanning-Transmission Electron Microscopy images analysis. The ablation products were also characterized by some spectroscopic techniques: conventional UV-vis optical absorption, atomic absorption, dynamic light scattering, micro-Raman and X-ray photoelectron spectroscopies. Finally, NIH/3T3 mouse fibroblasts were used to evaluate cell viability by the sulforhodamine B assay

Dependence of sodium laser guide star photon return on the geomagnetic field

NASA Astrophysics Data System (ADS)

Moussaoui, N.; Holzlöhner, R.; Hackenberg, W.; Bonaccini Calia, D.

2009-07-01

Aims: The efficiency of optical pumping that increases the backscatter emission of mesospheric sodium atoms in continuous wave (cw) laser guide stars (LGSs) can be significantly reduced and, in the worst case, eliminated by the action of the geomagnetic field. Our goal is to present an estimation of this effect for several telescope sites. Methods: Sodium atoms precess around magnetic field lines that cycle the magnetic quantum number, reducing the effectiveness of optical pumping. Our method is based on calculating the sodium magnetic sublevel populations in the presence of the geomagnetic field and on experimental measurements of radiance return from sodium LGS conducted at the Starfire optical range (SOR). Results: We propose a relatively simple semi-empirical formula for estimating the effect of the geomagnetic field on enhancing the LGSs photon return due to optical pumping with a circularly polarized cw single-frequency laser beam. Starting from the good agreement between our calculations and the experimental measurements for the geomagnetic field effect, and in order to more realistically estimate the sodium LGSs photon return, we introduce the effect of the distance to the mesospheric sodium layer and the atmospheric attenuation. The combined effect of these three factors is calculated for several telescope sites. Conclusions: In calculating the return flux of LGSs, only the best return conditions are often assumed, relying on strong optical pumping with circularly polarized lasers. However, one can only obtain this optimal return along one specific laser orientation on the sky, where the geomagnetic field lines are parallel to the laser beam. For most of the telescopes, the optimum can be obtained at telescope orientations beyond the observation limit. For the telescopes located close to the geomagnetic pole, the benefit of the optical pumping is much more important than for telescopes located close to the geomagnetic equator.

Key optical components for spaceborne lasers

NASA Astrophysics Data System (ADS)

Löhring, J.; Winzen, M.; Faidel, H.; Miesner, J.; Plum, D.; Klein, J.; Fitzau, O.; Giesberts, M.; Brandenburg, W.; Seidel, A.; Schwanen, N.; Riesters, D.; Hengesbach, S.; Hoffmann, H.-D.

2016-03-01

Spaceborne lidar (light detection and ranging) systems have a large potential to become powerful instruments in the field of atmospheric research. Obviously, they have to be in operation for about three years without any maintenance like readjusting. Furthermore, they have to withstand strong temperature cycles typically in the range of -30 to +50 °C as well as mechanical shocks and vibrations, especially during launch. Additionally, the avoidance of any organic material inside the laser box is required, particularly in UV lasers. For atmospheric research pulses of about several 10 mJ at repetition rates of several 10 Hz are required in many cases. Those parameters are typically addressed by DPSSL that comprise components like: laser crystals, nonlinear crystals in pockels cells, faraday isolators and frequency converters, passive fibers, diode lasers and of course a lot of mirrors and lenses. In particular, some components have strong requirements regarding their tilt stability that is often in the 10 μrad range. In most of the cases components and packages that are used for industrial lasers do not fulfil all those requirements. Thus, the packaging of all these key components has been developed to meet those specifications only making use of metal and ceramics beside the optical component itself. All joints between the optical component and the laser baseplate are soldered or screwed. No clamps or adhesives are used. Most of the critical properties like tilting after temperature cycling have been proven in several tests. Currently, these components are used to build up first prototypes for spaceborne systems.

A real-time multi-gases detection and concentration measurements based-on time-division multiplexed-lasers

NASA Astrophysics Data System (ADS)

Yazdandoust, Fatemeh; Tatenguem Fankem, Hervé; Milde, Tobias; Jimenez, Alvaro; Sacher, Joachim

2018-02-01

We report the development of a platform, based-on a Field-Programmable Gate Arrays (FPGAs) and suitable for Time-Division-Multiplexed DFB lasers. The designed platform is subsequently combined with a spectroscopy setup, for detection and quantification of species in a gas mixture. The experimental results show a detection limit of 460 ppm, an uncertainty of 0.1% and a computation time of less than 1000 clock cycles. The proposed system offers a high level of flexibility and is applicable to arbitrary types of gas-mixtures.

Measurement of electromagnetic pulses generated during interactions of high power lasers with solid targets

NASA Astrophysics Data System (ADS)

De Marco, M.; Krása, J.; Cikhardt, J.; Pfeifer, M.; Krouský, E.; Margarone, D.; Ahmed, H.; Borghesi, M.; Kar, S.; Giuffrida, L.; Vrana, R.; Velyhan, A.; Limpouch, J.; Korn, G.; Weber, S.; Velardi, L.; Delle Side, D.; Nassisi, V.; Ullschmied, J.

2016-06-01

A target irradiated with a high power laser pulse, blows off a large amount of charge and as a consequence the target itself becomes a generator of electromagnetic pulses (EMP) owing to high return current flowing to the ground through the target holder. The first measurement of the magnetic field induced by the neutralizing current reaching a value of a few kA was performed with the use of an inductive target probe at the PALS Laser Facility (Cikhardt et al. Rev. Sci. Instrum. 85 (2014) 103507). A full description of EMP generation should contain information on the spatial distribution and temporal variation of the electromagnetic field inside and outside of the interaction chamber. For this reason, we consider the interaction chamber as a resonant cavity in which different modes of EMP oscillate for hundreds of nanoseconds, until the EMP is transmitted outside through the glass windows and EM waves are attenuated. Since the experimental determination of the electromagnetic field distribution is limited by the number of employed antennas, a mapping of the electromagnetic field has to be integrated with numerical simulations. Thus, this work reports on a detailed numerical mapping of the electromagnetic field inside the interaction chamber at the PALS Laser Facility (covering a frequency spectrum from 100 MHz to 3 GHz) using the commercial code COMSOL Multiphysics 5.2. Moreover we carried out a comparison of the EMP generated in the parallelepiped-like interaction chamber used in the Vulcan Petawatt Laser Facility at the Rutherford Appleton Laboratory, against that produced in the spherical interaction chamber of PALS.

New generation attosecond light sources

NASA Astrophysics Data System (ADS)

Chang, Zenghu

2017-04-01

Millijoule level, few-cycle, carrier-envelope phase (CEP) stable Ti:Sapphire lasers centered at 800 nm have been the workhorse for the first generation attosecond light sources in the last 16 years. The spectral range of isolated attosecond pulses with sufficient photon flux for time-resolved pump-probe experiments has been limited to extreme ultraviolet (10 to 150 eV). The shortest pulses achieved are 67 as. It was demonstrated in 2001 that the cutoff photon energy of the high harmonic spectrum could be extended by increasing the center wavelength of the driving lasers. In recent years, mJ level, two-cycle, carrier-envelope phase stabilized lasers at 1.6 to 2.1 micron have been developed by implementing Optical Parametric Chirped Pulse Amplification (OPCPA) techniques. Recently, when long wavelength driving was combined with polarization gating, isolated soft x-rays in the water window (280-530 eV) were generated in our laboratory. The number of x-ray photons in the 120-400 eV range is comparable to that generated with Ti:Sapphire lasers in the 50 to 150 eV range. The ultrabroadband isolated x-ray pulses with 53 as duration were characterized by attosecond streaking measurements. The new generation attosecond soft X-ray sources open the door for studying electron dynamics with element specificity through core to valence transitions. NSF (1068604), ARO (W911NF-14-1-0383), AFOSR (FA9550-15-1-0037, FA9550-16-1-0013), DARPA-PULSE (W31P4Q1310017).

Study, optimization, and design of a laser heat engine. [for satellite applications

NASA Technical Reports Server (NTRS)

Taussig, R. T.; Cassady, P. E.; Zumdieck, J. F.

1978-01-01

Laser heat engine concepts, proposed for satellite applications, are analyzed to determine which engine concept best meets the requirements of high efficiency (50 percent or better), continuous operation in space using near-term technology. The analysis of laser heat engines includes the thermodynamic cycles, engine design, laser power sources, collector/concentrator optics, receiving windows, absorbers, working fluids, electricity generation, and heat rejection. Specific engine concepts, optimized according to thermal efficiency, are rated by their technological availability and scaling to higher powers. A near-term experimental demonstration of the laser heat engine concept appears feasible utilizing an Otto cycle powered by CO2 laser radiation coupled into the engine through a diamond window. Higher cycle temperatures, higher efficiencies, and scalability to larger sizes appear to be achievable from a laser heat engine design based on the Brayton cycle and powered by a CO laser.

Preliminary Investigation on Life Cycle Inventory of Powder Bed Fusion of Stainless Steel

NASA Astrophysics Data System (ADS)

Nyamekye, Patricia; Piili, Heidi; Leino, Maija; Salminen, Antti

Manufacturing of work pieces from stainless steel with laser additive manufacturing, known also as laser sintering or 3D printing may increase energy and material efficiency. The use of powder bed fusion offers advantages to make parts for dynamic applications of light weight and near-net-shape products. Due to these advantages among others, PBF may also reduce emissions and operational cost in various applications. However, there are only few life cycle assessment studies examining this subject despite its prospect to business opportunity. The application of Life Cycle Inventory (LCI) in Powder Bed Fusion (PBF) provides a distinct evaluation of material and energy consumption. LCI offers a possibility to improve knowledge of process efficiency. This study investigates effect of process sustainability in terms of raw material, energy and time consumption with PBF and CNC machining. The results of the experimental study indicated lower energy efficiency in the production process with PBF. This study revealed that specific energy consumption in PBF decreased when several components are built simultaneously than if they would be built individually. This is due to fact that energy consumption per part is lower. On the contrary, amount of energy needed to machine on part in case of CNC machining is lower when parts are done separately.

Connecting Lab-Based Attosecond Science with FEL research

ScienceCinema

Vrakking, Marc

2017-12-09

In the last few years laboratory-scale femtosecond laser-based research using XUV light has developed dramatically following the successful development of attosecond laser pulses by means of high-harmonic generation. Using attosecond laser pulses, studies of electron dynamics on the natural timescale that electronic processes occur in atoms, molecules and solids can be contemplated, providing unprecedented insight into the fundamental role that electrons play in photo-induced processes. In my talk I will briefly review the present status of the attosecond science research field in terms of present and foreseen capabilities, and discuss a few recent applications, including a first example of the use of attosecond laser pulses in molecular science. In addition, I will discuss very recent results of experiments where photoionization of dynamically aligned molecules is investigated using a high-harmonics XUV source. Photoionization of aligned molecules becomes all the more interesting if the experiment is performed using x-ray photons. Following the absorption of x-rays, ejected photoelectrons can be used as a probe of the (time-evolving) molecular structure, making use of intra-molecular electron diffraction. This amounts, as some have stated, to “illuminating the molecule from within”. I will present the present status of our experiments on this topic making use of the FLASH free electron laser in Hamburg. Future progress in this research field not only depends on the availability of better and more powerful light sources, but also requires sophisticated detector strategies. In my talk I will explain how we are trying to meet some of the experimental challenges by using the Medipix family of detectors, which we have already used for time- and space-resolved imaging of electrons and ions.

Femtosecond synchronism of x-rays and visible/infrared light in an x-ray free-electron laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adams, B. W.

2007-12-15

A way is proposed to obtain ultrashort pulses of intense infrared/visible light in few-femtosecond synchronism with x-rays from an x-ray free-electron laser (XFEL). It makes use of the recently proposed emittance-slicing technique [Emma et al., Phys. Rev. Lett. 92, 074801 (2004)] to both restrict the duration of self-amplified spontaneous emission (SASE) to a few femtoseconds and to lead to a coherence enhancement of near-infrared transition undulator radiation (CTUR). The x-rays and the near-infrared light originate within the XFEL undulator from the same slice of electrons within a bunch and are therefore perfectly synchronized with each other. An example of realizingmore » the scheme at the Linac Coherent Light Source is presented. A few side issues are explored briefly, such as the magnitude of the velocity term versus the acceleration term in the Lienard-Wiechert fields and the possible use of the CTUR as a diagnostic tool for the SASE process itself.« less

Research on Vacuum Laser Accelerator and Proof-of Principle Experiment

NASA Astrophysics Data System (ADS)

Shao, Lei

This thesis discovers a proof-of-principle theory of Vacuum Laser Acceleration (VLA) and proposes a new acceleration mechanism---Capture and Acceleration Scenario (CAS) in our far-field laser acceleration research, which is a promising new scheme in advanced acceleration field. In this thesis, I studied electrons' dynamic behaviors while interacting with intense laser beam. There are two kinds of dynamics trajectories, namely IS (Inelastic Scattering) and CAS. In CAS, electrons can be captured and moving along the laser beam for a long time and receive considerable energy exchange from the laser field, rather than quickly expelled from the intense field region of the laser as predicted by the conventional Ponderomotive Potential Model (PPM). This thesis shows the research on most parameters of both laser beam and electron beam which will affect this VLA scheme. One of the primary factors is the laser intensity. Relatively high laser intensity is critically required for VLA, and there are thresholds of intensity a0( th) for CAS occurrence; the thresholds are different under different laser beam waist widths which is also a very important parameter of laser beam. Laser intensity is still a big obstacle nowadays. In the last decade there are only a few laboratories have the laser power to ˜1019 W/cm2 and above. Our simulation shows that laser intensity threshold of CAS is around a0 = 5˜8, in correspondence to laser power around 1019˜1022 W/cm 2 depending on different wave length and waist width. The interaction is also sensitive to various electron beam parameters, such as the optimal initial electron energy falls in the range of 4--15 MeV, electron incident angle and position, and so on. At last the thesis presents out experimental work on this new VLA scheme. The collaboration is between our UCLA group and Brookhaven National Lab - Accelerator Test Facility (BNL-ATF). At BNL-ATF, they have both intense laser beam and high quality electron beam. The characters of BNL-ATF fit our project very well. The laser system at ATF is a short pulse CO2 laser. Under present ATF condition, the peak power of the CO2 laser is around 5J with pulse duration 5ps. Therefore the maximum laser intensity can reach a 0 ≈ 1.0. Such level of laser intensity is not sufficient to perform violent electron acceleration-CAS according to the threshold we defined. However this level intensity is already high enough to see basic proof-of-principle signal based on our extensive simulations with exact practical ATF experimental conditions. Another important factor is the electron beam condition. ATF uses photoinjector Radio Frequency (RF) gun system for electron beam. The working frequency is at constant level 2856MHz. Generally the electron beam deliver energy around 40MeV˜60MeV to the transport beam line. However as we mentioned before with relatively low laser intensity the electron initial energy is required to be lower as well correspondently. We tried best to tuned ATF electron beam energy down to 15MeV. With laser intensity around a 0 ≈ 1.0 and electron beam 15MeV, our simulation indicates to see energy spread expansion after interaction, and this effect increases while the laser intensity increases (even slightly change from a 0 ≈ 0.9 to 2.2). The experiment design is completed based on ATF beam line condition. The design and layout are presented. All the optical devices are acquired and machined. Installation and alignment have been done a few times for testing. (Abstract shortened by UMI.)

Novel target design for enhanced laser driven proton acceleration

NASA Astrophysics Data System (ADS)

Dalui, Malay; Kundu, M.; Tata, Sheroy; Lad, Amit D.; Jha, J.; Ray, Krishanu; Krishnamurthy, M.

2017-09-01

We demonstrate a simple method of preparing structured target for enhanced laser-driven proton acceleration under target-normal-sheath-acceleration scheme. A few layers of genetically modified, clinically grown micron sized E. Coli bacteria cell coated on a thin metal foil has resulted in an increase in the maximum proton energy by about 1.5 times and the total proton yield is enhanced by approximately 25 times compared to an unstructured reference foil at a laser intensity of 1019 W/cm2. Particle-in-cell simulations on the system shows that the structures on the target-foil facilitates anharmonic resonance, contributing to enhanced hot electron production which leads to stronger accelerating field. The effect is observed to grow as the number of structures is increased in the focal area of the laser pulse.

Wake profile measurements of fixed and oscillating flaps

NASA Technical Reports Server (NTRS)

Owen, F. K.

1984-01-01

Although the potential of laser velocimetry for the non-intrusive measurement of complex shear flows has long been recognized, there have been few applications in other small, closely controlled laboratory situations. Measurements in large scale, high speed wind tunnels are still a complex task. To support a study of periodic flows produced by an oscillating edge flap in the Ames eleven foot wind tunnel, this study was done. The potential for laser velocimeter measurements in large scale production facilities are evaluated. The results with hot wire flow field measurements are compared.

Why plasma harmonics?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganeev, R A

We discuss the emergence of interest in the high-order harmonic generation (HHG) of ultrashort pulses propagated through laser-produced plasmas. It is shown that, during the last few years, substantial amendments of plasma HHG allowed in some cases the characteristics of gas HHG to be surpassed. The attractiveness of a new approach in coherent extreme ultraviolet radiation generation is demonstrated, which can also be used as a tool for laser-ablation-induced HHG spectroscopy of a giant class of solids. We present general ideas and prospects for this relatively new field of nonlinear optics. (review)

Parametric study of transport beam lines for electron beams accelerated by laser-plasma interaction

NASA Astrophysics Data System (ADS)

Scisciò, M.; Lancia, L.; Migliorati, M.; Mostacci, A.; Palumbo, L.; Papaphilippou, Y.; Antici, P.

2016-03-01

In the last decade, laser-plasma acceleration of high-energy electrons has attracted strong attention in different fields. Electrons with maximum energies in the GeV range can be laser-accelerated within a few cm using multi-hundreds terawatt (TW) lasers, yielding to very high beam currents at the source (electron bunches with up to tens-hundreds of pC in a few fs). While initially the challenge was to increase the maximum achievable electron energy, today strong effort is put in the control and usability of these laser-generated beams that still lack of some features in order to be used for applications where currently conventional, radio-frequency (RF) based, electron beam lines represent the most common and efficient solution. Several improvements have been suggested for this purpose, some of them acting directly on the plasma source, some using beam shaping tools located downstream. Concerning the latter, several studies have suggested the use of conventional accelerator magnetic devices (such as quadrupoles and solenoids) as an easy implementable solution when the laser-plasma accelerated beam requires optimization. In this paper, we report on a parametric study related to the transport of electron beams accelerated by laser-plasma interaction, using conventional accelerator elements and tools. We focus on both, high energy electron beams in the GeV range, as produced on petawatt (PW) class laser systems, and on lower energy electron beams in the hundreds of MeV range, as nowadays routinely obtained on commercially available multi-hundred TW laser systems. For both scenarios, our study allows understanding what are the crucial parameters that enable laser-plasma accelerators to compete with conventional ones and allow for a beam transport. We show that suitable working points require a tradeoff-combination between low beam divergence and narrow energy spread.

Multielectron effects in the photoelectron momentum distribution of noble-gas atoms driven by visible-to-infrared-frequency laser pulses: A time-dependent density-functional-theory approach

NASA Astrophysics Data System (ADS)

Murakami, Mitsuko; Zhang, G. P.; Chu, Shih-I.

2017-05-01

We present the photoelectron momentum distributions (PMDs) of helium, neon, and argon atoms driven by a linearly polarized, visible (527-nm) or near-infrared (800-nm) laser pulse (20 optical cycles in duration) based on the time-dependent density-functional theory (TDDFT) under the local-density approximation with a self-interaction correction. A set of time-dependent Kohn-Sham equations for all electrons in an atom is numerically solved using the generalized pseudospectral method. An effect of the electron-electron interaction driven by a visible laser field is not recognizable in the helium and neon PMDs except for a reduction of the overall photoelectron yield, but there is a clear difference between the PMDs of an argon atom calculated with the frozen-core approximation and TDDFT, indicating an interference of its M -shell wave functions during the ionization. Furthermore, we find that the PMDs of degenerate p states are well separated in intensity when driven by a near-infrared laser field, so that the single-active-electron approximation can be adopted safely.

Intensity distributions and isolated attosecond pulse generation from molecular high-order harmonic generation in H2+ driven by nonhomogeneous field

NASA Astrophysics Data System (ADS)

Feng, Liqiang; Chu, Tianshu

2017-10-01

Intensity distributions and isolated attosecond pulse generation from the molecular high-order harmonic generation (MHHG) in H2+ and T2+ driven by the nonhomogeneous field have been theoretically investigated. (i) Generally speaking, the intensities of the harmonics driven by the homogeneous field can be enhanced as the initial vibrational state increases and much more intense harmonics can be obtained from the light nuclei. However, with the introduction of the nonhomogeneous effect, the enhanced ratios of the harmonic yields are decreased as the initial vibrational state increases. Moreover, the intensities of the harmonics from H2+ and T2+ are very sensitive to the nonhomogeneous effect of the laser field. (ii) The contributions of the MHHG from the two-H nuclei present the periodic variation as a function of the laser phase for the case of the symmetric nonhomogeneous field. However, for the case of the positive and the negative asymmetric nonhomogeneous fields, the left-H and the right-H play the dominating role in the MHHG, respectively. Moreover, as the angle between the laser polarization direction and the molecular axis increases, the intensity differences of the harmonics from the two-H nuclei are increased. (iii) By properly adding a half-cycle pulse into the positive asymmetric nonhomogeneous field, a supercontinuum with the bandwidth of 279 eV and an isolated 25 as pulse can be obtained.

Fabrication and local laser heating of freestanding Ni{sub 80}Fe{sub 20} bridges with Pt contacts displaying anisotropic magnetoresistance and anomalous Nernst effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandl, F.; Grundler, D., E-mail: grundler@ph.tum.de

2014-04-28

In spin caloritronics, ferromagnetic samples subject to relatively large in-plane temperature gradients ∇T have turned out to be extremely interesting. We report on a preparation technique that allows us to create freely suspended permalloy/Pt hybrid structures where a scanning laser induces ∇T on the order of a few K/μm. We observe both the anisotropic magnetoresistance at room temperature and the magnetic field dependent anomalous Nernst effect under laser heating. The technique is promising for the realization of device concepts considered in spin caloritronics based on suspended ferromagnetic nanostructures with electrical contacts.

Investigation of the High-Cycle Fatigue Life of Selective Laser Melted and Hot Isostatically Pressed Ti-6Al-4v

DTIC Science & Technology

2015-03-26

INVESTIGATION OF THE HIGH -CYCLE FATIGUE LIFE OF SELECTIVE LASER MELTED AND HOT ISOSTATICALLY PRESSED TI-6AL-4V THESIS Kevin D. Rekedal...ENY-MS-15-M-212 INVESTIGATION OF THE HIGH -CYCLE FATIGUE LIFE OF SELECTIVE LASER MELTED AND HOT ISOSTATICALLY PRESSED TI-6AL-4V THESIS...AFIT-ENY-MS-15-M-212 INVESTIGATION OF THE HIGH -CYCLE FATIGUE LIFE OF SELECTIVE LASER MELTED AND HOT ISOSTATICALLY PRESSED TI-6AL-4V

Application of optical interferometry in focused acoustic field measurement

NASA Astrophysics Data System (ADS)

Wang, Yuebing; Sun, Min; Cao, Yonggang; Zhu, Jiang

2018-07-01

Optical interferometry has been successfully applied in measuring acoustic pressures in plane-wave fields and spherical-wave fields. In this paper, the "effective" refractive index for focused acoustic fields was developed, through numerical simulation and experiments, the feasibility of the optical method in measuring acoustic fields of focused transducers was proved. Compared with the results from a membrane hydrophone, it was concluded that the optical method has good spatial resolution and is suitable for detecting focused fields with fluctuant distributions. The influences of a few factors (the generated lamb wave, laser beam directivity, etc.) were analyzed, and corresponding suggestions were proposed for effective application of this technology.

Design of catalytic monoliths for closed-cycle carbon dioxide lasers

NASA Technical Reports Server (NTRS)

Herz, R. K.; Guinn, K.; Goldblum, S.; Noskowski, E.

1989-01-01

Pulsed carbon dioxide (CO2) lasers have many applications in aeronautics, space research, weather monitoring and other areas. Full exploitation of the potential of these lasers in hampered by the dissociation of CO2 that occurs during laser operation. The development of closed-cycle CO2 lasers requires active CO-O2 recombination (CO oxidation) catalyst and design methods for implementation of catalysts in CO2 laser systems. A monolith catalyst section model and associated design computer program, LASCAT, are presented to assist in the design of a monolith catalyst section of a closed cycle CO2 laser system. Using LASCAT,the designer is able to specify a number of system parameters and determine the monolith section performance. Trade-offs between the catalyst activity, catalyst dimensions, monolith dimensions, pressure drop, O2 conversion, and other variables can be explored and adjusted to meet system design specifications. An introduction describes a typical closed-cycle CO2 system, and indicates some advantages of a closed cycle laser system over an open cycle system and some advantages of monolith support over other types of supports. The development and use of a monolith catalyst model is presented. The results of a design study and a discussion of general design rules are given.

Apparatus and method for pulsed laser deposition of materials on wires and pipes

DOEpatents

Fernandez, Felix E.

2003-01-01

Methods and apparatuses are disclosed which allow uniform coatings to be applied by pulsed laser deposition (PLD) on inner and outer surfaces of cylindrical objects, such as rods, pipes, tubes, and wires. The use of PLD makes this technique particularly suitable for complex multicomponent materials, such as superconducting ceramics. Rigid objects of any length, i.e., pipes up to a few meters, and with diameters from less than 1 centimeter to over 10 centimeters can be coated using this technique. Further, deposition is effected simultaneously onto an annular region of the pipe wall. This particular arrangement simplifies the apparatus, reduces film uniformity control difficulties, and can result in faster operation cycles. In addition, flexible wires of any length can be continuously coated using the disclosed invention.

Performance of one hundred watt HVM LPP-EUV source

NASA Astrophysics Data System (ADS)

Mizoguchi, Hakaru; Nakarai, Hiroaki; Abe, Tamotsu; Nowak, Krzysztof M.; Kawasuji, Yasufumi; Tanaka, Hiroshi; Watanabe, Yukio; Hori, Tsukasa; Kodama, Takeshi; Shiraishi, Yutaka; Yanagida, Tatsuya; Soumagne, Georg; Yamada, Tsuyoshi; Yamazaki, Taku; Okazaki, Shinji; Saitou, Takashi

2015-03-01

We have been developing CO2-Sn-LPP EUV light source which is the most promising solution as the 13.5nm high power light source for HVM EUVL. Unique and original technologies such as: combination of pulsed CO2 laser and Sn droplets, dual wavelength laser pulses shooting, and mitigation with magnetic field, have been developed in Gigaphoton Inc. The theoretical and experimental data have clearly showed the advantage of our proposed strategy. Based on these data we are developing first practical source for HVM - "GL200E". This data means 250W EUV power will be able to realize around 20kW level pulsed CO2 laser. We have reported engineering data from our recent test such around 43W average clean power, CE=2.0%, with 100kHz operation and other data 19). We have already finished preparation of higher average power CO2 laser more than 20kW at output power cooperate with Mitsubishi Electric Corporation 14). Recently we achieved 92W with 50kHz, 50% duty cycle operation 20). We have reported component technology progress of EUV light source system. We report promising experimental data and result of simulation of magnetic mitigation system in Proto #1 system. We demonstrated several data with Proto #2 system: (1) emission data of 140W in burst under 70kHz 50% duty cycle during 10 minutes. (2) emission data of 118W in burst under 60kHz 70% duty cycle during 10 minutes. (3) emission data of 42W in burst under 20kHz 50% duty cycle (10000pls/0.5ms OFF) during 3 hours (110Mpls). Also we report construction of Pilot #1 system. Final target is week level operation with 250W EUV power with CE=4%, more than 27kW CO2 laser power by the end of Q2 of 2015.

Quasistationary magnetic field generation with a laser-driven capacitor-coil assembly.

PubMed

Tikhonchuk, V T; Bailly-Grandvaux, M; Santos, J J; Poyé, A

2017-08-01

Recent experiments are showing possibilities to generate strong magnetic fields on the excess of 500 T with high-energy nanosecond laser pulses in a compact setup of a capacitor connected to a single turn coil. Hot electrons ejected from the capacitor plate (cathode) are collected at the other plate (anode), thus providing the source of a current in the coil. However, the physical processes leading to generation of currents exceeding hundreds of kiloamperes in such a laser-driven diode are not sufficiently understood. Here we present a critical analysis of previous results and propose a self-consistent model for the high current generation in a laser-driven capacitor-coil assembly. It accounts for three major effects controlling the diode current: the space charge neutralization, the plasma magnetization between the capacitor plates, and the Ohmic heating of the external circuit-the coil-shaped connecting wire. The model provides the conditions necessary for transporting strongly super-Alfvenic currents through the diode on the time scale of a few nanoseconds. The model validity is confirmed by a comparison with the available experimental data.

Whole-field digital vibrometer system for buried landmine detection

NASA Astrophysics Data System (ADS)

Lal, Amit; Hess, Cecil; Scott, Eddie; Dang, Michael; Nichols, Robert

2005-06-01

Previous results have shown the potential of acoustic-to-seismic coupling with Laser Doppler Vibrometry for the detection of buried landmines. An important objective of the present technology is to improve the spatial resolution and the speed of the measurement. In this paper, MetroLaser reports on a whole-field digital vibrometer (WDV) that measures an entire one meter area with sub-centimeter spatial resolution in just a few seconds. The WDV is based on a dual-pulsed laser such that each pulse illuminates a one meter area on the ground, and the temporal separation between the two laser pulses can be adjusted to match the ground excitation frequency. By sweeping this excitation frequency, a displacement map of the ground at each frequency can be quickly generated. In addition, an innovative speckle repositioning strategy allows for movement of the measurement platform at reasonable speeds while still obtaining measurements with interferometric precision. This paper describes the WDV instrument and presents preliminary experimental results obtained with this system. This research is being supported by the U.S. Army RDECOM CERDEC NVESD under Contract W909MY04-C-0004.

Analgesic effect of simultaneous exposure to infrared laser radiation and μT magnetic field in rats

NASA Astrophysics Data System (ADS)

Cieslar, Grzegorz; Mrowiec, Janina; Kasperczyk, Slawomir; Sieron-Stoltny, Karolina; Sieron, Aleksander

2008-03-01

The aim of the experiment was to estimate the effect of repeated simultaneous exposures to infrared laser radiation and μT variable magnetic field used in magnetostimulation on pain perception in rats, as well as the involvement of endogenous opioid system in the mechanism of this effect. In experimental group clean-shaven scull of male Wistar rats placed individually in a specially designed plastic chamber were simultaneously exposed to infrared laser radiation (wavelength - 855 nm, mean power - 4,1 mW, energy density - 30 J/cm2) and variable magnetic field of saw-like shape of impulse, at a frequency of basic impulse 180-195 Hz and mean induction value of 120 μT generated by magneto-laser applicator of device for magnetostimulation Viofor JPS (Med & Life, Poland) 12 minutes daily for 2 periods of 5 consecutive days, with 2 days-lasting break between them, while control animals were sham-exposed. The pain perception was determined by means of "hot plate" test on the basis of calculated analgesic index. As a result of repeated exposures a significant increase in analgesic index persisting also till 14 th day after the end of a cycle of exposures was observed. This analgesic effect was inhibited by prior i.p. injection of opioid antagonist - Naloxone.

Study of large Forbush decreases in cosmic-ray intensity observed during solar cycle 23 and 24

NASA Astrophysics Data System (ADS)

Kumar, Anand; Badruddin, B.

2016-07-01

Neutron monitors at different geomagnetic latitude and longitude of Earth measure the cosmic-ray intensity with high precision. Sudden decreases in cosmic-ray intensity within few hours and slow recovery to pre-decrease level within a few days (Forbush decreases) are observed in neutron monitor data. We identify large-amplitude Forbush decreases (FDs), using high counting rate neutron monitor data, that occurred during previous solar cycle 23 (1995-2009) and current solar cycle 24 (2010-2015). We then search for the solar sources and the interplanetary structures responsible for these decreases. We attempt to find the relative importance of various interplanetary plasma and field parameters and the physical mechanism(s) responsible for FDs of varying amplitudes. We analyze a number of interplanetary plasma and field parameters, during both the phases (main and recovery) of FDs. The interplanetary plasma and field data analyzed in this study are the solar-wind velocity, the interplanetary magnetic field, its fluctuations, interplanetary electric field and the time variation of interplanetary electric potential. For monitoring the changes in interplanetary plasma/field conditions during the development of FDs, we also utilize plasma density, temperature and plasma beta, dynamic pressure and Mach number during the passage of interplanetary structures responsible for FDs. In addition to their amplitude, we study the recovery of FDs in detail after determining the time constant during their recovery by exponential fit to the data. As the solar magnetic polarity reversed during the maximum phase of solar cycle 23 (in the year 2000), we study the differences in amplitude, time constant of recovery and plasma/field condition to search for the polarity dependent effects, if any, on the amplitude and recovery of FDs due to implication for the models suggested to explain the Forbush decrease phenomena. The implications of these results are discussed.

Consolidated fuel reprocessing program

NASA Astrophysics Data System (ADS)

1985-04-01

A survey of electrochemical methods applications in fuel reprocessing was completed. A dummy fuel assembly shroud was cut using the remotely operated laser disassembly equipment. Operations and engineering efforts have continued to correct equipment operating, software, and procedural problems experienced during the previous uranium compaigns. Fuel cycle options were examined for the liquid metal reactor fuel cycle. In high temperature gas cooled reactor spent fuel studies, preconceptual designs were completed for the concrete storage cask and open field drywell storage concept. These and other tasks operating under the consolidated fuel reprocessing program are examined.

Closed-cycle gas dynamic laser design investigation

NASA Technical Reports Server (NTRS)

Ketch, G. W.; Young, W. E.

1977-01-01

A conceptual design study was made of a closed cycle gas-dynamic laser to provide definition of the major components in the laser loop. The system potential application is for long range power transmission by way of high power laser beams to provide satellite propulsion energy for orbit changing or station keeping. A parametric cycle optimization was conducted to establish the thermodynamic requirements for the system components. A conceptual design was conducted of the closed cycle system and the individual components to define physical characteristics and establish the system size and weight. Technology confirmation experimental demonstration programs were outlined to develop, evaluate, and demonstrate the technology base needed for this closed cycle GDL system.

Estimating Canopy Structure in an Amazon Forest from Laser Range Finder and IKONOS Satellite Observations

Treesearch

Gregory P. Asner; Michael Palace; Michael Keller; Rodrigo Pereira Jr.; Jose N. M. Silva; Johan C. Zweede

2002-01-01

Canopy structural data can be used for biomass estimation and studies of carbon cycling, disturbance, energy balance, and hydrological processes in tropical forest ecosystems. Scarce information on canopy dimensions reflects the difficulties associated with measuring crown height, width, depth, and area in tall, humid tropical forests. New field and spaceborne...

Reduction of short wavelength reflectance of multi-wall carbon nanotubes through ultraviolet laser irradiation

NASA Astrophysics Data System (ADS)

Stephens, Michelle S.; Simonds, Brian J.; Yung, Christopher S.; Conklin, Davis; Livigni, David J.; Oliva, Alberto Remesal; Lehman, John H.

2018-05-01

Multi-wall carbon nanotube coatings are used as broadband, low-reflectance absorbers for bolometric applications and for stray light control. They are also used as high emittance blackbody radiators. Irradiation of single wall carbon nanotubes with ultraviolet (UV) laser light has been shown to remove amorphous carbon debris, but there have been few investigations of the interaction of UV light with the more complex physics of multi-wall carbon nanotubes. We present measurements of reflectance and surface morphology before and after exposure of multi-wall carbon nanotube coatings to 248 nm UV laser light. We show that UV exposure reduces the reflectivity at wavelengths below 600 nm and present modeling of the thermal cycling the UV exposure causes at the surface of the carbon nanotubes. This effect can be used to flatten the spectral shape of the reflectivity curve of carbon nanotube absorber coatings used for broadband applications. Finally, we find that the effect of UV exposure depends on the nanotube growth process.

Chromatic effect in a novel THz generation scheme

NASA Astrophysics Data System (ADS)

Li, Bin; Zhang, Wenyan; Liu, Xiaoqing; Deng, Haixiao; Lan, Taihe; Liu, Bo; Liu, Jia; Wang, Xingtao; Zeng, Zhinan; Zhang, Lijian

2017-11-01

Deriving single or few cycle terahertz (THz) pulse by an intense femtosecond laser through cascaded optical rectification is a crucial technique in cutting-edge time-resolved spectroscopy to characterize micro-scale structures and ultrafast dynamics. Due to the broadband nature of the ultrafast driving laser, the chromatic effect limits the THz conversion efficiency in optical rectification crystals, especially for those implementing the pulse-front tilt scheme, e.g. lithium niobate (LN) crystal, has been prevalently used in the past decade. In this research we developed a brand new type of LN crystal utilizing Brewster coupling, and conducted systematically experimental and simulative investigation for the chromatic effect and multi-dimensionally entangled parameters in THz generation, predicting that an extreme conversion efficiency of ˜10% would be potentially achievable at the THz absorption coefficient of ˜0.5 cm-1. Moreover, we first discovered that the chirp of the driving laser plays a decisive role in the pulse-front tilt scheme, and the THz generation efficiency could be enhanced tremendously by applying an appropriate chirp.

Light bullets in transparent dielectrics

NASA Astrophysics Data System (ADS)

Kandidov, Valerii; Chekalin, Sergey; Kompanets, Victor; Dormidonov, Alexander

2017-10-01

The state of research of the light bullets (LB) formation in the process of femtosecond laser pulse filamentation is presented. LB is a near single-cycle wave packet that is formed in the result of the light field self-organization in a nonlinear dispersive medium under matched spatiotemporal radiation self-compression in the regime of anomalous group-velocity dispersion (GVD). The formation of each LB is accompanied by the generation of a discrete portion of supercontinuum (SC) in the anti-Stokes region. LB is a short-lived robust object with parameters determined by fundamental properties of the medium and the laser pulse central wavelength.

High power fiber coupled diode lasers for display and lighting applications

NASA Astrophysics Data System (ADS)

Drovs, Simon; Unger, Andreas; Dürsch, Sascha; Köhler, Bernd; Biesenbach, Jens

2017-02-01

The performance of diode lasers in the visible spectral range has been continuously improved within the last few years, which was mainly driven by the goal to replace arc lamps in cinema or home projectors. In addition, the availability of such high power visible diode lasers also enables new applications in the medical field, but also the usage as pump sources for other solid state lasers. This paper summarizes the latest developments of fiber coupled sources with output power from 1.4 W to 120 W coupled into 100 μm to 400 μm fibers in the spectral range around 405 nm and 640 nm. New developments also include the use of fiber coupled multi single emitter arrays at 450 nm, as well as very compact modules with multi-W output power.

High duty cycle hard soldered kilowatt laser diode arrays

NASA Astrophysics Data System (ADS)

Klumel, Genady; Karni, Yoram; Oppenheim, Jacob; Berk, Yuri; Shamay, Moshe; Tessler, Renana; Cohen, Shalom

2010-02-01

High-brightness laser diode arrays operating at a duty cycle of 10% - 20% are in ever-increasing demand for the optical pumping of solid state lasers and directed energy applications. Under high duty-cycle operation at 10% - 20%, passive (conductive) cooling is of limited use, while micro-coolers using de-ionized cooling water can considerably degrade device reliability. When designing and developing actively-cooled collimated laser diode arrays for high duty cycle operation, three main problems should be carefully addressed: an effective local and total heat removal, a minimization of packaging-induced and operational stresses, and high-precision fast axis collimation. In this paper, we present a novel laser diode array incorporating a built-in tap water cooling system, all-hard-solder bonded assembly, facet-passivated high-power 940 nm laser bars and tight fast axis collimation. By employing an appropriate layout of water cooling channels, careful choice of packaging materials, proper design of critical parts, and active optics alignment, we have demonstrated actively-cooled collimated laser diode arrays with extended lifetime and reliability, without compromising their efficiency, optical power density, brightness or compactness. Among the key performance benchmarks achieved are: 150 W/bar optical peak power at 10% duty cycle, >50% wallplug efficiency and <1° collimated fast axis divergence. A lifetime of >0.5 Ghots with <2% degradation has been experimentally proven. The laser diode arrays have also been successfully tested under harsh environmental conditions, including thermal cycling between -20°C and 40°C and mechanical shocks at 500g acceleration. The results of both performance and reliability testing bear out the effectiveness and robustness of the manufacturing technology for high duty-cycle laser arrays.

High resolution laser micro sintering / melting using q-switched and high brilliant laser radiation

NASA Astrophysics Data System (ADS)

Exner, H.; Streek, A.

2015-03-01

Since the discovery of selective laser sintering/melting, numerous modifications have been made to upgrade or customize this technology for industrial purposes. Laser micro sintering (LMS) is one of those modifications: Powders with particles in the range of a few micrometers are used to obtain products with highly resolved structures. Pulses of a q-switched laser had been considered necessary in order to generate sinter layers from the micrometer scaled metal powders. LMS has been applied with powders from metals as well as from ceramic and cermet feedstock's to generate micro parts. Recent technological progress and the application of high brilliant continuous laser radiation have now allowed an efficient laser sintering/melting of micrometer scaled metal powders. Thereby it is remarkable that thin sinter layers are generated using high continuous laser power. The principles of the process, the state of the art in LMS concerning its advantages and limitations and furthermore the latest results of the recent development of this technology will be presented. Laser Micro Sintering / Laser Micro Melting (LMM) offer a vision for a new dimension of additive fabrication of miniature and precise parts also with application potential in all engineering fields.

Large-area few-layer hexagonal boron nitride prepared by quadrupole field aided exfoliation

NASA Astrophysics Data System (ADS)

Lun Lu, Han; Zhi Rong, Min; Qiu Zhang, Ming

2018-03-01

A quadrupole electric field-mediated exfoliation method is proposed to convert micron-sized hexagonal boron nitride (h-BN) powder into few-layer hexagonal boron nitride nanosheets (h-BNNS). Under optimum conditions (400 Hz, 40 V, 32 μg ml-1, sodium deoxycholate, TAE medium), the h-BN powders (thickness >200 nm, horizontal scale ˜10 μm) are successfully exfoliated into 0.5-4 nm (1-10 layers) thick h-BNNS with the same horizontal scale. Dynamic laser scattering and atomic force microscope data show that the yield is 47.6% (for the portion with the thickness of 0.5-6 nm), and all of the vertical sizes are reduced to smaller than 18 nm (45 layers).

Innovative single-shot diagnostics for electrons from laser wakefield acceleration at FLAME

NASA Astrophysics Data System (ADS)

Bisesto, F. G.; Anania, M. P.; Cianchi, A.; Chiadroni, E.; Curcio, A.; Ferrario, M.; Pompili, R.; Zigler, A.

2017-07-01

Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (> 100 GV/m), enabling acceleration of electrons to GeV energy in few centimeters. Here we present all the plasma related activities currently underway at SPARC_LAB exploiting the high power laser FLAME. In particular, we will give an overview of the single shot diagnostics employed: Electro Optic Sampling (EOS) for temporal measurement and Optical Transition Radiation (OTR) for an innovative one shot emittance measurements. In detail, the EOS technique has been employed to measure for the first time the longitudinal profile of electric field of fast electrons escaping from a solid target, driving the ions and protons acceleration, and to study the impact of using different target shapes. Moreover, a novel scheme for one shot emittance measurements based on OTR, developed and tested at SPARC_LAB LINAC, used in an experiment on electrons from laser wakefield acceleration still undergoing, will be shown.

Signal processing and calibration procedures for in situ diode-laser absorption spectroscopy.

PubMed

Werle, P W; Mazzinghi, P; D'Amato, F; De Rosa, M; Maurer, K; Slemr, F

2004-07-01

Gas analyzers based on tunable diode-laser spectroscopy (TDLS) provide high sensitivity, fast response and highly specific in situ measurements of several atmospheric trace gases simultaneously. Under optimum conditions even a shot noise limited performance can be obtained. For field applications outside the laboratory practical limitations are important. At ambient mixing ratios below a few parts-per-billion spectrometers become more and more sensitive towards noise, interference, drift effects and background changes associated with low level signals. It is the purpose of this review to address some of the problems which are encountered at these low levels and to describe a signal processing strategy for trace gas monitoring and a concept for in situ system calibration applicable for tunable diode-laser spectroscopy. To meet the requirement of quality assurance for field measurements and monitoring applications, procedures to check the linearity according to International Standard Organization regulations are described and some measurements of calibration functions are presented and discussed.

Optical hair removal.

PubMed

Ort, R J; Anderson, R R

1999-06-01

Traditional methods of hair removal have proven unsatisfactory for many individuals with excessive or unwanted hair. In the last few years, several lasers and xenon flashlamps have been developed that promise to fulfill the need for a practical, safe, and long-lasting method of hair removal. Aggressive marketing of these has contributed to their popularity among patients and physicians. However, significant controversy and confusion surrounds this field. This article provides a detailed explanation of the scientific underpinnings for optical hair removal and explores the advantages and disadvantages of the various devices currently available (Nd:YAG, ruby, alexandrite, diode lasers, and xenon flashlamp). Treatment and safety guidelines are provided to assist the practitioner in the use of these devices. Although the field of optical hair removal is still in its infancy, initial reports of long-term efficacy are encouraging.

Stationary Light Pulses in Cold Atomic Media and without Bragg Gratings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Y.-W.; Liao, W.-T.; Peters, Thorsten

We study the creation of stationary light pulses (SLPs), i.e., light pulses without motion, based on the effect of electromagnetically induced transparency with two counterpropagating coupling fields in cold atoms. We show that the Raman excitations created by counterpropagating probe and coupling fields prohibit the formation of SLPs in media of cold and stationary atoms such as laser-cooled atom clouds, Bose condensates or color-center crystals. A method is experimentally demonstrated to suppress these Raman excitations and SLPs are realized in laser-cooled atoms. Furthermore, we report the first experimental observation of a bichromatic SLP at wavelengths for which no Bragg gratingmore » can be established. Our work advances the understanding of SLPs and opens a new avenue to SLP studies for few-photon nonlinear interactions.« less

Tunable triple-wavelength mode-locked fiber laser with topological insulator Bi2Se3 solution

NASA Astrophysics Data System (ADS)

Guo, Bo; Yao, Yong

2016-08-01

We experimentally demonstrated a tunable triple-wavelength mode-locked erbium-doped fiber laser with few-layer topological insulator: Bi2Se3/polyvinyl alcohol solution. By properly adjusting the pump power and the polarization state, the single-, dual-, and triple-wavelength mode-locking operation could be stably initiated with a wavelength-tunable range (˜1 nm) and a variable wavelength spacing (1.7 or 2 nm). Meanwhile, it exhibits the maximum output power of 10 mW and pulse energy of 1.12 nJ at the pump power of 175 mW. The simple, low-cost triple-wavelength mode-locked fiber laser might be applied in various potential fields, such as optical communication, biomedical research, and sensing system.

Education and training for technicians in photonics-enabled technologies

NASA Astrophysics Data System (ADS)

Hull, Daniel M.; Hull, Darrell M.

2005-10-01

Within a few years after lasers were first made operational in 1960, it became apparent that rapid growth in the applications of this new technology in industry, health care, and other fields would require a new generation of technicians in laser/optics engineering. Technicians are the men and women who work alongside scientists and engineers in bringing their ideas, designs, and processes to fruition. In America, most highly qualified technicians are graduates of associate of applied science (AAS) programs in community and technical colleges (two-year postsecondary institutions). Curricula and educational programs designed to prepare technicians in laser/electro-optics technology (LEOT) emerged in the 1970s; today there are over 15 LEOT programs in the United States producing over 100 LEOT graduates each year.

Photospheric and coronal magnetic fields in six magnetographs. I. Consistent evolution of the bashful ballerina

NASA Astrophysics Data System (ADS)

Virtanen, Ilpo; Mursula, Kalevi

2016-06-01

Aims: We study the long-term evolution of photospheric and coronal magnetic fields and the heliospheric current sheet (HCS), especially its north-south asymmetry. Special attention is paid to the reliability of the six data sets used in this study and to the consistency of the results based on these data sets. Methods: We use synoptic maps constructed from Wilcox Solar Observatory (WSO), Mount Wilson Observatory (MWO), Kitt Peak (KP), SOLIS, SOHO/MDI, and SDO/HMI measurements of the photospheric field and the potential field source surface (PFSS) model. Results: The six data sets depict a fairly similar long-term evolution of magnetic fields and the heliospheric current sheet, including polarity reversals and hemispheric asymmetry. However, there are time intervals of several years long, when first KP measurements in the 1970s and 1980s, and later WSO measurements in the 1990s and early 2000s, significantly deviate from the other simultaneous data sets, reflecting likely errors at these times. All of the six magnetographs agree on the southward shift of the heliospheric current sheet (the so-called bashful ballerina phenomenon) in the declining to minimum phase of the solar cycle during a few years of the five included cycles. We show that during solar cycles 20-22, the southward shift of the HCS is mainly due to the axial quadrupole term, reflecting the stronger magnetic field intensity at the southern pole during these times. During cycle 23 the asymmetry is less persistent and mainly due to higher harmonics than the quadrupole term. Currently, in the early declining phase of cycle 24, the HCS is also shifted southward and is mainly due to the axial quadrupole as for most earlier cycles. This further emphasizes the special character of the global solar field during cycle 23.

Attosecond physics at the nanoscale

NASA Astrophysics Data System (ADS)

Ciappina, M. F.; Pérez-Hernández, J. A.; Landsman, A. S.; Okell, W. A.; Zherebtsov, S.; Förg, B.; Schötz, J.; Seiffert, L.; Fennel, T.; Shaaran, T.; Zimmermann, T.; Chacón, A.; Guichard, R.; Zaïr, A.; Tisch, J. W. G.; Marangos, J. P.; Witting, T.; Braun, A.; Maier, S. A.; Roso, L.; Krüger, M.; Hommelhoff, P.; Kling, M. F.; Krausz, F.; Lewenstein, M.

2017-05-01

Recently two emerging areas of research, attosecond and nanoscale physics, have started to come together. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femto- and sub-femtosecond time scales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds (1 attosecond  =  1 as  =  10-18 s), which is comparable with the optical field. For comparison, the revolution of an electron on a 1s orbital of a hydrogen atom is  ˜152 as. On the other hand, the second branch involves the manipulation and engineering of mesoscopic systems, such as solids, metals and dielectrics, with nanometric precision. Although nano-engineering is a vast and well-established research field on its own, the merger with intense laser physics is relatively recent. In this report on progress we present a comprehensive experimental and theoretical overview of physics that takes place when short and intense laser pulses interact with nanosystems, such as metallic and dielectric nanostructures. In particular we elucidate how the spatially inhomogeneous laser induced fields at a nanometer scale modify the laser-driven electron dynamics. Consequently, this has important impact on pivotal processes such as above-threshold ionization and high-order harmonic generation. The deep understanding of the coupled dynamics between these spatially inhomogeneous fields and matter configures a promising way to new avenues of research and applications. Thanks to the maturity that attosecond physics has reached, together with the tremendous advance in material engineering and manipulation techniques, the age of atto-nanophysics has begun, but it is in the initial stage. We present thus some of the open questions, challenges and prospects for experimental confirmation of theoretical predictions, as well as experiments aimed at characterizing the induced fields and the unique electron dynamics initiated by them with high temporal and spatial resolution.

Attosecond physics at the nanoscale.

PubMed

Ciappina, M F; Pérez-Hernández, J A; Landsman, A S; Okell, W A; Zherebtsov, S; Förg, B; Schötz, J; Seiffert, L; Fennel, T; Shaaran, T; Zimmermann, T; Chacón, A; Guichard, R; Zaïr, A; Tisch, J W G; Marangos, J P; Witting, T; Braun, A; Maier, S A; Roso, L; Krüger, M; Hommelhoff, P; Kling, M F; Krausz, F; Lewenstein, M

2017-05-01

Recently two emerging areas of research, attosecond and nanoscale physics, have started to come together. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femto- and sub-femtosecond time scales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds (1 attosecond  =  1 as  =  10 -18 s), which is comparable with the optical field. For comparison, the revolution of an electron on a 1s orbital of a hydrogen atom is  ∼152 as. On the other hand, the second branch involves the manipulation and engineering of mesoscopic systems, such as solids, metals and dielectrics, with nanometric precision. Although nano-engineering is a vast and well-established research field on its own, the merger with intense laser physics is relatively recent. In this report on progress we present a comprehensive experimental and theoretical overview of physics that takes place when short and intense laser pulses interact with nanosystems, such as metallic and dielectric nanostructures. In particular we elucidate how the spatially inhomogeneous laser induced fields at a nanometer scale modify the laser-driven electron dynamics. Consequently, this has important impact on pivotal processes such as above-threshold ionization and high-order harmonic generation. The deep understanding of the coupled dynamics between these spatially inhomogeneous fields and matter configures a promising way to new avenues of research and applications. Thanks to the maturity that attosecond physics has reached, together with the tremendous advance in material engineering and manipulation techniques, the age of atto-nanophysics has begun, but it is in the initial stage. We present thus some of the open questions, challenges and prospects for experimental confirmation of theoretical predictions, as well as experiments aimed at characterizing the induced fields and the unique electron dynamics initiated by them with high temporal and spatial resolution.

High-average-power 2 μm few-cycle optical parametric chirped pulse amplifier at 100 kHz repetition rate.

PubMed

Shamir, Yariv; Rothhardt, Jan; Hädrich, Steffen; Demmler, Stefan; Tschernajew, Maxim; Limpert, Jens; Tünnermann, Andreas

2015-12-01

Sources of long wavelengths few-cycle high repetition rate pulses are becoming increasingly important for a plethora of applications, e.g., in high-field physics. Here, we report on the realization of a tunable optical parametric chirped pulse amplifier at 100 kHz repetition rate. At a central wavelength of 2 μm, the system delivered 33 fs pulses and a 6 W average power corresponding to 60 μJ pulse energy with gigawatt-level peak powers. Idler absorption and its crystal heating is experimentally investigated for a BBO. Strategies for further power scaling to several tens of watts of average power are discussed.

Recent advances in ultrafast-laser-based spectroscopy and imaging for reacting plasmas and flames

NASA Astrophysics Data System (ADS)

Patnaik, Anil K.; Adamovich, Igor; Gord, James R.; Roy, Sukesh

2017-10-01

Reacting flows and plasmas are prevalent in a wide array of systems involving defense, commercial, space, energy, medical, and consumer products. Understanding the complex physical and chemical processes involving reacting flows and plasmas requires measurements of key parameters, such as temperature, pressure, electric field, velocity, and number densities of chemical species. Time-resolved measurements of key chemical species and temperature are required to determine kinetics related to the chemical reactions and transient phenomena. Laser-based, noninvasive linear and nonlinear spectroscopic approaches have proved to be very valuable in providing key insights into the physico-chemical processes governing reacting flows and plasmas as well as validating numerical models. The advent of kilohertz rate amplified femtosecond lasers has expanded the multidimensional imaging of key atomic species such as H, O, and N in a significant way, providing unprecedented insight into preferential diffusion and production of these species under chemical reactions or electric-field driven processes. These lasers not only provide 2D imaging of chemical species but have the ability to perform measurements free of various interferences. Moreover, these lasers allow 1D and 2D temperature-field measurements, which were quite unimaginable only a few years ago. The rapid growth of the ultrafast-laser-based spectroscopic measurements has been fueled by the need to achieve the following when measurements are performed in reacting flows and plasmas. They are: (1) interference-free measurements (collision broadening, photolytic dissociation, Stark broadening, etc), (2) time-resolved single-shot measurements at a rate of 1-10 kHz, (3) spatially-resolved measurements, (4) higher dimensionality (line, planar, or volumetric), and (5) simultaneous detection of multiple species. The overarching goal of this article is to review the current state-of-the-art ultrafast-laser-based spectroscopic techniques and their remarkable development in the past two decades in meeting one or all of the above five goals for the spectroscopic measurement of temperature, number density of the atomic and molecular species, and electric field.

Nonlinear Optics and Applications

NASA Technical Reports Server (NTRS)

Abdeldayem, Hossin A. (Editor); Frazier, Donald O. (Editor)

2007-01-01

Nonlinear optics is the result of laser beam interaction with materials and started with the advent of lasers in the early 1960s. The field is growing daily and plays a major role in emerging photonic technology. Nonlinear optics play a major role in many of the optical applications such as optical signal processing, optical computers, ultrafast switches, ultra-short pulsed lasers, sensors, laser amplifiers, and many others. This special review volume on Nonlinear Optics and Applications is intended for those who want to be aware of the most recent technology. This book presents a survey of the recent advances of nonlinear optical applications. Emphasis will be on novel devices and materials, switching technology, optical computing, and important experimental results. Recent developments in topics which are of historical interest to researchers, and in the same time of potential use in the fields of all-optical communication and computing technologies, are also included. Additionally, a few new related topics which might provoke discussion are presented. The book includes chapters on nonlinear optics and applications; the nonlinear Schrodinger and associated equations that model spatio-temporal propagation; the supercontinuum light source; wideband ultrashort pulse fiber laser sources; lattice fabrication as well as their linear and nonlinear light guiding properties; the second-order EO effect (Pockels), the third-order (Kerr) and thermo-optical effects in optical waveguides and their applications in optical communication; and, the effect of magnetic field and its role in nonlinear optics, among other chapters.

'Design of CO-O2 recombination catalysts for closed-cycle CO2 lasers'

NASA Technical Reports Server (NTRS)

Guinn, K.; Goldblum, S.; Noskowski, E.; Herz, R.

1989-01-01

Pulsed CO2 lasers have many applications in aeronautics, space research, weather monitoring and other areas. Full exploitation of the potential of these lasers is hampered by the dissociation of CO2 that occurs during laser operation. The development of closed-cycle CO2 lasers requires active CO-O2 recombination (CO oxidation) catalysts and design methods for implementation of catalysts inside lasers. This paper will discuss the performance criteria and constraints involved in the design of monolith catalyst configurations for use in a closed-cycle laser and will present a design study performed with a computerized design program that had been written. Trade-offs between catalyst activity and dimensions, flow channel dimensions, pressure drop, O2 conversion and other variables will be discussed.

Non-Topographic Space-Based Laser Remote Sensing

NASA Technical Reports Server (NTRS)

Yu, Anthony W.; Abshire, James B.; Riris, Haris; Purucker, Michael; Janches, Diego; Getty, Stephanie; Krainak, Michael A.; Stephen, Mark A.; Chen, Jeffrey R.; Li, Steve X.;

Development and testing of hermetic, laser-ignited pyrotechnic and explosive components

NASA Technical Reports Server (NTRS)

Kramer, Daniel P.; Beckman, Thomas M.; Spangler, Ed M.; Munger, Alan C.; Woods, C. M.

1993-01-01

During the last decade there has been increasing interest in the use of lasers in place of electrical systems to ignite various pyrotechnic and explosive materials. The principal driving force for this work was the requirement for safer energetic components which would be insensitive to electrostatic and electromagnetic radiation. In the last few years this research has accelerated since the basic concepts have proven viable. At the present time it is appropriate to shift the research emphasis in laser initiation from the scientific arena--whether it can be done--to the engineering realm--how it can be put into actual practice in the field. Laser initiation research and development at EG&G Mound was in three principal areas: (1) laser/energetic material interactions; (2) development of novel processing techniques for fabricating hermetic (helium leak rate of less than 1 x 10(exp -8) cu cm/s) laser components; and (3) evaluation and testing of laser-ignited components. Research in these three areas has resulted in the development of high quality, hermetic, laser initiated components. Examples are presented which demonstrate the practicality of fabricating hermetic, laser initiated explosive or pyrotechnic components that can be used in the next generation of ignitors, actuators, and detonators.

Athermal fiber laser for the SWARM absolute scalar magnetometer

NASA Astrophysics Data System (ADS)

Fourcault, W.; Léger, J.-M.; Costes, V.; Fratter, I.; Mondin, L.

2017-11-01

The Absolute Scalar Magnetometer (ASM) developed by CEA-LETI/CNES is an optically pumped 4He magnetic field sensor based on the Zeeman effect and an electronic magnetic resonance whose effects are amplified by a laser pumping process [1-2]. Consequently, the role of the laser is to pump the 4He atoms at the D0 transition as well as to allow the magnetic resonance signal detection. The ASM will be the scalar magnetic reference instrument of the three ESA Swarm satellites to be launched in 2012 in order to carry out the best ever survey of the Earth magnetic field and its temporal evolution. The sensitivity and accuracy of this magnetometer based on 4He optical pumping depend directly on the characteristics of its light source, which is the key sub-system of the sensor. We describe in this paper the selected fiber laser architecture and its wavelength stabilization scheme. Its main performance in terms of spectral emission, optical power at 1083 nm and intensity noise characteristics in the frequency bands used for the operation of the magnetometer, are then presented. Environmental testing results (thermal vacuum cycling, vibrations, shocks and ageing) are also reported at the end of this paper.

Qualification of Laser Diode Arrays for Mercury Laser Altimeter

NASA Technical Reports Server (NTRS)

Stephen, Mark; Vasilyev, Aleksey; Schafer, John; Allan, Graham R.

2004-01-01

NASA's requirements for high reliability, high performance satellite laser instruments have driven the investigation of many critical components; specifically, 808 nm laser diode array (LDA) pump devices. Performance of Quasi-CW, High-power, laser diode arrays under extended use is presented. We report the optical power over several hundred million pulse operation and the effect of power cycling and temperature cycling of the laser diode arrays. Data on the initial characterization of the devices is also presented.

A full time-domain approach to spatio-temporal dynamics of semiconductor lasers. II. Spatio-temporal dynamics

NASA Astrophysics Data System (ADS)

Böhringer, Klaus; Hess, Ortwin

The spatio-temporal dynamics of novel semiconductor lasers is discussed on the basis of a space- and momentum-dependent full time-domain approach. To this means the space-, time-, and momentum-dependent Full-Time Domain Maxwell Semiconductor Bloch equations, derived and discussed in our preceding paper I [K. Böhringer, O. Hess, A full time-domain approach to spatio-temporal dynamics of semiconductor lasers. I. Theoretical formulation], are solved by direct numerical integration. Focussing on the device physics of novel semiconductor lasers that profit, in particular, from recent advances in nanoscience and nanotechnology, we discuss the examples of photonic band edge surface emitting lasers (PBE-SEL) and semiconductor disc lasers (SDLs). It is demonstrated that photonic crystal effects can be obtained for finite crystal structures, and leading to a significant improvement in laser performance such as reduced lasing thresholds. In SDLs, a modern device concept designed to increase the power output of surface-emitters in combination with near-diffraction-limited beam quality, we explore the complex interplay between the intracavity optical fields and the quantum well gain material in SDL structures. Our simulations reveal the dynamical balance between carrier generation due to pumping into high energy states, momentum relaxation of carriers, and stimulated recombination from states near the band edge. Our full time-domain approach is shown to also be an excellent framework for the modelling of the interaction of high-intensity femtosecond and picosecond pulses with semiconductor nanostructures. It is demonstrated that group velocity dispersion, dynamical gain saturation and fast self-phase modulation (SPM) are the main causes for the induced changes and asymmetries in the amplified pulse shape and spectrum of an ultrashort high-intensity pulse. We attest that the time constants of the intraband scattering processes are critical to gain recovery. Moreover, we present new insight into the physics of nonlinear coherent pulse propagation phenomena in active (semiconductor) gain media. Our numerical full time-domain simulations are shown to generally agree well with analytical predictions, while in the case of optical pulses with large pulse areas or few-cycle pulses they reveal the limits of analytic approaches. Finally, it is demonstrated that coherent ultrafast nonlinear propagation effects become less distinctive if we apply a realistic model of the quantum well semiconductor gain material, consider characteristic loss channels and take into account de-phasing processes and homogeneous broadening.

Numerical and Engine Cycle Analyses of a Pulse Laser Ramjet Vehicle

NASA Astrophysics Data System (ADS)

Katsurayama, Hiroshi; Komurasaki, Kimiya; Momozawa, Ai; Arakawa, Yoshihiro

A preliminary feasibility study of a laser ramjet SSTO has been conducted using engine cycle analysis. Although a large amount of laser energy is lost due to chemically frozen flow at high altitudes, the laser ramjet SSTO was found to be feasible with 100 MW laser power for 100 kg vehicle mass and 1 m2 vehicle cross-section area. Obtained momentum coupling coefficient, Cm, was validated by means of CFD. As a result, the engine cycle analysis was under-estimating Cm. This would be because of the strong unsteady energy input in the actual heating process and the spatially localized pressure on the afterbody.

Carrier Envelope Phase Effect of a Long Duration Pulse in the Low Frequency Region

NASA Astrophysics Data System (ADS)

Zhao, Xi; Yang, Yu-Jun; Liu, Xue-Shen; Wang, Bing-Bing

2014-04-01

Using the characteristic of small energy difference between two high Rydberg states, we theoretically investigate the carrier envelope phase (CEP) effect in a bound-bound transition of an atom in a low-frequency long laser pulse with tens of optical cycles. Particularly, we first prepare a Rydberg state of a hydrogen-like atom by a laser field with the resonant frequency between this state and the ground state. Then by using a low-frequency long laser pulse interacting with this Rydberg atom, we calculate the population of another Rydberg state nearby this Rydberg state at the end of the laser pulse and find that the population changes dramatically with the CEP of the low-frequency pulse. This CEP effect is attributed to the interference between the positive-frequency and negative-frequency components in one-photon transition. These results may provide a method to measure the CEP value of a long laser pulse with low frequency.

Dark-field microscopic image stitching method for surface defects evaluation of large fine optics.

PubMed

Liu, Dong; Wang, Shitong; Cao, Pin; Li, Lu; Cheng, Zhongtao; Gao, Xin; Yang, Yongying

2013-03-11

One of the challenges in surface defects evaluation of large fine optics is to detect defects of microns on surfaces of tens or hundreds of millimeters. Sub-aperture scanning and stitching is considered to be a practical and efficient method. But since there are usually few defects on the large aperture fine optics, resulting in no defects or only one run-through line feature in many sub-aperture images, traditional stitching methods encounter with mismatch problem. In this paper, a feature-based multi-cycle image stitching algorithm is proposed to solve the problem. The overlapping areas of sub-apertures are categorized based on the features they contain. Different types of overlapping areas are then stitched in different cycles with different methods. The stitching trace is changed to follow the one that determined by the features. The whole stitching procedure is a region-growing like process. Sub-aperture blocks grow bigger after each cycle and finally the full aperture image is obtained. Comparison experiment shows that the proposed method is very suitable to stitch sub-apertures that very few feature information exists in the overlapping areas and can stitch the dark-field microscopic sub-aperture images very well.

Numerical simulations to model laser-driven coil-capacitor targets for generation of kilo-Tesla magnetic fields

NASA Astrophysics Data System (ADS)

Schillaci, F.; De Marco, M.; Giuffrida, L.; Fujioka, S.; Zhang, Z.; Korn, G.; Margarone, D.

2018-02-01

A coil-capacitor target is modeled using FEM simulations and analytical calculations, which allow to explain the time evolution of such complex target during magnetic field production driven by the flow of an extremely high current generated through the interaction with a high power laser. The numerical model includes a detailed study of the magnetic field produced by the coil-capacitor target, both in the static and transient cases, as well as magnetic force and Joule heating. The model is validated by experimental data reported in literature and can be of interest for several applications. As an example, the combination of two synchronized nanosecond lasers with the purpose of producing a plasma responsible of the proton-boron (p+ + 11B → 8.5 MeV + 3α) fusion reaction, and energizing two multi-turn coils with the main purpose of confining such a plasma could enhance the reaction rate. The preliminary conceptual design of a magnetic mirror configuration to be used for confining protons and boron ions up to a few MeV/u in a region of less than 1 mm2 is briefly reported.

Amplification of anharmonicities in multiphoton vibrational action spectra.

PubMed

Calvo, F; Parneix, P

2012-01-16

The influence of one or several infrared laser pulses on the stability of bare and argon-tagged sodium chloride clusters is investigated theoretically by a combination of computational methods involving explicit molecular dynamics and properly calibrated unimolecular rate theories. The fragmentation spectra obtained by varying the laser frequency in the far-IR range is compared to the linear absorption spectrum resulting from the dipole moment autocorrelation function. Under appropriate laser field parameters, the action spectra are found to resemble the absorption spectra quite accurately in terms of positions, line widths, and even relative intensities. However, the action spectra exhibit residual and systematic redshifts of a few percent, which are partly due to the finite spectral bandwidth but are amplified by the progressive heating by the laser. A quantitative analysis suggests that these anharmonicity effects should generally arise upon multiple photon absorption. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fiber laser-microscope system for femtosecond photodisruption of biological samples

PubMed Central

Yavaş, Seydi; Erdogan, Mutlu; Gürel, Kutan; Ilday, F. Ömer; Eldeniz, Y. Burak; Tazebay, Uygar H.

2012-01-01

We report on the development of a ultrafast fiber laser-microscope system for femtosecond photodisruption of biological targets. A mode-locked Yb-fiber laser oscillator generates few-nJ pulses at 32.7 MHz repetition rate, amplified up to ∼125 nJ at 1030 nm. Following dechirping in a grating compressor, ∼240 fs-long pulses are delivered to the sample through a diffraction-limited microscope, which allows real-time imaging and control. The laser can generate arbitrary pulse patterns, formed by two acousto-optic modulators (AOM) controlled by a custom-developed field-programmable gate array (FPGA) controller. This capability opens the route to fine optimization of the ablation processes and management of thermal effects. Sample position, exposure time and imaging are all computerized. The capability of the system to perform femtosecond photodisruption is demonstrated through experiments on tissue and individual cells. PMID:22435105

THz generation by laser coupling to carbon nanotube array

NASA Astrophysics Data System (ADS)

Malik, Rakhee; Uma, R.

2018-01-01

A viable scheme of THz radiation generation by beating of two lasers ( ω1 , k→ 1 ; ω2 , k→ 2 ) in a nanotube array, mounted on a dielectric substrate, is proposed and studied. The free electrons of the nanotubes acquire a large oscillatory velocity and experience a beat frequency ponderomotive force that turns nanotubes into oscillating dipole antennae emitting THz radiation. The THz power peaks in directions where a phase difference between fields due to successive nanotubes is integral multiple of 2 π . The THz power is large when the beat frequency equals ωp/√{2 } (where ωp is the electron plasma frequency) and surface plasmon resonance occurs. For our set of laser and carbon nanotube parameters, the generated THz is about 0.1 kW for CO2 laser power of 10 GW and pulse length of a few picoseconds.

Control of microstructure and mechanical properties of laser solid formed Inconel 718 superalloy by electromagnetic stirring

NASA Astrophysics Data System (ADS)

Liu, Fencheng; Cheng, Hongmao; Yu, Xiaobin; Yang, Guang; Huang, Chunping; Lin, Xin; Chen, Jing

2018-02-01

The coarse columnar grains and special interface in laser solid formed (LSFed) Inconel 718 superalloy workpieces seriously affect their mechanical properties. To improve the microstructure and mechanical properties of LSFed Inconel 718 superalloy, electromagnetic stirring (EMS) was introduced to alter the solidification process of the molten pool during LSF. The results show that EMS could not completely eliminate the epitaxially growing columnar grains, however, the strong convection of liquid metals can effectively influence the solid-liquid interface growing mode. The segregation of alloying elements on the front of solid-liquid interface is inhibited and the degree of constitutional supercooling decreases correspondingly. Comparing the microstructures of samples formed under different process parameters, the size and amount of the γ+Laves eutectic phases formed in interdendritic area decrease along with the increasing magnetic field intensity, resulting in more uniformly distributed alloying elements. The residual stress distribution is proved to be more uniform, which is beneficial to the grain refinement after recrystallilzaiton. Mechanical properties testing results show an improvement of 100 MPa in tensile strength and 22% in elongation was obtained after EMS was used. The high cycle fatigue properties at room temperature was also improved from 4.09 × 104 cycles to 8.21 × 104 cycles for the as-deposited samples, and from 5.45 × 104 cycles to 12.73 × 104 cycles for the heat treated samples respectively.

Multi-gigahertz repetition rate passively modelocked fiber lasers using carbon nanotubes.

PubMed

Martinez, Amos; Yamashita, Shinji

2011-03-28

There is an increasing demand for all-fiber passively mode-locked lasers with pulse repetition rates in the order of gigahertz for their potential applications in fields such as telecommunications and metrology. However, conventional mode-locked fiber lasers typically operate at fundamental repetition rates of only a few megahertz. In this paper, we report all-fiber laser operation with fundamental repetition rates of 4.24 GHz, 9.63 GHz and 19.45 GHz. This is, to date and to the best of our knowledge, the highest fundamental repetition rate reported for an all-fiber laser. The laser operation is based on the passive modelocking of a miniature all-fiber Fabry-Pérot laser (FFPL) by a carbon nanotube (CNT) saturable absorber. The key components for such device are a very high-gain Er:Yb phosphosilicate fiber and a fiber compatible saturable absorber with very small foot print and very low losses. The laser output of the three lasers was close to transform-limited with a pulsewidth of approximately 1 ps and low noise. As a demonstration of potential future applications for this laser, we also demonstrated supercontinuum generation with a longitudinal mode-spacing of 0.08 nm by launching the laser operating at 9.63 GHz into 30 m of a highly nonlinear dispersion shifted fiber.

Solar Cycle Variability and Grand Minima Induced by Joy's Law Scatter

NASA Astrophysics Data System (ADS)

Karak, Bidya Binay; Miesch, Mark S.

2017-08-01

The strength of the solar cycle varies from one cycle to another in an irregular manner and the extreme example of this irregularity is the Maunder minimum when Sun produced only a few spots for several years. We explore the cause of these variabilities using a 3D Babcock--Leighton dynamo. In this model, based on the toroidal flux at the base of the convection zone, bipolar magnetic regions (BMRs) are produced with flux, tilt angle, and time of emergence all obtain from their observed distributions. The dynamo growth is limited by a tilt quenching.The randomnesses in the BMR emergences make the poloidal field unequal and eventually cause an unequal solar cycle. When observed fluctuations of BMR tilts around Joy's law, i.e., a standard deviation of 15 degrees, are considered, our model produces a variation in the solar cycle comparable to the observed solar cycle variability. Tilt scatter also causes occasional Maunder-like grand minima, although the observed scatter does not reproduce correct statistics of grand minima. However, when we double the tilt scatter, we find grand minima consistent with observations. Importantly, our dynamo model can operate even during grand minima with only a few BMRs, without requiring any additional alpha effect.

New laser machining processes for shape memory alloys

NASA Astrophysics Data System (ADS)

Haferkamp, Heinz; Paschko, Stefan; Goede, Martin

2001-04-01

Due to special material properties, shape memory alloys (SMA) are finding increasing attention in micro system technology. However, only a few processes are available for the machining of miniaturized SMA-components. In this connection, laser material processing offers completely new possibilities. This paper describes the actual status of two projects that are being carried out to qualify new methods to machine SMA components by means of laser radiation. Within one project, the laser material ablation process of miniaturized SMA- components using ultra-short laser pulses (pulse duration: approx. 200 fs) in comparison to conventional laser material ablation is being investigated. Especially for SMA micro- sensors and actuators, it is important to minimize the heat affected zone (HAZ) to maintain the special mechanical properties. Light-microscopic investigations of the grain texture of SMA devices processed with ultra-short laser pulses show that the HAZ can be neglected. Presently, the main goal of the project is to qualify this new processing technique for the micro-structuring of complex SMA micro devices with high precision. Within a second project, investigations are being carried out to realize the induction of the two-way memory effect (TWME) into SMA components using laser radiation. By precisely heating SMA components with laser radiation, local tensions remain near the component surface. In connection with the shape memory effect, these tensions can be used to make the components execute complicated movements. Compared to conventional training methods to induce the TWME, this procedure is faster and easier. Furthermore, higher numbers of thermal cycling are expected because of the low dislocation density in the main part of the component.

How do red and infrared low-level lasers affect folliculogenesis cycle in rat's ovary tissue in comparison with clomiphene under in vivo condition.

PubMed

Naseri, Paria; Alihemmati, Alireza; Rasta, Seyed Hossein

2017-12-01

Folliculogenesis is a cycle that produces the majority of oocyte. Any disruption to this cycle leads to ovulation diseases, like polycystic ovarian syndrome (PCOS). Treatments include drugs and surgery; lasers have also been used complementarily. Meanwhile, still there is no definite treatment for PCOS. This study investigated the photo-bio stimulation effect of near-infrared and red low-level laser on producing follicles and compared the result with result of using common drug, clomiphene. Therefore, the aim of this study was to propose the use of lasers autonomously treatment. So, there was one question: how do lasers affect folliculogenesis cycle in rat's ovary tissue? In this study, 28 rats were assigned to four groups as follows: control (CT), clomiphene drug (D), red laser (RL), and near-infrared laser (NIRL). Afterwards, 14 rats of RL and NIRL groups received laser on the first 2 days of estrous cycle, each 6 days, for 48 days. During treatment period, each rat received energy density of 5 J/cm 2 . Seven rats in D group received clomiphene. After the experiment, lasers' effects at two wavelengths of 630 and 810 nm groups have been investigated and compared with clomiphene and CT groups. Producing different follicles to complement folliculogenesis cycle increased in NIRL and RL groups, but this increase was significant only in the NIRL group. This indicates that NIRL increases ovarian activity to produce oocyte that certainly can be used in future studies for finding a cure to ovarian negligence to produce more oocyte and treat diseases caused by it like PCOS.

Coupling of Laser with Plasma Arc to Facilitate Hybrid Welding of Metallic Materials: A Review

NASA Astrophysics Data System (ADS)

Zhiyong, Li; Srivatsan, T. S.; Yan, LI; Wenzhao, Zhang

2013-02-01

Hybrid laser arc welding combines the advantages of laser welding and arc welding. Ever since its origination in the late 1970s, this technique has gained gradual attention and progressive use due to a combination of high welding speed, better formation of weld bead, gap tolerance, and increased penetration coupled with less distortion. In hybrid laser arc welding, one of the reasons for the observed improvement is an interaction or coupling effect between the plasma arc, laser beam, droplet transfer, and the weld pool. Few researchers have made an attempt to study different aspects of the process to facilitate a better understanding. It is difficult to get a thorough understanding of the process if only certain information in a certain field is provided. In this article, an attempt to analyze the coupling effect of the process was carried out based on a careful review of the research work that has been done which provides useful information from a different prospective.

Parametric study of transport beam lines for electron beams accelerated by laser-plasma interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scisciò, M.; Antici, P., E-mail: patrizio.antici@polytechnique.edu; INRS-EMT, Université du Québec, 1650 Lionel Boulet, Varennes, Québec J3X 1S2

2016-03-07

In the last decade, laser-plasma acceleration of high-energy electrons has attracted strong attention in different fields. Electrons with maximum energies in the GeV range can be laser-accelerated within a few cm using multi-hundreds terawatt (TW) lasers, yielding to very high beam currents at the source (electron bunches with up to tens-hundreds of pC in a few fs). While initially the challenge was to increase the maximum achievable electron energy, today strong effort is put in the control and usability of these laser-generated beams that still lack of some features in order to be used for applications where currently conventional, radio-frequencymore » (RF) based, electron beam lines represent the most common and efficient solution. Several improvements have been suggested for this purpose, some of them acting directly on the plasma source, some using beam shaping tools located downstream. Concerning the latter, several studies have suggested the use of conventional accelerator magnetic devices (such as quadrupoles and solenoids) as an easy implementable solution when the laser-plasma accelerated beam requires optimization. In this paper, we report on a parametric study related to the transport of electron beams accelerated by laser-plasma interaction, using conventional accelerator elements and tools. We focus on both, high energy electron beams in the GeV range, as produced on petawatt (PW) class laser systems, and on lower energy electron beams in the hundreds of MeV range, as nowadays routinely obtained on commercially available multi-hundred TW laser systems. For both scenarios, our study allows understanding what are the crucial parameters that enable laser-plasma accelerators to compete with conventional ones and allow for a beam transport. We show that suitable working points require a tradeoff-combination between low beam divergence and narrow energy spread.« less

Controlled Electron Injection into Plasma Accelerators and SpaceCharge Estimates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fubiani, Gwenael G.J.

2005-09-01

Plasma based accelerators are capable of producing electron sources which are ultra-compact (a few microns) and high energies (up to hundreds of MeVs) in much shorter distances than conventional accelerators. This is due to the large longitudinal electric field that can be excited without the limitation of breakdown as in RF structures.The characteristic scale length of the accelerating field is the plasma wavelength and for typical densities ranging from 10 18 - 10 19 cm -3, the accelerating fields and scale length can hence be on the order of 10-100GV/m and 10-40 μm, respectively. The production of quasimonoenergetic beams wasmore » recently obtained in a regime relying on self-trapping of background plasma electrons, using a single laser pulse for wakefield generation. In this dissertation, we study the controlled injection via the beating of two lasers (the pump laser pulse creating the plasma wave and a second beam being propagated in opposite direction) which induce a localized injection of background plasma electrons. The aim of this dissertation is to describe in detail the physics of optical injection using two lasers, the characteristics of the electron beams produced (the micrometer scale plasma wavelength can result in femtosecond and even attosecond bunches) as well as a concise estimate of the effects of space charge on the dynamics of an ultra-dense electron bunch with a large energy spread.« less

Influence of different temperatures on the thermal fatigue behavior and thermal stability of hot-work tool steel processed by a biomimetic couple laser technique

NASA Astrophysics Data System (ADS)

Meng, Chao; Zhou, Hong; Zhou, Ying; Gao, Ming; Tong, Xin; Cong, Dalong; Wang, Chuanwei; Chang, Fang; Ren, Luquan

2014-04-01

Three kinds of biomimetic non-smooth shapes (spot-shape, striation-shape and reticulation-shape) were fabricated on the surface of H13 hot-work tool steel by laser. We investigated the thermal fatigue behavior of biomimetic non-smooth samples with three kinds of shapes at different thermal cycle temperature. Moreover, the evolution of microstructure, as well as the variations of hardness of laser affected area and matrix were studied and compared. The results showed that biomimetic non-smooth samples had better thermal fatigue behavior compared to the untreated samples at different thermal cycle temperatures. For a given maximal temperature, the biomimetic non-smooth sample with reticulation-shape had the optimum thermal fatigue behavior, than with striation-shape which was better than that with the spot-shape. The microstructure observations indicated that at different thermal cycle temperatures the coarsening degrees of microstructures of laser affected area were different and the microstructures of laser affected area were still finer than that of the untreated samples. Although the resistance to thermal cycling softening of laser affected area was lower than that of the untreated sample, laser affected area had higher microhardness than the untreated sample at different thermal cycle temperature.

The Laser-Assisted Field Effect Transistor Gas Sensor Based on Morphological Zinc-Excited Tin-Doped In2O3 Nanowires

NASA Astrophysics Data System (ADS)

Shariati, Mohsen; Khosravinejad, Fariba

The gas nanosensor of indium oxide nanowires in laser assisted approach, doped with tin and zinc for gas sensing and 1D growth purposes respectively, was reported. The nanowires were very sensitive to H2S gas in low concentration of 20ppb gas at room temperature. The fast dynamic intensive and sensitive response to gas was in a few seconds with an on/off sensitivity ratio of around 10. The square cross-section indium oxide nanowires were fabricated through physical vapor deposition (PVD) mechanism and annealing approach. The field emission scanning electron microscopy (FESEM) observations indicated that the annealing temperature was vital in nanostructures’ morphology. The fabricated nanowires for the optimized annealing temperature in applied growth technique were around 60nm in diameter.

Laser vibration sensing at Fraunhofer IOSB: review and applications

NASA Astrophysics Data System (ADS)

Lutzmann, Peter; Göhler, Benjamin; Hill, Chris A.; van Putten, Frank

2017-03-01

Laser vibrometry based on coherent detection allows noncontact measurements of small-amplitude vibration characteristics of objects. This technique, commonly using the Doppler effect, offers high potential for short-range civil applications and for medium- or long-range applications in defense and security. Most commercially available laser Doppler vibrometers are for short ranges (up to a few tens of meters) and use a single beam from a low-power HeNe laser source (λ=633 nm). Medium- or long-range applications need higher laser output power, and thus, appropriate vibrometers typically operate at 1.5, 2, or 10.6 μm to meet the laser safety regulations. Spatially resolved vibrational information can be obtained from an object by using scanning laser vibrometers. To reduce measuring time and to measure transient object movements and vibrational mode structures of objects, several approaches to multibeam laser Doppler vibrometry have been developed, and some of them are already commercially available for short ranges. We focus on applications in the field of defense and security, such as target classification and identification, including camouflaged or partly concealed targets, and the detection of buried land mines. Examples of civil medium-range applications are also given.

Large Area Few Layers Hexagonal Boron Nitride Prepared by Quadrupole Field Aided Exfoliation.

PubMed

Hanlun, Lu; Rong, Min Zhi; Zhang, Ming Qiu

2018-01-16

A quadrupole electric field mediated exfoliation method is proposed to convert micron sized hexagonal boron nitride (hBN) powders into few layers hexagonal boron nitride nano-sheets (h-BNNS). Under the optimum conditions (400 Hz, 40 V, 32μg/mL, sodium deoxycholate, TAE medium), the hBN powders (thickness > 200 nm, horizontal scale ~ 10 μm) are successfully exfoliated into 0.5-4 nm (1-10 layers) thick h-BNNS with the same horizontal scale. Dynamic laser scattering (DLS) and atomic force microscope (AFM) statistics show that the yield is 47.6 % (for the portion with the thickness of 0.5-6 nm), and all of the vertical sizes are reduced to smaller than 18 nm (45 layers). © 2018 IOP Publishing Ltd.

Demonstration of an advanced fibre laser hydrophone array in Gulf St Vincent

NASA Astrophysics Data System (ADS)

Foster, Scott; Tikhomirov, Alexei; Harrison, Joanne; van Velzen, John

2015-09-01

We have developed an 8-element fibre laser seabed array demonstrating state-of-the art performance characteristics for a fibre laser sensing system. The system employs sea-state-zero sensitivity hydrophones with a flat acoustic response over a bandwidth exceeding 5kHz and very low inertial sensitivity. The system contains no outboard electronics and few metal components making it extremely light, compact, and low complexity. The array may be deployed up to 4 km from a land or sea based platform to a depth of up to 80m. Power delivery and telemetry for all 8 sensors is achieved via a single 2mm diameter optical fibre cable weighing less than 5kg per km. We report here results of the first field trials of this system.

A novel laser-based method for controlled crystallization in dental prosthesis materials

NASA Astrophysics Data System (ADS)

Cam, Peter; Neuenschwander, Beat; Schwaller, Patrick; Köhli, Benjamin; Lüscher, Beat; Senn, Florian; Kounga, Alain; Appert, Christoph

2015-02-01

Glass-ceramic materials are increasingly becoming the material of choice in the field of dental prosthetics, as they can feature both high strength and very good aesthetics. It is believed that their color, microstructure and mechanical properties can be tuned such as to achieve an optimal lifelike performance. In order to reach that ultimate perfection a controlled arrangement of amorphous and crystalline phases in the material is required. A phase transformation from amorphous to crystalline is achieved by a heat treatment at defined temperature levels. The traditional approach is to perform the heat treatment in a furnace. This, however, only allows a homogeneous degree of crystallization over the whole volume of the parent glass material. Here a novel approach using a local heat treatment by laser irradiation is presented. To investigate the potential of this approach the crystallization process of SiO2-Li2O-Al2O3-based glass has been studied with laser systems (pulsed and continuous wave) operating at different wavelengths. Our results show the feasibility of gradual and partial crystallization of the base material using continuous laser irradiation. A dental prosthesis machined from an amorphous glassy state can be effectively treated with laser irradiation and crystallized within a confined region of a few millimeters starting from the body surface. Very good aesthetics have been achieved. Preliminary investigation with pulsed nanosecond lasers of a few hundreds nanoseconds pulse width has enabled more refinement of crystallization and possibility to place start of phase change within the material bulk.

Carrier-envelope phase-dependent effect of high-order sideband generation in ultrafast driven optomechanical system.

PubMed

Xiong, Hao; Si, Liu-Gang; Lü, Xin-You; Yang, Xiaoxue; Wu, Ying

2013-02-01

We analyze the features of the output field of a generic optomechanical system that is driven by a control field and a nanosecond driven pulse, and find a robust high-order sideband generation in optomechanical systems. The typical spectral structure, plateau and cutoff, confirms the nonperturbative nature of the effect, which is similar to high-order harmonic generation in atoms or molecules. Based on the phenomenon, we show that the carrier-envelope phase of laser pulses that contain huge numbers of cycles can cause profound effects.

Alignment, orientation, and Coulomb explosion of difluoroiodobenzene studied with the pixel imaging mass spectrometry (PImMS) camera.

PubMed

Amini, Kasra; Boll, Rebecca; Lauer, Alexandra; Burt, Michael; Lee, Jason W L; Christensen, Lauge; Brauβe, Felix; Mullins, Terence; Savelyev, Evgeny; Ablikim, Utuq; Berrah, Nora; Bomme, Cédric; Düsterer, Stefan; Erk, Benjamin; Höppner, Hauke; Johnsson, Per; Kierspel, Thomas; Krecinic, Faruk; Küpper, Jochen; Müller, Maria; Müller, Erland; Redlin, Harald; Rouzée, Arnaud; Schirmel, Nora; Thøgersen, Jan; Techert, Simone; Toleikis, Sven; Treusch, Rolf; Trippel, Sebastian; Ulmer, Anatoli; Wiese, Joss; Vallance, Claire; Rudenko, Artem; Stapelfeldt, Henrik; Brouard, Mark; Rolles, Daniel

2017-07-07

Laser-induced adiabatic alignment and mixed-field orientation of 2,6-difluoroiodobenzene (C 6 H 3 F 2 I) molecules are probed by Coulomb explosion imaging following either near-infrared strong-field ionization or extreme-ultraviolet multi-photon inner-shell ionization using free-electron laser pulses. The resulting photoelectrons and fragment ions are captured by a double-sided velocity map imaging spectrometer and projected onto two position-sensitive detectors. The ion side of the spectrometer is equipped with a pixel imaging mass spectrometry camera, a time-stamping pixelated detector that can record the hit positions and arrival times of up to four ions per pixel per acquisition cycle. Thus, the time-of-flight trace and ion momentum distributions for all fragments can be recorded simultaneously. We show that we can obtain a high degree of one-and three-dimensional alignment and mixed-field orientation and compare the Coulomb explosion process induced at both wavelengths.

LaRC-developed catalysts for CO2 lasers

NASA Technical Reports Server (NTRS)

Upchurch, Billy T.; Kielin, Erik J.; Miller, Irvin M.

1990-01-01

Pulsed CO2 lasers have many remote sensing applications from space, airborne, and ground platforms. The NASA Laser Atmospheric Wind Sounder (LAWS) system will be designed to measure wind velocities from polar earth orbit for a period of up to three years. Accordingly, this and other applications require a closed-cycle pulsed CO2 laser which necessitates the use of an efficient CO-O2 recombination catalyst for these dissociation products which otherwise would degrade the laser operation. The required catalyst must not only operate at low temperatures but also must operate efficiently for long time periods. The research effort at NASA LaRC has centered around development and testing of CO oxidation catalysts for closed-cycle, pulsed, common and rare-isotope CO2 lasers. Researchers examined available commercial catalysts both in a laser and under simulated closed-cycle laser conditions with efforts aimed toward a thorough understanding of the fundamental catalytic reaction. These data were used to design and synthesize new catalyst compositions to better meet the catalyst requirements for closed-cycle pulsed CO2 lasers. Syntheses and test results for catalysts developed at Langley Research Center which have significantly better long-term decay characteristics than previously available catalysts and at the same time operate quite well under lower temperature conditions are discussed.

A Coupled 2 × 2D Babcock-Leighton Solar Dynamo Model. II. Reference Dynamo Solutions

NASA Astrophysics Data System (ADS)

Lemerle, Alexandre; Charbonneau, Paul

2017-01-01

In this paper we complete the presentation of a new hybrid 2 × 2D flux transport dynamo (FTD) model of the solar cycle based on the Babcock-Leighton mechanism of poloidal magnetic field regeneration via the surface decay of bipolar magnetic regions (BMRs). This hybrid model is constructed by allowing the surface flux transport (SFT) simulation described in Lemerle et al. to provide the poloidal source term to an axisymmetric FTD simulation defined in a meridional plane, which in turn generates the BMRs required by the SFT. A key aspect of this coupling is the definition of an emergence function describing the probability of BMR emergence as a function of the spatial distribution of the internal axisymmetric magnetic field. We use a genetic algorithm to calibrate this function, together with other model parameters, against observed cycle 21 emergence data. We present a reference dynamo solution reproducing many solar cycle characteristics, including good hemispheric coupling, phase relationship between the surface dipole and the BMR-generating internal field, and correlation between dipole strength at cycle maximum and peak amplitude of the next cycle. The saturation of the cycle amplitude takes place through the quenching of the BMR tilt as a function of the internal field. The observed statistical scatter about the mean BMR tilt, built into the model, acts as a source of stochasticity which dominates amplitude fluctuations. The model thus can produce Dalton-like epochs of strongly suppressed cycle amplitude lasting a few cycles and can even shut off entirely following an unfavorable sequence of emergence events.

On the fly quantum dynamics of electronic and nuclear wave packets

NASA Astrophysics Data System (ADS)

Komarova, Ksenia G.; Remacle, F.; Levine, R. D.

2018-05-01

Multielectronic states quantum dynamics on a grid is described in a manner motivated by on the fly classical trajectory computations. Non stationary electronic states are prepared by a few cycle laser pulse. The nuclei respond and begin moving. We solve the time dependent Schrödinger equation for the electronic and nuclear dynamics for excitation from the ground electronic state. A satisfactory accuracy is possible using a localized description on a discrete grid. This enables computing on the fly for both the nuclear and electronic dynamics including non-adiabatic couplings. Attosecond dynamics in LiH is used as an example.

Magnus expansion method for two-level atom interacting with few-cycle pulse

NASA Astrophysics Data System (ADS)

Begzjav, T.; Ben-Benjamin, J. S.; Eleuch, H.; Nessler, R.; Rostovtsev, Y.; Shchedrin, G.

2018-06-01

Using the Magnus expansion to the fourth order, we obtain analytic expressions for the atomic state of a two-level system driven by a laser pulse of arbitrary shape with small pulse area. We also determine the limitation of our obtained formulas due to limited range of convergence of the Magnus series. We compare our method to the recently developed method of Rostovtsev et al. (PRA 2009, 79, 063833) for several detunings. Our analysis shows that our technique based on the Magnus expansion can be used as a complementary method to the one in PRA 2009.

Attosecond pulse carrier-envelope phase effects on ionized electron momentum and energy distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, L.-Y.; Starace, Anthony F.

2007-10-15

We analyze carrier-envelope phase (CEP) effects on electron wave-packet momentum and energy spectra produced by one or two few-cycle attosecond xuv pulses. The few-cycle attosecond pulses are assumed to have arbitrary phases. We predict CEP effects on ionized electron wave-packet momentum distributions produced by attosecond pulses having durations comparable to those obtained by Sansone et al. [Science 314, 443 (2006)]. The onset of significant CEP effects is predicted to occur for attosecond pulse field strengths close to those possible with current experimental capabilities. Our results are based on single-active-electron solutions of the three-dimensional, time-dependent Schroedinger equation including atomic potentials appropriatemore » for the H and He atoms.« less

Influence of localized deformation on A-286 austenitic stainless steel stress corrosion cracking in PWR primary water

NASA Astrophysics Data System (ADS)

Fournier, L.; Savoie, M.; Delafosse, D.

2007-06-01

The low cycle fatigue (LCF) behaviour of precipitation-strengthened A-286 austenitic stainless steel was first investigated at room temperature under 0.2% plastic strain control. LCF led to hardening for the first 20 cycles and then to significant softening. LCF-induced dislocation microstructure was characterized using both bright and dark-field imaging techniques in transmission electron microscopy. Cycling softening was correlated with the formation of precipitate-free localized deformation bands. The effect of these precipitate-free localized deformation bands on A-286 stress corrosion cracking (SCC) behaviour in PWR primary water was then examined by means of constant extension rate tensile (CERT) tests at 320 °C and 360 °C. Comparative CERT tests were performed on companion specimens with similar yield stress but pre-fatigued to a few cycles (4-8) or between 125 and 200 cycles. Specimens pre-fatigued to a few cycles with no precipitate-free localized deformation bands exhibited little susceptibility to intergranular SCC (IGSCC). In contrast, the presence of precipitate-free localized deformation bands formed by pre-fatigue to between 125 and 200 cycles strongly promoted IGSCC. The interest of the approach used in this study is to provide insight into the role of localized deformation in irradiation assisted stress corrosion cracking.

Extracting conformational structure information of benzene molecules via laser-induced electron diffraction

DOE PAGES

Ito, Yuta; Wang, Chuncheng; Le, Anh-Thu; ...

2016-05-01

Here, we have measured the angular distributions of high energy photoelectrons of benzene molecules generated by intense infrared femtosecond laser pulses. These electrons arise from the elastic collisions between the benzene ions with the previously tunnel-ionized electrons that have been driven back by the laser field. Theory shows that laser-free elastic differential cross sections (DCSs) can be extracted from these photoelectrons, and the DCS can be used to retrieve the bond lengths of gas-phase molecules similar to the conventional electron diffraction method. From our experimental results, we have obtained the C-C and C-H bond lengths of benzene with a spatialmore » resolution of about 10 pm. Our results demonstrate that laser induced electron diffraction (LIED) experiments can be carried out with the present-day ultrafast intense lasers already. Looking ahead, with aligned or oriented molecules, more complete spatial information of the molecule can be obtained from LIED, and applying LIED to probe photo-excited molecules, a “molecular movie” of the dynamic system may be created with sub-A°ngstrom spatial and few-ten femtosecond temporal resolutions.« less

Laser-based fast-neutron spectroscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Pomerantz, Ishay; Kishon, Itay; Kleinschmidt, Annika; Schanz, Victor A.; Tebartz, Alexandra; Fernández, Juan Carlos; Gautier, Donald C.; Johnson, Randall Philip; Shimada, Tsutomu; Wurden, Glen Anthony; Roth, Markus

2017-05-01

Great progress has been made in recent years in realizing compact, laser-based neutron generators. These devices, however, are inapplicable for conducting energy-resolved fast-neutron radiography because of the electromagnetic noise produced by the interaction of a strong laser field with matter. To overcome this limitation, we developed a novel neutron time-of-flight detector, largely immune to electromagnetic noise. The detector is based on plastic scintillator, only a few mm in size, which is coupled to a silicon photo-multiplier by a long optical fiber. I will present results we obtained at the Trident Laser Facility at Los Alamos National Laboratory during the summer of 2016. Using this detector, we recorded high resolution, low-background fast neutron spectra generated by the interaction of laser accelerated deuterons with Beryllium. The quality of these spectra was sufficient to resolve the unique neutron absorption spectra of different elements and thus it is the first demonstration of laser-based fast neutron spectroscopy. I will discuss how this achievement paves the way to realizing compact neutron radiography systems for research, security, and commercial applications.

Femtosecond laser induced nanostructuring of graphite for the fabrication of quasi-periodic nanogratings and novel carbon nanostructures

NASA Astrophysics Data System (ADS)

Saikiran, V.; Dar, Mudasir H.; Rao, D. Narayana

2018-01-01

Here we have experimentally studied ultrafast femtosecond laser ablation of graphite in air and water environments for the fabrication of promising nanostructures on the graphite surface and also nanographite flakes, graphene quantum dots in water. After the fs laser irradiation in air quasi-periodic nanogratings were found on the graphite surface and when the irradiation is done in water we observed graphene quantum dots (GQDs) and graphitic flakes dispersed in the solution. The sheets consist of few layers of spongy kind of porous graphene, which form an irregular 3D porous structure. The field emission scanning electron microscopy reveals the formation of fluence dependent quasi-periodic deep-subwavelength nanogratings (Ʌ = 130-230 nm) on the surface. Several characterization methods have confirmed the formation of layered graphene and quantum dots. The studies on the solution confirmed the presence of GQDs with dimensions ranging about 2-4 nm. It is found that the formation of subwavelength structures and GQDs depends on the fs-laser energy and vary with different laser parameters such as fluence, energy, laser polarization.

A dark-line two-dimensional magneto-optical trap of 85Rb atoms with high optical depth.

PubMed

Zhang, Shanchao; Chen, J F; Liu, Chang; Zhou, Shuyu; Loy, M M T; Wong, G K L; Du, Shengwang

2012-07-01

We describe the apparatus of a dark-line two-dimensional (2D) magneto-optical trap (MOT) of (85)Rb cold atoms with high optical depth (OD). Different from the conventional configuration, two (of three) pairs of trapping laser beams in our 2D MOT setup do not follow the symmetry axes of the quadrupole magnetic field: they are aligned with 45° angles to the longitudinal axis. Two orthogonal repumping laser beams have a dark-line volume in the longitudinal axis at their cross over. With a total trapping laser power of 40 mW and repumping laser power of 18 mW, we obtain an atomic OD up to 160 in an electromagnetically induced transparency (EIT) scheme, which corresponds to an atomic-density-length product NL = 2.05 × 10(15) m(-2). In a closed two-state system, the OD can become as large as more than 600. Our 2D MOT configuration allows full optical access of the atoms in its longitudinal direction without interfering with the trapping and repumping laser beams spatially. Moreover, the zero magnetic field along the longitudinal axis allows the cold atoms maintain a long ground-state coherence time without switching off the MOT magnetic field, which makes it possible to operate the MOT at a high repetition rate and a high duty cycle. Our 2D MOT is ideal for atomic-ensemble-based quantum optics applications, such as EIT, entangled photon pair generation, optical quantum memory, and quantum information processing.

Frequency divide-and-conquer approach to producing octave-wide frequency combs and few-cycle pulses in the mid-IR

NASA Astrophysics Data System (ADS)

Vodopyanov, Konstantin

2014-05-01

I will present a new technique for extending frequency combs to the highly desirable yet difficult-to-achieve mid-IR spectral range. The technique is based on subharmonic optical parametric oscillation (OPO) that can be considered as a reverse of the second harmonic generation process. The frequency comb of a pump laser is transposed to half of its central frequency and simultaneously spectrally augmented, thanks to an enormous gain bandwidth of the OPO near degeneracy, as well as due to massive cross-coupling between the laser and the OPO frequency comb components. Using ultrafast erbium (1.56 microns) or thulium (2 microns)-based fiber lasers as a pump and using thin, sub-mm-long, quasi phase-matched lithium niobate or gallium arsenide crystals, we produce frequency combs centered correspondingly at 3.1 or 4 micron subharmonic of the pump frequency. With the properly managed OPO cavity group velocity dispersion, octave-wide frequency combs spanning 2.5 - 6 micron range were achieved. Due to the doubly-resonant operation, the threshold of such a system is low (typically 10 mW) and by several experiments including measuring frequency beats between the OPO comb teeth and a narrow-linewidth CW laser and by interfering the outputs of two identical but distinct OPOs pumped by the same laser, we established that the frequency comb from a subharmonic OPO is phase-locked to that of the pump laser. Pulse duration measurements show that for the optimal intracavity dispersion conditions, we generate sub 5-cycle pulses at the subharmonic of the pump. I will also talk about applications of our mid-IR frequency combs to trace gas detection, where part-per-billion sensitivity of molecular detection is achieved as well as about Fourier spectroscopy using a dual-comb system consisting of two phase-locked lasers. I thank NASA, Office of Naval Research, Air Force Office of Scientific Research, Agilent Technologies, Sanofi- Aventis, Stanford University Bio-X, Stanford Medical School, and Stanford Woods Institute for their financial support.

Polarization control of isolated high-harmonic pulses

NASA Astrophysics Data System (ADS)

Huang, Pei-Chi; Hernández-García, Carlos; Huang, Jen-Ting; Huang, Po-Yao; Lu, Chih-Hsuan; Rego, Laura; Hickstein, Daniel D.; Ellis, Jennifer L.; Jaron-Becker, Agnieszka; Becker, Andreas; Yang, Shang-Da; Durfee, Charles G.; Plaja, Luis; Kapteyn, Henry C.; Murnane, Margaret M.; Kung, A. H.; Chen, Ming-Chang

2018-06-01

High-harmonic generation driven by femtosecond lasers makes it possible to capture the fastest dynamics in molecules and materials. However, thus far, the shortest isolated attosecond pulses have only been produced with linear polarization, which limits the range of physics that can be explored. Here, we demonstrate robust polarization control of isolated extreme-ultraviolet pulses by exploiting non-collinear high-harmonic generation driven by two counter-rotating few-cycle laser beams. The circularly polarized supercontinuum is produced at a central photon energy of 33 eV with a transform limit of 190 as and a predicted linear chirp of 330 as. By adjusting the ellipticity of the two counter-rotating driving pulses simultaneously, we control the polarization state of isolated extreme-ultraviolet pulses—from circular through elliptical to linear polarization—without sacrificing conversion efficiency. Access to the purely circularly polarized supercontinuum, combined with full helicity and ellipticity control, paves the way towards attosecond metrology of circular dichroism.

Measurement of ultrashort laser pulses using single-crystal films of 4-aminobenzophenone

NASA Astrophysics Data System (ADS)

Bhowmik, Achintya K.; Tan, Shida; Ahyi, Ayayi C.; Dharmadhikari, J. A.; Dharmadhikari, A. K.; Mathur, D.

2007-12-01

Single-crystal thin-film of an organic second-order nonlinear optical material, 4-aminobenzophenone (ABP), is used to measure the pulsewidth of a Ti-Sapphire laser producing ˜45 fs pulses at 1 kHz repetition rate, by the non-collinear second-harmonic generation (SHG) intensity autocorrelation technique. These films are suitable for measurements over a broad wavelength range, down to 780 nm, due to their wide optical transparency. The single-crystal film with thickness (˜3 μm) less than the coherence length requires no phase-matching for efficient broadband SHG. Pulse walk-off due to group-velocity mismatch (GVM) and temporal broadening of the pulses due to group-velocity dispersion (GVD) are found to be negligible. These effects have been estimated for pulse width down to few-cycle pulses (˜10 fs), and the analyses show that these films can be used to characterize such ultrashort optical pulses.

Gasdynamic lasers and photon machines.

NASA Technical Reports Server (NTRS)

Christiansen, W. H.; Hertzberg, A.

1973-01-01

The basic operational highlights of CO2-N2 gasdynamic lasers (GDL's) are described. Features common to powerful gas lasers are indicated. A simplified model of the vibrational kinetics of the system is presented, and the importance of rapid expansion nozzles is shown from analytic solutions of the equations. A high-power pulsed GDL is described, along with estimations of power extraction. A closed-cycle laser is suggested, leading to a description of a photon generator/engine. Thermodynamic analysis of the closed-cycle laser illustrates in principle the possibility of direct conversion of laser energy to work.

Application of a high-repetition-rate laser diagnostic system for single-cycle-resolved imaging in internal combustion engines.

PubMed

Hult, Johan; Richter, Mattias; Nygren, Jenny; Aldén, Marcus; Hultqvist, Anders; Christensen, Magnus; Johansson, Bengt

2002-08-20

High-repetition-rate laser-induced fluorescence measurements of fuel and OH concentrations in internal combustion engines are demonstrated. Series of as many as eight fluorescence images, with a temporal resolution ranging from 10 micros to 1 ms, are acquired within one engine cycle. A multiple-laser system in combination with a multiple-CCD camera is used for cycle-resolved imaging in spark-ignition, direct-injection stratified-charge, and homogeneous-charge compression-ignition engines. The recorded data reveal unique information on cycle-to-cycle variations in fuel transport and combustion. Moreover, the imaging system in combination with a scanning mirror is used to perform instantaneous three-dimensional fuel-concentration measurements.

Shock isolator for diode laser operation on a closed-cycle refrigerator

NASA Technical Reports Server (NTRS)

Jennings, D. E.; Hillman, J. J.

1977-01-01

Closed-cycle helium refrigerators are widely used as coolers for semiconductor diode lasers. These refrigerators pose several difficulties including temperature oscillations due to varying refrigerator capacity during the Solvay cycle, and impact shocks delivered to the diode in the cycle's expansion phase. A shock isolator has been designed to isolate diode lasers from such impact shocks. Slow diode current scans have been made before installation of the shock isolator, with the isolator but no thermal damper, and with both devices. With the isolator and no damper, the diode output frequency oscillated at the refrigerator cycle rate, deviating by plus or minus 40 MHz. Using the isolator and the damper no frequency fluctuation was detected.

Subcycle dynamics of high-order-harmonic generation of He atoms excited by attosecond pulses and driven by near-infrared laser fields: A self-interaction-free time-dependent density-functional-theory approach

NASA Astrophysics Data System (ADS)

Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

2014-05-01

In the framework of the self-interaction-free time-dependent density-functional theory, we have performed three-dimensional (3D) ab initio calculations of He atoms in near-infrared (NIR) laser fields subject to excitation by a single extreme ultraviolet (XUV) attosecond pulse (SAP). We have explored the dynamical behavior of the subcycle high harmonic generation (HHG) for transitions from the excited states to the ground state and found oscillation structures with respect to the time delay between the SAP and NIR fields. The oscillatory pattern in the photon emission spectra has a period of ˜1.3 fs which is half of the NIR laser optical cycle, similar to that recently measured in the experiments on transient absorption of He [M. Chini et al., Sci. Rep. 3, 1105 (2013), 10.1038/srep01105]. We present the photon emission spectra from 1s2p, 1s3p, 1s4p, 1s5p, and 1s6p excited states as functions of the time delay. We explore the subcycle Stark shift phenomenon in NIR fields and its influence on the photon emission process. Our analysis reveals several interesting features of the subcycle HHG dynamics and we identify the mechanisms responsible for the observed peak splitting in the photon emission spectra.

Aerodynamic/acoustic performance of YJ101/double bypass VCE with coannular plug nozzle

NASA Technical Reports Server (NTRS)

Vdoviak, J. W.; Knott, P. R.; Ebacker, J. J.

1981-01-01

Results of a forward Variable Area Bypass Injector test and a Coannular Nozzle test performed on a YJ101 Double Bypass Variable Cycle Engine are reported. These components are intended for use on a Variable Cycle Engine. The forward Variable Area Bypass Injector test demonstrated the mode shifting capability between single and double bypass operation with less than predicted aerodynamic losses in the bypass duct. The acoustic nozzle test demonstrated that coannular noise suppression was between 4 and 6 PNdB in the aft quadrant. The YJ101 VCE equipped with the forward VABI and the coannular exhaust nozzle performed as predicted with exhaust system aerodynamic losses lower than predicted both in single and double bypass modes. Extensive acoustic data were collected including far field, near field, sound separation/ internal probe measurements as Laser Velocimeter traverses.

Comparison of stimulated and spontaneous laser-radar methods for the remote sensing of ocean physical properties

NASA Astrophysics Data System (ADS)

Leonard, Donald A.; Sweeney, Harold E.

1990-09-01

The physical properties of ocean water, in the top few ten meters, are of great interest in the scientific, engineering, and general oceanographic communities. Subsurface profiles of temperature, salinity, and sound speed measured by laser radar in real time on a synoptic basis over a wide area from an airborne platform would provide valuable information complementary to the data that is now readily available. The laser-radar technique specifically applicable to ocean sensing uses spectroscopic analysis of the inelastic backscattered optical signal. Two methods have received considerable attention for remote sensing and both have been demonstrated in field experiments. These are spontaneous Raman1 and spontaneous Brillouin2 scattering. A discussion of these two processes and a comparison of their properties that are useful for remote sensing was presented3 at SPIE Ocean Optics IX. This paper compares ocean remote sensing using stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) processes with better known spontaneous methods. The results of laboratory measurements of temperature using SBS and some preliminary results of SRS are presented with extensions to performance estimates of potential field systems.

Performance of a three-dimensional-printed microscanner in a laser scanning microscopy application

NASA Astrophysics Data System (ADS)

Oyman, Hilmi Artun; Gokdel, Yigit Daghan; Ferhanoglu, Onur; Yalcinkaya, Arda Deniz

2018-04-01

A magnetically actuated microscanner is used in a laser scanning microscopy application. Stress distribution along the circular-profiled flexure is compared with a rectangular counterpart in finite-element environment. Magnetic actuation mechanism of the scanning unit is explained in detail. Moreover, reliability of the scanner is tested for 3×106 cycle. The scanning device is designed to meet a confocal microscopy application providing 100 μm×100 μm field of view and <3-μm lateral resolution. The resonance frequencies of the device were analytically modeled, where we obtained 130- and 268-Hz resonance values for the out-of-plane and torsion modes, respectively. The scanning device provided an optical scan angle about 2.5 deg for 170-mA drive current, enabling the desired field of view for our custom built confocal microscope setup. Finally, imaging experiments were conducted on a resolution target, showcasing the desired scan area and resolution.

Molecular isomerization induced by ultrashort infrared pulses. I. Few-cycle to sub-one-cycle Gaussian pulses and the role of the carrier-envelope phase.

PubMed

Uiberacker, Christoph; Jakubetz, Werner

2004-06-22

Using 550 previously calculated vibrational energy levels and dipole moments we performed simulations of the HCN-->HNC isomerization dynamics induced by sub-one-cycle and few-cycle IR pulses, which we represent as Gaussian pulses with 0.25-2 optical cycles in the pulse width. Starting from vibrationally pre-excited states, isomerization probabilities of up to 50% are obtained for optimized pulses. With decreasing number of optical cycles a strong dependence on the carrier-envelope phase (CEP) emerges. Although the optimized pulse parameters change significantly with the number of optical cycles, the distortion by the Gaussian envelope produces nearly equal fields, with a positive lobe followed by a negative one. The positions and areas of the lobes are also almost unchanged, irrespective of the number of cycles in the half-width. Isomerization proceeds via a pump-dumplike mechanism induced by the sequential lobes. The first lobe prepares a wave packet incorporating many delocalized states above the barrier. It is the motion of this wave packet across the barrier, which determines the timing of the pump and dump lobes. The role of the pulse parameters, and in particular of the CEP, is to produce the correct lobe sequence, size and timing within a continuous pulse. (c) 2004 American Institute of Physics.

Intense ionizing radiation from laser-induced processes in ultra-dense deuterium D(-1)

NASA Astrophysics Data System (ADS)

Olofson, Frans; Holmlid, Leif

2014-09-01

Nuclear fusion in ultra-dense deuterium D(-1) has been reported from our laboratory in a few studies using pulsed lasers with energy < 0.2 J. The direct observation of massive particles with energy 1-20 MeV u-1 is conclusive proof for fusion processes, either as a cause or as a result. Continuing the step-wise approach necessary for untangling a complex problem, the high-energy photons from the laser-induced plasma are now studied. The focus is here on the photoelectrons formed. The photons penetrating a copper foil have energy > 80 keV. The total charge created is up to 2 μC or 1 × 1013 photoelectrons per laser shot at 0.13 J pulse energy, assuming isotropic photon emission. The variation of the photoelectron current with laser intensity is faster than linear for some systems, which indicates rapid approach to volume ignition. On a permanent magnet at approximately 1 T, a laser pulse-energy threshold exists for the laser-induced processes probably due to the floating of most clusters of D(-1) in the magnetic field. This Meissner effect was reported previously.

LIDT test coupled with gamma radiation degraded optics

NASA Astrophysics Data System (ADS)

IOAN, M.-R.

2016-06-01

A laser can operate in regular but also in nuclear ionizing radiation environments. This paper presents the results of a real time measuring method used to detect the laser induced damage threshold (LIDT) in the optical surfaces/volumes of TEMPAX borosilicate glasses operating in high gamma rays fields. The laser damage quantification technique is applied by using of an automated station intended to measure the damage threshold of optical components, according to the International Standard ISO 21254. Single and multiple pulses laser damage thresholds were determined. For an optical material, life time when it is subjected to multiple pulses of high power laser radiation can be predicted. A few ns pulses shooting laser, operating in regular conditions, inflects damage to a target by its intense electrical component but also in a lower manner by local absorption of its transported thermal energy. When the beam is passing thru optical glass elements affected by ionizing radiation fields, the thermal component is starting to have a more important role, because of the increased thermal absorption in the material's volume caused by the radiation induced color centers. LIDT results on TEMPAX optical glass windows, with the contribution due to the gamma radiation effects (ionization mainly by Compton effect in this case), are presented. This contribution was highlighted and quantified. Energetic, temporal and spatial beam characterizations (according to ISO 11554 standards) and LIDT tests were performed using a high power Nd: YAG laser (1064 nm), before passing the beam through each irradiated glass sample (0 kGy, 1.3 kGy and 21.2 kGy).

Laser-Induced Damage with Femtosecond Pulses

NASA Astrophysics Data System (ADS)

Kafka, Kyle R. P.

The strong electric fields of focused femtosecond laser pulses lead to non-equilibrium dynamics in materials, which, beyond a threshold intensity, causes laser-induced damage (LID). Such a strongly non-linear and non-perturbative process renders important LID observables like fluence and intensity thresholds and damage morphology (crater) extremely difficult to predict quantitatively. However, femtosecond LID carries a high degree of precision, which has been exploited in various micro/nano-machining and surface engineering applications, such as human eye surgery and super-hydrophobic surfaces. This dissertation presents an array of experimental studies which have measured the damage behavior of various materials under femtosecond irradiation. Precision experiments were performed to produce extreme spatio-temporal confinement of the femtosecond laser-solid damage interaction on monocrystalline Cu, which made possible the first successful direct-benchmarking of LID simulation with realistic damage craters. A technique was developed to produce laser-induced periodic surface structures (LIPSS) in a single pulse (typically a multi-pulse phenomenon), and was used to perform a pump-probe study which revealed asynchronous LIPSS formation on copper. Combined with 1-D calculations, this new experimental result suggests more drastic electron heating than expected. Few-cycle pulses were used to study the LID performance and morphology of commercial ultra-broadband optics, which had not been systematically studied before. With extensive surface analysis, various morphologies were observed, including LIPSS, swelling (blisters), simple craters, and even ring-shaped structures, which varied depending on the coating design, number of pulses, and air/vacuum test environment. Mechanisms leading to these morphologies are discussed, many of which are ultrafast in nature. The applied damage behavior of multi-layer dielectric mirrors was measured and compared between long pulse (150 ps) and femtosecond (33 fs) regimes for a large number of optics contributed by manufacturers globally. The damage performance of the mirrors in the 150 ps tests was shown to be uncorrelated with the 33 fs tests, which implies that the two regimes are guided by different mechanisms. In fact, one of the worst-performing mirrors in the long-pulse regime turned out to be the best-performer in the femtosecond regime. The broad array of experimental results presented here all found that LID in the femtosecond regime is distinctly different from long pulse damage, and paves multiple pathways into developing the next stage of theoretical models and applications of femtosecond laser-induced damage.

Design Investigation of Solar Powered Lasers for Space Applications

DTIC Science & Technology

1979-05-01

Brayton Cycle Power Units 64 3.4 Heat Exchanger 75 3.5 Waste Heat Radiator 79 3.6 Solar Powered Gas Dynamic Laser 82 3.7 Solar Powered Electric... Brayton Cycle Space Power Units 65 10 Supersonic C02 GDL (1 MW) 85 11 Specific Weights for Comparative Evaluation of Solar Lasers 88 12 Subsonic C02...for the Brayton Cycle Power Units 61 21 Solar Radiation Boiler-Receiver Solar Radiation from the Collectors in Focussed (at left) on the

Heat transfer, fluid flow and mass transfer in laser welding of stainless steel with small length scale

NASA Astrophysics Data System (ADS)

He, Xiuli

Nd: YAG Laser welding with hundreds of micrometers in laser beam diameter is widely used for assembly and closure of high reliability electrical and electronic packages for the telecommunications, aerospace and medical industries. However, certain concerns have to be addressed to obtain defect-free and structurally sound welds. During laser welding, Because of the high power density used, the pressures at the weld pool surface can be greater than the ambient pressure. This excess pressure provides a driving force for the vaporization to take place. As a result of vaporization for different elements, the composition in the weld pool may differ from that of base metal, which can result in changes in the microstructure and degradation of mechanical properties of weldments. When the weld pool temperatures are very high, the escaping vapor exerts a large recoil force on the weld pool surface, and as a consequence, tiny liquid metal particles may be expelled from the weld pool. Vaporization of alloying elements and liquid metal expulsion are the two main mechanisms of material loss. Besides, for laser welds with small length scale, heat transfer and fluid flow are different from those for arc welds with much larger length scale. Because of small weld pool size, rapid changes of temperature and very short duration of the laser welding process, physical measurements of important parameters such as temperature and velocity fields, weld thermal cycles, solidification and cooling rates are very difficult. The objective of the research is to quantitatively understand the influences of various factors on the heat transfer, fluid flow, vaporization of alloying elements and liquid metal expulsion in Nd:YAG laser welding with small length scale of 304 stainless steel. In this study, a comprehensive three dimensional heat transfer and fluid flow model based on the mass, momentum and energy conservation equations is relied upon to calculate temperature and velocity fields in the weld pool, weld thermal cycle, weld pool geometry and solidification parameters. Surface tension and buoyancy forces were considered for the calculation of transient weld pool convection. Very fine grids and small time steps were used to achieve accuracy in the calculations. The calculated weld pool dimensions were compared with the corresponding measured values to validate the model. (Abstract shortened by UMI.)

Field Guide: The Culture of the Chinese People’s Liberation Army

DTIC Science & Technology

2009-02-01

technologies , and were knowledgeable on a wide range of subjects 44 Remedy: Add new officer accession paths. The PLA aspires to draw many more officer...needs only a few hundred thousand new conscripts. There are many ways of avoiding conscription; in the end, few people join the military who really...training are carried out as part of an annual cycle: • On November 1, potential conscripts report for screening. • By around February 1, new conscripts

High-intensity laser therapy versus pulsed electromagnetic field in the treatment of primary dysmenorrhea

PubMed Central

Thabet, Ali Abd El-Monsif; Elsodany, Ahmed Mohamed; Battecha, Kadrya H; Alshehri, Mansour Abdullah; Refaat, Bassem

2017-01-01

[Purpose] To determine the efficacy of high intensity laser therapy (HILT) versus pulsed electromagnetic field (PEMF) in the treatment of primary dysmenorrhea. [Subjects and Methods] This was a randomized clinical trial that included 52 girls diagnosed with primary dysmenorrhea and who were assigned randomly into two groups of equal numbers. The treatment was three sessions every cycle for three consecutive cycles where group (A) included those participants treated with HILT 15 min/session and group (B) those who were treated with PEMF 30 min/session. All patients were evaluated before starting the treatment as well as after the end of treatment by present pain intensity scale and the prostaglandin level in blood and pain relief scale at the end of treatment for both groups. [Results] The results showed a significant decrease in the severity of pain, statistically significant decrease in prostaglandin level in blood, and a statistically significant pain alleviation in both groups. With comparison between both groups there was a statistically significant decrease in the severity of pain, significant decrease in the blood levels of PGF2α, in group (A) than group (B). [Conclusion] Both HILT and PEMF are effective in the treatment of primary dysmenorrhea with HILT being superior to PEMF. PMID:29184281

Carrier-envelope phase-stabilized attosecond pulses from asymmetric molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lan Pengfei; Lu Peixiang; Cao Wei

2007-08-15

High-order harmonic generation from asymmetric molecules is investigated, and the concept of phase-stabilized infrared ultrashort laser pulses is extended to the extreme ultraviolet regime. It is shown that the ionization symmetry in consecutive half optical cycles is broken for asymmetric molecules, and both even and odd harmonics with comparable intensity are produced. In the time domain, only one attosecond pulse is generated in each cycle of the driving field, and the carrier-envelope phases of the attosecond pulses are equal. Consequently, a clean attosecond pulse train with the same carrier-envelope phase from pulse to pulse is obtained in the extreme ultravioletmore » regime.« less

Dynamics of photoionization from molecular electronic wavepacket states in intense pulse laser fields: A nonadiabatic electron wavepacket study.

PubMed

Matsuoka, Takahide; Takatsuka, Kazuo

2017-04-07

A theory for dynamics of molecular photoionization from nonadiabatic electron wavepackets driven by intense pulse lasers is proposed. Time evolution of photoelectron distribution is evaluated in terms of out-going electron flux (current of the probability density of electrons) that has kinetic energy high enough to recede from the molecular system. The relevant electron flux is in turn evaluated with the complex-valued electronic wavefunctions that are time evolved in nonadiabatic electron wavepacket dynamics in laser fields. To uniquely rebuild such wavefunctions with its electronic population being lost by ionization, we adopt the complex-valued natural orbitals emerging from the electron density as building blocks of the total wavefunction. The method has been implemented into a quantum chemistry code, which is based on configuration state mixing for polyatomic molecules. Some of the practical aspects needed for its application will be presented. As a first illustrative example, we show the results of hydrogen molecule and its isotope substitutes (HD and DD), which are photoionized by a two-cycle pulse laser. Photon emission spectrum associated with above threshold ionization is also shown. Another example is taken from photoionization dynamics from an excited state of a water molecule. Qualitatively significant effects of nonadiabatic interaction on the photoelectron spectrum are demonstrated.

Innovative single-shot diagnostics for electrons accelerated through laser-plasma interaction at FLAME

NASA Astrophysics Data System (ADS)

Bisesto, F. G.; Anania, M. P.; Chiadroni, E.; Cianchi, A.; Costa, G.; Curcio, A.; Ferrario, M.; Galletti, M.; Pompili, R.; Schleifer, E.; Zigler, A.

2017-05-01

Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (> 100 GV/m), enabling acceleration of electrons to GeV energy in few centimeters. Here we present all the plasma related activities currently underway at SPARC LAB exploiting the high power laser FLAME. In particular, we will give an overview of the single shot diagnostics employed: Electro Optic Sampling (EOS) for temporal measurement and optical transition radiation (OTR) for an innovative one shot emittance measurements. In detail, the EOS technique has been employed to measure for the first time the longitudinal profile of electric field of fast electrons escaping from a solid target, driving the ions and protons acceleration, and to study the impact of using different target shapes. Moreover, a novel scheme for one shot emittance measurements based on OTR, developed and tested at SPARC LAB LINAC, will be shown.

Laser cooling of BaF

NASA Astrophysics Data System (ADS)

Bo, Yan; Bu, Wenhao; Chen, Tao; Lv, Guitao

2017-04-01

In this poster, we report our recently experimental progresses in laser cooling of BaF molecule. Our theoretic calculation shows BaF is a good candidate for laser cooling: quasi-cycling transitions, good wavelengths (around 900nm) for the main transitions. We have built a 4K cryogenic machine, laser ablate the target to make BaF molecules. The precise spectroscopy of BaF is measured and the laser cooling related transitions are identified. The collision between BaF and 4K He is carefully characterized. The quasi-cycling transition is demonstrated. And laser cooling experiment is going on.

Ultra-fast quantum randomness generation by accelerated phase diffusion in a pulsed laser diode.

PubMed

Abellán, C; Amaya, W; Jofre, M; Curty, M; Acín, A; Capmany, J; Pruneri, V; Mitchell, M W

2014-01-27

We demonstrate a high bit-rate quantum random number generator by interferometric detection of phase diffusion in a gain-switched DFB laser diode. Gain switching at few-GHz frequencies produces a train of bright pulses with nearly equal amplitudes and random phases. An unbalanced Mach-Zehnder interferometer is used to interfere subsequent pulses and thereby generate strong random-amplitude pulses, which are detected and digitized to produce a high-rate random bit string. Using established models of semiconductor laser field dynamics, we predict a regime of high visibility interference and nearly complete vacuum-fluctuation-induced phase diffusion between pulses. These are confirmed by measurement of pulse power statistics at the output of the interferometer. Using a 5.825 GHz excitation rate and 14-bit digitization, we observe 43 Gbps quantum randomness generation.

An actively Q-switched fiber laser with cylindrical vector beam generation

NASA Astrophysics Data System (ADS)

Zhang, Jiaojiao; Zhang, Zuxing; Cai, Yu; Wan, Hongdan; Wang, Zhiqiang; Zhang, Lin

2018-03-01

We demonstrate an actively Q-switched fiber laser with cylindrical vector beam (CVB) emission using a few-mode fiber Bragg grating as the mode selection component and an acousto-optic modulator to achieve Q-switching. To the best of our knowledge, this is the first such demonstration. Using a linear cavity configuration, an actively Q-switched CVB with a pulse width of about 64 ns, a pulse energy of 4.25 µJ and a repetition rate of 20 kHz has been obtained. Moreover, by tuning the polarization controllers radially and azimuthally, polarized Q-switched beams can be excited separately with a polarization purity of  >94.5%. This compact Q-switched fiber laser with ns CVB pulse output could find potential applications in the field of material processing, nonlinear optics and so on.

What is the surface temperature of a solid irradiated by a Petawatt laser?

NASA Astrophysics Data System (ADS)

Kemp, A. J.; Divol, L.

2016-09-01

When a solid target is irradiated by a Petawatt laser pulse, its surface is heated to tens of millions of degrees within a few femtoseconds, facilitating a diffusive heat wave and the acceleration of electrons to MeV energies into the target. Using numerically converged collisional particle-in-cell simulations, we observe a competition between two surface heating mechanisms-inverse bremsstrahlung in solid density on the one hand and electron scattering on turbulent electric fields on the other. Collisionless heating effectively dominates above the relativistic intensity threshold. Our numerical results show that a high-contrast 40 fs, f/5 laser pulse with 1 J energy will heat the skin layer to 5 keV, and the inside of the target over several microns deep to bulk temperatures in the range of 10-100 eV at solid density.

GHz laser-free time-resolved transmission electron microscopy: A stroboscopic high-duty-cycle method.

PubMed

Qiu, Jiaqi; Ha, Gwanghui; Jing, Chunguang; Baryshev, Sergey V; Reed, Bryan W; Lau, June W; Zhu, Yimei

2016-02-01

A device and a method for producing ultrashort electron pulses with GHz repetition rates via pulsing an input direct current (dc) electron beam are provided. The device and the method are based on an electromagnetic-mechanical pulser (EMMP) that consists of a series of transverse deflecting cavities and magnetic quadrupoles. The EMMP modulates and chops the incoming dc electron beam and converts it into pico- and sub-pico-second electron pulse sequences (pulse trains) at >1GHz repetition rates, as well as controllably manipulates the resulting pulses. Ultimately, it leads to negligible electron pulse phase-space degradation compared to the incoming dc beam parameters. The temporal pulse length and repetition rate for the EMMP can be continuously tunable over wide ranges. Applying the EMMP to a transmission electron microscope (TEM) with any dc electron source (e.g. thermionic, Schottky, or field-emission source), a GHz stroboscopic high-duty-cycle TEM can be realized. Unlike in many recent developments in time-resolved TEM that rely on a sample pumping laser paired with a laser launching electrons from a photocathode to probe the sample, there is no laser in the presented experimental set-up. This is expected to be a significant relief for electron microscopists who are not familiar with laser systems. The EMMP and the sample are externally driven by a radiofrequency (RF) source synchronized through a delay line. With no laser pumping the sample, the problem of the pump laser induced residual heating/damaging the sample is eliminated. As many RF-driven processes can be cycled indefinitely, sampling rates of 1-50GHz become accessible. Such a GHz stroboscopic TEM would open up a new paradigm for in situ and in operando experiments to study samples externally driven electromagnetically. Complementary to the lower (MHz) repetition rates experiments enabled by laser photocathode TEM, new experiments in the multi-GHz regime will be enabled by the proposed RF design. Because TEM is also a platform for various analytical methods, there are infinite application opportunities in energy and electronics to resolve charge (electronic and ionic) transport, and magnetic, plasmonic and excitonic dynamics in advanced functional materials. In addition, because the beam duty-cycle can be as high as ~10(-1) (or 10%), detection can be accomplished by commercially available detectors. In this article, we report an optimal design of the EMMP. The optimal design was found using an analytical generalized matrix approach in the thin lens approximation along with detailed beam dynamics taking actual realistic dc beam parameters in a TEM operating at 200keV. Copyright © 2015 Elsevier B.V. All rights reserved.

Ultra-narrow band diode lasers with arbitrary pulse shape modulation (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ryasnyanskiy, Aleksandr I.; Smirnov, Vadim; Mokhun, Oleksiy; Glebov, Alexei L.; Glebov, Leon B.

2017-03-01

Wideband emission spectra of laser diode bars (several nanometers) can be largely narrowed by the usage of thick volume Bragg gratings (VBGs) recorded in photo-thermo-refractive glass. Such narrowband systems, with GHz-wide emission spectra, found broad applications for Diode Pumped Alkali vapor Lasers, optically pumped rare gas metastable lasers, Spin Exchange Optical Pumping, atom cooling, etc. Although the majority of current applications of narrow line diode lasers require CW operation, there are a variety of fields where operation in a different pulse mode regime is necessary. Commercial electric pulse generators can provide arbitrary current pulse profiles (sinusoidal, rectangular, triangular and their combinations). The pulse duration and repetition rate however, have an influence on the laser diode temperature, and therefore, the emitting wavelength. Thus, a detailed analysis is needed to understand the correspondence between the optical pulse profiles from a diode laser and the current pulse profiles; how the pulse profile and duty cycle affects the laser performance (e.g. the wavelength stability, signal to noise ratio, power stability etc.). We present the results of detailed studies of the narrowband laser diode performance operating in different temporal regimes with arbitrary pulse profiles. The developed narrowband (16 pm) tunable laser systems at 795 nm are capable of operating in different pulse regimes while keeping the linewidth, wavelength, and signal-to-noise ratio (>20 dB) similar to the corresponding CW modules.

Generation of single-cycle mid-infrared pulses via coherent synthesis.

PubMed

Ma, Fen; Liu, Hongjun; Huang, Nan; Sun, Qibing

2012-12-17

A new approach for the generation of single-cycle mid-infrared pulses without complicated control systems is proposed, which is based on direct coherent synthesis of two idlers generated by difference frequency generation (DFG) processes. It is found that the waveform of synthesized pulses is mainly determined by the spectra superposition, the carrier-envelope phase (CEP) difference, the relative timing and the chirp ratio between the idlers. The influences of these parameters on the synthesized waveform are also numerically calculated and analyzed via second-order autocorrelation, which offers general guidelines for the waveform optimization. The single-cycle synthesized mid-infrared pulses, which are centered at 4233 nm with the spectrum spanning from 3000 nm to 7000 nm, are achieved by carefully optimizing these parameters. The single-cycle mid-infrared laser source presents the possibility of investigating and controlling the strong field light-matter interaction.

Pulsed laser activated cell sorter (PLACS) for high-throughput fluorescent mammalian cell sorting

NASA Astrophysics Data System (ADS)

Chen, Yue; Wu, Ting-Hsiang; Chung, Aram; Kung, Yu-Chung; Teitell, Michael A.; Di Carlo, Dino; Chiou, Pei-Yu

2014-09-01

We present a Pulsed Laser Activated Cell Sorter (PLACS) realized by exciting laser induced cavitation bubbles in a PDMS microfluidic channel to create high speed liquid jets to deflect detected fluorescent samples for high speed sorting. Pulse laser triggered cavitation bubbles can expand in few microseconds and provide a pressure higher than tens of MPa for fluid perturbation near the focused spot. This ultrafast switching mechanism has a complete on-off cycle less than 20 μsec. Two approaches have been utilized to achieve 3D sample focusing in PLACS. One is relying on multilayer PDMS channels to provide 3D hydrodynamic sheath flows. It offers accurate timing control of fast (2 m sec-1) passing particles so that synchronization with laser bubble excitation is possible, an critically important factor for high purity and high throughput sorting. PLACS with 3D hydrodynamic focusing is capable of sorting at 11,000 cells/sec with >95% purity, and 45,000 cells/sec with 45% purity using a single channel in a single step. We have also demonstrated 3D focusing using inertial flows in PLACS. This sheathless focusing approach requires 10 times lower initial cell concentration than that in sheath-based focusing and avoids severe sample dilution from high volume sheath flows. Inertia PLACS is capable of sorting at 10,000 particles sec-1 with >90% sort purity.

Laser engines operating by resonance absorption.

PubMed

Garbuny, M; Pechersky, M J

1976-05-01

The coherence properties and power levels of lasers available at present lend themselves to the remote operation of mechanical engines by resonance absorption in a working gas. Laser radiation is capable of producing extremely high temperatures in a gas. Limits to the achievable temperatures in the working gas of an engine are imposed by the solid walls and by loss of resonance absorption due to thermal saturation, bleaching, and dissociation. However, it is shown that by proper control of the laser beam in space, time, and frequency, as well as by choice of the absorbing gas, these limits are to a great extent removed so that very high temperatures are indeed attainable. The working gas is largely monatomic, preferably helium with the addition of a few volume percent of an absorber. Such a gas mixture, internally heated, permits an optimization of the expansion ratio, with resulting thermal efficiencies and work ratios, not achievable in conventional engines. A relationship between thermal efficiency and work ratio is derived that is quite general for the optimization condition. The performance of laser piston engines, turbines, and the Stirling cycle based on these principles is discussed and compared with conventional engine operation. Finally, a brief discussion is devoted to the possibility and concepts for the direct conversion of selective vibrational or electronic excitation into mechanical work, bypassing the translational degrees of freedom.

Tunable diode-laser heterodyne spectrometer for remote observations near 8 microns

NASA Technical Reports Server (NTRS)

Glenar, D.; Kostiuk, T.; Jennings, D. E.; Buhl, D.; Mumma, M. J.

1982-01-01

A diode-laser-based, ultrahigh resolution IR heterodyne spectrometer for laboratory and field use has been developed for operation between 7.5 and 8.5 microns. The local oscillator is a PbSe tunable diode laser kept continuously at operating temperatures of 12-60 K using a closed-cycle cooler. The laser output frequency is controlled and stabilized using a high-precision diode current supply, constant temperature controller, and a shock isolator mounted between the refrigerator cold tip and the diode mount. The system largely employs reflecting optics to minimize losses from internal reflection and absorption and to eliminate chromatic effects. Spectral analysis of the diode-laser output between 0 and 1 GHz reveals excess noise at many diode current settings, which limits the IR spectral regions over which useful heterodyne operation can be achieved. Observations have been made of atmospheric N2O, O3, and CH4 between 1170 and 1200/cm, using both a single-frequency swept IF channel and a 64-channel RF spectral line receiver with a total IF coverage of 1600 MHz.

Direct-detection Free-space Laser Transceiver Test-bed

NASA Technical Reports Server (NTRS)

Krainak, Michael A.; Chen, Jeffrey R.; Dabney, Philip W.; Ferrara, Jeffrey F.; Fong, Wai H.; Martino, Anthony J.; McGarry Jan. F.; Merkowitz, Stephen M.; Principe, Caleb M.; Sun, Siaoli;

Ultraviolet surprise: Efficient soft x-ray high-harmonic generation in multiply ionized plasmas.

PubMed

Popmintchev, Dimitar; Hernández-García, Carlos; Dollar, Franklin; Mancuso, Christopher; Pérez-Hernández, Jose A; Chen, Ming-Chang; Hankla, Amelia; Gao, Xiaohui; Shim, Bonggu; Gaeta, Alexander L; Tarazkar, Maryam; Romanov, Dmitri A; Levis, Robert J; Gaffney, Jim A; Foord, Mark; Libby, Stephen B; Jaron-Becker, Agnieszka; Becker, Andreas; Plaja, Luis; Murnane, Margaret M; Kapteyn, Henry C; Popmintchev, Tenio

2015-12-04

High-harmonic generation is a universal response of matter to strong femtosecond laser fields, coherently upconverting light to much shorter wavelengths. Optimizing the conversion of laser light into soft x-rays typically demands a trade-off between two competing factors. Because of reduced quantum diffusion of the radiating electron wave function, the emission from each species is highest when a short-wavelength ultraviolet driving laser is used. However, phase matching--the constructive addition of x-ray waves from a large number of atoms--favors longer-wavelength mid-infrared lasers. We identified a regime of high-harmonic generation driven by 40-cycle ultraviolet lasers in waveguides that can generate bright beams in the soft x-ray region of the spectrum, up to photon energies of 280 electron volts. Surprisingly, the high ultraviolet refractive indices of both neutral atoms and ions enabled effective phase matching, even in a multiply ionized plasma. We observed harmonics with very narrow linewidths, while calculations show that the x-rays emerge as nearly time-bandwidth-limited pulse trains of ~100 attoseconds. Copyright © 2015, American Association for the Advancement of Science.

The Ultraviolet Surprise. Efficient Soft X-Ray High Harmonic Generation in Multiply-Ionized Plasmas

DOE PAGES

Popmintchev, Dimitar; Hernandez-Garcia, Carlos; Dollar, Franklin; ...

2015-12-04

High-harmonic generation is a universal response of matter to strong femtosecond laser fields, coherently upconverting light to much shorter wavelengths. Optimizing the conversion of laser light into soft x-rays typically demands a trade-off between two competing factors. Reduced quantum diffusion of the radiating electron wave function results in emission from each species which is highest when a short-wavelength ultraviolet driving laser is used. But, phase matching—the constructive addition of x-ray waves from a large number of atoms—favors longer-wavelength mid-infrared lasers. We identified a regime of high-harmonic generation driven by 40-cycle ultraviolet lasers in waveguides that can generate bright beams inmore » the soft x-ray region of the spectrum, up to photon energies of 280 electron volts. Surprisingly, the high ultraviolet refractive indices of both neutral atoms and ions enabled effective phase matching, even in a multiply ionized plasma. We observed harmonics with very narrow linewidths, while calculations show that the x-rays emerge as nearly time-bandwidth–limited pulse trains of ~100 attoseconds.« less

Switchable Underwater Bubble Wettability on Laser-Induced Titanium Multiscale Micro-/Nanostructures by Vertically Crossed Scanning.

PubMed

Jiao, Yunlong; Li, Chuanzong; Wu, Sizhu; Hu, Yanlei; Li, Jiawen; Yang, Liang; Wu, Dong; Chu, Jiaru

2018-05-16

We present here a kind of novel multiscale TiO 2 square micropillar arrays on titanium sheets through vertically crossed scanning of femtosecond laser. This multiscale micro-/nanostructure is ascribed to the combination of laser ablation/shock compression/debris self-deposition, which shows superaerophobicity in water with a very small sliding angle. The laser-induced sample displays switchable bubble wettability in water via heating in a dark environment and ultraviolet (UV) irradiation in alcohol. After heating in a dark environment (0.5 h), the ablated titanium surface shows superaerophilicity in water with a bubble contact angle (BCA) of ∼4°, which has a great ability of capturing bubbles in water. After UV irradiation in alcohol (1 h), the sample recovered its superaerophobicity in water and the BCA turns into 156°. The mechanism of reversible switching is believed as the chemical conversion between Ti-OH and Ti-O. It is worth noting that our proposed switching strategy is time-saving and the switch wetting cycle costs only 1.5 h. Then we repeat five switching cycles on the reversibility and the method shows excellent reproducibility and stability. Moreover, laser-induced samples with different scanning spacing (50-120 μm) are fabricated and all of them show switchable underwater bubble wettability via the above tunable methods. Finally, we fabricate hybrid-patterned microstructures to show different patterned bubbles in water on the heated samples. We believe the original works will provide some new insights to researchers in bubble manipulation and gas collection fields.

The Si(1-x)Nx Rugate

NASA Astrophysics Data System (ADS)

Bassel, R. H.

1989-08-01

With the advent of lasers, intense sources of monochromatic light are now available. The problem of eye and sensor protection from these devices is now crucial to the field operations of troops and military weapons systems. In other words it is necessary to construct a filter which will reject particular laser lines from impinging upon a material. The results are presented in the infrared and near infrared region of the spectrum. The effectiveness of a Rugate filter constructed of a silicon nitrogen alloy is calculated. Single and double line rugates are discussed. The dependence on the rugate on the various parameters such as the number of cycles, the amplitudes of the sine waves and the phase angle are presented. The effects of absorption, constructional malfunctions, and the angle of incidence of the laser beam are studied. It is found that quite large optical densities can be achieved with rather thin films, thus the silicon nitrogen rugate is a viable candidate for a laser rejection filter.

A COUPLED 2 × 2D BABCOCK–LEIGHTON SOLAR DYNAMO MODEL. II. REFERENCE DYNAMO SOLUTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemerle, Alexandre; Charbonneau, Paul, E-mail: lemerle@astro.umontreal.ca, E-mail: paulchar@astro.umontreal.ca

In this paper we complete the presentation of a new hybrid 2 × 2D flux transport dynamo (FTD) model of the solar cycle based on the Babcock–Leighton mechanism of poloidal magnetic field regeneration via the surface decay of bipolar magnetic regions (BMRs). This hybrid model is constructed by allowing the surface flux transport (SFT) simulation described in Lemerle et al. to provide the poloidal source term to an axisymmetric FTD simulation defined in a meridional plane, which in turn generates the BMRs required by the SFT. A key aspect of this coupling is the definition of an emergence function describing the probabilitymore » of BMR emergence as a function of the spatial distribution of the internal axisymmetric magnetic field. We use a genetic algorithm to calibrate this function, together with other model parameters, against observed cycle 21 emergence data. We present a reference dynamo solution reproducing many solar cycle characteristics, including good hemispheric coupling, phase relationship between the surface dipole and the BMR-generating internal field, and correlation between dipole strength at cycle maximum and peak amplitude of the next cycle. The saturation of the cycle amplitude takes place through the quenching of the BMR tilt as a function of the internal field. The observed statistical scatter about the mean BMR tilt, built into the model, acts as a source of stochasticity which dominates amplitude fluctuations. The model thus can produce Dalton-like epochs of strongly suppressed cycle amplitude lasting a few cycles and can even shut off entirely following an unfavorable sequence of emergence events.« less

Evaluation damage threshold of optical thin-film using an amplified spontaneous emission source

NASA Astrophysics Data System (ADS)

Zhou, Qiong; Sun, Mingying; Zhang, Zhixiang; Yao, Yudong; Peng, Yujie; Liu, Dean; Zhu, Jianqiang

2014-10-01

An accurate evaluation method with an amplified spontaneous emission (ASE) as the irradiation source has been developed for testing thin-film damage threshold. The partial coherence of the ASE source results in a very smooth beam profile in the near-field and a uniform intensity distribution of the focal spot in the far-field. ASE is generated by an Nd: glass rod amplifier in SG-II high power laser facility, with pulse duration of 9 ns and spectral width (FWHM) of 1 nm. The damage threshold of the TiO2 high reflection film is 14.4J/cm2 using ASE as the irradiation source, about twice of 7.4 J/cm2 that tested by a laser source with the same pulse duration and central wavelength. The damage area induced by ASE is small with small-scale desquamation and a few pits, corresponding to the defect distribution of samples. Large area desquamation is observed in the area damaged by laser, as the main reason that the non-uniformity of the laser light. The ASE damage threshold leads to more accurate evaluations of the samples damage probability by reducing the influence of hot spots in the irradiation beam. Furthermore, the ASE source has a great potential in the detection of the defect distribution of the optical elements.

Systems efficiency and specific mass estimates for direct and indirect solar-pumped closed-cycle high-energy lasers in space

NASA Technical Reports Server (NTRS)

Monson, D. J.

1978-01-01

Based on expected advances in technology, the maximum system efficiency and minimum specific mass have been calculated for closed-cycle CO and CO2 electric-discharge lasers (EDL's) and a direct solar-pumped laser in space. The efficiency calculations take into account losses from excitation gas heating, ducting frictional and turning losses, and the compressor efficiency. The mass calculations include the power source, radiator, compressor, fluids, ducting, laser channel, optics, and heat exchanger for all of the systems; and in addition the power conditioner for the EDL's and a focusing mirror for the solar-pumped laser. The results show the major component masses in each system, show which is the lightest system, and provide the necessary criteria for solar-pumped lasers to be lighter than the EDL's. Finally, the masses are compared with results from other studies for a closed-cycle CO2 gasdynamic laser (GDL) and the proposed microwave satellite solar power station (SSPS).

Inducing myoblast re-entry into the cell cycle: a potential mechanism for laser-enhanced skeletal muscle regeneration

NASA Astrophysics Data System (ADS)

Liu, T.; Fang, Y.; Zhang, C. P.; Chen, P.; Wang, C. Z.; Kang, H. X.; Shen, B. J.; Liang, J.; Fu, X. B.

2014-09-01

This study investigated the effect of low-level laser irradiation (LLLI) on the cell cycle and proliferative activity of cultured myoblasts, and sought to elucidate the possible cellular mechanism by which LLLI promotes the regeneration of skeletal muscle in vivo. Primary myoblasts isolated from rat hindlegs were irradiated with helium-neon laser light at different energy densities. Distributions of cell-cycle subpopulations and the expression of cell-cycle regulatory proteins in myoblasts were assessed using flow cytometric analysis and western blot assay. It was found that laser irradiation stimulated cell-cycle entry; induced the expression of cyclin A and cyclin D; and increased cell proliferation index and bromodeoxyuridine incorporation as compared to the unirradiated control cells, indicating LLLI augmented the number of proliferative myoblasts in the S phase and G2/M phase of the cell cycle. These results suggest that LLLI at certain fluxes and wavelengths could activate quiescent myoblasts, leading to cell division and facilitating new myofiber formation. This could contribute to the improvement of skeletal muscle regeneration following trauma and myopathic diseases.

Field propagation-induced directionality of carrier-envelope phase-controlled photoemission from nanospheres

PubMed Central

Süßmann, F.; Seiffert, L.; Zherebtsov, S.; Mondes, V.; Stierle, J.; Arbeiter, M.; Plenge, J.; Rupp, P.; Peltz, C.; Kessel, A.; Trushin, S. A.; Ahn, B.; Kim, D.; Graf, C.; Rühl, E.; Kling, M. F.; Fennel, T.

2015-01-01

Near-fields of non-resonantly laser-excited nanostructures enable strong localization of ultrashort light fields and have opened novel routes to fundamentally modify and control electronic strong-field processes. Harnessing spatiotemporally tunable near-fields for the steering of sub-cycle electron dynamics may enable ultrafast optoelectronic devices and unprecedented control in the generation of attosecond electron and photon pulses. Here we utilize unsupported sub-wavelength dielectric nanospheres to generate near-fields with adjustable structure and study the resulting strong-field dynamics via photoelectron imaging. We demonstrate field propagation-induced tunability of the emission direction of fast recollision electrons up to a regime, where nonlinear charge interaction effects become dominant in the acceleration process. Our analysis supports that the timing of the recollision process remains controllable with attosecond resolution by the carrier-envelope phase, indicating the possibility to expand near-field-mediated control far into the realm of high-field phenomena. PMID:26264422

Field propagation-induced directionality of carrier-envelope phase-controlled photoemission from nanospheres.

PubMed

Süßmann, F; Seiffert, L; Zherebtsov, S; Mondes, V; Stierle, J; Arbeiter, M; Plenge, J; Rupp, P; Peltz, C; Kessel, A; Trushin, S A; Ahn, B; Kim, D; Graf, C; Rühl, E; Kling, M F; Fennel, T

2015-08-12

Near-fields of non-resonantly laser-excited nanostructures enable strong localization of ultrashort light fields and have opened novel routes to fundamentally modify and control electronic strong-field processes. Harnessing spatiotemporally tunable near-fields for the steering of sub-cycle electron dynamics may enable ultrafast optoelectronic devices and unprecedented control in the generation of attosecond electron and photon pulses. Here we utilize unsupported sub-wavelength dielectric nanospheres to generate near-fields with adjustable structure and study the resulting strong-field dynamics via photoelectron imaging. We demonstrate field propagation-induced tunability of the emission direction of fast recollision electrons up to a regime, where nonlinear charge interaction effects become dominant in the acceleration process. Our analysis supports that the timing of the recollision process remains controllable with attosecond resolution by the carrier-envelope phase, indicating the possibility to expand near-field-mediated control far into the realm of high-field phenomena.

The influence of dentin demineralization on morphological features of cavities using Er:YAG laser.

PubMed

Melo, Mary A S; Lima, Juliana P M; Passos, Vanara F; Rodrigues, Lidiany K A

2015-01-01

The purpose of this study was to evaluate the influence of erbium-doped: yttrium-aluminum-garnet (Er:YAG) laser parameters and different degrees of demineralization on morphological features, diameter, and depth of prepared cavities. Minimally invasive dentin caries removal has been recommended. Ablation of deep caries lesions using Er:YAG laser should preserve remaining demineralized dentin; however, the influence of the degree of mineralization of this substrate had not been entirely described. A randomized, factorial design was used to study the effects of two factors. Laser parameter was tested at two levels (250 mJ/4 Hz vs. 200 mJ/2 Hz) and degree of demineralization was tested at four levels (control, two-four-eight cycles). Twelve slabs of human dentin were divided into four groups according to the number of cycles induced by pH-cycling: G1, zero cycles; G2, two cycles, G3, four cycles, and G4, eight cycles. An Er:YAG laser was used at an output energy of 250 mJ/4 Hz and 200 mJ/2 Hz for all groups, for 10 sec at 12 mm distance focus/object. Circumference and depth of the cavities were measured on scanning electron microscopy (SEM) images using image analysis software. The mean values were subjected to two way analysis of variance (ANOVA) and Tukey tests. When using 250 mJ/4 Hz, the mean values of circumferential area increased significantly in relation to control (503.54 μm(2)) with increasing demineralization level (eight cycles) (555.45 μm(2)). Regardless of the demineralization level, there was also significant statistical difference in the studied measurements of the cavities when 250 mJ/4 Hz and 200 mJ/2 Hz were used. SEM also showed that laser cavity preparations left no smear layer, and the dentinal tubules were clear. The circumferential area and depth measurements were affected by laser parameter and demineralization level (eight cycles). Energy level output represents a relevant factor for increased circumferential area and depth measurements. High demineralized artificially caries-affected dentin may also imply higher ablation. Appropriated parameter of laser pulse frequency/power density for demineralized dentin should be used for effective less-invasive caries treatment.

Method for Ground-to-Satellite Laser Calibration System

NASA Technical Reports Server (NTRS)

Lukashin, Constantine (Inventor); Wielicki, Bruce A. (Inventor)

2015-01-01

The present invention comprises an approach for calibrating the sensitivity to polarization, optics degradation, spectral and stray light response functions of instruments on orbit. The concept is based on using an accurate ground-based laser system, Ground-to-Space Laser Calibration (GSLC), transmitting laser light to instrument on orbit during nighttime substantially clear-sky conditions. To minimize atmospheric contribution to the calibration uncertainty the calibration cycles should be performed in short time intervals, and all required measurements are designed to be relative. The calibration cycles involve ground operations with laser beam polarization and wavelength changes.

Method for Ground-to-Space Laser Calibration System

NASA Technical Reports Server (NTRS)

Lukashin, Constantine (Inventor); Wielicki, Bruce A. (Inventor)

2014-01-01

The present invention comprises an approach for calibrating the sensitivity to polarization, optics degradation, spectral and stray light response functions of instruments on orbit. The concept is based on using an accurate ground-based laser system, Ground-to-Space Laser Calibration (GSLC), transmitting laser light to instrument on orbit during nighttime substantially clear-sky conditions. To minimize atmospheric contribution to the calibration uncertainty the calibration cycles should be performed in short time intervals, and all required measurements are designed to be relative. The calibration cycles involve ground operations with laser beam polarization and wavelength changes.

Comparison of the effect of diode laser versus intense pulsed light in axillary hair removal.

PubMed

Ormiga, Patricia; Ishida, Cleide Eiko; Boechat, Alvaro; Ramos-E-Silva, Marcia

2014-10-01

Devices such as diode laser and intense pulsed light (IPL) are in constant development aiming at permanent hair removal, but there are few comparative studies between these technologies. The objective was to comparatively assess axillary hair removal performed by diode laser and IPL and to obtain parameters of referred pain and evolution response for each method. A comparative prospective, double-blind, and randomized study of axillary hair removal performed by the diode laser and IPL was conducted in 21 females. Six sessions were held with application of the diode laser in one axilla and the IPL in the other, with intervals of 30 days and follow-up of 6 months after the last session. Clinical photographs and digital dermoscopy for hair counts in predefined and fixed fields of the treated areas were performed before, 2 weeks after the sixth session, and 6 months after the end of treatment. A questionnaire to assess the pain was applied. The number of hair shafts was significantly reduced with the diode laser and IPL. The diode laser was more effective, although more painful than the IPL. No serious, adverse, or permanent effects were observed with both technologies. Both diode laser and the IPL are effective, safe, and able to produce lasting results in axillary hair removal.

Role of asymmetric meridional circulation in producing north-south asymmetry in a solar cycle dynamo model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belucz, Bernadett; Dikpati, Mausumi

2013-12-10

Solar cycles in the north and south hemispheres differ in cycle length, amplitude, profile, polar fields, and coronal structure. To show what role differences in meridional flow could play in producing these differences, we present the results of three sets of numerical simulations from a flux transport dynamo in which one property of meridional circulation has been changed in the south only. The changes are in amplitude and the presence of a second cell in latitude or in depth. An ascending phase speedup causes weakening of polar and toroidal fields; a speed decrease in a late descending phase does notmore » change amplitudes. A long-duration speed increase leads to lower toroidal field peaks but unchanged polar field peaks. A second high-latitude circulation cell in an ascending phase weakens the next polar and toroidal field peaks, and the ascending phase is lengthened. A second cell in a late descending phase speeds up the cycle. A long-duration second cell leads to a poleward branch of the butterfly diagram and weaker polar fields. A second cell in depth reverses the tilt of the butterfly wing, decreasing polar fields when added during an ascending phase and increasing them during a late descending phase. A long-duration presence of a second cell in radius evolves the butterfly diagram far away from the observed one, with different dynamo periods in low and high latitudes. Thus, a second cell in depth is unlikely to persist more than a few years if the solar dynamo is advection-dominated. Our results show the importance of time variation and north-south asymmetry in meridional circulation in producing differing cycles in the north and south.« less

Return to the red planet

NASA Astrophysics Data System (ADS)

Nichols, Robert G.

1992-10-01

The paper discusses the type of data which will be collected by the NASA's Mars Observer spacecraft when it reaches the planet next year. These will include measurements on the Martian magnetic field, the volcanic activity, the dust storms, seasonal weather cycles, and the planet's atmosphere and gravitational field. The Mars Observer's instruments include a magnetometer, an electron reflectometer, an IR radiometer, a laser altimeter, a thermal-emission spectrometer, a gamma-ray spectrometer, a camera, and a radio system. The program is counting on the vehicle's longevity so that it can participate in a Russian mission due to arrive at Mars in September 1995.

Surface modification of AISI H13 tool steel by laser cladding with NiTi powder

NASA Astrophysics Data System (ADS)

Norhafzan, B.; Aqida, S. N.; Chikarakara, E.; Brabazon, D.

2016-04-01

This paper presents laser cladding of NiTi powder on AISI H13 tool steel surface for surface properties enhancement. The cladding process was conducted using Rofin DC-015 diffusion-cooled CO2 laser system with wavelength of 10.6 µm. NiTi powder was pre-placed on H13 tool steel surface. The laser beam was focused with a spot size of 90 µm on the sample surface. Laser parameters were set to 1515 and 1138 W peak power, 18 and 24 % duty cycle and 2300-3500 Hz laser pulse repetition frequency. Hardness properties of the modified layer were characterized by Wilson Hardness tester. Metallographic study and chemical composition were conducted using field emission scanning electron microscope and energy-dispersive X-ray spectrometer (EDXS) analysis. Results showed that hardness of NiTi clad layer increased three times that of the substrate material. The EDXS analysis detected NiTi phase presence in the modified layer up to 9.8 wt%. The metallographic study shows high metallurgical bonding between substrate and modified layer. These findings are significant to both increased hardness and erosion resistance of high-wear-resistant components and elongating their lifetime.

The lightcraft project

NASA Technical Reports Server (NTRS)

Messitt, Don G.; Myrabo, Leik N.

1991-01-01

Rensselaer Polytechnic Institute has been developing a transatmospheric 'Lightcraft' technology which uses beamed laser energy to propel advanced shuttle craft to orbit. In the past several years, Rensselaer students have analyzed the unique combined-cycle Lightcraft engine, designed a small unmanned Lightcraft Technology Demonstrator, and conceptualized larger manned Lightcraft - to name just a few of the interrelated design projects. The 1990-91 class carried out preliminary and detailed design efforts for a one-person 'Mercury' Lightcraft, using computer-aided design and finite-element structural modeling techniques. In addition, they began construction of a 2.6 m-diameter, full-scale engineering prototype mockup. The mockup will be equipped with three robotic legs that 'kneel' for passenger entry and exit. More importantly, the articulated tripod gear is crucial for accurately pointing at, and tracking the laser relay mirrors, a maneuver that must be performed just prior to liftoff. Also accomplished were further design improvements on a 6-inch-diameter Lightcraft model (for testing in RPI's hypersonic tunnel), and new laser propulsion experiments. The resultant experimental data will be used to calibrate Computational Fluid Dynamic (CFD) codes and analytical laser propulsion models that can simulate vehicle/engine flight conditions along a transatmospheric boost trajectory. These efforts will enable the prediction of distributed aerodynamic and thruster loads over the entire full-scale spacecraft.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ito, Yuta; Wang, Chuncheng; Le, Anh-Thu

Here, we have measured the angular distributions of high energy photoelectrons of benzene molecules generated by intense infrared femtosecond laser pulses. These electrons arise from the elastic collisions between the benzene ions with the previously tunnel-ionized electrons that have been driven back by the laser field. Theory shows that laser-free elastic differential cross sections (DCSs) can be extracted from these photoelectrons, and the DCS can be used to retrieve the bond lengths of gas-phase molecules similar to the conventional electron diffraction method. From our experimental results, we have obtained the C-C and C-H bond lengths of benzene with a spatialmore » resolution of about 10 pm. Our results demonstrate that laser induced electron diffraction (LIED) experiments can be carried out with the present-day ultrafast intense lasers already. Looking ahead, with aligned or oriented molecules, more complete spatial information of the molecule can be obtained from LIED, and applying LIED to probe photo-excited molecules, a “molecular movie” of the dynamic system may be created with sub-A°ngstrom spatial and few-ten femtosecond temporal resolutions.« less

The LILIA (laser induced light ions acceleration) experiment at LNF

NASA Astrophysics Data System (ADS)

Agosteo, S.; Anania, M. P.; Caresana, M.; Cirrone, G. A. P.; De Martinis, C.; Delle Side, D.; Fazzi, A.; Gatti, G.; Giove, D.; Giulietti, D.; Gizzi, L. A.; Labate, L.; Londrillo, P.; Maggiore, M.; Nassisi, V.; Sinigardi, S.; Tramontana, A.; Schillaci, F.; Scuderi, V.; Turchetti, G.; Varoli, V.; Velardi, L.

2014-07-01

Laser-matter interaction at relativistic intensities opens up new research fields in the particle acceleration and related secondary sources, with immediate applications in medical diagnostics, biophysics, material science, inertial confinement fusion, up to laboratory astrophysics. In particular laser-driven ion acceleration is very promising for hadron therapy once the ion energy will attain a few hundred MeV. The limited value of the energy up to now obtained for the accelerated ions is the drawback of such innovative technique to the real applications. LILIA (laser induced light ions acceleration) is an experiment now running at LNF (Frascati) with the goal of producing a real proton beam able to be driven for significant distances (50-75 cm) away from the interaction point and which will act as a source for further accelerating structure. In this paper the description of the experimental setup, the preliminary results of solid target irradiation and start to end simulation for a post-accelerated beam up to 60 MeV are given.

Preliminary Investigations on Therapy Thresholds for Laser Dosimetry, Cryogen Spray Cooling Duration, and Treatment Cycles for Laser Cartilage Reshaping in the New Zealand White Rabbit Auricle

PubMed Central

Chlebicki, Cara A.; Protsenko, Dmitry E.; Wong, Brian J.

2014-01-01

Previous studies have demonstrated the feasibility of laser irradiation (λ=1.45 μm) in tandem with cryogen spray cooling (CSC) to reshape rabbit auricular cartilage using total energy density of 14 J/cm2. The aim of this study was to further explore and identify the dosimetry parameter space for laser output energy, CSC duration, and treatment cycles required to achieve shape change while limiting skin and cartilage injury. Ten New Zealand white rabbits were treated with the 1.45 μm diode laser combined with cryogen spray cooling (Candela Smoothbeam™, Candela Co., Wayland, MA). The ear's central portion was bent around a cylindrical jig and irradiated in consecutive spots of 6 mm diameter (13 J/cm2 or 14 J/cm2 per spot) along 3 rows encompassing the bend. CSC was delivered during irradiation in cycles consisting of 25-35 ms. At thin and thick portions of the ear, 4-7 and 6-10 treatment cycles were delivered, respectively. After surgery, ears were examined and splinted for 6 weeks. Treatment parameters resulting in acceptable (Grades 1 & 2) and unacceptable (Grade 3) skin injuries for thick and thin regions were identified and shape change was observed. Confocal and histological analysis of cartilage tissue revealed several outcomes correlating to laser dosimetry, CSC duration, and treatment cycles. These outcomes included expansion of cartilage layers (thickening), partial cartilage injuries, and full thickness cartilage injuries. We determined therapy thresholds for laser output energy, cryogen spray cooling duration, and treatment cycles in the rabbit auricular model. These parameters are a starting point for future clinical procedures aimed at correcting external ear deformities. PMID:24202858

Preliminary investigations on therapy thresholds for laser dosimetry, cryogen spray cooling duration, and treatment cycles for laser cartilage reshaping in the New Zealand white rabbit auricle.

PubMed

Chlebicki, Cara A; Protsenko, Dmitry E; Wong, Brian J

2014-05-01

Previous studies have demonstrated the feasibility of laser irradiation (λ = 1.45 μm) in tandem with cryogen spray cooling (CSC) to reshape rabbit auricular cartilage using a total energy density of 14 J/cm(2). The aim of this study was to further explore and identify the dosimetry parameter space for laser output energy, CSC duration, and treatment cycles required to achieve shape change while limiting skin and cartilage injury. Ten New Zealand white rabbits were treated with the 1.45 μm diode laser combined with cryogen spray cooling (Candela Smoothbeam™, Candela Co., Wayland, MA, USA). The ear's central portion was bent around a cylindrical jig and irradiated in consecutive spots of 6 mm diameter (13 or 14 J/cm(2) per spot) along three rows encompassing the bend. CSC was delivered during irradiation in cycles consisting of 25-35 ms. At thin and thick portions of the ear, 4-7 and 6-10 treatment cycles were delivered, respectively. After surgery, ears were examined and splinted for 6 weeks. Treatment parameters resulting in acceptable (grades 1 and 2) and unacceptable (grade 3) skin injuries for thick and thin regions were identified, and shape change was observed. Confocal and histological analysis of cartilage tissue revealed several outcomes correlating to laser dosimetry, CSC duration, and treatment cycles. These outcomes included expansion of cartilage layers (thickening), partial cartilage injuries, and full-thickness cartilage injuries. We determined therapy thresholds for laser output energy, cryogen spray cooling duration, and treatment cycles in the rabbit auricular model. These parameters are a starting point for future clinical procedures aimed at correcting external ear deformities.

3D additive manufactured 316L components microstructural features and changes induced by working life cycles

NASA Astrophysics Data System (ADS)

Pace, M. L.; Guarnaccio, A.; Dolce, P.; Mollica, D.; Parisi, G. P.; Lettino, A.; Medici, L.; Summa, V.; Ciancio, R.; Santagata, A.

2017-10-01

The ability of processing through laser beams different kinds of metallic powders for direct production of 3D components with complex geometries has been gaining an impressive and growing attention for specific industrial applications. The process which can be distinguished as Selective Laser Sintering or Selective Laser Melting is even considered, more generally, as Additive Manufacturing where layer by layer material is built by the interaction between a laser beam and a powder bed. The rapid heating of the powder due to the laser beam energy transfer process followed by a rapid cooling rate induces within the manufactured material a cellular structure with fine sub-grains, which are in the range of few hundreds of micrometers. These metastable structures, which are smaller than the grain size in conventionally manufactured 316L stainless steel components, can undertake towards a recrystallization process due to either heat or mechanical treatments. For instance, when sub-grain boundaries of the cells are enriched with Mo and higher concentration of dislocation, dynamical processes occur generating local residual stresses. In these circumstances the segregation of Mo in cell boundaries is out of thermodynamic equilibrium conditions so that microstructures and phases are metastable. In the range of 1100-1400 °C heat treatments a complete dissolution of Mo in the Fe matrix with a gradual disappearance of sub-microns cell is observed feeding the growth of larger austenitic sub-grains formation. It follows a higher degree of Mo dissolution in the material matrix and a decrease of dislocation's concentration (Saeidi et al., 2015) [1]. In the work here presented we point out which are the microstructural features of stainless steel 316L components realized by Additive Manufacturing. Furthermore, the occurrence of a microstructural evolution is presented after experiencing to fatigue of 80000 cycles some door joints obtained by this technique. A decrease of dislocation's number, an increase of twinning due to the growth of grains and to the release of local stresses can be hypothesized following that an important role could be played by the presence of dislocations in cell boundaries as well as oxides nano-inclusion formed in-situ during the Additive Manufacturing process (Saeidi et al., 2015) [2]. From these outcomes it is going to be presented how the 3D components produced by Additive Manufacturing could change and improve their features for potential industrial applications during life cycles and enhance such a behavior by taking carefully into account the laser parameters and its scanning speed.

The linac coherent light source single particle imaging road map

PubMed Central

Aquila, A.; Barty, A.; Bostedt, C.; Boutet, S.; Carini, G.; dePonte, D.; Drell, P.; Doniach, S.; Downing, K. H.; Earnest, T.; Elmlund, H.; Elser, V.; Gühr, M.; Hajdu, J.; Hastings, J.; Hau-Riege, S. P.; Huang, Z.; Lattman, E. E.; Maia, F. R. N. C.; Marchesini, S.; Ourmazd, A.; Pellegrini, C.; Santra, R.; Schlichting, I.; Schroer, C.; Spence, J. C. H.; Vartanyants, I. A.; Wakatsuki, S.; Weis, W. I.; Williams, G. J.

2015-01-01

Intense femtosecond x-ray pulses from free-electron laser sources allow the imaging of individual particles in a single shot. Early experiments at the Linac Coherent Light Source (LCLS) have led to rapid progress in the field and, so far, coherent diffractive images have been recorded from biological specimens, aerosols, and quantum systems with a few-tens-of-nanometers resolution. In March 2014, LCLS held a workshop to discuss the scientific and technical challenges for reaching the ultimate goal of atomic resolution with single-shot coherent diffractive imaging. This paper summarizes the workshop findings and presents the roadmap toward reaching atomic resolution, 3D imaging at free-electron laser sources. PMID:26798801

The linac coherent light source single particle imaging road map

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aquila, A.; Barty, A.; Bostedt, C.

Intense femtosecond x-ray pulses from free-electron laser sources allow the imaging of individual particles in a single shot. Early experiments at the Linac Coherent Light Source (LCLS) have led to rapid progress in the field and, so far, coherent diffractive images have been recorded from biological specimens, aerosols, and quantum systems with a few-tens-of-nanometers resolution. In March 2014, LCLS held a workshop to discuss the scientific and technical challenges for reaching the ultimate goal of atomic resolution with single-shot coherent diffractive imaging. This paper summarizes the workshop findings and presents the roadmap toward reaching atomic resolution, 3D imaging at free-electronmore » laser sources.« less

Research of beam conditioning technologies on SG-III laser facility

NASA Astrophysics Data System (ADS)

Zhang, Rui; Su, Jingqin; Yuan, Haoyu; Li, Ping; Tian, Xiaocheng; Wang, Jianjun; Dong, Jun; Zhang, Ying; Yuan, Qiang; Wang, Yuancheng; Zhou, Wei; Peng, Zhitao; Wang, Fang; Hu, Dongxia; Zhu, Qihua; Zheng, Wanguo; Zhang, Xiaomin

2014-12-01

Multi-FM SSD and CPP was experimentally studied in high fluence and will be equipped on all the beams of SG-III laser facility. The output spectrum of the cascade phase modulators are stable and the residual amplitude modulation is small. FM-to-AM effect caused by free-space propagation after using smoothing by spectral dispersion is theoretically analyzed. Results indicate inserting a dispersion grating in places with larger beam aperture could alleviate the FM-to- AM effect, suggesting minimizing free-space propagation and adopting image relay. Experiments taken on SG-III laser facility indicate when the number of color cycles (Nc) adopts 1, imposing of SSD with 3.3 times diffraction limit (TDL) did not lead to pinhole closure in the spatial filters of the preamplifier and main amplifier with 30-TDL pinhole size. The nonuniformity of the focal spot using Multi-FM SSD and CPP drops to 0.26, comparing to 0.84 only using CPP. The experiments solve some key technical problems using SSD and CPP on SG-III laser facility, and provide a flexible platform for laser-plasma interaction experiments. Combined beam smoothing and polarization smoothing are also analyzed. Simulation results indicate through adjusting dispersion directions of one-dimensional SSD beams in a quad, two-dimensional SSD could be obtained. The near field and far field properties of beams using polarization smoothing were also studied, including birefringent wedge and polarization control plate (PCP). By using PCP, cylindrical vector beams could be obtained. New solutions will be provided to solve the LPI problem encountered in indirect drive laser fusion.

Propagation of terahertz pulses in random media.

PubMed

Pearce, Jeremy; Jian, Zhongping; Mittleman, Daniel M

2004-02-15

We describe measurements of single-cycle terahertz pulse propagation in a random medium. The unique capabilities of terahertz time-domain spectroscopy permit the characterization of a multiply scattered field with unprecedented spatial and temporal resolution. With these results, we can develop a framework for understanding the statistics of broadband laser speckle. Also, the ability to extract information on the phase of the field opens up new possibilities for characterizing multiply scattered waves. We illustrate this with a simple example, which involves computing a time-windowed temporal correlation between fields measured at different spatial locations. This enables the identification of individual scattering events, and could lead to a new method for imaging in random media.

Interaction of intense laser pulses with gas for two-color THz generation and remote magnetometry

NASA Astrophysics Data System (ADS)

Johnson, Luke A.

The interaction of intense laser pulses with atmospheric gases is studied in two contexts: (i) the generation of broadband terahertz radiation via two-color photoionization currents in nitrogen, and (ii) the generation of an electromagnetic wakefield by the induced magnetization currents of oxygen. (i) A laser pulse propagation simulation code was developed to investigate the radiation patterns from two-color THz generation in nitrogen. Understanding the mechanism for conical, two-color THz furthers the development of broadband THz sources. Two-color photoionization produces a cycle-averaged current driving broadband, conically emitted THz radiation. The THz emission angle is found to be determined by an optical Cherenkov effect, occurring when the front velocity of the ionization induced current source is greater than the THz phase velocity. (ii) A laser pulse propagating in the atmosphere is capable of exciting a magnetic dipole transition in molecular oxygen. The resulting transient current creates a co-propagating electromagnetic field behind the laser pulse, i.e. the wakefield, which has a rotated polarization that depends on the background magnetic field. This effect is analyzed to determine it's suitability for remote atmospheric magnetometry for the detection of underwater and underground objects. In the proposed approach, Kerr self-focusing is used to bring a polarized, high-intensity, laser pulse to focus at a remote detection site where the laser pulse induces a ringing in the oxygen magnetization. The detection signature for underwater and underground objects is the change in the wakefield polarization between different measurement locations. The magnetic dipole transition line that is considered is the b-X transition band of oxygen near 762 nm.

Correlated electronic decay in expanding clusters triggered by intense XUV pulses from a Free-Electron-Laser

PubMed Central

Oelze, Tim; Schütte, Bernd; Müller, Maria; Müller, Jan P.; Wieland, Marek; Frühling, Ulrike; Drescher, Markus; Al-Shemmary, Alaa; Golz, Torsten; Stojanovic, Nikola; Krikunova, Maria

2017-01-01

Irradiation of nanoscale clusters and large molecules with intense laser pulses transforms them into highly-excited non- equilibrium states. The dynamics of intense laser-cluster interaction is encoded in electron kinetic energy spectra, which contain signatures of direct photoelectron emission as well as emission of thermalized nanoplasma electrons. In this work we report on a so far not observed spectrally narrow bound state signature in the electron kinetic energy spectra from mixed Xe core - Ar shell clusters ionized by intense extreme-ultraviolet (XUV) pulses from a free-electron-laser. This signature is attributed to the correlated electronic decay (CED) process, in which an excited atom relaxes and the excess energy is used to ionize the same or another excited atom or a nanoplasma electron. By applying the terahertz field streaking principle we demonstrate that CED-electrons are emitted at least a few picoseconds after the ionizing XUV pulse has ended. Following the recent finding of CED in clusters ionized by intense near-infrared laser pulses, our observation of CED in the XUV range suggests that this process is of general relevance for the relaxation dynamics in laser produced nanoplasmas. PMID:28098175

Watt-level widely tunable single-mode emission by injection-locking of a multimode Fabry-Perot quantum cascade laser

NASA Astrophysics Data System (ADS)

Chevalier, Paul; Piccardo, Marco; Anand, Sajant; Mejia, Enrique A.; Wang, Yongrui; Mansuripur, Tobias S.; Xie, Feng; Lascola, Kevin; Belyanin, Alexey; Capasso, Federico

2018-02-01

Free-running Fabry-Perot lasers normally operate in a single-mode regime until the pumping current is increased beyond the single-mode instability threshold, above which they evolve into a multimode state. As a result of this instability, the single-mode operation of these lasers is typically constrained to few percents of their output power range, this being an undesired limitation in spectroscopy applications. In order to expand the span of single-mode operation, we use an optical injection seed generated by an external-cavity single-mode laser source to force the Fabry-Perot quantum cascade laser into a single-mode state in the high current range, where it would otherwise operate in a multimode regime. Utilizing this approach, we achieve single-mode emission at room temperature with a tuning range of 36 cm-1 and stable continuous-wave output power exceeding 1 W at 4.5 μm. Far-field measurements show that a single transverse mode is emitted up to the highest optical power, indicating that the beam properties of the seeded Fabry-Perot laser remain unchanged as compared to free-running operation.

Effects of erbium, chromium:YSGG laser irradiation on root surface: morphological and atomic analytical studies.

PubMed

Kimura, Y; Yu, D G; Kinoshita, J; Hossain, M; Yokoyama, K; Murakami, Y; Nomura, K; Takamura, R; Matsumoto, K

2001-04-01

The purpose of this study was to investigate the morphological and atomic changes on the root surface by stereoscopy, field emission-scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (SEM-EDX) after erbium, chromium:yttrium, scandium, gallium, garnet (Er,Cr:YSGG) laser irradiation in vitro. There have been few reports on morphological and atomic analytical study on root surface by Er,Cr:YSGG laser irradiation. Eighteen extracted human premolar and molar teeth were irradiated on root surfaces at a vertical position with water-air spray by an Er,Cr:YSGG laser at the parameter of 5.0 W and 20 Hz for 5 sec while moving. The samples were then morphologically observed by stereoscopy and FE-SEM and examined atomic-analytically by SEM-EDX. Craters having rough but clean surfaces and no melting or carbonization were observed in the samples. An atomic analytical examination showed that the calcium ratio to phosphorus showed no significant changes between the control and irradiated areas (p > 0.01). These results showed that the Er,Cr:YSGG laser has a good cutting effect on root surface and causes no burning or melting after laser irradiation.

Comprehensive description of the Orion laser facility

NASA Astrophysics Data System (ADS)

Hopps, Nicholas; Oades, Kevin; Andrew, Jim; Brown, Colin; Cooper, Graham; Danson, Colin; Daykin, Simon; Duffield, Stuart; Edwards, Ray; Egan, David; Elsmere, Stephen; Gales, Steve; Girling, Mark; Gumbrell, Edward; Harvey, Ewan; Hillier, David; Hoarty, David; Horsfield, Colin; James, Steven; Leatherland, Alex; Masoero, Stephen; Meadowcroft, Anthony; Norman, Michael; Parker, Stefan; Rothman, Stephen; Rubery, Michael; Treadwell, Paul; Winter, David; Bett, Thomas

2015-06-01

The Orion laser facility at the atomic weapons establishment (AWE) in the UK has been operational since April 2013, fielding experiments that require both its long and short pulse capability. This paper provides a full description of the facility in terms of laser performance, target systems and diagnostics currently available. Inevitably, this is a snapshot of current capability—the available diagnostics and the laser capability are evolving continuously. The laser systems consist of ten beams, optimised around 1 ns pulse duration, which each provide a nominal 500 J at a wavelength of 351 nm. There are also two short pulse beams, which each provide 500 J in 0.5 ps at 1054 nm. There are options for frequency doubling one short pulse beam to enhance the pulse temporal contrast. More recently, further contrast enhancement, based on optical parametric amplification (OPA) in the front end with a pump pulse duration of a few ps, has been installed. An extensive suite of diagnostics are available for users, probing the optical emission, x-rays and particles produced in laser-target interactions. Optical probe diagnostics are also available. A description of the diagnostics is provided.

Potential efficiencies of open- and closed-cycle CO, supersonic, electric-discharge lasers

NASA Technical Reports Server (NTRS)

Monson, D. J.

1976-01-01

Computed open- and closed-cycle system efficiencies (laser power output divided by electrical power input) are presented for a CW carbon monoxide, supersonic, electric-discharge laser. Closed-system results include the compressor power required to overcome stagnation pressure losses due to supersonic heat addition and a supersonic diffuser. The paper shows the effect on the system efficiencies of varying several important parameters. These parameters include: gas mixture, gas temperature, gas total temperature, gas density, total discharge energy loading, discharge efficiency, saturated gain coefficient, optical cavity size and location with respect to the discharge, and supersonic diffuser efficiency. Maximum open-cycle efficiency of 80-90% is predicted; the best closed-cycle result is 60-70%.

Laser guide star pointing camera for ESO LGS Facilities

NASA Astrophysics Data System (ADS)

Bonaccini Calia, D.; Centrone, M.; Pedichini, F.; Ricciardi, A.; Cerruto, A.; Ambrosino, F.

2014-08-01

Every observatory using LGS-AO routinely has the experience of the long time needed to bring and acquire the laser guide star in the wavefront sensor field of view. This is mostly due to the difficulty of creating LGS pointing models, because of the opto-mechanical flexures and hysteresis in the launch and receiver telescope structures. The launch telescopes are normally sitting on the mechanical structure of the larger receiver telescope. The LGS acquisition time is even longer in case of multiple LGS systems. In this framework the optimization of the LGS systems absolute pointing accuracy is relevant to boost the time efficiency of both science and technical observations. In this paper we show the rationale, the design and the feasibility tests of a LGS Pointing Camera (LPC), which has been conceived for the VLT Adaptive Optics Facility 4LGSF project. The LPC would assist in pointing the four LGS, while the VLT is doing the initial active optics cycles to adjust its own optics on a natural star target, after a preset. The LPC allows minimizing the needed accuracy for LGS pointing model calibrations, while allowing to reach sub-arcsec LGS absolute pointing accuracy. This considerably reduces the LGS acquisition time and observations operation overheads. The LPC is a smart CCD camera, fed by a 150mm diameter aperture of a Maksutov telescope, mounted on the top ring of the VLT UT4, running Linux and acting as server for the client 4LGSF. The smart camera is able to recognize within few seconds the sky field using astrometric software, determining the stars and the LGS absolute positions. Upon request it returns the offsets to give to the LGS, to position them at the required sky coordinates. As byproduct goal, once calibrated the LPC can calculate upon request for each LGS, its return flux, its fwhm and the uplink beam scattering levels.

Near-Simultaneous Measurement of Ground Level Carbon Dioxide and Methane Concentrations with an Open-Path Tunable Diode Laser Sensor at the Bonanza Creek Long Term Ecological Research site near Fairbanks, Alaska

NASA Astrophysics Data System (ADS)

Bailey, D. M.; Miller, J. H. H.

2017-12-01

Beyond anthropogenic carbon emissions, the increase in atmospheric carbon from natural feedbacks such as thawing permafrost poses a risk to the global climate as global temperatures continue to increase. Permafrost is formally defined as soil that is continuously frozen for 24 consecutive months. These soils comprise nearly twenty-five percent of the Earth's terrestrial surface and possess twice the amount of carbon currently in the atmosphere. Continuous collection of carbon dioxide (CO2) and methane (CH4) concentrations is imperative in understanding seasonal and inter-annual variability of carbon feedbacks above thawing permafrost. A multi-year collaborative effort with the University of Alaska - Fairbanks, NASA Goddard Space Flight Center, and our group at George Washington University is underway to monitor these feedbacks near Fairbanks, Alaska. In June 2017, we deployed two open-path tunable diode laser sensors at the Bonanza Long Term Ecological Research Site for measurement of CO2 and CH4 concentrations. The open-path instrument (OPI) is an inexpensive, low-power sensor that collects spatially-integrated measurements of target molecules approximately 1.5 meters above ground level. With a total power burden of 18 W, the sensors ran exclusively on solar power for 15 days in a young thermokarst bog and 3.5 days at a rich fen site. Here we report on initial retrieval of diurnal cycles from each field site and compare our spatially-integrated measurements of CO2 and CH4. For CO2, the magnitude of the diurnal cycles show a strong dependence on daily weather at both field sites. These laser measurements are complemented by point measurements of CO2, temperature, pressure, and humidity made along the laser's optical path by non-dispersive infrared (NDIR) sensors.

Fabrication and Operation of a Nano-Optical Conveyor Belt

PubMed Central

Ryan, Jason; Zheng, Yuxin; Hansen, Paul; Hesselink, Lambertus

2015-01-01

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological and physical sciences over the past few decades. The progress made in this field invites further study of even smaller systems and at a larger scale, with tools that could be distributed more easily and made more widely available. Unfortunately, the fundamental laws of diffraction limit the minimum size of the focal spot of a laser beam, which makes particles smaller than a half-wavelength in diameter hard to trap and generally prevents an operator from discriminating between particles which are closer together than one half-wavelength. This precludes the optical manipulation of many closely-spaced nanoparticles and limits the resolution of optical-mechanical systems. Furthermore, manipulation using focused beams requires beam-forming or steering optics, which can be very bulky and expensive. To address these limitations in the system scalability of conventional optical trapping our lab has devised an alternative technique which utilizes near-field optics to move particles across a chip. Instead of focusing laser beams in the far-field, the optical near field of plasmonic resonators produces the necessary local optical intensity enhancement to overcome the restrictions of diffraction and manipulate particles at higher resolution. Closely-spaced resonators produce strong optical traps which can be addressed to mediate the hand-off of particles from one to the next in a conveyor-belt-like fashion. Here, we describe how to design and produce a conveyor belt using a gold surface patterned with plasmonic C-shaped resonators and how to operate it with polarized laser light to achieve super-resolution nanoparticle manipulation and transport. The nano-optical conveyor belt chip can be produced using lithography techniques and easily packaged and distributed. PMID:26381708

Fabrication and Operation of a Nano-Optical Conveyor Belt.

PubMed

Ryan, Jason; Zheng, Yuxin; Hansen, Paul; Hesselink, Lambertus

2015-08-26

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological and physical sciences over the past few decades. The progress made in this field invites further study of even smaller systems and at a larger scale, with tools that could be distributed more easily and made more widely available. Unfortunately, the fundamental laws of diffraction limit the minimum size of the focal spot of a laser beam, which makes particles smaller than a half-wavelength in diameter hard to trap and generally prevents an operator from discriminating between particles which are closer together than one half-wavelength. This precludes the optical manipulation of many closely-spaced nanoparticles and limits the resolution of optical-mechanical systems. Furthermore, manipulation using focused beams requires beam-forming or steering optics, which can be very bulky and expensive. To address these limitations in the system scalability of conventional optical trapping our lab has devised an alternative technique which utilizes near-field optics to move particles across a chip. Instead of focusing laser beams in the far-field, the optical near field of plasmonic resonators produces the necessary local optical intensity enhancement to overcome the restrictions of diffraction and manipulate particles at higher resolution. Closely-spaced resonators produce strong optical traps which can be addressed to mediate the hand-off of particles from one to the next in a conveyor-belt-like fashion. Here, we describe how to design and produce a conveyor belt using a gold surface patterned with plasmonic C-shaped resonators and how to operate it with polarized laser light to achieve super-resolution nanoparticle manipulation and transport. The nano-optical conveyor belt chip can be produced using lithography techniques and easily packaged and distributed.

Pulse-burst PIV in a high-speed wind tunnel

NASA Astrophysics Data System (ADS)

Beresh, Steven; Kearney, Sean; Wagner, Justin; Guildenbecher, Daniel; Henfling, John; Spillers, Russell; Pruett, Brian; Jiang, Naibo; Slipchenko, Mikhail; Mance, Jason; Roy, Sukesh

2015-09-01

Time-resolved particle image velocimetry (TR-PIV) has been achieved in a high-speed wind tunnel, providing velocity field movies of compressible turbulence events. The requirements of high-speed flows demand greater energy at faster pulse rates than possible with the TR-PIV systems developed for low-speed flows. This has been realized using a pulse-burst laser to obtain movies at up to 50 kHz, with higher speeds possible at the cost of spatial resolution. The constraints imposed by use of a pulse-burst laser are limited burst duration of 10.2 ms and a low duty cycle for data acquisition. Pulse-burst PIV has been demonstrated in a supersonic jet exhausting into a transonic crossflow and in transonic flow over a rectangular cavity. The velocity field sequences reveal the passage of turbulent structures and can be used to find velocity power spectra at every point in the field, providing spatial distributions of acoustic modes. The present work represents the first use of TR-PIV in a high-speed ground-test facility.

Laser Technology in Interplanetary Exploration: The Past and the Future

NASA Technical Reports Server (NTRS)

Smith, David E.

2000-01-01

Laser technology has been used in planetary exploration for many years but it has only been in the last decade that laser altimeters and ranging systems have been selected as flight instruments alongside cameras, spectrometers, magnetometers, etc. Today we have an active laser system operating at Mars and another destined for the asteroid Eros. A few years ago a laser ranging system on the Clementine mission changed much of our thinking about the moon and in a few years laser altimeters will be on their way to Mercury, and also to Europa. Along with the increased capabilities and reliability of laser systems has came the realization that precision ranging to the surface of planetary bodies from orbiting spacecraft enables more scientific problems to be addressed, including many associated with planetary rotation, librations, and tides. In addition, new Earth-based laser ranging systems working with similar systems on other planetary bodies in an asynchronous transponder mode will be able to make interplanetary ranging measurements at the few cm level and will advance our understanding of solar system dynamics and relativistic physics.

Metabolite-cycled STEAM and semi-LASER localization for MR spectroscopy of the human brain at 9.4T.

PubMed

Giapitzakis, Ioannis-Angelos; Shao, Tingting; Avdievich, Nikolai; Mekle, Ralf; Kreis, Roland; Henning, Anke

2018-04-01

Metabolite cycling (MC) is an MRS technique for the simultaneous acquisition of water and metabolite spectra that avoids chemical exchange saturation transfer effects and for which water may serve as a reference signal or contain additional information in functional or diffusion studies. Here, MC was developed for human investigations at ultrahigh field. MC-STEAM and MC-semi-LASER are introduced at 9.4T with an optimized inversion pulse and elaborate coil setup. Experimental and simulation results are given for the implementation of adiabatic inversion pulses for MC. The two techniques are compared, and the effect of frequency and phase correction based on the MC water spectra is evaluated. Finally, absolute quantification of metabolites is performed. The proposed coil configuration results in a maximum B1 + of 48 μΤ in a voxel within the occipital lobe. Frequency and phase correction of single acquisitions improve signal-to-noise ratio (SNR) and linewidth, leading to high-resolution spectra. The improvement of SNR of N-acetylaspartate (SNR NAA ) for frequency aligned data, acquired with MC-STEAM and MC-semi-LASER, are 37% and 30%, respectively (P < 0.05). Moreover, a doubling of the SNR NAA for MC-semi-LASER in comparison with MC-STEAM is observed (P < 0.05). Concentration levels for 18 metabolites from the human occipital lobe are reported, as acquired with both MC-STEAM and MC-semi-LASER. This work introduces a novel methodology for single-voxel MRS on a 9.4T whole-body scanner and highlights the advantages of semi-LASER compared to STEAM in terms of excitation profile. In comparison with MC-STEAM, MC-semi-LASER yields spectra with higher SNR. Magn Reson Med 79:1841-1850, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Advanced 2-micron Solid-state Laser for Wind and CO2 Lidar Applications

NASA Technical Reports Server (NTRS)

Yu, Jirong; Trieu, Bo C.; Petros, Mulugeta; Bai, Yingxin; Petzar, Paul J.; Koch, Grady J.; Singh, Upendra N.; Kavaya, Michael J.

2006-01-01

Significant advancements in the 2-micron laser development have been made recently. Solid-state 2-micron laser is a key subsystem for a coherent Doppler lidar that measures the horizontal and vertical wind velocities with high precision and resolution. The same laser, after a few modifications, can also be used in a Differential Absorption Lidar (DIAL) system for measuring atmospheric CO2 concentration profiles. The world record 2-micron laser energy is demonstrated with an oscillator and two amplifiers system. It generates more than one joule per pulse energy with excellent beam quality. Based on the successful demonstration of a fully conductive cooled oscillator by using heat pipe technology, an improved fully conductively cooled 2-micron amplifier was designed, manufactured and integrated. It virtually eliminates the running coolant to increase the overall system efficiency and reliability. In addition to technology development and demonstration, a compact and engineering hardened 2-micron laser is under development. It is capable of producing 250 mJ at 10 Hz by an oscillator and one amplifier. This compact laser is expected to be integrated to a lidar system and take field measurements. The recent achievements push forward the readiness of such a laser system for space lidar applications. This paper will review the developments of the state-of-the-art solid-state 2-micron laser.

Volcanic CO2 mapping and flux measurements at Campi Flegrei by Tunable Diode Laser absorption Spectroscopy

NASA Astrophysics Data System (ADS)

Pedone, Maria; Aiuppa, Alessandro; Giudice, Gaetano; Grassa, Fausto; Chiodini, Giovanni; Valenza, Mariano

2014-05-01

Near-infrared room-temperature Tunable Diode Lasers (TDL) have recently found increased usage in atmospheric chemistry and air monitoring research, but applications in Volcanology are still limited to a few examples. Here, we explored the potentiality of a commercial infrared laser unit (GasFinder 2.0 from Boreal Laser Ltd) to measurement of volcanic CO2 flux emissions. Our field tests were conducted at Campi Flegrei (near Pozzuoli, Southern Italy), where the GasFinder was used (during three campaigns in October 2012, January 2013 and May 2013) to repeatedly measure the path-integrated concentrations of CO2 along cross-sections of the atmospheric plumes of the two main fumarolic fields in the area (Solfatara and Pisciarelli). By using ad-hoc designed field-set-up and a tomographic post-processing routine, we resolved, for each of the 2 manifestations, the contour maps of CO2 concentrations in their atmospheric plumes, from the integration of which (and after multiplication by the plumes' transport speeds) the CO2 fluxes were finally obtained [1]. The so-calculated fluxes average of 490 tons/day, which agrees well with independent evaluations of Aiuppa et al. (2013) [2] (460 tons/day on average), and support a significant contribution of fumaroles to the total CO2 budget. The cumulative (fumarole [this study] +soil [2]) CO2 output from Campi Flegrei is finally evaluated at 1600 tons/day. The application of lasers to volcanic gas studies is still an emerging (though intriguing) research field, and requires more testing and validation experiments. We conclude that TDL technique may valuably assist CO2 flux quantification at a number of volcanic targets worldwide. [1] Pedone M. et al. (2013) Gold2013:abs:5563, Goldschmidt Conference, session 11a. [2] Aiuppa A. et al. (2013) Geochemistry Geophysics Geosystems. doi: 10.1002/ggge.20261. [3] Chiodini G. et al. (2010) Journal of Geophysical Research, Volume 115, B03205. doi:10.1029/2008JB006258.

Time-dependent quantum chemistry of laser driven many-electron molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen-Dang, Thanh-Tung; Couture-Bienvenue, Étienne; Viau-Trudel, Jérémy

2014-12-28

A Time-Dependent Configuration Interaction approach using multiple Feshbach partitionings, corresponding to multiple ionization stages of a laser-driven molecule, has recently been proposed [T.-T. Nguyen-Dang and J. Viau-Trudel, J. Chem. Phys. 139, 244102 (2013)]. To complete this development toward a fully ab-initio method for the calculation of time-dependent electronic wavefunctions of an N-electron molecule, we describe how tools of multiconfiguration quantum chemistry such as the management of the configuration expansion space using Graphical Unitary Group Approach concepts can be profitably adapted to the new context, that of time-resolved electronic dynamics, as opposed to stationary electronic structure. The method is applied tomore » calculate the detailed, sub-cycle electronic dynamics of BeH{sub 2}, treated in a 3–21G bound-orbital basis augmented by a set of orthogonalized plane-waves representing continuum-type orbitals, including its ionization under an intense λ = 800 nm or λ = 80 nm continuous-wave laser field. The dynamics is strongly non-linear at the field-intensity considered (I ≃ 10{sup 15} W/cm{sup 2}), featuring important ionization of an inner-shell electron and strong post-ionization bound-electron dynamics.« less

Characterization of extreme ultraviolet laser ablation mass spectrometry for actinide trace analysis and nanoscale isotopic imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Green, Tyler; Kuznetsov, Ilya; Willingham, David

The purpose of this research was to characterize Extreme Ultraviolet Time-of-Flight (EUV TOF) Laser Ablation Mass Spectrometry for high spatial resolution elemental and isotopic analysis. We compare EUV TOF results with Secondary Ionization Mass Spectrometry (SIMS) to orient the EUV TOF method within the overall field of analytical mass spectrometry. Using the well-characterized NIST 61x glasses, we show that the EUV ionization approach produces relatively few molecular ion interferences in comparison to TOF SIMS. We demonstrate that the ratio of element ion to element oxide ion is adjustable with EUV laser pulse energy and that the EUV TOF instrument hasmore » a sample utilization efficiency of 0.014%. The EUV TOF system also achieves a lateral resolution of 80 nm and we demonstrate this lateral resolution with isotopic imaging of closely spaced particles or uranium isotopic standard materials.« less

LARES: A new mission to improve the measurement of lense-thirring effect with Satellite Laser Ranging

NASA Astrophysics Data System (ADS)

Pavlis, E. C.; Ciufolini, I.; Paolozzi, A.

2012-12-01

LARES, Laser Relativity Satellite, is a spherical laser-ranged satellite, passive and covered with retroreflectors. It will be launched with ESA's new launch vehicle VEGA (ESA-ELV-ASI-AVIO) in early 2012. Its orbital elements will be: inclination 70° ± 1, semi-major axis 7830 km and near zero eccentricity. Its weight is about 387 kg and its radius 18.2 cm. It will be the single known most dense body orbiting Earth in the solar system, and the non-gravitational perturbations will be minimized by its very small 'cross-section-to-mass' ratio. The main objective of the LARES satellite is a test of the frame-dragging effect, a consequence of the gravitomagnetic field predicted by Einstein's theory of General Relativity. Together with the orbital data from LAGEOS and LAGEOS 2, it will allow a measurement of frame-dragging with an accuracy of a few percent.

Laser-aided material identification for the waste sorting process

NASA Astrophysics Data System (ADS)

Haferkamp, Heinz; Burmester, Ingo; Engel, Kai

1994-03-01

The LZH has carried out investigations in the field of rapid laser-supported material- identification systems for automatic material-sorting systems. The aim of this research is the fast identification of different sorts of plastics coming from recycled rubbish or electronic waste. Within a few milliseconds a spot on the sample which has to be identified is heated with a CO2 laser. The different and specific chemical and physical material properties of the examined sample cause a different temperature distribution on the surface which is measured with an IR thermographic system. This `thermal impulse response' has to be analyzed by means of a computer system. The results of previous investigations have shown that material identification of different sorts of plastics can possibly be done at a frequency of 30 Hz. Due to economic efficiency, a high velocity identification process is necessary to sort huge waste currents.

A new type of caesium clock: a laser-cooled atomic fountain.

NASA Astrophysics Data System (ADS)

Clairon, A.

1995-05-01

In recent years, progress has been made in the field of cooling neutral atoms using a laser. An initial application is the construction of a new type of atomic clock. Today it is easy to produce a gas of caesium atoms at a temperature of a few microkelvins, corresponding to a mean square velocity of the order of 1 cm/s; all that is needed is two laser diodes forming an optical soup in a low pressure caesium cell. In the longer term, these cooled atoms will make it possible to build clocks whose performance will be one or two orders of magnitude better than those that exist at present. A prototype caesium clock using cold atoms has been operating for over a year that the LPTF in the Paris observatory. This article describes its design principles and gives a brief presentation of the results obtained so far.

Universal feature in optical control of a p -wave Feshbach resonance

NASA Astrophysics Data System (ADS)

Peng, Peng; Zhang, Ren; Huang, Lianghui; Li, Donghao; Meng, Zengming; Wang, Pengjun; Zhai, Hui; Zhang, Peng; Zhang, Jing

2018-01-01

We report the experimental results on the optical control of a p -wave Feshbach resonance by utilizing a laser-driven bound-to-bound transition to shift the energy of a closed-channel molecule state. The magnetic field location for the p -wave resonance as a function of laser detuning can be captured by a simple formula with essentially one parameter, which describes how sensitively the resonance depends on the laser detuning. The key result of this work is to demonstrate, both experimentally and theoretically, that the ratio between this parameter for the m =0 component of the resonance and that for the m =±1 component, to a large extent, is universal. We also show that this optical control can create intriguing situations where interesting few- and many-body physics can occur, such as a p -wave resonance overlapping with an s -wave resonance or the three components of a p -wave resonance being degenerate.

A computer program for the design of optimum catalytic monoliths for CO2 lasers

NASA Technical Reports Server (NTRS)

Guinn, K.; Goldblum, S.; Noskowski, E.; Herz, R.

1990-01-01

Pulsed CO2 lasers have many applications in aeronautics, space research, weather monitoring and other areas. Full exploitation of the potential of these lasers is hampered by the dissociation of CO2 that occurs during laser operation. The development of closed-cycle CO2 lasers requires active CO-O2 recombination (CO oxidation) catalysts and design methods for implementation of catalysts inside lasers. The performance criteria and constraints involved in the design of catalyst configurations for use in a closed-cycle laser are discussed, and several design studies performed with a computerized design program that was written are presented. Trade-offs between catalyst activity and dimensions, flow channel dimensions, pressure drop, O2 conversion and other variables are discussed.

Research of epidermal cellular vegetal cycle of intravascular low level laser irradiation in treatment of psoriasis

NASA Astrophysics Data System (ADS)

Zhu, Jing; Bao, Xiaoqing; Zhang, Mei-Jue

2005-07-01

Objective: To research epidermal cellular vegetal cycle and the difference of DNA content between pre and post Intravascular Low Level Laser Irradiation treatment of psoriasis. Method: 15 patients suffered from psoriasis were treated by intravascular low level laser irradiation (output power: 4-5mw, 1 hour per day, a course of treatment is 10 days). We checked the different DNA content of epidermal cell between pre and post treatment of psoriasis and 8 natural human. Then the percentage of each phase among the whole cellular cycle was calculated and the statistical analysis was made. Results: The mean value of G1/S phase is obviously down while G2+M phase increased obviously. T test P<0.05.The related statistical analysis showed significant difference between pre and post treatments. Conclusions: The Intravascular Low Level Laser Irradiation (ILLLI) in treatment of psoriasis is effective according to the research of epidermal cellular vegetal cycle and the difference DNA content of Intravascular Low Level Laser Irradiation between pre and post treatment of psoriasis

Designing Catalytic Monoliths For Closed-Cycle CO2 Lasers

NASA Technical Reports Server (NTRS)

Guinn, Keith; Herz, Richard K.; Goldblum, Seth; Noskowski, ED

1992-01-01

LASCAT (Design of Catalytic Monoliths for Closed-Cycle Carbon Dioxide Lasers) computer program aids in design of catalyst in monolith by simulating effects of design decisions on performance of laser. Provides opportunity for designer to explore tradeoffs among activity and dimensions of catalyst, dimensions of monolith, pressure drop caused by flow of gas through monolith, conversion of oxygen, and other variables. Written in FORTRAN 77.

Do dielectric nanostructures turn metallic in high-electric dc fields?

PubMed

Silaeva, E P; Arnoldi, L; Karahka, M L; Deconihout, B; Menand, A; Kreuzer, H J; Vella, A

2014-11-12

Three-dimensional dielectric nanostructures have been analyzed using field ion microscopy (FIM) to study the electric dc field penetration inside these structures. The field is proved to be screened within a few nanometers as theoretically calculated taking into account the high-field impact ionization process. Moreover, the strong dc field of the order of 0.1 V/Å at the surface inside a dielectric nanostructure modifies its band structure leading to a strong band gap shrinkage and thus to a strong metal-like optical absorption near the surface. This metal-like behavior was theoretically predicted using first-principle calculations and experimentally proved using laser-assisted atom probe tomography (APT). This work opens up interesting perspectives for the study of the performance of all field-effect nanodevices, such as nanotransistor or super capacitor, and for the understanding of the physical mechanisms of field evaporation of dielectric nanotips in APT.

Perturbation-theory analysis of ionization by a chirped few-cycle attosecond pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pronin, E. A.; Starace, Anthony F.; Peng Liangyou

2011-07-15

The angular distribution of electrons ionized from an atom by a chirped few-cycle attosecond pulse is analyzed using perturbation theory (PT), keeping terms in the transition amplitude up to second order in the pulse electric field. The dependence of the asymmetry in the ionized electron distributions on both the chirp and the carrier-envelope phase (CEP) of the pulse are explained using a simple analytical formula that approximates the exact PT result. This approximate formula (in which the chirp dependence is explicit) reproduces reasonably well the chirp-dependent oscillations of the electron angular distribution asymmetries found numerically by Peng et al. [Phys.more » Rev. A 80, 013407 (2009)]. It can also be used to determine the chirp rate of the attosecond pulse from the measured electron angular distribution asymmetry.« less

Scaling of Energy Deposition in Fast Ignition Targets

NASA Astrophysics Data System (ADS)

Campbell, R. B.; Welch, Dale

2005-10-01

We examine the scaling to ignition of the energy deposition of laser generated electrons in compressed fast ignition cores. Relevant cores have densities of several hundred g/cm^3, with a few keV initial temperature. As the laser intensities increase approaching ignition systems, on the order of a few 10^21W/cm^2, the hot electron energies expected to approach 100MeV[1]. Most certainly anomalous processes must play a role in the energy transfer, but the exact nature of these processes, as well as a practical way to model them, remain open issues. Traditional PIC explicit methods are limited to low densities on current and anticipated computing platforms, so the study of relevant parameter ranges has received so far little attention. We use LSP[2] to examine a relativistic electron beam (presumed generated from a laser plasma interaction) of legislated energy and angular distribution is injected into a 3D block of compressed DT. Collective effects will determine the stopping, most likely driven by magnetic field filamentation. The scaling of the stopping as a function of block density and temperature, as well as hot electron current and laser intensity is presented. Sub-grid models may be profitably used and degenerate effects included in the solution of this problem. Sandia is operated by Sandia Corporation, for the USDOE. [1] A. Pukhov, et. al., Phys. Plas. 6, p2847 (1999) [2] D. R. Welch et al., Comput. Phys.Commun. 164, p183 (2004).

Stable electron beams from laser wakefield acceleration with few-terawatt driver using a supersonic air jet

NASA Astrophysics Data System (ADS)

Boháček, K.; Kozlová, M.; Nejdl, J.; Chaulagain, U.; Horný, V.; Krůs, M.; Ta Phuoc, K.

2018-03-01

The generation of stable electron beams produced by the laser wakefield acceleration mechanism with a few-terawatt laser system (600 mJ, 50 fs) in a supersonic synthetic air jet is reported and the requirements necessary to build such a stable electron source are experimentally investigated in conditions near the bubble regime threshold. The resulting electron beams have stable energies of (17.4 ± 1.1) MeV and an energy spread of (13.5 ± 1.5) MeV (FWHM), which has been achieved by optimizing the properties of the supersonic gas jet target for the given laser system. Due to the availability of few-terawatt laser systems in many laboratories around the world these stable electron beams open possibilities for applications of this type of particle source.

Current and long-term technologies of laser therapy

NASA Astrophysics Data System (ADS)

Ulashcyk, Vladimir S.; Volotovskaya, Anna V.

2007-06-01

Laser therapy, using low-energy laser radiation, is being more and more applied. The most applied technology is transcutaneous radiation of tissues by laser radiation. Originally, a direct action on a pathological site was mostly used, but recently more attention is given to reflexogenic areas, acupuncture points, and endocrine organ projection sites. The development of light-conductive engineering made it possible to practically apply intraorgan laser therapy. This technology is widely spread in gynecology, otorhinolaryngology, urology, gastroenterology, etc. Close to it are different versions of intratissue laser therapy (intraosteal, periosteal, myofascial). A special kind of laser therapy is laser hemotherapy. Depending on the techniques and protocol of its application, there are extracorporeal, intravascular, and supravenous ways of action. According to our comparative investigations, supravenous hemotherapy by its therapeutic efficacy and major medicinal effects can be well compared with intravascular laser hemotherapy. With good prospects and efficiency is laser therapy as a combination of laser and other physical factors. Magnetolaser therapy has been scientifically substantiated and practically applied so far. Theoretically and experimentally substantiated is a combined application of laser radiation and physical factors such as ultrasound, direct current field, vacuum, cryotherapy, etc. Experimental research and few so far clinical observations are indicative of prospects of a complex application of laser radiation and drugs. To improve light absorption, laser radiation is combined with different dyes. Photodynamic therapy, originally used in oncology, is applied today in treating different diseases. We showed a possibility of using a number of drugs possessing simultaneously photosensitizing properties to this end. Laser radiation significantly influences pharmacokinetics and pharmacodynamics of drugs, which gives reason to practically implement laser technologies, based on pharmacomodulating action of laser radiation, to practical medicine.

IRIDE: Interdisciplinary research infrastructure based on dual electron linacs and lasers

NASA Astrophysics Data System (ADS)

Ferrario, M.; Alesini, D.; Alessandroni, M.; Anania, M. P.; Andreas, S.; Angelone, M.; Arcovito, A.; Arnesano, F.; Artioli, M.; Avaldi, L.; Babusci, D.; Bacci, A.; Balerna, A.; Bartalucci, S.; Bedogni, R.; Bellaveglia, M.; Bencivenga, F.; Benfatto, M.; Biedron, S.; Bocci, V.; Bolognesi, M.; Bolognesi, P.; Boni, R.; Bonifacio, R.; Boscherini, F.; Boscolo, M.; Bossi, F.; Broggi, F.; Buonomo, B.; Calo, V.; Catone, D.; Capogni, M.; Capone, M.; Cassou, K.; Castellano, M.; Castoldi, A.; Catani, L.; Cavoto, G.; Cherubini, N.; Chirico, G.; Cestelli-Guidi, M.; Chiadroni, E.; Chiarella, V.; Cianchi, A.; Cianci, M.; Cimino, R.; Ciocci, F.; Clozza, A.; Collini, M.; Colo, G.; Compagno, A.; Contini, G.; Coreno, M.; Cucini, R.; Curceanu, C.; Curciarello, F.; Dabagov, S.; Dainese, E.; Davoli, I.; Dattoli, G.; De Caro, L.; De Felice, P.; De Leo, V.; Dell Agnello, S.; Della Longa, S.; Delle Monache, G.; De Spirito, M.; Di Cicco, A.; Di Donato, C.; Di Gioacchino, D.; Di Giovenale, D.; Di Palma, E.; Di Pirro, G.; Dodaro, A.; Doria, A.; Dosselli, U.; Drago, A.; Dupraz, K.; Escribano, R.; Esposito, A.; Faccini, R.; Ferrari, A.; Filabozzi, A.; Filippetto, D.; Fiori, F.; Frasciello, O.; Fulgentini, L.; Gallerano, G. P.; Gallo, A.; Gambaccini, M.; Gatti, C.; Gatti, G.; Gauzzi, P.; Ghigo, A.; Ghiringhelli, G.; Giannessi, L.; Giardina, G.; Giannini, C.; Giorgianni, F.; Giovenale, E.; Giulietti, D.; Gizzi, L.; Guaraldo, C.; Guazzoni, C.; Gunnella, R.; Hatada, K.; Iannone, M.; Ivashyn, S.; Jegerlehner, F.; Keeffe, P. O.; Kluge, W.; Kupsc, A.; Labate, L.; Levi Sandri, P.; Lombardi, V.; Londrillo, P.; Loreti, S.; Lorusso, A.; Losacco, M.; Lukin, A.; Lupi, S.; Macchi, A.; Magazù, S.; Mandaglio, G.; Marcelli, A.; Margutti, G.; Mariani, C.; Mariani, P.; Marzo, G.; Masciovecchio, C.; Masjuan, P.; Mattioli, M.; Mazzitelli, G.; Merenkov, N. P.; Michelato, P.; Migliardo, F.; Migliorati, M.; Milardi, C.; Milotti, E.; Milton, S.; Minicozzi, V.; Mobilio, S.; Morante, S.; Moricciani, D.; Mostacci, A.; Muccifora, V.; Murtas, F.; Musumeci, P.; Nguyen, F.; Orecchini, A.; Organtini, G.; Ottaviani, P. L.; Pace, C.; Pace, E.; Paci, M.; Pagani, C.; Pagnutti, S.; Palmieri, V.; Palumbo, L.; Panaccione, G. C.; Papadopoulos, C. F.; Papi, M.; Passera, M.; Pasquini, L.; Pedio, M.; Perrone, A.; Petralia, A.; Petrarca, M.; Petrillo, C.; Petrillo, V.; Pierini, P.; Pietropaolo, A.; Pillon, M.; Polosa, A. D.; Pompili, R.; Portoles, J.; Prosperi, T.; Quaresima, C.; Quintieri, L.; Rau, J. V.; Reconditi, M.; Ricci, A.; Ricci, R.; Ricciardi, G.; Ricco, G.; Ripani, M.; Ripiccini, E.; Romeo, S.; Ronsivalle, C.; Rosato, N.; Rosenzweig, J. B.; Rossi, A. A.; Rossi, A. R.; Rossi, F.; Rossi, G.; Russo, D.; Sabatucci, A.; Sabia, E.; Sacchetti, F.; Salducco, S.; Sannibale, F.; Sarri, G.; Scopigno, T.; Sekutowicz, J.; Serafini, L.; Sertore, D.; Shekhovtsova, O.; Spassovsky, I.; Spadaro, T.; Spataro, B.; Spinozzi, F.; Stecchi, A.; Stellato, F.; Surrenti, V.; Tenore, A.; Torre, A.; Trentadue, L.; Turchini, S.; Vaccarezza, C.; Vacchi, A.; Valente, P.; Venanzoni, G.; Vescovi, S.; Villa, F.; Zanotti, G.; Zema, N.; Zobov, M.; Zomer, F.

2014-03-01

This paper describes the scientific aims and potentials as well as the preliminary technical design of IRIDE, an innovative tool for multi-disciplinary investigations in a wide field of scientific, technological and industrial applications. IRIDE will be a high intensity "particles factory", based on a combination of high duty cycle radio-frequency superconducting electron linacs and of high energy lasers. Conceived to provide unique research possibilities for particle physics, for condensed matter physics, chemistry and material science, for structural biology and industrial applications, IRIDE will open completely new research possibilities and advance our knowledge in many branches of science and technology. IRIDE is also supposed to be realized in subsequent stages of development depending on the assigned priorities.

Integrated RGB laser light module for autostereoscopic outdoor displays

NASA Astrophysics Data System (ADS)

Reitterer, Jörg; Fidler, Franz; Hambeck, Christian; Saint Julien-Wallsee, Ferdinand; Najda, Stephen; Perlin, Piotr; Stanczyk, Szymon; Czernecki, Robert; McDougall, Stewart D.; Meredith, Wyn; Vickers, Garrie; Landles, Kennedy; Schmid, Ulrich

2015-02-01

We have developed highly compact RGB laser light modules to be used as light sources in multi-view autostereoscopic outdoor displays and projection devices. Each light module consists of an AlGaInP red laser diode, a GaInN blue laser diode, a GaInN green laser diode, as well as a common cylindrical microlens. The plano-convex microlens is a so-called "fast axis collimator", which is widely used for collimating light beams emitted from high-power laser diode bars, and has been optimized for polychromatic RGB laser diodes. The three light beams emitted from the red, green, and blue laser diodes are collimated in only one transverse direction, the so-called "fast axis", and in the orthogonal direction, the so-called "slow axis", the beams pass the microlens uncollimated. In the far field of the integrated RGB light module this produces Gaussian beams with a large ellipticity which are required, e.g., for the application in autostereoscopic outdoor displays. For this application only very low optical output powers of a few milliwatts per laser diode are required and therefore we have developed tailored low-power laser diode chips with short cavity lengths of 250 μm for red and 300 μm for blue. Our RGB laser light module including the three laser diode chips, associated monitor photodiodes, the common microlens, as well as the hermetically sealed package has a total volume of only 0.45 cm³, which to our knowledge is the smallest RGB laser light source to date.

Laser cutting of various materials: Kerf width size analysis and life cycle assessment of cutting process

NASA Astrophysics Data System (ADS)

Yilbas, Bekir Sami; Shaukat, Mian Mobeen; Ashraf, Farhan

2017-08-01

Laser cutting of various materials including Ti-6Al-4V alloy, steel 304, Inconel 625, and alumina is carried out to assess the kerf width size variation along the cut section. The life cycle assessment is carried out to determine the environmental impact of the laser cutting in terms of the material waste during the cutting process. The kerf width size is formulated and predicted using the lump parameter analysis and it is measured from the experiments. The influence of laser output power and laser cutting speed on the kerf width size variation is analyzed using the analytical tools including scanning electron and optical microscopes. In the experiments, high pressure nitrogen assisting gas is used to prevent oxidation reactions in the cutting section. It is found that the kerf width size predicted from the lump parameter analysis agrees well with the experimental data. The kerf width size variation increases with increasing laser output power. However, this behavior reverses with increasing laser cutting speed. The life cycle assessment reveals that material selection for laser cutting is critical for the environmental protection point of view. Inconel 625 contributes the most to the environmental damages; however, recycling of the waste of the laser cutting reduces this contribution.

Split ring resonator based THz-driven electron streak camera featuring femtosecond resolution

PubMed Central

Fabiańska, Justyna; Kassier, Günther; Feurer, Thomas

2014-01-01

Through combined three-dimensional electromagnetic and particle tracking simulations we demonstrate a THz driven electron streak camera featuring a temporal resolution on the order of a femtosecond. The ultrafast streaking field is generated in a resonant THz sub-wavelength antenna which is illuminated by an intense single-cycle THz pulse. Since electron bunches and THz pulses are generated with parts of the same laser system, synchronization between the two is inherently guaranteed. PMID:25010060

Time-Synchronized Continuous Wave Laser Induced Fluorescence Velocity Measurements of a 600 Watt Hall Thruster

DTIC Science & Technology

2015-07-01

channel and near- field plume region of a 600 W Hall thruster operating on xenon. Results show significant fluctuations in LIF signal intensity... LIF signal intensity (corre- lated with the density of the probed excited metastable state) in time during the discharge current cycle, with the peak...fluorescence ( LIF ).1 LIF provides the opportunity to investigate plasma sources non-intrusively with higher spatial resolution (typically < 1 mm) than

Estimating aboveground live understory vegetation carbon in the United States

Treesearch

Kristofer D Johnson; Grant M Domke; Matthew B Russell; Brian Walters; John Hom; Alicia Peduzzi; Richard Birdsey; Katelyn Dolan; Wenli Huang

2017-01-01

Despite the key role that understory vegetation plays in ecosystems and the terrestrial carbon cycle, it is often overlooked and has few quantitative measurements, especially at national scales. To understand the contribution of understory carbon to the United States (US) carbon budget, we developed an approach that relies on field measurements of understory vegetation...

Femtosecond solid-state laser based on a few-layered black phosphorus saturable absorber.

PubMed

Su, Xiancui; Wang, Yiran; Zhang, Baitao; Zhao, Ruwei; Yang, Kejian; He, Jingliang; Hu, Qiangqiang; Jia, Zhitai; Tao, Xutang

2016-05-01

In this Letter, a high-quality, few-layered black phosphorus (BP) saturable absorber (SA) was fabricated successfully, and a femtosecond solid-state laser modulated by BP-SA was experimentally demonstrated for the first time, to the best of our knowledge. Pulses as short as 272 fs were achieved with an average output power of 0.82 W, corresponding to the pulse energy of 6.48 nJ and peak power of 23.8 MW. So far, these represent the shortest pulse duration and highest output power ever obtained with a BP-based mode-locked solid-state laser. The results indicate the promising potential of few-layered BP-SA for applications in solid-state femtosecond mode-locked lasers.

High-speed fuel tracer fluorescence and OH radical chemiluminescence imaging in a spark-ignition direct-injection engine

NASA Astrophysics Data System (ADS)

Smith, James D.; Sick, Volker

2005-11-01

An innovative technique has been demonstrated to achieve crank-angle-resolved planar laser-induced fluorescence (PLIF) of fuel followed by OH* chemiluminescence imaging in a firing direct-injected spark-ignition engine. This study used two standard KrF excimer lasers to excite toluene for tracking fuel distribution. The intensified camera system was operated at single crank-angle resolution at 2000 revolutions per minute (RPM) for 500 consecutive cycles. Through this work, it has been demonstrated that toluene and OH* can be imaged through the same optical setup while similar signal levels are obtained from both species, even at these high rates. The technique is useful for studying correlations between fuel distribution and subsequent ignition and flame propagation without the limitations of phase-averaging imaging approaches. This technique is illustrated for the effect of exhaust gas recirculation on combustion and will be useful for studies of misfire causes. Finally, a few general observations are presented as to the effect of preignition fuel distribution on subsequent combustion.

LAWS (Laser Atmospheric Wind Sounder) earth observing system

NASA Technical Reports Server (NTRS)

1988-01-01

Wind profiles can be measured from space using current technology. These wind profiles are essential for answering many of the interdisciplinary scientific questions to be addressed by EOS, the Earth Observing System. This report provides guidance for the development of a spaceborne wind sounder, the Laser Atmospheric Wind Sounder (LAWS), discussing the current state of the technology and reviewing the scientific rationale for the instrument. Whether obtained globally from the EOS polar platform or in the tropics and subtropics from the Space Station, wind profiles from space will provide essential information for advancing the skill of numerical weather prediction, furthering knowledge of large-scale atmospheric circulation and climate dynamics, and improving understanding of the global biogeochemical and hydrologic cycles. The LAWS Instrument Panel recommends that it be given high priority for new instrument development because of the pressing scientific need and the availability of the necessary technology. LAWS is to measure wind profiles with an accuracy of a few meters per second and to sample at intervals of 100 km horizontally for layers km thick.

High-speed fuel tracer fluorescence and OH radical chemiluminescence imaging in a spark-ignition direct-injection engine.

PubMed

Smith, James D; Sick, Volker

2005-11-01

An innovative technique has been demonstrated to achieve crank-angle-resolved planar laser-induced fluorescence (PLIF) of fuel followed by OH* chemiluminescence imaging in a firing direct-injected spark-ignition engine. This study used two standard KrF excimer lasers to excite toluene for tracking fuel distribution. The intensified camera system was operated at single crank-angle resolution at 2000 revolutions per minute (RPM) for 500 consecutive cycles. Through this work, it has been demonstrated that toluene and OH* can be imaged through the same optical setup while similar signal levels are obtained from both species, even at these high rates. The technique is useful for studying correlations between fuel distribution and subsequent ignition and flame propagation without the limitations of phase-averaging imaging approaches. This technique is illustrated for the effect of exhaust gas recirculation on combustion and will be useful for studies of misfire causes. Finally, a few general observations are presented as to the effect of preignition fuel distribution on subsequent combustion.

Catalytic Oxidation of CO for Closed-Cycle CO2 Lasers

NASA Technical Reports Server (NTRS)

Miller, I. M.; Schryer, D. R.; Hess, R. V.; Sidney, B. D.; Wood, G. M., Jr.; Paulin, P. A.; Upchurch, B. T.; Brown, K. G.

1987-01-01

Stoichiometric mixture converted completely. High-energy pulsed CO2 lasers have potential for measuring many different features of atmosphere of Earth and particularly useful on airborne or space platforms. For this application, laser must be operated in closed cycle to conserve gas, especially if rare nonradioactive isotopes of carbon and oxygen used. However, laser discharge decomposes fraction of CO2 to CO and O2, causing rapid loss in power leading to erratic behavior. To maintain operation, CO and O2 must be recombined to form CO2.

Miscellaneous Lasing Actions in Organo-Lead Halide Perovskite Films.

PubMed

Duan, Zonghui; Wang, Shuai; Yi, Ningbo; Gu, Zhiyuan; Gao, Yisheng; Song, Qinghai; Xiao, Shumin

2017-06-21

Lasing actions in organo-lead halide perovskite films have been heavily studied in the past few years. However, due to the disordered nature of synthesized perovskite films, the lasing actions are usually understood as random lasers that are formed by multiple scattering. Herein, we demonstrate the miscellaneous lasing actions in organo-lead halide perovskite films. In addition to the random lasers, we show that a single or a few perovskite microparticles can generate laser emissions with their internal resonances instead of multiple scattering among them. We experimentally observed and numerically confirmed whispering gallery (WG)-like microlasers in polygon shaped and other deformed microparticles. Meanwhile, owing to the nature of total internal reflection and the novel shape of the nanoparticle, the size of the perovskite WG laser can be significantly decreased to a few hundred nanometers. Thus, wavelength-scale lead halide perovskite lasers were realized for the first time. All of these laser behaviors are complementary to typical random lasers in perovskite film and will help the understanding of lasing actions in complex lead halide perovskite systems.

Measuring carbon and oxygen isotope signals of photosynthesis and respiration: first field results from a chamber system coupled to tunable diode laser spectrometers

NASA Astrophysics Data System (ADS)

Wingate, L.; Burlett, R.; Bosc, A.; Cross, A.; Devaux, M.; Grace, J.; Loustau, D.; Seibt, U.; Ogée, J.

2007-12-01

Studying the carbon and oxygen stable isotope signals from plants and soils can help us gain insight to mechanistic processes responsible for the net exchange of CO2 and water cycled between terrestrial ecosystems and the atmosphere. Chamber field measurements of component fluxes and their isotopic composition have been reported for a few ecosystems. These observations have revealed that isotopic signals for carbon and oxygen are dynamic over relatively short time scales (hrs and days) for both branches and soils (Seibt et al., 2006a; 2006b; Wingate et al., 2007), and not fully explained by currently available models (Seibt et al., 2006b; Wingate et al., 2007). Ecosystem isotope studies have been limited by flask sampling requirements in the past. To evaluate and refine our models of isotopic fractionation by plants and soil, we need high resolution continuous isotopic measurements over the growing season for different ecosystems. In this study, we coupled chambers with tunable diode laser spectroscopy techniques in the field to continuously capture the isotopic signals from the most important component fluxes contributing to the net ecosystem exchange of CO2 in a Pinus pinaster forest in south-west France. We obtained profiles of the carbon and oxygen isotope content of CO2 within and above the forest canopy. In addition, we measured branch photosynthetic 13C and 18O discrimination alongside the 13C and 18O isotopic composition of the branch, stem and soil respiration during a 6-month period in 2007. In this talk, we will present the first results from this field campaign. References Seibt, U., Wingate, L., Berry, J.A. and Lloyd, J. (2006a) Non steady state effects in diurnal 18O discrimination by Picea sitchensis branches in the field. Plant, Cell and Environment Vol 29, 928-939. Seibt, U., Wingate, L., Lloyd, J. and Berry, J.A. (2006b) Diurnally variable δ18O signatures of soil CO2 fluxes indicate carbonic anhydrase activity in a forest soil. JGR-Biogeosciences, Vol. 111, G04005, doi:10.1029/2006JG000177. Seibt, U., Wingate, L. and Berry, J.A. (2007) Nocturnal stomatal conductance effects on the δ18O of foliage gas exchange observed in two forest ecosystems. Tree Physiology, Vol. 27, 585-595. Wingate, L., Seibt, U., Moncrieff, J.B., Jarvis, P.G. and Lloyd, J. (2007) Variations in 13C discrimination during CO2 exchange by Picea sitchensis branches in the field. Plant, Cell and Environment doi: 10.1111/j.1365-3040.2007.01647.

Linking high harmonics from gases and solids.

PubMed

Vampa, G; Hammond, T J; Thiré, N; Schmidt, B E; Légaré, F; McDonald, C R; Brabec, T; Corkum, P B

2015-06-25

When intense light interacts with an atomic gas, recollision between an ionizing electron and its parent ion creates high-order harmonics of the fundamental laser frequency. This sub-cycle effect generates coherent soft X-rays and attosecond pulses, and provides a means to image molecular orbitals. Recently, high harmonics have been generated from bulk crystals, but what mechanism dominates the emission remains uncertain. To resolve this issue, we adapt measurement methods from gas-phase research to solid zinc oxide driven by mid-infrared laser fields of 0.25 volts per ångström. We find that when we alter the generation process with a second-harmonic beam, the modified harmonic spectrum bears the signature of a generalized recollision between an electron and its associated hole. In addition, we find that solid-state high harmonics are perturbed by fields so weak that they are present in conventional electronic circuits, thus opening a route to integrate electronics with attosecond and high-harmonic technology. Future experiments will permit the band structure of a solid to be tomographically reconstructed.

Self-synchronizing Schlieren photography and interferometry for the visualization of unsteady transonic flows

NASA Technical Reports Server (NTRS)

Kadlec, R.

1979-01-01

The use of self synchronizing stroboscopic Schlieren and laser interferometer systems to obtain quantitative space time measurements of distinguished flow surfaces, steakline patterns, and the density field of two dimensional flows that exhibit a periodic content was investigated. A large field single path stroboscopic Schlieren system was designed, constructed and successfully applied to visualize four periodic flows: near wake behind an oscillating airfoil; edge tone sound generation; 2-D planar wall jet; and axisymmetric pulsed sonic jet. This visualization technique provides an effective means of studying quasi-periodic flows in real time. The image on the viewing screen is a spatial signal average of the coherent periodic motion rather than a single realization, the high speed motion of a quasi-periodic flow can be reconstructed by recording photographs of the flow at different fixed time delays in one cycle. The preliminary design and construction of a self synchronizing stroboscopic laser interferometer with a modified Mach-Zehnder optical system is also reported.

Ultrafast all-optical control of the magnetization in magnetic dielectrics

NASA Astrophysics Data System (ADS)

Kirilyuk, Andrei; Kimel, Alexey; Hansteen, Fredrik; Rasing, Theo; Pisarev, Roman V.

2006-08-01

The purpose of this review is to summarize the recent progress on laser-induced magnetization dynamics in magnetic dielectrics. Due to the slow phonon-magnon interaction in these materials, direct thermal effects of the laser excitation can only be seen on the time scale of almost a nanosecond and thus are clearly distinguished from the ultrafast nonthermal effects. However, laser pulses are shown to indirectly modify the magnetic anisotropy in rare-earth orthoferrites via the crystal field, and to bring about spin reorientation within a few picoseconds. More interesting, however, are the direct nonthermal effects of light on spin systems. We demonstrate coherent optical control of the magnetization in ferrimagnetic garnet films on a femtosecond time scale through a combination of two different ultrafast and nonthermal photomagnetic effects and by employing multiple pump pulses. Linearly polarized laser pulses are shown to create a long-lived modification of the magnetocrystalline anisotropy via optically induced electron transfer between nonequivalent ion sites. In addition, circularly polarized pulses are shown to act as strong transient magnetic field pulses originating from the nonabsorptive inverse Faraday effect. An all-optical scheme of excitation and detection of different antiferromagnetic resonance modes with frequencies of up to 500GHz will be discussed as well. The reported effects open new and exciting possibilities for ultrafast manipulation of spins by light and provide new insight into the physics of magnetism on ultrafast time scales.

Analysis of optical scheme for medium-range directed energy laser weapon system

NASA Astrophysics Data System (ADS)

Jabczyński, Jan K.; Kaśków, Mateusz; Gorajek, Łukasz; Kopczyński, Krzysztof

2017-10-01

The relations between range of operation and aperture of laser weapon system were investigated, taking into account diffraction and technical limitations as beam quality, accuracy of point tracking, technical quality of optical train, etc. As a result for the medium ranges of 1 - 2 km we restricted the analysis to apertures not wider than 150 mm and the optical system without adaptive optics. To choose the best laser beam shape, the minimization of aperture losses and thermooptical effects inside optics as well as the effective width of laser beam in far field should be taken into account. We have analyzed theoretically such a problem for the group of a few most interesting from that point of view profiles including for reference two limiting cases of Gaussian beam and `top hat' profile. We have found that the most promising is the SuperGaussian profile of index p = 2 for which the surfaces of beam shaper elements can be manufactured in the acceptable cost-effective way and beam quality does not decrease noticeably. Further, we have investigated the thermo-optic effects on the far field parameters of Gaussian and `top hat' beams to determine the influence of absorption in optical elements on beam quality degradation. The simplified formulae were derived for beam quality measures (parameter M2 and Strehl ratio) which enables to estimate the influence of absorption losses on degradation of beam quality.

Laser amplifier and method

DOEpatents

Backus, S.; Kapteyn, H.C.; Murnane, M.M.

1997-07-01

Laser amplifiers and methods for amplifying a laser beam are disclosed. A representative embodiment of the amplifier comprises first and second curved mirrors, a gain medium, a third mirror, and a mask. The gain medium is situated between the first and second curved mirrors at the focal point of each curved mirror. The first curved mirror directs and focuses a laser beam to pass through the gain medium to the second curved mirror which reflects and recollimates the laser beam. The gain medium amplifies and shapes the laser beam as the laser beam passes therethrough. The third mirror reflects the laser beam, reflected from the second curved mirror, so that the laser beam bypasses the gain medium and return to the first curved mirror, thereby completing a cycle of a ring traversed by the laser beam. The mask defines at least one beam-clipping aperture through which the laser beam passes during a cycle. The gain medium is pumped, preferably using a suitable pumping laser. The laser amplifier can be used to increase the energy of continuous-wave or, especially, pulsed laser beams including pulses of femtosecond duration and relatively high pulse rate. 7 figs.

Laser amplifier and method

DOEpatents

Backus, Sterling; Kapteyn, Henry C.; Murnane, Margaret M.

1997-01-01

Laser amplifiers and methods for amplifying a laser beam are disclosed. A representative embodiment of the amplifier comprises first and second curved mirrors, a gain medium, a third mirror, and a mask. The gain medium is situated between the first and second curved mirrors at the focal point of each curved mirror. The first curved mirror directs and focuses a laser beam to pass through the gain medium to the second curved mirror which reflects and recollimates the laser beam. The gain medium amplifies and shapes the laser beam as the laser beam passes therethough. The third mirror reflects the laser beam, reflected from the second curved mirror, so that the laser beam bypasses the gain medium and return to the first curved mirror, thereby completing a cycle of a ring traversed by the laser beam. The mask defines at least one beam-clipping aperture through which the laser beam passes during a cycle. The gain medium is pumped, preferably using a suitable pumping laser. The laser amplifier can be used to increase the energy of continuous-wave or, especially, pulsed laser beams including pulses of femtosecond duration and relatively high pulse rate.

Factorization of laser-pulse ionization probabilities in the multiphotonic regime

NASA Astrophysics Data System (ADS)

Della Picca, R.; Fiol, J.; Fainstein, P. D.

2013-09-01

We present a detailed study of the ionization probability of H and H_{2}^{+} induced by a short intense laser pulse. Starting from a Coulomb-Volkov description of the process we derive a multipole-like expansion where each term is factored into two contributions: one that accounts for the effect of the electromagnetic field on the free-electron final state and a second factor that depends only on the target structure. Such a separation may be valuable to solve complex atomic or molecular systems as well as to interpret the dynamics of the process in simpler terms. We show that the series expansion converges rapidly, and thus the inclusion of the first few terms is sufficient to produce accurate results.

Amplified spontaneous emission properties of semiconducting organic materials.

PubMed

Calzado, Eva M; Boj, Pedro G; Díaz-García, María A

2010-06-18

This paper aims to review the recent advances achieved in the field of organic solid-state lasers with respect to the usage of semiconducting organic molecules and oligomers in the form of thin films as active laser media. We mainly focus on the work performed in the last few years by our research group. The amplified spontaneous emission (ASE) properties, by optical pump, of various types of molecules doped into polystyrene films in waveguide configuration, are described. The various systems investigated include N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD), several perilenediimide derivatives (PDIs), as well as two oligo-phenylenevinylene derivatives. The ASE characteristics, i.e., threshold, emission wavelength, linewidth, and photostability are compared with that of other molecular materials investigated in the literature.

Amplified Spontaneous Emission Properties of Semiconducting Organic Materials

PubMed Central

Calzado, Eva M.; Boj, Pedro G.; Díaz-García, María A.

2010-01-01

This paper aims to review the recent advances achieved in the field of organic solid-state lasers with respect to the usage of semiconducting organic molecules and oligomers in the form of thin films as active laser media. We mainly focus on the work performed in the last few years by our research group. The amplified spontaneous emission (ASE) properties, by optical pump, of various types of molecules doped into polystyrene films in waveguide configuration, are described. The various systems investigated include N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), several perilenediimide derivatives (PDIs), as well as two oligo-phenylenevinylene derivatives. The ASE characteristics, i.e., threshold, emission wavelength, linewidth, and photostability are compared with that of other molecular materials investigated in the literature. PMID:20640167

Tracing the phase of focused broadband laser pulses

NASA Astrophysics Data System (ADS)

Hoff, Dominik; Krüger, Michael; Maisenbacher, Lothar; Sayler, A. M.; Paulus, Gerhard G.; Hommelhoff, Peter

2017-10-01

Precise knowledge of the behaviour of the phase of light in a focused beam is fundamental to understanding and controlling laser-driven processes. More than a hundred years ago, an axial phase anomaly for focused monochromatic light beams was discovered and is now commonly known as the Gouy phase. Recent theoretical work has brought into question the validity of applying this monochromatic phase formulation to the broadband pulses becoming ubiquitous today. Based on electron backscattering at sharp nanometre-scale metal tips, a method is available to measure light fields with sub-wavelength spatial resolution and sub-optical-cycle time resolution. Here we report such a direct, three-dimensional measurement of the spatial dependence of the optical phase of a focused, 4-fs, near-infrared pulsed laser beam. The observed optical phase deviates substantially from the monochromatic Gouy phase--exhibiting a much more complex spatial dependence, both along the propagation axis and in the radial direction. In our measurements, these significant deviations are the rule and not the exception for focused, broadband laser pulses. Therefore, we expect wide ramifications for all broadband laser-matter interactions, such as in high-harmonic and attosecond pulse generation, femtochemistry, ophthalmological optical coherence tomography and light-wave electronics.

Simulation of Laser Cooling and Trapping in Engineering Applications

NASA Technical Reports Server (NTRS)

Ramirez-Serrano, Jaime; Kohel, James; Thompson, Robert; Yu, Nan; Lunblad, Nathan

2005-01-01

An advanced computer code is undergoing development for numerically simulating laser cooling and trapping of large numbers of atoms. The code is expected to be useful in practical engineering applications and to contribute to understanding of the roles that light, atomic collisions, background pressure, and numbers of particles play in experiments using laser-cooled and -trapped atoms. The code is based on semiclassical theories of the forces exerted on atoms by magnetic and optical fields. Whereas computer codes developed previously for the same purpose account for only a few physical mechanisms, this code incorporates many more physical mechanisms (including atomic collisions, sub-Doppler cooling mechanisms, Stark and Zeeman energy shifts, gravitation, and evanescent-wave phenomena) that affect laser-matter interactions and the cooling of atoms to submillikelvin temperatures. Moreover, whereas the prior codes can simulate the interactions of at most a few atoms with a resonant light field, the number of atoms that can be included in a simulation by the present code is limited only by computer memory. Hence, the present code represents more nearly completely the complex physics involved when using laser-cooled and -trapped atoms in engineering applications. Another advantage that the code incorporates is the possibility to analyze the interaction between cold atoms of different atomic number. Some properties that cold atoms of different atomic species have, like cross sections and the particular excited states they can occupy when interacting with each other and light fields, play important roles not yet completely understood in the new experiments that are under way in laboratories worldwide to form ultracold molecules. Other research efforts use cold atoms as holders of quantum information, and more recent developments in cavity quantum electrodynamics also use ultracold atoms to explore and expand new information-technology ideas. These experiments give a hint on the wide range of applications and technology developments that can be tackled using cold atoms and light fields. From more precise atomic clocks and gravity sensors to the development of quantum computers, there will be a need to completely understand the whole ensemble of physical mechanisms that play a role in the development of such technologies. The code also permits the study of the dynamic and steady-state operations of technologies that use cold atoms. The physical characteristics of lasers and fields can be time-controlled to give a realistic simulation of the processes involved such that the design process can determine the best control features to use. It is expected that with the features incorporated into the code it will become a tool for the useful application of ultracold atoms in engineering applications. Currently, the software is being used for the analysis and understanding of simple experiments using cold atoms, and for the design of a modular compact source of cold atoms to be used in future research and development projects. The results so far indicate that the code is a useful design instrument that shows good agreement with experimental measurements (see figure), and a Windows-based user-friendly interface is also under development.

Erbium-doped fiber ring laser based on few-mode-singlemode-few-mode fiber structure for refractive index measurement

NASA Astrophysics Data System (ADS)

Liu, Jingxuan; Wang, Muguang; Liang, Xiao; Dong, Yue; Xiao, Han; Jian, Shuisheng

2017-08-01

A novel Erbium-doped fiber ring cavity laser sensor for refractive index (RI) measurement based on a special designed few-mode-singlemode-few-mode structure is proposed and experimentally demonstrated. The few-mode fiber is a home-made concentric ring core fiber (CRCF) which can only support two scalar modes. Thus a stable mode interference occurs which functions as a sensing head and band-pass filter to select the lasing wavelength simultaneously. A sensitivity of -45.429 nm/RIU is obtained in the range of 1.333-1.363. High optical signal to noise ratio (OSNR) of ∼45 dB and narrow 3-dB bandwidth of ∼0.1 nm indicate that the fiber ring laser sensing system has a high resolution and accuracy RI measurement.

Colloquium: Strong-field phenomena in periodic systems

NASA Astrophysics Data System (ADS)

Kruchinin, Stanislav Yu.; Krausz, Ferenc; Yakovlev, Vladislav S.

2018-04-01

The advent of visible-infrared laser pulses carrying a substantial fraction of their energy in a single field oscillation cycle has opened a new era in the experimental investigation of ultrafast processes in semiconductors and dielectrics (bulk as well as nanostructured), motivated by the quest for the ultimate frontiers of electron-based signal metrology and processing. Exploring ways to approach those frontiers requires insight into the physics underlying the interaction of strong high-frequency (optical) fields with electrons moving in periodic potentials. This Colloquium aims at providing this insight. Introduction to the foundations of strong-field phenomena defines and compares regimes of field-matter interaction in periodic systems, including (perfect) crystals as well as optical and semiconductor superlattices, followed by a review of recent experimental advances in the study of strong-field dynamics in crystals and nanostructures. Avenues toward measuring and controlling electronic processes up to petahertz frequencies are discussed.

Nd:YOV4 laser surface texturing on DLC coating: Effect on morphology, adhesion, and dry wear behavior

NASA Astrophysics Data System (ADS)

Surfaro, Maria; Giorleo, Luca; Montesano, Lorenzo; Allegri, Gabriele; Ceretti, Elisabetta; La Vecchia, Giovina Marina

2018-05-01

The surface of structural components is usually subjected to higher stresses, greater wear or fatigue damage, and more direct environmental exposure than the inner parts. For this reason, the interest to improve superficial properties of items is constantly increasing in different fields as automotive, electronic, biomedical, etc. Different approaches can be used to achieve this goal: case hardening by means of superficial heat treatments like carburizing or nitriding, deposition of thin or thick coatings, roughness modification, etc. Between the available technologies to modify components surface, Laser Surface Texturing (LST) has already been recognized in the last decade as a process, which improves the tribological properties of various parts. Based on these considerations the aim of the present research work was to realize a controlled laser texture on a Diamond-like Carbon (DLC) thin coating (about 3 µm thick) without damaging both the coating itself and the substrate. In particular, the effect of laser process parameters as marking speed and loop cycle were investigated in terms of texture features modifications. Both qualitative and quantitative analyses of the texture were executed by using a scanning electron microscope and a laser probe system to select the proper laser parameters. Moreover, the effect of the selected texture on the DLC nanohardness, adhesion and wear behavior was pointed out.

Spatially resolved and time-resolved imaging of transport of indirect excitons in high magnetic fields

NASA Astrophysics Data System (ADS)

Dorow, C. J.; Hasling, M. W.; Calman, E. V.; Butov, L. V.; Wilkes, J.; Campman, K. L.; Gossard, A. C.

2017-06-01

We present the direct measurements of magnetoexciton transport. Excitons give the opportunity to realize the high magnetic-field regime for composite bosons with magnetic fields of a few tesla. Long lifetimes of indirect excitons allow the study of kinetics of magnetoexciton transport with time-resolved optical imaging of exciton photoluminescence. We performed spatially, spectrally, and time-resolved optical imaging of transport of indirect excitons in high magnetic fields. We observed that an increasing magnetic field slows down magnetoexciton transport. The time-resolved measurements of the magnetoexciton transport distance allowed for an experimental estimation of the magnetoexciton diffusion coefficient. An enhancement of the exciton photoluminescence energy at the laser excitation spot was found to anticorrelate with the exciton transport distance. A theoretical model of indirect magnetoexciton transport is presented and is in agreement with the experimental data.

Behavioral reactions in rats exposed to low-energy laser radiation

NASA Astrophysics Data System (ADS)

Sieron, Aleksander; Mrowiec, Janina; Plech, Andrzej; Cieslar, Grzegorz; Biniszkiewicz, Tomasz

1995-03-01

The effect on their behavior of chronic exposure to infrared laser radiation applied to the skull of rats was evaluated. The experiment was carried out on 20 Wistar white male rats. A semiconductive infrared laser (wavelength -- 904 nm, frequency -- 100 Hz, pulse duration -- 10 ns, mean power 10 mW, energy density 1.5 J/cm2) was used. A skull fornix of rats was irradiated with use of multidiode probe, 10 minutes daily for 14 consecutive days. A locomotor activity was determined in the `open field' test. Simultaneously, an exploratory activity was examined in the `hole' test. Space memory was determined by means of a water maze test. Afterwards, an irritability was investigated by means of the score of Nakamura and Thoenen. The evaluation of behavior was made 24 hours after a single irradiation, at the 7th and 14th day of repeated everyday irradiation and then at the 7th and 14th day after the end of the cycle of irradiations. Obtained data show that low-energy laser radiation does not affect the rats central nervous system, resulting in persistent changes of behavior.

Compositional and Microstructural Evolution of Olivine During Pulsed Laser Irradiation: Insights Based on a FIB/Field-Emission TEM Study

NASA Technical Reports Server (NTRS)

Christoffersen, R.; Loeffler, M. J.; Dukes, C. A.; Baragiola, R. A.

2015-01-01

Introduction: The use of pulsed laser irradiation to simulate the short duration, high-energy conditions characteristic of micrometeorite impacts is now an established approach in experimental space weathering studies. The laser generates both melt and vapor deposits that contain nanophase metallic Fe (npFe(sup 0)) grains with size distributions and optical properties similar to those in natural impact-generated melt and vapor deposits. There remains uncertainty, however, about how well lasers simulate the mechanical work and internal (thermal) energy partitioning that occurs in actual impacts. We are currently engaged in making a direct comparison between the products of laser irradiation and experimental/natural hypervelocity impacts. An initial step reported here is to use analytical TEM is to attain a better understanding of how the microstructure and composition of laser deposits evolve over multiple cycles of pulsed laser irradiation. Experimental Methods: We irradiated pressed-powder pellets of San Carlos olivine (Fo(sub 90)) with up to 99 rastered pulses of a GAM ArF excimer laser. The irradiated surface of the sample were characterized by SEM imaging and areas were selected for FIB cross sectioning for TEM study using an FEI Quanta dual-beam electron/focused ion beam instrument. FIB sections were characterized using a JEOL2500SE analytical field-emission scanning transmission electron microscope (FE-STEM) optimized for quantitative element mapping at less than 10 nm spatial resolutions. Results: In the SEM the 99 pulse pressed pellet sample shows a complex, inhomogeneous, distribution of laser-generated material, largely concentrated in narrow gaps and larger depressions between grains. Local concentrations of npFe0 spherules 0.1 to 1 micrometers in size are visible within these deposits in SEM back-scatter images. Fig. 1 shows bright-field STEM images of a FIB cross-section of a one of these deposits that continuously covers the top and sloping side of an olivine grain. The deposit has 3 microstructurally distinct sub-layers composed of silicate glass with varying modal fractions and size distributions of npFe( sup 0) spherules, along with nanocrystalline silicate material. A relatively thin (50-300 nm) topmost surface layer has a high-concentration of npFe0 spherules 5-20 nm in size. Element mapping shows the layer to be enriched in Fe by a factor of 2.5 relative to the olivine substrate, with Mg and Si depleted by 20% and 10% respectively. This is compositionally complementary to the underlying, middle layer of the deposit that is depleted in Fe, enriched in Mg and has a much lower npFe0 concentration. A third layer of nanocrystalline olivine occurs at the substrate interface. Discussion: The FE-STEM results suggest the topmost layer is a vapor deposit, underlain by a thicker microstructurally complex melt-generated layer. The compositional relations suggest the melt layer was partially vaporized, preferentially losing more volatile elements (e.g., Fe). The vaporized material re-condensed to form the thin, npFe(sup 0)-rich surface deposit during or immediately after the scan cycle. Nanocrystalline olivine that grew within the melt layer as it formed and cooled is similar in volume and microstructure to what we have observed in the impact melt lining of a micrometeorite impact crater in olivine. This suggest the time-temperature relations attained in the laser sample may not be too different from a micrometeorite impact. Our TEM observations, however, do not show evidence for the same level of mechanical dam-age (e.g., fracturing) seen around the natural micrometeorite crater.

WIND MEASUREMENTS WITH HIGH-ENERGY DOPPLER LIDAR

NASA Technical Reports Server (NTRS)

Koch, Grady J.; Kavaya, Michael J.; Barnes, Bruce W.; Beyon, Jeffrey Y.; Petros, Mulugeta; Jirong, Yu; Amzajerdian, Farzin; Slingh, Upendra N.

2006-01-01

Coherent lidars at 2-micron wavelengths from holmium or thulium solid-state lasers have been in use to measure wind for applications in meteorology, aircraft wake vortex tracking, and turbulence detection [1,2,3] These field-deployed lidars, however, have generally been of a pulse energy of a few millijoules, limiting their range capability or restricting operation to regions of high aerosol concentration such as the atmospheric boundary layer. Technology improvements in the form of high-energy pulsed lasers, low noise detectors, and high optical quality telescopes are being evaluated to make wind measurements to long ranges or low aerosol concentrations. This research is aimed at developing lidar technology for satellite-based observation of wind on a global scale. The VALIDAR project was initiated to demonstrate a high pulse energy coherent Doppler lidar. VALIDAR gets its name from the concept of validation lidar, in that it can serve as a calibration and validation source for future airborne and spaceborne lidar missions. VALIDAR is housed within a mobile trailer for field measurements.

Routes to formation of highly excited neutral atoms in the break-up of strongly driven hydrogen molecule

NASA Astrophysics Data System (ADS)

Emmanouilidou, Agapi

2012-06-01

We present a theoretical quasiclassical treatment of the formation, during Coulomb explosion, of highly excited neutral H atoms for strongly-driven hydrogen molecule. This process, where after the laser field is turned off, one electron escapes to the continuum while the other occupies a Rydberg state, was recently reported in an experimental study in Phys. Rev. Lett 102, 113002 (2009). We find that two-electron effects are important in order to correctly account for all pathways leading to highly excited neutral hydrogen formation [1]. We identify two pathways where the electron that escapes to the continuum does so either very quickly or after remaining bound for a few periods of the laser field. These two pathways of highly excited neutral H formation have distinct traces in the probability distribution of the escaping electron momentum components. [4pt] [1] A. Emmanouilidou, C. Lazarou, A. Staudte and U. Eichmann, Phys. Rev. A (Rapid) 85 011402 (2012).

Real-time turbulence profiling with a pair of laser guide star Shack-Hartmann wavefront sensors for wide-field adaptive optics systems on large to extremely large telescopes.

PubMed

Gilles, L; Ellerbroek, B L

2010-11-01

Real-time turbulence profiling is necessary to tune tomographic wavefront reconstruction algorithms for wide-field adaptive optics (AO) systems on large to extremely large telescopes, and to perform a variety of image post-processing tasks involving point-spread function reconstruction. This paper describes a computationally efficient and accurate numerical technique inspired by the slope detection and ranging (SLODAR) method to perform this task in real time from properly selected Shack-Hartmann wavefront sensor measurements accumulated over a few hundred frames from a pair of laser guide stars, thus eliminating the need for an additional instrument. The algorithm is introduced, followed by a theoretical influence function analysis illustrating its impulse response to high-resolution turbulence profiles. Finally, its performance is assessed in the context of the Thirty Meter Telescope multi-conjugate adaptive optics system via end-to-end wave optics Monte Carlo simulations.

Field propagation-induced directionality of carrier-envelope phase-controlled photoemission from nanospheres

DOE PAGES

SuBmann, F.; Seiffert, L.; Zherebtsov, S.; ...

2015-08-12

Near-fields of non-resonantly laser-excited nanostructures enable strong localization of ultrashort light fields and have opened novel routes to fundamentally modify and control electronic strong-field processes. Harnessing spatiotemporally tunable near-fields for the steering of sub-cycle electron dynamics may enable ultrafast optoelectronic devices and unprecedented control in the generation of attosecond electron and photon pulses. Here we utilize unsupported sub-wavelength dielectric nanospheres to generate near-fields with adjustable structure and study the resulting strong-field dynamics via photoelectron imaging. We demonstrate field propagation-induced tunability of the emission direction of fast recollision electrons up to a regime, where nonlinear charge interaction effects become dominant inmore » the acceleration process. In conclusion, our analysis supports that the timing of the recollision process remains controllable with attosecond resolution by the carrier-envelope phase, indicating the possibility to expand near-field-mediated control far into the realm of high-field phenomena.« less

Field propagation-induced directionality of carrier-envelope phase-controlled photoemission from nanospheres

DOE Office of Scientific and Technical Information (OSTI.GOV)

SuBmann, F.; Seiffert, L.; Zherebtsov, S.

Near-fields of non-resonantly laser-excited nanostructures enable strong localization of ultrashort light fields and have opened novel routes to fundamentally modify and control electronic strong-field processes. Harnessing spatiotemporally tunable near-fields for the steering of sub-cycle electron dynamics may enable ultrafast optoelectronic devices and unprecedented control in the generation of attosecond electron and photon pulses. Here we utilize unsupported sub-wavelength dielectric nanospheres to generate near-fields with adjustable structure and study the resulting strong-field dynamics via photoelectron imaging. We demonstrate field propagation-induced tunability of the emission direction of fast recollision electrons up to a regime, where nonlinear charge interaction effects become dominant inmore » the acceleration process. In conclusion, our analysis supports that the timing of the recollision process remains controllable with attosecond resolution by the carrier-envelope phase, indicating the possibility to expand near-field-mediated control far into the realm of high-field phenomena.« less

Irreversible transformation of ferromagnetic ordered stripe domains in single-shot infrared-pump/resonant-x-ray-scattering-probe experiments

NASA Astrophysics Data System (ADS)

Bergeard, Nicolas; Schaffert, Stefan; López-Flores, Víctor; Jaouen, Nicolas; Geilhufe, Jan; Günther, Christian M.; Schneider, Michael; Graves, Catherine; Wang, Tianhan; Wu, Benny; Scherz, Andreas; Baumier, Cédric; Delaunay, Renaud; Fortuna, Franck; Tortarolo, Marina; Tudu, Bharati; Krupin, Oleg; Minitti, Michael P.; Robinson, Joe; Schlotter, William F.; Turner, Joshua J.; Lüning, Jan; Eisebitt, Stefan; Boeglin, Christine

2015-02-01

The evolution of a magnetic domain structure upon excitation by an intense, femtosecond infrared (IR) laser pulse has been investigated using single-shot based time-resolved resonant x-ray scattering at the x-ray free electron laser LCLS. A well-ordered stripe domain pattern as present in a thin CoPd alloy film has been used as a prototype magnetic domain structure for this study. The fluence of the IR laser pump pulse was sufficient to lead to an almost complete quenching of the magnetization within the ultrafast demagnetization process taking place within the first few hundreds of femtoseconds following the IR laser pump pulse excitation. On longer time scales this excitation gave rise to subsequent irreversible transformations of the magnetic domain structure. Under our specific experimental conditions, it took about 2 ns before the magnetization started to recover. After about 5 ns the previously ordered stripe domain structure had evolved into a disordered labyrinth domain structure. Surprisingly, we observe after about 7 ns the occurrence of a partially ordered stripe domain structure reoriented into a novel direction. It is this domain structure in which the sample's magnetization stabilizes as revealed by scattering patterns recorded long after the initial pump-probe cycle. Using micromagnetic simulations we can explain this observation based on changes of the magnetic anisotropy going along with heat dissipation in the film.

In situ temperature measurements with thermocouple probes during laser interstitial thermotherapy (LITT): quantification and correction of a measurement artifact.

PubMed

Manns, F; Milne, P J; Gonzalez-Cirre, X; Denham, D B; Parel, J M; Robinson, D S

1998-01-01

The purpose of this work was to quantify the magnitude of an artifact induced by stainless steel thermocouple probes in temperature measurements made in situ during experimental laser interstitial thermo-therapy (LITT). A procedure for correction of this observational error is outlined. A CW Nd:YAG laser system emitting 20W for 25-30 s delivered through a fiber-optic probe was used to create localized heating. The temperature field around the fiber-optic probe during laser irradiation was measured every 0.3 s in air, water, 0.4% intralipid solution, and fatty cadaver pig tissue, with a field of up to fifteen needle thermocouple probes. Direct absorption of Nd:YAG laser radiation by the thermocouple probes induced an overestimation of the temperature, ranging from 1.8 degrees C to 118.6 degrees C in air, 2.2 degrees C to 9.9 degrees C in water, 0.7 C to 4.7 C in intralipid and 0.3 C to 17.9 C in porcine tissue after irradiation at 20W for 30 s and depending on the thermocouple location. The artifact in porcine tissue was removed by applying exponential and linear fits to the measured temperature curves. Light absorption by thermocouple probes can induce a significant artifact in the measurement of laser-induced temperature increases. When the time constant of the thermocouple effect is much smaller than the thermal relaxation time of the surrounding tissue, the artifact can be accurately quantified. During LITT experiments where temperature differences of a few degrees are significant, the thermocouple artifact must be removed in order to be able accurately to predict the treatment outcome.

Closed cycle electric discharge laser design investigation

NASA Technical Reports Server (NTRS)

Baily, P. K.; Smith, R. C.

1978-01-01

Closed cycle CO2 and CO electric discharge lasers were studied. An analytical investigation assessed scale-up parameters and design features for CO2, closed cycle, continuous wave, unstable resonator, electric discharge lasing systems operating in space and airborne environments. A space based CO system was also examined. The program objectives were the conceptual designs of six CO2 systems and one CO system. Three airborne CO2 designs, with one, five, and ten megawatt outputs, were produced. These designs were based upon five minute run times. Three space based CO2 designs, with the same output levels, were also produced, but based upon one year run times. In addition, a conceptual design for a one megawatt space based CO laser system was also produced. These designs include the flow loop, compressor, and heat exchanger, as well as the laser cavity itself. The designs resulted in a laser loop weight for the space based five megawatt system that is within the space shuttle capacity. For the one megawatt systems, the estimated weight of the entire system including laser loop, solar power generator, and heat radiator is less than the shuttle capacity.

A Comparative Study of Cycle Variability of Laser Plug Ignition vs Classical Spark Plug Ignition in Combustion Engines

NASA Astrophysics Data System (ADS)

Done, Bogdan

2017-10-01

Over the past 30 years numerous studies and laboratory experiments have researched the use of laser energy to ignite gas and fuel-air mixtures. The actual implementation of this laser application has still to be fully achieved in a commercial automotive application. Laser Plug Ignition as a replacement for Spark Plug Ignition in the internal combustion engines of automotive vehicles, offers several potential benefits such as extending lean burn capability, reducing the cyclic variability between combustion cycles and decreasing the total amount of ignition costs, and implicitly weight and energy requirements. The paper presents preliminary results of cycle variability study carried on a SI Engine equipped with laser Plug Ignition system. Versus classic ignition system, the use of the laser Plug Ignition system assures the reduction of the combustion process variability, reflected in the lower values of the coefficient of variability evaluated for indicated mean effective pressure, maximum pressure, maximum pressure angle and maximum pressure rise rate. The laser plug ignition system was mounted on an experimental spark ignition engine and tested at the regime of 90% load and 2800 rev/min, at dosage of λ=1.1. Compared to conventional spark plug, laser ignition assures the efficiency at lean dosage.

A compact, efficient, and lightweight laser head for CARLO®: integration, performance, and benefits

NASA Astrophysics Data System (ADS)

Deibel, Waldemar; Schneider, Adrian; Augello, Marcello; Bruno, Alfredo E.; Juergens, Philipp; Cattin, Philippe

2015-09-01

Ever since the first functional lasers were built about 50 years ago, researchers and doctors dream of a medical use for such systems. Today's technology is finally advanced enough to realize these ambitions in a variety of medical fields. There are well-established laser based systems in ophthalmology, dental applications, treatment of kidney stones, and many more. Using lasers presents more than just an alternative to conventional methods for osteotomies. It offers less tissue damage, faster healing times, comparable intervention duration and in consequence improves postoperative treatment of patients. However, there are a few factors that limit routine applications. These technical drawbacks include missing depth control and safe guiding of the laser beam. This paper presents the engineering and integration of a miniaturized laser head for a computer assisted and robot-guided laser osteotome (CARLO®), which can overcome the mentioned drawbacks. The CARLO® device ensures a safe and precise guidance of the laser beam. Such guidance also enables new opportunities and methods, e.g. free geometrical functional cuts, which have the potential to revolutionize bone surgery. The laser head is optimized for beam shaping, target conditioning, working distance, compactness and the integration of all other parts needed, e.g. CCD-cameras for monitoring and referencing, a visible laser for cut simulation, etc. The beam coming out of the laser system is conditioned in shape, energy properties and working distance with an optical arrangement to achieve the desired cutting performance. Here also parameters like optical losses, operating mode, optics materials and long-term stability have are taken into account.

Superelastic Few-Layer Carbon Foam Made from Natural Cotton for All-Solid-State Electrochemical Capacitors.

PubMed

Lin, Tianquan; Liu, Fengxin; Xu, Feng; Bi, Hui; Du, Yahui; Tang, Yufeng; Huang, Fuqiang

2015-11-18

Flexible/stretchable devices for energy storage are essential for future wearable and flexible electronics. Electrochemical capacitors (ECs) are an important technology for supplement batteries in the energy storage and harvesting field, but they are limited by relatively low energy density. Herein, we report a superelastic foam consisting of few-layer carbon nanowalls made from natural cotton as a good scaffold to growth conductive polymer polyaniline for stretchable, lightweight, and flexible all-solid-state ECs. As-prepared superelastic bulk tubular carbon foam (surface area ∼950 m(2)/g) can withstand >90% repeated compression cycling and support >45,000 times its own weight but no damage. The flexible device has a high specific capacitance of 510 F g(-1), a specific energy of 25.5 Wh kg(-1) and a power density of 28.5 kW kg(-1) in weight of the total electrode materials and withstands 5,000 charging/discharging cycles.

The effect of advanced ultrasonic forging on fatigue fracture mechanisms of welded Ti-6A1-4V alloy

NASA Astrophysics Data System (ADS)

Smirnova, A.; Pochivalov, Yu.; Panin, V.; Panin, S.; Eremin, A.; Gorbunov, A.

2017-12-01

The current study is devoted to application of advanced postwelding ultrasonic forging to joints formed by laser welding of Ti-6A1-4V alloy in order to enhance their mechanical properties and fatigue durability. Low cycle fatigue tests were performed via digital image correlation technique used to obtain strain fields and in situ characterization of deformation, crack growth and fracture. Fracture surfaces were studied by SEM analysis accompanied with calculation of fracture patterns percentage. The fatigue tests demonstrate the high increase in the number of cycles until fracture (from 17 000 to 32 000 cycles) which could be explained by high ductility of welded material after treatment. This leads to lower fatigue crack growth rate due to higher energy dissipation. The obtained effect is attributable only for small cracks on micro-/mesoscales and fails to play a significant role for macro cracks.

Exploring the effects of low-level laser therapy on fibroblasts and tumor cells following gamma radiation exposure.

PubMed

Ramos Silva, Camila; Cabral, Fernanda Viana; de Camargo, Claudinei Francisco Morais; Núñez, Silvia Cristina; Mateus Yoshimura, Tania; de Lima Luna, Arthur Cássio; Maria, Durvanei Augusto; Ribeiro, Martha Simões

2016-12-01

Ionizing radiation (IR) induces DNA damage and low-level laser therapy (LLLT) has been investigated to prevent or repair detrimental outcomes resulting from IR exposure. Few in vitro studies, however, explore the biological mechanisms underlying those LLLT benefits. Thus, in this work, fibroblasts and tumor cells are submitted to IR with doses of 2.5 Gy and 10 Gy. After twenty-four-h, the cells are exposed to LLLT with fluences of 30 J cm -2 , 90 J cm -2 , and 150 J cm -2 . Cellular viability, cell cycle phases, cell proliferation index and senescence are evaluated on days 1 and 4 after LLLT irradiation. For fibroblasts, LLLT promotes - in a fluence-dependent manner - increments in cell viability and proliferation, while a reduction in the senescence was observed. Regarding tumor cells, no influences of LLLT on cell viability are noticed. Whereas LLLT enhances cell populations in S and G 2 /M cell cycle phases for both cellular lines, a decrease in proliferation and increase in senescence was verified only for tumor cells. Putting together, the results suggest that fibroblasts and tumor cells present different responses to LLLT following exposure to gamma-radiation, and these promising results should stimulate further investigations. Senescence of tumor cells and fibroblasts on the 4 th day after ionizing radiation (IR) and low-level laser therapy (LLLT) exposures. The number of senescent cells increased significantly for tumor cells (a) while for fibroblasts no increment was observed (b). The blue collor indicates senescence activity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Constraining stellar binary black hole formation scenarios with eLISA eccentricity measurements

NASA Astrophysics Data System (ADS)

Nishizawa, Atsushi; Sesana, Alberto; Berti, Emanuele; Klein, Antoine

2017-03-01

A space-based interferometer such as the evolved Laser Interferometer Space Antenna (eLISA) could observe a few to a few thousands of progenitors of black hole binaries (BHBs) similar to those recently detected by Advanced LIGO. Gravitational radiation circularizes the orbit during inspiral, but some BHBs retain a measurable eccentricity at the low frequencies where eLISA is the most sensitive. The eccentricity of a BHB carries precious information about its formation channel: BHBs formed in the field, in globular clusters, or close to a massive black hole (MBH) have distinct eccentricity distributions in the eLISA band. We generate mock eLISA observations, folding in measurement errors, and using a Bayesian model selection, we study whether eLISA measurements can identify the BHB formation channel. We find that a handful of observations would suffice to tell whether BHBs were formed in the gravitational field of an MBH. Conversely, several tens of observations are needed to tell apart field formation from globular cluster formation. A 5-yr eLISA mission with the longest possible armlength is desirable to shed light on BHB formation scenarios.

Laser space debris removal: now, not later

NASA Astrophysics Data System (ADS)

Phipps, Claude R.

2015-02-01

Small (1-10cm) debris in low Earth orbit (LEO) are extremely dangerous, because they spread the breakup cascade depicted in the movie "Gravity." Laser-Debris-Removal (LDR) is the only solution that can address both large and small debris. In this paper, we briefly review ground-based LDR, and discuss how a polar location can dramatically increase its effectiveness for the important class of sun-synchronous orbit (SSO) objects. No other solutions address the whole problem of large ( 1000cm, 1 ton) as well as small debris. Physical removal of small debris (by nets, tethers and so on) is impractical because of the energy cost of matching orbits. We also discuss a new proposal which uses a space-based station in low Earth orbit (LEO), and rapid, head-on interaction in 10- 40s rather than 4 minutes, with high-power bursts of 100ps, 355nm pulses from a 1.5m diameter aperture. The orbiting station employs "heat-capacity" laser mode with low duty cycle to create an adaptable, robust, dualmode system which can lower or raise large derelict objects into less dangerous orbits, as well as clear out the small debris in a 400-km thick LEO band. Time-average laser optical power is less than 15kW. The combination of short pulses and UV wavelength gives lower required energy density (fluence) on target as well as higher momentum coupling coefficient. This combination leads to much smaller mirrors and lower average power than the ground-based systems we have considered previously. Our system also permits strong defense of specific assets. Analysis gives an estimated cost of about 1k each to re-enter most small debris in a few months, and about 280k each to raise or lower 1-ton objects by 40km. We believe it can do this for 2,000 such large objects in about four years. Laser ablation is one of the few interactions in nature that propel a distant object without any significant reaction on the source.

Single-cycle high-intensity electromagnetic pulse generation in the interaction of a plasma wakefield with regular nonlinear structures.

PubMed

Bulanov, S S; Esirkepov, T Zh; Kamenets, F F; Pegoraro, F

2006-03-01

The interaction of regular nonlinear structures (such as subcycle solitons, electron vortices, and wake Langmuir waves) with a strong wake wave in a collisionless plasma can be exploited in order to produce ultrashort electromagnetic pulses. The electromagnetic field of the nonlinear structure is partially reflected by the electron density modulations of the incident wake wave and a single-cycle high-intensity electromagnetic pulse is formed. Due to the Doppler effect the length of this pulse is much shorter than that of the nonlinear structure. This process is illustrated with two-dimensional particle-in-cell simulations. The considered laser-plasma interaction regimes can be achieved in present day experiments and can be used for plasma diagnostics.

Ultrafast control of strong light-matter coupling

NASA Astrophysics Data System (ADS)

Lange, Christoph; Cancellieri, Emiliano; Panna, Dmitry; Whittaker, David M.; Steger, Mark; Snoke, David W.; Pfeiffer, Loren N.; West, Kenneth W.; Hayat, Alex

2018-01-01

We dynamically modulate strong light-matter coupling in a GaAs/AlGaAs microcavity using intense ultrashort laser pulses tuned below the interband exciton energy, which induce a transient Stark shift of the cavity polaritons. For 225-fs pulses, shorter than the cavity Rabi cycle period of 1000 fs, this shift decouples excitons and cavity photons for the duration of the pulse, interrupting the periodic energy exchange between photonic and electronic states. For 1500-fs pulses, longer than the Rabi cycle period, however, the Stark shift does not affect the strong coupling. The two regimes are marked by distinctly different line shapes in ultrafast reflectivity measurements—regardless of the Stark field intensity. The crossover marks the transition from adiabatic to diabatic switching of strong light-matter coupling.

Measurements and Studies of Secondary Electron Emission of Diamond Amplified Photocathode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu,Q.

2008-10-01

The Diamond Amplified Photocathode (DAP) is a novel approach to generating electrons. By following the primary electron beam, which is generated by traditional electron sources, with an amplifier, the electron beam available to the eventual application is increased by 1 to 2 orders of magnitude in current. Diamond has a very wide band gap of 5.47eV which allows for a good negative electron affinity with simple hydrogenation, diamond can hold more than 2000MV/m field before breakdown. Diamond also provides the best rigidity among all materials. These two characters offer the capability of applying high voltage across very thin diamond filmmore » to achieve high SEY and desired emission phase. The diamond amplifier also is capable of handling a large heat load by conduction and sub-nanosecond pulse input. The preparation of the diamond amplifier includes thinning and polishing, cleaning with acid etching, metallization, and hydrogenation. The best mechanical polishing available can provide high purity single crystal diamond films with no less than 100 {micro}m thickness and <15 nm Ra surface roughness. The ideal thickness for 700MHz beam is {approx}30 {micro}m, which requires further thinning with RIE or laser ablation. RIE can achieve atomic layer removal precision and roughness eventually, but the time consumption for this procedure is very significant. Laser ablation proved that with <266nm ps laser beam, the ablation process on the diamond can easily achieve removing a few microns per hour from the surface and <100nm roughness. For amplifier application, laser ablation is an adequate and efficient process to make ultra thin diamond wafers following mechanical polishing. Hydrogenation will terminate the diamond surface with monolayer of hydrogen, and form NEA so that secondary electrons in the conduction band can escape into the vacuum. The method is using hydrogen cracker to strike hydrogen atoms onto the bare diamond surface to form H-C bonds. Two independent experiments were carried out to determine the transport of the electrons within the diamond and their emission at the surface. In transmission mode measurements, the diamond amplifier was coated with metal on both sides, so results simply depend only on the electron transport within the diamond. The SEY for this mode provides one secondary electron per 20eV energy, which gives the gain of more than 200 for 4.7keV (effective energy) primary electrons under 2MV/m. Laser detrapping can help the signal maintain the gain with lops pulse and duty cycle of 1.67 x 10{sup -7}. In emission mode measurements, in which the diamond is prepared as in the actual application, the SEY is {approx}20 for 700eV (effective energy) primary electrons under 1.21MV/m. The electric field applied and the primary electron energy is limited by the experiment setup, but the results show good trend toward large gain under high field. Thermal emittance of the diamond secondary emission is critical for the beam application. A careful design is setup to measure with very fine precision and accuracy of 0.01eV.« less