Coherent Enhancement of 10 s Burst-Mode Ultraviolet Pulses at Megawatt Peak Power

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

Abudureyimu, Reheman; Liu, Yun

2017-01-01

A doubly-resonant optical cavity and its locking technique have been developed to achieve coherent enhancement of 402.5-MHz, 50-ps, megawatt peak power ultraviolet (355 nm) laser pulses operating at a 10- s/10-Hz burst mode.

Enhancement of EUV emission from a liquid microjet target by use of dual laser pulses

NASA Astrophysics Data System (ADS)

Higashiguchi, Takeshi; Rajyaguru, Chirag; Koga, Masato; Kawasaki, Keita; Sasaki, Wataru; Kubodera, Shoichi; Kikuchi, Takashi; Yugami, Noboru; Kawata, Shigeo; Andreev, Alexander A.

2005-03-01

Extreme ultraviolet (EUV) radiation at the wavelength of around 13nm waws observed from a laser-produced plasma using continuous water-jet. Strong dependence of the conversion efficiency (CE) on the laser focal spot size and jet diameter was observed. The EUV CE at a given laser spot size and jet diameter was further enhanced using double laser pulses, where a pre-pulse was used for initial heating of the plasma.

Multistep Ionization of Argon Clusters in Intense Femtosecond Extreme Ultraviolet Pulses

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

Bostedt, C.; Thomas, H.; Hoener, M.

The interaction of intense extreme ultraviolet femtosecond laser pulses ({lambda}=32.8 nm) from the FLASH free electron laser (FEL) with clusters has been investigated by means of photoelectron spectroscopy and modeled by Monte Carlo simulations. For laser intensities up to 5x10{sup 13} W/cm{sup 2}, we find that the cluster ionization process is a sequence of direct electron emission events in a developing Coulomb field. A nanoplasma is formed only at the highest investigated power densities where ionization is frustrated due to the deep cluster potential. In contrast with earlier studies in the IR and vacuum ultraviolet spectral regime, we find nomore » evidence for electron emission from plasma heating processes.« less

Development of ultraviolet lasers

NASA Technical Reports Server (NTRS)

Walters, G. K.

1974-01-01

The pulsed electron accelerator selected for use in the development of ultraviolet laser capability suitable for use in photoexcitation and photoionization studies of the upper atmosphere is reported. Performance figures, installation specifications, and total cost of the equipment are briefly shown, and plans for further studies are outlined.

Ultrafast, high repetition rate, ultraviolet, fiber-laser-based source: application towards Yb⁺ fast quantum-logic.

PubMed

Hussain, Mahmood Irtiza; Petrasiunas, Matthew Joseph; Bentley, Christopher D B; Taylor, Richard L; Carvalho, André R R; Hope, Joseph J; Streed, Erik W; Lobino, Mirko; Kielpinski, David

2016-07-25

Trapped ions are one of the most promising approaches for the realization of a universal quantum computer. Faster quantum logic gates could dramatically improve the performance of trapped-ion quantum computers, and require the development of suitable high repetition rate pulsed lasers. Here we report on a robust frequency upconverted fiber laser based source, able to deliver 2.5 ps ultraviolet (UV) pulses at a stabilized repetition rate of 300.00000 MHz with an average power of 190 mW. The laser wavelength is resonant with the strong transition in Ytterbium (Yb⁺) at 369.53 nm and its repetition rate can be scaled up using high harmonic mode locking. We show that our source can produce arbitrary pulse patterns using a programmable pulse pattern generator and fast modulating components. Finally, simulations demonstrate that our laser is capable of performing resonant, temperature-insensitive, two-qubit quantum logic gates on trapped Yb⁺ ions faster than the trap period and with fidelity above 99%.

300-mW narrow-linewidth deep-ultraviolet light generation at 193 nm by frequency mixing between Yb-hybrid and Er-fiber lasers.

PubMed

Xuan, Hongwen; Zhao, Zhigang; Igarashi, Hironori; Ito, Shinji; Kakizaki, Kouji; Kobayashi, Yohei

2015-04-20

A narrow-linewidth, high average power deep-ultraviolet (DUV) coherent laser emitting at 193 nm is demonstrated by frequency mixing a Yb-hybrid laser with an Er-fiber laser. The Yb-hybrid laser consists of Yb-fiber lasers and an Yb:YAG amplifier. The average output power of the 193 nm laser is 310 mW at 6 kHz, which corresponds to a pulse energy of 51 μJ. To the best of our knowledge, this is the highest average power and pulse energy ever reported for a narrow-linewidth 193 nm light generated by a combination of solid-state and fiber lasers with frequency mixing. We believe this laser will be beneficial for the application of interference lithography by seeding an injection-locking ArF eximer laser.

X-Ray Laser Program Final Report for FY92

DTIC Science & Technology

1993-07-01

also produced population inversion. Ultra- intense , femtosecond- pulsed laboratory lasers ranging from the ultraviolet to the infrared represent an...with pulse lengths of 650 femtoseconds normally Incident on a 2p. thick planar aluminum slab. Comparisons are made for two laser Intensities , two...prepulse is subsequently irradiated by the main high intensity pulse . The persistence of the heliumlike ground state raises the possibility that a photon

Optical effects of exposing intact human lenses to ultraviolet radiation and visible light.

PubMed

Kessel, Line; Eskildsen, Lars; Lundeman, Jesper Holm; Jensen, Ole Bjarlin; Larsen, Michael

2011-12-30

The human lens is continuously exposed to high levels of light. Ultraviolet radiation is believed to play a causative role in the development of cataract. In vivo, however, the lens is mainly exposed to visible light and the ageing lens absorbs a great part of the short wavelength region of incoming visible light. The aim of the present study was to examine the optical effects on human lenses of short wavelength visible light and ultraviolet radiation. Naturally aged human donor lenses were irradiated with UVA (355 nm), violet (400 and 405 nm) and green (532 nm) lasers. The effect of irradiation was evaluated qualitatively by photography and quantitatively by measuring the direct transmission before and after irradiation. Furthermore, the effect of pulsed and continuous laser systems was compared as was the effect of short, intermediate and prolonged exposures. Irradiation with high intensity lasers caused scattering lesions in the human lenses. These effects were more likely to be seen when using pulsed lasers because of the high pulse intensity. Prolonged irradiation with UVA led to photodarkening whereas no detrimental effects were observed after irradiation with visible light. Irradiation with visible light does not seem to be harmful to the human lens except if the lens is exposed to laser irradiances that are high enough to warrant thermal protein denaturation that is more readily seen using pulsed laser systems.

Ultraviolet Raman scattering from persistent chemical warfare agents

NASA Astrophysics Data System (ADS)

Kullander, Fredrik; Wästerby, Pär.; Landström, Lars

2016-05-01

Laser induced Raman scattering at excitation wavelengths in the middle ultraviolet was examined using a pulsed tunable laser based spectrometer system. Droplets of chemical warfare agents, with a volume of 2 μl, were placed on a silicon surface and irradiated with sequences of laser pulses. The Raman scattering from V-series nerve agents, Tabun (GA) and Mustard gas (HD) was studied with the aim of finding the optimum parameters and the requirements for a detection system. A particular emphasis was put on V-agents that have been previously shown to yield relatively weak Raman scattering in this excitation band.

Simple Ultraviolet Short-Pulse Intensity Diagnostic Method Using Atmosphere

NASA Astrophysics Data System (ADS)

Aota, Tatsuya; Takahashi, Eiichi; Losev, Leonid L.; Tabuchi, Takeyuki; Kato, Susumu; Matsumoto, Yuji; Okuda, Isao; Owadano, Yoshiro

2005-05-01

An ultraviolet (UV) short-pulse intensity diagnostic method using atmosphere as a nonlinear medium was developed. This diagnostic method is based on evaluating the ion charge of the two-photon ionization of atmospheric oxygen upon irradiation with a UV (238-299 nm) short-pulse laser. The observed ion signal increased proportionally to the input intensity to the power of ˜2.2, during the two-photon ionization of atmospheric oxygen. An autocorrelator was constructed and used to successfully measure a UV laser pulse of ˜400 fs duration. Since this diagnostic system is used in the open-air under windowless conditions, it can be set along the beam path and used as a UV intensity monitor.

Multifunctional optical correlator for picosecond ultraviolet laser pulse measurement

DOE PAGES

Rakhman, Abdurahim; Wang, Yang; Garcia, Frances; ...

2014-01-01

A compact optical correlator system that measures both the autocorrelation between two infrared (IR) lights and the cross-correlation between an IR and an ultraviolet (UV) light using a single nonlinear optical crystal has been designed and experimentally demonstrated. The rapid scanning of optical delay line, switching between auto and cross-correlations, crystal angle tuning, and data acquisition and processing are all computer controlled. Pulse widths of an IR light from a mode-locked laser are measured by the correlator and the results are compared with a direct measurement using a high-speed photodetector system. The correlator has been used to study the parametermore » dependence of the pulse width of a macropulse UV laser designed for laser-assisted hydrogen ion (H-) beam stripping for the Spallation Neutron Source at Oak Ridge National Laboratory.« less

Electronic gating circuit and ultraviolet laser excitation permit improved dosimeter sensitivity

NASA Technical Reports Server (NTRS)

Eggenberger, D.; King, D.; Longnecker, A.; Schutt, D.

1968-01-01

Standard dosimeter reader, modified by adding an electronic gating circuit to trigger the intensity level photomultiplier, increases readout sensitivity of photoluminescent dosimeter systems. The gating circuit is controlled by a second photomultiplier which senses a short ultraviolet pulse from a laser used to excite the dosimeter.

Laser-Bioplasma Interaction: Excitation and Suppression of the Brain Waves by the Multi-photon Pulsed-operated Fiber Lasers in the Ultraviolet Range of Frequencies

NASA Astrophysics Data System (ADS)

Stefan, V. Alexander; IAPS-team Team

2017-10-01

The novel study of the laser excitation-suppression of the brain waves is proposed. It is based on the pulsed-operated multi-photon fiber-laser interaction with the brain parvalbumin (PV) neurons. The repetition frequency matches the low frequency brain waves (5-100 Hz); enabling the resonance-scanning of the wide range of the PV neurons (the generators of the brain wave activity). The tunable fiber laser frequencies are in the ultraviolet frequency range, thus enabling the monitoring of the PV neuron-DNA, within the 10s of milliseconds. In medicine, the method can be used as an ``instantaneous-on-off anesthetic.'' Supported by Nikola Tesla Labs, Stefan University.

Femtosecond-pulse-driven electron-excited extreme-ultraviolet lasers in Be-like ions.

PubMed

Hooker, S M; Harris, S E

1995-10-01

A suggestion for the generation of extreme-ultraviolet (XUV) laser radiation based on tunneling ionization and subsequent electron excitation of Deltan not equal 0 transitions is described. The favorable scaling of the required intensity of the pump laser with the output XUV wavelength is compared with that exhibited by XUV lasers ased on Deltan = 0 transitions. Calculations for Be-like Ne predict signif icant gain at 14.1 nm.

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.

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.

Physics of the Brain. Prevention of the Epileptic Seizures by the Multi-photon Pulsed-operated Fiber Lasers in the Ultraviolet Range of Frequencies.

NASA Astrophysics Data System (ADS)

Stefan, V. Alexander; IAPS Team

The novel study of the epileptogenesis mechanisms is proposed. It is based on the pulsed-operated (amplitude modulation) multi-photon (frequency modulation) fiber-laser interaction with the brain epilepsy-topion (the epilepsy onset area), so as to prevent the excessive electrical discharge (epileptic seizure) in the brain. The repetition frequency, Ω, matches the low frequency (epileptic) phonon waves in the brain. The laser repetition frequency (5-100 pulses per second) enables the resonance-scanning of the wide range of the phonon (possible epileptic-to-be) activity in the brain. The tunable fiber laser frequencies, Δω (multi photon operation), are in the ultraviolet frequency range, thus enabling monitoring of the electrical charge imbalance (within the 10s of milliseconds), and the DNA-corruption in the epilepsy-topion, as the possible cause of the disease. Supported by Nikola Tesla Labs., Stefan University.

CO2 laser drives extreme ultraviolet nano-lithography — second life of mature laser technology

NASA Astrophysics Data System (ADS)

Nowak, K. M.; Ohta, T.; Suganuma, T.; Fujimoto, J.; Mizoguchi, H.; Sumitani, A.; Endo, A.

2013-12-01

It was shown both theoretically and experimentally that nanosecond order laser pulses at 10.6 micron wavelength were superior for driving the Sn plasma extreme ultraviolet (EUV) source for nano-lithography for the reasons of higher conversion efficiency, lower production of debris and higher average power levels obtainable in CO2 media without serious problems of beam distortions and nonlinear effects occurring in competing solid-state lasers at high intensities. The renewed interest in such pulse format, wavelength, repetition rates in excess of 50 kHz and average power levels in excess of 18 kiloWatt has sparked new opportunities for a matured multi-kiloWatt CO2 laser technology. The power demand of EUV source could be only satisfied by a Master-Oscillator-Power-Amplifier system configuration, leading to a development of a new type of hybrid pulsed CO2 laser employing a whole spectrum of CO2 technology, such as fast flow systems and diffusion-cooled planar waveguide lasers, and relatively recent quantum cascade lasers. In this paper we review briefly the history of relevant pulsed CO2 laser technology and the requirements for multi-kiloWatt CO2 laser, intended for the laser-produced plasma EUV source, and present our recent advances, such as novel solid-state seeded master oscillator and efficient multi-pass amplifiers built on planar waveguide CO2 lasers.

Excimer Lasers In Medicine

NASA Astrophysics Data System (ADS)

Tittel, Frank K.; Saidi, Iyad S.; Pettit, George H.; Wisoff, P. J.; Sauerbrey, Roland A.

1989-06-01

Excimer lasers emit light energy, short optical pulses at ultraviolet wavelengths, that results in a unique laser tissue interaction. This has led to an increasing number of studies into medical applications of these lasers in fields such as ophthalmology, urology, cardiology and neurology.

Single-shot spectro-temporal characterization of XUV pulses from a seeded free-electron laser

PubMed Central

De Ninno, Giovanni; Gauthier, David; Mahieu, Benoît; Ribič, Primož Rebernik; Allaria, Enrico; Cinquegrana, Paolo; Danailov, Miltcho Bojanov; Demidovich, Alexander; Ferrari, Eugenio; Giannessi, Luca; Penco, Giuseppe; Sigalotti, Paolo; Stupar, Matija

2015-01-01

Intense ultrashort X-ray pulses produced by modern free-electron lasers (FELs) allow one to probe biological systems, inorganic materials and molecular reaction dynamics with nanoscale spatial and femtoscale temporal resolution. These experiments require the knowledge, and possibly the control, of the spectro-temporal content of individual pulses. FELs relying on seeding have the potential to produce spatially and temporally fully coherent pulses. Here we propose and implement an interferometric method, which allows us to carry out the first complete single-shot spectro-temporal characterization of the pulses, generated by an FEL in the extreme ultraviolet spectral range. Moreover, we provide the first direct evidence of the temporal coherence of a seeded FEL working in the extreme ultraviolet spectral range and show the way to control the light generation process to produce Fourier-limited pulses. Experiments are carried out at the FERMI FEL in Trieste. PMID:26290320

The development of a tunable, single-frequency ultraviolet laser source for UV filtered Rayleigh scattering

NASA Technical Reports Server (NTRS)

Finkelstein, N.; Gambogi, J.; Lempert, Walter R.; Miles, Richard B.; Rines, G. A.; Finch, A.; Schwarz, R. A.

1995-01-01

We present the development of a flexible, high power, narrow line width, tunable ultraviolet source for diagnostic application. By frequency tripling the output of a pulsed titanium-sapphire laser, we achieve broadly tunable (227-360 nm) ultraviolet light with high quality spatial and spectral resolution. We also present the characterization of a mercury vapor cell which provides a narrow band, sharp edge absorption filter at 253.7 nm. These two components form the basis for the extension of the Filtered Rayleigh Scattering technique into the ultraviolet. The UV-FRS system is comprised of four pieces: a single frequency, cw tunable Ti:Sapphire seeding source; a high-powered pulsed Ti:Sapphire oscillator; a third harmonic generator system; and an atomic mercury vapor filter. In this paper we discuss the development and characterization of each of these elements.

Construction and characterization of ultraviolet acousto-optic based femtosecond pulse shapers

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

Mcgrane, Shawn D; Moore, David S; Greenfield, Margo T

2008-01-01

We present all the information necessary for construction and characterization of acousto optic pulse shapers, with a focus on ultraviolet wavelengths, Various radio-frequency drive configurations are presented to allow optimization via knowledgeable trade-off of design features. Detailed performance characteristics of a 267 nm acousto-optic modulator (AOM) based pulse shaper are presented, Practical considerations for AOM based pulse shaping of ultra-broad bandwidth (sub-10 fs) amplified femtosecond pulse shaping are described, with particular attention paid to the effects of the RF frequency bandwidth and optical frequency bandwidth on the spatial dispersion of the output laser pulses.

Evaluation of Analysis Conditions for Laser-Pulsed Atom Probe Tomography: Example of Cemented Tungsten Carbide.

PubMed

Peng, Zirong; Choi, Pyuck-Pa; Gault, Baptiste; Raabe, Dierk

2017-04-01

Cemented tungsten carbide has been analyzed using laser-pulsed atom probe tomography (APT). The influence of experimental parameters, including laser pulse energy, pulse repetition rate, and specimen base temperature, on the acquired data were evaluated from different aspects, such as mass spectrum, chemical composition, noise-to-signal ratio, and multiple events. Within all the applied analysis conditions, only 1 MHz pulse repetition rate led to a strong detector saturation effect, resulting in a largely biased chemical composition. A comparative study of the laser energy settings showed that an ~12 times higher energy was required for the less focused green laser of the LEAPTM 3000X HR system to achieve a similar evaporation field as the finer spot ultraviolet laser of the LEAPTM 5000 XS system.

Investigation of optical fibers for gas-phase, ultraviolet laser-induced-fluorescence (UV-LIF) spectroscopy.

PubMed

Hsu, Paul S; Kulatilaka, Waruna D; Jiang, Naibo; Gord, James R; Roy, Sukesh

2012-06-20

We investigate the feasibility of transmitting high-power, ultraviolet (UV) laser pulses through long optical fibers for laser-induced-fluorescence (LIF) spectroscopy of the hydroxyl radical (OH) and nitric oxide (NO) in reacting and non-reacting flows. The fundamental transmission characteristics of nanosecond (ns)-duration laser pulses are studied at wavelengths of 283 nm (OH excitation) and 226 nm (NO excitation) for state-of-the-art, commercial UV-grade fibers. It is verified experimentally that selected fibers are capable of transmitting sufficient UV pulse energy for single-laser-shot LIF measurements. The homogeneous output-beam profile resulting from propagation through a long multimode fiber is ideal for two-dimensional planar-LIF (PLIF) imaging. A fiber-coupled UV-LIF system employing a 6 m long launch fiber is developed for probing OH and NO. Single-laser-shot OH- and NO-PLIF images are obtained in a premixed flame and in a room-temperature NO-seeded N(2) jet, respectively. Effects on LIF excitation lineshapes resulting from delivering intense UV laser pulses through long fibers are also investigated. Proof-of-concept measurements demonstrated in the current work show significant promise for fiber-coupled UV-LIF spectroscopy in harsh diagnostic environments such as gas-turbine test beds.

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.

Energy transport in short-pulse-laser-heated targets measured using extreme ultraviolet laser backlighting.

PubMed

Wilson, L A; Tallents, G J; Pasley, J; Whittaker, D S; Rose, S J; Guilbaud, O; Cassou, K; Kazamias, S; Daboussi, S; Pittman, M; Delmas, O; Demailly, J; Neveu, O; Ros, D

2012-08-01

The accurate characterization of thermal electron transport and the determination of heating by suprathermal electrons in laser driven solid targets are both issues of great importance to the current experiments being performed at the National Ignition Facility, which aims to achieve thermonuclear fusion ignition using lasers. Ionization, induced by electronic heat conduction, can cause the opacity of a material to drop significantly once bound-free photoionization is no longer energetically possible. We show that this drop in opacity enables measurements of the transmission of extreme ultraviolet (EUV) laser pulses at 13.9 nm to act as a signature of the heating of thin (50 nm) iron layers with a 50-nm thick parylene-N (CH) overlay irradiated by 35-fs pulses at irradiance 3×10(16) Wcm(-2). Comparing EUV transmission measurements at different times after irradiation to fluid code simulations shows that the target is instantaneously heated by hot electrons (with approximately 10% of the laser energy), followed by thermal conduction with a flux limiter of ≈0.05.

Low-debris, efficient laser-produced plasma extreme ultraviolet source by use of a regenerative liquid microjet target containing tin dioxide (SnO2) nanoparticles

NASA Astrophysics Data System (ADS)

Higashiguchi, Takeshi; Dojyo, Naoto; Hamada, Masaya; Sasaki, Wataru; Kubodera, Shoichi

2006-05-01

We demonstrated a low-debris, efficient laser-produced plasma extreme ultraviolet (EUV) source by use of a regenerative liquid microjet target containing tin-dioxide (SnO2) nanoparticles. By using a low SnO2 concentration (6%) solution and dual laser pulses for the plasma control, we observed the EUV conversion efficiency of 1.2% with undetectable debris.

Absolute Two-Photon Absorption Coefficients in UltraViolet Window Materials

DTIC Science & Technology

1977-12-01

fvtt* tld » II ntctHB,-y md Idtnlll’ by block number; The absolute two-photon absorption coefficiehts of u. v. transmitting materials have been...measured using well-calibrated single picosecond pulses, at the third and fourth harmonic of a mode locked Nd:YAG laser systems. Twc photon...30, 1977. Work in the area of laser induced breakdown and multiphoton absorption in ultraviolet and infrared laser window materials was carried

Analysis of fabric materials cut using ultraviolet laser ablation

NASA Astrophysics Data System (ADS)

Tsai, Hsin-Yi; Yang, Chih-Chung; Hsiao, Wen-Tse; Huang, Kuo-Cheng; Andrew Yeh, J.

2016-04-01

Laser ablation technology has widely been applied in the clothing industry in recent years. However, the laser mechanism would affect the quality of fabric contours and its components. Hence, this study examined carbonization and oxidation conditions and contour variation in nonwoven, cotton, and composite leather fabrics cut by using an ultraviolet laser at a wavelength of 355 nm. Processing parameters such as laser power, pulse frequency, scanning speed, and number of pulses per spot were adjusted to investigate component variation of the materials and to determine suitable cutting parameters for the fabrics. The experimental results showed that the weights of the component changed substantially by pulse frequency but slightly by laser power, so pulse frequency of 100 kHz and laser power of 14 W were the approximate parameters for three fabrics for the smaller carbonization and a sufficient energy for rapidly cutting, which the pulse duration of laser system was fixed at 300 μs and laser irradiance was 0.98 J/mm2 simultaneously. In addition, the etiolate phenomenon of nonwoven was reduced, and the component weight of cotton and composite leather was closed to the value of knife-cut fabric as the scanning speed increased. The approximate scanning speed for nonwoven and composite leather was 200 mm/s, and one for cotton was 150 mm/s, respectively. The sharper and firmer edge is obtained by laser ablation mechanism in comparison with traditional knife cutting. Experimental results can serve as the reference for laser cutting in the clothing industry, for rapidly providing smoother patterns with lower carbonization and oxidation edge in the fashion industry.

Investigation of optical fibers for high-repetition-rate, ultraviolet planar laser-induced fluorescence of OH.

PubMed

Hsu, Paul S; Kulatilaka, Waruna D; Roy, Sukesh; Gord, James R

2013-05-01

We investigate the fundamental transmission characteristics of nanosecond-duration, 10 kHz repetition rate, ultraviolet (UV) laser pulses through state-of-the-art, UV-grade fused-silica fibers being used for hydroxyl radical (OH) planar laser-induced fluorescence (PLIF) imaging. Studied in particular are laser-induced damage thresholds (LIDTs), nonlinear absorption, and optical transmission stability during long-term UV irradiation. Solarization (photodegradation) effects are significantly enhanced when the fiber is exposed to high-repetition-rate, 283 nm UV irradiation. For 10 kHz laser pulses, two-photon absorption is strong and LIDTs are low, as compared to those of laser pulses propagating at 10 Hz. The fiber characterization results are utilized to perform single-laser-shot, OH-PLIF imaging in pulsating turbulent flames with a laser that operates at 10 kHz. The nearly spatially uniform output beam that exits a long multimode fiber becomes ideal for PLIF measurements. The proof-of-concept measurements show significant promise for extending the application of a fiber-coupled, high-speed OH-PLIF system to harsh environments such as combustor test beds, and potential system improvements are suggested.

Angular distribution of ions and extreme ultraviolet emission in laser-produced tin droplet plasma

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

Chen, Hong; Duan, Lian; Lan, Hui

Angular-resolved ion time-of-flight spectra as well as extreme ultraviolet radiation in laser-produced tin droplet plasma are investigated experimentally and theoretically. Tin droplets with a diameter of 150 μm are irradiated by a pulsed Nd:YAG laser. The ion time-of-flight spectra measured from the plasma formed by laser irradiation of the tin droplets are interpreted in terms of a theoretical elliptical Druyvesteyn distribution to deduce ion density distributions including kinetic temperatures of the plasma. The opacity of the plasma for extreme ultraviolet radiation is calculated based on the deduced ion densities and temperatures, and the angular distribution of extreme ultraviolet radiation is expressedmore » as a function of the opacity using the Beer–Lambert law. Our results show that the calculated angular distribution of extreme ultraviolet radiation is in satisfactory agreement with the experimental data.« less

Angular distribution of ions and extreme ultraviolet emission in laser-produced tin droplet plasma

NASA Astrophysics Data System (ADS)

Chen, Hong; Wang, Xinbing; Duan, Lian; Lan, Hui; Chen, Ziqi; Zuo, Duluo; Lu, Peixiang

2015-05-01

Angular-resolved ion time-of-flight spectra as well as extreme ultraviolet radiation in laser-produced tin droplet plasma are investigated experimentally and theoretically. Tin droplets with a diameter of 150 μm are irradiated by a pulsed Nd:YAG laser. The ion time-of-flight spectra measured from the plasma formed by laser irradiation of the tin droplets are interpreted in terms of a theoretical elliptical Druyvesteyn distribution to deduce ion density distributions including kinetic temperatures of the plasma. The opacity of the plasma for extreme ultraviolet radiation is calculated based on the deduced ion densities and temperatures, and the angular distribution of extreme ultraviolet radiation is expressed as a function of the opacity using the Beer-Lambert law. Our results show that the calculated angular distribution of extreme ultraviolet radiation is in satisfactory agreement with the experimental data.

All-solid-state deep ultraviolet laser for single-photon ionization mass spectrometry.

PubMed

Yuan, Chengqian; Liu, Xianhu; Zeng, Chenghui; Zhang, Hanyu; Jia, Meiye; Wu, Yishi; Luo, Zhixun; Fu, Hongbing; Yao, Jiannian

2016-02-01

We report here the development of a reflectron time-of-flight mass spectrometer utilizing single-photon ionization based on an all-solid-state deep ultraviolet (DUV) laser system. The DUV laser was achieved from the second harmonic generation using a novel nonlinear optical crystal KBe2BO3F2 under the condition of high-purity N2 purging. The unique property of this laser system (177.3-nm wavelength, 15.5-ps pulse duration, and small pulse energy at ∼15 μJ) bears a transient low power density but a high single-photon energy up to 7 eV, allowing for ionization of chemicals, especially organic compounds free of fragmentation. Taking this advantage, we have designed both pulsed nanospray and thermal evaporation sources to form supersonic expansion molecular beams for DUV single-photon ionization mass spectrometry (DUV-SPI-MS). Several aromatic amine compounds have been tested revealing the fragmentation-free performance of the DUV-SPI-MS instrument, enabling applications to identify chemicals from an unknown mixture.

Compact, passively Q-switched, all-solid-state master oscillator-power amplifier-optical parametric oscillator (MOPA-OPO) system pumped by a fiber-coupled diode laser generating high-brightness, tunable, ultraviolet radiation.

PubMed

Peuser, Peter; Platz, Willi; Fix, Andreas; Ehret, Gerhard; Meister, Alexander; Haag, Matthias; Zolichowski, Paul

2009-07-01

We report on a compact, tunable ultraviolet laser system that consists of an optical parametric oscillator (OPO) and a longitudinally diode-pumped Nd:YAG master oscillator-power amplifier (MOPA). The pump energy for the whole laser system is supplied via a single delivery fiber. Nanosecond pulses are produced by an oscillator that is passively Q-switched by a Cr(4+):YAG crystal. The OPO is pumped by the second harmonic of the Nd:YAG MOPA. Continuously tunable radiation is generated by an intracavity sum-frequency mixing process within the OPO in the range of 245-260 nm with high beam quality. Maximum pulse energies of 1.2 mJ were achieved, which correspond to an optical efficiency of 3.75%, relating to the pulse energy of the MOPA at 1064 nm.

Recycling of laser and plasma radiation energy for enhancement of extreme ultraviolet sources for nanolithography

NASA Astrophysics Data System (ADS)

Sizyuk, V.; Sizyuk, T.; Hassanein, A.; Johnson, K.

2018-01-01

We have developed comprehensive integrated models for detailed simulation of laser-produced plasma (LPP) and laser/target interaction, with potential recycling of the escaping laser and out-of-band plasma radiation. Recycling, i.e., returning the escaping laser and plasma radiation to the extreme ultraviolet (EUV) generation region using retroreflective mirrors, has the potential of increasing the EUV conversion efficiency (CE) by up to 60% according to our simulations. This would result in significantly reduced power consumption and/or increased EUV output. Based on our recently developed models, our High Energy Interaction with General Heterogeneous Target Systems (HEIGHTS) computer simulation package was upgraded for LPP devices to include various radiation recycling regimes and to estimate the potential CE enhancement. The upgraded HEIGHTS was used to study recycling of both laser and plasma-generated radiation and to predict possible gains in conversion efficiency compared to no-recycling LPP devices when using droplets of tin target. We considered three versions of the LPP system including a single CO2 laser, a single Nd:YAG laser, and a dual-pulse device combining both laser systems. The gains in generating EUV energy were predicted and compared for these systems. Overall, laser and radiation energy recycling showed the potential for significant enhancement in source efficiency of up to 60% for the dual-pulse system. Significantly higher CE gains might be possible with optimization of the pre-pulse and main pulse parameters and source size.

Laser-induced reduction of graphene oxide powders by high pulsed ultraviolet laser irradiations

NASA Astrophysics Data System (ADS)

Yang, Chii-Rong; Tseng, Shih-Feng; Chen, Yu-Ting

2018-06-01

This study aims to develop a laser-induced reduction approach for graphene oxide (GO) powders fabricated by using high pulsed ultraviolet laser irradiations. Before and after the laser irradiation with different fluences, the physical and electrical properties of homemade GO powders and reduced graphene oxide (rGO) powders were measured and analyzed using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), surface area analyzer, and four-point probe instrument. The laser irradiation parameters included the pulse repetition frequency of 100 kHz, the scanning speed of galvanometers of 50 mm/s, the number of laser irradiated cycles of 10, and the laser fluences of ranging from 0.153 mJ/cm2 to 0.525 mJ/cm2. The laser reduction experiments of GO powders demonstrated that the largest relative intensity of the 2D peak and specific surface area were found at the laser fluence of 0.438 mJ/cm2. Moreover, the electrical resistance sharply decreased from 280 MΩ in the initial GO powders to 0.267 MΩ in rGO powders at a laser irradiation fluence of 0.438. The C/O ratio was increased from 0.232 in the initial GO powders to 1.86 in the rGO powders at a laser irradiation fluence of 0.525 mJ/cm2; furthermore, the C/O ratios increased with increasing the laser fluences.

Green and ultraviolet pulse generation with a compact, fiber laser, chirped-pulse amplification system for aerosol fluorescence measurements.

PubMed

Lou, Janet W; Currie, Marc; Sivaprakasam, Vasanthi; Eversole, Jay D

2010-10-01

We use a compact chirped-pulse amplified system to harmonically generate ultrashort pulses for aerosol fluorescence measurements. The seed laser is a compact, all-normal dispersion, mode-locked Yb-doped fiber laser with a 1050 nm center wavelength operating at 41 MHz. Average powers of more than 1.2 W at 525 nm and 350 mW at 262 nm are generated with <500 fs pulse durations. The pulses are time-stretched with high-dispersion fiber, amplified by a high-power, large-mode-area fiber amplifier, and recompressed using a chirped volume holographic Bragg grating. The resulting high-peak-power pulses allow for highly efficient harmonic generation. We also demonstrate for the first time to our knowledge, the use of a mode-locked ultraviolet source to excite individual biological particles and other calibration particles in an inlet air flow as they pass through an optical chamber. The repetition rate is ideal for biofluorescence measurements as it allows faster sampling rates as well as the higher peak powers as compared to previously demonstrated Q-switched systems while maintaining a pulse period that is longer than the typical fluorescence lifetimes. Thus, the fluorescence excitation can be considered to be quasicontinuous and requires no external synchronization and triggering.

Laser-assisted solar cell metallization processing

NASA Technical Reports Server (NTRS)

Dutta, S.

1984-01-01

Laser-assisted processing techniques utilized to produce the fine line, thin metal grid structures that are required to fabricate high efficiency solar cells are examined. Two basic techniques for metal deposition are investigated; (1) photochemical decomposition of liquid or gas phase organometallic compounds utilizing either a focused, CW ultraviolet laser (System 1) or a mask and ultraviolet flood illumination, such as that provided by a repetitively pulsed, defocused excimer laser (System 2), for pattern definition, and (2) thermal deposition of metals from organometallic solutions or vapors utilizing a focused, CW laser beam as a local heat source to draw the metallization pattern.

Enhanced hole boring with two-color relativistic laser pulses in the fast ignition scheme

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

Yu, Changhai; Tian, Ye; Li, Wentao

A scheme of using two-color laser pulses for hole boring into overdense plasma as well as energy transfer into electron and ion beams has been studied using particle-in-cell simulations. Following an ultra-short ultra-intense hole-boring laser pulse with a short central wavelength in extreme ultra-violet range, the main infrared driving laser pulse can be guided in the hollow channel preformed by the former laser and propagate much deeper into an overdense plasma, as compared to the case using the infrared laser only. In addition to efficiently transferring the main driving laser energy into energetic electrons and ions generation deep inside themore » overdense plasma, the ion beam divergence can be greatly reduced. The results might be beneficial for the fast ignition concept of inertial confinement fusion.« less

Spatio-temporal shaping of photocathode laser pulses for linear electron accelerators

NASA Astrophysics Data System (ADS)

Mironov, S. Yu; Andrianov, A. V.; Gacheva, E. I.; Zelenogorskii, V. V.; Potemkin, A. K.; Khazanov, E. A.; Boonpornprasert, P.; Gross, M.; Good, J.; Isaev, I.; Kalantaryan, D.; Kozak, T.; Krasilnikov, M.; Qian, H.; Li, X.; Lishilin, O.; Melkumyan, D.; Oppelt, A.; Renier, Y.; Rublack, T.; Felber, M.; Huck, H.; Chen, Y.; Stephan, F.

2017-10-01

Methods for the spatio-temporal shaping of photocathode laser pulses for generating high brightness electron beams in modern linear accelerators are discussed. The possibility of forming triangular laser pulses and quasi-ellipsoidal structures is analyzed. The proposed setup for generating shaped laser pulses was realised at the Institute of Applied Physics (IAP) of the Russian Academy of Sciences (RAS). Currently, a prototype of the pulse-shaping laser system is installed at the Photo Injector Test facility at DESY, Zeuthen site (PITZ). Preliminary experiments on electron beam generation using ultraviolet laser pulses from this system were carried out at PITZ, in which electron bunches with a 0.5-nC charge and a transverse normalized emittance of 1.1 mm mrad were obtained. A new scheme for the three-dimensional shaping of laser beams using a volume Bragg profiled grating is proposed at IAP RAS and is currently being tested for further electron beam generation experiments at the PITZ photoinjector.

X-Ray Radiation Measurements With Photodiodes In Plasmas Generated By 1017 W/Cm2 Intensity Krf Excimer Laser Pulses

NASA Astrophysics Data System (ADS)

Rácz, E.; Földes, I. B.; Ryć, L.

2006-01-01

Experiments were carried out using a prepulse-free hybrid KrF excimer-dye laser system (700fs pulse duration, 248nm wavelength, 15mJ pulse energy). The intensity of the p-polarized, focused laser beam was 1.5ṡ1017 W/cm2. Vacuum ultraviolet (VUV) and x-rays from solid state laser plasmas were generated in the laser-plasma interaction of subpicosecond laser pulses of nonrelativistic laser intensities. An x-ray sensitive FLM photodiode (ITE, Warsaw) was used to detect x-rays between 1-19 keV in front of the targets. The diode was filtered by a 4μm Al foil. The dependence of the x-ray flux on laser intensity and the angular distribution of x-rays for aluminum and copper targets in the half space of the front side of the targets were investigated.

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

Abudureyimu, Reheman; Huang, Chunning; Liu, Yun

We report on a first experimental demonstration of locking a doubly-resonant Fabry-Perot cavity to burst-mode picosecond ultraviolet (UV) pulses by using a temperature controlled dispersion compensation method. This technique will eventually enable the intra cavity power enhancement of burst-mode 402.5MHz/50ps UV laser pulses with a MW level peak power required for the laser assisted H- beam stripping experiment at the Spallation Neutron Source.

High-speed photorefractive keratectomy with femtosecond ultraviolet pulses

NASA Astrophysics Data System (ADS)

Danieliene, Egle; Gabryte, Egle; Vengris, Mikas; Ruksenas, Osvaldas; Gutauskas, Algimantas; Morkunas, Vaidotas; Danielius, Romualdas

2015-05-01

Femtosecond near-infrared lasers are widely used for a number of ophthalmic procedures, with flap cutting in the laser-assisted in situ keratomileusis (LASIK) surgery being the most frequent one. At the same time, lasers of this type, equipped with harmonic generators, have been shown to deliver enough ultraviolet (UV) power for the second stage of the LASIK procedure, the stromal ablation. However, the speed of the ablation reported so far was well below the currently accepted standards. Our purpose was to perform high-speed photorefractive keratectomy (PRK) with femtosecond UV pulses in rabbits and to evaluate its predictability, reproducibility and healing response. The laser source delivered femtosecond 206 nm pulses with a repetition rate of 50 kHz and an average power of 400 mW. Transepithelial PRK was performed using two different ablation protocols, to a total depth of 110 and 150 μm. The surface temperature was monitored during ablation; haze dynamics and histological samples were evaluated to assess outcomes of the PRK procedure. For comparison, analogous excimer ablation was performed. Increase of the ablation speed up to 1.6 s/diopter for a 6 mm optical zone using femtosecond UV pulses did not significantly impact the healing process.

Locking the waveform with a quartz crystal

NASA Astrophysics Data System (ADS)

Ghimire, Shambhu

2018-05-01

High-order harmonics in the extreme-ultraviolet regime can be produced and a stable waveform-locked attosecond pulse can be formed when quartz is excited by a strong short-pulsed laser, providing a robust path towards attosecond photonics.

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.

Watching electrons tunnel

NASA Astrophysics Data System (ADS)

Moser, Simon

2008-03-01

To get insight to time resolved inner atomic or molecular processes, laser pulses of few femtoseconds or even attoseconds are needed. These short light pulse techniques ask for broad frequency spectra, control of dispersion and control of phase. Hence, linear optics fails and nonlinear optics in high electromagnetic fields is needed to satisfy the amount of control that is needed. One recent application of attosecond laser pulses is time resolved visualization of tunnel ionization in atoms applied to high electromagnetic fields. Here, Ne atom electrons are excited by an extreme ultraviolet attosecond laser pulse. After a while, a few cycles nearly infrared femtosecond laser pulse is applied to the atom causing tunnel ionization. The ion yield distribution can be measured as function of the delay time between excitation and ionization and so deliver insight to the time resolved mechanisms.

Coherent diffractive imaging of single helium nanodroplets with a high harmonic generation source.

PubMed

Rupp, Daniela; Monserud, Nils; Langbehn, Bruno; Sauppe, Mario; Zimmermann, Julian; Ovcharenko, Yevheniy; Möller, Thomas; Frassetto, Fabio; Poletto, Luca; Trabattoni, Andrea; Calegari, Francesca; Nisoli, Mauro; Sander, Katharina; Peltz, Christian; J Vrakking, Marc; Fennel, Thomas; Rouzée, Arnaud

2017-09-08

Coherent diffractive imaging of individual free nanoparticles has opened routes for the in situ analysis of their transient structural, optical, and electronic properties. So far, single-shot single-particle diffraction was assumed to be feasible only at extreme ultraviolet and X-ray free-electron lasers, restricting this research field to large-scale facilities. Here we demonstrate single-shot imaging of isolated helium nanodroplets using extreme ultraviolet pulses from a femtosecond-laser-driven high harmonic source. We obtain bright wide-angle scattering patterns, that allow us to uniquely identify hitherto unresolved prolate shapes of superfluid helium droplets. Our results mark the advent of single-shot gas-phase nanoscopy with lab-based short-wavelength pulses and pave the way to ultrafast coherent diffractive imaging with phase-controlled multicolor fields and attosecond pulses.Diffraction imaging studies of free individual nanoparticles have so far been restricted to XUV and X-ray free - electron laser facilities. Here the authors demonstrate the possibility of using table-top XUV laser sources to image prolate shapes of superfluid helium droplets.

Interaction of nanosecond ultraviolet laser pulses with reactive dusty plasma

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

Wetering, F. M. J. H. van de; Oosterbeek, W.; Beckers, J.

2016-05-23

Even though UV laser pulses that irradiate a gas discharge are small compared to the plasma volume (≲3%) and plasma-on time (≲6 × 10{sup −6}%), they are found to dramatically change the discharge characteristics on a global scale. The reactive argon–acetylene plasma allows the growth of nanoparticles with diameters up to 1 μm, which are formed inside the discharge volume due to spontaneous polymerization reactions. It is found that the laser pulses predominantly accelerate and enhance the coagulation phase and are able to suppress the formation of a dust void.

Dynamics of defects in Ce³⁺ doped silica affecting its performance as protective filter in ultraviolet high-power lasers.

PubMed

Demos, Stavros G; Ehrmann, Paul R; Qiu, S Roger; Schaffers, Kathleen I; Suratwala, Tayyab I

2014-11-17

We investigate defects forming in Ce³⁺-doped fused silica samples following exposure to nanosecond ultraviolet laser pulses and their relaxation as a function of time and exposure to low intensity light at different wavelengths. A subset of these defects are responsible for inducing absorption in the visible and near infrared spectral range, which is of critical importance for the use of this material as ultraviolet light absorbing filter in high power laser systems. The dependence of the induced absorption as a function of laser fluence and methods to most efficiently mitigate this effect are presented. Experiments simulating the operation of the material as a UV protection filter for high power laser systems were performed in order to determine limitations and practical operational conditions.

Spectral lines and characteristic of temporal variations in photoionized plasmas induced with laser-produced plasma extreme ultraviolet source

NASA Astrophysics Data System (ADS)

Saber, I.; Bartnik, A.; Wachulak, P.; Skrzeczanowski, W.; Jarocki, R.; Fiedorowicz, H.

2017-11-01

Spectral lines for Kr/Ne/H2 photoionized plasma in the ultraviolet and visible (UV/Vis) wavelength ranges have been created using a laser-produced plasma (LPP) EUV source. The source is based on a double-stream gas puff target irradiated with a commercial Nd:YAG laser. The laser pulses were focused onto a gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Spectral lines from photoionization in neutral Kr/Ne/H2 and up to few charged states were observed. The intense emission lines were associated with the Kr transition lines. Experimental and theoretical investigations on intensity variations for some ionic lines are presented. A decrease in the intensity with the delay time between the laser pulse and the spectrum acquisition was revealed. Electron temperature and electron density in the photoionized plasma have been estimated from the characteristic emission lines. Temperature was obtained using Boltzmann plot method, assuming that the population density of atoms and ions are considered in a local thermodynamic equilibrium (LTE). Electron density was calculated from the Stark broadening profile. The temporal evaluation of the plasma and the way of optimizing the radiation intensity of LPP EUV sources is discussed.

FAST TRACK COMMUNICATION: Inhomogeneous charge redistribution in Xe clusters exposed to an intense extreme ultraviolet free electron laser

NASA Astrophysics Data System (ADS)

Iwayama, H.; Sugishima, A.; Nagaya, K.; Yao, M.; Fukuzawa, H.; Motomura, K.; Liu, X.-J.; Yamada, A.; Wang, C.; Ueda, K.; Saito, N.; Nagasono, M.; Tono, K.; Yabashi, M.; Ishikawa, T.; Ohashi, H.; Kimura, H.; Togashi, T.

2010-08-01

The emission of highly charged ions from Xe clusters exposed to intense extreme ultraviolet laser pulses (λ ~ 52 nm) from the free electron laser in Japan was investigated using ion momentum spectroscopy. With increasing average cluster size, we observed multiply charged ions Xez + up to z = 3. From kinetic energy distributions, we found that multiply charged ions were generated near the cluster surface. Our results suggest that charges are inhomogeneously redistributed in the cluster to lower the total energy stored in the clusters.

Ultraviolet laser ablation as technique for defect repair of GaN-based light-emitting diodes

NASA Astrophysics Data System (ADS)

Passow, Thorsten; Kunzer, Michael; Pfeuffer, Alexander; Binder, Michael; Wagner, Joachim

2018-03-01

Defect repair of GaN-based light-emitting diodes (LEDs) by ultraviolet laser micromachining is reported. Percussion and helical drilling in GaN by laser ablation were investigated using 248 nm nanosecond and 355 nm picosecond pulses. The influence of laser ablation including different laser parameters on electrical and optical properties of GaN-based LED chips was evaluated. The results for LEDs on sapphire with transparent conductive oxide p-type contact on top as well as for thin-film LEDs are reported. A reduction of leakage current by up to six orders in magnitude and homogeneous luminance distribution after proper laser defect treatment were achieved.

Application of Laser Plasma Sources of Soft X-rays and Extreme Ultraviolet (EUV) in Imaging, Processing Materials and Photoionization Studies

NASA Astrophysics Data System (ADS)

Fiedorowicz, H.; Bartnik, A.; Wachulak, P. W.; Jarocki, R.; Kostecki, J.; Szczurek, M.; Ahad, I. U.; Fok, T.; Szczurek, A.; Wȩgrzyński, Ł.

In the paper we present new applications of laser plasma sources of soft X-rays and extreme ultraviolet (EUV) in various areas of plasma physics, nanotechnology and biomedical engineering. The sources are based on a gas puff target irradiated with nanosecond laser pulses from commercial Nd: YAG lasers, generating pulses with time duration from 1 to 10 ns and energies from 0.5 to 10 J at a 10 Hz repetition rate. The targets are produced with the use of a double valve system equipped with a special nozzle to form a double-stream gas puff target which allows for high conversion efficiency of laser energy into soft X-rays and EUV without degradation of the nozzle. The sources are equipped with various optical systems to collect soft X-ray and EUV radiation and form the radiation beam. New applications of these sources in imaging, including EUV tomography and soft X-ray microscopy, processing of materials and photoionization studies are presented.

Direct measurement of the pulse duration and frequency chirp of seeded XUV free electron laser pulses

NASA Astrophysics Data System (ADS)

Azima, Armin; Bödewadt, Jörn; Becker, Oliver; Düsterer, Stefan; Ekanayake, Nagitha; Ivanov, Rosen; Kazemi, Mehdi M.; Lamberto Lazzarino, Leslie; Lechner, Christoph; Maltezopoulos, Theophilos; Manschwetus, Bastian; Miltchev, Velizar; Müller, Jost; Plath, Tim; Przystawik, Andreas; Wieland, Marek; Assmann, Ralph; Hartl, Ingmar; Laarmann, Tim; Rossbach, Jörg; Wurth, Wilfried; Drescher, Markus

2018-01-01

We report on a direct time-domain measurement of the temporal properties of a seeded free-electron laser pulse in the extreme ultraviolet spectral range. Utilizing the oscillating electromagnetic field of terahertz radiation, a single-shot THz streak-camera was applied for measuring the duration as well as spectral phase of the generated intense XUV pulses. The experiment was conducted at FLASH, the free electron laser user facility at DESY in Hamburg, Germany. In contrast to indirect methods, this approach directly resolves and visualizes the frequency chirp of a seeded free-electron laser (FEL) pulse. The reported diagnostic capability is a prerequisite to tailor amplitude, phase and frequency distributions of FEL beams on demand. In particular, it opens up a new window of opportunities for advanced coherent spectroscopic studies making use of the high degree of temporal coherence expected from a seeded FEL pulse.

Ultraviolet laser transverse profile shaping for improving x-ray free electron laser performance

DOE PAGES

Li, S.; Alverson, S.; Bohler, D.; ...

2017-08-17

The photocathode rf gun is one of the most critical components in x-ray free electron lasers. The drive laser strikes the photocathode surface, which emits electrons with properties that depend on the shape of the drive laser. Most free electron lasers use photocathodes with work function in the ultraviolet, a wavelength where direct laser manipulation becomes challenging. In this paper, we present a novel application of a digital micromirror device (DMD) for the 253 nm drive laser at the Linear Coherent Light Source. Laser profile shaping is accomplished through an iterative algorithm that takes into account shaping error and efficiency.more » Next, we use laser shaping to control the X-ray laser output via an online optimizer, which shows improvement in FEL pulse energy. Lastly, as a preparation for electron beam shaping, we use the DMD to measure the photocathode quantum efficiency across cathode surface with an averaged laser rms spot size of 59 μm. In conclusion, our experiments demonstrate promising outlook of using DMD to shape ultraviolet lasers for photocathode rf guns with various applications.« less

Ultraviolet laser transverse profile shaping for improving x-ray free electron laser performance

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

Li, S.; Alverson, S.; Bohler, D.

The photocathode rf gun is one of the most critical components in x-ray free electron lasers. The drive laser strikes the photocathode surface, which emits electrons with properties that depend on the shape of the drive laser. Most free electron lasers use photocathodes with work function in the ultraviolet, a wavelength where direct laser manipulation becomes challenging. In this paper, we present a novel application of a digital micromirror device (DMD) for the 253 nm drive laser at the Linear Coherent Light Source. Laser profile shaping is accomplished through an iterative algorithm that takes into account shaping error and efficiency.more » Next, we use laser shaping to control the X-ray laser output via an online optimizer, which shows improvement in FEL pulse energy. Lastly, as a preparation for electron beam shaping, we use the DMD to measure the photocathode quantum efficiency across cathode surface with an averaged laser rms spot size of 59 μm. In conclusion, our experiments demonstrate promising outlook of using DMD to shape ultraviolet lasers for photocathode rf guns with various applications.« less

Ultraviolet laser transverse profile shaping for improving x-ray free electron laser performance

NASA Astrophysics Data System (ADS)

Li, S.; Alverson, S.; Bohler, D.; Egger, A.; Fry, A.; Gilevich, S.; Huang, Z.; Miahnahri, A.; Ratner, D.; Robinson, J.; Zhou, F.

2017-08-01

The photocathode rf gun is one of the most critical components in x-ray free electron lasers. The drive laser strikes the photocathode surface, which emits electrons with properties that depend on the shape of the drive laser. Most free electron lasers use photocathodes with work function in the ultraviolet, a wavelength where direct laser manipulation becomes challenging. In this paper, we present a novel application of a digital micromirror device (DMD) for the 253 nm drive laser at the Linear Coherent Light Source. Laser profile shaping is accomplished through an iterative algorithm that takes into account shaping error and efficiency. Next, we use laser shaping to control the X-ray laser output via an online optimizer, which shows improvement in FEL pulse energy. Lastly, as a preparation for electron beam shaping, we use the DMD to measure the photocathode quantum efficiency across cathode surface with an averaged laser rms spot size of 59 μ m . Our experiments demonstrate promising outlook of using DMD to shape ultraviolet lasers for photocathode rf guns with various applications.

Comparative study on crystallization characteristics of amorphous Ge2Sb2Te5 films by an ultraviolet laser radiation and isothermal annealing

NASA Astrophysics Data System (ADS)

Zhu, Z.; Liu, F. R.; Wang, Z. M.; Fan, Z. K.; Liu, F.; Sun, N. X.

2015-04-01

A comparative study on crystallization characteristics of amorphous Ge2Sb2Te5 (GST) films induced by an ultraviolet pulse laser and isothermal annealing was carried out by using transmission electron microscopy (TEM) and Raman scattering. TEM observations showed that the mean grain size induced by a pulse laser was in the nanoscale. A more complete crystallization in the 50 nm thick GST film was obtained which was ascribed to the effect of thermal convection produced in a thinner GST film, however, when the film thickness was over 70 nm, no significant decrease in the mean grain size was found because of the effect of heating mode, where a surface heat source by the ultraviolet laser radiation caused a quick temperature drop. The body heating mode at the isothermal annealing condition made the mean grain size increase remarkably with the increase of film thickness, which could be up to the submicron scale, relative to the size of film thickness. The Raman spectrum analysis showed that a red shift was observed in laser induced Ge2Sb2Te5 films as compared to the isothermal annealing samples, which was caused by the resultant stress of the thermal stress and phase transformation stress.

Generation of UV light by intense ultrashort laser pulses in air

NASA Astrophysics Data System (ADS)

Alexeev, Ilya; Ting, Antonio; Gordon, Daniel; Briscoe, Eldridge; Penano, Joe; Sprangle, Phillip

2004-11-01

The propagation of collimated high-peak-power ultrashort laser pulses in air has attracted considerable attention, which may have a variety of important applications including remote sensing and chemical-biological aerosols standoff detection. Sub-millimeter diameter laser filaments can develop without any focusing optics and instead solely from laser self-focusing and plasma formation in air. These filaments can produce ultraviolet radiations in the form of the 3rd harmonic of the fundamental frequency and also through spectral broadening due to self-phase modulation of the laser pulse. Using femtosecond laser pulses produced by a high power Ti:Sapphire laser (0.8 TW, 50 fs, 800 nm) we observed generation of the third harmonic radiation light in air (centered around 267 nm) by the laser filaments. Characterization of the 3rd harmonic generation with respect to the major gas components of the air will be reported. Supported by the ONR and RDECOM. I. Alexeev is NRC/NRL Post-Doc.

Integrated ultraviolet and tunable mid-infrared laser source for analyses of proteins

NASA Astrophysics Data System (ADS)

Hazama, Hisanao; Takatani, Yoshiaki; Awazu, Kunio

2007-02-01

Mass spectrometry using matrix-assisted laser desorption/ionization (MALDI) technique is one of the most widely used method to analyze proteins in biological research fields. However, it is difficult to analyze insoluble proteins which have important roles in researches on disease mechanisms or in developments of drugs by using ultraviolet (UV) lasers which have commonly been used for MALDI. Recently, a significant improvement in MALDI process of insoluble proteins using a combination of a UV nitrogen laser and a tunable mid-infrared (MIR) free electron laser (FEL) was reported. Since the FEL is a very large and expensive equipment, we have developed a tabletop laser source which can generate both UV and tunable MIR lasers. A tunable MIR laser (5.5-10 μm) was obtained by difference frequency generation (DFG) between a Nd:YAG and a tunable Cr:forsterite lasers using two AgGaS II crystals. The MIR laser can generate pulses with an energy of up to 1.4 mJ at a repetition rate of 10 Hz. A UV laser was obtained by third harmonic generation of a Nd:YAG laser splitted from that used for DFG. A time interval between the UV and the MIR laser pulses can be adjusted with a variable optical delay.

Clean sub-8-fs pulses at 400 nm generated by a hollow fiber compressor for ultraviolet ultrafast pump-probe spectroscopy.

PubMed

Liu, Jun; Okamura, Kotaro; Kida, Yuichiro; Teramoto, Takahiro; Kobayashi, Takayoshi

2010-09-27

Clean 7.5 fs pulses at 400 nm with less than 3% energy in tiny satellite pulses were obtained by spectral broadening in a hollow fiber and dispersive compensating using a prism pair together with a deformable mirror system. As an example, this stable and clean pulse was used to study the ultrafast pump-probe spectroscopy of photoactive yellow protein. Moreover, the self-diffraction signal shows a smoothed and broadened laser spectrum and is expected to have a further clean laser pulse, which makes it more useful in the ultrafast pump-probe spectroscopy in the future.

Enhancement of Photon Number Reflected by the Relativistic Flying Mirror

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

Kando, M.; Pirozhkov, A. S.; Kawase, K.

2009-12-04

Laser light reflection by a relativistically moving electron density modulation (flying mirror) in a wake wave generated in a plasma by a high intensity laser pulse is investigated experimentally. A counterpropagating laser pulse is reflected and upshifted in frequency with a multiplication factor of 37-66, corresponding to the extreme ultraviolet wavelength. The demonstrated flying mirror reflectivity (from 3x10{sup -6} to 2x10{sup -5}, and from 1.3x10{sup -4} to 0.6x10{sup -3}, for the photon number and pulse energy, respectively) is close to the theoretical estimate for the parameters of the experiment.

Time-diagnostics for improved dynamics experiments at XUV FELs

NASA Astrophysics Data System (ADS)

Drescher, Markus; Frühling, Ulrike; Krikunova, Maria; Maltezopoulos, Theophilos; Wieland, Marek

2010-10-01

Significantly structured and fluctuating temporal profiles of pulses from self-amplified spontaneous emission free electron lasers as well as their unstable timing require time diagnostics on a single-shot basis. The duration and structure of extreme-ultraviolet (XUV) pulses from the Free Electron Laser (FEL) in Hamburg (FLASH) are becoming accessible using a variation of the streak camera principle, where photoemitted electrons are energetically streaked in the electric field component of a terahertz electromagnetic wave. The timing with respect to an independently generated laser pulse can be measured in an XUV/laser cross-correlator, based on a non-collinear superposition of both pulses on a solid state surface and detection of XUV-induced modulations of its reflectivity for visible light. Sorting of data according to the measured timing dramatically improves the temporal resolution of an experiment sampling the relaxation of transient electronic states in xenon after linear- as well as nonlinear excitation with intense XUV pulses from FLASH.

Plasma ignition thresholds in UV laser ablation plumes

NASA Astrophysics Data System (ADS)

Clarke, P.; Dyer, P. E.; Key, P. H.; Snelling, H. V.

Ultraviolet (UV) laser thresholds for plasma ignition on solid targets predicted from electron-neutral collisional heating are generally much higher than those observed experimentally. This inconsistency was reconciled by Rosen, et al. [2], who showed that excited-state photoionization played a key role in long-pulse UV laser breakdown. Here we develop a related model but with emphasis on pulses of 10 ns duration. Experimental results are also reported for titanium, copper, silicon, and ferulic acid targets in vacuum, irradiated with combinations of the XeF, KrF, and ArF lasers for comparison with predictions.

Detection limits of organic compounds achievable with intense, short-pulse lasers.

PubMed

Miles, Jordan; De Camillis, Simone; Alexander, Grace; Hamilton, Kathryn; Kelly, Thomas J; Costello, John T; Zepf, Matthew; Williams, Ian D; Greenwood, Jason B

2015-06-21

Many organic molecules have strong absorption bands which can be accessed by ultraviolet short pulse lasers to produce efficient ionization. This resonant multiphoton ionization scheme has already been exploited as an ionization source in time-of-flight mass spectrometers used for environmental trace analysis. In the present work we quantify the ultimate potential of this technique by measuring absolute ion yields produced from the interaction of 267 nm femtosecond laser pulses with the organic molecules indole and toluene, and gases Xe, N2 and O2. Using multiphoton ionization cross sections extracted from these results, we show that the laser pulse parameters required for real-time detection of aromatic molecules at concentrations of one part per trillion in air and a limit of detection of a few attomoles are achievable with presently available commercial laser systems. The potential applications for the analysis of human breath, blood and tissue samples are discussed.

Integrated oxide graphene based device for laser inactivation of pathogenic microorganisms

NASA Astrophysics Data System (ADS)

Grishkanich, Alexsandr; Ruzankina, Julia; Afanasyev, Mikhail; Paklinov, Nikita; Hafizov, Nail

2018-02-01

We develop device for virus disinfection of pathogenic microorganisms. Viral decontamination can be carried out due to hard ultraviolet irradiation and singlet oxygen destroying the genetic material of a virus capsid. UV rays can destroy DNA, leading to the formation of dimers of nucleic acids. This practically does not occur in tissues, tk. UV rays penetrate badly through them, however, the viral particles are small and UV can destroy their genetic material, RNA / DNA and the virus can not replicate. It is with the construction of the ultraviolet laser water disinfection system (UFLOV) based on the continuous and periodic pulsed ultraviolet laser sources (pump) binds to solve sterility and depyrogenation of water. It has been established that small doses of UV irradiation stimulate reproduction, and large doses cause the death of pathogenic microorganisms. The effect of a dose of ultraviolet is the result of photochemical action on the substance of a living bacterial cell or virion. Also complex photodynamic laser inactivation on graphene oxide is realized.

Isolation of Coherent Synchrotron Emission During Relativistic Laser Plasma Interactions

NASA Astrophysics Data System (ADS)

Dromey, B.; Rykovanov, S. G.; Lewis, C. L. S.; Zepf, M.

Coherent Synchrotron Emission (CSE) from relativistic laser plasmas (Pukhov et al., Plas Phys Control Fusion 52:124039, 2010; Dromey et al., Nat Phys 8:804-808, 2012; Dromey et al., New J Phys 15:015025, 2013) has recently been identified as a unique platform for the generation of coherent extreme ultraviolet (XUV) and X-Ray radiation with clear potential for bright attosecond pulse production. Exploiting this potential requires careful selection of interaction geometry, spectral wavelength range and target characteristics to allow the generation of high fidelity single attosecond pulses. In the laboratory the first step on this road is to study the individual mechanisms driving the emission of coherent extreme ultraviolet and X-Ray radiation during laser solid interactions in isolation. Here we show how interactions can be tailored to permit the unambiguous observation of coherent synchrotron emission (CSE) and the implications of this geometry for the resulting harmonic spectrum over the duration of the interaction.

Diagnosis of energy transport in iron buried layer targets using an extreme ultraviolet laser

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

Shahzad, M.; Culfa, O.; Rossall, A. K.

2015-02-15

We demonstrate the use of extreme ultra-violet (EUV) laboratory lasers in probing energy transport in laser irradiated solid targets. EUV transmission through targets containing a thin layer of iron (50 nm) encased in plastic (CH) after irradiation by a short pulse (35 fs) laser focussed to irradiances 3 × 10{sup 16} Wcm{sup −2} is measured. Heating of the iron layer gives rise to a rapid decrease in EUV opacity and an increase in the transmission of the 13.9 nm laser radiation as the iron ionizes to Fe{sup 5+} and above where the ion ionisation energy is greater than the EUV probe photon energy (89 eV).more » A one dimensional hydrodynamic fluid code HYADES has been used to simulate the temporal variation in EUV transmission (wavelength 13.9 nm) using IMP opacity values for the iron layer and the simulated transmissions are compared to measured transmission values. When a deliberate pre-pulse is used to preform an expanding plastic plasma, it is found that radiation is important in the heating of the iron layer while for pre-pulse free irradiation, radiation transport is not significant.« less

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

Measurement of temperature and density fluctuations in turbulence using an ultraviolet laser

NASA Technical Reports Server (NTRS)

Massey, G. A.

1984-01-01

Noninvasive measurement of density and temperature fluctuations in turbulent air flow was examined. The approach used fluorescence of oxygen molecules which are selectively excited by a tunable vacuum ultraviolet laser beam. The strength of the fluorescence signal and its dependence on laser wavelength vary with the density and temperature of the air in the laser beam. Because fluorescence can be detected at 90 degrees from the beam propagation direction, spatial resolution in three dimensions, rather than path-integrated measurements can be achieved. With spatial resolutions of the order of a millimeter and at supersonic air velocities it is necessary to perform each measurement in a time of the order of a microsecond; this is possible by by using laser pulses of ten nanosecond duration. In this method atmospheric O2 is excited by the emission of a tunable ArF excimer laser, and the fluorescence, which spans the 210 to 420 range, is detected by an ultraviolet phototube.

High speed micromachining with high power UV laser

NASA Astrophysics Data System (ADS)

Patel, Rajesh S.; Bovatsek, James M.

2013-03-01

Increasing demand for creating fine features with high accuracy in manufacturing of electronic mobile devices has fueled growth for lasers in manufacturing. High power, high repetition rate ultraviolet (UV) lasers provide an opportunity to implement a cost effective high quality, high throughput micromachining process in a 24/7 manufacturing environment. The energy available per pulse and the pulse repetition frequency (PRF) of diode pumped solid state (DPSS) nanosecond UV lasers have increased steadily over the years. Efficient use of the available energy from a laser is important to generate accurate fine features at a high speed with high quality. To achieve maximum material removal and minimal thermal damage for any laser micromachining application, use of the optimal process parameters including energy density or fluence (J/cm2), pulse width, and repetition rate is important. In this study we present a new high power, high PRF QuasarR 355-40 laser from Spectra-Physics with TimeShiftTM technology for unique software adjustable pulse width, pulse splitting, and pulse shaping capabilities. The benefits of these features for micromachining include improved throughput and quality. Specific example and results of silicon scribing are described to demonstrate the processing benefits of the Quasar's available power, PRF, and TimeShift technology.

Bubble formation during pulsed laser ablation: mechanism and implications

NASA Astrophysics Data System (ADS)

van Leeuwen, Ton G. J. M.; Jansen, E. Duco; Motamedi, Massoud; Welch, Ashley J.; Borst, Cornelius

1993-07-01

Holmium ((lambda) equals 2.09 micrometers ) and excimer ((lambda) equals 308 nm) lasers are used for ablation of tissue. In a previous study it was demonstrated that both excimer and holmium laser pulses produce fast expanding and collapsing vapor bubbles. To investigate whether the excimer induced bubble is caused by vaporization of water, the threshold fluence for bubble formation at a bare fiber tip in water was compared between the excimer laser (pulse length 115 ns) and the Q-switched and free-running holmium lasers (pulse length 1 microsecond(s) to 250 microsecond(s) , respectively). To induce bubble formation by excimer laser light in water, the absorber oxybuprocaine-hydrochloride (OBP-HCl) was added to the water. Fast flash photography was used to measure the threshold fluence as a function of the water temperature (6 - 90 degree(s)C) at environmental pressure. The ultraviolet excimer laser light is strongly absorbed by blood. Therefore, to document the implications of bubble formation at fluences above the tissue ablation threshold, excimer laser pulses were delivered in vitro in hemoglobin solution and in vivo in the femoral artery of the rabbit. We conclude that the principal content of the fast bubble induced by a 308 nm excimer laser pulse is water vapor. Therefore, delivery of excimer laser pulses in a water or blood environment will cause fast expanding water vapor bubbles, which may induce mechanical damage to adjacent tissue.

Influence of subsurface defects on damage performance of fused silica in ultraviolet laser

NASA Astrophysics Data System (ADS)

Huang, Jin; Zhou, Xinda; Liu, Hongjie; Wang, Fengrui; Jiang, Xiaodong; Wu, Weidong; Tang, Yongjian; Zheng, Wanguo

2013-02-01

In ultraviolet pulse laser, damage performance of fused silica optics is directly dependent on the absorptive impurities and scratches in subsurface, which are induced by mechanical polishing. In the research about influence of subsurface defects on damage performance, a series of fused silica surfaces with various impurity concentrations and scratch structures were created by hydrofluoric (HF) acid solution etching. Time of Flight secondary ion mass spectrometry and scanning probe microprobe revealed that with increasing etching depth, impurity concentrations in subsurface layers are decreased, the scratch structures become smoother and the diameter:depth ratio is increased. Damage performance test with 355-nm pulse laser showed that when 600 nm subsurface thickness is removed by HF acid etching, laser-induced damage threshold of fused silica is raised by 40 percent and damage density is decreased by over one order of magnitude. Laser weak absorption was tested to explain the cause of impurity elements impacting damage performance, field enhancement caused by change of scratch structures was calculated by finite difference time domain simulation, and the calculated results are in accord with the damage test results.

Bombyx mori silk protein films microprocessing with a nanosecond ultraviolet laser and a femtosecond laser workstation: theory and experiments

NASA Astrophysics Data System (ADS)

Lazare, S.; Sionkowska, A.; Zaborowicz, M.; Planecka, A.; Lopez, J.; Dijoux, M.; Louména, C.; Hernandez, M.-C.

2012-01-01

Laser microprocessing of several biopolymers from renewable resources is studied. Three proteinic materials were either extracted from the extracellular matrix like Silk Fibroin/Sericin and collagen, or coming from a commercial source like gelatin. All can find future applications in biomedical experimentation, in particular for cell scaffolding. Films of ˜hundred of microns thick were made by aqueous solution drying and laser irradiation. Attention is paid to the properties making them processable with two laser sources: the ultraviolet and nanosecond (ns) KrF (248 nm) excimer and the infrared and femtosecond (fs) Yb:KGW laser. The UV radiation is absorbed in a one-photon resonant process to yield ablation and the surface foaming characteristics of a laser-induced pressure wave. To the contrary, resonant absorption of the IR photons of the fs laser is not possible and does not take place. However, the high field of the intense I>˜1012 W/cm2 femtosecond laser pulse ionizes the film by the multiphoton absorption followed by the electron impact mechanism, yielding a dense plasma capable to further absorb the incident radiation of the end of the pulse. The theoretical model of this absorption is described in detail, and used to discuss the presented experimental effects (cutting, ablation and foaming) of the fs laser. The ultraviolet laser was used to perform simultaneous multiple spots experiments in which energetic foaming yields melt ejection and filament spinning. Airborne nanosize filaments "horizontally suspended by both ends" (0.25 μm diameter and 10 μm length) of silk biopolymer were observed upon irradiation with large fluences.

Prospects for a Novel Ultrashort Pulsed Laser Technology for Pathogen Inactivation

DTIC Science & Technology

2012-07-06

and Listeria [3-11]. The USP laser technology has the following advantages over the current methods of disinfection of pathogens: (1) With... Listeria monocytogenes Gram positive 10 3 Enterobacter Sakazakii Gram negative 10 3 (2) Existing disinfection methods such as irradiation of ultraviolet

CITIUS: An infrared-extreme ultraviolet light source for fundamental and applied ultrafast science

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

Grazioli, C.; Gauthier, D.; Ivanov, R.

2014-02-15

We present the main features of CITIUS, a new light source for ultrafast science, generating tunable, intense, femtosecond pulses in the spectral range from infrared to extreme ultraviolet (XUV). The XUV pulses (about 10{sup 5}-10{sup 8} photons/pulse in the range 14-80 eV) are produced by laser-induced high-order harmonic generation in gas. This radiation is monochromatized by a time-preserving monochromator, also allowing one to work with high-resolution bandwidth selection. The tunable IR-UV pulses (10{sup 12}-10{sup 15} photons/pulse in the range 0.4-5.6 eV) are generated by an optical parametric amplifier, which is driven by a fraction of the same laser pulse thatmore » generates high order harmonics. The IR-UV and XUV pulses follow different optical paths and are eventually recombined on the sample for pump-probe experiments. We also present the results of two pump-probe experiments: with the first one, we fully characterized the temporal duration of harmonic pulses in the time-preserving configuration; with the second one, we demonstrated the possibility of using CITIUS for selective investigation of the ultra-fast dynamics of different elements in a magnetic compound.« less

Generation of Bright Phase-matched Circularly-polarized Extreme Ultraviolet High Harmonics

DTIC Science & Technology

2014-12-08

circularly-polarized laser pulses field-ionize a gas in a hollow - core waveguide. We use this new light source for magnetic circular dichroism...polarized with opposite helicity in a gas-filled hollow waveguide (see Supplementary Section 6 for details on the important features of this source...mJ/pulse) driving lasers are focused into a 150-µm-diameter, 2-cm-long gas-filled hollow waveguide using lenses with focal lengths of 50 cm and 75 cm

Green synthesis of gold nanoparticles of different sizes and shapes using agar-agar water solution and femtosecond pulse laser irradiation

NASA Astrophysics Data System (ADS)

Almeida de Matos, Ricardo; da Silva Cordeiro, Thiago; Elgul Samad, Ricardo; Dias Vieira, Nilson; Coronato Courrol, Lilia

2012-11-01

We report a method to create gold nanoparticles of different sizes and shapes using agar-agar water solution and irradiation with light from a xenon lamp, followed by ultrashort laser pulses. No additives, such as solvents, surfactants or reducing agents, were used in the procedure. Laser irradiation (laser ablation) was important to the reduction of the nanoparticles diameter and formation of another shapes. Distilled water was used as solvent and agar-agar (hydrophilic colloid extracted from certain seaweeds) was important for the stabilization of gold nanoparticles, avoiding their agglomeration. The formation of gold nanoparticles was confirmed with ultraviolet-visible absorption and TEM microscopy. The gold nanoparticles acquired spherical, prism, and rod shapes depending on the laser parameters. Variation of laser irradiation parameters as pulse energy, irradiation time and repetition rate was assessed. The relevant mechanisms contributing for the gold nanoparticles production are discussed.

Extreme-ultraviolet-initiated high-order harmonic generation in Ar+

NASA Astrophysics Data System (ADS)

Clarke, D. D. A.; van der Hart, H. W.; Brown, A. C.

2018-02-01

We employ the R matrix with time dependence method to investigate extreme-ultraviolet-initiated high-order harmonic generation (XIHHG) in Ar+. Using a combination of extreme-ultraviolet (XUV, 92 nm, 3 ×1012W cm-2 ) and time-delayed, infrared (IR, 800 nm, 3 ×1014W cm-2 ) laser pulses, we demonstrate that control over both the mechanism and timing of ionization can afford significant enhancements in the yield of plateau and subthreshold harmonics alike. The presence of the XUV pulse is also shown to alter the relative contribution of different electron emission pathways. Manifestation of the Ar+ electronic structure is found in the appearance of a pronounced Cooper minimum. Interferences among the outer-valence 3 p and inner-valence 3 s electrons are found to incur only a minor suppression of the harmonic intensities, at least for the present combination of XUV and IR laser light. Additionally, the dependence of the XIHHG efficiency on time delay is discussed and rationalized with the aid of classical trajectory simulations.

Comparison of retina damage thresholds simulating the femtosecond-laser in situ keratomileusis (fs-LASIK) process with two laser systems in the CW- and fs-regime

NASA Astrophysics Data System (ADS)

Sander, M.; Minet, O.; Zabarylo, U.; Müller, M.; Tetz, M. R.

2012-04-01

The femtosecond-laser in situ keratomileusis procedure affords the opportunity to correct ametropia by cutting transparent corneal tissue with ultra-short laser pulses. Thereby the tissue cut is generated by a laser-induced optical breakdown in the cornea with ultra-short laser pulses in the near-infrared range. Compared to standard procedures such as photorefractive keratectomy and laser in-situ keratomileusis with the excimer laser, where the risk potential for the eye is low due to the complete absorption of ultraviolet irradiation from corneal tissue, only a certain amount of the pulse energy is deposited in the cornea during the fs-LASIK process. The remaining energy propagates through the eye and interacts with the retina and the strong absorbing tissue layers behind. The objective of the presented study was to determine and compare the retina damage thresholds during the fs-LASIK process simulated with two various laser systems in the CW- and fs-regime.

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

Bierbach, Jana; Yeung, Mark; Eckner, Erich

Surface high-harmonic generation in the relativistic regime is demonstrated as a source of extreme ultra-violet (XUV) pulses with extended operation time. Relativistic high-harmonic generation is driven by a frequency-doubled high-power Ti:Sapphire laser focused to a peak intensity of 3·1019 W/cm2 onto spooling tapes. We demonstrate continuous operation over up to one hour runtime at a repetition rate of 1 Hz. Harmonic spectra ranging from 20 eV to 70 eV (62 nm to 18 nm) were consecutively recorded by an XUV spectrometer. An average XUV pulse energy in the µJ range is measured. With the presented setup, relativistic surface high-harmonic generationmore » becomes a powerful source of coherent XUV pulses that might enable applications in, e.g. attosecond laser physics and the seeding of free-electron lasers, when the laser issues causing 80-% pulse energy fluctuations are overcome.« less

A small size 1-3 atm pulsed CO2 laser with series-connected spark gaps ultraviolet preionization.

PubMed

Silakhori, K; Jelvani, S; Ghanavati, F; Sajad, B; Talebi, M; Sadr, M R

2014-01-01

A small size pulsed CO2 laser with rounded edge flat profiled electrodes and variable gas pressure in 1-3 atm range has been constructed and characterized. The perionization system consists of a pair of 16 series-connected spark gaps located along either side of the main electrodes by which, the number of required preionization capacitors is reduced to 4. Sharpening of the main discharge has been performed using a 300 pF peaking capacitor. A maximum energy of 160 mJ/pulse was obtained for CO2:N2:He≡1:1:8 gas mixture and 33 kV discharge voltage. By increasing the laser gas pressure in 1-3 atm range, the duration of spike and tail parts of the laser pulses have been reduced from 110 ns and 4 μs to 37 ns and 1 μs, respectively.

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

Shaw, B. H.; Applied Science and Technology, University of California, Berkeley, California 94720; Tilborg, J. van

Solid-based surface high-harmonic generation from a tape is experimentally studied. By operating at mildly relativistic normalized laser strengths a{sub 0}≲0.2, harmonics up to the 17th order are efficiently produced in the coherent wake emission (CWE) regime. CWE pulse properties, such as divergence, energy, conversion efficiency, and spectrum, are investigated for various tape materials and drive laser conditions. A clear correlation between surface roughness and harmonic beam divergence is found. At the measured pulse properties for the 15th harmonic (conversion efficiency ∼6.5×10{sup −7}, divergence ∼7−15 mrad), the 100-mJ-level drive laser produces several MWs of extreme ultra-violet pulses. The spooling tape configurationmore » enables multi-Hz operation over thousands of shots, making this source attractive as a seed to the few-Hz laser-plasma-accelerator-driven free-electron laser (FEL). Models indicate that these CWE pulses with MW level powers are sufficient for seed-induced bunching and FEL gain.« less

Quantitative analysis of vacuum-ultraviolet radiation from nanosecond laser-zinc interaction

NASA Astrophysics Data System (ADS)

Parchamy, Homaira; Szilagyi, John; Masnavi, Majid; Richardson, Martin

2018-07-01

The paper reports measurements of the vacuum-ultraviolet spectral irradiances of a flat zinc target over a wavelength region of 124-164 nm generated by 10 and 60 ns duration low-intensities, 5 ×109 - 3 ×1010 W cm-2, 1.06 μm wavelength laser pulses. Maximum radiation conversion efficiencies of 2.5%/2πsr and 0.8%/2πsr were measured for 60 and 10 ns laser pulses at the intensities of 5 ×109 and 1.4 ×1010 W cm-2, respectively. Atomic structure calculations using a relativistic configuration-interaction, flexible atomic code and a developed non-local thermodynamic equilibrium population kinetics model in comparison to the experimental spectra detected by the Seya-Namioka type monochromator reveal the strong broadband experimental emission originates mainly from 3d94p-3d94s, 3d94d-3d94p and 3d84p-3d84s, 3d84d-3d84p unresolved-transition arrays of double and triple ionized zinc, respectively. Two-dimensional radiation-hydrodynamics code is used to investigate time-space plasma evolution and spectral radiation of a 10 ns full-width-at-half-maximum Gaussian laser pulse-zinc interaction.

An optical parametric chirped-pulse amplifier for seeding high repetition rate free-electron lasers

DOE PAGES

Höppner, H.; Hage, A.; Tanikawa, T.; ...

2015-05-15

High repetition rate free-electron lasers (FEL), producing highly intense extreme ultraviolet and x-ray pulses, require new high power tunable femtosecond lasers for FEL seeding and FEL pump-probe experiments. A tunable, 112 W (burst mode) optical parametric chirped-pulse amplifier (OPCPA) is demonstrated with center frequencies ranging from 720–900 nm, pulse energies up to 1.12 mJ and a pulse duration of 30 fs at a repetition rate of 100 kHz. Since the power scalability of this OPCPA is limited by the OPCPA-pump amplifier, we also demonstrate a 6.7–13.7 kW (burst mode) thin-disk OPCPA-pump amplifier, increasing the possible OPCPA output power to manymore » hundreds of watts. Furthermore, third and fourth harmonic generation experiments are performed and the results are used to simulate a seeded FEL with high-gain harmonic generation.« less

Pulse Duration of Seeded Free-Electron Lasers

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

Finetti, Paola; Hoppner, Hauke; Allaria, Enrico

The pulse duration, and, more generally, the temporal intensity profile of free-electron laser (FEL) pulses, is of utmost importance for exploring the new perspectives offered by FELs; it is a nontrivial experimental parameter that needs to be characterized. We measured the pulse shape of an extreme ultraviolet externally seeded FEL operating in high-gain harmonic generation mode. Two different methods based on the cross-correlation of the FEL pulses with an external optical laser were used. The two methods, one capable of single-shot performance, may both be implemented as online diagnostics in FEL facilities. The measurements were carried out at the seededmore » FEL facility FERMI. The FEL temporal pulse characteristics were measured and studied in a range of FEL wavelengths and machine settings, and they were compared to the predictions of a theoretical model. Finally, the measurements allowed a direct observation of the pulse lengthening and splitting at saturation, in agreement with the proposed theory.« less

Pulse Duration of Seeded Free-Electron Lasers

DOE PAGES

Finetti, Paola; Hoppner, Hauke; Allaria, Enrico; ...

2017-06-16

The pulse duration, and, more generally, the temporal intensity profile of free-electron laser (FEL) pulses, is of utmost importance for exploring the new perspectives offered by FELs; it is a nontrivial experimental parameter that needs to be characterized. We measured the pulse shape of an extreme ultraviolet externally seeded FEL operating in high-gain harmonic generation mode. Two different methods based on the cross-correlation of the FEL pulses with an external optical laser were used. The two methods, one capable of single-shot performance, may both be implemented as online diagnostics in FEL facilities. The measurements were carried out at the seededmore » FEL facility FERMI. The FEL temporal pulse characteristics were measured and studied in a range of FEL wavelengths and machine settings, and they were compared to the predictions of a theoretical model. Finally, the measurements allowed a direct observation of the pulse lengthening and splitting at saturation, in agreement with the proposed theory.« less

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

Three-photon absorption and nonlinear refraction of BaMgF4 in the ultraviolet region.

PubMed

Ma, Yanzhi; Chen, Junjie; Zheng, Yuanlin; Chen, Xianfeng

2012-08-01

The nonlinear refraction and nonlinear absorption phenomena are investigated in BaMgF(4) single crystal using the Z-scan technique in the ultraviolet region with a pulsed laser at 400 nm with 1 ps pulse duration. The remarkable nonlinear absorption behavior is identified to be three-photon absorption under the experimental conditions. In addition, both nonlinear refraction and nonlinear absorption have relatively large values and possess small anisotropy along three different crystallographic axes. The large values of nonlinear refractive index are demonstrated through the self-phase modulation effect.

Investigation of laser dynamics, modulation and control by means of intra-cavity time varying perturbation

NASA Technical Reports Server (NTRS)

Harris, S. E.

1974-01-01

Projects aimed at the generation of tunable visible, infrared, and ultraviolet light, and on the control of this light by means of novel mode-locking and modulation techniques are discussed. During this period the following projects have been active: (1) studies of transient mode-locking of the Nd:YAG laser and the application of short optical pulses; (2) experimental investigations of the Na-Xe excimer laser system; (3) further development of techniques for vacuum ultraviolet holography; and (4) theoretical and initial experimental studies of a new device which should prove very useful for both infrared up-conversion and generation of tunable UV radiation - a two-photon resonantly pumped frequency converter.

DNA Damage in Bone Marrow Cells Induced by Femtosecond and Nanosecond Ultraviolet Laser Pulses.

PubMed

Morkunas, Vaidotas; Gabryte, Egle; Vengris, Mikas; Danielius, Romualdas; Danieliene, Egle; Ruksenas, Osvaldas

2015-12-01

The purpose of this study was to investigate the possible genotoxic impact of new generation 205 nm femtosecond solid-state laser irradiation on the DNA of murine bone marrow cells in vitro, and to compare the DNA damage caused by both femtosecond and nanosecond UV laser pulses. Recent experiments of corneal stromal ablation in vitro and in vivo applying femtosecond UV pulses showed results comparable with or superior to those obtained using nanosecond UV lasers. However, the possible genotoxic effect of ultrashort laser pulses was not investigated. Mouse bone marrow cells were exposed to different doses of 205 nm femtosecond, 213 and 266 nm nanosecond lasers, and 254 nm UV lamp irradiation. The comet assay was used for the evaluation of DNA damage. All types of irradiation demonstrated intensity-dependent genotoxic impact. The DNA damage induced depended mainly upon wavelength rather than on other parameters such as pulse duration, repetition rate, or beam delivery to a target. Both 205 nm femtosecond and clinically applied 213 nm nanosecond lasers' pulses induced a comparable amount of DNA breakage in cells exposed to the same irradiation dose. To further evaluate the suitability of femtosecond UV laser sources for microsurgery, a separate investigation of the genotoxic and mutagenic effects on corneal cells in vitro and, particularly, in vivo is needed.

The DUV Stability of Superlattice-Doped CMOS Detector Arrays

NASA Technical Reports Server (NTRS)

Hoenk, M. E.; Carver, A. G.; Jones, T.; Dickie, M.; Cheng, P.; Greer, H. F.; Nikzad, S.; Sgro, J.; Tsur, S.

2013-01-01

JPL and Alacron have recently developed a high performance, DUV camera with a superlattice doped CMOS imaging detector. Supperlattice doped detectors achieve nearly 100% internal quantum efficiency in the deep and far ultraviolet, and a single layer, Al2O3 antireflection coating enables 64% external quantum efficiency at 263nm. In lifetime tests performed at Applied Materials using 263 nm pulsed, solid state and 193 nm pulsed excimer laser, the quantum efficiency and dark current of the JPL/Alacron camera remained stable to better than 1% precision during long-term exposure to several billion laser pulses, with no measurable degradation, no blooming and no image memory at 1000 fps.

Time-resolved photoelectron spectroscopy of polyatomic molecules using 42-nm vacuum ultraviolet laser based on high harmonics generation

NASA Astrophysics Data System (ADS)

Nishitani, Junichi; West, Christopher W.; Higashimura, Chika; Suzuki, Toshinori

2017-09-01

Time-resolved photoelectron spectroscopy (TRPES) of gaseous polyatomic molecules using 266-nm (4.7 eV) pump and 42-nm (29.5 eV) probe pulses is presented. A 1-kHz Ti:sapphire laser with a 35 fs pulse duration is employed to generate high harmonics in Kr gas, and the 19th harmonic (42-nm) was selected using two SiC/Mg mirrors. Clear observation of the ultrafast electronic dephasing in pyrazine and photoisomerization of 1,3-cyclohexadiene demonstrates the feasibility of TRPES with the UV pump and VUV probe pulses under weak excitation conditions in the perturbation regime.

Investigation of laser dynamics, modulation and control by means of intra-cavity time varying perturbation

NASA Technical Reports Server (NTRS)

Harris, S. E.; Siegman, A. E.; Kuizenga, D. J.; Kung, A. H.; Young, J. F.; Bekkers, G. W.; Bloom, D. M.; Newton, J. H.; Phillion, D. W.

1975-01-01

The generation of tunable visible, infrared, and ultraviolet light is examined, along with the control of this light by means of novel mode-locking and modulation techniques. Transient mode-locking of the Nd:YAG laser and generation of short tunable pulses in the visible and the alkali metal inert gas excimer laser systems were investigated. Techniques for frequency conversion of high power and high energy laser radiation are discussed, along with high average power blue and UV laser light sources.

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

Absorption and emission of single attosecond light pulses in an autoionizing gaseous medium dressed by a time-delayed control field

NASA Astrophysics Data System (ADS)

Chu, Wei-Chun; Lin, C. D.

2013-01-01

An extreme ultraviolet (EUV) single attosecond pulse passing through a laser-dressed dense gas is studied theoretically. The weak EUV pulse pumps the helium gas from the ground state to the 2s2p(1P) autoionizing state, which is coupled to the 2s2(1S) autoionizing state by a femtosecond infrared laser with the intensity in the order of 1012 W/cm2. The simulation shows how the transient absorption and emission of the EUV are modified by the coupling laser. A simple analytical expression for the atomic response derived for δ-function pulses reveals the strong modification of the Fano lineshape in the spectra, where these features are quite universal and remain valid for realistic pulse conditions. We further account for the propagation of pulses in the medium and show that the EUV signal at the atomic resonance can be enhanced in the gaseous medium by more than 50% for specifically adjusted laser parameters, and that this enhancement persists as the EUV propagates in the gaseous medium. Our result demonstrates the high-level control of nonlinear optical effects that are achievable with attosecond pulses.

Control of Early Flame Kernel Growth by Multi-Wavelength Laser Pulses for Enhanced Ignition

DOE PAGES

Dumitrache, Ciprian; VanOsdol, Rachel; Limbach, Christopher M.; ...

2017-08-31

The present contribution examines the impact of plasma dynamics and plasma-driven fluid dynamics on the flame growth of laser ignited mixtures and shows that a new dual-pulse scheme can be used to control the kernel formation process in ways that extend the lean ignition limit. We do this by performing a comparative study between (conventional) single-pulse laser ignition (λ = 1064 nm) and a novel dual-pulse method based on combining an ultraviolet (UV) pre-ionization pulse (λ = 266 nm) with an overlapped near-infrared (NIR) energy addition pulse (λ = 1064 nm). We employ OH* chemiluminescence to visualize the evolution ofmore » the early flame kernel. For single-pulse laser ignition at lean conditions, the flame kernel separates through third lobe detachment, corresponding to high strain rates that extinguish the flame. In this work, we investigate the capabilities of the dual-pulse to control the plasma-driven fluid dynamics by adjusting the axial offset of the two focal points. In particular, we find there exists a beam waist offset whereby the resulting vorticity suppresses formation of the third lobe, consequently reducing flame stretch. With this approach, we demonstrate that the dual-pulse method enables reduced flame speeds (at early times), an extended lean limit, increased combustion efficiency, and decreased laser energy requirements.« less

Control of Early Flame Kernel Growth by Multi-Wavelength Laser Pulses for Enhanced Ignition

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

Dumitrache, Ciprian; VanOsdol, Rachel; Limbach, Christopher M.

The present contribution examines the impact of plasma dynamics and plasma-driven fluid dynamics on the flame growth of laser ignited mixtures and shows that a new dual-pulse scheme can be used to control the kernel formation process in ways that extend the lean ignition limit. We do this by performing a comparative study between (conventional) single-pulse laser ignition (λ = 1064 nm) and a novel dual-pulse method based on combining an ultraviolet (UV) pre-ionization pulse (λ = 266 nm) with an overlapped near-infrared (NIR) energy addition pulse (λ = 1064 nm). We employ OH* chemiluminescence to visualize the evolution ofmore » the early flame kernel. For single-pulse laser ignition at lean conditions, the flame kernel separates through third lobe detachment, corresponding to high strain rates that extinguish the flame. In this work, we investigate the capabilities of the dual-pulse to control the plasma-driven fluid dynamics by adjusting the axial offset of the two focal points. In particular, we find there exists a beam waist offset whereby the resulting vorticity suppresses formation of the third lobe, consequently reducing flame stretch. With this approach, we demonstrate that the dual-pulse method enables reduced flame speeds (at early times), an extended lean limit, increased combustion efficiency, and decreased laser energy requirements.« less

Control of Early Flame Kernel Growth by Multi-Wavelength Laser Pulses for Enhanced Ignition.

PubMed

Dumitrache, Ciprian; VanOsdol, Rachel; Limbach, Christopher M; Yalin, Azer P

2017-08-31

The present contribution examines the impact of plasma dynamics and plasma-driven fluid dynamics on the flame growth of laser ignited mixtures and shows that a new dual-pulse scheme can be used to control the kernel formation process in ways that extend the lean ignition limit. We perform a comparative study between (conventional) single-pulse laser ignition (λ = 1064 nm) and a novel dual-pulse method based on combining an ultraviolet (UV) pre-ionization pulse (λ = 266 nm) with an overlapped near-infrared (NIR) energy addition pulse (λ = 1064 nm). We employ OH* chemiluminescence to visualize the evolution of the early flame kernel. For single-pulse laser ignition at lean conditions, the flame kernel separates through third lobe detachment, corresponding to high strain rates that extinguish the flame. In this work, we investigate the capabilities of the dual-pulse to control the plasma-driven fluid dynamics by adjusting the axial offset of the two focal points. In particular, we find there exists a beam waist offset whereby the resulting vorticity suppresses formation of the third lobe, consequently reducing flame stretch. With this approach, we demonstrate that the dual-pulse method enables reduced flame speeds (at early times), an extended lean limit, increased combustion efficiency, and decreased laser energy requirements.

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.

European Scientific Notes. Volume 37, Number 9.

DTIC Science & Technology

1983-09-30

themes: Reactions of the Ionosphere and Neutral Atmosphere to Magnetospheric Activity, and Pulsations : Correlated Observations from Satellites and the...periods of hundreds of nanosec- heating pulse at 532-nm wavelength was onds. used. Raman data were obtained from J. Bok (l’Ecole Normale Sup4rieuse...both the heating pulse and from a 355-nm France) Bok thce Norato ofpaeser weak ultraviolet probe pulse. The France) viewed the action of laser latter

Pulsed laser ablation of dental calculus in the near ultraviolet.

PubMed

Schoenly, Joshua E; Seka, Wolf; Rechmann, Peter

2014-02-01

Pulsed lasers emitting wavelengths near 400 nm can selectively ablate dental calculus without damaging underlying and surrounding sound dental hard tissue. Our results indicate that calculus ablation at this wavelength relies on the absorption of porphyrins endogenous to oral bacteria commonly found in calculus. Sub- and supragingival calculus on extracted human teeth, irradiated with 400-nm, 60-ns laser pulses at ≤8  J/cm2, exhibits a photobleached surface layer. Blue-light microscopy indicates this layer highly scatters 400-nm photons, whereas fluorescence spectroscopy indicates that bacterial porphyrins are permanently photobleached. A modified blow-off model for ablation is proposed that is based upon these observations and also reproduces our calculus ablation rates measured from laser profilometry. Tissue scattering and a stratified layering of absorbers within the calculus medium explain the gradual decrease in ablation rate from successive pulses. Depending on the calculus thickness, ablation stalling may occur at <5  J/cm2 but has not been observed above this fluence.

Long-term operation of surface high-harmonic generation from relativistic oscillating mirrors using a spooling tape

DOE PAGES

Bierbach, Jana; Yeung, Mark; Eckner, Erich; ...

2015-05-01

Surface high-harmonic generation in the relativistic regime is demonstrated as a source of extreme ultra-violet (XUV) pulses with extended operation time. Relativistic high-harmonic generation is driven by a frequency-doubled high-power Ti:Sapphire laser focused to a peak intensity of 3·1019 W/cm2 onto spooling tapes. We demonstrate continuous operation over up to one hour runtime at a repetition rate of 1 Hz. Harmonic spectra ranging from 20 eV to 70 eV (62 nm to 18 nm) were consecutively recorded by an XUV spectrometer. An average XUV pulse energy in the µJ range is measured. With the presented setup, relativistic surface high-harmonic generationmore » becomes a powerful source of coherent XUV pulses that might enable applications in, e.g. attosecond laser physics and the seeding of free-electron lasers, when the laser issues causing 80-% pulse energy fluctuations are overcome.« less

Solid-state laser source of narrowband ultraviolet B light for skin disease care

NASA Astrophysics Data System (ADS)

Tarasov, Aleksandr A.; Chu, Hong

2013-03-01

We report about the development of all-solid-state laser source of narrowband UV-B light for medical applications. The device is based on a gain-switched Ti: Sapphire laser with volume Bragg grating, pumped at 532 nm and operating at 931.8 nm, followed by a third harmonic generator and a fiber optic beam homogenizer. The maximum available pulse energy exceeded 5 mJ at 310.6 nm, with a pulse repetition rates of 50 Hz. The output characteristics satisfy the medical requirements for psoriasis and vitiligo treatment. A new optical scheme for third harmonic generation enhancement at moderate levels of input intensities is proposed and investigated. As a result, 40% harmonic efficiency was obtained, when input pulse power was only 300 kW.

Emission spectra of photoionized plasmas induced by intense EUV pulses: Experimental and theoretical investigations

NASA Astrophysics Data System (ADS)

Saber, Ismail; Bartnik, Andrzej; Skrzeczanowski, Wojciech; Wachulak, Przemysław; Jarocki, Roman; Fiedorowicz, Henryk

2017-03-01

Experimental measurements and numerical modeling of emission spectra in photoionized plasma in the ultraviolet and visible light (UV/Vis) range for noble gases have been investigated. The photoionized plasmas were created using laser-produced plasma (LPP) extreme ultraviolet (EUV) source. The source was based on a gas puff target; irradiated with 10ns/10J/10Hz Nd:YAG laser. The EUV radiation pulses were collected and focused using grazing incidence multifoil EUV collector. The laser pulses were focused on a gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Irradiation of gases resulted in a formation of low temperature photoionized plasmas emitting radiation in the UV/Vis spectral range. Atomic photoionized plasmas produced this way consisted of atomic and ionic with various ionization states. The most dominated observed spectral lines originated from radiative transitions in singly charged ions. To assist in a theoretical interpretation of the measured spectra, an atomic code based on Cowan's programs and a collisional-radiative PrismSPECT code have been used to calculate the theoretical spectra. A comparison of the calculated spectral lines with experimentally obtained results is presented. Electron temperature in plasma is estimated using the Boltzmann plot method, by an assumption that a local thermodynamic equilibrium (LTE) condition in the plasma is validated in the first few ionization states. A brief discussion for the measured and computed spectra is given.

Biomodulation of light on cells in laser surgery

NASA Astrophysics Data System (ADS)

Liu, Timon C.; Li, Yan; Duan, Rui; Cai, Xiongwei

2002-04-01

In laser surgery, it has been observed pulsed 532-nm laser can avoid postoperative purpura, but pulsed 585-nm, 595-nm or 600-nm lasers nonetheless cause purpura when they were used to treat port-wine stains; the XeCl excimer laser (308 nm) can safely and effectively clear psoriasis; both XeCl excimer laser and Ho:YAG laser were used in coronary interventions, but only former was approved by the FDA; open channels after ultraviolet (UV) laser treatment and closed channels with infrared (IR) lasers for transmyocardial laser revascularization; and so on. In this paper, the biological information model of low intensity laser (BIML) is extended to include UVA biomodulation and is used to understand these phenomena. Although the central intensity of the laser beam is so intense that it destroys the tissue, the edge intensity is so low that it can induce biomodulation. Our investigation showed that biomodulation of light on cells might play an important role in the long-term effects of laser surgery.

Interpreting atom probe data from chromium oxide scales.

PubMed

La Fontaine, Alexandre; Gault, Baptiste; Breen, Andrew; Stephenson, Leigh; Ceguerra, Anna V; Yang, Limei; Nguyen, Thuan Dinh; Zhang, Jianqiang; Young, David J; Cairney, Julie M

2015-12-01

Picosecond-pulsed ultraviolet-laser (UV-355 nm) assisted atom probe tomography (APT) was used to analyze protective, thermally grown chromium oxides formed on stainless steel. The influence of analysis parameters on the thermal tail observed in the mass spectra and the chemical composition is investigated. A new parameter termed "laser sensitivity factor" is introduced in order to quantify the effect of laser energy on the extent of the thermal tail. This parameter is used to compare the effect of increasing laser energy on thermal tails in chromia and chromite samples. Also explored is the effect of increasing laser energy on the measured oxygen content and the effect of specimen base temperature and laser pulse frequency on the mass spectrum. Finally, we report a preliminary analysis of molecular ion dissociations in chromia. Copyright © 2015 Elsevier B.V. All rights reserved.

Chip design for thin-film deep ultraviolet LEDs fabricated by laser lift-off of the sapphire substrate

NASA Astrophysics Data System (ADS)

Cho, H. K.; Krüger, O.; Külberg, A.; Rass, J.; Zeimer, U.; Kolbe, T.; Knauer, A.; Einfeldt, S.; Weyers, M.; Kneissl, M.

2017-12-01

We report on a chip design which allows the laser lift-off (LLO) of the sapphire substrate sustaining the epitaxial film of flip-chip mounted deep ultraviolet light emitting diodes. A nanosecond pulsed excimer laser with a wavelength of 248 nm was used for the LLO. A mechanically stable chip design was found to be the key to prevent crack formation in the epitaxial layers and material chipping during the LLO process. Stabilization was achieved by introducing a Ti/Au leveling layer that mechanically supports the fragile epitaxial film. The electrical and optical characterization of devices before and after the LLO process shows that the device performance did not degrade by the LLO.

Sub-50-as isolated extreme ultraviolet continua generated by 1.6-cycle near-infrared pulse combined with double optical gating scheme

NASA Astrophysics Data System (ADS)

Oguri, Katsuya; Mashiko, Hiroki; Ogawa, Tatsuya; Hanada, Yasutaka; Nakano, Hidetoshi; Gotoh, Hideki

2018-04-01

We demonstrate the generation of ultrabroad bandwidth attosecond continua extending to sub-50-as duration in the extreme ultraviolet (EUV) region based on a 1.6-cycle Ti:sapphire laser pulse. The combination of the amplitude gating scheme with a sub-two-cycle driver pulse and the double optical gating scheme achieves the continuum generation with a bandwidth of 70 eV at the full width at half maximum near the peak photon energy of 140 eV, which supports a Fourier-transform-limited pulse duration as short as 32 as. The carrier-envelope-phase (CEP) dependence of the attosecond continua shows a single-peak structure originating from the half-cycle cut-off at appropriate CEP values, which strongly indicates the generation of a single burst of an isolated attosecond pulse. Our approach suggests a possibility for isolated sub-50-as pulse generation in the EUV region by compensating for the intrinsic attosecond chirp with a Zr filter.

Light and Laser Modalities in the Treatment of Cutaneous Sarcoidosis: A Systematic Review.

PubMed

Lima, Ana Luiza; Goetze, Steven; Illing, Tanja; Elsner, Peter

2018-04-27

Sarcoidosis is a systemic non-caseating granulomatous disease of unknown aetiology. Cutaneous manifestations are present in approximately 10-30% of the patients with the systemic form. Therapy is indicated in case of disabling symptoms, organ dysfunction or cosmetically distressing manifestation. Despite different therapeutic possibilities, cutaneous sarcoidosis remains exceptionally difficult to treat. Light and laser therapy may be a promising alternative. In this systematic review, we summarised the available treatments according to the literature concerning light and laser therapy for cutaneous sarcoidosis. Publications written in English and German, published between January 1990 and July 2016 in the database PubMed, MEDLINE, Embase, and Scopus were analysed. Light therapy with intense pulsed light, photodynamic therapy, and ultraviolet A light therapy, as well as laser therapy with pulsed dye laser, YAG laser, and Q-switched ruby laser were described. The results are based on individual case reports and small case series. Randomised controlled studies are lacking.

Generation of strongly coupled plasmas by high power excimer laser

NASA Astrophysics Data System (ADS)

Zhu, Yongxiang; Liu, Jingru; Zhang, Yongsheng; Hu, Yun; Zhang, Jiyan; Zheng, Zhijian; Ye, Xisheng

2013-05-01

(ultraviolet). To generate strongly coupled plasmas (SCP) by high power excimer laser, an Au-CH-Al-CH target is used to make the Al sample reach the state of SCP, in which the Au layer transforms laser energy to X-ray that heating the sample by volume and the CH layers provides necessary constraints. With aid of the MULTI-1D code, we calculate the state of the Al sample and its relationship with peak intensity, width and wavelength of laser pulses. The calculated results suggest that an excimer laser with peak intensity of the magnitude of 1013W/cm2 and pulse width being 5ns - 10ns is suitable to generate SCP with the temperature being tens of eV and the density of electron being of the order of 1022/cm-3. Lasers with shorter wavelength, such as KrF laser, are preferable.

Beyond the single-atom response in absorption line shapes: probing a dense, laser-dressed helium gas with attosecond pulse trains.

PubMed

Liao, Chen-Ting; Sandhu, Arvinder; Camp, Seth; Schafer, Kenneth J; Gaarde, Mette B

2015-04-10

We investigate the absorption line shapes of laser-dressed atoms beyond the single-atom response, by using extreme ultraviolet (XUV) attosecond pulse trains to probe an optically thick helium target under the influence of a strong infrared (IR) field. We study the interplay between the IR-induced phase shift of the microscopic time-dependent dipole moment and the resonant-propagation-induced reshaping of the macroscopic XUV pulse. Our experimental and theoretical results show that as the optical depth increases, this interplay leads initially to a broadening of the IR-modified line shape, and subsequently, to the appearance of new, narrow features in the absorption line.

Selective ablation of dental calculus with a frequency-doubled Alexandrite laser

NASA Astrophysics Data System (ADS)

Rechmann, Peter; Hennig, Thomas

1996-01-01

The aim of the study was the selective removal of dental calculus by means of pulsed lasers. In a first approach the optical characteristics of subgingival calculus were calculated using fluorescence emission spectroscopy (excitation laser: N2-laser, wavelength 337 nm, pulse duration 4 ns). Subgingival calculus seems to absorb highly in the ultraviolet spectral region up to 420 nm. According to these measurements a frequency doubled Alexandrite-laser (wavelength 377 nm, pulse duration 100 ns, repetition rate 110 Hz) was used to irradiate calculus located on enamel, at the cementum enamel junction and on the root surface (located on dentin or on cementum). Irradiation was performed perpendicular to the root surface with a laser fluence of 1 Jcm-2. During the irradiation procedure an effective water cooling-system was engaged. Histological investigations were done on undecalcified sections. As a result, engaging low fluences allows a fast and strictly selective removal of subgingival calculus. Even more the investigations revealed that supragingival calculus can be removed in a strictly selective manner engaging a frequency doubled Alexandrite-laser. No adverse side effects to the surrounding tissues could be found.

Comparative study of pulsed laser cleaning applied to weathered marble surfaces

NASA Astrophysics Data System (ADS)

Ortiz, P.; Antúnez, V.; Ortiz, R.; Martín, J. M.; Gómez, M. A.; Hortal, A. R.; Martínez-Haya, B.

2013-10-01

The removal of unwanted matter from surface stones is a demanding task in the conservation of cultural heritage. This paper investigates the effectiveness of near-infrared (IR) and ultraviolet (UV) laser pulses for the cleaning of surface deposits, iron oxide stains and different types of graffiti (black, red and green sprays and markers, and black cutting-edge ink) on dolomitic white marble. The performance of the laser techniques is compared to common cleaning methods on the same samples, namely pressurized water and chemical treatments. The degree of cleaning achieved with each technique is assessed by means of colorimetric measurements and X-ray microfluorescence. Eventual morphological changes induced on the marble substrate are monitored with optical and electronic microscopy. It is found that UV pulsed laser ablation at 266 nm manages to clean all the stains except the cutting-edge ink, although some degree of surface erosion is produced. The IR laser pulses at 1064 nm can remove surface deposits and black spray acceptably, but a yellowing is observed on the stone surface after treatment. An economic evaluation shows that pulsed laser cleaning techniques are advantageous for the rapid cleaning of small or inaccessible surface areas, although their extensive application becomes expensive due to the long operating times required.

Extreme ultraviolet emission and confinement of tin plasmas in the presence of a magnetic field

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

Roy, Amitava, E-mail: roy@fzu.cz, E-mail: aroy@barc.gov.in; HiLASE Project, Department of Diode-pumped Lasers, Institute of Physics of the ASCR, Na Slovance 2, 18221 Prague; Murtaza Hassan, Syed

2014-05-15

We investigated the role of a guiding magnetic field on extreme ultraviolet (EUV) and ion emission from a laser produced Sn plasma for various laser pulse duration and intensity. For producing plasmas, planar slabs of pure Sn were irradiated with 1064 nm, Nd:YAG laser pulses with varying pulse duration (5–15 ns) and intensity. A magnetic trap was fabricated with the use of two neodymium permanent magnets which provided a magnetic field strength ∼0.5 T along the plume expansion direction. Our results indicate that the EUV conversion efficiency do not depend significantly on applied axial magnetic field. Faraday Cup ion analysis of Sn plasmamore » show that the ion flux reduces by a factor of ∼5 with the application of an axial magnetic field. It was found that the plasma plume expand in the lateral direction with peak velocity measured to be ∼1.2 cm/μs and reduced to ∼0.75 cm/μs with the application of an axial magnetic field. The plume expansion features recorded using fast photography in the presence and absence of 0.5 T axial magnetic field are simulated using particle-in-cell code. Our simulation results qualitatively predict the plasma behavior.« less

Simultaneous operation of two soft x-ray free-electron lasers driven by one linear accelerator

NASA Astrophysics Data System (ADS)

Faatz, B.; Plönjes, E.; Ackermann, S.; Agababyan, A.; Asgekar, V.; Ayvazyan, V.; Baark, S.; Baboi, N.; Balandin, V.; von Bargen, N.; Bican, Y.; Bilani, O.; Bödewadt, J.; Böhnert, M.; Böspflug, R.; Bonfigt, S.; Bolz, H.; Borges, F.; Borkenhagen, O.; Brachmanski, M.; Braune, M.; Brinkmann, A.; Brovko, O.; Bruns, T.; Castro, P.; Chen, J.; Czwalinna, M. K.; Damker, H.; Decking, W.; Degenhardt, M.; Delfs, A.; Delfs, T.; Deng, H.; Dressel, M.; Duhme, H.-T.; Düsterer, S.; Eckoldt, H.; Eislage, A.; Felber, M.; Feldhaus, J.; Gessler, P.; Gibau, M.; Golubeva, N.; Golz, T.; Gonschior, J.; Grebentsov, A.; Grecki, M.; Grün, C.; Grunewald, S.; Hacker, K.; Hänisch, L.; Hage, A.; Hans, T.; Hass, E.; Hauberg, A.; Hensler, O.; Hesse, M.; Heuck, K.; Hidvegi, A.; Holz, M.; Honkavaara, K.; Höppner, H.; Ignatenko, A.; Jäger, J.; Jastrow, U.; Kammering, R.; Karstensen, S.; Kaukher, A.; Kay, H.; Keil, B.; Klose, K.; Kocharyan, V.; Köpke, M.; Körfer, M.; Kook, W.; Krause, B.; Krebs, O.; Kreis, S.; Krivan, F.; Kuhlmann, J.; Kuhlmann, M.; Kube, G.; Laarmann, T.; Lechner, C.; Lederer, S.; Leuschner, A.; Liebertz, D.; Liebing, J.; Liedtke, A.; Lilje, L.; Limberg, T.; Lipka, D.; Liu, B.; Lorbeer, B.; Ludwig, K.; Mahn, H.; Marinkovic, G.; Martens, C.; Marutzky, F.; Maslocv, M.; Meissner, D.; Mildner, N.; Miltchev, V.; Molnar, S.; Mross, D.; Müller, F.; Neumann, R.; Neumann, P.; Nölle, D.; Obier, F.; Pelzer, M.; Peters, H.-B.; Petersen, K.; Petrosyan, A.; Petrosyan, G.; Petrosyan, L.; Petrosyan, V.; Petrov, A.; Pfeiffer, S.; Piotrowski, A.; Pisarov, Z.; Plath, T.; Pototzki, P.; Prandolini, M. J.; Prenting, J.; Priebe, G.; Racky, B.; Ramm, T.; Rehlich, K.; Riedel, R.; Roggli, M.; Röhling, M.; Rönsch-Schulenburg, J.; Rossbach, J.; Rybnikov, V.; Schäfer, J.; Schaffran, J.; Schlarb, H.; Schlesselmann, G.; Schlösser, M.; Schmid, P.; Schmidt, C.; Schmidt-Föhre, F.; Schmitz, M.; Schneidmiller, E.; Schöps, A.; Scholz, M.; Schreiber, S.; Schütt, K.; Schütz, U.; Schulte-Schrepping, H.; Schulz, M.; Shabunov, A.; Smirnov, P.; Sombrowski, E.; Sorokin, A.; Sparr, B.; Spengler, J.; Staack, M.; Stadler, M.; Stechmann, C.; Steffen, B.; Stojanovic, N.; Sychev, V.; Syresin, E.; Tanikawa, T.; Tavella, F.; Tesch, N.; Tiedtke, K.; Tischer, M.; Treusch, R.; Tripathi, S.; Vagin, P.; Vetrov, P.; Vilcins, S.; Vogt, M.; de Zubiaurre Wagner, A.; Wamsat, T.; Weddig, H.; Weichert, G.; Weigelt, H.; Wentowski, N.; Wiebers, C.; Wilksen, T.; Willner, A.; Wittenburg, K.; Wohlenberg, T.; Wortmann, J.; Wurth, W.; Yurkov, M.; Zagorodnov, I.; Zemella, J.

2016-06-01

Extreme-ultraviolet to x-ray free-electron lasers (FELs) in operation for scientific applications are up to now single-user facilities. While most FELs generate around 100 photon pulses per second, FLASH at DESY can deliver almost two orders of magnitude more pulses in this time span due to its superconducting accelerator technology. This makes the facility a prime candidate to realize the next step in FELs—dividing the electron pulse trains into several FEL lines and delivering photon pulses to several users at the same time. Hence, FLASH has been extended with a second undulator line and self-amplified spontaneous emission (SASE) is demonstrated in both FELs simultaneously. FLASH can now deliver MHz pulse trains to two user experiments in parallel with individually selected photon beam characteristics. First results of the capabilities of this extension are shown with emphasis on independent variation of wavelength, repetition rate, and photon pulse length.

Control of electron excitation and localization in the dissociation of H2(+) and its isotopes using two sequential ultrashort laser pulses.

PubMed

He, Feng; Ruiz, Camilo; Becker, Andreas

2007-08-24

We study the control of dissociation of the hydrogen molecular ion and its isotopes exposed to two ultrashort laser pulses by solving the time-dependent Schrödinger equation. While the first ultraviolet pulse is used to excite the electron wave packet on the dissociative 2psigma{u} state, a second time-delayed near-infrared pulse steers the electron between the nuclei. Our results show that by adjusting the time delay between the pulses and the carrier-envelope phase of the near-infrared pulse, a high degree of control over the electron localization on one of the dissociating nuclei can be achieved (in about 85% of all fragmentation events). The results demonstrate that current (sub-)femtosecond technology can provide a control over both electron excitation and localization in the fragmentation of molecules.

Laser Pulse Width Dependence and Ionization Mechanism of Matrix-Assisted Laser Desorption/Ionization

NASA Astrophysics Data System (ADS)

Liang, Sheng-Ping; Lu, I.-Chung; Tsai, Shang-Ting; Chen, Jien-Lian; Lee, Yuan Tseh; Ni, Chi-Kung

2017-10-01

Ultraviolet laser pulses at 355 nm with variable pulse widths in the region from 170 ps to 1.5 ns were used to investigate the ionization mechanism of matrix-assisted laser desorption/ionization (MALDI) for matrices 2,5-dihydroxybenzoic acid (DHB), α-cyano-4-hydroxycinnamic acid (CHCA), and sinapinic acid (SA). The mass spectra of desorbed ions and the intensity and velocity distribution of desorbed neutrals were measured simultaneously for each laser shot. These quantities were found to be independent of the laser pulse width. A comparison of the experimental measurements and numerical simulations according to the multiphoton ionization, coupled photophysical and chemical dynamics (CPCD), and thermally induced proton transfer models showed that the predictions of thermally induced proton transfer model were in agreement with the experimental data, but those of the multiphoton ionization model were not. Moreover, the predictions of the CPCD model based on singlet-singlet energy pooling were inconsistent with the experimental data of CHCA and SA, but were consistent with the experimental data of DHB only when some parameters used in the model were adjusted to extreme values. [Figure not available: see fulltext.

Laser and optical system for laser assisted hydrogen ion beam stripping at SNS

DOE PAGES

Liu, Y.; Rakhman, A.; Menshov, A.; ...

2016-12-01

A high-efficiency laser assisted hydrogen ion (H-) beam stripping was recently successfully carried out in the Spallation Neutron Source (SNS) accelerator. The experiment was not only an important step toward foil-less H- stripping for charge exchange injection, it also set up a first example of using megawatt ultraviolet (UV) laser source in an operational high power proton accelerator facility. This study reports in detail the design, installation, and commissioning result of a macro-pulsed multi-megawatt UV laser system and laser beam transport line for the laser stripping experiment.

Laser and optical system for laser assisted hydrogen ion beam stripping at SNS

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

Liu, Y.; Rakhman, A.; Menshov, A.

A high-efficiency laser assisted hydrogen ion (H-) beam stripping was recently successfully carried out in the Spallation Neutron Source (SNS) accelerator. The experiment was not only an important step toward foil-less H- stripping for charge exchange injection, it also set up a first example of using megawatt ultraviolet (UV) laser source in an operational high power proton accelerator facility. This study reports in detail the design, installation, and commissioning result of a macro-pulsed multi-megawatt UV laser system and laser beam transport line for the laser stripping experiment.

Excimer laser ablation of the cornea

NASA Astrophysics Data System (ADS)

Pettit, George H.; Ediger, Marwood N.; Weiblinger, Richard P.

1995-03-01

Pulsed ultraviolet laser ablation is being extensively investigated clinically to reshape the optical surface of the eye and correct vision defects. Current knowledge of the laser/tissue interaction and the present state of the clinical evaluation are reviewed. In addition, the principal findings of internal Food and Drug Administration research are described in some detail, including a risk assessment of the laser-induced-fluorescence and measurement of the nonlinear optical properties of cornea during the intense UV irradiation. Finally, a survey is presented of the alternative laser technologies being explored for this ophthalmic application.

Ionization heating in rare-gas clusters under intense XUV laser pulses

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

Arbeiter, Mathias; Fennel, Thomas

The interaction of intense extreme ultraviolet (XUV) laser pulses ({lambda}=32 nm, I=10{sup 11}-10{sup 14} W/cm{sup 2}) with small rare-gas clusters (Ar{sub 147}) is studied by quasiclassical molecular dynamics simulations. Our analysis supports a very general picture of the charging and heating dynamics in finite samples under short-wavelength radiation that is of relevance for several applications of free-electron lasers. First, up to a certain photon flux, ionization proceeds as a series of direct photoemission events producing a jellium-like cluster potential and a characteristic plateau in the photoelectron spectrum as observed in Bostedt et al. [Phys. Rev. Lett. 100, 133401 (2008)]. Second,more » beyond the onset of photoelectron trapping, nanoplasma formation leads to evaporative electron emission with a characteristic thermal tail in the electron spectrum. A detailed analysis of this transition is presented. Third, in contrast to the behavior in the infrared or low vacuum ultraviolet range, the nanoplasma energy capture proceeds via ionization heating, i.e., inner photoionization of localized electrons, whereas collisional heating of conduction electrons is negligible up to high laser intensities. A direct consequence of the latter is a surprising evolution of the mean energy of emitted electrons as function of laser intensity.« less

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

Note: Enhancement of the extreme ultraviolet emission from a potassium plasma by dual laser irradiation

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

Higashiguchi, Takeshi, E-mail: higashi@cc.utsunomiya-u.ac.jp; Yamaguchi, Mami; Otsuka, Takamitsu

2014-09-15

Emission spectra from multiply charged potassium ions ranging from K{sup 3+} to K{sup 5+} have been obtained in the extreme ultraviolet (EUV) spectral region. A strong emission feature peaking around 38 nm, corresponding to a photon energy of 32.6 eV, is the dominant spectral feature at time-averaged electron temperatures in the range of 8−12 eV. The variation of this emission with laser intensity and the effects of pre-pulses on the relative conversion efficiency (CE) have been explored experimentally and indicate that an enhancement of about 30% in EUV CE is readily attainable.

Ultraviolet acousto-optic programmable dispersive filter laser pulse shaping in KDP.

PubMed

Coudreau, Sebastien; Kaplan, Daniel; Tournois, Pierre

2006-06-15

An acousto-optic programmable dispersive filter pulse shaper has been designed using KDP material for operation in the 200-500 nm wavelength range. With an acousto-optic interaction length of 72 mm, a spectral resolution of 0.15 nm has been measured to be consistent with theoretical predictions. Theory and experiments indicate that diffraction efficiencies up to 50% are expected in practical experimental conditions.

Extension of harmonic cutoff in a multicycle chirped pulse combined with a chirp-free pulse

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

Xu Junjie; Zeng Bin; Yu Yongli

2010-11-15

We demonstrate high-order harmonic generation in a wave form synthesized by a multicycle 800-nm chirped laser pulse and a chirp-free laser pulse. Compared with the case of using only a chirped pulse, both the harmonic cutoff and the extreme ultraviolet supercontinuum can be extended when a weak chirp-free pulse is combined with the chirped pulse. When chirp-free pulse intensity grows, the cutoff energy and bandwidth of the supercontinuum grow as well. It is found that the broad supercontinuum can be achieved for a driving pulse with long duration even though the driving pulse reaches 10 optical cycles. An isolated attosecondmore » pulse with duration of about 59 as is obtained, and after appropriate phase compensation with a duration of about 11 as. In addition, by performing time-frequency analyses and the classical trajectory simulation, the difference in supercontinuum generation between the preceding wave form and a similar wave form synthesized by an 800-nm fundamental pulse and a 1600-nm subharmonic pulse is investigated.« less

A Compact Ti:Sapphire Laser With its Third Harmonic Generation (THG) for an Airborne Ozone Differential Absorption Lidar (DIAL) Transmitter

NASA Technical Reports Server (NTRS)

Chen, Songsheng; Storm, Mark E.; Marsh, Waverly D.; Petway, Larry B.; Edwards, William C.; Barnes, James C.

2000-01-01

A compact and high-pulse-energy Ti:Sapphire laser with its Third Harmonic Generation (THG) has been developed for an airborne ozone differential absorption lidar (DIAL) to study the distributions and concentrations of the ozone throughout the troposphere. The Ti:Sapphire laser, pumped by a frequency-doubled Nd:YAG laser and seeded by a single mode diode laser, is operated either at 867 nm or at 900 nm with a pulse repetition frequency of 20 Hz. High energy laser pulses (more than 110 mJ/pulse) at 867 nm or 900 nm with a desired beam quality have been achieved and utilized to generate its third harmonic at 289nm or 300nm, which are on-line and off-line wavelengths of an airborne ozone DIAL. After being experimentally compared with Beta-Barium Borate (beta - BaB2O4 or BBO) nonlinear crystals, two Lithium Triborate (LBO) crystals (5 x 5 x 20 cu mm) are selected for the Third Harmonic Generation (THG). In this paper, we report the Ti:Sapphire laser at 900 nm and its third harmonic at 300 nm. The desired high ultraviolet (UV) output pulse energy is more than 30 mJ at 300 nm and the energy conversion efficiency from 900 nm to 300 nm is 30%.

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.

XUV ionization of aligned molecules

NASA Astrophysics Data System (ADS)

Kelkensberg, F.; Rouzée, A.; Siu, W.; Gademann, G.; Johnsson, P.; Lucchini, M.; Lucchese, R. R.; Vrakking, M. J. J.

2011-11-01

New extreme-ultraviolet (XUV) light sources such as high-order-harmonic generation (HHG) and free-electron lasers (FELs), combined with laser-induced alignment techniques, enable novel methods for making molecular movies based on measuring molecular frame photoelectron angular distributions. Experiments are presented where CO2 molecules were impulsively aligned using a near-infrared laser and ionized using femtosecond XUV pulses obtained by HHG. Measured electron angular distributions reveal contributions from four orbitals and the onset of the influence of the molecular structure.

Is energy pooling necessary in ultraviolet matrix-assisted laser desorption/ionization?

PubMed

Lin, Hou-Yu; Song, Botao; Lu, I-Chung; Hsu, Kuo-Tung; Liao, Chih-Yu; Lee, Yin-Yu; Tseng, Chien-Ming; Lee, Yuan-Tseh; Ni, Chi-Kung

2014-01-15

Energy pooling has been suggested as the key process for generating the primary ions during ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI). In previous studies, decreases in fluorescence quantum yields as laser fluence increased for 2-aminobenzoic acid, 2,5-dihydroxybenzoic acid (2,5-DHB), and 3-hydroxypicolinic acid were used as evidence of energy pooling. This work extends the research to other matrices and addresses whether energy pooling is a universal property in UV-MALDI. Energy pooling was investigated in a time-resolved fluorescence experiment by using a short laser pulse (355 nm, 20 ps pulse width) for excitation and a streak camera (1 ps time resolution) for fluorescence detection. The excited-state lifetime of 2,5-DHB decreased with increases in laser fluence. This suggests that a reaction occurs between two excited molecules, and that energy pooling may be one of the possible reactions. However, the excited-state lifetime of 2,4,6-trihydroxyacetophenone (THAP) did not change with increases in laser fluence. The upper limit of the energy pooling rate constant for THAP is estimated to be approximately 100-500 times smaller than that of 2,5-DHB. The small energy pooling rate constant for THAP indicates that the potential contribution of the energy pooling mechanism to the generation of THAP matrix primary ions should be reconsidered. Copyright © 2013 John Wiley & Sons, Ltd.

Single-electron pulses for ultrafast diffraction

PubMed Central

Aidelsburger, M.; Kirchner, F. O.; Krausz, F.; Baum, P.

2010-01-01

Visualization of atomic-scale structural motion by ultrafast electron diffraction and microscopy requires electron packets of shortest duration and highest coherence. We report on the generation and application of single-electron pulses for this purpose. Photoelectric emission from metal surfaces is studied with tunable ultraviolet pulses in the femtosecond regime. The bandwidth, efficiency, coherence, and electron pulse duration are investigated in dependence on excitation wavelength, intensity, and laser bandwidth. At photon energies close to the cathode’s work function, the electron pulse duration shortens significantly and approaches a threshold that is determined by interplay of the optical pulse width and the acceleration field. An optimized choice of laser wavelength and bandwidth results in sub-100-fs electron pulses. We demonstrate single-electron diffraction from polycrystalline diamond films and reveal the favorable influences of matched photon energies on the coherence volume of single-electron wave packets. We discuss the consequences of our findings for the physics of the photoelectric effect and for applications of single-electron pulses in ultrafast 4D imaging of structural dynamics. PMID:21041681

Composition variations in pulsed-laser-deposited Y-Ba-Cu-O thin films as a function of deposition parameters

NASA Technical Reports Server (NTRS)

Foote, M. C.; Jones, B. B.; Hunt, B. D.; Barner, J. B.; Vasquez, R. P.; Bajuk, L. J.

1992-01-01

The composition of pulsed-ultraviolet-laser-deposited Y-Ba-Cu-O films was examined as a function of position across the substrate, laser fluence, laser spot size, substrate temperature, target conditioning, oxygen pressure and target-substrate distance. Laser fluence, laser spot size, and substrate temperature were found to have little effect on composition within the range investigated. Ablation from a fresh target surface results in films enriched in copper and barium, both of which decrease in concentration until a steady state condition is achieved. Oxygen pressure and target-substrate distance have a significant effect on film composition. In vacuum, copper and barium are slightly concentrated at the center of deposition. With the introduction of an oxygen background pressure, scattering results in copper and barium depletion in the deposition center, an effect which increases with increasing target-substrate distance. A balancing of these two effects results in stoichiometric deposition.

High-order harmonics measured by the photon statistics of the infrared driving-field exiting the atomic medium.

PubMed

Tsatrafyllis, N; Kominis, I K; Gonoskov, I A; Tzallas, P

2017-04-27

High-order harmonics in the extreme-ultraviolet spectral range, resulting from the strong-field laser-atom interaction, have been used in a broad range of fascinating applications in all states of matter. In the majority of these studies the harmonic generation process is described using semi-classical theories which treat the electromagnetic field of the driving laser pulse classically without taking into account its quantum nature. In addition, for the measurement of the generated harmonics, all the experiments require diagnostics in the extreme-ultraviolet spectral region. Here by treating the driving laser field quantum mechanically we reveal the quantum-optical nature of the high-order harmonic generation process by measuring the photon number distribution of the infrared light exiting the harmonic generation medium. It is found that the high-order harmonics are imprinted in the photon number distribution of the infrared light and can be recorded without the need of a spectrometer in the extreme-ultraviolet.

High-order harmonics measured by the photon statistics of the infrared driving-field exiting the atomic medium

PubMed Central

Tsatrafyllis, N.; Kominis, I. K.; Gonoskov, I. A.; Tzallas, P.

2017-01-01

High-order harmonics in the extreme-ultraviolet spectral range, resulting from the strong-field laser-atom interaction, have been used in a broad range of fascinating applications in all states of matter. In the majority of these studies the harmonic generation process is described using semi-classical theories which treat the electromagnetic field of the driving laser pulse classically without taking into account its quantum nature. In addition, for the measurement of the generated harmonics, all the experiments require diagnostics in the extreme-ultraviolet spectral region. Here by treating the driving laser field quantum mechanically we reveal the quantum-optical nature of the high-order harmonic generation process by measuring the photon number distribution of the infrared light exiting the harmonic generation medium. It is found that the high-order harmonics are imprinted in the photon number distribution of the infrared light and can be recorded without the need of a spectrometer in the extreme-ultraviolet. PMID:28447616

Ultraviolet Laser-induced ignition of RDX single crystal

PubMed Central

Yan, Zhonghua; Zhang, Chuanchao; Liu, Wei; Li, Jinshan; Huang, Ming; Wang, Xuming; Zhou, Guorui; Tan, Bisheng; Yang, Zongwei; Li, Zhijie; Li, Li; Yan, Hongwei; Yuan, Xiaodong; Zu, Xiaotao

2016-01-01

The RDX single crystals are ignited by ultraviolet laser (355 nm, 6.4 ns) pulses. The laser-induced damage morphology consisted of two distinct regions: a core region of layered fracture and a peripheral region of stripped material surrounding the core. As laser fluence increases, the area of the whole crack region increases all the way, while both the area and depth of the core region increase firstly, and then stay stable over the laser fluence of 12 J/cm2. The experimental details indicate the dynamics during laser ignition process. Plasma fireball of high temperature and pressure occurs firstly, followed by the micro-explosions on the (210) surface, and finally shock waves propagate through the materials to further strip materials outside and yield in-depth cracks in larger surrounding region. The plasma fireball evolves from isotropic to anisotropic under higher laser fluence resulting in the damage expansion only in lateral direction while maintaining the fixed depth. The primary insights into the interaction dynamics between laser and energetic materials can help developing the superior laser ignition technique. PMID:26847854

Ultimate waveform reproducibility of extreme-ultraviolet pulses by high-harmonic generation in quartz

NASA Astrophysics Data System (ADS)

Garg, M.; Kim, H. Y.; Goulielmakis, E.

2018-05-01

Optical waveforms of light reproducible with subcycle precision underlie applications of lasers in ultrafast spectroscopies, quantum control of matter and light-based signal processing. Nonlinear upconversion of optical pulses via high-harmonic generation in gas media extends these capabilities to the extreme ultraviolet (EUV). However, the waveform reproducibility of the generated EUV pulses in gases is inherently sensitive to intensity and phase fluctuations of the driving field. We used photoelectron interferometry to study the effects of intensity and carrier-envelope phase of an intense single-cycle optical pulse on the field waveform of EUV pulses generated in quartz nanofilms, and contrasted the results with those obtained in gas argon. The EUV waveforms generated in quartz were found to be virtually immune to the intensity and phase of the driving field, implying a non-recollisional character of the underlying emission mechanism. Waveform-sensitive photonic applications and precision measurements of fundamental processes in optics will benefit from these findings.

Extreme ultraviolet interferometry of warm dense matter in laser plasmas.

PubMed

Gartside, L M R; Tallents, G J; Rossall, A K; Wagenaars, E; Whittaker, D S; Kozlová, M; Nejdl, J; Sawicka, M; Polan, J; Kalal, M; Rus, B

2010-11-15

We demonstrate that interferometric probing with extreme ultraviolet (EUV) laser light enables determination of the degree of ionization of the "warm dense matter" produced between the critical and ablation surfaces of laser plasmas. Interferometry has been utilized to measure both transmission and phase information for an EUV laser beam at the photon energy of 58.5 eV, probing longitudinally through laser-irradiated plastic (parylene-N) targets (thickness 350 nm) irradiated by a 300 ps duration pulse of wavelength 438 nm and peak irradiance 10(12) W cm(-2). The transmission of the EUV probe beam provides a measure of the rate of target ablation, as ablated plasma becomes close to transparent when the photon energy is less than the ionization energy of the predominant ion species. We show that refractive indices η below the solid parylene N (η(solid) = 0.946) and expected plasma values are produced in the warm dense plasma created by laser irradiation due to bound-free absorption in C(+).

Generation of coherent two-color pulses at two adjacent harmonics in a seeded free-electron laser

NASA Astrophysics Data System (ADS)

Zhao, Zhouyu; Li, Heting; Jia, Qika

2018-02-01

The growing requirements of pump-probe techniques and nonlinear optics experiments greatly promote the studies of two-color free-electron lasers (FELs). We propose a new method to generate coherent two-color pulses in a high-gain harmonic generation (HGHG) FEL. In this scheme, an initial tilted electron beam is sent though the modulator and dispersive section of an HGHG FEL to generate the bunching at harmonics of the seed laser. Then a transverse gradient undulator (TGU) is adopted as the radiator and in such radiator, only two separated fractions of the tilted beam will resonate at two adjacent harmonics of the seed laser and are enabled to emit the coherent two-color pulses simultaneously. The time separation between the two pulses are on the order of hundreds of femtoseconds, and can be precisely controlled by varying the tilted amplitude of the electron beam and/or the transverse gradient of the TGU radiator. Numerical simulations confirm the validity and feasibility of this scheme in the extreme ultraviolet waveband.

A tribute to Dr. Ron W. Waynant (Conference Presentation)

NASA Astrophysics Data System (ADS)

Gannot, Israel; Ilev, Ilko K.; Anders, Juanita J.; Kang, Jin U.

2017-02-01

Ron, our beloved mentor, friend and colleague has passed away on May 7th, 2016. This presentation will follow his life and remarkable achievements. It will describe his work and original developments in three major fields of his interest: his early inventive work on vacuum ultraviolet laser radiation; specialty fiber-optics for laser transmission, especially high-power short-pulse broadband laser delivery of free-electron laser; and up to his latest work on Photobiomodulation. The authors will share their personal experience working with Ron - a Nobel and creative person, however, very humble.

Ultraviolet-Diode Pump Solid State Laser Removal of Titanium Aluminium Nitride Coating from Tungsten Carbide Substrate

NASA Astrophysics Data System (ADS)

See, Tian Long; Chantzis, Dimitrios; Royer, Raphael; Metsios, Ioannis; Antar, Mohammad; Marimuthu, Sundar

2017-09-01

This paper presents an investigation on the titanium aluminium nitride (TiAlN) coating removal from tungsten carbide (WC-Co) substrate using a diode pump solid state (DPSS) ultraviolet (UV) laser with maximum average power of 90 W, wavelength of 355 nm and pulse width of 50 ns. The TiAlN coating of 1.5 μm thickness is removed from the WC-Co substrate with laser fluence of 2.71 J/cm2 at 285.6 number of pulses (NOP) and with NOP of 117.6 at 3.38 J/cm2 fluence. Titanium oxide formation was observed on the ablated surface due to the re-deposition of ablated titanium residue and also attributed to the high temperature observed during the laser ablation process. Crack width of around 0.2 μm was observed over both TiAlN coating and WC-Co substrate. The crack depth ranging from 1 to 10 μm was observed and is related to the thickness of the melted carbide. The crack formation is a result of the thermal induced stresses caused by the laser beam interaction with the material as well as the higher thermal conductivity of cobalt compared to WC. Two cleaning regions are observed and is a consequence of the Gaussian distribution of the laser beam energy. The surface roughness of the ablated WC-Co increased with increasing laser fluence and NOP.

The role of film interfaces in near-ultraviolet absorption and pulsed-laser damage in ion-beam-sputtered coatings based on HfO 2/SiO 2 thin-film pairs

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

Ristau, Detlev; Papernov, S.; Kozlov, A. A.

2015-11-23

The role of thin-film interfaces in the near-ultraviolet absorption and pulsed-laser–induced damage was studied for ion-beam–sputtered and electron-beam–evaporated coatings comprised from HfO 2 and SiO 2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage-threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO 2 single-layer film and for a film containing seven narrow HfO 2 layers separated by SiO 2 layers. The seven-layer film was designed to have a total optical thickness of HfO 2 layers, equal to one wave at 355 nm and an E-field peak and averagemore » intensity similar to a single-layer HfO 2 film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces, as compared to HfO 2 film material. The relevance of obtained absorption data to coating near-ultraviolet, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO 2 film in both sputtered and evaporated coatings. Here, the results are explained through the similarity of interfacial film structure with structure formed during the co-deposition of HfO 2 and SiO 2 materials.« less

Optically pumped cerium-doped LiSrAlF{sub 6} and LiCaAlF{sub 6}

DOEpatents

Marshall, C.D.; Payne, S.A.; Krupke, W.F.

1996-05-14

Ce{sup 3+}-doped LiSrAlF{sub 6} crystals are pumped by ultraviolet light which is polarized along the c axis of the crystals to effectively energize the laser system. In one embodiment, the polarized fourth harmonic light output from a conventional Nd:YAG laser operating at 266 nm is arranged to pump Ce:LiSrAlF{sub 6} with the pump light polarized along the c axis of the crystal. The Ce:LiSrAlF{sub 6} crystal may be placed in a laser cavity for generating tunable coherent ultraviolet radiation in the range of 280-320 nm. Additionally, Ce-doped crystals possessing the LiSrAlF{sub 6} type of chemical formula, e.g. Ce-doped LiCaAlF{sub 6} and LiSrGaF{sub 6}, can be used. Alternative pump sources include an ultraviolet-capable krypton or argon laser, or ultraviolet emitting flashlamps. The polarization of the pump light will impact operation. The laser system will operate efficiently when light in the 280-320 nm gain region is injected or recirculated in the system such that the beam is also polarized along the c axis of the crystal. The Ce:LiSrAlF{sub 6} laser system can be configured to generate ultrashort pulses, and it may be used to pump other devices, such as an optical parametric oscillator. 10 figs.

Optically pumped cerium-doped LiSrAlF.sub.6 and LiCaAlF.sub.6

DOEpatents

Marshall, Christopher D.; Payne, Stephen A.; Krupke, William F.

1996-01-01

Ce.sup.3+ -doped LiSrAlF.sub.6 crystals are pumped by ultraviolet light which is polarized along the c axis of the crystals to effectively energize the laser system. In one embodiment, the polarized fourth harmonic light output from a conventional Nd:YAG laser operating at 266 nm is arranged to pump Ce:LiSrAlF.sub.6 with the pump light polarized along the c axis of the crystal. The Ce:LiSrAlF.sub.6 crystal may be placed in a laser cavity for generating tunable coherent ultraviolet radiation in the range of 280-320 nm. Additionally, Ce-doped crystals possessing the LiSrAlF.sub.6 type of chemical formula, e.g. Ce-doped LiCaAlF.sub.6 and LiSrGaF.sub.6, can be used. Alternative pump sources include an ultraviolet-capable krypton or argon laser, or ultraviolet emitting flashlamps. The polarization of the pump light will impact operation. The laser system will operate efficiently when light in the 280-320 nm gain region is injected or recirculated in the system such that the beam is also polarized along the c axis of the crystal. The Ce:LiSrAlF.sub.6 laser system can be configured to generate ultrashort pulses, and it may be used to pump other devices, such as an optical parametric oscillator.

POWER RECYCLING OF BURST-MODE LASER PULSES FOR LASER PARTICLE INTERACTIONS

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

Liu, Yun

A number of laser-particle interaction experiments such as the laser assisted hydrogen ion beam stripping or X-/ -ray generations via inverse-Compton scattering involve light sources operating in a burst mode to match the tem-poral structure of the particle beam. To mitigate the laser power challenge, it is important to make the interaction inside an optical cavity to recycle the laser power. In many cases, conventional cavity locking techniques will not work since the burst normally has a very small duty factor and low repetition rate and it is impossible to gen-erate an effective control signal. This work reports on themore » development of a doubly-resonant optical cavity scheme and its locking techniques that enables a simultaneous resonance of two laser beams with different spectra and/or temporal structures. We demonstrate that such a cavity can be used to recycle burst-mode ultra-violet laser pulses with arbitrary burst lengths and repetition rates.« less

XUV ionization of aligned molecules

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

Kelkensberg, F.; Siu, W.; Gademann, G.

2011-11-15

New extreme-ultraviolet (XUV) light sources such as high-order-harmonic generation (HHG) and free-electron lasers (FELs), combined with laser-induced alignment techniques, enable novel methods for making molecular movies based on measuring molecular frame photoelectron angular distributions. Experiments are presented where CO{sub 2} molecules were impulsively aligned using a near-infrared laser and ionized using femtosecond XUV pulses obtained by HHG. Measured electron angular distributions reveal contributions from four orbitals and the onset of the influence of the molecular structure.

Molecular alignment dependent electron interference in attosecond ultraviolet photoionization

PubMed Central

Yuan, Kai-Jun; Bandrauk, André D.

2015-01-01

We present molecular photoionization processes by intense attosecond ultraviolet laser pulses from numerical solutions of time-dependent Schrödinger equations. Simulations preformed on a single electron diatomic H2+ show minima in molecular photoelectron energy spectra resulting from two center interference effects which depend strongly on molecular alignment. We attribute such sensitivity to the spatial orientation asymmetry of the photoionization process from the two nuclei. A similar influence on photoelectron kinetic energies is also presented. PMID:26798785

Generation of Bright, Spatially Coherent Soft X-Ray High Harmonics in a Hollow Waveguide Using Two-Color Synthesized Laser Pulses.

PubMed

Jin, Cheng; Stein, Gregory J; Hong, Kyung-Han; Lin, C D

2015-07-24

We investigate the efficient generation of low-divergence high-order harmonics driven by waveform-optimized laser pulses in a gas-filled hollow waveguide. The drive waveform is obtained by synthesizing two-color laser pulses, optimized such that highest harmonic yields are emitted from each atom. Optimization of the gas pressure and waveguide configuration has enabled us to produce bright and spatially coherent harmonics extending from the extreme ultraviolet to soft x rays. Our study on the interplay among waveguide mode, atomic dispersion, and plasma effect uncovers how dynamic phase matching is accomplished and how an optimized waveform is maintained when optimal waveguide parameters (radius and length) and gas pressure are identified. Our analysis should help laboratory development in the generation of high-flux bright coherent soft x rays as tabletop light sources for applications.

Widely tunable two-colour seeded free-electron laser source for resonant-pump resonant-probe magnetic scattering

PubMed Central

Ferrari, Eugenio; Spezzani, Carlo; Fortuna, Franck; Delaunay, Renaud; Vidal, Franck; Nikolov, Ivaylo; Cinquegrana, Paolo; Diviacco, Bruno; Gauthier, David; Penco, Giuseppe; Ribič, Primož Rebernik; Roussel, Eleonore; Trovò, Marco; Moussy, Jean-Baptiste; Pincelli, Tommaso; Lounis, Lounès; Manfredda, Michele; Pedersoli, Emanuele; Capotondi, Flavio; Svetina, Cristian; Mahne, Nicola; Zangrando, Marco; Raimondi, Lorenzo; Demidovich, Alexander; Giannessi, Luca; De Ninno, Giovanni; Danailov, Miltcho Boyanov; Allaria, Enrico; Sacchi, Maurizio

2016-01-01

The advent of free-electron laser (FEL) sources delivering two synchronized pulses of different wavelengths (or colours) has made available a whole range of novel pump–probe experiments. This communication describes a major step forward using a new configuration of the FERMI FEL-seeded source to deliver two pulses with different wavelengths, each tunable independently over a broad spectral range with adjustable time delay. The FEL scheme makes use of two seed laser beams of different wavelengths and of a split radiator section to generate two extreme ultraviolet pulses from distinct portions of the same electron bunch. The tunability range of this new two-colour source meets the requirements of double-resonant FEL pump/FEL probe time-resolved studies. We demonstrate its performance in a proof-of-principle magnetic scattering experiment in Fe–Ni compounds, by tuning the FEL wavelengths to the Fe and Ni 3p resonances. PMID:26757813

Relativistic frequency upshift to the extreme ultraviolet regime using self-induced oscillatory flying mirrors

PubMed Central

Kim, I Jong; Pae, Ki Hong; Kim, Chul Min; Kim, Hyung Taek; Yun, Hyeok; Yun, Sang Jae; Sung, Jae Hee; Lee, Seong Ku; Yoon, Jin Woo; Yu, Tae Jun; Jeong, Tae Moon; Nam, Chang Hee; Lee, Jongmin

2012-01-01

Coherent short-wavelength radiation from laser–plasma interactions is of increasing interest in disciplines including ultrafast biomolecular imaging and attosecond physics. Using solid targets instead of atomic gases could enable the generation of coherent extreme ultraviolet radiation with higher energy and more energetic photons. Here we present the generation of extreme ultraviolet radiation through coherent high-harmonic generation from self-induced oscillatory flying mirrors—a new-generation mechanism established in a long underdense plasma on a solid target. Using a 30-fs, 100-TW Ti:sapphire laser, we obtain wavelengths as short as 4.9 nm for an optimized level of amplified spontaneous emission. Particle-in-cell simulations show that oscillatory flying electron nanosheets form in a long underdense plasma, and suggest that the high-harmonic generation is caused by reflection of the laser pulse from electron nanosheets. We expect this extreme ultraviolet radiation to be valuable in realizing a compact X-ray instrument for research in biomolecular imaging and attosecond physics. PMID:23187631

Terahertz Streaking of Few-Femtosecond Relativistic Electron Beams

NASA Astrophysics Data System (ADS)

Zhao, Lingrong; Wang, Zhe; Lu, Chao; Wang, Rui; Hu, Cheng; Wang, Peng; Qi, Jia; Jiang, Tao; Liu, Shengguang; Ma, Zhuoran; Qi, Fengfeng; Zhu, Pengfei; Cheng, Ya; Shi, Zhiwen; Shi, Yanchao; Song, Wei; Zhu, Xiaoxin; Shi, Jiaru; Wang, Yingxin; Yan, Lixin; Zhu, Liguo; Xiang, Dao; Zhang, Jie

2018-04-01

Streaking of photoelectrons with optical lasers has been widely used for temporal characterization of attosecond extreme ultraviolet pulses. Recently, this technique has been adapted to characterize femtosecond x-ray pulses in free-electron lasers with the streaking imprinted by far-infrared and terahertz (THz) pulses. Here, we report successful implementation of THz streaking for time stamping of an ultrashort relativistic electron beam, whose energy is several orders of magnitude higher than photoelectrons. Such an ability is especially important for MeV ultrafast electron diffraction (UED) applications, where electron beams with a few femtosecond pulse width may be obtained with longitudinal compression, while the arrival time may fluctuate at a much larger timescale. Using this laser-driven THz streaking technique, the arrival time of an ultrashort electron beam with a 6-fs (rms) pulse width has been determined with 1.5-fs (rms) accuracy. Furthermore, we have proposed and demonstrated a noninvasive method for correction of the timing jitter with femtosecond accuracy through measurement of the compressed beam energy, which may allow one to advance UED towards a sub-10-fs frontier, far beyond the approximate 100-fs (rms) jitter.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Laser-induced extreme UV radiation sources for manufacturing next-generation integrated circuits

NASA Astrophysics Data System (ADS)

Borisov, V. M.; Vinokhodov, A. Yu; Ivanov, A. S.; Kiryukhin, Yu B.; Mishchenko, V. A.; Prokof'ev, A. V.; Khristoforov, O. B.

2009-10-01

The development of high-power discharge sources emitting in the 13.5±0.135-nm spectral band is of current interest because they are promising for applications in industrial EUV (extreme ultraviolet) lithography for manufacturing integrated circuits according to technological precision standards of 22 nm and smaller. The parameters of EUV sources based on a laser-induced discharge in tin vapours between rotating disc electrodes are investigated. The properties of the discharge initiation by laser radiation at different wavelengths are established and the laser pulse parameters providing the maximum energy characteristics of the EUV source are determined. The EUV source developed in the study emits an average power of 276 W in the 13.5±0.135-nm spectral band on conversion to the solid angle 2π sr in the stationary regime at a pulse repetition rate of 3000 Hz.

Growth of ferroelectric Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} epitaxial films by ultraviolet pulsed laser irradiation of chemical solution derived precursor layers

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

Queraltó, A.; Pérez del Pino, A., E-mail: aperez@icmab.es; Mata, M. de la

2015-06-29

Highly crystalline epitaxial Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} (BST) thin-films are grown on (001)-oriented LaNiO{sub 3}-buffered LaAlO{sub 3} substrates by pulsed laser irradiation of solution derived barium-zirconium-titanium precursor layers using a UV Nd:YAG laser source at atmospheric conditions. The structural analyses of the obtained films, studied by X-ray diffractometry and transmission electron microscopy, demonstrate that laser processing allows the growth of tens of nm-thick BST epitaxial films with crystalline structure similar to that of films obtained through conventional thermal annealing methods. However, the fast pulsed nature of the laser employed leads to crystallization kinetic evolution orders of magnitude faster than inmore » thermal treatments. The combination of specific photothermal and photochemical mechanisms is the main responsible for the ultrafast epitaxial laser-induced crystallization. Piezoresponse microscopy measurements demonstrate equivalent ferroelectric behavior in laser and thermally annealed films, being the piezoelectric constant ∼25 pm V{sup −1}.« less

Method and apparatus for secondary laser pumping by electron beam excitation

DOEpatents

George, E. Victor; Krupke, William F.; Murray, John R.; Powell, Howard T.; Swingle, James C.; Turner, Jr., Charles E.; Rhodes, Charles K.

1978-01-01

An electron beam of energy typically 100 keV excites a fluorescer gas which emits ultraviolet radiation. This radiation excites and drives an adjacent laser gas by optical pumping or photolytic dissociation to produce high efficiency pulses. The invention described herein was made in the course of, or under, United States Energy Research and Development Administration Contract No. W-7405-Eng-48 with the University of California.

Laser-plasma extreme ultraviolet and soft X-ray sources based on a double stream gas puff target: interaction of the radiation pulses with matter

NASA Astrophysics Data System (ADS)

Bartnik, A.

2015-06-01

In this work a review of investigations concerning interaction of intense extreme ultraviolet (EUV) and soft X-ray (SXR) pulses with matter is presented. The investigations were performed using laser-produced plasma (LPP) EUV/SXR sources based on a double stream gas puff target. The sources are equipped with dedicated collectors allowing for efficient focusing of the EUV/SXR radiation pulses. Intense radiation in a wide spectral range, as well as a quasi-monochromatic radiation can be produced. In the paper different kinds of LPP EUV/SXR sources developed in the Institute of Optoelectronics, Military University of Technology are described. Radiation intensities delivered by the sources are sufficient for different kinds of interaction experiments including EUV/SXR induced ablation, surface treatment, EUV fluorescence or photoionized plasma creation. A brief review of the main results concerning this kind of experiments performed by author of the paper are presented. However, since the LPP sources cannot compete with large scale X-ray sources like synchrotrons, free electron lasers or high energy density plasma sources, it was indicated that some investigations not requiring extreme irradiation parameters can be performed using the small scale installations. Some results, especially concerning low temperature photoionized plasmas are very unique and could be hardly obtained using the large facilities.

On- and off-axis spectral emission features from laser-produced gas breakdown plasmas

NASA Astrophysics Data System (ADS)

Harilal, S. S.; Skrodzki, P. J.; Miloshevsky, A.; Brumfield, B. E.; Phillips, M. C.; Miloshevsky, G.

2017-06-01

Laser-heated gas breakdown plasmas or sparks emit profoundly in the ultraviolet and visible region of the electromagnetic spectrum with contributions from ionic, atomic, and molecular species. Laser created kernels expand into a cold ambient with high velocities during their early lifetime followed by confinement of the plasma kernel and eventually collapse. However, the plasma kernels produced during laser breakdown of gases are also capable of exciting and ionizing the surrounding ambient medium. Two mechanisms can be responsible for excitation and ionization of the surrounding ambient: photoexcitation and ionization by intense ultraviolet emission from the sparks produced during the early times of their creation and/or heating by strong shocks generated by the kernel during its expansion into the ambient. In this study, an investigation is made on the spectral features of on- and off-axis emission of laser-induced plasma breakdown kernels generated in atmospheric pressure conditions with an aim to elucidate the mechanisms leading to ambient excitation and emission. Pulses from an Nd:YAG laser emitting at 1064 nm with a pulse duration of 6 ns are used to generate plasma kernels. Laser sparks were generated in air, argon, and helium gases to provide different physical properties of expansion dynamics and plasma chemistry considering the differences in laser absorption properties, mass density, and speciation. Point shadowgraphy and time-resolved imaging were used to evaluate the shock wave and spark self-emission morphology at early and late times, while space and time resolved spectroscopy is used for evaluating the emission features and for inferring plasma physical conditions at on- and off-axis positions. The structure and dynamics of the plasma kernel obtained using imaging techniques are also compared to numerical simulations using the computational fluid dynamics code. The emission from the kernel showed that spectral features from ions, atoms, and molecules are separated in time with early time temperatures and densities in excess of 35 000 K and 4 × 1018/cm3 with an existence of thermal equilibrium. However, the emission from the off-kernel positions from the breakdown plasmas showed enhanced ultraviolet radiation with the presence of N2 bands and is represented by non-local thermodynamic equilibrium (non-LTE) conditions. Our results also highlight that the ultraviolet radiation emitted during the early time of spark evolution is the predominant source of the photo-excitation of the surrounding medium.

On- and off-axis spectral emission features from laser-produced gas breakdown plasmas

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

Harilal, S. S.; Skrodzki, P. J.; Miloshevsky, A.

Laser-heated gas breakdown plasmas or sparks emit profoundly in the ultraviolet and visible region of the electromagnetic spectrum with contributions from ionic, atomic, and molecular species. Laser created kernels expand into a cold ambient with high velocities during its early lifetime followed by confinement of the plasma kernel and eventually collapse. However, the plasma kernels produced during laser breakdown of gases are also capable of exciting and ionizing the surrounding ambient medium. Two mechanisms can be responsible for excitation and ionization of surrounding ambient: viz. photoexcitation and ionization by intense ultraviolet emission from the sparks produced during the early timesmore » of its creation and/or heating by strong shocks generated by the kernel during its expansion into the ambient. In this study, an investigation is made on the spectral features of on- and off-axis emission features of laser-induced plasma breakdown kernels generated in atmospheric pressure conditions with an aim to elucidate the mechanisms leading to ambient excitation and emission. Pulses from an Nd:YAG laser emitting at 1064 nm with 6 ns pulse duration are used to generate plasma kernels. Laser sparks were generated in air, argon, and helium gases to provide different physical properties of expansion dynamics and plasma chemistry considering the differences in laser absorption properties, mass density and speciation. Point shadowgraphy and time-resolved imaging were used to evaluate the shock wave and spark self-emission morphology at early and late times while space and time resolved spectroscopy is used for evaluating the emission features as well as for inferring plasma fundaments at on- and off-axis. Structure and dynamics of the plasma kernel obtained using imaging techniques are also compared to numerical simulations using computational fluid dynamics code. The emission from the kernel showed that spectral features from ions, atoms and molecules are separated in time with an early time temperatures and densities in excess of 35000 K and 4×10 18 /cm 3 with an existence of thermal equilibrium. However, the emission from the off-kernel positions from the breakdown plasmas showed enhanced ultraviolet radiation with the presence of N 2 bands and represented by non-LTE conditions. Finally, our results also highlight that the ultraviolet radiation emitted during early time of spark evolution is the predominant source of the photo-excitation of the surrounding medium.« less

On- and off-axis spectral emission features from laser-produced gas breakdown plasmas

DOE PAGES

Harilal, S. S.; Skrodzki, P. J.; Miloshevsky, A.; ...

2017-06-01

Laser-heated gas breakdown plasmas or sparks emit profoundly in the ultraviolet and visible region of the electromagnetic spectrum with contributions from ionic, atomic, and molecular species. Laser created kernels expand into a cold ambient with high velocities during its early lifetime followed by confinement of the plasma kernel and eventually collapse. However, the plasma kernels produced during laser breakdown of gases are also capable of exciting and ionizing the surrounding ambient medium. Two mechanisms can be responsible for excitation and ionization of surrounding ambient: viz. photoexcitation and ionization by intense ultraviolet emission from the sparks produced during the early timesmore » of its creation and/or heating by strong shocks generated by the kernel during its expansion into the ambient. In this study, an investigation is made on the spectral features of on- and off-axis emission features of laser-induced plasma breakdown kernels generated in atmospheric pressure conditions with an aim to elucidate the mechanisms leading to ambient excitation and emission. Pulses from an Nd:YAG laser emitting at 1064 nm with 6 ns pulse duration are used to generate plasma kernels. Laser sparks were generated in air, argon, and helium gases to provide different physical properties of expansion dynamics and plasma chemistry considering the differences in laser absorption properties, mass density and speciation. Point shadowgraphy and time-resolved imaging were used to evaluate the shock wave and spark self-emission morphology at early and late times while space and time resolved spectroscopy is used for evaluating the emission features as well as for inferring plasma fundaments at on- and off-axis. Structure and dynamics of the plasma kernel obtained using imaging techniques are also compared to numerical simulations using computational fluid dynamics code. The emission from the kernel showed that spectral features from ions, atoms and molecules are separated in time with an early time temperatures and densities in excess of 35000 K and 4×1018 /cm3 with an existence of thermal equilibrium. However, the emission from the off-kernel positions from the breakdown plasmas showed enhanced ultraviolet radiation with the presence of N2 bands and represented by non-LTE conditions. Our results also highlight that the ultraviolet radiation emitted during early time of spark evolution is the predominant source of the photo-excitation of the surrounding medium.« less

All-femtosecond laser-assisted in situ keratomileusis

NASA Astrophysics Data System (ADS)

Gabryte, Egle; Danieliene, Egle; Vaiceliunaite, Agne; Ruksenas, Osvaldas; Vengris, Mikas; Danielius, Romualdas

2013-03-01

We present a femtosecond solid-state Yb:KGW laser system capable of performing the complete laser-assisted in situ keratomileusis (LASIK) ophthalmic procedure. The fundamental infrared radiation (IR) is used to create the corneal flap, and subsequently the corneal stromal ablation is performed using the ultraviolet (UV) pulses of the fifth harmonic. The heating of cornea, ablated surface quality, and healing outcomes of the surgeries performed using the femtosecond laser system are investigated by both ex vivo and in vivo experiments and compared to the results of conventional clinical ArF excimer laser application. The results of this research indicate the feasibility of clinical application of femtosecond UV lasers for LASIK procedure.

A soft X-ray source based on a low divergence, high repetition rate ultraviolet laser

NASA Astrophysics Data System (ADS)

Crawford, E. A.; Hoffman, A. L.; Milroy, R. D.; Quimby, D. C.; Albrecht, G. F.

The CORK code is utilized to evaluate the applicability of low divergence ultraviolet lasers for efficient production of soft X-rays. The use of the axial hydrodynamic code wih one ozone radial expansion to estimate radial motion and laser energy is examined. The calculation of ionization levels of the plasma and radiation rates by employing the atomic physics and radiation model included in the CORK code is described. Computations using the hydrodynamic code to determine the effect of laser intensity, spot size, and wavelength on plasma electron temperature are provided. The X-ray conversion efficiencies of the lasers are analyzed. It is observed that for a 1 GW laser power the X-ray conversion efficiency is a function of spot size, only weakly dependent on pulse length for time scales exceeding 100 psec, and better conversion efficiencies are obtained at shorter wavelengths. It is concluded that these small lasers focused to 30 micron spot sizes and 10 to the 14th W/sq cm intensities are useful sources of 1-2 keV radiation.

Simultaneous operation of two soft x-ray free-electron lasers driven by one linear accelerator

DOE PAGES

Faatz, B.; Plönjes, E.; Ackermann, S.; ...

2016-06-20

Extreme-ultraviolet to x-ray free-electron lasers (FELs) in operation for scientific applications are up to now single-user facilities. While most FELs generate around 100 photon pulses per second, FLASH at DESY can deliver almost two orders of magnitude more pulses in this time span due to its superconducting accelerator technology. This makes the facility a prime candidate to realize the next step in FELs—dividing the electron pulse trains into several FEL lines and delivering photon pulses to several users at the same time. Hence, FLASH has been extended with a second undulator line and self-amplified spontaneous emission (SASE) is demonstrated inmore » both FELs simultaneously. Here, FLASH can now deliver MHz pulse trains to two user experiments in parallel with individually selected photon beam characteristics. First results of the capabilities of this extension are shown with emphasis on independent variation of wavelength, repetition rate, and photon pulse length.« less

HV discharge acceleration by sequences of UV laser filaments with visible and near-infrared pulses

NASA Astrophysics Data System (ADS)

Schubert, Elise; Rastegari, Ali; Feng, Chengyong; Mongin, Denis; Kamer, Brian; Kasparian, Jérôme; Wolf, Jean-Pierre; Arissian, Ladan; Diels, Jean-Claude

2017-12-01

We investigate the triggering and guiding of DC high-voltage discharges over a distance of 37 cm by filaments produced by ultraviolet (266 nm) laser pulses of 200 ps duration. The latter reduce the breakdown electric field by half and allow up to 80% discharge probability in an electric field of 920 kV m–1. This high efficiency is not further increased by adding nanosecond pulses in the Joule range at 532 and at 1064 nm. However, the latter statistically increases the guiding length, thereby accelerating the discharge by a factor of 2. This effect is due both to photodetachment and to the heating of the plasma channel, that increases the efficiency of avalanche ionization and reduces electron attachment and recombination.

Role of HfO 2/SiO 2 thin-film interfaces in near-ultraviolet absorption and pulsed laser damage

DOE PAGES

Papernov, Semyon; Kozlov, Alexei A.; Oliver, James B.; ...

2016-07-15

Here, the role of thin-film interfaces in the near-ultraviolet (near-UV) absorption and pulsed laser-induced damage was studied for ion-beam-sputtered and electron-beam-evaporated coatings comprised from HfO 2 and SiO 2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO 2 single-layer film and for a film containing seven narrow HfO 2 layers separated by SiO 2 layers. The seven-layer film was designed to have a total optical thickness of HfO 2 layers, equal to one wave at 355 nm and anmore » E-field peak and average intensity similar to a single-layer HfO 2 film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces as compared to HfO 2 film material. The relevance of obtained absorption data to coating near-UV, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO 2 film in both sputtered and evaporated coatings. The results are explained through the similarity of interfacial film structure with structure formed during the codeposition of HfO 2 and SiO 2 materials.« less

A passion for precision

ScienceCinema

Hänsch, Theodor W.

2018-05-23

For more than three decades, the quest for ever higher precision in laser spectroscopy of the simple hydrogen atom has inspired many advances in laser, optical, and spectroscopic techniques, culminating in femtosecond laser optical frequency combs  as perhaps the most precise measuring tools known to man. Applications range from optical atomic clocks and tests of QED and relativity to searches for time variations of fundamental constants. Recent experiments are extending frequency comb techniques into the extreme ultraviolet. Laser frequency combs can also control the electric field of ultrashort light pulses, creating powerful new tools for the emerging field of attosecond science.

Ferroelectric domain engineering by focused infrared femtosecond pulses

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

Chen, Xin; Shvedov, Vladlen; Sheng, Yan, E-mail: yan.sheng@anu.edu.au

2015-10-05

We demonstrate infrared femtosecond laser-induced inversion of ferroelectric domains. This process can be realised solely by using tightly focused laser pulses without application of any electric field prior to, in conjunction with, or subsequent to the laser irradiation. As most ferroelectric crystals like LiNbO{sub 3}, LiTaO{sub 3}, and KTiOPO{sub 4} are transparent in the infrared, this optical poling method allows one to form ferroelectric domain patterns much deeper inside a ferroelectric crystal than by using ultraviolet light and hence can be used to fabricate practical devices. We also propose in situ diagnostics of the ferroelectric domain inversion process by monitoringmore » the Čerenkov second harmonic signal, which is sensitive to the appearance of ferroelectric domain walls.« less

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

Surface patterning of multilayer graphene by ultraviolet laser irradiation in biomolecule sensing devices

NASA Astrophysics Data System (ADS)

Chang, Tien-Li; Chen, Zhao-Chi

2015-12-01

The study presents a direct process for surface patterning of multilayer graphene on the glass substrate as a biosensing device. In contrast to lithography with etching, the proposed process provides simultaneous surface patterning of multilayer graphene through nanosecond laser irradiation. In this study, the multilayer graphene was prepared by a screen printing process. Additionally, the wavelength of the laser beam was 355 nm. To perform the effective laser process with the small heat affected zone, the surface patterns on the sensing devices could be directly fabricated using the laser with optimal control of the pulse overlap at a fluence threshold of 0.63 J/cm2. The unique patterning of the laser-ablated surface exhibits their electrical and hydrophilic characteristics. The hydrophilic surface of graphene-based sensing devices was achieved in the process with the pulse overlap of 90%. Furthermore, the sensing devices for controlling the electrical response of glucose by using glucose oxidase can be used in sensors in commercial medical applications.

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.

Scaling EUV and X-ray Thomson sources to optical free-electron laser operation with traveling-wave Thomson scattering (Conference Presentation)

NASA Astrophysics Data System (ADS)

Steiniger, Klaus; Albach, Daniel; Debus, Alexander; Loeser, Markus; Pausch, Richard; Roeser, Fabian; Schramm, Ulrich; Siebold, Matthias; Bussmann, Michael

2017-05-01

Traveling-Wave Thomson-Scattering (TWTS) allows for the realization of optical free-electron lasers (OFELs) from the interaction of short, high-power laser pulses with brilliant relativistic electron bunches. The laser field provides the optical undulator which is traversed by the electrons. In order to achieve coherent amplification of radiation through electron microbunching the interaction between electrons and laser must be maintained over hundreds to thousands of undulator periods. Traveling-Wave Thomson-Scattering is the only scattering geometry so far allowing for the realization of optical undulators of this length which is at the same time scalable from extreme ultraviolet to X-ray photon energies. TWTS is also applicable for the realization of incoherent high peak brightness hard X-ray to gamma-ray sources which can provide orders of magnitude higher photon output than classic head-on Thomson sources. In contrast to head-on Thomson sources TWTS employs a side-scattering geometry where laser and electron propagation direction of motion enclose an angle. Tilting the laser pulse front with respect to the wave front by half of this interaction angle optimizes electron and laser pulse overlap. In the side-scattering geometry the tilt of the pulse-front compensates the spatial offset between electrons and laser pulse-front which would be present otherwise for an electron bunch far from the interaction point where it overlaps with the laser pulse center. Thus the laser pulse-front tilt ensures continuous overlap between laser pulse and electrons while these traverse the laser pulse cross-sectional area. This allows to control the interaction distance in TWTS by the laser pulse width rather than laser pulse duration as is the case for head-on Thomson scattering. Utilizing petawatt class laser pulses with millimeter to centimeter scale width allows for the realization of compact optical undulators with thousands of periods. When laser pulses for TWTS are prepared, care has to be taken of laser dispersion. Especially for scenarios featuring interaction angles of several ten to over one hundred degree the angular dispersion originating from laser pulse-front tilt can significantly prolong the pulse duration during the interaction which leads to a decrease in optical undulator amplitude and eventually terminates the interaction long before the target interaction distance is reached. In the talk it is shown how a pair of two gratings can be used to first generate the pulse-front tilt and second control and compensate dispersion during the interaction by utilizing the plane of optimum compression. Furthermore an experimental setup strategy is presented allowing for an interaction outside the laser pulse focus. This is a necessity for TWTS OFELs requiring focusing to reach optical undulator strengths on the order of unity since the centimeter scale laser pulse width at the interaction point result in turn in Rayleigh lengths on the order of one hundred meter and thus in laser focusing distances of several hundred meter. The talk shows how an out-of-focus interaction geometry utilizing strong focusing of the incident laser pulse needs to be designed in order to regain compactness by reducing the focusing distance by one to two orders of magnitude.

Ultraviolet-infrared laser-induced domain inversion in MgO-doped congruent LiNbO3 and near stoichiometric LiTaO3 crystals

NASA Astrophysics Data System (ADS)

Zhi, Ya'nan; Qu, Weijuan; Liu, De'an; Sun, Jianfeng; Yan, Aimin; Liu, Liren

2008-08-01

Laser-induced domain inversion is a promising technique for domain engineering in LiNbO3 and LiTaO3. The ultraviolet-infrared laser induced domain inversions in MgO-doped congruent LiNbO3 and near stoichiometric LiTaO3 crystals are investigated for the first time here. Within the wavelength range from 351 to 799 nm, the different reductions of nucleation field induced by the focused continuous laser irradiation are systematically investigated in the MgO-doped congruent LiNbO3 crystals. The investigation of ultrashort-pulse laser-induced domain inversion in MgO-doped congruent LiNbO3 is performed with 800 nm wavelength irradiation. The focused continuous ultraviolet laser-induced ferroelectric domain inversion in the near stoichiometric LiTaO3 is also investigated. The different physical explanations, based on space charge field and defect formation, are presented for the laser-induced domain inversion, and the solid experimental proofs are also presented. The results provide the solid experimental proofs and feasible schemes for the further investigation of laser-induced domain engineering in MgO-doped LiNbO3 and near stoichiometric LiTaO3 crystals. The important characteristics of domain inversion, including domain wall and internal field, in LiNbO3 crystals are also investigated by the digital holographic interferometry with an improved reconstruction method, and some creative experimental results and conclusions are achieved.

Nail-like targets for laser plasma interaction experiments

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

Pasley, J; Wei, M; Shipton, E

2007-12-18

The interaction of ultra-high power picosecond laser pulses with solid targets is of interest both for benchmarking the results of hybrid particle in cell (PIC) codes and also for applications to re-entrant cone guided fast ignition. We describe the construction of novel targets in which copper/titanium wires are formed into 'nail-like' objects by a process of melting and micromachining, so that energy can be reliably coupled to a 24 {micro}m diameter wire. An extreme-ultraviolet image of the interaction of the Titan laser with such a target is shown.

Method for adhesion of metal films to ceramics

DOEpatents

Lowndes, Douglas H.; Pedraza, Anthony J.; DeSilva, Melvin J.; Kumar, Rajagopalan A.

1997-01-01

Methods for making strongly bonded metal-ceramic materials. The methods include irradiating a portion of the surface of the ceramic material with a pulsed ultraviolet laser having an energy density sufficient to effect activation of the irradiated surface of the ceramic material so that adhesion of metals subsequently deposited onto the irradiated surface is substantially increased. Advantages of the invention include (i) the need for only a small number of laser pulses at relatively low focused energy density, (ii) a smoother substrate surface, (iii) activation of the laser-treated surface which provides a chemical bond between the surface and a metal deposited thereon, (iv) only low temperature annealing is required to produce the strong metal-ceramic bond; (v) the ability to obtain strong adhesion between ceramic materials and oxidation resistant metals; (vi) ability to store the laser treated ceramic materials for later deposition of metals thereon.

IR-laser assisted additive freeform optics manufacturing.

PubMed

Hong, Zhihan; Liang, Rongguang

2017-08-02

Computer-controlled additive manufacturing (AM) processes, also known as three-dimensional (3D) printing, create 3D objects by the successive adding of a material or materials. While there have been tremendous developments in AM, the 3D printing of optics is lagging due to the limits in materials and tight requirements for optical applicaitons. We propose a new precision additive freeform optics manufacturing (AFOM) method using an pulsed infrared (IR) laser. Compared to ultraviolet (UV) curable materials, thermally curable optical silicones have a number of advantages, such as strong UV stability, non-yellowing, and high transmission, making it particularly suitable for optical applications. Pulsed IR laser radiation offers a distinct advantage in processing optical silicones, as the high peak intensity achieved in the focal region allows for curing the material quickly, while the brief duration of the laser-material interaction creates a negligible heat-affected zone.

Method for adhesion of metal films to ceramics

DOEpatents

Lowndes, D.H.; Pedraza, A.J.; DeSilva, M.J.; Kumar, R.A.

1997-12-30

Methods for making strongly bonded metal-ceramic materials are disclosed. The methods include irradiating a portion of the surface of the ceramic material with a pulsed ultraviolet laser having an energy density sufficient to effect activation of the irradiated surface of the ceramic material so that adhesion of metals subsequently deposited onto the irradiated surface is substantially increased. Advantages of the invention include (i) the need for only a small number of laser pulses at relatively low focused energy density, (ii) a smoother substrate surface, (iii) activation of the laser-treated surface which provides a chemical bond between the surface and a metal deposited thereon, (iv) only low temperature annealing is required to produce the strong metal-ceramic bond; (v) the ability to obtain strong adhesion between ceramic materials and oxidation resistant metals; (vi) ability to store the laser treated ceramic materials for later deposition of metals thereon. 7 figs.

Ultraviolet Molecular Rayleigh Scattering Used to Measure Velocity in High-Speed Flow

NASA Technical Reports Server (NTRS)

Seasholtz, Richard G.

1997-01-01

Molecular Rayleigh scattering offers a means to measure gas flow parameters including density, temperature, and velocity. No seeding of the flow is necessary. The Rayleigh scattered power is proportional to the gas density, the spectral width is related to the gas temperature, and the shift in the frequency of the spectral peak is proportional to one component of the fluid velocity. Velocity measurements based on Rayleigh scattering are more suitable for high-speed flow, where the bulk fluid velocity is on the order of, or larger than, the molecular thermal velocities. Use of ultraviolet wavelengths for Rayleigh scattering diagnostics is attractive for two reasons. First, the Rayleigh scattering cross section is proportional to the inverse 4th power of the wavelength. And second, the reflectivity of metallic surfaces is generally less than it is at longer wavelengths. This is of particular interest in confined flow situations, such as in small wind tunnels and aircraft engine components, where the stray laser light scattered from the windows and internal surfaces in the test facility limits the application of Rayleigh scattering diagnostics. In this work at the NASA Lewis Research Center, molecular Rayleigh scattering of the 266-nm fourth harmonic of a pulsed, injection seeded Nd:YAG (neodymium:yttriumaluminum- garnet) laser was used to measure velocity in a supersonic free air jet with a 9.3- mm exit diameter. The frequency of the Rayleigh scattered light was analyzed with a planar mirror Fabry-Perot interferometer used in a static imaging mode, with the images recorded on a cooled, high-quantum-efficiency charge-coupled discharge (CCD) camera. In addition, some unshifted light from the same laser pulse was imaged through the interferometer to generate a reference. Data were obtained with single laser pulses at velocities up to Mach 1.3. The measured velocities were in good agreement with velocities calculated from isentropic flow relations. Our conclusion from this study was that ultraviolet Rayleigh scattering is preferable in confined flow situations because of the increase in the ratio of Rayleigh scattering signal to stray laser light. On the other hand, in open flows, such as free jets and larger wind tunnels where stray laser light can be controlled, visible Rayleigh scattering is preferable.

High-harmonic and single attosecond pulse generation using plasmonic field enhancement in ordered arrays of gold nanoparticles with chirped laser pulses.

PubMed

Yang, Ying-Ying; Scrinzi, Armin; Husakou, Anton; Li, Qian-Guang; Stebbings, Sarah L; Süßmann, Frederik; Yu, Hai-Juan; Kim, Seungchul; Rühl, Eckart; Herrmann, Joachim; Lin, Xue-Chun; Kling, Matthias F

2013-01-28

Coherent XUV sources, which may operate at MHz repetition rate, could find applications in high-precision spectroscopy and for spatio-time-resolved measurements of collective electron dynamics on nanostructured surfaces. We theoretically investigate utilizing the enhanced plasmonic fields in an ordered array of gold nanoparticles for the generation of high-harmonic, extreme-ultraviolet (XUV) radiation. By optimization of the chirp of ultrashort laser pulses incident on the array, our simulations indicate a potential route towards the temporal shaping of the plasmonic near-field and, in turn, the generation of single attosecond pulses. The inherent effects of inhomogeneity of the local fields on the high-harmonic generation are analyzed and discussed. While taking the inhomogeneity into account does not affect the optimal chirp for the generation of a single attosecond pulse, the cut-off energy of the high-harmonic spectrum is enhanced by about a factor of two.

Bright high-order harmonic generation with controllable polarization from a relativistic plasma mirror

PubMed Central

Chen, Zi-Yu; Pukhov, Alexander

2016-01-01

Ultrafast extreme ultraviolet (XUV) sources with a controllable polarization state are powerful tools for investigating the structural and electronic as well as the magnetic properties of materials. However, such light sources are still limited to only a few free-electron laser facilities and, very recently, to high-order harmonic generation from noble gases. Here we propose and numerically demonstrate a laser–plasma scheme to generate bright XUV pulses with fully controlled polarization. In this scheme, an elliptically polarized laser pulse is obliquely incident on a plasma surface, and the reflected radiation contains pulse trains and isolated circularly or highly elliptically polarized attosecond XUV pulses. The harmonic polarization state is fully controlled by the laser–plasma parameters. The mechanism can be explained within the relativistically oscillating mirror model. This scheme opens a practical and promising route to generate bright attosecond XUV pulses with desirable ellipticities in a straightforward and efficient way for a number of applications. PMID:27531047

Kinetics of UV laser radiation defects in high performance glasses

NASA Astrophysics Data System (ADS)

Natura, U.; Feurer, T.; Ehrt, D.

2000-05-01

High purity fluoride phosphate glasses are attractive candidates as UV transmitting materials. The calculated values for the ultraviolet resonance wavelength are comparable with those of pure silica glass or fluoride single crystal CaF2. The formation of radiation-induced defect centers leads to additional absorption bands in the VUV-UV-vis range. The damage and the healing behavior by lamps and lasers are investigated in dependence on phosphate content and the content of impurities, mainly transition metals. Experiments were carried out using pulsed lasers with a duration of femto- and nanoseconds at a wavelength of 248 nm. The initial slope of the induced absorption shows a nonlinear dependence on the pulse energy density. Resonant and non-resonant two-photon mechanisms were observed. Two-photon-absorption coefficients at 248 nm for samples with different phosphate contents were measured. Models of the kinetics of the radiation-induced defects were developed. The inclusion of energy transfer was necessary to explain the difference in the damage behavior for nanosecond (248 nm, 193 nm) and femtosecond (248 nm) laser pulses.

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

Detection of polychlorinated biphenyls in transformer oils in Vietnam by multiphoton ionization mass spectrometry using a far-ultraviolet femtosecond laser as an ionization source.

PubMed

Duong, Vu Thi Thuy; Duong, Vu; Lien, Nghiem Thi Ha; Imasaka, Tomoko; Tang, Yuanyuan; Shibuta, Shinpei; Hamachi, Akifumi; Hoa, Do Quang; Imasaka, Totaro

2016-03-01

Polychlorinated biphenyls (PCBs) in transformer and food oils were measured using gas chromatography combined with multiphoton ionization mass spectroscopy. An ultrashort laser pulse emitting in the far-ultraviolet region was utilized for efficient ionization of the analytes. Numerous signal peaks were clearly observed for a standard sample mixture of PCBs when the third and fourth harmonic emissions (267 and 200nm) of a femtosecond Ti:sapphire laser (800nm) were employed. The signal intensities were found to be greater when measured at 200nm compared with those measured at 267nm, providing lower detection limits especially for highly chlorinated PCBs at shorter wavelengths. After simple pretreatment using disposable columns, PCB congeners were measured and found to be present in the transformer oils used in Vietnam. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of an electron momentum spectrometer for time-resolved experiments employing nanosecond pulsed electron beam

NASA Astrophysics Data System (ADS)

Tang, Yaguo; Shan, Xu; Liu, Zhaohui; Niu, Shanshan; Wang, Enliang; Chen, Xiangjun

2018-03-01

The low count rate of (e, 2e) electron momentum spectroscopy (EMS) has long been a major limitation of its application to the investigation of molecular dynamics. Here we report a new EMS apparatus developed for time-resolved experiments in the nanosecond time scale, in which a double toroidal energy analyzer is utilized to improve the sensitivity of the spectrometer and a nanosecond pulsed electron gun with a repetition rate of 10 kHz is used to obtain an average beam current up to nA. Meanwhile, a picosecond ultraviolet laser with a repetition rate of 5 kHz is introduced to pump the sample target. The time zero is determined by photoionizing the target using a pump laser and monitoring the change of the electron beam current with time delay between the laser pulse and electron pulse, which is influenced by the plasma induced by the photoionization. The performance of the spectrometer is demonstrated by the EMS measurement on argon using a pulsed electron beam, illustrating the potential abilities of the apparatus for investigating the molecular dynamics in excited states when employing the pump-probe scheme.

Power enhancement of burst-mode UV pulses using a doubly-resonant optical cavity

DOE PAGES

Rahkman, Abdurahim; Notcutt, Mark; Liu, Yun

2015-11-24

We report a doubly-resonant enhancement cavity (DREC) that can realize a simultaneous enhancement of two incoming laser beams at different wavelengths and different temporal structures. The double-resonance condition is theoretically analyzed and different DREC locking methods are experimentally investigated. Simultaneous locking of a Fabry-Perot cavity to both an infrared (IR, 1064 nm) and its frequency tripled ultraviolet (UV, 355 nm) pulses has been demonstrated by controlling the frequency difference between the two beams with a fiber optic frequency shifter. The DREC technique opens a new paradigm in the applications of optical cavities to power enhancement of burst-mode lasers with arbitrarymore » macropulse width and repetition rate.« less

Wavefront measurement of single-mode quantum cascade laser beam for seed application in laser-produced plasma extreme ultraviolet system.

PubMed

Nowak, Krzysztof M; Ohta, Takeshi; Suganuma, Takashi; Yokotsuka, Toshio; Fujimoto, Junichi; Mizoguchi, Hakaru

2012-12-01

Quantum cascade laser (QCL) is a very attractive seed source for a multikilowatt pulsed CO2 lasers applied for driving extreme ultraviolet emitting plasmas. In this Letter, we investigate output beam properties of a QCL designed to address P18 and P20 lines of 10.6 micron band of CO2 molecule. In particular, output beam quality and stability are investigated for the first time. A well-defined linear polarization and a single-mode operation enabled a use of phase retrieval method for full description of QCL output beam. A direct, multi-image numerical phase retrieval technique was developed and successfully applied to the measured intensity patterns of a QCL beam. Very good agreement between the measured and reconstructed beam profiles was observed at distances ranging from QCL aperture to infinity, proving a good understanding of the beam propagation. The results also confirm a high spatial coherence and high stability of the beam parameters, the features expected from an excellent seed source.

Characterization of gas targets for laser produced extreme ultraviolet plasmas with a Hartmann-Shack sensor

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

Peth, Christian; Kranzusch, Sebastian; Mann, Klaus

2004-10-01

A table top extreme ultraviolet (EUV)-source was developed at Laser-Laboratorium Goettingen for the characterization of optical components and sensoric devices in the wavelength region from 11 to 13 nm. EUV radiation is generated by focusing the beam of a Q-switched Nd:YAG laser into a pulsed xenon gas jet. Since a directed gas jet with a high number density is needed for an optimal performance of the source, conical nozzles with different cone angles were drilled with an excimer laser to produce a supersonic gas jet. The influence of the nozzle geometry on the gas jet was characterized with a Hartmann-Shackmore » wave front sensor. The deformation of a planar wave front after passing the gas jet was analyzed with this sensor, allowing a reconstruction of the gas density distribution. Thus, the gas jet was optimized resulting in an increase of EUV emission by a factor of two and a decrease of the plasma size at the same time.« less

Spatial control of photoemitted electron beams using a microlens-array transverse-shaping technique

DOE PAGES

Halavanau, A.; Qiang, G.; Ha, G.; ...

2017-10-26

A transversely inhomogeneous laser distribution on the photocathode surface generally produces electron beams with degraded beam quality. In this paper, we explore the use of microlens arrays to dramatically improve the transverse uniformity of an ultraviolet drive-laser pulse used in a photoinjector. Here, we also demonstrate a capability of microlens arrays to generate transversely modulated electron beams and present an application of such a feature to diagnose the properties of a magnetized beam.

Whole life cycle of femtosecond ultraviolet filaments in water

NASA Astrophysics Data System (ADS)

Jarnac, Amélie; Tamosauskas, Gintaras; Majus, Donatas; Houard, Aurélien; Mysyrowicz, André; Couairon, Arnaud; Dubietis, Audrius

2014-03-01

We present measurements fully characterizing the whole life cycle of femtosecond pulses undergoing filamentation in water at 400 nm. The complete pulse dynamics is monitored by means of a four-dimensional mapping technique for the intensity distribution I (x,y,z,t) during the nonlinear interaction. Measured events (focusing or defocusing cycles, pulse splitting and replenishment, supercontinuum generation, conical emission, nonlinear absorption peaks) are mutually connected.The filament evolution from laser energy deposition in water, which is of paramount importance for a wide range of technological and medical applications, is interpreted in light of simulation results.

Study of ablation and implosion stages in wire arrays using coupled ultraviolet and X-ray probing diagnostics

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

Anderson, A. A.; Ivanov, V. V.; Astanovitskiy, A. L.

2015-11-15

Star and cylindrical wire arrays were studied using laser probing and X-ray radiography at the 1-MA Zebra pulse power generator at the University of Nevada, Reno. The Leopard laser provided backlighting, producing a laser plasma from a Si target which emitted an X-ray probing pulse at the wavelength of 6.65 Å. A spherically bent quartz crystal imaged the backlit wires onto X-ray film. Laser probing diagnostics at the wavelength of 266 nm included a 3-channel polarimeter for Faraday rotation diagnostic and two-frame laser interferometry with two shearing interferometers to study the evolution of the plasma electron density at the ablation and implosionmore » stages. Dynamics of the plasma density profile in Al wire arrays at the ablation stage were directly studied with interferometry, and expansion of wire cores was measured with X-ray radiography. The magnetic field in the imploding plasma was measured with the Faraday rotation diagnostic, and current was reconstructed.« less

[Alternatives to femtosecond laser technology: subnanosecond UV pulse and ring foci for creation of LASIK flaps].

PubMed

Vogel, A; Freidank, S; Linz, N

2014-06-01

In refractive corneal surgery femtosecond (fs) lasers are used for creating LASIK flaps, dissecting lenticules and for astigmatism correction by limbal incisions. Femtosecond laser systems are complex and expensive and cutting precision is compromised by the large focal length associated with the commonly used infrared (IR) wavelengths. Based on investigations of the cutting dynamics, novel approaches for corneal dissection using ultraviolet A (UVA) picosecond (ps) pulses and ring foci from vortex beams are presented. Laser-induced bubble formation in corneal stroma was investigated by high-speed photography at 1-50 million frames/s. Using Gaussian and vortex beams of UVA pulses with durations between 200 and 850 ps the laser energy needed for easy removal of flaps created in porcine corneas was determined and the quality of the cuts by scanning electron microscopy was documented. Cutting parameters for 850 ps are reported also for rabbit eyes. The UV-induced and mechanical stress were evaluated for Gaussian and vortex beams. The results show that UVA picosecond lasers provide better cutting precision than IR femtosecond lasers, with similar processing times. Cutting energy decreases by >50 % when the laser pulse duration is reduced to 200 ps. Vortex beams produce a short, donut-shaped focus allowing efficient and precise dissection along the corneal lamellae which results in a dramatic reduction of the absorbed energy needed for cutting and of mechanical side effects as well as in less bubble formation in the cutting plane. A combination of novel approaches for corneal dissection provides the option to replace femtosecond lasers by compact UVA microchip laser technology. Ring foci are also of interest for femtosecond laser surgery, especially for improved lenticule excision.

Single-order laser high harmonics in XUV for ultrafast photoelectron spectroscopy of molecular wavepacket dynamics.

PubMed

Fushitani, Mizuho; Hishikawa, Akiyoshi

2016-11-01

We present applications of extreme ultraviolet (XUV) single-order laser harmonics to gas-phase ultrafast photoelectron spectroscopy. Ultrashort XUV pulses at 80 nm are obtained as the 5th order harmonics of the fundamental laser at 400 nm by using Xe or Kr as the nonlinear medium and separated from other harmonic orders by using an indium foil. The single-order laser harmonics is applied for real-time probing of vibrational wavepacket dynamics of I 2 molecules in the bound and dissociating low-lying electronic states and electronic-vibrational wavepacket dynamics of highly excited Rydberg N 2 molecules.

Noncontact detection of homemade explosive constituents via photodissociation followed by laser-induced fluorescence.

PubMed

Wynn, C M; Palmacci, S; Kunz, R R; Rothschild, M

2010-03-15

Noncontact detection of the homemade explosive constituents urea nitrate, nitromethane and ammonium nitrate is achieved using photodissociation followed by laser-induced fluorescence (PD-LIF). Our technique utilizes a single ultraviolet laser pulse (approximately 7 ns) to vaporize and photodissociate the condensed-phase materials, and then to detect the resulting vibrationally-excited NO fragments via laser-induced fluorescence. PD-LIF excitation and emission spectra indicate the creation of NO in vibrationally-excited states with significant rotational energy, useful for low-background detection of the parent compound. The results for homemade explosives are compared to one another and 2,6-dinitrotoluene, a component present in many military explosives.

The influence of femtosecond laser pulse wavelength on embryonic stem cell differentiation

NASA Astrophysics Data System (ADS)

Mthunzi, Patience

2012-10-01

Stem cells are rich in proteins, carbohydrates, deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and various other cellular components which are responsible for a diversity of functions. Mostly the building blocks of these intracellular entities play an active role in absorbing ultra-violet (UV) and visible light sources. Light-matter interactions in biomaterials are a complex situation and subsequent damage may not always amount only from wavelength dependent effects but may also be driven by a wealth of other optical parameters which may lead to a variety photochemical reactions. Previously, literature has reported efficient photo-transfection and differentiation of pluripotent stem cells via near infrared (NIR) femtosecond (fs) laser pulses with minimum compromise to their viability. Therefore, in this study the influence of using different fs laser wavelengths on optical stem cell transfection and differentiation is investigated. A potassium titanyl phosphate (KTP) crystal was employed in frequency doubling a 1064 nm fs laser beam. The newly generated 532 nm fs pulsed beam was then utilized for the first time in transient photo-transfection of ES-E14TG2a mouse embryonic stem (mES) cells. Compared to using 1064 nm fs pulses which non-invasively introduce plasmid DNA and other macromolecules into mES cells, our results showed a significant decline in the photo-transfection efficiency following transfecting with a pulsed fs visible green beam.

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.

Near infrared and extreme ultraviolet light pulses induced modifications of ultrathin Co films

NASA Astrophysics Data System (ADS)

Kisielewski, Jan; Sveklo, Iosif; Kurant, Zbigniew; Bartnik, Andrzej; Jakubowski, Marcin; Dynowska, ElŻbieta; Klinger, Dorota; Sobierajski, Ryszard; Wawro, Andrzej; Maziewski, Andrzej

2017-05-01

We report on comparative study of magnetic properties of Pt/Co/Pt trilayers after irradiation with different light sources. Ultrathin Pt/Co/Pt films were deposited by molecular beam epitaxy technique on sapphire (0001) substrates. Pt buffers were grown at room temperature (RT) and at 750°C (high temperature, HT). The samples were irradiated with a broad range of light energy densities (up to film ablation) using two different single pulse irradiation sources: (i) 40 fs laser with 800 nm wavelength and (ii) 3 ns laser-plasma source of extreme ultraviolet (EUV) with the most intense emission centered at 11 nm. The light pulse-driven irreversible structural and as a consequence, magnetic modifications were investigated using polar magneto-optical Kerr effect-based microscopy and atomic and magnetic force microscopies. The light pulse-induced transitions from the out-of-plane to in-plane magnetization state, and from in-plane to out-of-plane, were observed for both types of samples and irradiation methods. Diagrams of the magnetic states as a function of the Co layer thickness and energy density of the absorbed femtosecond pulses were constructed for the samples with both the RT and HT buffers. The energy density range responsible for the creation of the out-of-plane magnetization was wider for the HT than for RT buffer. This is correlated with the higher (for HT) crystalline quality and much smoother Pt/Co surface deduced from the X-ray diffraction studies. Submicrometer magnetic domains were observed in the irradiated region while approaching the out-of-plane magnetization state. Changes of Pt/Co/Pt structures are discussed for both types of light pulses.

Mechanisms of Laser-Induced Dissection and Transport of Histologic Specimens

PubMed Central

Vogel, Alfred; Lorenz, Kathrin; Horneffer, Verena; Hüttmann, Gereon; von Smolinski, Dorthe; Gebert, Andreas

2007-01-01

Rapid contact- and contamination-free procurement of histologic material for proteomic and genomic analysis can be achieved by laser microdissection of the sample of interest followed by laser-induced transport (laser pressure catapulting). The dynamics of laser microdissection and laser pressure catapulting of histologic samples of 80 μm diameter was investigated by means of time-resolved photography. The working mechanism of microdissection was found to be plasma-mediated ablation initiated by linear absorption. Catapulting was driven by plasma formation when tightly focused pulses were used, and by photothermal ablation at the bottom of the sample when defocused pulses producing laser spot diameters larger than 35 μm were used. With focused pulses, driving pressures of several hundred MPa accelerated the specimen to initial velocities of 100–300 m/s before they were rapidly slowed down by air friction. When the laser spot was increased to a size comparable to or larger than the sample diameter, both driving pressure and flight velocity decreased considerably. Based on a characterization of the thermal and optical properties of the histologic specimens and supporting materials used, we calculated the evolution of the heat distribution in the sample. Selected catapulted samples were examined by scanning electron microscopy or analyzed by real-time reverse-transcriptase polymerase chain reaction. We found that catapulting of dissected samples results in little collateral damage when the laser pulses are either tightly focused or when the laser spot size is comparable to the specimen size. By contrast, moderate defocusing with spot sizes up to one-third of the specimen diameter may involve significant heat and ultraviolet exposure. Potential side effects are maximal when samples are catapulted directly from a glass slide without a supporting polymer foil. PMID:17766336

Collisional Removal of OH (X (sup 2)Pi, nu=7) by O2, N2, CO2, and N2O

NASA Technical Reports Server (NTRS)

Knutsen, Karen; Dyer, Mark J.; Copeland, Richard A.

1996-01-01

Collisional removal rate constants for the OH (X 2PI, nu = 7) radical are measured for the colliders O2, CO2, and N2O, and an upper limit is established for N2. OH(nu = 4) molecules, generated in a microwave discharge flow cell by the reaction of hydrogen atoms with ozone, are excited to v = 7 by the output of a pulsed infrared laser via direct vibrational overtone excitation. The temporal evolution of the P = 7 population is probed as a function of the collider gas partial pressure by a time-delayed pulsed ultraviolet laser. Fluorescence from the B 21 + state is detected in the visible spectral region.

Real-time detection of S(1D2) photofragments produced from the 1B2(1Σu+) state of CS2 by vacuum ultraviolet photoelectron imaging using 133 nm probe pulses

NASA Astrophysics Data System (ADS)

Horio, Takuya; Spesyvtsev, Roman; Furumido, Yu; Suzuki, Toshinori

2017-07-01

Ultrafast photodissociation dynamics from the 1B2(1Σu+) state of CS2 are studied by time-resolved photoelectron imaging using the fourth (4ω, 198 nm) and sixth (6ω, 133 nm) harmonics of a femtosecond Ti:sapphire laser. The 1B2 state of CS2 was prepared with the 4ω pulses, and subsequent dynamics were probed using the 6ω vacuum ultraviolet (VUV) pulses. The VUV pulses enabled real-time detection of S(1D2) photofragments, produced via CS2*(1B2(1Σu+)) → CS(X 1Σ+) + S(1D2). The photoionization signal of dissociating CS2*(1B2(1Σu+)) molecules starts to decrease at about 100 fs, while the S(1D2) fragments appear with a finite (ca. 400 fs) delay time after the pump pulse. Also discussed is the configuration interaction of the 1B2(1Σu+) state based on relative photoionization cross-sections to different cationic states.

Two-bunch operation with ns temporal separation at the FERMI FEL facility

NASA Astrophysics Data System (ADS)

Penco, Giuseppe; Allaria, Enrico; Bassanese, Silvano; Cinquegrana, Paolo; Cleva, Stefano; Danailov, Miltcho B.; Demidovich, Alexander; Ferianis, Mario; Gaio, Giulio; Giannessi, Luca; Masciovecchio, Claudio; Predonzani, Mauro; Rossi, Fabio; Roussel, Eleonore; Spampinati, Simone; Trovò, Mauro

2018-05-01

In the last decade, a continuous effort has been dedicated to extending the capabilities of existing free-electron lasers (FELs) operating in the x-ray and vacuum ultraviolet regimes. In this framework, the generation of two-color (or multi-color) temporally separated FEL pulses, has paved the way to new x-ray pump and probe experiments and several two-color two-pulse schemes have been implemented at the main facilities, but with a generally limited time-separation between the pulses, from 0 to few hundreds of fs. This limitation may be overcome by generating light with two independent electron bunches, temporally separated by integral multiples of the radio-frequency period. This solution was investigated at FERMI, measurements and characterization of this two-bunch mode of operation are presented, including trajectory control, impact of longitudinal and transverse wakefields, manipulation of the longitudinal phase space and finally a demonstration of suitability of the scheme to provide extreme ultraviolet light by using both bunches.

Generation of coherent magnons in NiO stimulated by EUV pulses from a seeded free-electron laser

NASA Astrophysics Data System (ADS)

Simoncig, A.; Mincigrucci, R.; Principi, E.; Bencivenga, F.; Calvi, A.; Foglia, L.; Kurdi, G.; Matruglio, A.; Dal Zilio, S.; Masciotti, V.; Lazzarino, M.; Masciovecchio, C.

2017-12-01

The full comprehension of magnetic phenomena at the femtosecond (fs) time scale is of high demand for current material science and technology. Here we report the observation of coherent collective modes in the antiferromagnetic insulator nickel oxide (NiO) identified by a frequency of 0.86 THz, which matches the expected out-of-plane single-mode magnon resonance. Such collective excitations are inelastically stimulated by extreme ultraviolet (EUV) pulses delivered by a seeded free-electron laser (FEL) and subsequently revealed probing the transient optical activity of NiO looking at the Faraday effect. Moreover, the unique capability of the employed FEL source to deliver circularly polarized pulses allows us to demonstrate optomagnetic control of such collective modes at EUV photon energies. These results may set a starting point for future investigations of magnetic materials at time scales comparable or faster than those typical of exchange interactions.

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.

Coherent ultra-violet to near-infrared generation in silica ridge waveguides

PubMed Central

Yoon Oh, Dong; Yang, Ki Youl; Fredrick, Connor; Ycas, Gabriel; Diddams, Scott A.; Vahala, Kerry J.

2017-01-01

Short duration, intense pulses of light can experience dramatic spectral broadening when propagating through lengths of optical fibre. This continuum generation process is caused by a combination of nonlinear optical effects including the formation of dispersive waves. Optical analogues of Cherenkov radiation, these waves allow a pulse to radiate power into a distant spectral region. In this work, efficient and coherent dispersive wave generation of visible to ultraviolet light is demonstrated in silica waveguides on a silicon chip. Unlike fibre broadeners, the arrays provide a wide range of emission wavelength choices on a single, compact chip. This new capability is used to simplify offset frequency measurements of a mode-locked frequency comb. The arrays can also enable mode-locked lasers to attain unprecedented tunable spectral reach for spectroscopy, bioimaging, tomography and metrology. PMID:28067233

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

High average power, highly brilliant laser-produced plasma source for soft X-ray spectroscopy.

PubMed

Mantouvalou, Ioanna; Witte, Katharina; Grötzsch, Daniel; Neitzel, Michael; Günther, Sabrina; Baumann, Jonas; Jung, Robert; Stiel, Holger; Kanngiesser, Birgit; Sandner, Wolfgang

2015-03-01

In this work, a novel laser-produced plasma source is presented which delivers pulsed broadband soft X-radiation in the range between 100 and 1200 eV. The source was designed in view of long operating hours, high stability, and cost effectiveness. It relies on a rotating and translating metal target and achieves high stability through an on-line monitoring device using a four quadrant extreme ultraviolet diode in a pinhole camera arrangement. The source can be operated with three different laser pulse durations and various target materials and is equipped with two beamlines for simultaneous experiments. Characterization measurements are presented with special emphasis on the source position and emission stability of the source. As a first application, a near edge X-ray absorption fine structure measurement on a thin polyimide foil shows the potential of the source for soft X-ray spectroscopy.

Total internal reflection-based side-pumping configuration for terawatt ultraviolet amplifier and laser oscillator development

NASA Astrophysics Data System (ADS)

Cadatal-Raduban, Marilou; Pham, Minh Hong; Pham, Duong Van; Bui, Duong Thi Thuy; Yamanoi, Kohei; Takeda, Kohei; Empizo, Melvin John F.; Mui, Luong Viet; Shimizu, Toshihiko; Nguyen, Hung Dai; Sarukura, Nobuhiko; Fukuda, Tsuguo

2018-06-01

A two-side-pumping scheme that is based on total internal reflection in a diamond-cut Ce3+:LiCaAlF6 crystal suitable for the development of an ultraviolet laser and femtosecond amplifier system is proposed. Experimental fluorescence images and lasing results that demonstrate total internal reflection of the excitation beam using this diamond-cut crystal are presented. Calculations for the optimized crystal geometry that facilitate high extraction efficiency and homogeneity of the absorbed excitation beam are also discussed. About 50% increase in extraction efficiency compared to previously reported chirped-pulse femtosecond ultraviolet amplifier operating at 50-GW peak power is expected using this total internal reflection-based two-side-pumping configuration and a diamond-cut Ce3+:LiCaAlF6 crystal with a geometry of {φ _1} = 103°, {φ _2} = {φ _4} = 82°, {φ _3} = 93°, a length of 1.23 cm, a height of 2 cm, and an absorption coefficient of 1.5 cm-1. Our results can be used as a guide during the crystal growth process by providing the appropriate crystal geometry and size for a particular absorption coefficient to achieve high extraction efficiency. With the appropriate crystal combined with multiple-beam pumping afforded by the side-pumping scheme, the development of an all-solid-state ultraviolet laser operating at terawatt level would be within reach.

Effect of attochirp on attosecond streaking time delay in photoionization of atoms

NASA Astrophysics Data System (ADS)

Goldsmith, C.; Jaroń-Becker, A.; Becker, A.

2018-01-01

We present a theoretical analysis of the effect of the attochirp on the streaking time delay, intrinsic to photoionization of an atom by an attosecond laser pulse at extreme ultraviolet wavelengths superposed by a femtosecond streaking pulse. To this end, we determine the expectation value of the delay in a chirped pulse using a recently developed model formula. Results of our calculations show that the attochirp can be relevant for photoemission from the 3p shell in argon atom at frequencies near the Cooper minimum, while it is negligible if the photoionization cross section as a function of frequency varies smoothly.

Fast neutron production from lithium converters and laser driven protons

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

Storm, M.; Jiang, S.; Wertepny, D.

2013-05-15

Experiments to generate neutrons from the {sup 7}Li(p,n){sup 7}Be reaction with 60 J, 180 fs laser pulses have been performed at the Texas Petawatt Laser Facility at the University of Texas at Austin. The protons were accelerated from the rear surface of a thin target membrane using the target-normal-sheath-acceleration mechanism. The neutrons were generated in nuclear reactions caused by the subsequent proton bombardment of a pure lithium foil of natural isotopic abundance. The neutron energy ranged up to 2.9 MeV. The total yield was estimated to be 1.6 × 10{sup 7} neutrons per steradian. An extreme ultra-violet light camera, usedmore » to image the target rear surface, correlated variations in the proton yield and peak energy to target rear surface ablation. Calculations using the hydrodynamics code FLASH indicated that the ablation resulted from a laser pre-pulse of prolonged intensity. The ablation severely limited the proton acceleration and neutron yield.« less

A 490 W transversely excited atmospheric CO2 spark gap laser with added H2

NASA Astrophysics Data System (ADS)

Zand, M.; Koushki, A. M.; Neshati, R.; Kia, B.; Khorasani, K.

2018-02-01

In this paper we present a new design for a high pulse repetition rate transversely excited atmospheric CO2 laser with ultraviolet pre-ionization. A new method of fast thyristor capacitor charging and discharging by a spark gap is used. The effect of H2 gas addition on the output and stability of a transversely excited atmospheric laser operating with a basic mixture of CO2, N2 and He is investigated. The output power was increased by adding H2 to the gas mixture ratio of CO2:N2:He:H2  =  1:1:8:0.5 at total pressure of 850 mbar. An average power of 490 W at 110 Hz with 4.5 J per pulse was obtained. The laser efficiency was 11.2% and oxygen gas was used in the spark gap for electron capture to reduce the recovery time and increase the repetition rate.

A clinical review of phototherapy for psoriasis.

PubMed

Zhang, Ping; Wu, Mei X

2018-01-01

Psoriasis is an autoimmune inflammatory skin disease. In the past several decades, phototherapy has been widely used to treat stable psoriatic lesions, including trunk, scalp, arms and legs, and partial nail psoriasis. A variety of light/lasers with different mechanisms of action have been developed for psoriasis including ultraviolet B (UVB), psoralen ultraviolet A (PUVA), pulsed dye laser (PDL), photodynamic therapy (PDT), intense pulsed light (IPL), light-emitting diodes (LED), and so on. Because light/laser each has specific therapeutic and adverse effects, it is important to adequately choose the sources and parameters in management of psoriasis with different pathogenic sites, severities, and duration of the disorder. This review aims at providing most updated clinic information to physicians about how to select light/laser sources and individual therapeutic regimens. To date, UV light is primarily for stable plaque psoriasis and PDL for topical psoriatic lesions with small area, both of which are safe and effective. On the other hand, PUVA has better curative effects than UVB for managing refractory psoriasis plaques, if its side effects can be better controlled. PDL provides optimal outcomes on nail psoriasis compared with other lasers. Although the trails of low-level light/laser therapy (LLLT) are still small, the near infrared (NIR) and visible red light with low energy show promise for treating psoriasis due to its strong penetration and encouraging photobiomodulation. IPL is rarely reported for psoriasis treatment, but PDT-IPL has been found to offer a moderate effect on nail psoriasis. In brief, various phototherapies have been used either in different combinations or as monotherapy. The modality has become a mainstay in the treatment of mild-to-moderate psoriasis without systemic adverse events in today's clinical practice.

Diode-pumped continuous-wave and femtosecond Cr:LiCAF lasers with high average power in the near infrared, visible and near ultraviolet.

PubMed

Demirbas, Umit; Baali, Ilyes; Acar, Durmus Alp Emre; Leitenstorfer, Alfred

2015-04-06

We demonstrate continuous-wave (cw), cw frequency-doubled, cw mode-locked and Q-switched mode-locked operation of multimode diode-pumped Cr:LiCAF lasers with record average powers. Up to 2.54 W of cw output is obtained around 805 nm at an absorbed pump power of 5.5 W. Using intracavity frequency doubling with a BBO crystal, 0.9 W are generated around 402 nm, corresponding to an optical-to-optical conversion efficiency of 12%. With an intracavity birefringent tuning plate, the fundamental and frequency-doubled laser output is tuned continuously in a broad wavelength range from 745 nm to 885 nm and from 375 to 440 nm, respectively. A saturable Bragg reflector is used to initiate and sustain mode locking. In the cw mode-locked regime, the Cr:LiCAF laser produces 105-fs long pulses near 810 nm with an average power of 0.75 W. The repetition rate is 96.4 MHz, resulting in pulse energies of 7.7 nJ and peak powers of 65 kW. In Q-switched mode-locked operation, pulses with energies above 150 nJ are generated.

Picosecond laser ablation of poly-L-lactide: Effect of crystallinity on the material response

NASA Astrophysics Data System (ADS)

Ortiz, Rocío; Quintana, Iban; Etxarri, Jon; Lejardi, Ainhoa; Sarasua, Jose-Ramon

2011-11-01

The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation showed a reduction in the energy ablation threshold as the degree of crystallinity increased, probably related to photomechanical effects involved in laser ablation with ultra-short pulses and the lower stress accommodation behavior of semicrystalline polymers. In particular, cooperative chain motions are impeded by the higher degree of crystallinity, showing fragile mechanical behavior and lower energy dissipation. The experimental results on ablation rate versus laser energy showed that UV laser ablation on semicrystalline PLLA was more efficient than the visible ablation, i.e., it exhibits higher etch rates over a wide range of pulse energy conditions. These results were interpreted in terms of photo-thermal and photo-chemical response of polymers as a function of material micro-structure and incident laser wavelength. High quality micro-grooves were produced in amorphous PLLA, reveling the potential of ultra-fast laser processing technique in the field of micro-structuring biocompatible and biodegradable polymers for biomedical applications.

Performance of 100-W 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

2015-08-01

At Gigaphoton Inc., we have developed unique and original technologies for a carbon dioxide laser-produced tin plasma extreme ultraviolet (CO2-Sn-LPP EUV) light source, which is the most promising solution for high-power high-volume manufacturing (HVM) EUV lithography at 13.5 nm. Our unique technologies include the combination of a pulsed CO2 laser with Sn droplets, the application of dual-wavelength laser pulses for Sn droplet conditioning, and subsequent EUV generation and magnetic field mitigation. Theoretical and experimental data have clearly shown the advantage of our proposed strategy. Currently, we are developing the first HVM light source, `GL200E'. This HVM light source will provide 250-W EUV power based on a 20-kW level pulsed CO2 laser. The preparation of a high average-power CO2 laser (more than 20 kW output power) has been completed in cooperation with Mitsubishi Electric Corporation. Recently, we achieved 140 W at 50 kHz and 50% duty cycle operation as well as 2 h of operation at 100 W of power level. Further improvements are ongoing. We will report the latest status and the challenge to reach stable system operation of more than 100 W at about 4% conversion efficiency with 20-μm droplets and magnetic mitigation.

An innovative Yb-based ultrafast deep ultraviolet source for time-resolved photoemission experiments

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

Boschini, F.; Hedayat, H.; Dallera, C.

2014-12-15

Time- and angle-resolved photoemission spectroscopy is a powerful technique to study ultrafast electronic dynamics in solids. Here, an innovative optical setup based on a 100-kHz Yb laser source is presented. Exploiting non-collinear optical parametric amplification and sum-frequency generation, ultrashort pump (hν = 1.82 eV) and ultraviolet probe (hν = 6.05 eV) pulses are generated. Overall temporal and instrumental energy resolutions of, respectively, 85 fs and 50 meV are obtained. Time- and angle-resolved measurements on BiTeI semiconductor are presented to show the capabilities of the setup.

Strong Field-Induced Frequency Conversion of Laser Radiation in Plasma Plumes: Recent Achievements

PubMed Central

Ganeev, R. A.

2013-01-01

New findings in plasma harmonics studies using strong laser fields are reviewed. We discuss recent achievements in the growth of the efficiency of coherent extreme ultraviolet (XUV) radiation sources based on frequency conversion of the ultrashort pulses in the laser-produced plasmas, which allowed for the spectral and structural studies of matter through the high-order harmonic generation (HHG) spectroscopy. These studies showed that plasma HHG can open new opportunities in many unexpected areas of laser-matter interaction. Besides being considered as an alternative method for generation of coherent XUV radiation, it can be used as a powerful tool for various spectroscopic and analytical applications. PMID:23864818

A passion for precision

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

None

2010-05-19

For more than three decades, the quest for ever higher precision in laser spectroscopy of the simple hydrogen atom has inspired many advances in laser, optical, and spectroscopic techniques, culminating in femtosecond laser optical frequency combs  as perhaps the most precise measuring tools known to man. Applications range from optical atomic clocks and tests of QED and relativity to searches for time variations of fundamental constants. Recent experiments are extending frequency comb techniques into the extreme ultraviolet. Laser frequency combs can also control the electric field of ultrashort light pulses, creating powerful new tools for the emerging field of attosecondmore » science.Organiser(s): L. Alvarez-Gaume / PH-THNote: * Tea & coffee will be served at 16:00.« less

Ultraviolet germicidal efficacy as a function of pulsed radiation parameters studied by spore film dosimetry.

PubMed

Bauer, Stefan; Holtschmidt, Hans; Ott, Günter

2018-01-01

Disinfection by pulsed ultraviolet (UV) radiation is a commonly used method, e.g. in industry or medicine and can be carried out either with lasers or broadband UV radiation sources. Detrimental effects to biological materials depending on parameters such as pulse duration τ or pulse repetition frequency f p are well-understood for pulsed coherent UV radiation, however, relatively little is known for its incoherent variant. Therefore, within this work, it is the first time that disinfection rates of pulsed and continuous (cw) incoherent UV radiation studied by means of spore film dosimetry are presented, compared with each other, and in a second step further investigated regarding two pulse parameters. After analyzing the dynamic range of the Bacillus subtilis spore films with variable cw radiant exposures H=5-100Jm -2 a validation of the Bunsen-Roscoe law revealed its restricted applicability and a 28% enhanced detrimental effect of pulsed compared to cw incoherent UV radiation. A radiant exposure H=50Jm -2 and an irradiance E=0.5Wm -2 were found to be suitable parameters for an analysis of the disinfection rate as a function of τ=0.5-10ms and f p =25-500Hz unveiling that shorter pulses and lower frequencies inactivate more spores. Finally, the number of applied pulses as well as the experiment time were considered with regard to spore film disinfection. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

National Ignition Facility Comes to Life

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

Moses, E

2003-09-01

First conceived of nearly 15 years ago, the National Ignition Facility (NIF) is up and running and successful beyond almost everyone's expectations. During commissioning of the first four laser beams, the laser system met design specifications for everything from beam quality to energy output. NIF will eventually have 192 laser beams. Yet with just 2% of its final beam configuration complete, NIF has already produced the highest energy laser shots in the world. In July, laser shots in the infrared wavelength using four beams produced a total of 26.5 kilojoules of energy per beam, not only meeting NIF's design energymore » requirement of 20 kilojoules per beam but also exceeding the energy of any other infrared laser beamline. In another campaign, NIF produced over 11.4 kilojoules of energy when the infrared light was converted to green light. An earlier performance campaign of laser light that had been frequency converted from infrared to ultraviolet really proved NIF's mettle. Over 10.4 kilojoules of ultraviolet energy were produced in about 4 billionths of a second. If all 192 beamlines were to operate at these levels, over 2 megajoules of energy would result. That much energy for the pulse duration of several nanoseconds is about 500 trillion watts of power, more than 500 times the US peak generating power.« less

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).

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.

Experimental station for ultrafast extreme ultraviolet spectroscopy for non-equilibrium dynamics in warm dense matter

NASA Astrophysics Data System (ADS)

Lee, Jong-won; Geng, Xiaotao; Jung, Jae Hyung; Cho, Min Sang; Yang, Seong Hyeok; Jo, Jawon; Lee, Chang-lyoul; Cho, Byoung Ick; Kim, Dong-Eon

2018-07-01

Recent interest in highly excited matter generated by intense femtosecond laser pulses has led to experimental methods that directly investigate ultrafast non-equilibrium electronic and structural dynamics. We present a tabletop experimental station for the extreme ultraviolet (EUV) spectroscopy used to trace L-edge dynamics in warm dense aluminum with a temporal resolution of a hundred femtoseconds. The system consists of the EUV probe generation part via a high-order harmonic generation process of femtosecond laser pulses with atomic clusters, a beamline with high-throughput optics and a sample-refreshment system of nano-foils utilizing the full repetition rate of the probe, and a flat-field EUV spectrograph. With the accumulation of an order of a hundred shots, a clear observation of the change in the aluminum L-shell absorption was achieved with a temporal resolution of 90 fs in a 600-fs window. The signature of a non-equilibrium electron distribution over a 10-eV range and its evolution to a 1-eV Fermi distribution are observed. This demonstrates the capability of this apparatus to capture the non-equilibrium electron-hole dynamics in highly excited warm dense matter conditions.

Single shot polarization characterization of XUV FEL pulses from crossed polarized undulators

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

Ferrari, E.; Allaria, E.; Buck, J.

Polarization control is a key feature of light generated by short-wavelength free-electron lasers. In this work, we report the first experimental characterization of the polarization properties of an extreme ultraviolet high gain free-electron laser operated with crossed polarized undulators. We research the average degree of polarization and the shot-to-shot stability and we analyze aspects such as existing possibilities for controlling and switching the polarization state of the emitted light. The results are in agreement with predictions based on Gaussian beams propagation.

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)

Single shot polarization characterization of XUV FEL pulses from crossed polarized undulators

DOE PAGES

Ferrari, E.; Allaria, E.; Buck, J.; ...

2015-08-28

Polarization control is a key feature of light generated by short-wavelength free-electron lasers. In this work, we report the first experimental characterization of the polarization properties of an extreme ultraviolet high gain free-electron laser operated with crossed polarized undulators. We research the average degree of polarization and the shot-to-shot stability and we analyze aspects such as existing possibilities for controlling and switching the polarization state of the emitted light. The results are in agreement with predictions based on Gaussian beams propagation.

Erosion resistant nozzles for laser plasma extreme ultraviolet (EUV) sources

DOEpatents

Kubiak, Glenn D.; Bernardez, II, Luis J.

2000-01-04

A gas nozzle having an increased resistance to erosion from energetic plasma particles generated by laser plasma sources. By reducing the area of the plasma-facing portion of the nozzle below a critical dimension and fabricating the nozzle from a material that has a high EUV transmission as well as a low sputtering coefficient such as Be, C, or Si, it has been shown that a significant reduction in reflectance loss of nearby optical components can be achieved even after exposing the nozzle to at least 10.sup.7 Xe plasma pulses.

Time-resolved lidar fluorosensor for sea pollution detection

NASA Technical Reports Server (NTRS)

Ferrario, A.; Pizzolati, P. L.; Zanzottera, E.

1986-01-01

A contemporary time and spectral analysis of oil fluorescence is useful for the detection and the characterization of oil spills on the sea surface. Nevertheless the fluorosensor lidars, which were realized up to now, have only partial capability to perform this double analysis. The main difficulties are the high resolution required (of the order of 1 nanosecond) and the complexity of the detection system for the recording of a two-dimensional matrix of data for each laser pulse. An airborne system whose major specifications were: time range, 30 to 75 ns; time resolution, 1 ns; spectral range, 350 to 700 nm; and spectral resolution, 10 nm was designed and constructed. The designed system of a short pulse ultraviolet laser source and a streak camera based detector are described.

Attosecond nonlinear optics using gigawatt-scale isolated attosecond pulses

PubMed Central

Takahashi, Eiji J.; Lan, Pengfei; Mücke, Oliver D.; Nabekawa, Yasuo; Midorikawa, Katsumi

2013-01-01

High-energy isolated attosecond pulses required for the most intriguing nonlinear attosecond experiments as well as for attosecond-pump/attosecond-probe spectroscopy are still lacking at present. Here we propose and demonstrate a robust generation method of intense isolated attosecond pulses, which enable us to perform a nonlinear attosecond optics experiment. By combining a two-colour field synthesis and an energy-scaling method of high-order harmonic generation, the maximum pulse energy of the isolated attosecond pulse reaches as high as 1.3 μJ. The generated pulse with a duration of 500 as, as characterized by a nonlinear autocorrelation measurement, is the shortest and highest-energy pulse ever with the ability to induce nonlinear phenomena. The peak power of our tabletop light source reaches 2.6 GW, which even surpasses that of an extreme-ultraviolet free-electron laser. PMID:24158092

Finesse of transparent tissue cutting by ultrafast lasers at various wavelengths.

PubMed

Wang, Jenny; Schuele, Georg; Palanker, Daniel

2015-01-01

Transparent ocular tissues, such as the cornea and crystalline lens, can be ablated or dissected using short-pulse lasers. In refractive and cataract surgeries, the cornea, lens, and lens capsule can be cut by producing dielectric breakdown in the focus of a near-infrared (IR) femtosecond laser, which results in explosive vaporization of the interstitial water, causing mechanical rupture of the surrounding tissue. Here, we compare the texture of edges of lens capsule cut by femtosecond lasers with IR and ultraviolet (UV) wavelengths and explore differences in interactions of these lasers with biological molecules. Scanning electron microscopy indicates that a 400-nm laser is capable of producing very smooth cut edges compared to 800 or 1030 nm at a similar focusing angle. Using gel electrophoresis and liquid chromatography/mass spectrometry, we observe laser-induced nonlinear breakdown of proteins and polypeptides by 400-nm femtosecond pulses above and below the dielectric breakdown threshold. On the other hand, 800-nm femtosecond lasers do not produce significant dissociation even above the threshold of dielectric breakdown. However, despite this additional interaction of UV femtosecond laser with proteins, we determine that efficient cutting requires plasma-mediated bubble formation and that remarkably smooth edges are the result of reduced thresholds and smaller focal volume.

Ultraviolet electroluminescence from hetero p-n junction between a single ZnO microsphere and p-GaN thin film.

PubMed

Tetsuyama, Norihiro; Fusazaki, Koshi; Mizokami, Yasuaki; Shimogaki, Tetsuya; Higashihata, Mitsuhiro; Nakamura, Daisuke; Okada, Tatsuo

2014-04-21

We report ultraviolet electroluminescence from a hetero p-n junction between a single ZnO microsphere and p-GaN thin film. ZnO microspheres, which have high crystalline quality, have been synthesized by ablating a ZnO sintered target. It was found that synthesized ZnO microspheres had a high-optical property and exhibit the laser action in the whispering gallery mode under pulsed optical pumping. A hetero p-n junction was formed between the single ZnO microsphere/ p-GaN thin film, and a good rectifying property with a turn-on voltage of approximately 6 V was observed in I-V characteristic across the junction. Ultraviolet and visible electroluminescence were observed under forward bias.

A compact OPO/SFG laser for ultraviolet biological sensing

NASA Astrophysics Data System (ADS)

Tiihonen, Mikael; Pasiskevicius, Valdas; Laurell, Fredrik; Jonsson, Per; Lindgren, Mikael

2004-07-01

A compact parametric oscillator (OPO) with intracavity sum-frequency generation (SFG) to generate 293 nm UV laser irradiation, was developed. The OPO/SFG device was pumped by a 100 Hz Nd:YAG laser (1064 nm) of own design, including subsequent second harmonic generation (SHG) in an external periodically poled KTiOPO4 (KTP) crystal. The whole system could be used to deliver more than 30 μJ laser irradiation per pulse (100 Hz) at 293 nm. The UV laser light was introduced in an optical fiber attached to a sample compartment allowing detection of fluorescence emission using a commercial spectrometer. Aqueous samples containing biomolecules (ovalbumin) or bacteria spores (Bacillus subtilis) were excited by the UV-light at 293 nm resulting in strong fluorescence emission in the range 325 - 600 nm.

A Solid State Ultraviolet Lasers Based on Cerium-Doped LiCaAIF(sub 6) Crystal Resonator

NASA Technical Reports Server (NTRS)

Yu, Nan; Le, Thanh; Schowalter, Steven J.; Rellergert, Wade; Jeet, Justin; Lin, Guoping; Hudson, Eric

2012-01-01

We report the first demonstration of a UV laser using a high-Q whispering gallery mode (WGM) resonator of Ce+: LiCaAlF6. We show that WGM resonators from LiCaAlF6 can achieve a Q of 2.6 x 10(sup 7) at UV. We demonstrated a UV laser at 290 nm with a pulsed pump laser at 266 nm. The experiments showed the low pump threshold intensity of 7.5 x 10(sup 9) W/m(sup 2) and slope efficiency of 25%. We have also observed lasing delay dynamics. These results are consistent with our modeling and theoretical estimates, and pave the way for a low threshold cw UV laser using WGM resonator cavity.

Advances in 193 nm excimer lasers for mass spectrometry applications

NASA Astrophysics Data System (ADS)

Delmdahl, Ralph; Esser, Hans-Gerd; Bonati, Guido

2016-03-01

Ongoing progress in mass analysis applications such as laser ablation inductively coupled mass spectrometry of solid samples and ultraviolet photoionization mediated sequencing of peptides and proteins is to a large extent driven by ultrashort wavelength excimer lasers at 193 nm. This paper will introduce the latest improvements achieved in the development of compact high repetition rate excimer lasers and elaborate on the impact on mass spectrometry instrumentation. Various performance and lifetime measurements obtained in a long-term endurance test over the course of 18 months will be shown and discussed in view of the laser source requirements of different mass spectrometry tasks. These sampling type applications are served by excimer lasers delivering pulsed 193 nm output of several mJ as well as fast repetition rates which are already approaching one Kilohertz. In order to open up the pathway from the laboratory to broader market industrial use, sufficient component lifetimes and long-term stable performance behavior have to be ensured. The obtained long-term results which will be presented are based on diverse 193 nm excimer laser tube improvements aiming at e.g. optimizing the gas flow dynamics and have extended the operational life the laser tube for the first time over several billion pulses even under high duty-cycle conditions.

A sensitive EUV Schwarzschild microscope for plasma studies with sub-micrometer resolution

DOE PAGES

Zastrau, U.; Rodel, C.; Nakatsutsumi, M.; ...

2018-02-05

We present an extreme ultraviolet (EUV) microscope using a Schwarzschild objective which is optimized for single-shot sub-micrometer imaging of laser-plasma targets. The microscope has been designed and constructed for imaging the scattering from an EUV-heated solid-density hydrogen jet. Here, imaging of a cryogenic hydrogen target was demonstrated using single pulses of the free-electron laser in Hamburg (FLASH) free-electron laser at a wavelength of 13.5 nm. In a single exposure, we observe a hydrogen jet with ice fragments with a spatial resolution in the sub-micrometer range. In situ EUV imaging is expected to enable novel experimental capabilities for warm dense mattermore » studies of micrometer-sized samples in laser-plasma experiments.« less

A sensitive EUV Schwarzschild microscope for plasma studies with sub-micrometer resolution

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

Zastrau, U.; Rodel, C.; Nakatsutsumi, M.

We present an extreme ultraviolet (EUV) microscope using a Schwarzschild objective which is optimized for single-shot sub-micrometer imaging of laser-plasma targets. The microscope has been designed and constructed for imaging the scattering from an EUV-heated solid-density hydrogen jet. Here, imaging of a cryogenic hydrogen target was demonstrated using single pulses of the free-electron laser in Hamburg (FLASH) free-electron laser at a wavelength of 13.5 nm. In a single exposure, we observe a hydrogen jet with ice fragments with a spatial resolution in the sub-micrometer range. In situ EUV imaging is expected to enable novel experimental capabilities for warm dense mattermore » studies of micrometer-sized samples in laser-plasma experiments.« less

Ultra-fast switching of light by absorption saturation in vacuum ultra-violet region.

PubMed

Yoneda, Hitoki; Inubushi, Yuichi; Tanaka, Toshihiro; Yamaguchi, Yuta; Sato, Fumiya; Morimoto, Shunsuke; Kumagai, Taisuke; Nagasono, Mitsuru; Higashiya, Atsushi; Yabashi, Makina; Ishikawa, Tetsuya; Ohashi, Haruhiko; Kimura, Hiroaki; Kitamura, Hikaru; Kodama, Ryosuke

2009-12-21

Advances in free electron lasers producing high energy photons [Nat. Photonics 2(9), 555-559 (2008)] are expected to open up a new science of nonlinear optics of high energy photons. Specifically, lasers of photon energy higher than the plasma frequency of a metal can show new interaction features because they can penetrate deeply into metals without strong reflection. Here we show the observation of ultra-fast switching of vacuum ultra-violet (VUV) light caused by saturable absorption of a solid metal target. A strong gating is observed at energy fluences above 6J/cm2 at wavelength of 51 nm with tin metal thin layers. The ratio of the transmission at high intensity to low intensity is typically greater than 100:1. This means we can design new nonlinear photonic devices such as auto-correlator and pulse slicer for the VUV region.

Carcinogenic damage to deoxyribonucleic acid is induced by near-infrared laser pulses in multiphoton microscopy via combination of two- and three-photon absorption

NASA Astrophysics Data System (ADS)

Nadiarnykh, Oleg; Thomas, Giju; Van Voskuilen, Johan; Sterenborg, Henricus J. C. M.; Gerritsen, Hans C.

2012-11-01

Nonlinear optical imaging modalities (multiphoton excited fluorescence, second and third harmonic generation) applied in vivo are increasingly promising for clinical diagnostics and the monitoring of cancer and other disorders, as they can probe tissue with high diffraction-limited resolution at near-infrared (IR) wavelengths. However, high peak intensity of femtosecond laser pulses required for two-photon processes causes formation of cyclobutane-pyrimidine-dimers (CPDs) in cellular deoxyribonucleic acid (DNA) similar to damage from exposure to solar ultraviolet (UV) light. Inaccurate repair of subsequent mutations increases the risk of carcinogenesis. In this study, we investigate CPD damage that results in Chinese hamster ovary cells in vitro from imaging them with two-photon excited autofluorescence. The CPD levels are quantified by immunofluorescent staining. We further evaluate the extent of CPD damage with respect to varied wavelength, pulse width at focal plane, and pixel dwell time as compared with more pronounced damage from UV sources. While CPD damage has been expected to result from three-photon absorption, our results reveal that CPDs are induced by competing two- and three-photon absorption processes, where the former accesses UVA absorption band. This finding is independently confirmed by nonlinear dependencies of damage on laser power, wavelength, and pulse width.

Source of coherent short wavelength radiation

DOEpatents

Villa, Francesco

1990-01-01

An apparatus for producing coherent radiation ranging from X-rays to the far ultraviolet (i.e., 1 Kev to 10 eV) utilizing the Compton scattering effect. A photon beam from a laser is scattered on a high energy electron bunch from a pulse power linac. The short wavelength radiation produced by such scattering has sufficient intensity and spatial coherence for use in high resolution applications such as microscopy.

Photodissociation of aligned CH3I and C6H3F2I molecules probed with time-resolved Coulomb explosion imaging by site-selective extreme ultraviolet ionization

PubMed Central

Amini, Kasra; Savelyev, Evgeny; Brauße, Felix; Berrah, Nora; Bomme, Cédric; Brouard, Mark; Burt, Michael; Christensen, Lauge; Düsterer, Stefan; Erk, Benjamin; Höppner, Hauke; Kierspel, Thomas; Krecinic, Faruk; Lauer, Alexandra; Lee, Jason W. L.; Müller, Maria; Müller, Erland; Mullins, Terence; Redlin, Harald; Schirmel, Nora; Thøgersen, Jan; Techert, Simone; Toleikis, Sven; Treusch, Rolf; Trippel, Sebastian; Ulmer, Anatoli; Vallance, Claire; Wiese, Joss; Johnsson, Per; Küpper, Jochen; Rudenko, Artem; Rouzée, Arnaud; Stapelfeldt, Henrik; Rolles, Daniel; Boll, Rebecca

2018-01-01

We explore time-resolved Coulomb explosion induced by intense, extreme ultraviolet (XUV) femtosecond pulses from a free-electron laser as a method to image photo-induced molecular dynamics in two molecules, iodomethane and 2,6-difluoroiodobenzene. At an excitation wavelength of 267 nm, the dominant reaction pathway in both molecules is neutral dissociation via cleavage of the carbon–iodine bond. This allows investigating the influence of the molecular environment on the absorption of an intense, femtosecond XUV pulse and the subsequent Coulomb explosion process. We find that the XUV probe pulse induces local inner-shell ionization of atomic iodine in dissociating iodomethane, in contrast to non-selective ionization of all photofragments in difluoroiodobenzene. The results reveal evidence of electron transfer from methyl and phenyl moieties to a multiply charged iodine ion. In addition, indications for ultrafast charge rearrangement on the phenyl radical are found, suggesting that time-resolved Coulomb explosion imaging is sensitive to the localization of charge in extended molecules. PMID:29430482

Photodissociation of aligned CH3I and C6H3F2I molecules probed with time-resolved Coulomb explosion imaging by site-selective extreme ultraviolet ionization.

PubMed

Amini, Kasra; Savelyev, Evgeny; Brauße, Felix; Berrah, Nora; Bomme, Cédric; Brouard, Mark; Burt, Michael; Christensen, Lauge; Düsterer, Stefan; Erk, Benjamin; Höppner, Hauke; Kierspel, Thomas; Krecinic, Faruk; Lauer, Alexandra; Lee, Jason W L; Müller, Maria; Müller, Erland; Mullins, Terence; Redlin, Harald; Schirmel, Nora; Thøgersen, Jan; Techert, Simone; Toleikis, Sven; Treusch, Rolf; Trippel, Sebastian; Ulmer, Anatoli; Vallance, Claire; Wiese, Joss; Johnsson, Per; Küpper, Jochen; Rudenko, Artem; Rouzée, Arnaud; Stapelfeldt, Henrik; Rolles, Daniel; Boll, Rebecca

2018-01-01

We explore time-resolved Coulomb explosion induced by intense, extreme ultraviolet (XUV) femtosecond pulses from a free-electron laser as a method to image photo-induced molecular dynamics in two molecules, iodomethane and 2,6-difluoroiodobenzene. At an excitation wavelength of 267 nm, the dominant reaction pathway in both molecules is neutral dissociation via cleavage of the carbon-iodine bond. This allows investigating the influence of the molecular environment on the absorption of an intense, femtosecond XUV pulse and the subsequent Coulomb explosion process. We find that the XUV probe pulse induces local inner-shell ionization of atomic iodine in dissociating iodomethane, in contrast to non-selective ionization of all photofragments in difluoroiodobenzene. The results reveal evidence of electron transfer from methyl and phenyl moieties to a multiply charged iodine ion. In addition, indications for ultrafast charge rearrangement on the phenyl radical are found, suggesting that time-resolved Coulomb explosion imaging is sensitive to the localization of charge in extended molecules.

Comparative tensile strength study of the adhesion improvement of PTFE by UV photon assisted surface processing

NASA Astrophysics Data System (ADS)

Hopp, B.; Geretovszky, Zs.; Bertóti, I.; Boyd, I. W.

2002-01-01

Poly(tetrafluoroethylene) (PTFE) is notable for its non-adhesive and non-reactive properties. A number of technologies can potentially benefit from the application of PTFE, but these characteristics restrict the ability to structuring its surface. In this paper, we present results on two ultraviolet photon assisted treatments of PTFE. The originally poor adhesion was significantly improved by both 172 nm excimer lamp and 193 nm excimer laser assisted surface treatments. While Xe2∗ lamp irradiation, applied in a modest vacuum environment, was sufficient by itself to improve adhesion, the ArF laser process was only effective when the irradiated interface was in contact with 1,2-diaminoethane photoreagent. It was found that the tensile strength of an epoxy resin glued interface created on treated surfaces depended strongly on the applied number of laser pulses and lamp irradiation time. Laser treatment caused fast tensile strength increase during the first 50-500 pulses, while after this it saturates slowly at about 5.5 MPa in the 500-2500 pulse domain. The excimer lamp irradiation resulted in a maximum tensile strength of approximately 10 MPa after 2 min irradiation time which reduced to about 65% of the peak value at longer times.

Single-pass high harmonic generation at high repetition rate and photon flux

NASA Astrophysics Data System (ADS)

Hädrich, Steffen; Rothhardt, Jan; Krebs, Manuel; Demmler, Stefan; Klenke, Arno; Tünnermann, Andreas; Limpert, Jens

2016-09-01

Sources of short wavelength radiation with femtosecond to attosecond pulse durations, such as synchrotrons or free electron lasers, have already made possible numerous, and will facilitate more, seminal studies aimed at understanding atomic and molecular processes on fundamental length and time scales. Table-top sources of coherent extreme ultraviolet to soft x-ray radiation enabled by high harmonic generation (HHG) of ultrashort pulse lasers have also gained significant attention in the last few years due to their enormous potential for addressing a plethora of applications, therefore constituting a complementary source to large-scale facilities (synchrotrons and free electron lasers). Ti:sapphire based laser systems have been the workhorses for HHG for decades, but are limited in repetition rate and average power. On the other hand, it has been widely recognized that fostering applications in fields such as photoelectron spectroscopy and microscopy, coincidence detection, coherent diffractive imaging and frequency metrology requires a high repetition rate and high photon flux HHG sources. In this article we will review recent developments in realizing the demanding requirement of producing a high photon flux and repetition rate at the same time. Particular emphasis will be put on suitable ultrashort pulse and high average power lasers, which directly drive harmonic generation without the need for external enhancement cavities. To this end we describe two complementary schemes that have been successfully employed for high power fiber lasers, i.e. optical parametric chirped pulse amplifiers and nonlinear pulse compression. Moreover, the issue of phase-matching in tight focusing geometries will be discussed and connected to recent experiments. We will highlight the latest results in fiber laser driven high harmonic generation that currently produce the highest photon flux of all existing sources. In addition, we demonstrate the first promising applications and discuss the future direction and challenges of this new type of HHG source.

Generation of high-intensity sub-30 as pulses by inhomogeneous polarization gating technology in bowtie-shaped nanostructure

NASA Astrophysics Data System (ADS)

Feng, Liqiang; Feng, A. Yuanzi

2018-04-01

The generation of high-order harmonics and single attosecond pulses (SAPs) from He atom driven by the inhomogeneous polarization gating technology in a bowtie-shaped nanostructure is theoretically investigated. The results show that by the proper addition of bowtie-shaped nanostructure along the driven laser polarization direction, the harmonic emission becomes sensitive to the position of the laser field, and the harmonics emitted at the maximum orders that generate SAPs occur only at one side of the region inside the nanostructure. As a result, not only the harmonic cutoff can be extended, but also the modulations of the harmonics can be decreased, showing a carrier envelope phase independent harmonic cutoff with a bandwidth of 310 eV. Further, with the proper introduction of an ultraviolet pulse, the harmonic yield can be enhanced by 2 orders of magnitude. Finally, by the Fourier transformation of the selected harmonics, some SAPs with a full width at half maximum of sub-30 as can be obtained.

Ultrafast laser control of autoionizing resonances observed in attosecond transient absorption

NASA Astrophysics Data System (ADS)

Liao, Chen-Ting; Harkema, Nathan; Sandhu, Arvinder

2017-04-01

Attosecond and femtosecond extreme ultraviolet (XUV) pulses can be used to probe electron dynamics in high-lying excited states that autoionize on a femtosecond timescale, thus providing information on the process of Auger decay and its interference with the continua. Here we utilize XUV pulses in connection with infrared (IR) pulses to perform attosecond transient absorption spectroscopy of the impulsive response of argon autoionizing Rydberg states in the vicinity of the 3s-1 4 p resonance. We show that by tuning the time delay and field polarization of IR pulse, it is possible to control the dipolar coupling between neighboring states and hence the spectral line shape of the resonance, such as the transition between Breit-Wigner to Beutler-Fano profiles. NSF Grant No. PHY-1505556.

Pulsed UV laser light on Escherichia coli and Saccharomyces cerevisiae suspended in non-alcoholic beer

PubMed Central

Hosseini, SM; Azar-Daryany, MK; Massudi, R; Elikaei, A

2011-01-01

Background The aim of this study was to investigate the effect of pulsed ultra-violet (UV) irradiation on inactivation of beer spoilage microorganisms. UV irradiation is nowadays cost effective enough to compete with traditional biological, physical, and chemical treatment technologies and has become an alternative to such methods. Material and Methods Photoinactivation effects of pulsed UV laser with the wavelengths of 355 and 266 nm, which inactivate typical prokaryotic (Escherichia coli) and eukaryotic (Saccharomyces cerevisiae) microorganisms, were examined with different doses and exposure times. Results A dose of 100 J/cm2 of the 355 nm pulsed UV laser was able to reduce about 1 to 2 log (88.75%) of E.coli with the population of 1.6×108 colony-forming units (CFU/ml), and 97% of 3.2×107, 3×106, 5.5×105, and 9×104 CFU/ml. In the case of 266 nm, more than 99% reduction in E. coli serial dilutions was inactivated, using 10 J/cm2 with exception of 7×104 CFU/ml which was not detected any bacterial growth using 5 J/cm2. In addition, 50, 40, and 20 J/cm2 energy were used successfully to inactivate S. cerevisiae at the populations of 5.4×106, 7×105, 5×104 and 4×103 CFU/ml, respectively. As a result, pulsed UV Laser with 266 nm was strong enough to inactivate a high titer of bacterial and yeast indicator standards suspended in non-alcoholic beer in comparison with 355nm doses. Conclusion Results indicate that pulsed UV technology, in principle, is an attractive alternative to conventional methods for the inactivation of indicator microorganisms and has potential in irradiation of unpasteurized beer. PMID:22347580

Inversion of the resonance line of Sr/+/ produced by optically pumping Sr atoms

NASA Technical Reports Server (NTRS)

Green, W. R.; Falcone, R. W.

1978-01-01

A description is presented of an experiment which demonstrates the selective production of excited-state ions by an optical absorption from neutrals. An inversion on the resonance line of Sr(+) was produced by laser excitation of a two-electron transition, followed by ionization of one of the excited electrons by the same laser. A pulsed, mode-locked laser operating at 2680 A was used to excite atoms from the Sr ground level. The same laser then ionized the excited atoms. The 2680-A pump beam was generated by frequency doubling the output of a synchronously pumped mode-locked dye laser in a KDP crystal. It is pointed out that the reported results are significant for the construction of vacuum-ultraviolet and X-ray lasers. Many of the proposed methods for making such lasers depend on the selective production of excited-state ions.

[The commonest therapeutic methods for laser irradiation of blood].

PubMed

Moskvin, S V; Konchugova, T V; Khadartsev, A А

2017-12-05

One of the most widely employed methods of laser therapy is laser irradiation of blood (LIB). There are two modifications of this technique, one being intravenous low-intensity laser irradiation of blood (ILIB), the other non-invasive blood irradiation(NLIB). The two methods have been developing independently since either has its advantages and disadvantages. The present article was designed to review the main currently available techniques for laser irradiation of blood which are presented in the form of tables (charts). Replacing the UV irradiation of blood with UV lamps by laser ultraviolet irradiation of blood (LUVIB®) has made it possible to significantly simplify the technique and enhanced its efficiency. The most effective options for ILIB are the combined techniques: ILIB-635 + LUVIB® and ILIB-525 + LUVIB. The most effective technique for ELIB is believed to be the use of low-intensity pulsed laser light with a wavelength of 635 nm and output power up to 40 W.

Invisible two-dimensional barcode fabrication inside a synthetic fused silica by femtosecond laser processing using a computer-generated hologram

NASA Astrophysics Data System (ADS)

Kawashima, Hayato; Yamaji, Masahiro; Suzuki, Jun'ichi; Tanaka, Shuhei

2011-03-01

We report an invisible two-dimensional (2D) barcode embedded into a synthetic fused silica by femtosecond laser processing using a computer-generated hologram (CGH) that generates a spatially extended femtosecond pulse beam in the depth direction. When we illuminate the irradiated 2D barcode pattern with a 254 nm ultraviolet (UV) light, a strong red photoluminescence (PL) is observed, and we can read it by using a complementary metal oxide semiconductor (CMOS) camera and image processing technology. This work provides a novel barcode fabrication method by femtosecond laser processing using a CGH and a barcode reading method by a red PL.

Ultraviolet out-of-band radiation studies in laser tin plasma sources

NASA Astrophysics Data System (ADS)

Parchamy, Homaira; Szilagyi, John; Masnavi, Majid; Richardson, Martin

2017-11-01

Out-of-band long wavelength emission measurements from high power, high-repetition-rate extreme-ultra-violet lithography (EUVL) laser plasma sources are imperative to estimating heat deposition in EUV mirrors, and the impact of short wavelength light transported through the imaging system to the wafer surface. This paper reports a series of experiments conducted to measure the absolute spectral irradiances of laser-plasmas produced from planar tin targets over the wavelength region of 124 to 164 nm by 1.06 μm wavelength, 10 ns full-width-at-half-maximum Gaussian laser pulses. The use of spherical targets is relevant to the EUVL source scenario. Although plasmas produced from planar surfaces evolve differently, there is a close similarity to the evolution of current from 10.6 μm CO2 laser EUVL sources, which use a pre-pulse from a lower energy solid-state laser to melt and reform an initial spherical droplet into a thin planar disc target. The maximum of radiation conversion efficiency in the 124-164 nm wavelength band (1%/2πsr) occurs at the laser intensity of 1010 W cm-2. A developed collisional-radiative model reveals the strong experimental spectra that originate mainly from the 4d105p2-4d105s5p, 4d105p-4d105s resonance lines, and 4d95p-4d95s unresolved transition arrays from Sn III, Sn IV, and Sn V ions, respectively. The calculated conversion efficiencies using a 2D radiation-hydrodynamics model are in agreement with the measurements. The model predicts the out-of-band (100-400 nm) radiation conversion efficiencies generated by both 1.06 and 10.6 μm pulses. The 10.6 μm laser pulse produces a higher conversion efficiency (12%/2πsr) at the lower laser intensity of 109 W cm-2.

Quasi-supercontinuum source in the extreme ultraviolet using multiple frequency combs from high-harmonic generation

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

Wünsche, Martin; Fuchs, Silvio; Aull, Stefan

A quasi-supercontinuum source in the extreme ultraviolet (XUV) is demonstrated using a table-top femtosecond laser and a tunable optical parametric amplifier (OPA) as a driver for high-harmonic generation (HHG). The harmonic radiation, which is usually a comb of odd multiples of the fundamental frequency, is generated by near-infrared (NIR) laser pulses from the OPA. A quasi-continuous XUV spectrum in the range of 30 to 100 eV is realized by averaging over multiple harmonic comb spectra with slightly different fundamental frequencies and thus different spectral spacing between the individual harmonics. The driving laser wavelength is swept automatically during an averaging timemore » period. With a total photon flux of 4×10 9 photons/s in the range of 30 eV to 100 eV and 1×10 7 photons/s in the range of 100 eV to 200 eV, the resulting quasi-supercontinuum XUV source is suited for applications such as XUV coherence tomography (XCT) or near-edge absorption fine structure spectroscopy (NEXAFS).« less

Quasi-supercontinuum source in the extreme ultraviolet using multiple frequency combs from high-harmonic generation

DOE PAGES

Wünsche, Martin; Fuchs, Silvio; Aull, Stefan; ...

2017-03-16

A quasi-supercontinuum source in the extreme ultraviolet (XUV) is demonstrated using a table-top femtosecond laser and a tunable optical parametric amplifier (OPA) as a driver for high-harmonic generation (HHG). The harmonic radiation, which is usually a comb of odd multiples of the fundamental frequency, is generated by near-infrared (NIR) laser pulses from the OPA. A quasi-continuous XUV spectrum in the range of 30 to 100 eV is realized by averaging over multiple harmonic comb spectra with slightly different fundamental frequencies and thus different spectral spacing between the individual harmonics. The driving laser wavelength is swept automatically during an averaging timemore » period. With a total photon flux of 4×10 9 photons/s in the range of 30 eV to 100 eV and 1×10 7 photons/s in the range of 100 eV to 200 eV, the resulting quasi-supercontinuum XUV source is suited for applications such as XUV coherence tomography (XCT) or near-edge absorption fine structure spectroscopy (NEXAFS).« less

Measurements of Raman scattering in the middle ultraviolet band from persistent chemical warfare agents

NASA Astrophysics Data System (ADS)

Kullander, Fredrik; Landström, Lars; Lundén, Hampus; Mohammed, Abdesalam; Olofsson, Göran; Wästerby, Pär.

2014-05-01

The very low Raman scattering cross section and the fluorescence background limit the measuring range of Raman based instruments operating in the visible or infrared band. We are exploring if laser excitation in the middle ultraviolet (UV) band between 200 and 300 nm is useful and advantageous for detection of persistent chemical warfare agents (CWA) on various kinds of surfaces. The UV Raman scattering from tabun, mustard gas, VX and relevant simulants in the form of liquid surface contaminations has been measured using a laboratory experimental setup with a short standoff distance around 1 meter. Droplets having a volume of 1 μl were irradiated with a tunable pulsed laser swept within the middle UV band. A general trend is that the signal strength moves through an optimum when the laser excitation wavelength is swept between 240 and 300 nm. The signal from tabun reaches a maximum around 265 nm, the signal from mustard gas around 275 nm. The Raman signal from VX is comparably weak. Raman imaging by the use of a narrow bandpass UV filter is also demonstrated.

Time-resolved detection of aromatic compounds on planetary surfaces by ultraviolet laser induced fluorescence and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Eshelman, E.; Daly, M. G.; Slater, G.; Cloutis, E.

2015-12-01

Raman spectroscopic instruments are highly capable in the search for organics on Mars due to the potential to perform rapid and nondestructive measurements on unprepared samples. Upcoming and future Raman instruments are likely to also incorporate laser-induced fluorescence (LIF) capabilities, which can be added for modest cost and complexity. We demonstrate that it is possible to obtain sub-ns fluorescence lifetime measurements of Mars-relevant organics and minerals if a fast time-gating capability is used with an intensified detector and a short ultraviolet laser pulse. This serves a primary purpose of discriminating mineral from short-lived (less than 10 ns) organic fluorescence, considered a potential biosignature. Additionally, lifetime measurements may assist in determining if more than one fluorescing species is present and provide information concerning the molecular structure as well as the local environment. Fast time-gating is also useful at longer visible or near-IR wavelengths, as this approach increases the sensitivity of the instrument to organic material by removing the majority of the fluorescence background from the Raman signal and reducing the effect of ambient light.

The influence of surface contamination on the ion emission from nanosecond-pulsed laser ablation of Al and Cu

NASA Astrophysics Data System (ADS)

Ullah, S.; Dogar, A. H.; Qayyum, H.; Rehman, Z. U.; Qayyum, A.

2018-04-01

Ions emitted from planar Al and Cu targets irradiated with a 1064 nm pulsed laser were investigated with the help of a time-resolving Langmuir probe. It was found that the intensity of the ions emitted from a target area rapidly decreases with the increasing number of laser shots, and seems to reach saturation after about 10 laser shots. The saturated intensity of Al and Cu ions was approximately 0.1 and 0.3 times the intensity of the respective ions measured at the first laser shot, respectively. The higher target ion intensity for the first few shots is thought to be due to the enhanced ionization of target atoms by vacuum-ultraviolet radiations emitted from the thermally excited/ionized surface contaminants. The reduction of target ion intensity with an increasing number of laser shots thus indicates the removal of contaminants from the irradiated surface area. Laser-cleaned Al and Cu surfaces were then allowed to be recontaminated with residual vacuum gases and the ion intensity was measured at various time delays. The prolonged exposure of the cleaned target to vacuum residual gases completely restores the ion intensity. Regarding surface contaminants removal, laser shots of higher intensities were found to be more effective than a higher number of laser shots having lower intensities.

Novel approach to real-time flash photolysis and confocal [Ca2+] imaging

PubMed Central

Sobie, Eric A.; Kao, Joseph P.Y.; Lederer, W. J.

2008-01-01

Flash photolysis of “caged” compounds using ultraviolet light is a powerful experimental technique for producing rapid changes in concentrations of bioactive signaling molecules. Studies that employ this technique have used diverse strategies for controlling the spatial and temporal application of light to the specimen. Here we describe a new system for flash photolysis that delivers light from a pulsed, adjustable intensity laser through an optical fiber coupled into the epifluorescence port of a commercial confocal microscope. Photolysis is achieved with extremely brief (5 ns) pulses of ultraviolet light (355 nm) that can be synchronized with respect to confocal laser scanning. The system described also localizes the UV intensity spatially so that uncaging only occurs in defined sub-cellular regions; moreover, since the microscope optics are used in localization, the photolysis volume can be easily adjusted. Experiments performed on rat ventricular myocytes loaded with the Ca2+ indicator fluo-3 and the Ca2+ cage NP-EGTA demonstrate the system's capabilities. Localized intracellular increases in [Ca2+] can trigger sarcoplasmic reticular Ca2+ release events such as Ca2+ sparks and, under certain conditions, regenerative Ca2+ waves. This relatively simple and inexpensive system is therefore a useful tool for examining local signaling in heart and other tissues. PMID:17323075

Radiation damage to amorphous carbon thin films irradiated by multiple 46.9 nm laser shots below the single-shot damage threshold

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

Juha, L.; Hajkova, V.; Vorlicek, V.

2009-05-01

High-surface-quality amorphous carbon (a-C) optical coatings with a thickness of 45 nm, deposited by magnetron sputtering on a silicon substrate, were irradiated by the focused beam of capillary-discharge Ne-like Ar extreme ultraviolet laser (CDL=capillary-discharge laser; XUV=extreme ultraviolet, i.e., wavelengths below 100 nm). The laser wavelength and pulse duration were 46.9 nm and 1.7 ns, respectively. The laser beam was focused onto the sample surface by a spherical Sc/Si multilayer mirror with a total reflectivity of about 30%. The laser pulse energy was varied from 0.4 to 40 muJ on the sample surface. The irradiation was carried out at five fluencemore » levels between 0.1 and 10 J/cm{sup 2}, accumulating five different series of shots, i.e., 1, 5, 10, 20, and 40. The damage to the a-C thin layer was investigated by atomic force microscopy (AFM) and Nomarski differential interference contrast (DIC) optical microscopy. The dependence of the single-shot-damaged area on pulse energy makes it possible to determine a beam spot diameter in the focus. Its value was found to be equal to 23.3+-3.0 mum using AFM data, assuming the beam to have a Gaussian profile. Such a plot can also be used for a determination of single-shot damage threshold in a-C. A single-shot threshold value of 1.1 J/cm{sup 2} was found. Investigating the consequences of the multiple-shot exposure, it has been found that an accumulation of 10, 20, and 40 shots at a fluence of 0.5 J/cm{sup 2}, i.e., below the single-shot damage threshold, causes irreversible changes of thin a-C layers, which can be registered by both the AFM and the DIC microscopy. In the center of the damaged area, AFM shows a-C removal to a maximum depth of 0.3, 1.2, and 1.5 nm for 10-, 20- and 40-shot exposure, respectively. Raman microprobe analysis does not indicate any change in the structure of the remaining a-C material. The erosive behavior reported here contrasts with the material expansion observed earlier [L. Juha et al., Proc. SPIE 5917, 91 (2005)] on an a-C sample irradiated by a large number of femtosecond pulses of XUV high-order harmonics.« less

UV laser-assisted wire stripping and micro-machining

NASA Astrophysics Data System (ADS)

Martyniuk, Jerry

1994-02-01

Results are reported for the use of a 266 nm frequency quadrupled Nd:YAG ultraviolet laser in the areas of wire stripping of small coaxial type transmission lines and for micro-machining of various materials including copper, glass, polyimide and DuPont TEFLONTM. This new laser is typically run with a 2 KHz repetition rate, 40 ns FWHM pulse and a fluence of about 50 joules/cm2 which makes it possible to micro-machine metals, polymers, glasses and ceramics. The high fluence of this laser allows shielding structures such as Al-MylarTM, Al-KaptonTM or the plated copper used in small coaxial cables to be precisely cut. Cut rates are reported for the above materials as well as results and photos of wire stripping and micro- machining.

Modification of the amorphous carbon films by the ns-laser irradiation

NASA Astrophysics Data System (ADS)

Grigonis, Alfonsas; Marcinauskas, Liutauras; Vinciunaite, Vinga; Raciukaitis, Gediminas

2011-10-01

The effect of a nanosecond laser irradiation of thin (60 and 145 nm) amorphous, diamond-like carbon films deposited on Si substrate by an ion beam deposition (IBD) from pure acetylene and acetylene/hydrogen (1:2) gas mixture was analyzed in this work. The films were irradiated with the infrared (IR) and ultraviolet (UV) radiation of the nanosecond Nd:YAG lasers working at the first (1.16 eV) and the third (3.48 eV) harmonics, using a multi-shot regime. The IR laser irradiation stimulated a minor increase in the fraction of sp2 bonds, causing a slight decrease in the hardness of the films and initiated SiC formation. Irradiation with the UV laser caused the formation of carbides and increased hydrogenization of the Si substrate and the fraction of sp2 sites. Spalliation and ablation were observed at a higher energy density and with a large number of laser pulses per spot.

Charge Assisted Laser Desorption/Ionization Mass Spectrometry of Droplets

PubMed Central

Jorabchi, Kaveh; Westphall, Michael S.; Smith, Lloyd M.

2008-01-01

We propose and evaluate a new mechanism to account for analyte ion signal enhancement in ultraviolet-laser desorption mass spectrometry of droplets in the presence of corona ions. Our new insights are based on timing control of corona ion production, laser desorption, and peptide ion extraction achieved by a novel pulsed corona apparatus. We demonstrate that droplet charging rather than gas-phase ion-neutral reactions is the major contributor to analyte ion generation from an electrically isolated droplet. Implications of the new mechanism, termed charge assisted laser desorption/ionization (CALDI), are discussed and contrasted to those of the laser desorption atmospheric pressure chemical ionization method (LD-APCI). It is also demonstrated that analyte ion generation in CALDI occurs with external electric fields about one order of magnitude lower than those needed for atmospheric pressure matrix assisted laser desorption/ionization or electrospray ionization of droplets. PMID:18387311

Bioaerosol detection and classification using dual excitation wavelength laser-induced fluorescence

NASA Astrophysics Data System (ADS)

Jonsson, Per; Wästerby, Pär.; Gradmark, Per-Åke; Hedborg, Julia; Larsson, Anders; Landström, Lars

2015-05-01

We present results obtained by a detection system designed to measure laser-induced fluorescence from individual aerosol particles using dual excitation wavelengths. The aerosol is sampled from ambient air and via a 1 mm diameter nozzle, surrounded by a sheath air flow, confined into a particle beam. A continuous wave blue laser at 404 nm is focused on the aerosol beam and two photomultiplier tubes monitor the presence of individual particles by simultaneous measuring the scattered light and any induced fluorescence. When a particle is present in the detection volume, a laser pulse is triggered from an ultraviolet laser at 263 nm and the corresponding fluorescence spectrum is acquired with a spectrometer based on a diffraction grating and a 32 channel photomultiplier tube array with single-photon sensitivity. The spectrometer measures the fluorescence spectra in the wavelength region from 250 to 800 nm. In the present report, data were measured on different monodisperse reference aerosols, simulants of biological warfare agents, and different interference aerosol particles, e.g. pollen. In the analysis of the experimental data, i.e., the time-resolved scattered and fluorescence signals from 404 nm c.w. light excitation and the fluorescence spectra obtained by a pulsed 263 nm laser source, we use multivariate data analysis methods to classify each individual aerosol particle.

Chemical-free inactivated whole influenza virus vaccine prepared by ultrashort pulsed laser treatment

NASA Astrophysics Data System (ADS)

Tsen, Shaw-Wei David; Donthi, Nisha; La, Victor; Hsieh, Wen-Han; Li, Yen-Der; Knoff, Jayne; Chen, Alexander; Wu, Tzyy-Choou; Hung, Chien-Fu; Achilefu, Samuel; Tsen, Kong-Thon

2015-05-01

There is an urgent need for rapid methods to develop vaccines in response to emerging viral pathogens. Whole inactivated virus (WIV) vaccines represent an ideal strategy for this purpose; however, a universal method for producing safe and immunogenic inactivated vaccines is lacking. Conventional pathogen inactivation methods such as formalin, heat, ultraviolet light, and gamma rays cause structural alterations in vaccines that lead to reduced neutralizing antibody specificity, and in some cases, disastrous T helper type 2-mediated immune pathology. We have evaluated the potential of a visible ultrashort pulsed (USP) laser method to generate safe and immunogenic WIV vaccines without adjuvants. Specifically, we demonstrate that vaccination of mice with laser-inactivated H1N1 influenza virus at about a 10-fold lower dose than that required using conventional formalin-inactivated influenza vaccines results in protection against lethal H1N1 challenge in mice. The virus, inactivated by the USP laser irradiation, has been shown to retain its surface protein structure through hemagglutination assay. Unlike conventional inactivation methods, laser treatment did not generate carbonyl groups in protein, thereby reducing the risk of adverse vaccine-elicited T helper type 2 responses. Therefore, USP laser treatment is an attractive potential strategy to generate WIV vaccines with greater potency and safety than vaccines produced by current inactivation techniques.

Studies of bandwidth dependence of laser plasma instabilities driven by the Nike laser

NASA Astrophysics Data System (ADS)

Weaver, J.; Kehne, D.; Obenschain, S.; Serlin, V.; Schmitt, A. J.; Oh, J.; Lehmberg, R. H.; Brown, C. M.; Seely, J.; Feldman, U.

2012-10-01

Experiments at the Nike laser facility of the Naval Research Laboratory are exploring the influence of laser bandwidth on laser plasma instabilities (LPI) driven by a deep ultraviolet pump (248 nm) that incorporates beam smoothing by induced spatial incoherence (ISI). In early ISI studies with longer wavelength Nd:glass lasers (1054 nm and 527 nm),footnotetextObenschain, PRL 62(1989);Mostovych, PRL 62(1987);Peyser, Phys. Fluids B 3(1991). stimulated Raman scattering, stimulated Brillouin scattering, and the two plasmon decay instability were reduced when wide bandwidth ISI (δν/ν˜0.03-0.19%) pulses irradiated targets at moderate to high intensities (10^14-10^15 W/cm^2). The current studies will compare the emission signatures of LPI from planar CH targets during Nike operation at large bandwidth (δν˜1THz) to observations for narrower bandwidth operation (δν˜0.1-0.3THz). These studies will help clarify the relative importance of the short wavelength and wide bandwidth to the increased LPI intensity thresholds observed at Nike. New pulse shapes are being used to generate plasmas with larger electron density scale-lengths that are closer to conditions during pellet implosions for direct drive inertial confinement fusion.

Evidence of liquid phase during laser-induced periodic surface structures formation induced by accumulative ultraviolet picosecond laser beam

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

Huynh, T. T. D.; Petit, A.; Semmar, N., E-mail: nadjib.semmar@univ-orleans.fr

2015-11-09

Laser-induced periodic surface structures (LIPSS) were formed on Cu/Si or Cu/glass thin films using Nd:YAG laser beam (40 ps, 10 Hz, and 30 mJ/cm{sup 2}). The study of ablation threshold is always achieved over melting when the variation of the number of pulses increases from 1 to 1000. But the incubation effect is leading to reduce the threshold of melting as increasing the number of laser pulse. Also, real time reflectivity signals exhibit typical behavior to stress the formation of a liquid phase during the laser-processing regime and helps to determine the threshold of soft ablation. Atomic Force Microscopy (AFM) analyses have shownmore » the topology of the micro-crater containing regular spikes with different height. Transmission Electron Microscopy (TEM) allows finally to show three distinguished zones in the close region of isolated protrusions. The central zone is a typical crystallized area of few nanometers surrounded by a mixed poly-crystalline and amorphous area. Finally, in the region far from the protrusion zone, Cu film shows an amorphous structure. The real time reflectivity, AFM, and HR-TEM analyses evidence the formation of a liquid phase during the LIPSS formation in the picosecond regime.« less

Invited Article: Coherent imaging using seeded free-electron laser pulses with variable polarization: First results and research opportunities

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

Capotondi, F.; Pedersoli, E.; Mahne, N.

2013-05-15

FERMI-Elettra, the first vacuum ultraviolet and soft X-ray free-electron laser (FEL) using by default a 'seeded' scheme, became operational in 2011 and has been opened to users since December 2012. The parameters of the seeded FERMI FEL pulses and, in particular, the superior control of emitted radiation in terms of spectral purity and stability meet the stringent requirements for single-shot and resonant coherent diffraction imaging (CDI) experiments. The advantages of the intense seeded FERMI pulses with variable polarization have been demonstrated with the first experiments performed using the multipurpose experimental station operated at the diffraction and projection imaging (DiProI) beamline.more » The results reported here were obtained with fixed non-periodic targets during the commissioning period in 2012 using 20-32 nm wavelength range. They demonstrate that the performance of the FERMI FEL source and the experimental station meets the requirements of CDI, holography, and resonant magnetic scattering in both multi- and single-shot modes. Moreover, we present the first magnetic scattering experiments employing the fully circularly polarized FERMI pulses. The ongoing developments aim at pushing the lateral resolution by using shorter wavelengths provided by double-stage cascaded FERMI FEL-2 and probing ultrafast dynamic processes using different pump-probe schemes, including jitter-free seed laser pump or FEL-pump/FEL-probe with two color FEL pulses generated by the same electron bunch.« less

Photon synthesis of iron oxide thin films for thermo-photo-chemical sensors

NASA Astrophysics Data System (ADS)

Mulenko, S. A.; Petrov, Yu. N.; Gorbachuk, N. T.

2012-09-01

Ultraviolet photons of KrF-laser (248 nm) and of photodiode (360 nm) were used for the synthesis of iron oxide thin films with variable thickness, stoichiometry and electrical properties. The reactive pulsed laser deposition (RPLD) method was based on KrF-laser and photon-induced chemical vapor deposition (PCVD) was based on a photodiode. Deposited films demonstrated semiconductor properties with variable band gap (Eg). The film thickness (50-140 nm) and Eg depended on the laser pulse number, oxygen and iron carbonyl vapor pressure in the deposition chamber, and exposure time to the substrate surface with ultraviolet (UV) radiation. Sensing characteristics strongly depended on electrical and structural properties of such thin films. Iron oxide films were deposited on <1 0 0> Si substrate and had large thermo electromotive force (e.m.f.) coefficient (S) and high photosensitivity (F). The largest value of the S coefficient obtained by RPLD was about 1.65 mV/K in the range 270-290 K and by PCVD was about 1.5 mV/K in the range 280-322 K. The largest value F obtained by RPLD and PCVD was about 44 Vc/W and 40 Vc/W, accordingly, for white light at power density (I ≅ 0.006 W/cm2). It was shown that the S coefficient and F strongly depended on Eg. Moreover, these films were tested as chemical sensors: the largest sensitivity of NO molecules was at the level of 3 × 1012 cm-3. Our results showed that RPLD and PCVD were used to synthesize semiconductor iron oxide thin films with different sensing properties. So iron oxide thin films synthesized by UV photons are up-to-date materials for multi-parameter sensors: thermo-photo-chemical sensors operating at moderate temperature.

Time-resolved atomic inner-shell spectroscopy

NASA Astrophysics Data System (ADS)

Drescher, M.; Hentschel, M.; Kienberger, R.; Uiberacker, M.; Yakovlev, V.; Scrinzi, A.; Westerwalbesloh, Th.; Kleineberg, U.; Heinzmann, U.; Krausz, F.

2002-10-01

The characteristic time constants of the relaxation dynamics of core-excited atoms have hitherto been inferred from the linewidths of electronic transitions measured by continuous-wave extreme ultraviolet or X-ray spectroscopy. Here we demonstrate that a laser-based sampling system, consisting of a few-femtosecond visible light pulse and a synchronized sub-femtosecond soft X-ray pulse, allows us to trace these dynamics directly in the time domain with attosecond resolution. We have measured a lifetime of 7.9-0.9^{+1.0fs of M-shell vacancies of krypton in such a pump-probe experiment.}

Enhanced stimulated Raman scattering by femtosecond ultraviolet plasma grating in water

NASA Astrophysics Data System (ADS)

Liu, Fengjiang; Yuan, Shuai; He, Boqu; Nan, Junyi; Khan, Abdul Qayyum; Ding, Liang'en; Zeng, Heping

2018-02-01

Efficient forward stimulated Raman scattering (SRS) was observed along 400-nm femtosecond (fs) laser filaments in water. SRS conversion dominated over self-phase modulation induced continuum generation as the input pulse energy was above 4 μJ (˜30 Pcr), implying that plasma in the aqueous filamentation channel played an important role in compensating for the group velocity walk-off between the pump and Stokes pulses. By overlapping two synchronous fs 400-nm filaments to form plasma grating in water, significant enhancement of SRS conversion was observed. Such a SRS enhancement originated from the ultrahigh plasma density in the intersection region of the preformed plasma grating.

Ultraviolet Channeling Dynamics in Gaseous Media for X -- Ray Production

NASA Astrophysics Data System (ADS)

McCorkindale, John Charters

The development of a coherent high brightness / short duration X -- ray source has been of considerable interest to the scientific community as well as various industries since the invention of the technology. Possible applications include X -- ray lithography, biological micro-imaging and the probing of molecular and atomic dynamics. One such source under investigation involves the interaction of a high pulsed power KrF UV laser with a noble gas target (krypton or xenon), producing a photon energy from 1 -- 5 keV. Amplification in this regime requires materials with very special properties found in spatially organized hollow atom clusters. One of the driving forces behind X -- ray production is the UV laser. Theoretical analysis shows that above a critical laser power, the formation of a stable plasma channel in the gaseous medium will occur which can act as a guide for the X-ray pulse and co-propagating UV beam. These plasma channels are visualized with a triple pinhole camera, axial and transverse von Hamos spectrometers and a Thomson scattering setup. In order to understand observed channel morphologies, full characterization of the drive laser was achieved using a Transient Grating -- Frequency Resolved Optical Gating (TG-FROG) technique which gives a full temporal representation of the electric field and associated phase of the ultrashort pulse. Insights gleaned from the TG -- FROG data as well as analysis of photodiode diagnostics placed along the UV laser amplification chain provide explanations for the plasma channel morphology and X -- ray output.

High-power 266 nm ultraviolet generation in yttrium aluminum borate.

PubMed

Liu, Qiang; Yan, Xingpeng; Gong, Mali; Liu, Hua; Zhang, Ge; Ye, Ning

2011-07-15

A yttrium aluminum borate [YAl(3)(BO(3))(4)] (YAB) crystal with UV cutoff wavelength of 165 nm is used as the nonlinear optical crystal for fourth harmonic generation. The fundamental frequency laser at 1064 nm from an Nd:YVO(4) master oscillator power amplifier laser was frequency doubled to 532 nm. Using the type I phase-matching YAB crystal, a 5.05 W average power 266 nm UV laser was obtained at the pulse repetition frequency of 65 kHz, corresponding to the conversion efficiency of 12.3% from 532 to 266 nm. The experimental results show great potential for the application of using YAB as a nonlinear optical crystal to get high-power fourth harmonic generation. © 2011 Optical Society of America

Development of extreme ultraviolet and soft x-ray multilayer optics for scientific studies with femtosecond/attosecond sources

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

Aquila, Andrew Lee

The development of multilayer optics for extreme ultraviolet (EUV) radiation has led to advancements in many areas of science and technology, including materials studies, EUV lithography, water window microscopy, plasma imaging, and orbiting solar physics imaging. Recent developments in femtosecond and attosecond EUV pulse generation from sources such as high harmonic generation lasers, combined with the elemental and chemical specificity provided by EUV radiation, are opening new opportunities to study fundamental dynamic processes in materials. Critical to these efforts is the design and fabrication of multilayer optics to transport, focus, shape and image these ultra-fast pulses This thesis describes themore » design, fabrication, characterization, and application of multilayer optics for EUV femtosecond and attosecond scientific studies. Multilayer mirrors for bandwidth control, pulse shaping and compression, tri-material multilayers, and multilayers for polarization control are described. Characterization of multilayer optics, including measurement of material optical constants, reflectivity of multilayer mirrors, and metrology of reflected phases of the multilayer, which is critical to maintaining pulse size and shape, were performed. Two applications of these multilayer mirrors are detailed in the thesis. In the first application, broad bandwidth multilayers were used to characterize and measure sub-100 attosecond pulses from a high harmonic generation source and was performed in collaboration with the Max-Planck institute for Quantum Optics and Ludwig- Maximilians University in Garching, Germany, with Professors Krausz and Kleineberg. In the second application, multilayer mirrors with polarization control are useful to study femtosecond spin dynamics in an ongoing collaboration with the T-REX group of Professor Parmigiani at Elettra in Trieste, Italy. As new ultrafast x-ray sources become available, for example free electron lasers, the multilayer designs described in this thesis can be extended to higher photon energies, and such designs can be used with those sources to enable new scientific studies, such as molecular bonding, phonon, and spin dynamics.« less

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.

Single-Step Laser-Assisted Graphene Oxide Reduction and Nonlinear Optical Properties Exploration via CW Laser Excitation

NASA Astrophysics Data System (ADS)

Ghasemi, Fatemeh; Razi, Sepehr; Madanipour, Khosro

2018-02-01

The synthesis of reduced graphene oxide using pulsed laser irradiation is experimentally investigated. For this purpose, various irradiation conditions were selected and the chemical features of the different products were explored using ultraviolet-visible, Fourier transform infrared and Raman spectroscopy techniques. Moreover, the nonlinear optical properties of the synthesized products were assessed by using open and closed aperture Z-scan techniques, in which continuous wave laser irradiating at 532-nm wavelength was utilized as the exciting source. The results clearly revealed that the degree of graphene oxide reduction not only depends on the amount of the irradiation dose (energy of the laser beam × exposure time) but also on the light source wavelength. Furthermore, strong dependency between the nonlinear optical properties of the products and the amount of the de-oxygenation was observed. The experimental results are discussed in detail.

Detection of carcinogenic metals in kidney stones using ultraviolet laser-induced breakdown spectroscopy.

PubMed

Khalil, Ahmed Asaad I; Gondal, Mohammed A; Shemis, Mohamed; Khan, Irfan S

2015-03-10

The UV single-pulsed (SP) laser-induced breakdown spectroscopy (LIBS) system was developed to detect the carcinogenic metals in human kidney stones extracted through the surgical operation. A neodymium yttrium aluminium garnet laser operating at 266 nm wavelength and 20 Hz repetition rate along with a spectrometer interfaced with an intensified CCD (ICCD) was applied for spectral analysis of kidney stones. The ICCD camera shutter was synchronized with the laser-trigger pulse and the effect of laser energy and delay time on LIBS signal intensity was investigated. The experimental parameters were optimized to obtain the LIBS plasma in local thermodynamic equilibrium. Laser energy was varied from 25 to 50 mJ in order to enhance the LIBS signal intensity and attain the best signal to noise ratio. The parametric dependence studies were important to improve the limit of detection of trace amounts of toxic elements present inside stones. The carcinogenic metals detected in kidney stones were chromium, cadmium, lead, zinc, phosphate, and vanadium. The results achieved from LIBS system were also compared with the inductively coupled plasma-mass spectrometry analysis and the concentration detected with both techniques was in very good agreement. The plasma parameters (electron temperature and density) for SP-LIBS system were also studied and their dependence on incident laser energy and delay time was investigated as well.

20 kHz toluene planar laser-induced fluorescence imaging of a jet in nearly sonic crossflow

NASA Astrophysics Data System (ADS)

Miller, V. A.; Troutman, V. A.; Mungal, M. G.; Hanson, R. K.

2014-10-01

This manuscript describes continuous, high-repetition-rate (20 kHz) toluene planar laser-induced fluorescence (PLIF) imaging in an expansion tube impulse flow facility. Cinematographic image sequences are acquired that visualize an underexpanded jet of hydrogen in Mach 0.9 crossflow, a practical flow configuration relevant to aerospace propulsion systems. The freestream gas is nitrogen seeded with toluene; toluene broadly absorbs and fluoresces in the ultraviolet, and the relatively high quantum yield of toluene produces large signals and high signal-to-noise ratios. Toluene is excited using a commercially available, frequency-quadrupled (266 nm), high-repetition-rate (20 kHz), pulsed (0.8-0.9 mJ per pulse), diode-pumped solid-state Nd:YAG laser, and fluorescence is imaged with a high-repetition-rate intensifier and CMOS camera. The resulting PLIF movie and image sequences are presented, visualizing the jet start-up process and the dynamics of the jet in crossflow; the freestream duration and a measure of freestream momentum flux steadiness are also inferred. This work demonstrates progress toward continuous PLIF imaging of practical flow systems in impulse facilities at kHz acquisition rates using practical, turn-key, high-speed laser and imaging systems.

Detection of significant differences between absorption spectra of neutral helium and low temperature photoionized helium plasmas

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

Bartnik, A.; Wachulak, P.; Fiedorowicz, H.

2013-11-15

In this work, spectral investigations of photoionized He plasmas were performed. The photoionized plasmas were created by irradiation of helium stream, with intense pulses from laser-plasma extreme ultraviolet (EUV) source. The EUV source was based on a double-stream Xe/Ne gas-puff target irradiated with 10 ns/10 J Nd:YAG laser pulses. The most intense emission from the source spanned a relatively narrow spectral region below 20 nm, however, spectrally integrated intensity at longer wavelengths was also significant. The EUV radiation was focused onto a gas stream, injected into a vacuum chamber synchronously with the EUV pulse. The long-wavelength part of the EUVmore » radiation was used for backlighting of the photoionized plasmas to obtain absorption spectra. Both emission and absorption spectra in the EUV range were investigated. Significant differences between absorption spectra acquired for neutral helium and low temperature photoionized plasmas were demonstrated for the first time. Strong increase of intensities and spectral widths of absorption lines, together with a red shift of the K-edge, was shown.« less

A quantum dynamics study of the benzopyran ring opening guided by laser pulses

NASA Astrophysics Data System (ADS)

Saab, Mohamad; Doriol, Loïc Joubert; Lasorne, Benjamin; Guérin, Stéphane; Gatti, Fabien

2014-10-01

The ring-opening photoisomerization of benzopyran, which occurs via a photochemical route involving a conical intersection, has been studied with quantum dynamics calculations using the multi-configuration time-dependent Hartree method (MCTDH). We introduce a mechanistic strategy to control the conversion of benzopyran to merocyanine with laser pulses. We use a six-dimensional model developed in a previous work for the potential energy surfaces (PES) based on an extension of the vibronic-coupling Hamiltonian model (diabatization method by ansatz), which depends on the most active degrees of freedom. The main objective of these quantum dynamics simulations is to provide a set of strategies that could help experimentalists to control the photoreactivity vs. photostability ratio (selectivity). In this work we present: (i) a pump-dump technique used to control the photostability, (ii) a two-step strategy to enhance the reactivity of the system: first, a pure vibrational excitation in the electronic ground state that prepares the system and, second, an ultraviolet excitation that brings the system to the first adiabatic electronic state; (iii) finally the effect of a non-resonant pulse (Stark effect) on the dynamics.

Rare-gas-cluster explosions under irradiation by intense short XUV pulses

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

Hoffmann, K.; Murphy, B.; Kandadai, N.

High-intensity, extreme-ultraviolet (XUV) femtosecond interactions with large rare-gas clusters of xenon and argon have been studied at a wavelength of 38 nm. Pulses of XUV radiation with nJ energy are produced by high-order harmonic conversion from a 35-fs, near-infrared, terawatt laser. Mass resolved ion spectra show charge states up to Xe{sup 8+} and Ar{sup 4+}. Kinetic-energy measurements of ions and electrons indicate that a nanoplasma is formed and a hydrodynamic cluster explosion ensues after heating by the short wavelength pulse. It appears that the observed charge states and electron temperatures are consistent with sequential, single-photon ionization and collisional ionization ofmore » ions that have had their ionization potential depressed by plasma continuum lowering in the cluster nanoplasma.« less

A four kHz repetition rate compact TEA CO2 laser

NASA Astrophysics Data System (ADS)

Zheng, Yijun; Tan, Rongqing

2013-09-01

A compact transversely excited atmospheric (TEA) CO2 laser with high repetition-rate was reported. The size of the laser is 380 mm×300 mm×200 mm, and the discharge volume is 12×103 mm3. The laser cavity has a length of 320mm and consists of a totally reflective concave mirror with a radius of curvature of 4 m (Cu metal substrate coated with Au) and a partially reflecting mirror. The ultraviolet preionization makes the discharge even and stable，the output energy can be as high as 28 mJ under the circumstance of free oscillation, and the width of the light pulse is 60ns．To acquire the high wind velocity, a turbocharger is used in the system of the fast-gas flow cycle. When the wind speed is 100m/s, the repetition rate of the transversely excited atmospheric CO2 laser is up to 2 kHz. On this basis, a dual modular structure with two sets of the gas discharge unit is adopted to obtain a higher pulse repetition frequency output. The dual discharge unit composed two sets of electrodes and two sets of turbo fan. Alternate trigger technology is used to make the two sets of discharge module work in turn with repetition frequency of 2 kHz, the discharge interval of two sets of the gas discharge unit can be adjusted continuously from 20 microseconds to 250 microseconds. Under the conditions of maintaining the other parameters constant, the repetition frequency of the laser pulse is up to 4 kHz. The total size of laser with dual modular structure is 380mm×520mm×200mm, and the discharge volume is 24×103 mm3 with the cavity length of 520mm.

Comparison of the effect of soft-core potentials and Coulombic potentials on bremsstrahlung during laser matter interaction

NASA Astrophysics Data System (ADS)

Pandit, Rishi R.; Becker, Valerie R.; Barrington, Kasey; Thurston, Jeremy; Ramunno, Lora; Ackad, Edward

2018-04-01

An intense, short laser pulse incident on rare-gas clusters can produce nano-plasmas containing energetic electrons. As these electrons undergo scattering, from both phonons and ions, they emit bremsstrahlung radiation. Here, we compare a theory of bremsstrahlung emission appropriate for the interaction of intense lasers with matter using soft-core potentials and Coulombic potentials. A new scaling for the radiation cross-section and the radiated power via bremsstrahlung is derived for a soft-core potential (which depends on the potential depth) and compared with the Coulomb potential. Calculations using the new scaling are performed for electrons in vacuum ultraviolet, infrared and mid-infrared laser pulses. The radiation cross-section and the radiation power via bremsstrahlung are found to increase rapidly with increases in the potential depth of up to around 200 eV and then become mostly saturated for larger depths while remaining constant for the Coulomb potential. In both cases, the radiation cross-section and the radiation power of bremsstrahlung decrease with increases in the laser wavelength. The ratio of the scattering amplitude for the soft-core potential and that for the Coulombic potential decreases exponentially with an increase in momentum transfer. The bremsstrahlung emission by electrons in plasmas may provide a broadband light source for diagnostics.

Paper un-printing: using lasers to remove toner-print in order to reuse office paper

NASA Astrophysics Data System (ADS)

Leal-Ayala, D. R.; Allwood, J. M.; Counsell, T. A. M.

2011-12-01

In this article, lasers in the ultraviolet, visible and infrared light spectra working with pulse widths in the nanosecond range are applied to a range of toner-paper combinations to determine their ability to remove toner. If the laser energy fluence can be chosen to stay below the ablation threshold of paper at the same time that it surpasses that of toner, paper could be cleaned and re-used instead of being recycled or disposed into a landfill. This could significantly reduce the environmental impact of paper production and use. Although there are a variety of paper conservation studies which have investigated the effects of laser radiation on blank and soiled paper, none has previously explored toner-print removal from paper by laser ablation. Colour analysis under the L ∗ a ∗ b ∗ colour space and SEM examination of the outcome indicate that it is possible to remove toner from paper without damaging and discolouring the substrate. Best results are obtained when employing visible radiation at a wavelength of 532 nm working with a pulse width of 4 ns and energy fluences under 1.6 J/cm2. This means that it is technically feasible to remove toner-print for paper re-use.

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

Spectral and ion emission features of laser-produced Sn and SnO2 plasmas

NASA Astrophysics Data System (ADS)

Hui, Lan; Xin-Bing, Wang; Du-Luo, Zuo

2016-03-01

We have made a detailed comparison of the atomic and ionic debris, as well as the emission features of Sn and SnO2 plasmas under identical experimental conditions. Planar slabs of pure metal Sn and ceramic SnO2 are irradiated with 1.06 μm, 8 ns Nd:YAG laser pulses. Fast photography employing an intensified charge coupled device (ICCD), optical emission spectroscopy (OES), and optical time of flight emission spectroscopy are used as diagnostic tools. Our results show that the Sn plasma provides a higher extreme ultraviolet (EUV) conversion efficiency (CE) than the SnO2 plasma. However, the kinetic energies of Sn ions are relatively low compared with those of SnO2. OES studies show that the Sn plasma parameters (electron temperature and density) are lower compared to those of the SnO2 plasma. Furthermore, we also give the effects of the vacuum degree and the laser pulse energy on the plasma parameters. Project supported by the National Natural Science Foundation of China (Grant No. 11304235) and the Director Fund of WNLO, China.

Multispectral therapeutic endoscopy imaging and intervention

NASA Astrophysics Data System (ADS)

Bala, John L.; Schwaitzberg, Steven D.

2007-02-01

With the debut of antibiotic drug therapy, and as a result of its ease of use and general success in treating infection, drugs have become the treatment of choice for most bacterial infections. However, the advent of multiple, very aggressive drug-resistant bacteria, an increasing population which cannot tolerate drugs, and the high cost of drug therapy suggest that a new modality for treating infections is needed. The complex interplay of clonal spread, persistence, transfer of resistance elements and cell-to-cell interaction all contribute to the difficulty in developing drugs to treat new antibiotic-resistant bacterial strains. A dynamic non-drug system, using extant pulsed ultraviolet lightwave technology to kill infection, is being developed to destroy pathogens. This paper theorizes that the shock effect of pulsed xenon's high energy ultraviolet pulses at wavelengths between 250-270nm separates the bacteria's DNA bands, and, subsequently, destroys them. Preliminary laboratory tests have demonstrated the ability of the technology to destroy Staphylococcus aureus, Pseudomonas aeruginosa Escherichia coli, Helicobacter pylori, Acinetobacter baumannii, Klebsiella punemonia, Bacillus subtillis, and Aspergillus fumigates at penetration depths of greater than 3mm in fluids with 100% effectiveness in less than five seconds of exposure to pulsed xenon lightwaves. Micro Invasive Technology, Inc is developing .pulsed xenon therapeutic catheters and endoscopic instruments for internal antimicrobial eradication and topographical devices for prophylactic wound, burn and surgical entrance/exit site sterilization. Pulsed Xenon light sources have a broad optical spectrum (190-1200nm), and can generate light pulses with sufficient energy for combined imaging and therapeutic intervention by multiplexing a fiber optic pathway into the body. In addition, Pulsed Xenon has proven ability to activate photo reactive dyes; share endoscopic lightguides with lasers while, simultaneously, capturing high quality visual and activated video images.

Ultraviolet laser beam monitor using radiation responsive crystals

DOEpatents

McCann, Michael P.; Chen, Chung H.

1988-01-01

An apparatus and method for monitoring an ultraviolet laser beam includes disposing in the path of an ultraviolet laser beam a substantially transparent crystal that will produce a color pattern in response to ultraviolet radiation. The crystal is exposed to the ultraviolet laser beam and a color pattern is produced within the crystal corresponding to the laser beam intensity distribution therein. The crystal is then exposed to visible light, and the color pattern is observed by means of the visible light to determine the characteristics of the laser beam that passed through crystal. In this manner, a perpendicular cross sectional intensity profile and a longitudinal intensity profile of the ultraviolet laser beam may be determined. The observation of the color pattern may be made with forward or back scattered light and may be made with the naked eye or with optical systems such as microscopes and television cameras.

Short-range optical air data measurements for aircraft control using rotational Raman backscatter.

PubMed

Fraczek, Michael; Behrendt, Andreas; Schmitt, Nikolaus

2013-07-15

A first laboratory prototype of a novel concept for a short-range optical air data system for aircraft control and safety was built. The measurement methodology was introduced in [Appl. Opt. 51, 148 (2012)] and is based on techniques known from lidar detecting elastic and Raman backscatter from air. A wide range of flight-critical parameters, such as air temperature, molecular number density and pressure can be measured as well as data on atmospheric particles and humidity can be collected. In this paper, the experimental measurement performance achieved with the first laboratory prototype using 532 nm laser radiation of a pulse energy of 118 mJ is presented. Systematic measurement errors and statistical measurement uncertainties are quantified separately. The typical systematic temperature, density and pressure measurement errors obtained from the mean of 1000 averaged signal pulses are small amounting to < 0.22 K, < 0.36% and < 0.31%, respectively, for measurements at air pressures varying from 200 hPa to 950 hPa but constant air temperature of 298.95 K. The systematic measurement errors at air temperatures varying from 238 K to 308 K but constant air pressure of 946 hPa are even smaller and < 0.05 K, < 0.07% and < 0.06%, respectively. A focus is put on the system performance at different virtual flight altitudes as a function of the laser pulse energy. The virtual flight altitudes are precisely generated with a custom-made atmospheric simulation chamber system. In this context, minimum laser pulse energies and pulse numbers are experimentally determined, which are required using the measurement system, in order to meet measurement error demands for temperature and pressure specified in aviation standards. The aviation error margins limit the allowable temperature errors to 1.5 K for all measurement altitudes and the pressure errors to 0.1% for 0 m and 0.5% for 13000 m. With regard to 100-pulse-averaged temperature measurements, the pulse energy using 532 nm laser radiation has to be larger than 11 mJ (35 mJ), regarding 1-σ (3-σ) uncertainties at all measurement altitudes. For 100-pulse-averaged pressure measurements, the laser pulse energy has to be larger than 95 mJ (355 mJ), respectively. Based on these experimental results, the laser pulse energy requirements are extrapolated to the ultraviolet wavelength region as well, resulting in significantly lower pulse energy demand of 1.5 - 3 mJ (4-10 mJ) and 12-27 mJ (45-110 mJ) for 1-σ (3-σ) 100-pulse-averaged temperature and pressure measurements, respectively.

Extreme ultraviolet probing of nonequilibrium dynamics in high energy density germanium

NASA Astrophysics Data System (ADS)

Principi, E.; Giangrisostomi, E.; Mincigrucci, R.; Beye, M.; Kurdi, G.; Cucini, R.; Gessini, A.; Bencivenga, F.; Masciovecchio, C.

2018-05-01

Intense femtosecond infrared laser pulses induce a nonequilibrium between thousands of Kelvin hot valence electrons and room-temperature ions in a germanium sample foil. The evolution of this exotic state of matter is monitored with time-resolved extreme ultraviolet absorption spectroscopy across the Ge M2 ,3 edge (≃30 eV ) using the FERMI free-electron laser. We analyze two distinct regimes in the ultrafast dynamics in laser-excited Ge: First, on a subpicosecond time scale, the electron energy distribution thermalizes to an extreme temperature unreachable in equilibrium solid germanium; then, during the following picoseconds, the lattice reacts strongly altering the electronic structure and resulting in melting to a metallic state alongside a breakdown of the local atomic order. Data analysis, based on a hybrid approach including both numerical and analytical calculations, provides an estimation of the electron and ion temperatures, the electron density of states, the carrier-phonon relaxation time, as well as the carrier density and lattice heat capacity under those extreme nonequilibrium conditions. Related structural anomalies, such as the occurrence of a transient low-density liquid phase and the possible drop in lattice heat capacity are discussed.

Vacuum Ultraviolet Photodissociation and Fourier Transform-Ion Cyclotron Resonance (FT-ICR) Mass Spectrometry: Revisited.

PubMed

Shaw, Jared B; Robinson, Errol W; Paša-Tolić, Ljiljana

2016-03-15

We revisited the implementation of 193 nm ultraviolet photodissociation (UVPD) within the ion cyclotron resonance (ICR) cell of a Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometer. UVPD performance characteristics were examined in the context of recent developments in the understanding of UVPD and in-cell tandem mass spectrometry. Efficient UVPD and photo-ECD of a model peptide and proteins within the ICR cell of a FT-ICR mass spectrometer are accomplished through appropriate modulation of laser pulse timing, relative to ion magnetron motion and the potential applied to an ion optical element upon which photons impinge. It is shown that UVPD yields efficient and extensive fragmentation, resulting in excellent sequence coverage for model peptide and protein cations.

Laser-Induced Incandescence Calibration via Gravimetric Sampling

NASA Technical Reports Server (NTRS)

VanderWal, R. L.; Zhou, Z.; Choi, M. Y.

1995-01-01

Various beam imaging and/or sheet forming optics delivered light at 1064 nm from a pulsed Nd:YAG laser for use either as a beam of 3 mm radius or as a laser sheet. Imaging measurements were performed with a grated intensified array camera equipped with an ultraviolet f4.5 lens and a 40 mm extension tube. Point measurements were performed using an ultraviolet 250 mm focal length lens to collect and focus the laser induced incandescence (LII) signal into a 1 meter long quartz optical fiber which directed the LII signal to a 1/4 meter monochromator. An aperture preceding the lens restricted the signal collection region to 1 cm along the laser beam at the center of the gravimetric chimney. Signals from the PMT were processed by a boxcar integrator whereas the images were captured digitally using a frame-grabber with 16 MByte of on-board memory. Both 'point' and planar measurements were made with detector gates of 250 ns to minimize possible morphology bias in collection of the LII signal. Additionally, the imaging measurements were performed with broadband spectral collection of the LII signal to maximize the signal and again minimize any potential effects of morphology dependent heating and/or cooling rates. Digital delay generators controlled the firing of he laser, detector gates and data acquisition. Neutral density filters were used for both sets of measurements to maintain signal levels within linear dynamic ranges of the detectors, the range being determined prior to experiments.

Coherence properties of the radiation from FLASH

NASA Astrophysics Data System (ADS)

Schneidmiller, E. A.; Yurkov, M. V.

2016-02-01

Free electron LASer in Hamburg is the first free electron laser user facility operating in the vacuum ultraviolet and soft X-ray wavelength range. Many user experiments require knowledge of the spatial and temporal coherence properties of the radiation. In this paper, we present a theoretical analysis of the coherence properties of the radiation for the fundamental and for the higher odd frequency harmonics. We show that temporal and spatial coherence reach their maxima close to the free electron laser (FEL) saturation but may degrade significantly in the post-saturation regime. We also find that the pointing stability of short FEL pulses is limited due to the fact that nonazimuthal FEL eigenmodes are not sufficiently suppressed. We discuss possible ways for improving the degree of transverse coherence and the pointing stability.

A High-Average-Power Free Electron Laser for Microfabrication and Surface Applications

NASA Technical Reports Server (NTRS)

Dylla, H. F.; Benson, S.; Bisognano, J.; Bohn, C. L.; Cardman, L.; Engwall, D.; Fugitt, J.; Jordan, K.; Kehne, D.; Li, Z.;

Charge transfer in dissociating iodomethane and fluoromethane molecules ionized by intense femtosecond X-ray pulses

PubMed Central

Boll, Rebecca; Erk, Benjamin; Coffee, Ryan; Trippel, Sebastian; Kierspel, Thomas; Bomme, Cédric; Bozek, John D.; Burkett, Mitchell; Carron, Sebastian; Ferguson, Ken R.; Foucar, Lutz; Küpper, Jochen; Marchenko, Tatiana; Miron, Catalin; Patanen, Minna; Osipov, Timur; Schorb, Sebastian; Simon, Marc; Swiggers, Michelle; Techert, Simone; Ueda, Kiyoshi; Bostedt, Christoph; Rolles, Daniel; Rudenko, Artem

2016-01-01

Ultrafast electron transfer in dissociating iodomethane and fluoromethane molecules was studied at the Linac Coherent Light Source free-electron laser using an ultraviolet-pump, X-ray-probe scheme. The results for both molecules are discussed with respect to the nature of their UV excitation and different chemical properties. Signatures of long-distance intramolecular charge transfer are observed for both species, and a quantitative analysis of its distance dependence in iodomethane is carried out for charge states up to I21+. The reconstructed critical distances for electron transfer are in good agreement with a classical over-the-barrier model and with an earlier experiment employing a near-infrared pump pulse. PMID:27051675

The effect of viewing angle on the spectral behavior of a Gd plasma source near 6.7 nm

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

O'Gorman, Colm; Li Bowen; Cummins, Thomas

2012-04-02

We have demonstrated the effect of viewing angle on the extreme ultraviolet (EUV) emission spectra of gadolinium (Gd) near 6.7 nm. The spectra are shown to have a strong dependence on viewing angle when produced with a laser pulse duration of 10 ns, which may be attributed to absorption by low ion stages of Gd and an angular variation in the ion distribution. Absorption effects are less pronounced at a 150-ps pulse duration due to reduced opacity resulting from plasma expansion. Thus for evaluating source intensity, it is necessary to allow for variation with both viewing angle and target orientation.

A low-cost, high-efficiency and high-flexibility surface modification technology for a black bisphenol A polycarbonate board

NASA Astrophysics Data System (ADS)

Wang, Suhuan; Liu, Jianguo; Lv, Ming; Zeng, Xiaoyan

2014-09-01

In this paper, a low-cost, high-efficiency and high-flexibility surface modification technology for polymer materials was achieved at high laser scanning speeds (600-1000 mm s-1) and using an all-solid state, Q-switched, high-average power, and nanosecond pulse ultraviolet (355 nm wavelength) laser. During the surface modification of a very important engineering plastic, i.e., black bisphenol A polycarbonate (BAPC) board, it was found that different laser parameters (e.g., laser fluence and pulse frequency) were able to result in different surface microstructures (e.g., many tiny protuberances or a porous microstructure with periodical V-type grooves). After the modification, although the total relative content of the oxygen-containing groups (e.g., Csbnd O and COO-) on the BAPC surface increased, however, the special microstructures played a deciding role in the surface properties (e.g., contact angle and surface energy) of the BAPC. The change trend of the water contact angle on the BAPC surface was with an obvious increase, that of the diiodomethane contact angle was with a most decrease, and that of the ethylene glycol contact angle was between the above two. It showed that the wetting properties of the three liquids on the modified BAPC surface were different. Basing on the measurements of the contact angles of the three liquids, and according to the Young equation and the Lifshitz van der Waals and Lewis acid-base theory, the BAPC surface energy after the modification was calculated. The results were that, in a broad range of laser fluences, pulse frequencies and scanning speeds, the surface energy had a significant increase (e.g., from the original of about 44 mJ m-2 to the maximum of about 70 mJ m-2), and the higher the laser pulse frequency, the more significant the increase. This would be very advantageous to fabricate the high-quality micro-devices and micro-systems on the modified surface.

Ultrashort x-ray backlighters and applications

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

Umstadter, D., University of Michigan

Previously, using ultrashort laser pulses focused onto solid targets, we have experimentally studied a controllable ultrafast broadband radiation source in the extreme ultraviolet for time-resolved dynamical studies in ultrafast science [J. Workman, A. Maksimchuk, X. Llu, U. Ellenberger, J. S. Coe, C.-Y. Chien, and D. Umstadter, ``Control of Bright Picosecond X-Ray Emission from Intense Sub- Picosecond Laser-Plasma Interactions,`` Phys. Rev. Lett. 75, 2324 (1995)]. Once armed with a bright ultrafast broadband continuum x-ray source and appropriate detectors, we used the source as a backlighter to study a remotely produced plasma. The application of the source to a problem relevant tomore » high-density matter completes the triad: creating and controlling, efficiently detecting, and applying the source. This work represented the first use of an ultrafast laser- produced x-ray source as a time-resolving probe in an application relevant to atomic, plasma and high-energy-density matter physics. Using the x-ray source as a backlighter, we adopted a pump-probe geometry to investigate the dynamic changes in electronic structure of a thin metallic film as it is perturbed by an ultrashort laser pulse. Because the laser deposits its energy in a skin depth of about 100 {Angstrom} before expansion occurs, up to gigabar pressure shock waves lasting picosecond in duration have been predicted to form in these novel plasmas. This raises the possibility of studying high- energy-density matter relevant to inertial confinement fusion (ICF) and astrophysics in small-scale laboratory experiments. In the past, time-resolved measurements of K-edge shifts in plasmas driven by nanosecond pulses have been used to infer conditions in highly compressed materials. In this study, we used 100-fs laser pulses to impulsively drive shocks into a sample (an untamped 1000 {Angstrom} aluminum film on 2000 {Angstrom} of parylene-n), measuring L-edge shifts.« less

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

An Experimental Characterization System for Deep Ultra-Violet (UV) Photoresists

NASA Astrophysics Data System (ADS)

Drako, Dean M.; Partlo, William N.; Oldham, William G.; Neureuther, Andrew R.

1989-08-01

A versatile system designed specifically for experimental automated photoresist characterization has been constructed utilizing an excimer laser source for exposure at 248nm. The system was assembled, as much as possible, from commercially available components in order to facilitate its replication. The software and hardware are completely documented in a University of California-Berkeley Engineering Research Lab Memo. An IBM PC-AT compatible computer controls an excimer laser, operates a Fourier Transform Infrared (FTIR) Spectrometer, measures and records the energy of each laser pulse (incident, reflected, and transmitted), opens and closes shutters, and operates two linear stages for sample movement. All operations (except FTIR data reduction) are managed by a control program written in the "C" language. The system is capable of measuring total exposure dose, performing bleaching measurements, creating and recording exposure pulse sequences, and generating exposure patterns suitable for multiple channel monitoring of the development. The total exposure energy, energy per pulse, and pulse rate are selectable over a wide range. The system contains an in-situ Fourier Transform Infrared Spectrometer for qualitative and quantitative analysis of the photoresist baking and exposure processes (baking is not done in-situ). FIIR may be performed in transmission or reflection. The FTIR data will form the basis of comprehensive multi-state resist models. The system's versatility facilitates the development of new automated and repeatable experiments. Simple controlling software, utilizing the provided interface sub-routines, can be written to control new experiments and collect data.

Application of the UV laser printing technique to soft gelatin capsules containing titanium dioxide in the shells.

PubMed

Hosokawa, Akihiro; Kato, Yoshiteru

2012-03-01

The purpose of this study was to examine application of ultraviolet (UV) laser irradiation to printing soft gelatin capsules containing titanium dioxide (TiO(2)) in the shells and to study effect of UV laser power on the color strength of printing on the soft gelatin capsules. Size 6 Oval type soft gelatin capsules of which shells contained 0.685% TiO(2) and 0.005% ferric dioxide were used in this study. The capsules were irradiated pulsed UV laser at a wavelength 355 nm. The color strength of the printed capsules was determined by a spectrophotometer as total color difference (dE). The soft gelatin capsules which contained TiO(2) in the shells could be printed gray by the laser. Many black particles, which were associated with the printing, were formed at the colored parts of the shells. It was found that there were two inflection points in relationship between output laser energy of a pulse and dE. Below the lower point, the capsules were not printed. From the lower point to the upper point, the capsules were printed gray and total color difference of the printing increased linearly in proportion with the output laser energy. Beyond the upper point, total color difference showed saturation because of micro-bubbles formation at the laser irradiated spot. Soft gelatin capsules containing TiO(2) in the shells could be performed stable printing using the UV laser printing technique. Color strength of the printing could be controlled by regulating the laser energy between the two inflection points.

Propagation d'impulsions femtosecondes térawatts dans l'atmosphère et applications

NASA Astrophysics Data System (ADS)

Méjean, G.

2005-11-01

Propagation of femtosecond terawatt laser in atmosphere and applications When ultrasshort and high-power laser pulses propagate across the atmosphere, self-guided filaments of 100 μm radius are formed. They result from a balance between Kerr self-focusing and defocusing by the plasma generated by multiphoton ionisation. During this work, we showed that the white light spectrum generated in filament spans from the infrared (4.5 μm) to the ultraviolet (230 nm) thanks to Third Harmonic Generation and self-phase modulation. We charaterized the propagation under different conditions (rain, smog, turbulence) to developp different atmospheric applications. In particular, we demostrated multi-parameters LIDAR for relative humidity as well as atmospheric pollution remote sensing. Furthermore, it is possible to detect and to identify biological aerosols or solid targets (LIBS) at remote distances, by non-linear processes induced in situ by the high intensity delivered by filaments. Moreover, we demonstrated that guiding and triggering high-voltage discharge thanks to a femsecond high-powered pulse is possible even under a rain with an efficiency comparable to that observed in dry air. We also impoved the efficiency of a two pulses configurations (a femtosecond pulse and a subsequent nanosecond pulse). These results raise hope that lightning could be triggered and guided by laser pulses in the future. Les impulsions laser ultra-brèves (fs) et ultra-intenses (TW) forment, au cours de leur propagation non-linéaire dans l'atmosphère, des structures auto-guidées, d'une centaine de microns de diamètre, appelées filaments. Ces filaments résultent d'un équilibre dynamique entre l'effet Kerr qui focalise le faisceau et la défocalisation due au plasma généré au sein de ceux-ci. Au cours des différentes études rapportées ici, nous avons mesuré que le spectre de lumière blanche issue de l'automodulation de phase et de la génération de troisième harmonique s'étend de l'ultraviolet (230 nm) à l'infrarouge (4,5 μm). De même, la propagation dans l'air, sous différentes conditions (pluie, brouillard, turbulence), des faisceaux térawatts femtosecondes a été caractérisée afin de développer des applications atmosphériques. Il nous a ainsi été possible de développer le LIDAR à lumière blanche pour réaliser des mesures préliminaires d'ozone et d'aérosols simultanément. De même, grâce à la propagation fortement non-linéaire du faisceau qui permet de transporter des hautes intensités sur de longue distance, nous avons pu détecter et identifier, à distance, des aérosols biologiques et des cibles solides (LIBS) en induisant in situ des effets non-linéaires. Enfin, nous avons montré que le déclenchement et le guidage de décharges de haute tension par une impulsion laser femtoseconde sous la pluie reste possible avec une efficacité comparable à l'atmosphère sèche. D'autre part, une configuration à double impulsion laser augmente l'efficacité de déclenchement des décharges. Ces résultats nous rapproche de la perspective de déclenchement et guidage de foudre par laser.

Sharpening of the 6.8 nm peak in an Nd:YAG laser produced Gd plasma by using a pre-formed plasma

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

Tian, Yong; Song, Xiaolin; Xie, Zhuo

For effective use of a laser-produced-plasma (LPP) light source, an LPP is desired to emit a narrow spectral peak because the reflection spectrum of multilayer mirrors for guiding emission from the source is very narrow. While a Gd plasma has been studied extensively as an extreme ultraviolet (EUV) light source at around 6.8 nm, where La/B{sub 4}C multilayer is reported to have a high reflectivity with a bandwidth of about 0.6 %, all previous works using an Nd:YAG laser reported very broad spectra. This paper reports the first narrowing of the 6.8 nm peak in the case of using anmore » Nd:YAG laser to generate a Gd plasma by using a pre-pulse. The best peak narrowing is observed when a pre-formed plasma is heated by a 1064 nm main laser pulse with a duration of 10 ns at the irradiation density of 4x 10{sup 11} W/cm{sup 2} at a delay time of 50 ns after the pre-pulse irradiation. The observed spectral width of about 0.3 nm is about one fifth of the value for no pre-formed plasma. The peak wavelength of the 6.8 nm band shifted to a longer wavelength side and the peak was broadened both for lower and higher laser irradiation density. It is discussed that this robustness of the peak position of the 6.8 nm Gd peak against temperature change is suitable to achieve a narrow bandwidth from an LPP generated on solid. The observed spectra are compared with those previously reported in various conditions.« less

Spectral irradiance of singly and doubly ionized zinc in low-intensity laser-plasma ultraviolet light sources

NASA Astrophysics Data System (ADS)

Szilagyi, John; Parchamy, Homaira; Masnavi, Majid; Richardson, Martin

2017-01-01

The absolute spectral irradiances of laser-plasmas produced from planar zinc targets are determined over a wavelength region of 150 to 250 nm. Strong spectral radiation is generated using 60 ns full-width-at-half-maximum, 1.0 μm wavelength laser pulses with incident laser intensities as low as ˜5 × 108 W cm-2. A typical radiation conversion efficiency of ˜2%/2πsr is measured. Numerical calculations using a comprehensive radiation-hydrodynamics model reveal the strong experimental spectra to originate mainly from 3d94s4p-3d94s2, 3d94s4d-3d94s4p, and 3d94p-3d94s, 3d94d-3d94p unresolved-transition arrays in singly and doubly ionized zinc, respectively.

Fabrication of 10 μm-scale conductive Cu patterns by selective laser sintering of Cu complex ink

NASA Astrophysics Data System (ADS)

Min, Hyungsuk; Lee, Byoungyoon; Jeong, Sooncheol; Lee, Myeongkyu

2017-02-01

A Cu complex ink was synthesized using copper formate as a precursor and its potential for laser patterning was investigated. The Cu ink was spin-coated onto a substrate and the coated film was space-selectively sintered using a nanosecond-pulsed ultraviolet laser. The unexposed Cu ink could be removed from the film by rinsing it with the dispersing agent used to synthesize the ink, disclosing a conductive Cu pattern. A minimum resistivity of 8.46×10-5 Ω cm was obtained for the Cu lines with 10-20 μm widths. The feasibility of this method for metallization was demonstrated by fabricating a complex Cu electric circuit on an indium tin oxide-coated glass substrate. The selective laser sintering approach provides a simple, cost-effective alternative to conventional lithography for the production of electrode or metallization patterns.

Laser diodes with 353 nm wavelength enabled by reduced-dislocation-density AlGaN templates

DOE PAGES

Crawford, Mary H.; Allerman, Andrew A.; Armstrong, Andrew M.; ...

2015-10-30

We fabricated optically pumped and electrically injected ultraviolet (UV) lasers on reduced-threading-dislocation-density (reduced-TDD) AlGaN templates. The overgrowth of sub-micron-wide mesas in the Al 0.32Ga 0.68N templates enabled a tenfold reduction in TDD, to (2–3) × 10 8 cm –2. Optical pumping of AlGaN hetero-structures grown on the reduced-TDD templates yielded a low lasing threshold of 34 kW/cm 2 at 346 nm. Room-temperature pulsed operation of laser diodes at 353 nm was demonstrated, with a threshold of 22.5 kA/cm 2. Furthermore, reduced-TDD templates have been developed across the entire range of AlGaN compositions, presenting a promising approach for extending laser diodesmore » into the deep UV.« less

Collisional Removal of O2 (c(sup 1) Sigma(sup-)(sub u), nu=9) by O2, N2, and He

NASA Technical Reports Server (NTRS)

Copeland, Richard A.; Knutsen, Karen; Onishi, Marc E.; Yalcin, Talat

1996-01-01

The collisional removal Of 02 molecules in selected vibrational levels of the c state is studied using a two-laser double-resonance technique. The output of the first laser excites the 02 to nu = 9 or 10 of the c Sigma - state, and the ultraviolet output of the second laser monitors specific rovibrational levels via resonance-enhanced ionization. The temporal evolution of the c Sigma u state vibrational level is observed by scanning the time delay between the two pulsed lasers. As the rate constants for 02 and N2 are similar in magnitude, N2 collisions dominate the removal rate in the earth's atmosphere. For v= 10 colliding with 02, we find a removal rate constant that is 2-5 times that for v=9 and that single quantum collision cascade is an important pathway for removal.

Optogalvanic wavelength calibration for laser monitoring of reactive atmospheric species

NASA Technical Reports Server (NTRS)

Webster, C. R.

1982-01-01

Laser-based techniques have been successfully employed for monitoring atmospheric species of importance to stratospheric ozone chemistry or tropospheric air quality control. When spectroscopic methods using tunable lasers are used, a simultaneously recorded reference spectrum is required for wavelength calibration. For stable species this is readily achieved by incorporating into the sensing instrument a reference cell containing the species to be monitored. However, when the species of interest is short-lived, this approach is unsuitable. It is proposed that wavelength calibration for short-lived species may be achieved by generating the species of interest in an electrical or RF discharge and using optogalvanic detection as a simple, sensitive, and reliable means of recording calibration spectra. The wide applicability of this method is emphasized. Ultraviolet, visible, or infrared lasers, either CW or pulsed, may be used in aircraft, balloon, or shuttle experiments for sensing atoms, molecules, radicals, or ions.

The development of fluorides for high power laser optics

NASA Astrophysics Data System (ADS)

Ready, J. F.; Vora, H.

1980-07-01

The laser assisted thermonuclear fusion program has need for improved optical materials with high transmission in the ultraviolet, and with low values of nonlinear index of refraction. Lithium fluoride possesses a combination of optical properties which are of use. Single crystalline LiF is limited by low mechanical strength. The technique of press forging to increase the mechanical strength is investigated. LiF single crystals were press forged over the temperature range 300 - 600 deg C to produce fine grained polycrystalline material. Optical homogenity at 633, stress birefringence, scattering at 633, residual absorption over the spectral range 339 - 3800 nm, and laser damage thresholds for 1 ns, 1064 nm and 700 ps, 266 nm laser pulses are evaluated. Single crystals can be press forged without seriously degrading their optical properties. Yield strength in compression, proportional limit and fracture strength in 3 and 4 point bending, fracture energy, and threshold for microyield are discussed.

Nanometer-scale ablation using focused, coherent extreme ultraviolet/soft x-ray light

DOEpatents

Menoni, Carmen S [Fort Collins, CO; Rocca, Jorge J [Fort Collins, CO; Vaschenko, Georgiy [San Diego, CA; Bloom, Scott [Encinitas, CA; Anderson, Erik H [El Cerrito, CA; Chao, Weilun [El Cerrito, CA; Hemberg, Oscar [Stockholm, SE

2011-04-26

Ablation of holes having diameters as small as 82 nm and having clean walls was obtained in a poly(methyl methacrylate) on a silicon substrate by focusing pulses from a Ne-like Ar, 46.9 nm wavelength, capillary-discharge laser using a freestanding Fresnel zone plate diffracting into third order is described. Spectroscopic analysis of light from the ablation has also been performed. These results demonstrate the use of focused coherent EUV/SXR light for the direct nanoscale patterning of materials.

Matching the laser wavelength to the absorption properties of matrices increases the ion yield in UV-MALDI mass spectrometry.

PubMed

Wiegelmann, Marcel; Soltwisch, Jens; Jaskolla, Thorsten W; Dreisewerd, Klaus

2013-09-01

A high analytical sensitivity in ultraviolet matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) is only achieved if the laser wavelength corresponds to a high optical absorption of the matrix. Laser fluence and the physicochemical properties of the compounds, e.g., the proton affinity, also influence analytical sensitivity significantly. In combination, these parameters determine the amount of material ejected per laser pulse and the ion yield, i.e., the fraction of ionized biomolecules. Here, we recorded peptide ion signal intensities as a function of these parameters. Three cinnamic acid matrices were investigated: α-cyano-4-hydroxycinnamic acid, α-cyano-4-chlorocinnamic acid, and α-cyano-2,4-difluorocinnamic acid. In addition, 2,5-dihydroxybenzoic acid was used in comparison experiments. Ion signal intensities "per laser shot" and integrated ion signal intensities were acquired over 900 consecutive laser pulses applied on distinct positions on the dried-droplet sample preparations. With respect to laser wavelength, the two standard MALDI wavelengths of 337/355 nm were investigated. Also, 305 or 320 nm was selected to account for the blue-shifted absorption profiles of the halogenated derivatives. Maximal peptide ion intensities were obtained if the laser wavelength fell within the peak of the absorption profile of the compound and for fluences two to three times the corresponding ion detection threshold. The results indicate ways for improving the analytical sensitivity in MALDI-MS, and in particular for MALDI-MS imaging applications where a limited amount of material is available per irradiated pixel.

Imprinting on empty hard gelatin capsule shells containing titanium dioxide by application of the UV laser printing technique.

PubMed

Hosokawa, Akihiro; Kato, Yoshiteru; Terada, Katsuhide

2014-08-01

The purpose of this study was to examine the application of ultraviolet (UV) laser irradiation to printing hard gelatin capsule shells containing titanium dioxide (TiO2) and to clarify how the color strength of the printing by the laser could be controlled by the power of the irradiated laser. Hard gelatin capsule shells containing 3.5% TiO2 were used in this study. The capsules were irradiated with pulsed UV laser at a wavelength of 355 nm. The color strength of the printed capsule was determined by a spectrophotometer as total color difference (dE). The capsules could be printed gray by the UV laser. The formation of many black particles which were agglomerates of oxygen-defected TiO2 was associated with the printing. In the relationship between laser peak power of a pulse and dE, there were two inflection points. The lower point was the minimal laser peak power to form the black particles and was constant regardless of the dosage forms, for example film-coated tablets, soft gelatin capsules and hard gelatin capsules. The upper point was the minimal laser peak power to form micro-bubbles in the shells and was variable with the formulation. From the lower point to the upper point, the capsules were printed gray and the dE of the printing increased linearly with the laser peak power. Hard gelatin capsule shells containing TiO2 could be printed gray using the UV laser printing technique. The color strength of the printing could be controlled by regulating the laser energy between the two inflection points.

Zinc oxide nanocolloids prepared by picosecond pulsed laser ablation in water at different temperatures

NASA Astrophysics Data System (ADS)

D'Urso, Luisa; Spadaro, Salvatore; Bonsignore, Martina; Santangelo, Saveria; Compagnini, Giuseppe; Neri, Fortunato; Fazio, Enza

2018-01-01

Zinc oxide with wide direct band gap and high exciton binding energy is one of the most promising materials for ultraviolet (UV) light-emitting devices. It further exhibits good performance in the degradation of non-biodegradable pollutants under UV irradiation. In this work, zinc oxide (ZnO) and zinc oxide/gold (ZnO/Au) nanocolloids are prepared by picosecond pulsed laser ablation (ps-PLA), using a Zn and Au metallic targets in water media at room temperature (RT) and 80°C. ZnO and Au nanoparticles (NPs) with size in the 10-50 nm range are obtained at RT, while ZnO nanorods (NRs) are formed when water is maintained at 80°C during the ps-PLA process. Au NPs, added to ZnO colloids after the ablation process, decorate ZnO NRs. The crystalline phase of all ZnO nanocolloids is wurtzite. Methylene blue dye is used to investigate the photo-catalytic activity of all the synthesised nanocolloids, under UV light irradiation.

GINGER simulations of short-pulse effects in the LEUTL FEL

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

Huang, Z.; Fawley, W.M.

While the long-pulse, coasting beam model is often used in analysis and simulation of self-amplified spontaneous emission (SASE) free-electron lasers (FELs), many current SASE demonstration experiments employ relatively short electron bunches whose pulse length is on the order of the radiation slippage length. In particular, the low-energy undulator test line (LEUTL) FEL at the Advanced Photon Source has recently lased and nominally saturated in both visible and near-ultraviolet wavelength regions with a sub-ps pulse length that is somewhat shorter than the total slippage length in the 22-m undulator system. In this paper we explore several characteristics of the short pulsemore » regime for SASE FELs with the multidimensional, time-dependent simulation code GINGER, concentrating on making a direct comparison with the experimental results from LEUTL. Items of interest include the radiation gain length, pulse energy, saturation position, and spectral bandwidth. We address the importance of short-pulse effects when scaling the LEUTL results to proposed x-ray FELs and also briefly discuss the possible importance of coherent spontaneous emission at startup.« less

Polypyrrole coated phase-change contrast agents for sono-photoacoustic imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Li, David S.; Yoon, Soon Joon; Matula, Thomas J.; O'Donnell, Matthew; Pozzo, Lilo D.

2017-03-01

A new light and sound sensitive nanoemulsion contrast agent is presented. The agents feature a low boiling point liquid perfluorocarbon core and a broad light spectrum absorbing polypyrrole (PPy) polymer shell. The PPy coated nanoemulsions can reversibly convert from liquid to gas phase upon cavitation of the liquid perfluorocarbon core. Cavitation can be initiated using a sufficiently high intensity acoustic pulse or from heat generation due to light absorption from a laser pulse. The emulsions can be made between 150 and 350 nm in diameter and PPy has a broad optical absorption covering both the visible spectrum and extending into the near-infrared spectrum (peak absorption 1053 nm). The size, structure, and optical absorption properties of the PPy coated nanoemulsions were characterized and compared to PPy nanoparticles (no liquid core) using dynamic light scattering, ultraviolet-visible spectrophotometry, transmission electron microscopy, and small angle X-ray scattering. The cavitation threshold and signal intensity were measured as a function of both acoustic pressure and laser fluence. Overlapping simultaneous transmission of an acoustic and laser pulse can significantly reduce the activation energy of the contrast agents to levels lower than optical or acoustic activation alone. We also demonstrate that simultaneous light and sound cavitation of the agents can be used in a new sono-photoacoustic imaging method, which enables greater sensitivity than traditional photoacoustic imaging.

Safety of cornea and iris in ocular surgery with 355-nm lasers.

PubMed

Wang, Jenny; Chung, Jae Lim; Schuele, Georg; Vankov, Alexander; Dalal, Roopa; Wiltberger, Michael; Palanker, Daniel

2015-09-01

A recent study showed that 355-nm nanosecond lasers cut cornea with similar precision to infrared femtosecond lasers. However, use of ultraviolet wavelength requires precise assessment of ocular safety to determine the range of possible ophthalmic applications. In this study, the 355-nm nanosecond laser was evaluated for corneal and iris damage in rabbit, porcine, and human donor eyes as determined by minimum visible lesion (MVL) observation, live/dead staining of the endothelium, and apoptosis assay. Single-pulse damage to the iris was evaluated on porcine eyes using live/dead staining. In live rabbits, the cumulative median effective dose (ED50) for corneal damage was 231 J/cm2, as seen by lesion observation. Appearance of endothelial damage in live/dead staining or apoptosis occurred at higher radiant exposure of 287 J/cm2. On enucleated rabbit and porcine corneas, ED50 was 87 and 52 J/cm2, respectively, by MVL, and 241 and 160 J/cm2 for endothelial damage. In human eyes, ED50 for MVL was 110 J/cm2 and endothelial damage at 453 J/cm2. Single-pulse iris damage occurred at ED 50 of 208 mJ/cm2. These values determine the energy permitted for surgical patterns and can guide development of ophthalmic laser systems. Lower damage threshold in corneas of enucleated eyes versus live rabbits is noted for future safety evaluation.

Remote air lasing for trace detection

NASA Astrophysics Data System (ADS)

Dogariu, Arthur; Michael, James B.; Miles, Richard B.

2011-05-01

We demonstrate coherent light propagating backwards from a remotely generated high gain air laser. A short ultraviolet laser pulse tuned to a two-photon atomic oxygen electronic resonance at 226 nm simultaneously dissociates the oxygen molecules in air and excites the resulting atomic oxygen fragments. Due to the focal depth of the pumping laser, a millimeter long region of high gain is created in air for the atomic oxygen stimulated emission at 845nm. We demonstrate that the gain in excess of 60 cm-1 is responsible for both forward and backwards emission of a strong, collimated, coherent laser beam. We present evidence for coherent emission and characterize the backscattered laser beam while varying the pumping conditions. The optical gain and directional emission allows for six orders of magnitude enhancement for the backscattered emission when compared with the fluorescence emission collected into the same solid angle. . This opens new opportunities for the remote detection capabilities of trace species, and provides much greater range for the detection of optical molecular and atomic features from a distant target.

Near-ultraviolet removal rates for subgingival dental calculus at different irradiation angles.

PubMed

Schoenly, Joshua E; Seka, Wolf D; Rechmann, Peter

2011-07-01

The laser ablation rate of subgingival dental calculus irradiated at a 400-nm-wavelength, 7.4-mJ pulse energy, and 85- and 20-deg irradiation angles is measured using laser triangulation. Three-dimensional images taken before and after irradiation create a removal map with 6-μm axial resolution. Fifteen human teeth with subgingival calculus are irradiated in vitro under a cooling water spray with an ∼300-μm-diam, tenth-order super-gaussian beam. The average subgingival calculus removal rates for irradiation at 85 and 20 deg are 11.1±3.6 and 11.5±5.9 μm∕pulse, respectively, for depth removal and 4.5±1.7×10(5) and 4.8±2.3×10(5) μm(3)∕pulse, respectively, for volume removal. The ablation rate is constant at each irradiation site but varies between sites because of the large differences in the physical and optical properties of calculus. Comparison of the average depth- and volume-removal rates does not reveal any dependence on the irradiation angle and is likely due to the surface topology of subgingival calculus samples that overshadows any expected angular dependence.

Near-ultraviolet removal rates for subgingival dental calculus at different irradiation angles

NASA Astrophysics Data System (ADS)

Schoenly, Joshua E.; Seka, Wolf D.; Rechmann, Peter

2011-07-01

The laser ablation rate of subgingival dental calculus irradiated at a 400-nm-wavelength, 7.4-mJ pulse energy, and 85- and 20-deg irradiation angles is measured using laser triangulation. Three-dimensional images taken before and after irradiation create a removal map with 6-μm axial resolution. Fifteen human teeth with subgingival calculus are irradiated in vitro under a cooling water spray with an ~300-μm-diam, tenth-order super-Gaussian beam. The average subgingival calculus removal rates for irradiation at 85 and 20 deg are 11.1+/-3.6 and 11.5+/-5.9 μm/pulse, respectively, for depth removal and 4.5+/-1.7×105 and 4.8+/-2.3×105 μm3/pulse, respectively, for volume removal. The ablation rate is constant at each irradiation site but varies between sites because of the large differences in the physical and optical properties of calculus. Comparison of the average depth- and volume-removal rates does not reveal any dependence on the irradiation angle and is likely due to the surface topology of subgingival calculus samples that overshadows any expected angular dependence.

Dielectric breakdown induced by picosecond laser pulses

NASA Technical Reports Server (NTRS)

Smith, W. L.; Bechtel, J. H.; Bloembergen, N.

1976-01-01

The damage thresholds of transparent optical materials were investigated. Single picosecond pulses at 1.06 microns, 0.53 microns and 0.35 microns were obtained from a mode locked Nd-YAG oscillator-amplifier-frequency multiplier system. The pulses were Gaussian in space and time and permitted the determination of breakdown thresholds with a reproducibility of 15%. It was shown that the breakdown thresholds are characteristic of the bulk material, which included nine alkali halides, five different laser host materials, KDP, quartz, sapphire and calcium fluoride. The extension of the damage data to the ultraviolet is significant, because some indication was obtained that two- and three-photon absorption processes begin to play a role in determining the threshold. Throughout the visible region of the spectrum the threshold is still an increasing function of frequency, indicating that avalanche ionization is the dominant factor in determining the breakdown threshold. This was confirmed by a detailed study of the damage morphology with a high resolution microscope just above the threshold. The influence of self focusing is discussed, and evidence for beam distortion below the power threshold for complete self focusing is presented, confirming the theory of Marburger.

Linear operating region in the ozone dial photon counting system

NASA Technical Reports Server (NTRS)

Andrawis, Madeleine

1995-01-01

Ozone is a relatively unstable molecule found in Earth's atmosphere. An ozone molecule is made up of three atoms of oxygen. Depending on where ozone resides, it can protect or harm life on Earth. High in the atmosphere, about 15 miles up, ozone acts as a shield to protect Earth's surface from the sun's harmful ultraviolet radiation. Without this shield, we would be more susceptible to skin cancer, cataracts, and impaired immune systems. Closer to Earth, in the air we breathe, ozone is a harmful pollutant that causes damage to lung tissue and plants. Since the early 1980's, airborne lidar systems have been used for making measurements of ozone. The differential absorption lidar (DIAL) technique is used in the remote measurement of O3. This system allows the O3 to be measured as function of the range in the atmosphere. Two frequency-doubled Nd:YAG lasers are used to pump tunable dye lasers. The lasers are operating at 289 nm for the DIAL on-line wavelength of O3, and the other one is operated at 300 nm for the off-line wavelength. The DIAL wavelengths are produced in sequential laser pulses with a time separation of 300 micro s. The backscattered laser energy is collected by telescopes and measured using photon counting systems. The photon counting system measures the light signal by making use of the photon nature of light. The output pulse from the Photo-Multiplier Tube (PE), caused by a photon striking the PMT photo-cathode, is amplified and passed to a pulse height discriminator. The peak value of the pulse is compared to a reference voltage (discrimination level). If the pulse amplitude exceeds the discrimination level, the discriminator generates a standard pulse which is counted by the digital counter. Non-linearity in the system is caused by the overlapping of pulses and the finite response time of the electronics. At low count rates one expects the system to register one event for each output pulse from the PMT corresponding to a photon incident upon the photocathode, however, at higher rates the limitations of the discrimination/counting system will cause the observed count rate to be non-linear with respect to the true count rate. Depending on the pulse height distribution and the discriminator level, the overlapping of pulses (pulse pile-up) can cause count loss or even an additional apparent count gain as the signal levels increase. Characterization of the system, including the pulse height distribution, the signal to noise ratio, and the effect of the discriminator threshold level, is critical in maximizing the linear operating region of the system, thus greatly increasing the useful dynamic range of the system.

Steering attosecond electron wave packets with light.

PubMed

Kienberger, R; Hentschel, M; Uiberacker, M; Spielmann, Ch; Kitzler, M; Scrinzi, A; Wieland, M; Westerwalbesloh, Th; Kleineberg, U; Heinzmann, U; Drescher, M; Krausz, F

2002-08-16

Photoelectrons excited by extreme ultraviolet or x-ray photons in the presence of a strong laser field generally suffer a spread of their energies due to the absorption and emission of laser photons. We demonstrate that if the emitted electron wave packet is temporally confined to a small fraction of the oscillation period of the interacting light wave, its energy spectrum can be up- or downshifted by many times the laser photon energy without substantial broadening. The light wave can accelerate or decelerate the electron's drift velocity, i.e., steer the electron wave packet like a classical particle. This capability strictly relies on a sub-femtosecond duration of the ionizing x-ray pulse and on its timing to the phase of the light wave with a similar accuracy, offering a simple and potentially single-shot diagnostic tool for attosecond pump-probe spectroscopy.

[The spectra of a laser-produced plasma source with CO2, O2 and CF4 liquid aerosol spray target].

PubMed

Ni, Qi-Liang; Chen, Bo

2008-11-01

A laser-produced plasma (LPP) source with liquid aerosol spray target and nanosecond laser was developed, based on both soft X-ray radiation metrology and extreme ultraviolet projection lithography (EUVL). The LPP source is composed of a stainless steel solenoid valve whose temperature can be continuously controlled, a Nd : YAG laser with pulse width, working wavelength and pulse energy being 7 ns, 1.064 microm and 1J respectively, and a pulse generator which can synchronously control the valve and the laser. A standard General Valve Corporation series 99 stainless steel solenoid valve with copper gasket seals and a Kel-F poppet are used in order to minimize leakage and poppet deformation during high-pressure cryogenic operation. A close fitting copper cooling jacket surrounds the valve body. The jacket clamps a copper coolant carrying tube 3 mm in diameter, which is fed by an automatically pressurized liquid nitrogen-filled dewar. The valve temperature can be controlled between 77 and 473 K. For sufficiently high backing pressure and low temperature, the valve reservoir gas can undergo a gas-to-liquid phase transition. Upon valve pulsing, the liquid is ejected into a vacuum and breaks up into droplets, which is called liquid aerosol spray target. For the above-mentioned LPP source, firstly, by the use of Cowan program on the basis of non-relativistic quantum mechanics, the authors computed the radiative transition wavelengths and probabilities in soft X-ray region for O4+, O5+, O6+, O7+, F5+, F6+ and F7+ ions which were correspondingly produced from the interaction of the 10(11)-10(12) W x cm(-2) power laser with liquid O2, CO2 and CF4 aerosol spray targets. Secondly, the authors measured the spectra of liquid O2, CO2 and CF4 aerosol spray target LPP sources in the 6-20 nm band for the 8 x 10(11) W x cm(-2) laser irradiance. The measured results were compared with the Cowan calculated results ones, and the radiative transition wavelength and probability for the measured spectral lines were obtained.

A broadband proton backlighting platform to probe shock propagation in low-density systems

DOE PAGES

Sio, H.; Hua, R.; Ping, Y.; ...

2017-01-17

A proton backlighting platform has been developed for the study of strong shock propagation in low-density systems in planar geometry. Electric fields at the converging shock front in inertial confinement fusion implosions have been previously observed, demonstrating the presence of—and the need to understand—strong electric fields not modeled in standard radiation-hydrodynamic simulations. In this planar configuration, long-pulse ultraviolet lasers are used to drive a strong shock into a gas-cell target, while a short-pulse proton backlighter side-on radiographs the shock propagation. Finally, the capabilities of the platform are presented here. Future experiments will vary shock strength and gas fill, to probemore » shock conditions at different Z and T e.« less

High-order harmonic generation from highly excited states in acetylene

NASA Astrophysics Data System (ADS)

Mulholland, Peter; Dundas, Daniel

2018-04-01

High-order harmonic generation (HHG) from aligned acetylene molecules interacting with mid infra-red (IR), linearly polarized laser pulses is studied theoretically using a mixed quantum-classical approach in which the electrons are described using time-dependent density-functional theory while the ions are treated classically. We find that for molecules aligned perpendicular to the laser polarization axis, HHG arises from the highest-occupied molecular orbital (HOMO), while for molecules aligned along the laser polarization axis, HHG is dominated by the HOMO-1. In the parallel orientation we observe a double plateau with an inner plateau that is produced by ionization from and recombination back to an autoionizing state. Two pieces of evidence support this idea. First, by choosing a suitably tuned vacuum ultraviolet pump pulse that directly excites the autoionizing state we observe a dramatic enhancement of all harmonics in the inner plateau. Second, in certain circumstances, the position of the inner plateau cutoff does not agree with the classical three-step model. We show that this discrepancy can be understood in terms of a minimum in the dipole recombination matrix element from the continuum to the autoionizing state.

Transient lateral photovoltaic effect in synthetic single crystal diamond

NASA Astrophysics Data System (ADS)

Prestopino, G.; Marinelli, M.; Milani, E.; Verona, C.; Verona-Rinati, G.

2017-10-01

A transient lateral photovoltaic effect (LPE) is reported for a metal-semiconductor structure of synthetic single crystal diamond (SCD). A SCD Schottky photodiode was specifically designed to measure a LPE under collimated irradiation from a tunable pulsed laser. A transient lateral photovoltage parallel to the Schottky junction was indeed detected. LPE on the p-type doped SCD side showed a non-linearity of 2% and a fast response time, with a rise time of 2 μs and a decay time of 12 μs. The position sensitivity (up to 30 mV/mm at a laser wavelength of 220 nm and a pulse energy density of 2.9 μJ/mm2) was measured as a function of laser wavelength, and an ultraviolet (UV)-to-visible contrast ratio of about four orders of magnitude with a sharp cutoff at 225 nm was observed. Our results demonstrate that a large LPE at UV wavelengths is achievable in synthetic single crystal diamond, potentially opening opportunities for the study and application of LPE in diamond and for the fabrication of high performance visible blind UV position sensitive detectors with high sensitivity and microsecond scale response time.

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

Oloff, L.-P., E-mail: oloff@physik.uni-kiel.de; Hanff, K.; Stange, A.

With the advent of ultrashort-pulsed extreme ultraviolet sources, such as free-electron lasers or high-harmonic-generation (HHG) sources, a new research field for photoelectron spectroscopy has opened up in terms of femtosecond time-resolved pump-probe experiments. The impact of the high peak brilliance of these novel sources on photoemission spectra, so-called vacuum space-charge effects caused by the Coulomb interaction among the photoemitted probe electrons, has been studied extensively. However, possible distortions of the energy and momentum distributions of the probe photoelectrons caused by the low photon energy pump pulse due to the nonlinear emission of electrons have not been studied in detail yet.more » Here, we systematically investigate these pump laser-induced space-charge effects in a HHG-based experiment for the test case of highly oriented pyrolytic graphite. Specifically, we determine how the key parameters of the pump pulse—the excitation density, wavelength, spot size, and emitted electron energy distribution—affect the measured time-dependent energy and momentum distributions of the probe photoelectrons. The results are well reproduced by a simple mean-field model, which could open a path for the correction of pump laser-induced space-charge effects and thus toward probing ultrafast electron dynamics in strongly excited materials.« less

Selective ablation of sub- and supragingival calculus with a frequency-doubled Alexandrite laser

NASA Astrophysics Data System (ADS)

Rechmann, Peter; Hennig, Thomas

1995-05-01

In a preceding trial the absorption characteristics of subgingival calculus were calculated using fluorescence emission spectroscopy (excitation laser: N2-laser, wavelength 337 nm, pulse duration 4 ns). Subgingival calculus seems to contain chromophores absorbing in the ultraviolet spectral region up to 420 nm. The aim of the actual study was the ablation of sub- and supragingival calculus using a frequency doubled Alexandrite-laser (wavelength 377 nm, pulse duration 100 ns, repetition rate 110 Hz). Extracted human teeth presenting sub- and supragingival calculus were irradiated perpendicular to their axis with a laser fluence of 1 Jcm-2. Using a standard application protocol calculus was irradiated at the enamel surface, at the junction between enamel and root, and at the root surface (located on dentin or on cementum). During the irradiation procedure an effective water cooling-system was engaged. For light microscopical investigations undecalcified histological sections were prepared after treatment. The histological sections revealed that a selective and total removal of calculus is possible at all locations without ablation of healthy enamel, dentin or cementum. Even low fluences provide us with a high effectiveness for the ablation of calculus. Thus, based on different absorption characteristics and ablation thresholds, engaging a frequency doubled Alexandrite-laser a fast and, even more, a selective ablation of sub- and supragingival calculus is possible without adverse side effects to the surrounding tissues. Even more, microbial dental plaque can be perfectly removed.

Critical dimension control using ultrashort laser for improving wafer critical dimension uniformity

NASA Astrophysics Data System (ADS)

Avizemer, Dan; Sharoni, Ofir; Oshemkov, Sergey; Cohen, Avi; Dayan, Asaf; Khurana, Ranjan; Kewley, Dave

2015-07-01

Requirements for control of critical dimension (CD) become more demanding as the integrated circuit (IC) feature size specifications become tighter and tighter. Critical dimension control, also known as CDC, is a well-known laser-based process in the IC industry that has proven to be robust, repeatable, and efficient in adjusting wafer CD uniformity (CDU) [Proc. SPIE 6152, 615225 (2006)]. The process involves locally and selectively attenuating the deep ultraviolet light which goes through the photomask to the wafer. The input data for the CDC process in the wafer fab is typically taken from wafer CDU data, which is measured by metrology tools such as wafer-critical dimension-scanning electron microscopy (CD-SEM), wafer optical scatterometry, or wafer level CD (WLCD). The CD correction process uses the CDU data in order to create an attenuation correction contour, which is later applied by the in-situ ultrashort laser system of the CDC to locally change the transmission of the photomask. The ultrashort pulsed laser system creates small, partially scattered, Shade-In-Elements (also known as pixels) by focusing the laser beam inside the quartz bulk of the photomask. This results in the formation of a localized, intravolume, quartz modified area, which has a different refractive index than the quartz bulk itself. The CDC process flow for improving wafer CDU in a wafer fab with detailed explanations of the shading elements formation inside the quartz by the ultrashort pulsed laser is reviewed.

Design Considerations For A Clinical XeC1 Excimer Laser Angioplasty System

NASA Astrophysics Data System (ADS)

Laudenslager, James B.; Goldenberg, Tsvi; Naghieh, Harry R.; Pham, Andrew A.; Narciso, Hugh L.; Tranis, Art; Pacala, Thomas J.

1989-09-01

Laser ablation and removal of intravascular plaque has long been a goal of physicians and physicists as an alternative treatment for coronary and peripheral artery disease. Early application of cw free light beam visible and infrared lasers such as argon ion or Nd:YAG lasers for this application were plagued by thermal side effects of the ablation process. Specifically, imprecise control of the boundary tissue injury produced by the deep penetration depth of the laser beam gave rise to early reclosure of the vessel due to the thermal nature of the ablation process. Pulsed ultraviolet laser free beam ablation of atherosclerotic plaque, however, does not produce thermal effects, cuts tissue precisely leaving a smooth wall and can ablate hard calcific lesions. We have chosen to develop a XeC1 excimer laser-fiberoptic delivery system for the clinical application of laser angioplasty based on achieving the desired therapeutic results for a laser revascularization procedure. Four major engineering design issues must be considered in order to produce a successful clinical laser angioplasty product. These engineering issues are: 1) Functional clinical engineering, 2) Regulatory design issues, 3) Hospital facility and user requirements, and 4) Economic issues for the manufacturer, the hospital and the patient.

Odd harmonics-enhanced supercontinuum in bulk solid-state dielectric medium.

PubMed

Garejev, N; Jukna, V; Tamošauskas, G; Veličkė, M; Šuminas, R; Couairon, A; Dubietis, A

2016-07-25

We report on generation of ultrabroadband, more than 4 octave spanning supercontinuum in thin CaF₂ crystal, as pumped by intense mid-infrared laser pulses with central wavelength of 2.4 μm. The supercontinuum spectrum covers wavelength range from the ultraviolet to the mid-infrared and its short wavelength side is strongly enhanced by cascaded generation of third, fifth and seventh harmonics. Our results capture the transition from Kerr-dominated to plasma-dominated filamentation regime and uncover that in the latter the spectral superbroadening originates from dramatic plasma-induced compression of the driving pulse, which in turn induces broadening of the harmonics spectra due to cross-phase modulation effects. The experimental measurements are backed up by the numerical simulations based on a nonparaxial unidirectional propagation equation for the electric field of the pulse, which accounts for the cubic nonlinearity-induced effects, and which reproduce the experimental data in great detail.

Attosecond Streaking in the Water Window: A New Regime of Attosecond Pulse Characterization

NASA Astrophysics Data System (ADS)

Cousin, Seth L.; Di Palo, Nicola; Buades, Bárbara; Teichmann, Stephan M.; Reduzzi, M.; Devetta, M.; Kheifets, A.; Sansone, G.; Biegert, Jens

2017-10-01

We report on the first streaking measurement of water-window attosecond pulses generated via high-harmonic generation, driven by sub-2-cycle, carrier-to-envelope-phase-stable, 1850-nm laser pulses. Both the central photon energy and the energy bandwidth far exceed what has been demonstrated thus far, warranting the investigation of the attosecond streaking technique for the soft-x-ray regime and the limits of the frogcrab retrieval algorithm under such conditions. We also discuss the problem of attochirp compensation and issues regarding much lower photoionization cross sections compared with the extreme ultraviolet in addition to the fact that several shells of target gases are accessed simultaneously. Based on our investigation, we caution that the vastly different conditions in the soft-x-ray regime warrant a diligent examination of the fidelity of the measurement and the retrieval procedure.

A simple sub-nanosecond ultraviolet light pulse generator with high repetition rate and peak power.

PubMed

Binh, P H; Trong, V D; Renucci, P; Marie, X

2013-08-01

We present a simple ultraviolet sub-nanosecond pulse generator using commercial ultraviolet light-emitting diodes with peak emission wavelengths of 290 nm, 318 nm, 338 nm, and 405 nm. The generator is based on step recovery diode, short-circuited transmission line, and current-shaping circuit. The narrowest pulses achieved have 630 ps full width at half maximum at repetition rate of 80 MHz. Optical pulse power in the range of several hundreds of microwatts depends on the applied bias voltage. The bias voltage dependences of the output optical pulse width and peak power are analysed and discussed. Compared to commercial UV sub-nanosecond generators, the proposed generator can produce much higher pulse repetition rate and peak power.

Ocular injuries from laser accidents

NASA Astrophysics Data System (ADS)

Sliney, David H.

1996-04-01

Ocular injuries resulting from exposure to laser beams are relatively uncommon since there is normally a low probability of a relatively small-diameter laser beam entering the pupil of an eye. This has been the accident experience to date with lasers used in the research laboratory and in industry. A review of the accident data suggests that at least one type of laser is responsible for the majority of accidental injuries that result in a visual loss in the exposed eye. This is the q-switched neodymium:YAG laser. Although a continuous-wave laser causes a thermal coagulation of tissue, a q-switched laser having a pulse of only nanoseconds duration disrupts tissue. A visible or near-infrared laser can be focused on the retina, resulting in a vitreous hemorrhage. Examples of laser ocular injuries will be presented. Despite macular injuries and an initially serious visual loss, the vision of many patients recovers surprisingly well. Others may have severe vision loss. Corneal injuries resulting from exposure to reflected laser energy in the far-infrared account for surprisingly few reported laser accidents. The explanation for this accident statistic is not really clear. However, with the increasing use of lasers operating at many new wavelengths in the ultraviolet, visible and infrared, the ophthalmologist may see more accidental injuries from lasers.

Contributions to process monitoring by laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Rusak, David Alexander

1998-12-01

When a pulsed laser of sufficient energy and pulse duration is brought to a focus, multi-photon ionization creates free electrons in the focal volume. These electrons are accelerated in a process known as inverse Bremsstrahlung and cause collisional ionization of species in the focal volume. More charge carriers are produced and the process continues for the duration of the laser pulse. The manifestation of this process is a visible spark or plasma which typically lasts for tens of microseconds. This laser-induced plasma can serve as a source in an atomic emission experiment. Because the composition of the plasma is determined in large part by the environment in which it forms, elements in the laser target can be determined spectroscopically. The goal of a laser-induced breakdown spectroscopy (LIBS) experiment is to establish a relationship between the concentration of an element of interest in the target and the intensity of light emitted from the laser-induced plasma at a wavelength characteristic of that element. Because LIBS requires only optical access to the sample and can perform elemental determinations in solids, liquids, or gases with little sample preparation, there is interest in using it as an on-line technique for process monitoring in a number of industrial applications. However, before the technique becomes useful in industrial applications, many issues regarding instrumentation and data analysis need to be addressed in the lab. The first two chapters of this dissertation provide, respectively, the basics of the atomic emission experiment and a background of laser-induced breakdown spectroscopy. The next two chapters examine the effect of target water content on the laser-induced plasma and the use of LIBS for analysis of aqueous samples. Chapter 5 describes construction of a fiber optic LIBS probe and its use to study temporal electron number density evolution in plasmas formed on different metals. Chapter 6 is a study of excitation, vibrational, and rotational temperatures in plasmas formed by ultraviolet and infrared laser beams. The last chapter is a brief assessment of classification software for analysis of LIBS data and a discussion of future work.

Examination of Laser Microprobe Vacuum Ultraviolet Ionization Mass Spectrometry with Application to Mapping Mars Returned Samples

NASA Astrophysics Data System (ADS)

Burton, A. S.; Berger, E. L.; Locke, D. R.; Lewis, E. K.; Moore, J. F.

2018-04-01

Laser microprobe of surfaces utilizing a two laser setup whereby the desorption laser threshold is lowered below ionization, and the resulting neutral plume is examined using 157nm Vacuum Ultraviolet laser light for mass spec surface mapping.

Direct measurement of light waves.

PubMed

Goulielmakis, E; Uiberacker, M; Kienberger, R; Baltuska, A; Yakovlev, V; Scrinzi, A; Westerwalbesloh, Th; Kleineberg, U; Heinzmann, U; Drescher, M; Krausz, F

2004-08-27

The electromagnetic field of visible light performs approximately 10(15) oscillations per second. Although many instruments are sensitive to the amplitude and frequency (or wavelength) of these oscillations, they cannot access the light field itself. We directly observed how the field built up and disappeared in a short, few-cycle pulse of visible laser light by probing the variation of the field strength with a 250-attosecond electron burst. Our apparatus allows complete characterization of few-cycle waves of visible, ultraviolet, and/or infrared light, thereby providing the possibility for controlled and reproducible synthesis of ultrabroadband light waveforms.

Harmonium: A pulse preserving source of monochromatic extreme ultraviolet (30-110 eV) radiation for ultrafast photoelectron spectroscopy of liquids.

PubMed

Ojeda, J; Arrell, C A; Grilj, J; Frassetto, F; Mewes, L; Zhang, H; van Mourik, F; Poletto, L; Chergui, M

2016-03-01

A tuneable repetition rate extreme ultraviolet source (Harmonium) for time resolved photoelectron spectroscopy of liquids is presented. High harmonic generation produces 30-110 eV photons, with fluxes ranging from ∼2 × 10(11) photons/s at 36 eV to ∼2 × 10(8) photons/s at 100 eV. Four different gratings in a time-preserving grating monochromator provide either high energy resolution (0.2 eV) or high temporal resolution (40 fs) between 30 and 110 eV. Laser assisted photoemission was used to measure the temporal response of the system. Vibrational progressions in gas phase water were measured demonstrating the ∼0.2 eV energy resolution.

Optoelectrical Properties of a Heterojunction with Amorphous InGaZnO Film on n-Silicon Substrate

NASA Astrophysics Data System (ADS)

Jiang, D. L.; Ma, X. Z.; Li, L.; Xu, Z. K.

2017-10-01

An a-IGZO/ n-Si heterojunction device has been fabricated at room temperature by depositing amorphous InGaZnO (a-IGZO) film on n-type silicon substrate by plasma-assisted pulsed laser deposition and its optoelectrical properties studied in detail. The heterojunction showed distinct rectifying characteristic with rectification ratio of 1.93 × 103 at ±2 V bias and reverse leakage current density of 1.6 × 10-6 A cm-2 at -2 V bias. More interestingly, the heterojunction not only showed the characteristic of unbiased photoresponse, but could also detect either ultraviolet or ultraviolet-visible light by simply changing the polarity of the bias applied to the heterojunction. The variable photoresponse phenomenon and the charge transport mechanisms in the heterojunction are explained based on the energy band diagram of the heterojunction.

Wavelength-selective ultraviolet (Mg,Zn)O photodiodes: Tuning of parallel composition gradients with oxygen pressure

NASA Astrophysics Data System (ADS)

Zhang, Zhipeng; von Wenckstern, Holger; Lenzner, Jörg; Grundmann, Marius

2016-06-01

We report on ultraviolet photodiodes with integrated optical filter based on the wurtzite (Mg,Zn)O thin films. Tuning of the bandgap of filter and active layers was realized by employing a continuous composition spread approach relying on the ablation of a single segmented target in pulsed-laser deposition. Filter and active layers of the device were deposited on opposite sides of a sapphire substrate with nearly parallel compositional gradients. Ensure that for each sample position the bandgap of the filter layer blocking the high energy radiation is higher than that of the active layer. Different oxygen pressures during the two depositions runs. The absorption edge is tuned over 360 meV and the spectral bandwidth of photodiodes is typically 100 meV and as low as 50 meV.

Can pulsed xenon ultraviolet light systems disinfect aerobic bacteria in the absence of manual disinfection?

PubMed

Jinadatha, Chetan; Villamaria, Frank C; Ganachari-Mallappa, Nagaraja; Brown, Donna S; Liao, I-Chia; Stock, Eileen M; Copeland, Laurel A; Zeber, John E

2015-04-01

Whereas pulsed xenon-based ultraviolet light no-touch disinfection systems are being increasingly used for room disinfection after patient discharge with manual cleaning, their effectiveness in the absence of manual disinfection has not been previously evaluated. Our study indicates that pulsed xenon-based ultraviolet light systems effectively reduce aerobic bacteria in the absence of manual disinfection. These data are important for hospitals planning to adopt this technology as adjunct to routine manual disinfection. Published by Elsevier Inc.

Continuous-wave ultraviolet generation at 320 nm by intracavity frequency doubling of red-emitting Praseodymium lasers

NASA Astrophysics Data System (ADS)

Richter, A.; Pavel, N.; Heumann, E.; Huber, G.; Parisi, D.; Toncelli, A.; Tonelli, M.; Diening, A.; Seelert, W.

2006-04-01

We describe a new approach for the generation of coherent ultraviolet radiation. Continuous-wave ultraviolet light at 320 nm has been obtained by intracavity frequency doubling of red-emitting Praseodymium lasers. Lasing at the 640-nm fundamental wavelength in Pr:LiYF4 and Pr:BaY2F8 was realized by employing an optically pumped semiconductor laser at 480 nm as pump source.Using LiB3O5 as nonlinear medium, ~19 mW of ultraviolet radiation with ~9% optical efficiency with respect to absorbed power was reached for both laser crystals; the visible-to-ultraviolet conversion efficiency was 26% and 35% for Pr:LiYF4 and Pr:BaY2F8, respectively.

Focal overlap gating in velocity map imaging to achieve high signal-to-noise ratio in photo-ion pump-probe experiments

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

Shivaram, Niranjan; Champenois, Elio G.; Cryan, James P.

We demonstrate a technique in velocity map imaging (VMI) that allows spatial gating of the laser focal overlap region in time resolved pump-probe experiments. This significantly enhances signal-to-noise ratio by eliminating background signal arising outside the region of spatial overlap of pump and probe beams. This enhancement is achieved by tilting the laser beams with respect to the surface of the VMI electrodes which creates a gradient in flight time for particles born at different points along the beam. By suitably pulsing our microchannel plate detector, we can select particles born only where the laser beams overlap. Furthermore, this spatialmore » gating in velocity map imaging can benefit nearly all photo-ion pump-probe VMI experiments especially when extreme-ultraviolet light or X-rays are involved which produce large background signals on their own.« less

Ion formation mechanisms in UV-MALDI.

PubMed

Knochenmuss, Richard

2006-09-01

Matrix Assisted Laser Desorption/Ionization (MALDI) is a very widely used analytical method, but has been developed in a highly empirical manner. Deeper understanding of ionization mechanisms could help to design better methods and improve interpretation of mass spectra. This review summarizes current mechanistic thinking, with emphasis on the most common MALDI variant using ultraviolet laser excitation. A two-step framework is gaining acceptance as a useful model for many MALDI experiments. The steps are primary ionization during or shortly after the laser pulse, followed by secondary reactions in the expanding plume of desorbed material. Primary ionization in UV-MALDI remains somewhat controversial, the two main approaches are the cluster and pooling/photoionization models. Secondary events are less contentious, ion-molecule reaction thermodynamics and kinetics are often invoked, but details differ. To the extent that local thermal equilibrium is approached in the plume, the mass spectra may be straightforwardly interpreted in terms of charge transfer thermodynamics.

A method of atmospheric density measurements during Shuttle entry using UV laser Rayleigh scattering

NASA Technical Reports Server (NTRS)

Mckenzie, Robert L.

1987-01-01

A detailed study is described of the performance capabilities and the hardware requirements for a method in which ambient density is measured along the Space Shuttle flight path using on-board optical instrumentation. The technique relies on Rayleigh scattering of light from a pulsed, ultraviolet, ArF excimer laser operating at a wavelength of 193 nm. The method is shown to be capable of providing direct measurements of ambient density with an uncertainty of less than 1 percent and with a spatial resolution of 1 km, over an altitude range from 50 to 90 km. In addition, extensions of this concept are discussed that allow measurements of the shock wave location and the density profile within the shock layer. Two approaches are identified that appear to be feasible, in which the same laser system is used for the extended measurements as that required for the ambient density measurements.

Swords to plowshares: Shock wave applications to advanced lithography

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

Trucano, T.G.; Grady, D.E.; Kubiak, G.D.

1995-03-01

Extreme UltraViolet Lithography (EUVL) seeks to apply radiation in a wavelength region centered near 13 nm to produce microcircuits having features sizes 0.1 micron or less. A critical requirement for the commercial application of this technology is the development of an economical, compact source of this radiation which is suitable for lithographic applications. A good candidate is a laser-plasma source, which is generated by the interaction of an intermediate intensity laser pulse (up to 10{sup 12} W/cm{sup 2}) with a metallic target. While such a source has radiative characteristics which satisfy the needs of an EUVL source, the debris generatedmore » during the laser-target interaction strikes at the economy of the source. Here, the authors review the use of concepts and computer modeling, originally developed for hypervelocity impact analysis, to study this problem.« less

Extending the high-order-harmonic spectrum using surface plasmon polaritons

NASA Astrophysics Data System (ADS)

Ebadian, H.; Mohebbi, M.

2017-08-01

Nanoparticle assisted high-order-harmonic generation by low-intensity ultrashort laser pulses in hydrogen atomic gas is studied. This work is based on surface plasmon-polariton coupling in metal-insulator-metal structures. The necessary laser intensity is provided by enhancement of the incident laser power in the vicinity of bowtie nanoparticles installed on an insulator-metal structure. The inhomogeneous electric field distribution in the Au nanobowtie gap region is investigated. Simulations show that the insulator layer installed on the Au metal film that supports the plasmon-polariton interactions has a dramatic effect on the field enhancement factor. High-order-harmonic generation cutoffs for different arrangements are calculated and results show that the metal-insulator-metal structure is an excellent device for high-order-harmonic generation purposes. Also, the harmonic cutoff order is extended to more than 170, which is a considerable value and will be an efficient source for extreme ultraviolet radiation.

Focal overlap gating in velocity map imaging to achieve high signal-to-noise ratio in photo-ion pump-probe experiments

DOE PAGES

Shivaram, Niranjan; Champenois, Elio G.; Cryan, James P.; ...

2016-12-19

We demonstrate a technique in velocity map imaging (VMI) that allows spatial gating of the laser focal overlap region in time resolved pump-probe experiments. This significantly enhances signal-to-noise ratio by eliminating background signal arising outside the region of spatial overlap of pump and probe beams. This enhancement is achieved by tilting the laser beams with respect to the surface of the VMI electrodes which creates a gradient in flight time for particles born at different points along the beam. By suitably pulsing our microchannel plate detector, we can select particles born only where the laser beams overlap. Furthermore, this spatialmore » gating in velocity map imaging can benefit nearly all photo-ion pump-probe VMI experiments especially when extreme-ultraviolet light or X-rays are involved which produce large background signals on their own.« less

Helicity-Selective Enhancement and Polarization Control of Attosecond High Harmonic Waveforms Driven by Bichromatic Circularly Polarized Laser Fields.

PubMed

Dorney, Kevin M; Ellis, Jennifer L; Hernández-García, Carlos; Hickstein, Daniel D; Mancuso, Christopher A; Brooks, Nathan; Fan, Tingting; Fan, Guangyu; Zusin, Dmitriy; Gentry, Christian; Grychtol, Patrik; Kapteyn, Henry C; Murnane, Margaret M

2017-08-11

High harmonics driven by two-color counterrotating circularly polarized laser fields are a unique source of bright, circularly polarized, extreme ultraviolet, and soft x-ray beams, where the individual harmonics themselves are completely circularly polarized. Here, we demonstrate the ability to preferentially select either the right or left circularly polarized harmonics simply by adjusting the relative intensity ratio of the bichromatic circularly polarized driving laser field. In the frequency domain, this significantly enhances the harmonic orders that rotate in the same direction as the higher-intensity driving laser. In the time domain, this helicity-dependent enhancement corresponds to control over the polarization of the resulting attosecond waveforms. This helicity control enables the generation of circularly polarized high harmonics with a user-defined polarization of the underlying attosecond bursts. In the future, this technique should allow for the production of bright highly elliptical harmonic supercontinua as well as the generation of isolated elliptically polarized attosecond pulses.

Laser-induced surface modification of biopolymers – micro/nanostructuring and functionalization

NASA Astrophysics Data System (ADS)

Stankova, N. E.; Atanasov, P. A.; Nedyalkov, N. N.; Tatchev, Dr; Kolev, K. N.; Valova, E. I.; Armyanov, St. A.; Grochowska, K.; Śliwiński, G.; Fukata, N.; Hirsch, D.; Rauschenbach, B.

2018-03-01

The medical-grade polydimethylsiloxane (PDMS) elastomer is a widely used biomaterial in medicine for preparation of high-tech devices because of its remarkable properties. In this paper, we present experimental results on surface modification of PDMS elastomer by using ultraviolet, visible, and near-infrared ns-laser system and investigation of the chemical composition and the morphological structure inside the treated area in dependence on the processing parameters – wavelength, laser fluence and number of pulses. Remarkable chemical transformations and changes of the morphological structure were observed, resulting in the formation of a highly catalytically active surface, which was successfully functionalized via electroless Ni and Pt deposition by a sensitizing-activation free process. The results obtained are very promising in view of applying the methods of laser-induced micro- and nano-structuring and activation of biopolymers’ surface and further electroless metal plating to the preparation of, e.g., multielectrode arrays (MEAs) devices in neural and muscular surface interfacing implantable systems.

Trace element analysis of synthetic mono- and poly-crystalline CaF 2 by ultraviolet laser ablation inductively coupled plasma mass spectrometry at 266 and 193 nm

NASA Astrophysics Data System (ADS)

Koch, J.; Feldmann, I.; Hattendorf, B.; Günther, D.; Engel, U.; Jakubowski, N.; Bolshov, M.; Niemax, K.; Hergenröder, R.

2002-06-01

The analytical figures of merit for ultraviolet laser ablation-inductively coupled plasma mass spectrometry (UV-LA-ICP-MS) at 266 nm with respect to the trace element analysis of high-purity, UV-transmitting alkaline earth halides are investigated and discussed. Ablation threshold energy density values and ablation rates for mono- and poly-crystalline CaF 2 samples were determined. Furthermore, Pb-, Rb-, Sr-, Ba- and Yb-specific analysis was performed. For these purposes, a pulsed Nd:YAG laser operated at the fourth harmonic of the fundamental wavelength (λ=266 nm) and a double-focusing sector field ICP-MS detector were employed. Depending on the background noise and isotope-specific sensitivity, the detection limits typically varied from 0.7 ng/g for Sr to 7 ng/g in the case of Pb. The concentrations were determined using a glass standard reference material (SRM NIST612). In order to demonstrate the sensitivity of the arrangement described, comparative measurements by means of a commercial ablation system consisting of an ArF excimer laser (λ=193 nm) and a quadrupole-type ICP-MS (ICP-QMS) instrument were carried out. The accuracy of both analyses was in good agreement, whereas ablation at 266 nm and detection using sector-field ICP-MS led to a sensitivity that was one order of magnitude above that obtained at 193 nm with ICP-QMS.

One-shot deep-UV pulsed-laser-induced photomodification of hollow metal nanoparticles for high-density data storage on flexible substrates.

PubMed

Wan, Dehui; Chen, Hsuen-Li; Tseng, Shao-Chin; Wang, Lon A; Chen, Yung-Pin

2010-01-26

In this paper, we report a new optical data storage method: photomodification of hollow gold nanoparticle (HGN) monolayers induced by one-shot deep-ultraviolet (DUV) KrF laser recording. As far as we are aware, this study is the first to apply HGNs in optical data storage and also the first to use a recording light source for the metal nanoparticles (NPs) that is not a surface plasmon resonance (SPR) wavelength. The short wavelength of the recording DUV laser improved the optical resolution dramatically. We prepared HGNs exhibiting two absorbance regions: an SPR peak in the near-infrared (NIR) region and an intrinsic material extinction in the DUV region. A single pulse from a KrF laser heated the HGNs and transformed them from hollow structures to smaller solid spheres. This change in morphology for the HGNs was accompanied by a significant blue shift of the SPR peak. Employing this approach, we demonstrated its patterning ability with a resolving power of a half-micrometer (using a phase mask) and developed a readout method (using a blue-ray laser microscope). Moreover, we prepared large-area, uniform patterns of monolayer HGNs on various substrates (glass slides, silicon wafers, flexible plates). If this spectral recording technique could be applied onto thin flexible tapes, the recorded data density would increase significantly relative to that of current rigid discs (e.g., compact discs).

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).

Attosecond light sources in the water window

NASA Astrophysics Data System (ADS)

Ren, Xiaoming; Li, Jie; Yin, Yanchun; Zhao, Kun; Chew, Andrew; Wang, Yang; Hu, Shuyuan; Cheng, Yan; Cunningham, Eric; Wu, Yi; Chini, Michael; Chang, Zenghu

2018-02-01

As a compact and burgeoning alternative to synchrotron radiation and free-electron lasers, high harmonic generation (HHG) has proven its superiority in static and time-resolved extreme ultraviolet spectroscopy for the past two decades and has recently gained many interests and successes in generating soft x-ray emissions covering the biologically important water window spectral region. Unlike synchrotron and free-electron sources, which suffer from relatively long pulse width or large time jitter, soft x-ray sources from HHG could offer attosecond time resolution and be synchronized with their driving field to investigate time-resolved near edge absorption spectroscopy, which could reveal rich structural and dynamical information of the interrogated samples. In this paper, we review recent progresses on generating and characterizing attosecond light sources in the water window region. We show our development of an energetic, two-cycle, carrier-envelope phase stable laser source at 1.7 μm and our achievement in producing a 53 as soft x-ray pulse covering the carbon K-edge in the water window. Such source paves the ways for the next generation x-ray spectroscopy with unprecedented temporal resolution.

High-harmonic generation by field enhanced femtosecond pulses in metal-sapphire nanostructure

PubMed Central

Han, Seunghwoi; Kim, Hyunwoong; Kim, Yong Woo; Kim, Young-Jin; Kim, Seungchul; Park, In-Yong; Kim, Seung-Woo

2016-01-01

Plasmonic high-harmonic generation (HHG) drew attention as a means of producing coherent extreme ultraviolet (EUV) radiation by taking advantage of field enhancement occurring in metallic nanostructures. Here a metal-sapphire nanostructure is devised to provide a solid tip as the HHG emitter, replacing commonly used gaseous atoms. The fabricated solid tip is made of monocrystalline sapphire surrounded by a gold thin-film layer, and intended to produce EUV harmonics by the inter- and intra-band oscillations of electrons driven by the incident laser. The metal-sapphire nanostructure enhances the incident laser field by means of surface plasmon polaritons, triggering HHG directly from moderate femtosecond pulses of ∼0.1 TW cm−2 intensities. The measured EUV spectra exhibit odd-order harmonics up to ∼60 nm wavelengths without the plasma atomic lines typically seen when using gaseous atoms as the HHG emitter. This experimental outcome confirms that the plasmonic HHG approach is a promising way to realize coherent EUV sources for nano-scale near-field applications in spectroscopy, microscopy, lithography and atto-second physics. PMID:27721374

Vis-Near-Infrared Photodetectors Based on Methyl Ammonium Lead Iodide Thin Films by Pulsed Laser Deposition

NASA Astrophysics Data System (ADS)

Patel, Nagabhushan; Dias, Sandra; Krupanidhi, S. B.

2018-04-01

Organic-inorganic hybrid perovskite materials are considered as promising candidates for emerging thin-film photodetectors. In this work, we discuss the application of the CH3NH3PbI3 thin films by pulsed laser deposition for photodetection applications. With this method, we obtained good perovskite film coverage on fluorine-doped tin oxide-coated substrates and observed wel- developed grains. The films showed no sign of degradation over several months of testing. We investigated the surface morphology and surface roughness of the films by field emission scanning electron microscopy and atomic force microscopy. The optical response of the films was studied using ultraviolet-visible and photoluminescence spectroscopy. We carried out a study on the solar and infrared photodetection of CH3NH3PbI3 thin films. The values of the responsivity, sensitivity, external quantum efficiency and specific detectivity under 1 sun illumination and 0.7 V bias were 105.4 A/W, 1.9, 2.38 × 104% and 1.5 × 1012 Jones, respectively.

Live cell isolation by laser microdissection with gravity transfer

NASA Astrophysics Data System (ADS)

Podgorny, Oleg V.

2013-05-01

Laser microdissection by pulsing ultraviolet laser allows the isolation and recultivation of live cells based on morphological features or/and fluorescent labelling from adherent cell cultures. Previous investigations described only the use of the laser microdissection and pressure catapulting (LMPC) for live cell isolation. But LMPC requires complex manipulations and some skill. Furthermore, single-cell cloning using laser microdissection has not yet been demonstrated. The first evidence of successful application of laser microdissection with gravity transfer (LMDGT) for capturing and recultivation of live cells is presented. A new strategy for LMDGT is presented because of the failure to reproduce the manufacturer's protocol. Using the new strategy, successful capturing and recultivation of circle-shaped samples from confluent monolayer of HeLa cells was demonstrated. It was found that LMDGT is easier than LMPC because it doesn't require personal participation of investigator in transferring of isolated samples to final culture dishes. Moreover, for the first time, the generation of clonal colonies from single live cells isolated by laser microdissection was demonstrated. Data obtained in this study confirm that LMDGT is a reliable and high-yield method allowing isolation and expansion of both cell clusters and single cells from adherent cell cultures.

Non-equilibrium modeling of UV laser induced plasma on a copper target in the presence of Cu{sup 2+}

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

Ait Oumeziane, Amina, E-mail: a.aitoumeziane@gmail.com; Liani, Bachir; Parisse, Jean-Denis

2016-03-15

This work is a contribution to the understanding of UV laser ablation of a copper sample in the presence of Cu{sup 2+} species as well as electronic non-equilibrium in the laser induced plasma. This particular study extends a previous paper and develops a 1D hydrodynamic model to describe the behavior of the laser induced plume, including the thermal non-equilibrium between electrons and heavy particles. Incorporating the formation of doubly charged ions (Cu{sup 2+}) in such an approach has not been considered previously. We evaluate the effect of the presence of doubly ionized species on the characteristics of the plume, i.e.,more » temperature, pressure, and expansion velocity, and on the material itself by evaluating the ablation depth and plasma shielding effects. This study evaluates the effects of the doubly charged species using a non-equilibrium hydrodynamic approach which comprises a contribution to the understanding of the governing processes of the interaction of ultraviolet nanosecond laser pulses with metals and the parameter optimization depending on the intended application.« less

Hidden Charge States in Soft-X-Ray Laser-Produced Nanoplasmas Revealed by Fluorescence Spectroscopy

NASA Astrophysics Data System (ADS)

Schroedter, L.; Müller, M.; Kickermann, A.; Przystawik, A.; Toleikis, S.; Adolph, M.; Flückiger, L.; Gorkhover, T.; Nösel, L.; Krikunova, M.; Oelze, T.; Ovcharenko, Y.; Rupp, D.; Sauppe, M.; Wolter, D.; Schorb, S.; Bostedt, C.; Möller, T.; Laarmann, T.

2014-05-01

Highly charged ions are formed in the center of composite clusters by strong free-electron laser pulses and they emit fluorescence on a femtosecond time scale before competing recombination leads to neutralization of the nanoplasma core. In contrast to mass spectrometry that detects remnants of the interaction, fluorescence in the extreme ultraviolet spectral range provides fingerprints of transient states of high energy density matter. Spectra from clusters consisting of a xenon core and a surrounding argon shell show that a small fraction of the fluorescence signal comes from multiply charged xenon ions in the cluster core. Initially, these ions are as highly charged as the ions in the outer shells of pure xenon clusters with charge states up to at least 11+.

A method of atmospheric density measurements during space shuttle entry using ultraviolet-laser Rayleigh scattering

NASA Technical Reports Server (NTRS)

Mckenzie, Robert L.

1988-01-01

An analytical study and its experimental verification are described which show the performance capabilities and the hardware requirements of a method for measuring atmospheric density along the Space Shuttle flightpath during entry. Using onboard instrumentation, the technique relies on Rayleigh scattering of light from a pulsed ArF excimer laser operating at a wavelength of 193 nm. The method is shown to be capable of providing density measurements with an uncertainty of less than 1 percent and with a spatial resolution along the flightpath of 1 km, over an altitude range from 50 to 90 km. Experimental verification of the signal linearity and the expected signal-to-noise ratios is demonstrated in a simulation facility at conditions that duplicate the signal levels of the flight environment.

Energy driven self-organization in nanoscale metallic liquid films.

PubMed

Krishna, H; Shirato, N; Favazza, C; Kalyanaraman, R

2009-10-01

Nanometre thick metallic liquid films on inert substrates can spontaneously dewet and self-organize into complex nanomorphologies and nanostructures with well-defined length scales. Nanosecond pulses of an ultraviolet laser can capture the dewetting evolution and ensuing nanomorphologies, as well as introduce dramatic changes to dewetting length scales due to the nanoscopic nature of film heating. Here, we show theoretically that the self-organization principle, based on equating the rate of transfer of thermodynamic free energy to rate of loss in liquid flow, accurately describes the spontaneous dewetting. Experimental measurements of laser dewetting of Ag and Co liquid films on SiO(2) substrates confirm this principle. This energy transfer approach could be useful for analyzing the behavior of nanomaterials and chemical processes in which spontaneous changes are important.

Hybrid chirped pulse amplification system

DOEpatents

Barty, Christopher P.; Jovanovic, Igor

2005-03-29

A hybrid chirped pulse amplification system wherein a short-pulse oscillator generates an oscillator pulse. The oscillator pulse is stretched to produce a stretched oscillator seed pulse. A pump laser generates a pump laser pulse. The stretched oscillator seed pulse and the pump laser pulse are directed into an optical parametric amplifier producing an optical parametric amplifier output amplified signal pulse and an optical parametric amplifier output unconverted pump pulse. The optical parametric amplifier output amplified signal pulse and the optical parametric amplifier output laser pulse are directed into a laser amplifier producing a laser amplifier output pulse. The laser amplifier output pulse is compressed to produce a recompressed hybrid chirped pulse amplification pulse.

Study on high power ultraviolet laser oil detection system

NASA Astrophysics Data System (ADS)

Jin, Qi; Cui, Zihao; Bi, Zongjie; Zhang, Yanchao; Tian, Zhaoshuo; Fu, Shiyou

2018-03-01

Laser Induce Fluorescence (LIF) is a widely used new telemetry technology. It obtains information about oil spill and oil film thickness by analyzing the characteristics of stimulated fluorescence and has an important application in the field of rapid analysis of water composition. A set of LIF detection system for marine oil pollution is designed in this paper, which uses 355nm high-energy pulsed laser as the excitation light source. A high-sensitivity image intensifier is used in the detector. The upper machine sends a digital signal through a serial port to achieve nanoseconds range-gated width control for image intensifier. The target fluorescence spectrum image is displayed on the image intensifier by adjusting the delay time and the width of the pulse signal. The spectral image is coupled to CCD by lens imaging to achieve spectral display and data analysis function by computer. The system is used to detect the surface of the floating oil film in the distance of 25m to obtain the fluorescence spectra of different oil products respectively. The fluorescence spectra of oil products are obvious. The experimental results show that the system can realize high-precision long-range fluorescence detection and reflect the fluorescence characteristics of the target accurately, with broad application prospects in marine oil pollution identification and oil film thickness detection.

Ferromagnetic Mn-Implanted GaP: Microstructures vs Magnetic Properties.

PubMed

Yuan, Ye; Hübner, René; Liu, Fang; Sawicki, Maciej; Gordan, Ovidiu; Salvan, G; Zahn, D R T; Banerjee, D; Baehtz, Carsten; Helm, Manfred; Zhou, Shengqiang

2016-02-17

Ferromagnetic GaMnP layers were prepared by ion implantation and pulsed laser annealing (PLA). We present a systematic investigation on the evolution of microstructure and magnetic properties depending on the pulsed laser annealing energy. The sample microstructure was analyzed by high-resolution X-ray diffraction (HR-XRD), transmission electron microscopy (TEM), Rutherford backscattering spectrometry (RBS), ultraviolet Raman spectroscopy (UV-RS), and extended X-ray absorption fine structure (EXAFS) spectroscopy. The presence of X-ray Pendellösung fringes around GaP (004) and RBS channeling prove the epitaxial structure of the GaMnP layer annealed at the optimized laser energy density (0.40 J/cm(2)). However, a forbidden TO vibrational mode of GaP appears and increases with annealing energy, suggesting the formation of defective domains inside the layer. These domains mainly appear in the sample surface region and extend to almost the whole layer with increasing annealing energy. The reduction of the Curie temperature (TC) and of the uniaxial magnetic anisotropy gradually happens when more defects and the domains appear as increasing the annealing energy density. This fact univocally points to the decisive role of the PLA parameters on the resulting magnetic characteristics in the processed layers, which eventually determine the magnetic (or spintronics) figure of merit.

Blast-Wave Generation and Propagation in Rapidly Heated Laser-Irradiated Targets

NASA Astrophysics Data System (ADS)

Ivancic, S. T.; Stillman, C. R.; Nilson, P. M.; Solodov, A. A.; Froula, D. H.

2017-10-01

Time-resolved extreme ultraviolet (XUV) spectroscopy was used to study the creation and propagation of a >100-Mbar blast wave in a target irradiated by an intense (>1018WWcm2 cm2) laser pulse. Blast waves provide a platform to generate immense pressures in the laboratory. A temporal double flash of XUV radiation was observed when viewing the rear side of the target, which is attributed to the emergence of a blast wave following rapid heating by a fast-electron beam generated from the laser pulse. The time-history of XUV emission in the photon energy range of 50 to 200 eV was recorded with an x-ray streak camera with 7-ps temporal resolution. The heating and expansion of the target was simulated with an electron transport code coupled to 1-D radiation-hydrodynamics simulations. The temporal delay between the two flashes measured in a systematic study of target thickness and composition was found to evolve in good agreement with a Sedov-Taylor blast-wave solution. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and Department of Energy Office of Science Award Number DE-SC-0012317.

Control of the polarization of a vacuum-ultraviolet, high-gain, free-electron laser

DOE PAGES

Allaria, Enrico; Diviacco, Bruno; Callegari, Carlo; ...

2014-12-02

The two single-pass, externally seeded free-electron lasers (FELs) of the FERMI user facility are designed around Apple-II-type undulators that can operate at arbitrary polarization in the vacuum ultraviolet-to-soft x-ray spectral range. Furthermore, within each FEL tuning range, any output wavelength and polarization can be set in less than a minute of routine operations. We report the first demonstration of the full output polarization capabilities of FERMI FEL-1 in a campaign of experiments where the wavelength and nominal polarization are set to a series of representative values, and the polarization of the emitted intense pulses is thoroughly characterized by three independentmore » instruments and methods, expressly developed for the task. The measured radiation polarization is consistently >90% and is not significantly spoiled by the transport optics; differing, relative transport losses for horizontal and vertical polarization become more prominent at longer wavelengths and lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other, allow a cross-calibration of the instruments, and constitute a benchmark for user experiments.« less

Light-induced absorption and its relaxation under illumination of continuous wave ultraviolet light in Mn-doped near-stoichiometric LiNbO{sub 3}

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

Liu Youwen; Kitamura, Kenji; Takekawa, Shunji

2005-04-01

The steady-state light-induced absorption and the temporal relaxation behavior under illumination of cw ultraviolet light in Mn-doped near-stoichiometric LiNbO{sub 3} with different crystal compositions are investigated. The ultraviolet-light-induced absorption has been assigned to small polarons Nb{sub Li}{sup 4+} by measuring the absorption spectra at room temperature. The dependences of relaxation behaviors (time constant and stretching factor) of light-induced absorption on various illumination conditions (intensity, polarization) and temperature are presented, which are very different from those observed in Fe-doped LiNbO{sub 3} illuminated with highly intense light pulse, though the temporal relaxation follows the same stretched-exponential decay behavior in both cases. Themore » results are explained reasonably by using the model of distance-dependent electron transition probabilities between localized deep traps and small polarons without any additional assumptions, and discussed to tailor doped near-stoichiometric LiNbO{sub 3} crystals for two-color holographic recording with cw laser light.« less

Ultraviolet photodetectors based on ZnO sheets: The effect of sheet size on photoresponse properties

NASA Astrophysics Data System (ADS)

Ghasempour Ardakani, Abbas; Pazoki, Meysam; Mahdavi, Seyed Mohammad; Bahrampour, Ali Reza; Taghavinia, Nima

2012-05-01

In this work, ultraviolet photodetectors based on electrodeposited ZnO sheet thin films were fabricated on a glass substrate. Before electrodeposition, a thin buffer layer of ZnO was deposited on the glass by pulsed laser deposition method. This layer not only acted as a nucleation site for ZnO sheet growth, but also made it possible to use cheap glass substrate instead of conventional fluorine-doped tin oxide (FTO) substrate. Our results showed that photoresponse properties of the photodetectors strongly depend on the sheet sizes. The smaller sheets exhibited enhanced photosensitivity, shortened fall times and decreased gain compared to larger ones. We showed that photodetectors based on ZnO sheets have a faster response than ones based on polycrystalline films. It was also shown that even less response time could be obtained by using comb-like electrodes instead of two-electrode.

Reduction of B-integral accumulation in lasers

DOEpatents

Meyerhofer, David D.; Konoplev, Oleg A.

2000-01-01

A pulsed laser is provided wherein the B-integral accumulated in the laser pulse is reduced using a semiconductor wafer. A laser pulse is generated by a laser pulse source. The laser pulse passes through a semiconductor wafer that has a negative nonlinear index of refraction. Thus, the laser pulse accumulates a negative B-integral. The laser pulse is then fed into a laser amplification medium, which has a positive nonlinear index of refraction. The laser pulse may make a plurality of passes through the laser amplification medium and accumulate a positive B-integral during a positive non-linear phase change. The semiconductor and laser pulse wavelength are chosen such that the negative B-integral accumulated in the semiconductor wafer substantially cancels the positive B-integral accumulated in the laser amplification medium. There may be additional accumulation of positive B-integral if the laser pulse passes through additional optical mediums such as a lens or glass plates. Thus, the effects of self-phase modulation in the laser pulse are substantially reduced.

Efficient extreme-UV-to-extreme-UV conversion by four-wave mixing with intense near-IR pulses in highly charged ion plasmas

NASA Astrophysics Data System (ADS)

Chu, Hsu-hsin; Wang, Jyhpyng

2018-05-01

Nonlinear optics in the extreme-ultraviolet (EUV) has been limited by lack of transparent media and small conversion efficiency. To overcome this problem we explore the advantage of using multiply charged ion plasmas as the interacting media between EUV and intense near-infrared (NIR) pulses. Such media are transparent to EUV and can withstand intense NIR driving pulses without damage. We calculate the third-order nonlinear polarizabilities of Ar2 + and Ar3 + ions for EUV and NIR four-wave mixing by using the well-proven Cowan code and find that the EUV-to-EUV conversion efficiency as high as 26% can be expected for practical experimental configurations using multi-terawatt NIR lasers. Such a high efficiency is possible because the driving pulse intensity can be scaled up to several orders of magnitude higher than in conventional nonlinear media, and the group-velocity and phase mismatch are insignificant at the experimental plasma densities. This effective scheme of wave mixing can be utilized for ultrafast EUV waveform measurement and control as well as wavelength conversion.

Laser fusion pulse shape controller

DOEpatents

Siebert, Larry D.

1977-01-01

An apparatus for controlling the pulse shape, i.e., the pulse duration and intensity pattern, of a pulsed laser system, and which is particularly well adapted for controlling the pellet ignition pulse in a laser-driven fusion reaction system. The apparatus comprises a laser generator for providing an optical control pulse of the shape desired, a pulsed laser triggered by the control pulse, and a plurality of optical Kerr-effect gates serially disposed at the output of the pulsed laser and selectively triggered by the control pulse to pass only a portion of the pulsed laser output generally corresponding in shape to the control pulse.

Analytical model for atomic resonant attosecond transient absorption

NASA Astrophysics Data System (ADS)

Cariker, C.; Kjellson, T.; Lindroth, E.; Argenti, L.

2017-04-01

Recent advancements in ultrafast laser technology have made it possible to probe electron dynamics in highly excited atomic states that autoionize on a femtosecond timescale, thus giving insight into the dynamics of Auger decay and its interference with the continuum. These experiments provide a stringent test for time-resolved analytical models of autoionization. Here we present a finite-pulse, multi-photon perturbative model which is used in conjunction with ab-initio structure calculations to predict the attosecond transient absorption spectrum (ATAS) of an atom above the ionization threshold. We apply this model to compute the ATAS of argon in the vicinity of the 3s-1 4 p resonance as a function of the time delay between an extreme ultraviolet (XUV) and an infrared (IR) pulse, as well as of the angle between their polarization. We show that by modulating the parameters of the IR pulse it is possible to control the dipolar coupling between neighboring states and hence the lineshape of the 3s-1 4 p resonance. NSF Grant No. 1607588.

Time zero determination for FEL pump-probe studies based on ultrafast melting of bismuth.

PubMed

Epp, S W; Hada, M; Zhong, Y; Kumagai, Y; Motomura, K; Mizote, S; Ono, T; Owada, S; Axford, D; Bakhtiarzadeh, S; Fukuzawa, H; Hayashi, Y; Katayama, T; Marx, A; Müller-Werkmeister, H M; Owen, R L; Sherrell, D A; Tono, K; Ueda, K; Westermeier, F; Miller, R J D

2017-09-01

A common challenge for pump-probe studies of structural dynamics at X-ray free-electron lasers (XFELs) is the determination of time zero (T 0 )-the time an optical pulse (e.g., an optical laser) arrives coincidently with the probe pulse (e.g., a XFEL pulse) at the sample position. In some cases, T 0 might be extracted from the structural dynamics of the sample's observed response itself, but generally, an independent robust method is required or would be superior to the inferred determination of T 0 . In this paper, we present how the structural dynamics in ultrafast melting of bismuth can be exploited for a quickly performed, reliable and accurate determination of T 0 with a precision below 20 fs and an overall experimental accuracy of 50 fs to 150 fs (estimated). Our approach is potentially useful and applicable for fixed-target XFEL experiments, such as serial femtosecond crystallography, utilizing an optical pump pulse in the ultraviolet to near infrared spectral range and a pixelated 2D photon detector for recording crystallographic diffraction patterns in transmission geometry. In comparison to many other suitable approaches, our method is fairly independent of the pumping wavelength (UV-IR) as well as of the X-ray energy and offers a favorable signal contrast. The technique is exploitable not only for the determination of temporal characteristics of the experiment at the interaction point but also for investigating important conditions affecting experimental control such as spatial overlap and beam spot sizes.

Mid-infrared-to-mid-ultraviolet supercontinuum enhanced by third-to-fifteenth odd harmonics.

PubMed

Mitrofanov, A V; Voronin, A A; Mitryukovskiy, S I; Sidorov-Biryukov, D A; Pugžlys, A; Andriukaitis, G; Flöry, T; Stepanov, E A; Fedotov, A B; Baltuška, A; Zheltikov, A M

2015-05-01

A high-energy supercontinuum spanning 4.7 octaves, from 250 to 6500 nm, is generated using a 0.3-TW, 3.9-μm output of a mid-infrared optical parametric chirped-pulse amplifier as a driver inducing a laser filament in the air. The high-frequency wing of the supercontinuum spectrum is enhanced by odd-order optical harmonics of the mid-infrared driver. Optical harmonics up to the 15th order are observed in supercontinuum spectra as overlapping, yet well-resolved peaks broadened, as verified by numerical modeling, due to spatially nonuniform ionization-induced blue shift.

Cavity ring down spectrometry for disease diagnostics using exhaled air

NASA Astrophysics Data System (ADS)

Revalde, G.; Grundšteins, K.; Alnis, J.; Skudra, A.

2017-12-01

In this paper we report the current stage of the development of a cavity ring-down spectrometer (CRDS) system using exhaled human breath analysis for the diagnostics of different diseases like diabetes and later lung cancer. The portable CRDS system is made in ultraviolet spectral region using Nd:Yag laser 266 nm pulsed light. Calibration of the CRDS system was performed using generated samples by KinTek automated permeation tube system and self-prepared mixtures with known concentration of benzene and acetone in air. First experiments showed that the limits of detection for benzene and acetone are several tens of ppb.

Analysis of extreme ultraviolet spectra from laser produced rhenium plasmas

NASA Astrophysics Data System (ADS)

Wu, Tao; Higashiguchi, Takeshi; Li, Bowen; Suzuki, Yuhei; Arai, Goki; Dinh, Thanh-Hung; Dunne, Padraig; O'Reilly, Fergal; Sokell, Emma; Liu, Luning; O'Sullivan, Gerry

2015-08-01

Extreme ultraviolet spectra of highly-charged rhenium ions were observed in the 1-7 nm region using two Nd:YAG lasers with pulse lengths of 150 ps and 10 ns, respectively, operating at a number of laser power densities. The maximum focused peak power density was 2.6 × 1014 W cm-2 for the former and 5.5 × 1012 W cm-2 for the latter. The Cowan suite of atomic structure codes and unresolved transition array (UTA) approach were used to calculate and interpret the emission properties of the different spectra obtained. The results show that n = 4-n = 4 and n = 4-n = 5 UTAs lead to two intense quasi-continuous emission bands in the 4.3-6.3 nm and 1.5-4.3 nm spectral regions. As a result of the different ion stage distributions in the plasmas induced by ps and ns laser irradiation the 1.5-4.3 nm UTA peak moves to shorter wavelength in the ps laser produced plasma spectra. For the ns spectrum, the most populated ion stage during the lifetime of this plasma that could be identified from the n = 4-n = 5 transitions was Re23+ while for the ps plasma the presence of significantly higher stages was demonstrated. For the n = 4-n = 4 4p64dN-4p54dN+1 + 4p64dN-14f transitions, the 4d-4f transitions contribute mainly in the most intense 4.7-5.5 nm region while the 4p-4d subgroup gives rise to a weaker feature in the 4.3-4.7 nm region. A number of previously unidentified spectral features produced by n = 4-n = 5 transitions in the spectra of Re XVI to Re XXXIX are identified.

Ultraviolet and infrared laser-induced fragmentation of free (CF{sub 3}I){sub n} clusters in a molecular beam and (CF{sub 3}I){sub n} clusters inside or on the surface of large (Xe){sub m} clusters

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

Apatin, V. M.; Lokhman, V. N.; Makarov, G. N., E-mail: gmakarov@isan.troitsk.ru

The fragmentation of free homogeneous (CF{sub 3}I){sub n} clusters in a molecular beam (n ≤ 45 is the average number of molecules in the cluster) and (CF{sub 3}I){sub n} clusters inside or on the surface of large (Xe){sub m} clusters (m ≥ 100 is the average number of atoms in the cluster) by ultraviolet and infrared laser radiations has been studied. These three types of (CF{sub 3}I){sub n} clusters are shown to have different stabilities with respect to fragmentation by both ultraviolet and infrared radiations and completely different dependences of the fragmentation probability on the energy of ultraviolet and infraredmore » radiations. When exposed to ultraviolet radiation, the free (CF{sub 3}I){sub n} clusters fragment at comparatively low fluences (Φ{sub UV} ≤ 0.15 J cm{sup −2}) and the weakest energy dependence of the fragmentation probability is observed for them. A stronger energy dependence of the fragmentation probability is observed for the (CF{sub 3}I){sub n} clusters localized inside (Xe){sub m} clusters, and the strongest dependence is observed for the (CF{sub 3}I){sub n} clusters located on the surface of (Xe){sub m} clusters. When the clusters are exposed to infrared radiation, the homogeneous (CF{sub 3}I){sub n} clusters efficiently fragment at low fluences (Φ{sub IR} ≤ 25 mJ cm{sup −2}), higher fluences (Φ{sub IR} ≈ 75 mJ cm{sup −2}) are needed for the fragmentation of the (CF{sub 3}I){sub n} localized inside (Xe){sub m} clusters, and even higher fluences (Φ{sub IR} ≈ 150 mJ cm{sup −2}) are needed for the fragmentation of the (CF{sub 3}I){sub n} clusters located on the surface of (Xe){sub m} clusters. It has been established that small (CF{sub 3}I){sub n} clusters located on the surface of (Xe){sub m} clusters do not fragment up to fluences Φ{sub IR} ≈ 250 mJ cm{sup −2}. The fragmentation efficiency of (CF{sub 3}I){sub n} clusters is shown to be the same (at the same fluence) when they are excited by both pulsed (τ{sub p} ≈ 150 ns) and continuous-wave infrared laser radiations. Possible causes of such a pattern of ultraviolet and infrared laser-induced fragmentation of these clusters are discussed.« less

Studies of inactivation mechanism of non-enveloped icosahedral virus by a visible ultrashort pulsed laser

PubMed Central

2014-01-01

Background Low-power ultrashort pulsed (USP) lasers operating at wavelengths of 425 nm and near infrared region have been shown to effectively inactivate viruses such as human immunodeficiency virus (HIV), M13 bacteriophage, and murine cytomegalovirus (MCMV). It was shown previously that non-enveloped, helical viruses such as M13 bacteriophage, were inactivated by a USP laser through an impulsive stimulated Raman scattering (ISRS) process. Recently, enveloped virus like MCMV has been shown to be inactivated by a USP laser via protein aggregation induced by an ISRS process. However, the inactivation mechanism for a clinically important class of viruses – non-enveloped, icosahedral viruses remains unknown. Results and discussions We have ruled out the following four possible inactivation mechanisms for non-enveloped, icosahedral viruses, namely, (1) inactivation due to ultraviolet C (UVC) photons produced by non-linear optical process of the intense, fundamental laser beam at 425 nm; (2) inactivation caused by thermal heating generated by the direct laser absorption/heating of the virion; (3) inactivation resulting from a one-photon absorption process via chromophores such as porphyrin molecules, or indicator dyes, potentially producing reactive oxygen or other species; (4) inactivation by the USP lasers in which the extremely intense laser pulse produces shock wave-like vibrations upon impact with the viral particle. We present data which support that the inactivation mechanism for non-enveloped, icosahedral viruses is the impulsive stimulated Raman scattering process. Real-time PCR experiments show that, within the amplicon size of 273 bp tested, there is no damage on the genome of MNV-1 caused by the USP laser irradiation. Conclusion We conclude that our model non-enveloped virus, MNV-1, is inactivated by the ISRS process. These studies provide fundamental knowledge on photon-virus interactions on femtosecond time scales. From the analysis of the transmission electron microscope (TEM) images of viral particles before and after USP laser irradiation, the locations of weak structural links on the capsid of MNV-1 were revealed. This important information will greatly aid our understanding of the structure of non-enveloped, icosahedral viruses. We envision that this non-invasive, efficient viral eradication method will find applications in the disinfection of pharmaceuticals, biologicals and blood products in the near future. PMID:24495489

Roadmap on ultrafast optics

NASA Astrophysics Data System (ADS)

Reid, Derryck T.; Heyl, Christoph M.; Thomson, Robert R.; Trebino, Rick; Steinmeyer, Günter; Fielding, Helen H.; Holzwarth, Ronald; Zhang, Zhigang; Del'Haye, Pascal; Südmeyer, Thomas; Mourou, Gérard; Tajima, Toshiki; Faccio, Daniele; Harren, Frans J. M.; Cerullo, Giulio

2016-09-01

The year 2015 marked the 25th anniversary of modern ultrafast optics, since the demonstration of the first Kerr lens modelocked Ti:sapphire laser in 1990 (Spence et al 1990 Conf. on Lasers and Electro-Optics, CLEO, pp 619-20) heralded an explosion of scientific and engineering innovation. The impact of this disruptive technology extended well beyond the previous discipline boundaries of lasers, reaching into biology labs, manufacturing facilities, and even consumer healthcare and electronics. In recognition of such a milestone, this roadmap on Ultrafast Optics draws together articles from some of the key opinion leaders in the field to provide a freeze-frame of the state-of-the-art, while also attempting to forecast the technical and scientific paradigms which will define the field over the next 25 years. While no roadmap can be fully comprehensive, the thirteen articles here reflect the most exciting technical opportunities presented at the current time in Ultrafast Optics. Several articles examine the future landscape for ultrafast light sources, from practical solid-state/fiber lasers and Raman microresonators to exotic attosecond extreme ultraviolet and possibly even zeptosecond x-ray pulses. Others address the control and measurement challenges, requiring radical approaches to harness nonlinear effects such as filamentation and parametric generation, coupled with the question of how to most accurately characterise the field of ultrafast pulses simultaneously in space and time. Applications of ultrafast sources in materials processing, spectroscopy and time-resolved chemistry are also discussed, highlighting the improvements in performance possible by using lasers of higher peak power and repetition rate, or by exploiting the phase stability of emerging new frequency comb sources.

Laser system using ultra-short laser pulses

DOEpatents

Dantus, Marcos [Okemos, MI; Lozovoy, Vadim V [Okemos, MI; Comstock, Matthew [Milford, MI

2009-10-27

A laser system using ultrashort laser pulses is provided. In another aspect of the present invention, the system includes a laser, pulse shaper and detection device. A further aspect of the present invention employs a femtosecond laser and binary pulse shaping (BPS). Still another aspect of the present invention uses a laser beam pulse, a pulse shaper and a SHG crystal.

Temperature measurement using ultraviolet laser absorption of carbon dioxide behind shock waves.

PubMed

Oehlschlaeger, Matthew A; Davidson, David F; Jeffries, Jay B

2005-11-01

A diagnostic for microsecond time-resolved temperature measurements behind shock waves, using ultraviolet laser absorption of vibrationally hot carbon dioxide, is demonstrated. Continuous-wave laser radiation at 244 and 266 nm was employed to probe the spectrally smooth CO2 ultraviolet absorption, and an absorbance ratio technique was used to determine temperature. Measurements behind shock waves in both nonreacting and reacting (ignition) systems were made, and comparisons with isentropic and constant-volume calculations are reported.

Control of laser pulse waveform in longitudinally excited CO2 laser by adjustment of excitation circuit

NASA Astrophysics Data System (ADS)

Uno, Kazuyuki; Jitsuno, Takahisa

2018-05-01

In a longitudinally excited CO2 laser that had a 45 cm-long discharge tube with a 1:1:2 mixture of CO2/N2/He gas at a pressure of 3.0 kPa, we realized the generation of a short laser pulse with a spike pulse width of about 200 ns and a pulse tail length of several tens of microseconds, control of the energy ratio of the spike pulse part to the pulse tail part in the short laser pulse, the generation of a long laser pulse with a pulse width of several tens of microseconds, and control of the pulse width in the long laser pulse, by using four types of excitation circuits in which the capacitance was adjusted. In the short laser pulse, the energy ratio was in the range 1:14-1:112. In the long laser pulse, the pulse width was in the range 25.7-82.7 μs.

A double-stream Xe:He jet plasma emission in the vicinity of 6.7 nm

NASA Astrophysics Data System (ADS)

Chkhalo, N. I.; Garakhin, S. A.; Golubev, S. V.; Lopatin, A. Ya.; Nechay, A. N.; Pestov, A. E.; Salashchenko, N. N.; Toropov, M. N.; Tsybin, N. N.; Vodopyanov, A. V.; Yulin, S.

2018-05-01

We present the results of investigations of extreme ultraviolet (EUV) light emission in the range from 5 to 10 nm. The light source was a pulsed "double-stream" Xe:He gas jet target irradiated by a laser beam with a power density of ˜1011 W/cm2. The radiation spectra were measured with a Czerny-Turner monochromator with a plane diffraction grating. The conversion efficiency of the laser energy into EUV radiation caused by Xe+14…+16 ion emission in the range of 6-8 nm was measured using a calibrated power meter. The conversion efficiency of the laser radiation into EUV in the vicinity of 6.7 nm was (2.17 ± 0.13)% in a 1 nm spectral band. In the spectral band of the real optical system (0.7% for La/B multilayer mirrors) emitted into the half-space, it was (0.1 ± 0.006)%. The results of this study provide an impetus for further research on laser plasma sources for maskless EUV lithography at a wavelength of 6.7 nm.

Evaluation of pressure in a plasma produced by laser ablation of steel

NASA Astrophysics Data System (ADS)

Hermann, Jörg; Axente, Emanuel; Craciun, Valentin; Taleb, Aya; Pelascini, Frédéric

2018-05-01

We investigated the time evolution of pressure in the plume generated by laser ablation with ultraviolet nanosecond laser pulses in a near-atmospheric argon atmosphere. These conditions were previously identified to produce a plasma of properties that facilitate accurate spectroscopic diagnostics. Using steel as sample material, the present investigations benefit from the large number of reliable spectroscopic data available for iron. Recording time-resolved emission spectra with an echelle spectrometer, we were able to perform accurate measurements of electron density and temperature over a time interval from 200 ns to 12 μs. Assuming local thermodynamic equilibrium, we computed the plasma composition within the ablated vapor material and the corresponding kinetic pressure. The time evolution of plume pressure is shown to reach a minimum value below the pressure of the background gas. This indicates that the process of vapor-gas interdiffusion has a negligible influence on the plume expansion dynamics in the considered timescale. Moreover, the results promote the plasma pressure as a control parameter in calibration-free laser-induced breakdown spectroscopy.

Development of a compact laser-based single photon ionization time-of-flight mass spectrometer

NASA Astrophysics Data System (ADS)

Tonokura, Kenichi; Kanno, Nozomu; Yamamoto, Yukio; Yamada, Hiroyuki

2010-02-01

We have developed a compact, laser-based, single photon ionization time-of-flight mass spectrometer (SPI-TOF-MS) for on-line monitoring of trace organic species. To obtain the mass spectrum, we use a nearly fragmentation-free SPI technique with 10.5 eV (118 nm) vacuum ultraviolet laser pulses generated by frequency tripling of the third harmonic of an Nd:YAG laser. The instrument can be operated in a linear TOF-MS mode or a reflectron TOF-MS mode in the coaxial design. We designed ion optics to optimize detection sensitivity and mass resolution. For data acquisition, the instrument is controlled using LabVIEW control software. The total power requirement for the vacuum unit, control electronics unit, ion optics, and detection system is approximately 100 W. We achieve a detection limit of parts per billion by volume (ppbv) for on-line trace analysis of several organic compounds. A mass resolution of 800 at about 100 amu is obtained for reflectron TOF-MS mode in a 0.35 m long instrument. The application of on-line monitoring of diesel engine exhaust was demonstrated.

The national ignition facility: path to ignition in the laboratory

NASA Astrophysics Data System (ADS)

Moses, E. I.; Bonanno, R. E.; Haynam, C. A.; Kauffman, R. L.; MacGowan, B. J.; Patterson, R. W., Jr.; Sawicki, R. H.; van Wonterghem, B. M.

2007-08-01

The National Ignition Facility (NIF) is a 192-beam laser facility presently under construction at LLNL. When completed, NIF will be a 1.8-MJ, 500-TW ultraviolet laser system. Its missions are to obtain fusion ignition and to perform high energy density experiments in support of the US nuclear weapons stockpile. Four of the NIF beams have been commissioned to demonstrate laser performance and to commission the target area including target and beam alignment and laser timing. During this time, NIF demonstrated on a single-beam basis that it will meet its performance goals and demonstrated its precision and flexibility for pulse shaping, pointing, timing and beam conditioning. It also performed four important experiments for Inertial Confinement Fusion and High Energy Density Science. Presently, the project is installing production hardware to complete the project in 2009 with the goal to begin ignition experiments in 2010. An integrated plan has been developed including the NIF operations, user equipment such as diagnostics and cryogenic target capability, and experiments and calculations to meet this goal. This talk will provide NIF status, the plan to complete NIF, and the path to ignition.

Direct generation of superhydrophobic microstructures in metals by UV laser sources in the nanosecond regime

NASA Astrophysics Data System (ADS)

Ocaña, Jose L.; Jagdheesh, R.; García-Ballesteros, J. J.

2016-02-01

The current availability of new advanced fiber and DPSS lasers with characteristic pulse lengths ranging from ns to fs has provided a unique frame in which the development of laser-generated microstructures has been made possible for very diverse kinds of materials and applications. At the same time, the development of the appropriate laser-processing workstations granting the appropriate precision and repeatability of the respective laser interaction processes in line with the characteristic dimension features required in the microstructured samples has definitively consolidated laser surface microstructuring as a reference domain, nowadays, unavoidable for the design and manufacturing of current use microsystem: MEMSs, fluidic devices, advanced sensors, biomedical devices and instruments, etc., are all among the most well-known developments of the micromanufacturing technology. Completing the broad spectrum of applications developed mostly involving the generation of geometrical features on a subtrate with specific functional purposes, a relatively new, emerging class of laser-microstructuring techniques is finding an important niche of application in the generation of physically structured surfaces (particularly of metallic materials) with specific contact, friction, and wear functionalities, for whose generation the concourse of different types of laser sources is being found as an appropriate tool. In this paper, the application of laser sources with emission in the UV and at ns time regime to the surface structuration of metal surfaces (specifically Al) for the modification of their wettability properties is described as an attractive application basis for the generation of self-cleaning properties of extended functional surfaces. Flat aluminum sheets of thickness 100 μm were laser machined with ultraviolet laser pulses of 30 ns with different laser parameters to optimize the process parameters. The samples produced at the optimum conditions with respect to contact angle measurement were subjected to microstructure and chemical analysis. The wetting properties were evaluated by static contact angle measurements on the laser-patterned surface. The laser-patterned microstructures exhibited superhydrophobicity with a maximum contact angle of 180° for the droplet volumes in the range of 8-12 μl.

Classical trajectories in polar-asymmetric laser fields: Synchronous THz and XUV emission

NASA Astrophysics Data System (ADS)

Gragossian, Aram; Seletskiy, Denis V.; Sheik-Bahae, Mansoor

2016-10-01

The interaction of intense near- and mid-infrared laser pulses with rare gases has produced bursts of radiation with spectral content extending into the extreme ultraviolet and soft x-ray region of electromagnetic spectrum. On the other end of the spectrum, laser-driven gas plasmas has been shown to produce coherent sub-harmonic optical waveforms, covering from terahertz (THz) to mid- and near-infrared frequency spectral band. Both processes can be enhanced via a combination of a driving field and its second harmonic. Despite this striking similarity, only limited experimental and theoretical attempts have been made to address these two regimes simultaneously. Here we present systematic experiments and a unifying picture of these processes, based on our extension of the semi-classical three-step model. Further understanding of the generation and coherent control of time-synchronized transients with photon energies from meV to 1 keV can lead to numerous technological advances and to an intriguing possibilities of ultra-broadband investigations into complex condensed matter systems.

Experimental observation of attosecond control over relativistic electron bunches with two-colour fields

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

Yeung, M.; Rykovanov, S.; Bierbach, J.

2016-12-05

Energy coupling during relativistically intense laser–matter interactions is encoded in the attosecond motion of strongly driven electrons at the pre-formed plasma–vacuum boundary. Studying and controlling this motion can reveal details about the microscopic processes that govern a vast array of light–matter interaction phenomena, including those at the forefront of extreme laser–plasma science such as laser-driven ion acceleration, bright attosecond pulse generation and efficient energy coupling for the generation and study of warm dense matter. Here in this paper, we experimentally demonstrate that by precisely adjusting the relative phase of an additional laser beam operating at the second harmonic of themore » driving laser it is possible to control the trajectories of relativistic electron bunches formed during the interaction with a solid target at the attosecond scale. Finally, we observe significant enhancements in the resulting high-harmonic yield, suggesting potential applications for sources of ultra-bright, extreme ultraviolet attosecond radiation to be used in atomic and molecular pump–probe experiments« less

Absorption spectra of localized surface plasmon resonance observed in an inline/picoliter spectrometer cell fabricated by a near ultraviolet femtosecond laser

NASA Astrophysics Data System (ADS)

Shiraishi, Masahiko; Nishiyama, Michiko; Watanabe, Kazuhiro; Kubodera, Shoichi

2018-03-01

Absorption spectra based on localized surface plasmon resonance (LSPR) were obtained with an inline/picoliter spectrometer cell. The spectrometer cell was fabricated into an optical glass fiber by focusing a near UV (NUV) femtosecond laser pulses at a wavelength of 400 nm with an energy of 30 μJ. The laser beam was focused from two directions opposite to each other to fabricate a through-hole spectrometer cell. A diameter of the cell was approximately 3 μm, and the length was approximately 62.5 μm, which was nearly equal to the core diameter of the optical fiber. Liquid solution of gold nanoparticles (GNPs) with a diameter of 5-10 nm was injected into the spectrometer cell with its volume of 0.4 pL. The absorption peak centered at 518 nm was observed. An increase of absorption associated with the increase of the number of nanoparticles was in agreement with the numerical calculation based on the Lambert-Beer law.

An XUV/VUV free-electron laser oscillator

NASA Astrophysics Data System (ADS)

Goldstein, J. C.; Newnam, B. E.; Cooper, R. K.; Comly, J. C., Jr.

Problems regarding the extension of free-electron laser technology from the visible and near infrared region, where such devices are currently operating, to the ultraviolet have recently been extensively discussed. It was found that significant technical problems must be overcome before free-electron lasers (FELs) can be operated in the VUV (100-200 nm) and the XUV (50-100). However, the present lack of other intense and tunable sources of coherent radiation at these wavelengths together with the intrinsic properties of FELs make the development of such devices potentially very rewarding. The properties of FELs include continuous tunability in wavelength and output in the form of a train of picosecond pulses. An investigation is conducted regarding the feasibility of an operation of a FEL in the XUV/VUV regions, taking into account a theoretical model. It is found that modest improvements in electron beam and optical mirror technologies will make the design of a FEL for operation in the 50-200-nm range of optical wavelength possible.

Infrared-Vacuum Ultraviolet Pulsed Field Ionization-Photoelectron Study of C₂H₄ + Using a High-Resolution Infrared Laser

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

Xing, Xi; Reed, Beth; Bahng, Mi-Kyung

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The infrared (IR)-vacuum ultraviolet (VUV)-pulsed field ionization-photoelectron (IR-VUV-PFI-PE) spectrum for C₂H₄(X 1A g, V 11 = 1, N' Ka' Kc'=3₀₃) in the VUV range of 83 000-84 800 cm -1 obtained using a single mode infrared laser revealed 24 rotationally resolved vibrational bands for the ion C₂H₄ +(X 2B 3u) ground state. The frequencies and symmetry of the vibrational bandsmore » thus determined, together with the anharmonic frequency predictions calculated at the CCSD(T)/aug-cc-pVQZ level, have allowed the unambiguous assignment of these vibrational bands. These bands are mostly combination bands. The measured frequencies of these bands yield the fundamental frequencies for V 8 + ) 1103± ( 10 cm -1 and V 10 + ) 813 ( 10 cm -1 of C₂H₄ +(X 2B 3u), which have not been determined previously. The present IR-VUV-PFI-PE study also provides truly rovibrationally selected and resolved state-to-state cross sections for the photoionization transitions C₂H₄(X~ 1A g; V 11, N' Ka' Kc') → C₂H₄ +(X ~ 2B 3u; V i +, N + Ka + Kc +), where N' Ka' Kc' denotes the rotational level of C₂H₄(X ~ 1Ag; V 11), and V i + and N + Ka + Kc + represent the vibrational and rotational states of the cation.« less

Pulsed ultraviolet light reduces immunoglobulin E binding to atlantic white shrimp (litopenaeus setiferus).

USDA-ARS?s Scientific Manuscript database

To date, the only effective method to prevent allergic reactions to shellfish is complete avoidance; however, if processing methods could be employed to minimize shellfish allergens before products reach consumers, illness could be substantially lessened. Pulsed ultraviolet light (PUV), a novel food...

Efficient high-harmonic generation from a stable and compact ultrafast Yb-fiber laser producing 100 μJ, 350 fs pulses based on bendable photonic crystal fiber

NASA Astrophysics Data System (ADS)

Feehan, James S.; Price, Jonathan H. V.; Butcher, Thomas J.; Brocklesby, William S.; Frey, Jeremy G.; Richardson, David J.

2017-01-01

The development of an Yb3+-fiber-based chirped-pulse amplification system and the performance in the generation of extreme ultraviolet (EUV) radiation by high-harmonic generation is reported. The fiber laser produced 100 μJ, 350 fs output pulses with diffraction-limited beam quality at a repetition rate of 16.7 kHz. The system used commercial single-mode, polarization maintaining fiber technology. This included a 40 μm core, easily packaged, bendable final amplifier fiber in order to enable a compact system, to reduce cost, and provide reliable and environmentally stable long-term performance. The system enabled the generation of 0.4 μW of EUV at wavelengths between 27 and 80 nm with a peak at 45 nm using xenon gas. The EUV flux of 1011 photons per second for a driving field power of 1.67 W represents state-of-the-art generation efficiency for single-fiber amplifier CPA systems, corresponding to a maximum calculated energy conversion efficiency of 2.4 × 10-7 from the infrared to the EUV. The potential for high average power operation at increased repetition rates and further suggested technical improvements are discussed. Future applications could include coherent diffractive imaging in the EUV, and high-harmonic spectroscopy.

Experimental and theoretical study on emission spectra of a nitrogen photoionized plasma induced by intense EUV pulses

NASA Astrophysics Data System (ADS)

Saber, Ismail; Bartnik, Andrzej; Skrzeczanowski, Wojciech; Wachulak, Przemyslaw; Jarocki, Roman; Fiedorowicz, Henryk; Limpouch, Jiri

2018-01-01

Spectral lines of low-temperature nitrogen photoionized plasma were investigated. The photoionized plasma was created in the result of irradiation N2 gas using laser plasma EUV radiation pulses. The source was based on a 10J/10ns Nd:YAG (λ = 1064 nm) laser system and a gas puff target. The EUV radiation pulses were collected and focused using a grazing incidence multifoil EUV collector. The emission spectra were measured in the ultraviolet and visible (UV/Vis) range. It was found that the plasma emission lines in the lower region of the UV range are relativley weak. Nonetheless, a part of the spectra contains strong molecular band in the 300 - 430 nm originated from second positive and first negative systems band transitions of nitrogen. These molecular band transitions were identified using a code for study the diatomic molecules, LIFBASE. The vibrational band of Δv = 0 and ±1 transitions were significantly populated than of that with Δv = ±2 and 3 transitions. A comparison of the calculated and measured spectrum is presented. With an assumption of a local thermodynamic equilibrium (LTE), the vibrational temperature was determined from the integrated band intensities with the help of the Boltzmann plot method and compared to the temperature predicted by SPECAIR and LIFBASE simulations. A summary of the results and the variations in the vibrational temperatures was discussed.

Temporal variations of electron density and temperature in Kr/Ne/H2 photoionized plasma induced by nanosecond pulses from extreme ultraviolet source

NASA Astrophysics Data System (ADS)

Saber, I.; Bartnik, A.; Wachulak, P.; Skrzeczanowski, W.; Jarocki, R.; Fiedorowicz, H.

2017-06-01

Spectral investigations of low-temperature photoionized plasmas created in a Kr/Ne/H2 gas mixture were performed. The low-temperature plasmas were generated by gas mixture irradiation using extreme ultraviolet pulses from a laser-plasma source. Emission spectra in the ultraviolet/visible range from the photoionized plasmas contained lines that mainly corresponded to neutral atoms and singly charged ions. Temporal variations in the plasma electron temperature and electron density were studied using different characteristic emission lines at various delay times. Results, based on Kr II lines, showed that the electron temperature decreased from 1.7 to 0.9 eV. The electron densities were estimated using different spectral lines at each delay time. In general, except for the Hβ line, in which the electron density decreased from 3.78 × 1016 cm-3 at 200 ns to 5.77 × 1015 cm-3 at 2000 ns, most of the electron density values measured from the different lines were of the order of 1015 cm-3 and decreased slightly while maintaining the same order when the delay time increased. The time dependences of the measured and simulated intensities of a spectral line of interest were also investigated. The validity of the partial or full local thermodynamic equilibrium (LTE) conditions in plasma was explained based on time-resolved electron density measurements. The partial LTE condition was satisfied for delay times in the 200 ns to 1500 ns range. The results are summarized, and the dominant basic atomic processes in the gas mixture photoionized plasma are discussed.

A study of the mechanical vibrations of a table-top extreme ultraviolet interference nanolithography tool.

PubMed

Prezioso, S; De Marco, P; Zuppella, P; Santucci, S; Ottaviano, L

2010-04-01

A prototype low cost table-top extreme ultraviolet (EUV) laser source (1.5 ns pulse duration, lambda=46.9 nm) was successfully employed as a laboratory scale interference nanolithography (INL) tool. Interference patterns were obtained with a simple Lloyd's mirror setup. Periodic structures on Polymethylmethacrylate/Si substrates were produced on large areas (8 mm(2)) with resolutions from 400 to 22.5 nm half pitch (the smallest resolution achieved so far with table-top EUV laser sources). The mechanical vibrations affecting both the laser source and Lloyd's setup were studied to determine if and how they affect the lateral resolution of the lithographic system. The vibration dynamics was described by a statistical model based on the assumption that the instantaneous position of the vibrating mechanical parts follows a normal distribution. An algorithm was developed to simulate the process of sample irradiation under different vibrations. The comparison between simulations and experiments allowed to estimate the characteristic amplitude of vibrations that was deduced to be lower than 50 nm. The same algorithm was used to reproduce the expected pattern profiles in the lambda/4 half pitch physical resolution limit. In that limit, a nonzero pattern modulation amplitude was obtained from the simulations, comparable to the peak-to-valley height (2-3 nm) measured for the 45 nm spaced fringes, indicating that the mechanical vibrations affecting the INL tool do not represent a limit in scaling down the resolution.

Fabrication of a high-density nano-porous structure on polyimide by using ultraviolet laser irradiation

NASA Astrophysics Data System (ADS)

Ma, Yong-Won; Jeong, Myung Yung; Lee, Sang-Mae; Shin, Bo Sung

2016-03-01

A new approach for fabricating a high-density nano-porous structure on polyimide (PI) by using a 355-nm UV laser is presented here. When PI was irradiated by using a laser, debris that had electrical conductivity was generated. Accordingly, that debris caused electrical defects in the field of electronics. Thus, many researchers have tried to focus on a clean processing without debris. However, this study focused on forming a high density of debris so as to fabricate a nano-porous structure consisting of nanofibers on the PI film. A PI film with closed pores and open pores was successfully formed by using a chemical blowing agent (azodicarbonamide, CBA) in an oven. Samples were precured at 130 °C and cured at 205 °C in sequence so that the closed pores might not coalesce in the film. When the laser irradiated the PI film with closed pores, nanofibers were generated because polyimide was not completely decomposed by photochemical ablation. Our results indicated that a film with micro-closed pores, in conjunction with a 355-nm pulsed laser, can facilitate the fabrication of a high-density nano-porous structure.

Laser Measurements of the H Atom + Ozone Rate Constant at Atmospheric Temperatures

NASA Astrophysics Data System (ADS)

Liu, Y.; Smith, G. P.; Peng, J.; Reppert, K. J.; Callahan, S. L.

2015-12-01

The exothermic H + O3 reaction produces OH(v) Meinel band emissions, used to derive mesospheric H concentrations and chemical heating rates. We have remeasured its rate constant to reduce resulting uncertainties and the measurement extend to lower mesospheric temperatures using modern laser techniques. H atoms are produced by pulsed ultraviolet laser trace photolysis of O3, followed by reaction of O(D) with added H2. A second, delayed, frequency-mixed dye laser measures the reaction decay rate with the remaining ozone by laser induced fluorescence. We monitor either the H atom decay by 2 photon excitation at 205 nm and detection of red fluorescence, or the OH(v=9) product time evolution with excitation of the B-X (0,9) band at 237 nm and emission in blue B-A bands. By cooling the enclosed low pressure flow cell we obtained measurements from 146-305 K. Small kinetic modeling corrections are made for secondary regeneration of H atoms. The results fully confirm the current NASA JPL recommendation for this rate constant, and establish its extrapolation down to the lower temperatures of the mesosphere. This work was supported by the NSF Aeronomy Program and an NSF Physics summer REU student grant.

All Fiber-Coupled OH Planar Laser-Induced-Fluorescence (OH-PLIF)-Based Two-Dimensional Thermometry.

PubMed

Hsu, Paul S; Jiang, Naibo; Patnaik, Anil K; Katta, Vish; Roy, Sukesh; Gord, James R

2018-04-01

Two-color, planar laser-induced fluorescence (PLIF)-based two-dimensional (2D) thermometry techniques for reacting flows, which are typically developed in the laboratory conditions, face a stiff challenge in their practical implementation in harsh environments such as combustion rigs. In addition to limited optical access, the critical experimental conditions (i.e., uncontrolled humidity, vibration, and large thermal gradients) often restrict sensitive laser system operation and cause difficulties maintaining beam-overlap. Thus, an all fiber-coupled, two-color OH-PLIF system has been developed, employing two long optical fibers allowing isolation of the laser and signal-collection systems. Two OH-excitation laser beams (∼283 nm and ∼286 nm) are delivered through a common 6 m long, 400 µm core, deep ultraviolet (UV)-enhanced multimode fiber. The fluorescence signal (∼310 nm) is collected by a 3 m long, UV-grade imaging fiber. Proof-of-principle temperature measurements are demonstrated in atmospheric pressure, near adiabatic, CH 4 /O 2 /N 2 jet flames. The effects of the excitation pulse interval on fiber transmission are investigated. The proof-of-principle measurements show significant promise for thermometry in harsh environments such as gas turbine engine tests.

Realization of a mW-level 10.7-eV (λ = 115.6 nm) laser by cascaded third harmonic generation of a Yb:fiber CPA laser at 1-MHz.

PubMed

Zhao, Zhigang; Kobayashi, Yohei

2017-06-12

We demonstrate a 10.7-eV (λ = 115.6 nm) laser with mW levels of average power and a 1-MHz repetition rate, which was driven by the third harmonic radiation (THG), at 347 nm, of an Yb:fiber chirped pulse amplifier (CPA) laser. The 347 nm ultraviolet radiation was obtained by frequency conversion of the high power output of a 1-MHz Yb:fiber CPA, using beta barium borate (BBO) nonlinear crystals. The frequency converted output was focused down into a gas cell filled with a mixture of Ar and Xe, and was subjected to a second THG frequency conversion. The generated 10.7-eV laser was separated from the fundamental beam using a LiF prism and no further separation from other harmonic waves was required. The highest measured output power was ~80 μW, which corresponded to an average power of ~1.25 mW inside the gas cell when the transmission coefficients of the LiF optics were taken into account. The corresponding conversion efficiency from 347 nm down to 115.6 nm was ~2.5 × 10 -4 .

Experimental observations of transport of picosecond laser generated electrons in a nail-like target

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

Pasley, J.; Wei, M.; Shipton, E.

2007-12-15

The transport of relativistic electrons, generated by the interaction of a high intensity (2x10{sup 20} W/cm{sup 2}) laser, has been studied in a nail-like target comprised of a 20 {mu}m diameter solid copper wire, coated with {approx}2 {mu}m of titanium, with an 80 {mu}m diameter hemispherical termination. A {approx}500 fs, {approx}200 J pulse of 1.053 {mu}m laser light produced by the Titan Laser at Lawrence Livermore National Laboratory was focused to a {approx}20 {mu}m diameter spot centered on the flat face of the hemisphere. K{sub {alpha}} fluorescence from the Cu and Ti regions was imaged together with extreme ultraviolet (XUV)more » emission at 68 and 256 eV. Results showed a quasiexponential decline in K{sub {alpha}} emission along the wire over a distance of a few hundred microns from the laser focus, consistent with bulk Ohmic inhibition of the relativistic electron transport. Weaker K{sub {alpha}} and XUV emission on a longer scale length showed limb brightening suggesting a transition to enhanced transport at the surface of the wire.« less

Paramagnetic dysprosium-doped zinc oxide thin films grown by pulsed-laser deposition

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

Lo, Fang-Yuh, E-mail: fangyuhlo@ntnu.edu.tw; Ting, Yi-Chieh; Chou, Kai-Chieh

2015-06-07

Dysprosium(Dy)-doped zinc oxide (Dy:ZnO) thin films were fabricated on c-oriented sapphire substrate by pulsed-laser deposition with doping concentration ranging from 1 to 10 at. %. X-ray diffraction (XRD), Raman-scattering, optical transmission spectroscopy, and spectroscopic ellipsometry revealed incorporation of Dy into ZnO host matrix without secondary phase. Solubility limit of Dy in ZnO under our deposition condition was between 5 and 10 at. % according to XRD and Raman-scattering characteristics. Optical transmission spectroscopy and spectroscopic ellipsometry also showed increase in both transmittance in ultraviolet regime and band gap of Dy:ZnO with increasing Dy density. Zinc vacancies and zinc interstitials were identified by photoluminescencemore » spectroscopy as the defects accompanied with Dy incorporation. Magnetic investigations with a superconducting quantum interference device showed paramagnetism without long-range order for all Dy:ZnO thin films, and a hint of antiferromagnetic alignment of Dy impurities was observed at highest doping concentration—indicating the overall contribution of zinc vacancies and zinc interstitials to magnetic interaction was either neutral or toward antiferromagnetic. From our investigations, Dy:ZnO thin films could be useful for spin alignment and magneto-optical applications.« less

Influence of RF excitation during pulsed laser deposition in oxygen atmosphere on the structural properties and luminescence of nanocrystalline ZnO:Al thin films

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

Meljanac, Daniel, E-mail: dmeljan@irb.hr; Plodinec, Milivoj; Siketić, Zdravko

2016-03-15

Thin ZnO:Al layers were deposited by pulsed laser deposition in vacuum and in oxygen atmosphere at gas pressures between 10 and 70 Pa and by applying radio-frequency (RF) plasma. Grazing incidence small angle x-ray scattering and grazing incidence x-ray diffraction (GIXRD) data showed that an increase in the oxygen pressure leads to an increase in the roughness, a decrease in the sample density, and changes in the size distribution of nanovoids. The nanocrystal sizes estimated from GIXRD were around 20 nm, while the sizes of the nanovoids increased from 1 to 2 nm with the oxygen pressure. The RF plasma mainly influenced themore » nanostructural properties and point defects dynamics. The photoluminescence consisted of three contributions, ultraviolet (UV), blue emission due to Zn vacancies, and red emission, which are related to an excess of oxygen. The RF excitation lowered the defect level related to blue emission and narrowed the UV luminescence peak, which indicates an improvement of the structural ordering. The observed influence of the deposition conditions on the film properties is discussed as a consequence of two main effects: the variation of the energy transfer from the laser plume to the growing film and changes in the growth chemistry.« less

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.

Fiber Bragg grating Fabry-Perot cavity sensor based on pulse laser demodulation technique

NASA Astrophysics Data System (ADS)

Gao, Fangfang; Chen, Jianfeng; Liu, Yunqi; Wang, Tingyun

2011-12-01

We demonstrate a fiber laser sensing technique based on fiber Bragg grating Fabry-Perot (FBG-FP) cavity interrogated by pulsed laser, where short pulses generated from active mode-locked erbium-doped fiber ring laser and current modulated DFB laser are adopted. The modulated laser pulses launched into the FBG-FP cavity produce a group of reflected pulses. The optical loss in the cavity can be determined from the power ratio of the first two pulses reflected from the cavity. This technique does not require high reflectivity FBGs and is immune to the power fluctuation of the light source. Two short pulse laser sources were compared experimentally with each other on pulse width, pulse stability, pulse chirp and sensing efficiency.

Short pulse free electron laser amplifier

DOEpatents

Schlitt, Leland G.; Szoke, Abraham

1985-01-01

Method and apparatus for amplification of a laser pulse in a free electron laser amplifier where the laser pulse duration may be a small fraction of the electron beam pulse duration used for amplification. An electron beam pulse is passed through a first wiggler magnet and a short laser pulse to be amplified is passed through the same wiggler so that only the energy of the last fraction, f, (f<1) of the electron beam pulse is consumed in amplifying the laser pulse. After suitable delay of the electron beam, the process is repeated in a second wiggler magnet, a third, . . . , where substantially the same fraction f of the remainder of the electron beam pulse is consumed in amplification of the given short laser pulse in each wiggler magnet region until the useful electron beam energy is substantially completely consumed by amplification of the laser pulse.

Scattered UV irradiation during VISX excimer laser keratorefractive surgery.

PubMed

Hope, R J; Weber, E D; Bower, K S; Pasternak, J P; Sliney, D H

2008-04-01

To evaluate the potential occupational health hazards associated with scattered ultraviolet (UV) radiation during photorefractive keratectomy (PRK) using the VISX Star S3 excimer laser. The Laser Vision Center, National Naval Medical Center, Bethesda, Maryland, USA. Intraoperative radiometric measurements were made with the Ophir Power/Energy Meter (LaserStar Model PD-10 with silicon detector) during PRK treatments as well as during required calibration procedures at a distance of 20.3 cm from the left cornea. These measurements were evaluated using a worst-case scenario for exposure, and then compared with the American Conference of Governmental Industrial Hygeinists (ACGIH) Threshold Value Limits (TVL) to perform a risk/hazard analysis. During the PRK procedures, the highest measured value was 248.4 nJ/pulse. During the calibration procedures, the highest measured UV scattered radiation level was 149.6 nJ/pulse. The maximum treatment time was 52 seconds. Using a worst-case scenario in which all treatments used the maximum power and time, the total energy per eye treated was 0.132 mJ/cm2 and the total UV radiation at close range (80 cm from the treated eye) was 0.0085 mJ/cm2. With a workload of 20 patients, the total occupational exposure at 80 cm to actinic UV radiation in an 8-hour period would be 0.425 mJ/cm2. The scattered actinic UV laser radiation from the VISX Star S3 excimer laser did not exceed occupational exposure limits during a busy 8-hour workday, provided that operating room personnel were at least 80 cm from the treated eye. While the use of protective eyewear is always prudent, this study demonstrates that the trace amounts of scattered laser emissions produced by this laser do not pose a serious health risk even without the use of protective eyewear.

Ultraviolet Polariton Laser

DTIC Science & Technology

2015-09-17

Ultraviolet Polariton Laser Significant progress was achieved in the epitaxy of deep UV AlN/ AlGaN Bragg mirrors and microcavity structures paving...the way to the successful fabrication of vertical cavity emitting laser structures and polariton lasers. For the first time DBRs providing sufficient...high reflectivity for polariton emission were demonstrated. Thanks to a developed strain balanced Al0.85Ga0.15N template, the critical thickness

Optical Control of Internal Conversion in Pyrazine

NASA Astrophysics Data System (ADS)

Barry, Grant; Singha, Sima; Hu, Zhan; Seideman, Tamar; Gordon, Robert

2014-03-01

We apply quantum control schemes previously reserved for atoms and small molecules to more complex polyatomic molecules. Pyrazine was chosen as a model polyatomic molecule for its well-studied conical intersection seam between the S1 and S2 potential energy surfaces (PESs). Using shaped ultraviolet femtosecond laser pulses, we demonstrate optical control of the excited state dynamics of this molecule under collisionless conditions. This was achieved in a pump-probe experiment by employing a genetic algorithm programmed to suppress ionization of the pyrazine molecules at a preselected time. Our findings indicate that the optimized pulses localize the wave packet for times up to 1.5 ps at a location on the coupled S1/S2 PESs where ionization is energetically forbidden. Our approach is general and does not require knowledge of the molecular Hamiltonian. Funding provided by National Science Foundation grant no. CHE-0848198.

Solid-state harmonics beyond the atomic limit.

PubMed

Ndabashimiye, Georges; Ghimire, Shambhu; Wu, Mengxi; Browne, Dana A; Schafer, Kenneth J; Gaarde, Mette B; Reis, David A

2016-06-23

Strong-field laser excitation of solids can produce extremely nonlinear electronic and optical behaviour. As recently demonstrated, this includes the generation of high harmonics extending into the vacuum-ultraviolet and extreme-ultraviolet regions of the electromagnetic spectrum. High harmonic generation is shown to occur fundamentally differently in solids and in dilute atomic gases. How the microscopic mechanisms in the solid and the gas differ remains a topic of intense debate. Here we report a direct comparison of high harmonic generation in the solid and gas phases of argon and krypton. Owing to the weak van der Waals interaction, rare (noble)-gas solids are a near-ideal medium in which to study the role of high density and periodicity in the generation process. We find that the high harmonic generation spectra from the rare-gas solids exhibit multiple plateaus extending well beyond the atomic limit of the corresponding gas-phase harmonics measured under similar conditions. The appearance of multiple plateaus indicates strong interband couplings involving multiple single-particle bands. We also compare the dependence of the solid and gas harmonic yield on laser ellipticity and find that they are similar, suggesting the importance of electron-hole recollision in these solids. This implies that gas-phase methods such as polarization gating for attosecond pulse generation and orbital tomography could be realized in solids.

Molecular dynamics study of lubricant depletion by pulsed laser heating

NASA Astrophysics Data System (ADS)

Seo, Young Woo; Rosenkranz, Andreas; Talke, Frank E.

2018-05-01

In this study, molecular dynamics simulations were performed to numerically investigate the effect of pulsed laser heating on lubricant depletion. The maximum temperature, the lubricant depletion width, the number of evaporated lubricant beads and the number of fragmented lubricant chains were studied as a function of laser peak power, pulse duration and repetition rate. A continuous-wave laser and a square pulse laser were simulated and compared to a Gaussian pulse laser. With increasing repetition rate, pulsed laser heating was found to approach continuous-wave laser heating.

"Defense-in-Depth" Laser Safety and the National Ignition Facility

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

King, J J

The National Ignition Facility (NIF) is the largest and most energetic laser in the world contained in a complex the size of a football stadium. From the initial laser pulse, provided by telecommunication style infrared nanoJoule pulsed lasers, to the final 192 laser beams (1.8 Mega Joules total energy in the ultraviolet) converging on a target the size of a pencil eraser, laser safety is of paramount concern. In addition to this, there are numerous high-powered (Class 3B and 4) diagnostic lasers in use that can potentially send their laser radiation travelling throughout the facility. With individual beam paths ofmore » up to 1500 meters and a workforce of more than one thousand, the potential for exposure is significant. Simple laser safety practices utilized in typical laser labs just don't apply. To mitigate these hazards, NIF incorporates a multi layered approach to laser safety or 'Defense in Depth.' Most typical high-powered laser operations are contained and controlled within a single room using relatively simplistic controls to protect both the worker and the public. Laser workers are trained, use a standard operating procedure, and are required to wear Personal Protective Equipment (PPE) such as Laser Protective Eyewear (LPE) if the system is not fully enclosed. Non-workers are protected by means of posting the room with a warning sign and a flashing light. In the best of cases, a Safety Interlock System (SIS) will be employed which will 'safe' the laser in the case of unauthorized access. This type of laser operation is relatively easy to employ and manage. As the operation becomes more complex, higher levels of control are required to ensure personnel safety. Examples requiring enhanced controls are outdoor and multi-room laser operations. At the NIF there are 192 beam lines and numerous other Class 4 diagnostic lasers that can potentially deliver their hazardous energy to locations far from the laser source. This presents a serious and complex potential hazard to personnel. Because of this, a multilayered approach to safety is taken. This paper presents the philosophy and approach taken at the NIF in the multi-layered 'defense-in-depth' approach to laser safety.« less

Injection locked oscillator system for pulsed metal vapor lasers

DOEpatents

Warner, Bruce E.; Ault, Earl R.

1988-01-01

An injection locked oscillator system for pulsed metal vapor lasers is disclosed. The invention includes the combination of a seeding oscillator with an injection locked oscillator (ILO) for improving the quality, particularly the intensity, of an output laser beam pulse. The present invention includes means for matching the first seeder laser pulses from the seeding oscillator to second laser pulses of a metal vapor laser to improve the quality, and particularly the intensity, of the output laser beam pulse.

Use of near infrared femtosecond lasers as sub-micron radiation microbeam for cell DNA damage and repair studies.

PubMed

Botchway, S W; Reynolds, P; Parker, A W; O'Neill, P

2010-01-01

Laser induced radiation microbeam technology for radiobiology research is undergoing rapid growth because of the increased availability and ease of use of femtosecond laser sources. The main processes involved are multiphoton absorption and/or plasma formation. The high peak powers these lasers generate make them ideal tools for depositing sub-micrometer size radiant energy within a region of a living cell nucleus to activate ionising and/or photochemically driven processes. The technique allows questions relating to the effects of low doses of radiation, the propagation and treatment of deoxyribonucleic acid (DNA) damage and repair in individual live cells as well as non-targeted cell to cell effects to be addressed. This mini-review focuses on the use of near infrared (NIR) ca. 800nm radiation to induce damage that is radically different from the early and subsequent ultraviolet microbeam techniques. Ultrafast pulsed NIR instrumentation has many benefits including the ability to eliminate issues of unspecific UV absorption by the many materials prevalent within cells. The multiphoton interaction volume also permits energy deposition beyond the diffraction limit. Work has established that the fundamental process of the damage induced by the ultrashort laser pulses is different to those induced from continuous wave light sources. Pioneering work has demonstrated that NIR laser microbeam radiation can mimic ionising radiation via multiphoton absorption within the 3D femtolitre volume of the highly focused Gaussian beam. This light-matter interaction phenomenon provides a novel optical microbeam probe for mimicking both complex ionising and UV radiation-type cell damage including double strand breaks (DSBs) and base damage. A further advantage of the pulsed laser technique is that it provides further scope for time-resolved experiments. Recently the NIR laser microbeam technique has been used to investigate the recruitment of repair proteins to the sub-micrometre size area of damage in viable cells using both immuno-fluorescent staining of gamma-H2AX (a marker for DSBs) and real-time imaging of GFP-labelled repair proteins including ATM, p53 binding protein 1 (53BP1), RAD51 and Ku 70/80 to elucidate the interaction of the two DNA DSB repair pathways, homologous recombination and the non-homologous end joining pathway. 2010 Elsevier B.V. All rights reserved.

Laser capture microdissection: Arcturus(XT) infrared capture and UV cutting methods.

PubMed

Gallagher, Rosa I; Blakely, Steven R; Liotta, Lance A; Espina, Virginia

2012-01-01

Laser capture microdissection (LCM) is a technique that allows the precise procurement of enriched cell populations from a heterogeneous tissue under direct microscopic visualization. LCM can be used to harvest the cells of interest directly or can be used to isolate specific cells by ablating the unwanted cells, resulting in histologically enriched cell populations. The fundamental components of laser microdissection technology are (a) visualization of the cells of interest via microscopy, (b) transfer of laser energy to a thermolabile polymer with either the formation of a polymer-cell composite (capture method) or transfer of laser energy via an ultraviolet laser to photovolatize a region of tissue (cutting method), and (c) removal of cells of interest from the heterogeneous tissue section. Laser energy supplied by LCM instruments can be infrared (810 nm) or ultraviolet (355 nm). Infrared lasers melt thermolabile polymers for cell capture, whereas ultraviolet lasers ablate cells for either removal of unwanted cells or excision of a defined area of cells. LCM technology is applicable to an array of applications including mass spectrometry, DNA genotyping and loss-of-heterozygosity analysis, RNA transcript profiling, cDNA library generation, proteomics discovery, and signal kinase pathway profiling. This chapter describes the unique features of the Arcturus(XT) laser capture microdissection instrument, which incorporates both infrared capture and ultraviolet cutting technology in one instrument, using a proteomic downstream assay as a model.

Counter-facing plasma guns for efficient extreme ultra-violet plasma light source

NASA Astrophysics Data System (ADS)

Kuroda, Yusuke; Yamamoto, Akiko; Kuwabara, Hajime; Nakajima, Mitsuo; Kawamura, Tohru; Horioka, Kazuhiko

2013-11-01

A plasma focus system composed of a pair of counter-facing coaxial guns was proposed as a long-pulse and/or repetitive high energy density plasma source. We applied Li as the source of plasma for improvement of the conversion efficiency, the spectral purity, and the repetition capability. For operation of the system with ideal counter-facing plasma focus mode, we changed the system from simple coaxial geometry to a multi-channel configuration. We applied a laser trigger to make synchronous multi-channel discharges with low jitter. The results indicated that the configuration is promising to make a high energy density plasma with high spectral efficiency.

Investigation and Characterization of Defects in Epitaxial Films for Ultraviolet Light Emitting Devices Using FUV Time-Resolved Photoluminescence, Time-Resolved Cathodoluminescence, and Spatio-Time-Resolved Cathodoluminescence Excited Using Femtosecond Laser Pulses

DTIC Science & Technology

2013-05-22

mole fraction AlxGa1-xN alloys, and GaN were studied in this project. For this purpose, we quantified the radiative lifetimes (R) and nonradiative ...61556;R) and nonradiative lifetimes (NR) for the near-band-edge (NBE) emission by measuring the luminescence lifetimes () and...that is a fraction of radiative rate over the sum of radiative and nonradiative rates; i. e. int=(1+R/NR)-1. To improve int of practical devices

Characteristics of ultraviolet light and radicals formed by pulsed discharge in water

NASA Astrophysics Data System (ADS)

Sun, Bing; Kunitomo, Shinta; Igarashi, Chiaki

2006-09-01

In this investigation, the ultraviolet light characteristics and OH radical properties produced by a pulsed discharge in water were studied. For the plate-rod reactor, it was found that the ultraviolet light energy has a 3.2% total energy injected into the reactor. The ultraviolet light changed with the peak voltage and electrode distance. UV characteristics in tap water and the distilled water are given. The intensity of the OH radicals was the highest for the 40 mm electrode distance reactor. In addition, the properties of hydrogen peroxide and ozone were also studied under arc discharge conditions. It was found that the OH radicals were in the ground state and the excited state when a pulsed arc discharge was used. The ozone was produced by the arc discharge even if the oxygen gas is not bubbled into the reactor. The ozone concentration produces a maximum value with treatment time.

Method and apparatus for controlling carrier envelope phase

DOEpatents

Chang, Zenghu [Manhattan, KS; Li, Chengquan [Sunnyvale, CA; Moon, Eric [Manhattan, KS

2011-12-06

A chirped pulse amplification laser system. The system generally comprises a laser source, a pulse modification apparatus including first and second pulse modification elements separated by a separation distance, a positioning element, a measurement device, and a feedback controller. The laser source is operable to generate a laser pulse and the pulse modification apparatus operable to modify at least a portion of the laser pulse. The positioning element is operable to reposition at least a portion of the pulse modification apparatus to vary the separation distance. The measurement device is operable to measure the carrier envelope phase of the generated laser pulse and the feedback controller is operable to control the positioning element based on the measured carrier envelope phase to vary the separation distance of the pulse modification elements and control the carrier envelope phase of laser pulses generated by the laser source.

Heterodyne laser diagnostic system

DOEpatents

Globig, Michael A.; Johnson, Michael A.; Wyeth, Richard W.

1990-01-01

The heterodyne laser diagnostic system includes, in one embodiment, an average power pulsed laser optical spectrum analyzer for determining the average power of the pulsed laser. In another embodiment, the system includes a pulsed laser instantaneous optical frequency measurement for determining the instantaneous optical frequency of the pulsed laser.

Effect of pulse profile and chirp on a laser wakefield generation

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

Zhang Xiaomei; Shen Baifei; Ji Liangliang

2012-05-15

A laser wakefield driven by an asymmetric laser pulse with/without chirp is investigated analytically and through two-dimensional particle-in-cell simulations. For a laser pulse with an appropriate pulse length compared with the plasma wavelength, the wakefield amplitude can be enhanced by using an asymmetric un-chirped laser pulse with a fast rise time; however, the growth is small. On the other hand, the wakefield can be greatly enhanced for both positively chirped laser pulse having a fast rise time and negatively chirped laser pulse having a slow rise time. Simulations show that at the early laser-plasma interaction stage, due to the influencemore » of the fast rise time the wakefield driven by the positively chirped laser pulse is more intense than that driven by the negatively chirped laser pulse, which is in good agreement with analytical results. At a later time, since the laser pulse with positive chirp exhibits opposite evolution to the one with negative chirp when propagating in plasma, the wakefield in the latter case grows more intensely. These effects should be useful in laser wakefield acceleration experiments operating at low plasma densities.« less

Design of micro-second pulsed laser mode for ophthalmological CW self-raman laser

NASA Astrophysics Data System (ADS)

Mota, Alessandro D.; Rossi, Giuliano; Ortega, Tiago A.; Costal, Glauco Z.; Fontes, Yuri C.; Yasuoka, Fatima M. M.; Stefani, Mario A.; de Castro N., Jarbas C.; Paiva, Maria S. V.

2011-02-01

This work presents the mechanisms adopted for the design of micro-second pulsed laser mode for a CW Self-Raman laser cavity in 586nm and 4W output power. The new technique for retina disease treatment discharges laser pulses on the retina tissue, in laser sequences of 200 μs pulse duration at each 2ms. This operation mode requires the laser to discharge fast electric pulses, making the system control velocity of the electronic system cavity vital. The control procedures to keep the laser output power stable and the laser head behavior in micro-second pulse mode are presented.

Single attosecond pulse generation by using plasmon-driven double optical gating technology in crossed metal nanostructures

NASA Astrophysics Data System (ADS)

Feng, Liqiang; Liu, Katheryn

2018-05-01

An effective method to obtain the single attosecond pulses (SAPs) by using the multi-cycle plasmon-driven double optical gating (DOG) technology in the specifically designed metal nanostructures has been proposed and investigated. It is found that with the introduction of the crossed metal nanostructures along the driven and the gating polarization directions, not only the harmonic cutoff can be extended, but also the efficient high-order harmonic generation (HHG) at the very highest orders occurs only at one side of the region inside the nanostructure. As a result, a 93 eV supercontinuum with the near stable phase can be found. Further, by properly introducing an ultraviolet (UV) pulse into the driven laser polarization direction (which is defined as the DOG), the harmonic yield can be enhanced by two orders of magnitude in comparison with the singe polarization gating (PG) technology. However, as the polarized angle or the ellipticity of the UV pulse increase, the enhancement of the harmonic yield is slightly reduced. Finally, by superposing the selected harmonics from the DOG scheme, a 30 as SAP with intensity enhancement of two orders of magnitude can be obtained.

Picosecond pulse measurements using the active laser medium

NASA Technical Reports Server (NTRS)

Bernardin, James P.; Lawandy, N. M.

1990-01-01

A simple method for measuring the pulse lengths of synchronously pumped dye lasers which does not require the use of an external nonlinear medium, such as a doubling crystal or two-photon fluorescence cell, to autocorrelate the pulses is discussed. The technique involves feeding the laser pulses back into the dye jet, thus correlating the output pulses with the intracavity pulses to obtain pulse length signatures in the resulting time-averaged laser power. Experimental measurements were performed using a rhodamine 6G dye laser pumped by a mode-locked frequency-doubled Nd:YAG laser. The results agree well with numerical computations, and the method proves effective in determining lengths of picosecond laser pulses.

OH Planar Laser Induced Fluorescence (PLIF) Measurements for the Study of High Pressure Flames: An Evaluation of a New Laser and a New Camera System

NASA Technical Reports Server (NTRS)

Tedder, Sarah; Hicks, Yolanda

2012-01-01

Planar laser induced fluorescence (PLIF) is used by the Combustion Branch at the NASA Glenn Research Center (NASA Glenn) to assess the characteristics of the flowfield produced by aircraft fuel injectors. To improve and expand the capabilities of the PLIF system new equipment was installed. The new capabilities of the modified PLIF system are assessed by collecting OH PLIF in a methane/air flame produced by a flat flame burner. Specifically, the modifications characterized are the addition of an injection seeder to a Nd:YAG laser pumping an optical parametric oscillator (OPO) and the use of a new camera with an interline CCD. OH fluorescence results using the injection seeded OPO laser are compared to results using a Nd:YAG pumped dye laser with ultraviolet extender (UVX). Best settings of the new camera for maximum detection of PLIF signal are reported for the controller gain and microchannel plate (MCP) bracket pulsing. Results are also reported from tests of the Dual Image Feature (DIF) mode of the new camera which allows image pairs to be acquired in rapid succession. This allows acquisition of a PLIF image and a background signal almost simultaneously. Saturation effects in the new camera were also investigated and are reported.

Laser-produced plasma EUV source using a colloidal microjet target containing tin dioxide nanoparticles

NASA Astrophysics Data System (ADS)

Higashiguchi, Takeshi; Dojyo, Naoto; Sasaki, Wataru; Kubodera, Shoichi

2006-10-01

We realized a low-debris laser-produced plasma extreme ultraviolet (EUV) source by use of a colloidal microjet target, which contained low-concentration (6 wt%) tin-dioxide nanoparticles. An Nd:YAG laser was used to produce a plasma at the intensity on the order of 10^11 W/cm^2. The use of low concentration nanoparticles in a microjet target with a diameter of 50 μm regulated the neutral debris emission from a target, which was monitored by a silicon witness plate placed 30 cm apart from the source in a vacuum chamber. No XPS signals of tin and/or oxygen atoms were observed on the plate after ten thousand laser exposures. The low concentration nature of the target was compensated and the conversion efficiency (CE) was improved by introducing double pulses of two Nd:YAG lasers operated at 532 and 1064 nm as a result of controlling the micro-plasma characteristics. The EUV CE reached its maximum of 1.2% at the delay time of approximately 100 ns with the main laser intensiy of 2 x10^11 W/cm^2. The CE value was comparable to that of a tin bulk target, which, however, produced a significant amount of neutral debris.

High Intensity Femtosecond XUV Pulse Interactions with Atomic Clusters: Final Report

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

Ditmire, Todd

We propose to expand our recent studies on the interactions of intense extreme ultraviolet (XUV) femtosecond pulses with atomic and molecular clusters. The work described follows directly from work performed under BES support for the past grant period. During this period we upgraded the THOR laser at UT Austin by replacing the regenerative amplifier with optical parametric amplification (OPA) using BBO crystals. This increased the contrast of the laser, the total laser energy to ~1.2 J , and decreased the pulse width to below 30 fs. We built a new all reflective XUV harmonic beam line into expanded lab space. This enabled an increase influence by a factor ofmore » 25 and an increase in the intensity by a factor of 50. The goal of the program proposed in this renewal is to extend this class of experiments to available higher XUV intensity and a greater range of wavelengths. In particular we plan to perform experiments to confirm our hypothesis about the origin of the high charge states in these exploding clusters, an effect which we ascribe to plasma continuum lowering (ionization potential depression) in a cluster nano-­plasma. To do this we will perform experiments in which XUV pulses of carefully chosen wavelength irradiate clusters composed of only low-Z atoms and clusters with a mixture of this low-­Z atom with higher Z atoms. The latter clusters will exhibit higher electron densities and will serve to lower the ionization potential further than in the clusters composed only of low Z atoms. This should have a significant effect on the charge states produced in the exploding cluster. We will also explore the transition of explosions in these XUV irradiated clusters from hydrodynamic expansion to Coulomb explosion. The work proposed here will explore clusters of a wider range of constituents, including clusters from solids. Experiments on clusters from solids will be enabled by development we performed during the past grant period in which we constructed and tested a cluster generator based on the Laser Ablation of Microparticles (LAM) method.« less

Impact of pulsed xenon ultraviolet light on hospital-acquired infection rates in a community hospital.

PubMed

Vianna, Pedro G; Dale, Charles R; Simmons, Sarah; Stibich, Mark; Licitra, Carmelo M

2016-03-01

The role of contaminated environments in the spread of hospital-associated infections has been well documented. This study reports the impact of a pulsed xenon ultraviolet no-touch disinfection system on infection rates in a community care facility. This study was conducted in a community hospital in Southern Florida. Beginning November 2012, a pulsed xenon ultraviolet disinfection system was implemented as an adjunct to traditional cleaning methods on discharge of select rooms. The technology uses a xenon flashlamp to generate germicidal light that damages the DNA of organisms in the hospital environment. The device was implemented in the intensive care unit (ICU), with a goal of using the pulsed xenon ultraviolet system for disinfecting all discharges and transfers after standard cleaning and prior to occupation of the room by the next patient. For all non-ICU discharges and transfers, the pulsed xenon ultraviolet system was only used for Clostridium difficile rooms. Infection data were collected for methicillin-resistant Staphylococcus aureus, C difficile, and vancomycin-resistant Enterococci (VRE). The intervention period was compared with baseline using a 2-sample Wilcoxon rank-sum test. In non-ICU areas, a significant reduction was found for C difficile. There was a nonsignificant decrease in VRE and a significant increase in methicillin-resistant S aureus. In the ICU, all infections were reduced, but only VRE was significant. This may be because of the increased role that environment plays in the transmission of this pathogen. Overall, there were 36 fewer infections in the whole facility and 16 fewer infections in the ICU during the intervention period than would have been expected based on baseline data. Implementation of pulsed xenon ultraviolet disinfection is associated with significant decreases in facility-wide and ICU infection rates. These outcomes suggest that enhanced environmental disinfection plays a role in the risk mitigation of hospital-acquired infections. Copyright © 2015 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

Tabletop imaging of structural evolutions in chemical reactions demonstrated for the acetylene cation

NASA Astrophysics Data System (ADS)

Ibrahim, Heide; Wales, Benji; Beaulieu, Samuel; Schmidt, Bruno E.; Thiré, Nicolas; Fowe, Emmanuel P.; Bisson, Éric; Hebeisen, Christoph T.; Wanie, Vincent; Giguére, Mathieu; Kieffer, Jean-Claude; Spanner, Michael; Bandrauk, André D.; Sanderson, Joseph; Schuurman, Michael S.; Légaré, François

2014-07-01

The introduction of femto-chemistry has made it a primary goal to follow the nuclear and electronic evolution of a molecule in time and space as it undergoes a chemical reaction. Using Coulomb Explosion Imaging, we have shot the first high-resolution molecular movie of a to and fro isomerization process in the acetylene cation. So far, this kind of phenomenon could only be observed using vacuum ultraviolet light from a free-electron laser. Here we show that 266 nm ultrashort laser pulses are capable of initiating rich dynamics through multiphoton ionization. With our generally applicable tabletop approach that can be used for other small organic molecules, we have investigated two basic chemical reactions simultaneously: proton migration and C=C bond breaking, triggered by multiphoton ionization. The experimental results are in excellent agreement with the timescales and relaxation pathways predicted by new and quantitative ab initio trajectory simulations.

Advanced Gouy phase high harmonics interferometer

NASA Astrophysics Data System (ADS)

Mustary, M. H.; Laban, D. E.; Wood, J. B. O.; Palmer, A. J.; Holdsworth, J.; Litvinyuk, I. V.; Sang, R. T.

2018-05-01

We describe an extreme ultraviolet (XUV) interferometric technique that can resolve ∼100 zeptoseconds (10‑21 s) delay between high harmonic emissions from two successive sources separated spatially along the laser propagation in a single Gaussian beam focus. Several improvements on our earlier work have been implemented in the advanced interferometer. In this paper, we report on the design, characterization and optimization of the advanced Gouy phase interferometer. Temporal coherence for both atomic argon and molecular hydrogen gases has been observed for several harmonic orders. It has been shown that phase shift of XUV pulses mainly originates from the emission time delay due to the Gouy phase in the laser focus and the observed interference is independent of the generating medium. This interferometer can be a useful tool for measuring the relative phase shift between any two gas species and for studying ultrafast dynamics of their electronic and nuclear motion.

Changing of optical absorption and scattering coefficients in nonlinear-optical crystal lithium triborate before and after interaction with UV-radiation

NASA Astrophysics Data System (ADS)

Demkin, Artem S.; Nikitin, Dmitriy G.; Ryabushkin, Oleg A.

2016-04-01

In current work optical properties of LiB3O5 (LBO) crystal with ultraviolet (UV) (λ= 266 nm) induced volume macroscopic defect (track) are investigated using novel piezoelectric resonance laser calorimetry technique. Pulsed laser radiation of 10 W average power at 532 nm wavelength, is consecutively focused into spatial regions with and without optical defect. For these cases exponential fitting of crystal temperature kinetics measured during its irradiation gives different optical absorption coefficients α1 = 8.1 • 10-4 cm-1 (region with defect) and α =3.9ṡ10-4 cm-1 (non-defected region). Optical scattering coefficient is determined as the difference between optical absorption coefficients measured for opaque and transparent lateral facets of the crystal respectively. Measurements reveal that scattering coefficient of LBO in the region with defect is three times higher than the optical absorption coefficient.

Femtopulse laser-based mask repair in the DUV wavelength regime

NASA Astrophysics Data System (ADS)

Ghadiali, Firoz; Tolani, Vikram; Nagpal, Rajesh; Robinson, Tod; LeClaire, Jeff; Bozak, Ron; Lee, David A.; White, Roy

2006-05-01

Deep ultraviolet (DUV) femtosecond-pulsed laser ablation has numerous highly desirable properties for subtractive photomask defect repair. These qualities include high removal rates, resolution better than the focused spot size, minimized redeposition of the ablated material (rollup and splatter), and a negligible heat affected zone. The optical properties of the photomask result in a broad repair process window because the absorber film (whether Cr or MoSi) and the transmissive substrate allow for a high degree of material removal selectivity. Repair results and process parameters from such a system are examined in light of theoretical considerations. In addition, the practical aspects of the operation of this system in a production mask house environment are reviewed from the standpoint of repair quality, capability, availability, and throughput. Focus is given to the benefit received by the mask shop, and to the technical performance of the system.

Pulsed laser induced optical nonlinearities in undoped, copper doped and chromium doped CdS quantum dots

NASA Astrophysics Data System (ADS)

Sharma, Dimple; Malik, B. P.; Gaur, Arun

2015-04-01

Quantum dots (QDs) of CdS, Cu doped and Cr doped CdS were synthesized through chemical co- precipitation method. The synthesized QDs have been characterized by x-ray diffraction, ultraviolet visible absorption spectroscopy. The diameters of QDs were calculated using Debye-Scherrer’s formula and Brus equation. They are found to be in 3.5-3.8 nm range. The nonlinear properties has been studied by the open and closed aperture Z-scan technique using frequency double Nd:YAG laser. The nonlinear refractive index (n2), nonlinear absorption coefficient (β), third order nonlinear susceptibilities (χ3) of QDs has been calculated. It has been found that the values of nonlinear parameters are higher for doped QDs than undoped CdS QDs. Hence they can be regarded as potential material for the development of optoelectronics and photonics devices.

Kinetic processes determining attainable pulse repetition rate in pulsed metal vapor lasers

NASA Astrophysics Data System (ADS)

Petrash, Gueorgii G.

1998-06-01

A review of the investigations of the main processes determining the attainable pulse repetition rate of elemental metal vapor pulsed gas discharge self-terminating lasers, such as copper vapor laser, gold vapor laser, lead vapor laser, is given. Kinetic processes during an excitation pulse and interpulse period are considered as well as experiments with lasers operating at high repetition rate.

Wide band laser-plasma soft X-ray source using a gas puff target for direct photo-etching of polymers

NASA Astrophysics Data System (ADS)

Bartnik, Andrzej; Fiedorowicz, Henryk; Jarocki, Roman; Kostecki, Jerzy; Rakowski, Rafał; Szczurek, Mirosław

2005-09-01

Organic polymers (PMMA, PTFE, PET, and PI) are considered as the important materials in microengineering, especially for biological and medical applications. Micromachining of such materials is possible with the use of different techniques that involve electromagnetic radiation or charged particle beams. Another possibility of high aspect ratio micromachining of PTFE is direct photo-etching using synchrotron radiation. X-ray and ultraviolet radiation from other sources, for micromachining of materials by direct photo-etching can be also applied. In this paper we present the results of investigation of a wide band soft X-ray source and its application for direct photo-etching of organic polymers. X-ray radiation in the wavelength range from about 3 nm to 20 nm was produced as a result of irradiation of a double-stream gas puff target with laser pulses of energy 0.8 J and time duration of about 3 ns. The spectra, plasma size and absolute energies of soft X-ray pulses for different gas puff targets were measured. Photo-etching process of polymers irradiated with the use of the soft X-ray radiation was analyzed and investigated. Samples of organic polymers were placed inside a vacuum chamber of the x-ray source, close to the gas puff target at the distance of about 2 cm from plasmas created by focused laser pulses. A fine metal grid placed in front of the samples was used as a mask to form structures by x-ray ablation. The results of photo-etching process for several minutes exposition with l0Hz repetition rate were presented. High ablation efficiency was obtained with the use of the gas puff target containing xenon surrounded by helium.

Nonlinear optics with coherent free electron lasers

NASA Astrophysics Data System (ADS)

Bencivenga, F.; Capotondi, F.; Mincigrucci, R.; Cucini, R.; Manfredda, M.; Pedersoli, E.; Principi, E.; Simoncig, A.; Masciovecchio, C.

2016-12-01

We interpreted the recent construction of free electron laser (FELs) facilities worldwide as an unprecedented opportunity to bring concepts and methods from the scientific community working with optical lasers into the domain of x-ray science. This motivated our efforts towards the realization of FEL-based wave-mixing applications. In this article we present new extreme ultraviolet transient grating (X-TG) data from vitreous SiO2, collected using two crossed FEL pulses (photon frequency 38 eV) to generate the X-TG and a phase matched optical probing pulse (photon frequency 3.1 eV). This experiment extends our previous investigation, which was carried out on a nominally identical sample using a different FEL photon frequency (45 eV) to excite the X-TG. The present data are featured by a peak intensity of the X-TG signal substantially larger than that previously reported and by slower modulations of the X-TG signal at positive delays. These differences could be ascribed to the different FEL photon energy used in the two experiments or to differences in the sample properties. A systematic X-TG study on the same sample as a function of the FEL wavelength is needed to draw a consistent conclusion. We also discuss how the advances in the performance of the FELs, in terms of generation of fully coherent photon pulses and multi-color FEL emission, may push the development of original experimental strategies to study matter at the femtosecond-nanometer time-length scales, with the unique option of element and chemical state specificity. This would allow the development of advanced experimental tools based on wave-mixing processes, which may have a tremendous impact in the study of a large array of phenomena, ranging from nano-dynamics in complex materials to charge and energy transfer processes.

Impact of pulse duration on Ho:YAG laser lithotripsy: fragmentation and dusting performance.

PubMed

Bader, Markus J; Pongratz, Thomas; Khoder, Wael; Stief, Christian G; Herrmann, Thomas; Nagele, Udo; Sroka, Ronald

2015-04-01

In vitro investigations of Ho:YAG laser-induced stone fragmentation were performed to identify potential impacts of different pulse durations on stone fragmentation characteristics. A Ho:YAG laser system (Swiss LaserClast, EMS S.A., Nyon, Switzerland) with selectable long or short pulse mode was tested with regard to its fragmentation and laser hardware compatibility properties. The pulse duration is depending on the specific laser parameters. Fragmentation tests (hand-held, hands-free, single-pulse-induced crater) on artificial BEGO stones were performed under reproducible experimental conditions (fibre sizes: 365 and 200 µm; laser settings: 10 W through combinations of 0.5, 1, 2 J/pulse and 20, 10, 5 Hz, respectively). Differences in fragmentation rates between the two pulse duration regimes were detected with statistical significance for defined settings. Hand-held and motivated Ho:YAG laser-assisted fragmentation of BEGO stones showed no significant difference between short pulse mode and long pulse mode, neither in fragmentation rates nor in number of fragments and fragment sizes. Similarly, the results of the hands-free fragmentation tests (with and without anti-repulsion device) showed no statistical differences between long pulse and short pulse modes. The study showed that fragmentation rates for long and short pulse durations at identical power settings remain at a comparable level. Longer holmium laser pulse duration reduces stone pushback. Therefore, longer laser pulses may result in better clinical outcome of laser lithotripsy and more convenient handling during clinical use without compromising fragmentation effectiveness.

Acousto-optic replication of ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Yushkov, Konstantin B.; Molchanov, Vladimir Ya.; Ovchinnikov, Andrey V.; Chefonov, Oleg V.

2017-10-01

Precisely controlled sequences of ultrashort laser pulses are required in various scientific and engineering applications. We developed a phase-only acousto-optic pulse shaping method for replication of ultrashort laser pulses in a TW laser system. A sequence of several Fourier-transform-limited pulses is generated from a single femtosecond laser pulse by means of applying a piecewise linear phase modulation over the whole emission spectrum. Analysis demonstrates that the main factor which limits maximum delay between the pulse replicas is spectral resolution of the acousto-optic dispersive delay line used for pulse shaping. In experiments with a Cr:forsterite laser system, we obtained delays from 0.3 to 3.5 ps between two replicas of 190 fs transform-limited pulses at the central wavelength of laser emission, 1230 nm.

Laser-assisted solar-cell metallization processing

NASA Technical Reports Server (NTRS)

Dutta, S.

1984-01-01

A photolytic metal deposition system using a focused continuous wave ultraviolet laser, a photolytic metal deposition system using a mask and ultraviolet flood illumination, and a pyrolytic metal deposition system using a focused continuous wave laser were studied. Fabrication of solar cells, as well as characterization to determine the effects of transient heat on solar cell junctions were investigated.

Laser Materials and Laser Spectroscopy - A Satellite Meeting of IQEC '88

NASA Astrophysics Data System (ADS)

Wang, Zhijiang; Zhang, Zhiming

1989-03-01

The Table of Contents for the book is as follows: * Laser Materials * Laser Site Spectroscopy of Transition Metal Ions in Glass * Spectroscopy of Chromium Doped Tunable Laser Materials * Spectroscopic Properties of Nd3+ Ions in LaMgAl11O19 Crystal * Spectral Study and 2.938 μm Laser Emission of Er3+ in the Y3Al5O12 Crystal * Raman-infrared Spectra and Radiationless Relaxation of Laser Crystal NdAl3(BO3)4 * A Study on HB and FLN in BaFCl0.5Br0.5:Sm2+ at 77K * Pair-pumped Upconversion Solid State Lasers * CW Upconversion Laser Action in Neodymium and Erbium doped Solids * Ultra-high Sensitive Upconversion Fluorescence of YbF3 Doped with Trace Tm3+ and Er3+ * The Growth and Properties of NYAB and EYAB Multifunctional Crystal * Study on Fluorescence and Laser Light of Er3+ in Glass * Growth and Properties of Single Crystal Fibers for Laser Materials * A Study on the Quality of Sapphire, Ruby and Ti3+ Doped Sapphire Grown by Temperature Gradient Technique (TGT) and Czochralski Technique (CZ) * The Measurement of Output Property of Ti3+ Al2O3 Laser Crystal * An Xα Study of the Laser Crystal MgF2 : V2+ * Q-switched NAB Laser * Miniature YAG Lasers * Study of High Efficiency {LiF}:{F}^-_2 Color Center Crystals * Study on the Formation Conditions and Optical Properties of (F2+)H Color Center in NaCl:OH- Crystals * Novel Spectroscopic Properties of {LiF}:{F}^+_3 - {F}_2 Mixed Color Centers Laser Crystals * Terraced Substrate Visible GaAlAs Semiconductor Lasers with a Large Optical Cavity * The Temperature Dependence of Gain Spectra, Threshold Current and Auger Recombination in InGaAsP-InP Double Heterojunction Laser diode * Time-resolved Photoluminescence and Energy Transfer of Bound Excitons in GaP:N Crystals * Optical Limiting with Semiconductors * A Critical Review of High-efficiency Crystals for Tunable Lasers * Parametric Scattering in β - BaB2O4 Crystal Induced by Picosecond Pulses * Generation of Picosecond Pulses at 193 nm by Frequency Mixing in β - BaB2O4 * Mixing Frequency Generation of 271.0 - 291.5 nm in β - BaB2O4 * Low Temperature Absorption Steps Near Ultraviolet Intrinsic Edge in Beta Barium Metaborate * The Growth and Properties of BaTiO3 Crystals * High-order Phenomena Accompanied with Self-pumped Phase Conjugation in BaTiO * Growth and Laser Damage Estimation of Potassium Dihydrogen Phosphate Crystals for Laser Fusion * Noncritically Phase-matched KTP for Diode-pumped Lasers (400-700 nm) * Potassium Titanyl Phosphate (KTP): Properties and New Applications * A Kind of New Defect in KTP Crystal and its SHG Enhanced Effect * Nucleation and Growth of the Non-linear Optical Crystal Potassium Pentaborate Tetrahydrate * Quasi-periodic Oscillations in Photoinduced Conical Light Scattering from LiNbO3 : Fe Crystals * Laser Excited Photoreflectance of GaxIn1-xAs/InP Multiple Quantum Wells * Growth, Spectroscopic Properties and Applications of Doped LiNbO3 Crystals * Photorefractive and Photovoltaic Effect in Doped LiNbO3 * Recent Advances in Photorefractive Nonlinear Optics * Study on the Doubling-frequency and Anti-photorefractive Property of Heavily Magnesium-doped Lithium-rich Lithium Niobate Crystals * A New Technique for Increasing Two-wave Mixing Gain in Photorefractive Bi12SiO20 Crystals * Experimental Proof: There Existing Another Mechanism of Photorefractive Index in Crystal Ce-SBN * Effect of Crystal Annealing on Holographic Recording in Bismuth Silicon Oxide * Two Wave Coupling in KNbO3 Photorefractive Crystal * Photorefractive Effects in Nd-Doped Ferroelectric (KxNa1-x)0.4-(SryBa1-y)0.8 Nb2O6 Single Crystal * High Pressure Raman Spectra and the Effect of Pressure to the Ferroelastic Phase Transition in LnP5O15 * Time-delay Four-wave Mixing with Incoherent Light in Absorption Bands Treated as a Multi-level System * Pulsed Laser Induced Dislocation Structure in Lithium Fluoride Single Crystals * Laser Spectroscopy * Nonclassical Radiation from Single-atom Oscillators * Laser Spectroscopic Studies of Molecules in Highly Excited Vibrational State * Investigation of the Stark Effect in Xenon Autoionizing Rydberg Series with the Use of Coherent Tunable XUV Radiation * Laser Spectroscopy of Autoionising 5 dnf J = 4.5 Rydberg Series of Ba I * Resonance Photoionization Spectroscopy of Atoms: Autoionization and Highly Excited States of Kr and U * Stark Spectra of Strontium and Calcium Atoms * Observation of Bidirectional Stimulated Radiation at 330 nm, 364 nm and 718 nm with 660 nm Laser Pumping in Sodium Vapour * Study of Molecular Rydberg States and their Discriminations in Na2 * The Measurement of the High Excited Spectra of Samarium by using Stepwise Laser Excitation Method * Product Analysis in the Reaction of the Two-photon Excited Xe(5p56p) States with Freons * Photoionization Spectra of Ca and Sr Atoms above the Classical Field-ionization Threshold * Effect of Medium Background on the Hydrogen Spectrum * Photoemission and Photoelectron Spectra from Autoionizing Atoms in Strong Laser Field * Natural Radiative Lifetime Measurements of High-lying States of Samarium * Two-step Laser Excitation of nf Rydberg States in Neutral Al and Observation of Stark Effect * Measurements of Excited Spectra of the Refractory Metal Elements using Discharge Synchronized with the Laser Pulse * Multiphoton Ionization of Atomic Lead at 1.06μ * Kinetic Processes in the Electron-beam pumped KrF Laser * Laser-induced Fluorescence of Zn2 Excimer * Calculation of Transition Intensity in Heteronuclear Dimer NaK: Comparison with Experiment * Laser-induced Fluorescence of CCl2 Carbene * Study of Multiphoton Ionization Spectrum of Benzene and Two-photon Absorption Cross Section * Dicke Narrowing of N2O Linewidth Perturbed by N2 at 10 μm Band * Polyatomic Molecular Ions Studied by Laser Photodissociation Spectroscopy * Transverse-optically Pumped Ultraviolet S2 Laser * Multiphoton Ionization of Propanal by High Power Laser * UV MPI Mass Spectroscopy and Dynamics of Photodissociation of SO2 * Multiphoton Ionization-fragmentation Patterns of Ethylamine and Dimethylamine Isomers * Cars Measurements of SF6 Pumped by a CO2 Laser Pulse * Angular Dependence of Phase Conjugation of CO2 Laser on SF6 Gas * Resolution of Stretching-vibrational and Translational Raman Bands of Liquid Water by Means of Polarization Four-photon Spectroscopy * Laser-produced Plasma as an Effective Source for X-Ray Spectroscopy * Rotational Structure of the Low Lying Electronic States of Samarium Monoxide * Effects of Poling and Stretching on Second-harmonic Generation in Amorphous Vinylidene Cyanide/Vinyl Acetate Copolymer * Laser-induced Spectroscopy of Cardiovascular Tissues * Laser-excited Malignancy Autofluorescence for Tumour Malignancy Investigation and its Origin * A Study on Several Hematoporphyrin Derivatives by Time-resolved Spectroscopy * Research on Strong Field Processes with a Subpicosecond 400 GW Ultraviolet Source * Growth, Decay and Quenching of Stimulated Raman Scattering in Transparent Liquid Droplets * Layer Condensed Ammonia Studied by Photoacoustic Spectroscopy * High Efficiency Raman Conversion of XeCl Laser Radiation in Lead Vapor * Combined Effect of Stimulated Scattering and Phase Modulation on Generation of Supercontinum * Resonant Multiwave Mixing in Sodium Vapor * High Pressure Brillouin Scattering in Liquid Toluene * Optical Nonlinearities and Bistability in Gold Colloid * Sum-frequency Generation for Surface Vibrational Spectroscopy * Optical Studies of Molecule/Surface Interactions * Optical Second Harmonic Generation with Coupled Surface Plasmons from a Multi-layer Silver/Quartz Grating * Evidence of Silver Cluster and its Role in Surface Enhanced Raman Scattering (SERS) * Study on Cold-evaporated Silver Surfaces with Second-harmonic-generation * Study of Optical Second-harmonic-generation at Metal Surface with Polarization States * Spectroscopic Studies of J-Aggregates of Pseudoisocyanine in Molecular Monolayers in the Range 300 to 20 K * Study of Polymerization of Langmuir-Blodgett Monolayer by Surface Enhanced Raman Scattering * Dynamics of Laser-induced Etching of Si(III) Surface of Chlorine * Fourier Transform Heterodyne Spectroscopy of Liquid Interfaces * Generation of High Power UV Femtosecond Pulses * Femtosecond Photon Echoes * Transition Radiation of Femtosecond Optical Pulses * Observation of DFWN in a Saturable Absorber inside the CPM Ring Dye Laser Cavity * Study on the Induced Spectral Superbroadening of Ultrafast Laser Pulse in a Nonlinear Medium * Laser Cooling and Trapping of Atoms * Femtosecond Absorption Spectroscopy of Primary Processes in Bacterial Photosynthesis Reaction Centers * Observation of the Motion of Slow Atoms in a Standing Wave Field * The Interrelation between the Optical Properties and the MBE Growth Control of Quantum Well Structures * Ionic Excimers * Optical SHG Study on Polymerization of Langmuir-Blodgett Molecular Layers * Weak Localization of Light * Statistical Fragmentation Patterns of Metastable Ion: Comparison with Experiment * Oxygeneration Reaction of Cerium with XeCl Laser * Measurement of Verdet Coefficient and Magneto-optic Spectroscopy in terms of Beats * Study on Rhodamine 6G/Xylene and Red B Laser Dye Mixture System * Ultranarrow Absorption Resonances of Cold Particles and their Application in Spectroscopy and Optical Frequency Standards * The Dynamics of Ion Clouds in Paul Traps: Implications for Frequency Standard Applications * Frequency Stability Measurement of Zeeman Stabilized He-Ne Laser * Multi-wavelength CW He-Ne Laser and its Frequency Stabilization * Efficient Isotope Separation using Semiconductor Lasers * Multi-beam Circularly Polarized Holography * Ring Laser Opticity Meter * Improved Rademacher Functions and Rademacher Transform * Note

Single- and multi-photon ionization studies of organosulfur species

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

Cheung, Yu -San

1999-02-12

Accurate ionization energies (IE`s) for molecular species are used for prediction of chemical reactivity and are of fundamental importance to chemists. The IE of a gaseous molecule can be determined routinely in a photoionization or a photoelectron experiment. IE determinations made in conventional photoionization and photoelectron studies have uncertainties in the range of 3--100 meV (25--250 cm -1). In the past decade, the most exciting development in the field of photoionization and photoelectron spectroscopy has been the availability of high resolution, tunable ultraviolet (UV) and vacuum ultraviolet (VUV) laser sources. The laser pulsed field ionization photoelectron (PFI-PE) scheme is currentlymore » the state-of-the-art photoelectron spectroscopic technique and is capable of providing photoelectron energy resolution close to the optical resolution. The author has focused attention on the photoionization processes of some sulfur-containing species. The studies of the photoionization and photodissociation on sulfur-containing compounds [such as CS 2, CH 3SH, CH 3SSCH 3, CH 3CH 2SCH 2CH 3, HSCH 2CH 2SH and C 4H 4S (thiophene) and sulfur-containing radicals, such as HS, CS, CH 3S, CH 3CH 2S and CH 3SS], have been the major subjects in the group because sulfur is an important species contributing to air pollution in the atmosphere. The modeling of the combustion and oxidation of sulfur compounds represents important steps for the control of both the production and the elimination of sulfur-containing pollutants. Chapter 1 is a general introduction of the thesis. Chapters 2 and 6 contain five papers published in, or accepted for publication in, academic periodicals. In Chapter 7, the progress of the construction in the laboratory of a new vacuum ultraviolet laser system equipped with a reflectron mass spectrometer is presented. Chapters 2 through 7 have been removed for separate processing. A general conclusion of these studies are given in Chapter 8 followed by an appendix.« less

Synchronization of pulses from mode-locked lasers

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

Harvey, G.T.

A study of the synchronization of mode-locked lasers is presented. In particular, we investigate the timing of the laser output pulses with respect to the radio frequency (RF) signal driving the mode-locking elements in the laser cavity. Two types of mode-locked lasers are considered: a cw loss-modulated mode-locked argon ion laser; and a q-switched active-passive mode-locked Nd:YAG laser. We develop theoretical models for the treatment of laser pulse synchronization in both types of lasers. Experimental results are presented on a combined laser system that synchronizes pulses from both an argon ion and a Nd:YAG laser by using a common RFmore » signal to drive independent mode-lockers in both laser cavities. Shot to shot jitter as low as 18 ps (RMS) was measured between the output pulses from the two lasers. The theory of pulse synchronization for the cw loss-modulated mode-locked argon ion laser is based on the relationship between the timing of the mode-locked laser pulse (with respect to the peak of the RF signal) and the length of the laser cavity. Experiments on the argon laser include the measurement of the phase shift of the mode-locked pulse as a function of cavity length and intracavity intensity. The theory of synchronization of the active-passive mode-locked Nd:YAG laser is an extension of the pulse selection model of the active-passive laser. Experiments on the active-passive Nd:YAG laser include: measurement of the early noise fluctuations; measurement of the duration of the linear build-up stage (time between laser threshold and saturation of the absorber); measurement of jitter as a function of the mode-locker modulation depth; and measurement of the output pulse phase shift as a function of cavity length.« less

Vacuum Ultraviolet Photoionization of Complex Chemical Systems

DOE PAGES

Kostko, Oleg; Bandyopadhyay, Biswajit; Ahmed, Musahid

2016-02-24

Tunable vacuum ultraviolet (VUV) radiation coupled to mass spectrometry is applied to the study of complex chemical systems in this paper. The identification of novel reactive intermediates and radicals is revealed in flame, pulsed photolysis, and pyrolysis reactors, leading to the elucidation of spectroscopy, reaction mechanisms, and kinetics. Mass-resolved threshold photoelectron photoion coincidence measurements provide unprecedented access to vibrationally resolved spectra of free radicals present in high-temperature reactors. Photoionization measurements in water clusters, nucleic acid base dimers, and their complexes with water provide signatures of proton transfer in hydrogen-bonded and π-stacked systems. Experimental and theoretical methods to track ion–molecule reactionsmore » and fragmentation pathways in intermolecular and intramolecular hydrogen-bonded systems in sugars and alcohols are described. Photoionization of laser-ablated molecules, clusters, and their reaction products inform thermodynamics and spectroscopy that are relevant to astrochemistry and catalysis. Finally, new directions in coupling VUV radiation to interrogate complex chemical systems are discussed.« less

Laser-pulse shape effects on magnetic field generation in underdense plasmas

NASA Astrophysics Data System (ADS)

Gopal, Krishna; Raja, Md. Ali; Gupta, Devki Nandan; Avinash, K.; Sharma, Suresh C.

2018-07-01

Laser pulse shape effect has been considered to estimate the self-generated magnetic field in laser-plasma interaction. A ponderomotive force based physical mechanism has been proposed to investigate the self-generated magnetic field for different spatial profiles of the laser pulse in inhomogeneous plasmas. The spatially inhomogeneous electric field of a laser pulse imparts a stronger ponderomotive force on plasma electrons. Thus, the stronger ponderomotive force associated with the asymmetric laser pulse generates a stronger magnetic field in comparison to the case of a symmetric laser pulse. Scaling laws for magnetic field strength with the laser and plasma parameters for different shape of the pulse have been suggested. Present study might be helpful to understand the plasma dynamics relevant to the particle trapping and injection in laser-plasma accelerators.

The development of novel Ytterbium fiber lasers and their applications

NASA Astrophysics Data System (ADS)

Nie, Bai

The aim of my Ph.D. research is to push the fundamental limits holding back the development of novel Yb fiber lasers with high pulse energy and short pulse duration. The purpose of developing these lasers is to use them for important applications such as multiphoton microscopy and laser-induced breakdown spectroscopy. My first project was to develop a short-pulse high-energy ultrafast fiber laser for multiphoton microscopy. To achieve high multiphoton efficiency and depth resolved tissue imaging, ultrashort pulse duration and high pulse energy are required. In order to achieve this, an all-normal dispersion cavity design was adopted. Output performances of the built lasers were investigated by varying several cavity parameters, such as pump laser power, fiber length and intra-cavity spectral filter bandwidth. It was found that the length of the fiber preceding the gain fiber is critical to the laser performance. Generally, the shorter the fiber is, the broader the output spectrum is. The more interesting parameter is the intra-cavity spectral filter bandwidth. Counter intuitively, laser cavities using narrower bandwidth spectral filters generated much broader spectra. It was also found that fiber lasers with very narrow spectral filters produced laser pulses with parabolic profile, which are referred to as self-similar pulses or similaritons. This type of pulse can avoid wave-breaking and is an optimal approach to generate pulses with high pulse energy and ultrashort pulse duration. With a 3nm intra-cavity spectral filter, output pulses with about 20 nJ pulse energy were produced and compressed to about 41 fs full-width-at-half-maximum (FWHM) pulse duration. Due to the loss in the compression device, the peak power of the compressed pulses is about 250 kW. It was the highest peak power generated from a fiber oscillator when this work was published. This laser was used for multiphoton microscopy on living tissues like Drosophila larva and fruit fly wings. Several imaging methods, such as two-photon-excited fluorescence, second harmonic generation, and third harmonic generation, were performed. Not only were single layers of thin tissue imaged, but also depth resolved imaging of thick samples was tested, and three-dimensional image reconstruction was demonstrated. The other project was to develop a simple fiber oscillator for laser-induced breakdown spectroscopy (LIBS). Laser pulses with high energy, high ablation efficiency and low ablation threshold are desirable for this application. We built a fiber laser using up to 200 m long fiber and scaled the output pulse energy up to 450 nJ. This laser was operated in an unusual mode-locking regime and produced noise-like pulses, which have a picosecond long pulse envelope containing multiple irregular femtosecond sub-pulses. This type of pulse was mostly ignored by many earlier researchers. Intra-cavity spectral filters did not affect the laser performance as much as in the similariton lasers and were removed from the laser cavity. Characteristics of our noise-like laser, such as MHz repetition rate, broad spectrum, and picosecond-long pulse envelope containing multiple femtosecond sub-pulses, were found to meet the requirement of an ideal laser source for LIBS. A simple LIBS setup using our laser was demonstrated and atomic emission spectra with very good signal-to-noise ratio were obtained. Composition detection, qualitative concentration determination, and trace detection were also tested. These tests show that our noise-like fiber laser is an ideal laser source for a low-cost and portable LIBS system.

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.

Determination of polycyclic aromatic hydrocarbons and their nitro-, amino-derivatives absorbed on particulate matter 2.5 by multiphoton ionization mass spectrometry using far-, deep-, and near-ultraviolet femtosecond lasers.

PubMed

Tang, Yuanyuan; Imasaka, Tomoko; Yamamoto, Shigekazu; Imasaka, Totaro

2016-06-01

Multiphoton ionization processes of parent-polycyclic aromatic hydrocarbons (PPAHs), nitro-PAHs (NPAHs), and amino-PAHs (APAHs) were examined by gas chromatography combined with time-of-flight mass spectrometry using a femtosecond Ti:sapphire laser as the ionization source. The efficiency of multiphoton ionization was examined using lasers emitting in the far-ultraviolet (200 nm), deep-ultraviolet (267 nm), and near-ultraviolet (345 nm) regions. The largest signal intensities were obtained when the far-ultraviolet laser was employed. This favorable result can be attributed to the fact that these compounds have the largest molar absorptivities in the far-ultraviolet region. On the other hand, APAHs were ionized more efficiently than NPAHs in the near-ultraviolet region because of their low ionization energies. A sample extracted from a real particulate matter 2.5 (PM2.5) sample was measured, and numerous signal peaks arising from PAH and its analogs were observed at 200 nm. On the other hand, only a limited number of signed peaks were observed at 345 nm, some of which were signed to PPAHs, NPAHs, and APAHs. Thus, multiphoton ionization mass spectrometry has potential for the use in comprehensive analysis of toxic environmental pollutants. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

Plogmaker, Stefan; Johansson, Erik M. J.; Rensmo, Haakan

A novel light chopper system for fast timing experiments in the vacuum-ultraviolet (VUV) and x-ray spectral region has been developed. It can be phase-locked and synchronized with a synchrotron radiation storage ring, accommodating repetition rates in the range of {approx}8 to {approx}120 kHz by choosing different sets of apertures and subharmonics of the ring frequency (MHz range). Also the opening time of the system can be varied from some nanoseconds to several microseconds to meet the needs of a broad range of applications. Adjusting these parameters, the device can be used either for the generation of single light pulses ormore » pulse packages from a microwave driven, continuous He gas discharge lamp or from storage rings which are otherwise often considered as quasi-continuous light sources. This chopper can be utilized for many different kinds of experiments enabling, for example, unambiguous time-of-flight (TOF) multi-electron coincidence studies of atoms and molecules excited by a single light pulse as well as time-resolved visible laser pump x-ray probe electron spectroscopy of condensed matter in the valence and core level region.« less

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.

Time-resolved production and detection of reactive atoms

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

Grossman, L. W.; Hurst, G. S.

1977-09-01

Cesium iodide in the presence of a buffer gas was dissociated with a pulsed ultraviolet laser, which will be referred to as the source laser. This created a population of atoms at a well defined time and in a compact, well defined volume. A second pulsed laser, with a beam that completely surrounded that of the first, photoionized the cesium after a known time delay. This laser will be referred to as the detector laser. It was determined that for short time delays, all of the cesium atoms were easily ionized. When focused, the source laser generated an extremely intensemore » fluence. By accounting for the beam intensity profile it was shown that all of the molecules in the central portion of the beam can be dissociated and detected. Besides proving the feasibility of single-molecule detection, this enabled a determination of the absolute photodissociation cross section as a function of wavelength. Initial studies of the time decay of the cesium signal at low argon pressures indicated a non-exponential decay. This was consistent with a diffusion mechanism transporting cesium atoms out of the laser beam. Therefore, it was desired to conduct further experiments using a tightly focused source beam, passing along the axis of the detector beam. The theoretical behavior of this simple geometry accounting for diffusion and reaction is easily calculated. A diffusion coefficient can then be extracted by data fitting. If reactive decay is due to impurities constituting a fixed percentage of the buffer gas, then two-body reaction rates will scale linearly with pressure and three-body reaction rates will scale quadratically. Also, the diffusion coefficient will scale inversely with pressure. At low pressures it is conceivable that decay due to diffusion would be sufficiently rapid that all other processes can be neglected. Extraction of a diffusion coefficient would then be quite direct. Finally, study of the reaction of cesium and oxygen was undertaken.« less

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.

Effect of Pulsed Ultraviolet Light and High Hydrostatic Pressure on the Antigenicity of Almond Protein Extracts.

USDA-ARS?s Scientific Manuscript database

The efficacy of pulsed ultraviolet light (PUV) and high hydrostatic pressure (HHP) on reducing the IgE binding to the almond extracts, was studied using SDS-PAGE, Western Blot, and ELISA probed with human plasma containing IgE antibodies to almond allergens, and a polyclonal antibody against almond ...

Bibliography of Soviet Laser Developments. Number 43, September-October 1979.

DTIC Science & Technology

1980-06-01

Laser Materials, Ultrashort Pulse Generation, X-ray Lasers , Gamma Lasers , Laser Theory, Laser Biological Effects, Laser Communications, Laser ...chemical lasers ; components; nonlinear optics; spectroscopy of laser materials; ultrashort pulse generation; theoretical aspects of advanced lasers ; and...and A.L. Traynin (0). Study on single crystals of shaped germanium, irradiated by a pulsed CO 2 laser .

Nanoplasmonic generation of ultrashort EUV pulses

NASA Astrophysics Data System (ADS)

Choi, Joonhee; Lee, Dong-Hyub; Han, Seunghwoi; Park, In-Yong; Kim, Seungchul; Kim, Seung-Woo

2012-10-01

Ultrashort extreme-ultraviolet (EUV) light pulses are an important tool for time-resolved pump-probe spectroscopy to investigate the ultrafast dynamics of electrons in atoms and molecules. Among several methods available to generate ultrashort EUV light pulses, the nonlinear frequency upconversion process of high-harmonic generation (HHG) draws attention as it is capable of producing coherent EUV pulses with precise control of burst timing with respect to the driving near-infrared (NIR) femtosecond laser. In this report, we present and discuss our recent experimental data obtained by the plasmon-driven HHG method that generate EUV radiation by means of plasmonic nano-focusing of NIR femtosecond pulses. For experiment, metallic waveguides having a tapered hole of funnel shape inside were fabricated by adopting the focused-ion-beam process on a micro-cantilever substrate. The plasmonic field formed within the funnelwaveguides being coupled with the incident femtosecond pulse permitted intensity enhancement by a factor of ~350, which creates a hot spot of sub-wavelength size with intensities strong enough for HHG. Experimental results showed that with injection of noble gases into the funnel-waveguides, EUV radiation is generated up to wavelengths of 32 nm and 29.6 nm from Ar and Ne gas atoms, respectively. Further, it was observed that lower-order EUV harmonics are cut off in the HHG spectra by the tiny exit aperture of the funnel-waveguide.

Laser radiography forming bremsstrahlung radiation to image an object

DOEpatents

Perry, Michael D.; Sefcik, Joseph A.

2004-01-13

A method of imaging an object by generating laser pulses with a short-pulse, high-power laser. When the laser pulse strikes a conductive target, bremsstrahlung radiation is generated such that hard ballistic high-energy electrons are formed to penetrate an object. A detector on the opposite side of the object detects these electrons. Since laser pulses are used to form the hard x-rays, multiple pulses can be used to image an object in motion, such as an exploding or compressing object, by using time gated detectors. Furthermore, the laser pulses can be directed down different tubes using mirrors and filters so that each laser pulse will image a different portion of the object.

A vacuum ultraviolet laser pulsed field ionization-photoion study of methane (CH 4): Determination of the appearance energy of methylium from methane with unprecedented precision and the resulting impact on the bond dissociation energies of CH 4 and CH 4 +

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

Chang, Yih -Chung; Xiong, Bo; Bross, David H.

Here, we report on the successful implementation of a high-resolution vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection method for the study of unimolecular dissociation of quantum-state- or energy-selected molecular ions. As a test case, we have determined the 0 K appearance energy (AE 0) for the formation of methylium, CH 3 +, from methane, CH 4, as AE 0 (CH 3 +/CH 4) = 14.32271 ± 0.00013 eV. This value has a significantly smaller error limit, but is otherwise consistent with previous laboratory and/or synchrotron-based studies of this dissociative photoionization onset. Furthermore, the sum of the VUV lasermore » PFI-PI spectra obtained for the parent CH 4 + ion and the fragment CH 3 + ions of methane is found to agree with the earlier VUV pulsed field ionization-photoelectron (VUV-PFI-PE) spectrum of methane, providing unambiguous validation of the previous interpretation that the sharp VUV-PFI-PE step observed at the AE 0 (CH 3 +/CH 4) threshold ensues because of higher PFI detection efficiency for fragment CH 3 + than for parent CH 4 +. This, in turn, is a consequence of the underlying high- n Rydberg dissociation mechanism for the dissociative photoionization of CH 4, which was proposed in previous synchrotron-based VUV-PFI-PE and VUV-PFI-PEPICO studies of CH 4. The present highly accurate 0 K dissociative ionization threshold for CH 4 can be utilized to derive accurate values for the bond dissociation energies of methane and methane cation. For methane, the straightforward application of sequential thermochemistry via the positive ion cycle leads to some ambiguity because of two competing VUV-PFI-PE literature values for the ionization energy of methyl radical. The ambiguity is successfully resolved by applying the Active Thermochemical Tables (ATcT) approach, resulting in D 0 (H-CH 3) = 432.463 ± 0.027 kJ/mol and D 0(H-CH 3 +) = 164.701 ± 0.038 kJ/mol.« less

A vacuum ultraviolet laser pulsed field ionization-photoion study of methane (CH 4): Determination of the appearance energy of methylium from methane with unprecedented precision and the resulting impact on the bond dissociation energies of CH 4 and CH 4 +

DOE PAGES

Chang, Yih -Chung; Xiong, Bo; Bross, David H.; ...

2017-03-27

Here, we report on the successful implementation of a high-resolution vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection method for the study of unimolecular dissociation of quantum-state- or energy-selected molecular ions. As a test case, we have determined the 0 K appearance energy (AE 0) for the formation of methylium, CH 3 +, from methane, CH 4, as AE 0 (CH 3 +/CH 4) = 14.32271 ± 0.00013 eV. This value has a significantly smaller error limit, but is otherwise consistent with previous laboratory and/or synchrotron-based studies of this dissociative photoionization onset. Furthermore, the sum of the VUV lasermore » PFI-PI spectra obtained for the parent CH 4 + ion and the fragment CH 3 + ions of methane is found to agree with the earlier VUV pulsed field ionization-photoelectron (VUV-PFI-PE) spectrum of methane, providing unambiguous validation of the previous interpretation that the sharp VUV-PFI-PE step observed at the AE 0 (CH 3 +/CH 4) threshold ensues because of higher PFI detection efficiency for fragment CH 3 + than for parent CH 4 +. This, in turn, is a consequence of the underlying high- n Rydberg dissociation mechanism for the dissociative photoionization of CH 4, which was proposed in previous synchrotron-based VUV-PFI-PE and VUV-PFI-PEPICO studies of CH 4. The present highly accurate 0 K dissociative ionization threshold for CH 4 can be utilized to derive accurate values for the bond dissociation energies of methane and methane cation. For methane, the straightforward application of sequential thermochemistry via the positive ion cycle leads to some ambiguity because of two competing VUV-PFI-PE literature values for the ionization energy of methyl radical. The ambiguity is successfully resolved by applying the Active Thermochemical Tables (ATcT) approach, resulting in D 0 (H-CH 3) = 432.463 ± 0.027 kJ/mol and D 0(H-CH 3 +) = 164.701 ± 0.038 kJ/mol.« less

Process for laser machining and surface treatment

DOEpatents

Neil, George R.; Shinn, Michelle D.

2004-10-26

An improved method and apparatus increasing the accuracy and reducing the time required to machine materials, surface treat materials, and allow better control of defects such as particulates in pulsed laser deposition. The speed and quality of machining is improved by combining an ultrashort pulsed laser at high average power with a continuous wave laser. The ultrashort pulsed laser provides an initial ultrashort pulse, on the order of several hundred femtoseconds, to stimulate an electron avalanche in the target material. Coincident with the ultrashort pulse or shortly after it, a pulse from a continuous wave laser is applied to the target. The micromachining method and apparatus creates an initial ultrashort laser pulse to ignite the ablation followed by a longer laser pulse to sustain and enlarge on the ablation effect launched in the initial pulse. The pulse pairs are repeated at a high pulse repetition frequency and as often as desired to produce the desired micromachining effect. The micromachining method enables a lower threshold for ablation, provides more deterministic damage, minimizes the heat affected zone, minimizes cracking or melting, and reduces the time involved to create the desired machining effect.

Dual sub-picosecond and sub-nanosecond laser system

NASA Astrophysics Data System (ADS)

Xie, Xinglong; Liu, Fengqiao; Yang, Jingxin; Yang, Xin; Li, Meirong; Xue, Zhiling; Gao, Qi; Guan, Fuyi; Zhang, Weiqing; Huang, Guanlong; Zhuang, Yifei; Han, Aimei; Lin, Zunqi

2003-11-01

A high power laser system delivering a 20-TW, 0.5 - 0.8 ps ultra-short laser pulse and a 20-J, 500-ps long pulse simultaneously in one shot is completed. This two-beam laser operates at the wavelength of 1053 nm and uses Nd doped glass as the gain media of the main amplification chain. The chirped-pulse amplification (CPA) technology is used to compress the stretched laser pulse. After compression, the ultrashort laser pulse is measured: energy above 16.0 J, S/N contrast ratio ~ 10^(5) : 1, filling factor ~>52.7%. Another long pulse beam is a non-compressed chirped laser pulse, which is measured: energy ~ 20 J, pulse duration 500 ps. The two beams are directed onto the target surface at an angle of 15°.

Guiding of laser pulses in plasma waveguides created by linearly-polarized femtosecond laser pulses

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

Lemos, N.; Cardoso, L.; Geada, J.

We experimentally demonstrate that plasma waveguides produced with ultra-short laser pulses (sub-picosecond) in gas jets are capable of guiding high intensity laser pulses. This scheme has the unique ability of guiding a high-intensity laser pulse in a plasma waveguide created by the same laser system in the very simple and stable experimental setup. A hot plasma column was created by a femtosecond class laser that expands into an on-axis parabolic low density profile suitable to act as a waveguide for high intensity laser beams. We have successfully guided ~10 15 W cm -2 laser pulses in a 8 mm longmore » hydrogen plasma waveguide with a 35% guiding efficiency.« less

Guiding of laser pulses in plasma waveguides created by linearly-polarized femtosecond laser pulses

DOE PAGES

Lemos, N.; Cardoso, L.; Geada, J.; ...

2018-02-16

We experimentally demonstrate that plasma waveguides produced with ultra-short laser pulses (sub-picosecond) in gas jets are capable of guiding high intensity laser pulses. This scheme has the unique ability of guiding a high-intensity laser pulse in a plasma waveguide created by the same laser system in the very simple and stable experimental setup. A hot plasma column was created by a femtosecond class laser that expands into an on-axis parabolic low density profile suitable to act as a waveguide for high intensity laser beams. We have successfully guided ~10 15 W cm -2 laser pulses in a 8 mm longmore » hydrogen plasma waveguide with a 35% guiding efficiency.« less

NRL Review 2005. Pioneering the Future

DTIC Science & Technology

2005-01-01

pulse high- intensity lasers —the Table-Top Terawatt (T3) laser and the new Ti:Sapphire Femtosecond Laser (TFL)—to study intense laser -plasma...56 laser beams and is single- pulsed (4-ns pulse ). This facility provides intense radiation for studying inertial confinement fusion (ICF) target... ultrashort - pulse (40 fs), Ti:Sapphire Fem- tosecond Laser (TFL) system is now operational at 1 TW. These lasers comprise a

Method and apparatus for generating high power laser pulses in the two to six micron wavelength range

DOEpatents

MacPherson, David C.; Nelson, Loren D.; O'Brien, Martin J.

1996-01-01

Apparatus performs a method of generating one or more output laser pulses in a range of 2 to 6 microns. When a plurality of the output laser pulses are generated, a first output pulse has any selected wavelength within the range and a second output pulse is temporally closely spaced relative to the first output pulse and has a chosen wavelength differing from the selected wavelength. An oscillator laser cavity is provided with a tunable oscillator rod capable of generating initial laser pulses within a range of from 750 to 1000 nm, and a tuning element is coupled to the rod. A flashlamp is operable to pump the rod. For two pulse operation, the flashlamp has a given duration. A Q-switch provides the initial laser pulses upon operation of the tuning element and the flashlamp. A Raman device coupled to the rod shifts the wavelength of such initial laser pulse into the range of from 2 to 6 microns to form the output laser pulse having a wavelength within the range. For multiple pulses, a controller causes the Q-switch to provide first and second ones of the initial laser pulses, spaced by a time interval less than the given duration. Also, a selector coupled to the tuning element is operable within such duration to successively select the wavelength of the first output pulse and the chosen wavelength of the second initial pulse. The Raman device is responsive to each of the initial light pulses to generate radiation at first and second Stokes wavelengths, each of said the output laser pulses being radiation at the second Stokes wavelength.

Method and apparatus for generating high power laser pulses in the two to six micron wavelength range

DOEpatents

MacPherson, D.C.; Nelson, L.D.; O`Brien, M.J.

1996-12-10

Apparatus performs a method of generating one or more output laser pulses in a range of 2 to 6 microns. When a plurality of the output laser pulses are generated, a first output pulse has any selected wavelength within the range and a second output pulse is temporally closely spaced relative to the first output pulse and has a chosen wavelength differing from the selected wavelength. An oscillator laser cavity is provided with a tunable oscillator rod capable of generating initial laser pulses within a range of from 750 to 1000 nm, and a tuning element is coupled to the rod. A flashlamp is operable to pump the rod. For two pulse operation, the flashlamp has a given duration. A Q-switch provides the initial laser pulses upon operation of the tuning element and the flashlamp. A Raman device coupled to the rod shifts the wavelength of such initial laser pulse into the range of from 2 to 6 microns to form the output laser pulse having a wavelength within the range. For multiple pulses, a controller causes the Q-switch to provide first and second ones of the initial laser pulses, spaced by a time interval less than the given duration. Also, a selector coupled to the tuning element is operable within such duration to successively select the wavelength of the first output pulse and the chosen wavelength of the second initial pulse. The Raman device is responsive to each of the initial light pulses to generate radiation at first and second Stokes wavelengths, each of said the output laser pulses being radiation at the second Stokes wavelength. 30 figs.

2 micron femtosecond fiber laser

DOEpatents

Liu, Jian; Wan, Peng; Yang, Lihmei

2014-07-29

Methods and systems for generating femtosecond fiber laser pulses are disclose, including generating a signal laser pulse from a seed laser oscillator; using a first amplifier stage comprising an input and an output, wherein the signal laser pulse is coupled into the input of the first stage amplifier and the output of the first amplifier stage emits an amplified and stretched signal laser pulse; using an amplifier chain comprising an input and an output, wherein the amplified and stretched signal laser pulse from the output of the first amplifier stage is coupled into the input of the amplifier chain and the output of the amplifier chain emits a further amplified, stretched signal laser pulse. Other embodiments are described and claimed.

Pair Production Induced by Ultrashort and Ultraintense Laser Pulses in Plasmas

NASA Astrophysics Data System (ADS)

Luo, Yue-E.; Wang, Xue-Wen; Wang, Yuan-Sheng; Ji, Shen-Tong; Yu, Hong

2018-06-01

The probability of Schwinger pair production is calculated, which is induced by an ultraintense and ultrashort laser pulse propagating in a plasma. The dependence of the probability on the amplitude of the laser pulse and the frequency of plasmas is analyzed. Particularly, the effect of the pulse duration on the probability is discussed, by introducing a pulse-shape function to describe the temporal shape of the laser pulse. The results show that a laser with shorter pulse is more efficient in pair production. The probability of pair production increases when the order of the duration is comparable to the period of a laser.

Effectiveness of laser sources for contactless sampling of explosives

NASA Astrophysics Data System (ADS)

Akmalov, Artem E.; Chistyakov, Alexander A.; Kotkovskii, Gennadii E.

2016-05-01

A mass-spectrometric study of photo processes initiated by ultraviolet (UV) laser radiation in explosives adsorbed on metal and dielectric substrates has been performed. A calibrated quadrupole mass spectrometer was used to determine a value of activation energy of desorption and a quantity of explosives desorbed by laser radiation. A special vacuumoptical module was elaborated and integrated into a vacuum mass-spectrometric system to focus the laser beam on a sample. It has been shown that the action of nanosecond laser radiation set at q= 107 - 108 W/cm2, λ=266 nm on adsorbed layers of molecules of trinitrotoluene (TNT ) and pentaerytritoltetranitrate (PETN) leads not only to an effective desorption, but also to the non-equilibrium dissociation of molecules with the formation of nitrogen oxide NO. The cyclotrimethylenetrinitramine (RDX) dissociation products are observed only at high laser intensities (q> 109 W/cm2) thus indicating the thermal nature of dissociation, whereas desorption of RDX is observed even at q> 107 W/cm2 from all substrates. Desorption is not observed for cyclotetramethylenetetranitramine (HMX) under single pulse action: the dissociation products NO and NO2 are registered only, whereas irradiation at 10Hz is quite effective for HMX desorption. The results clearly demonstrate a high efficiency of nanosecond laser radiation with λ = 266 nm, q ~ 107 - 108 W/cm2, Epulse= 1mJ for desorption of molecules of explosives from various surfaces.

Laser peening with fiber optic delivery

DOEpatents

Friedman, Herbert W.; Ault, Earl R.; Scheibner, Karl F.

2004-11-16

A system for processing a workpiece using a laser. The laser produces at least one laser pulse. A laser processing unit is used to process the workpiece using the at least one laser pulse. A fiber optic cable is used for transmitting the at least one laser pulse from the laser to the laser processing unit.

Pulse-burst laser systems for fast Thomson scattering (invited)

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

Den Hartog, D. J.; Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, Madison, Wisconsin 53706; Ambuel, J. R.

2010-10-15

Two standard commercial flashlamp-pumped Nd:YAG (YAG denotes yttrium aluminum garnet) lasers have been upgraded to ''pulse-burst'' capability. Each laser produces a burst of up to 15 2 J Q-switched pulses (1064 nm) at repetition rates of 1-12.5 kHz. Variable pulse-width drive (0.15-0.39 ms) of the flashlamps is accomplished by insulated gate bipolar transistor (IGBT) switching of electrolytic capacitor banks. Direct control of the laser Pockels cell drive enables optimal pulse energy extraction, and up to four 2 J laser pulses during one flashlamp pulse. These lasers are used in the Thomson scattering plasma diagnostic system on the MST reversed-field pinchmore » to record the dynamic evolution of the electron temperature profile and temperature fluctuations. To further these investigations, a custom pulse-burst laser system with a maximum pulse repetition rate of 250 kHz is now being commissioned.« less

Femtosecond Fiber Lasers Based on Dissipative Processes for Nonlinear Microscopy.

PubMed

Wise, Frank W

2012-01-01

Recent progress in the development of femtosecond-pulse fiber lasers with parameters appropriate for nonlinear microscopy is reviewed. Pulse-shaping in lasers with only normal-dispersion components is briefly described, and the performance of the resulting lasers is summarized. Fiber lasers based on the formation of dissipative solitons now offer performance competitive with that of solid-state lasers, but with the benefits of the fiber medium. Lasers based on self-similar pulse evolution in the gain section of a laser also offer a combination of short pulse duration and high pulse energy that will be attractive for applications in nonlinear bioimaging.

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.

Dual-pulse laser ignition of ethylene-air mixtures in a supersonic combustor.

PubMed

Yang, Leichao; An, Bin; Liang, Jianhan; Li, Xipeng; Wang, Zhenguo

2018-04-02

To reduce the energy of an individual laser pulse, dual-pulse laser ignitions (LIs) at various pulse intervals were investigated in a Mach 2.92 scramjet engine fueled with ethylene. For comparison, experiments on a single-pulse LI were also performed. Schlieren visualization and high-speed photography were employed to observe the ignition processes simultaneously. The results indicate that the energy of an individual laser pulse can be reduced by half via a dual-pulse LI method as compared with a single-pulse LI with the same total energy. The reduction of the individual laser pulse energy degrades the requirements on the laser source and the beam delivery system, which facilitates the practical application of LI in hypersonic vehicles. A pulse interval shorter than 40 μs is suggested for dual-pulse LI in the present study. Because of the intense heat loss and radical dissipation in high-speed flows, the pulse interval for dual-pulse LI should be short enough to narrow the spatial distribution of the initial flame kernel.

Ablation of film stacks in solar cell fabrication processes

DOEpatents

Harley, Gabriel; Kim, Taeseok; Cousins, Peter John

2013-04-02

A dielectric film stack of a solar cell is ablated using a laser. The dielectric film stack includes a layer that is absorptive in a wavelength of operation of the laser source. The laser source, which fires laser pulses at a pulse repetition rate, is configured to ablate the film stack to expose an underlying layer of material. The laser source may be configured to fire a burst of two laser pulses or a single temporally asymmetric laser pulse within a single pulse repetition to achieve complete ablation in a single step.

High-speed multi-frame dynamic transmission electron microscope image acquisition system with arbitrary timing

DOEpatents

Reed, Bryan W.; DeHope, William J.; Huete, Glenn; LaGrange, Thomas B.; Shuttlesworth, Richard M.

2016-02-23

An electron microscope is disclosed which has a laser-driven photocathode and an arbitrary waveform generator (AWG) laser system ("laser"). The laser produces a train of temporally-shaped laser pulses each being of a programmable pulse duration, and directs the laser pulses to the laser-driven photocathode to produce a train of electron pulses. An image sensor is used along with a deflector subsystem. The deflector subsystem is arranged downstream of the target but upstream of the image sensor, and has a plurality of plates. A control system having a digital sequencer controls the laser and a plurality of switching components, synchronized with the laser, to independently control excitation of each one of the deflector plates. This allows each electron pulse to be directed to a different portion of the image sensor, as well as to enable programmable pulse durations and programmable inter-pulse spacings.

Ultrashort laser pulses and electromagnetic pulse generation in air and on dielectric surfaces.

PubMed

Sprangle, P; Peñano, J R; Hafizi, B; Kapetanakos, C A

2004-06-01

Intense, ultrashort laser pulses propagating in the atmosphere have been observed to emit sub-THz electromagnetic pulses (EMPS). The purpose of this paper is to analyze EMP generation from the interaction of ultrashort laser pulses with air and with dielectric surfaces and to determine the efficiency of conversion of laser energy to EMP energy. In our self-consistent model the laser pulse partially ionizes the medium, forms a plasma filament, and through the ponderomotive forces associated with the laser pulse, drives plasma currents which are the source of the EMP. The propagating laser pulse evolves under the influence of diffraction, Kerr focusing, plasma defocusing, and energy depletion due to electron collisions and ionization. Collective effects and recombination processes are also included in the model. The duration of the EMP in air, at a fixed point, is found to be a few hundred femtoseconds, i.e., on the order of the laser pulse duration plus the electron collision time. For steady state laser pulse propagation the flux of EMP energy is nonradiative and axially directed. Radiative EMP energy is present only for nonsteady state or transient laser pulse propagation. The analysis also considers the generation of EMP on the surface of a dielectric on which an ultrashort laser pulse is incident. For typical laser parameters, the power and energy conversion efficiency from laser radiation to EMP radiation in both air and from dielectric surfaces is found to be extremely small, < 10(-8). Results of full-scale, self-consistent, numerical simulations of atmospheric and dielectric surface EMP generation are presented. A recent experiment on atmospheric EMP generation is also simulated.

Invited Article: High resolution angle resolved photoemission with tabletop 11 eV laser

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

He, Yu; Vishik, Inna M.; Yi, Ming

2016-01-15

We developed a table-top vacuum ultraviolet (VUV) laser with 113.778 nm wavelength (10.897 eV) and demonstrated its viability as a photon source for high resolution angle-resolved photoemission spectroscopy (ARPES). This sub-nanosecond pulsed VUV laser operates at a repetition rate of 10 MHz, provides a flux of 2 × 10{sup 12} photons/s, and enables photoemission with energy and momentum resolutions better than 2 meV and 0.012 Å{sup −1}, respectively. Space-charge induced energy shifts and spectral broadenings can be reduced below 2 meV. The setup reaches electron momenta up to 1.2 Å{sup −1}, granting full access to the first Brillouin zone ofmore » most materials. Control over the linear polarization, repetition rate, and photon flux of the VUV source facilitates ARPES investigations of a broad range of quantum materials, bridging the application gap between contemporary low energy laser-based ARPES and synchrotron-based ARPES. We describe the principles and operational characteristics of this source and showcase its performance for rare earth metal tritellurides, high temperature cuprate superconductors, and iron-based superconductors.« less

The national ignition facility: Path to ignition in the laboratory

NASA Astrophysics Data System (ADS)

Moses, E. I.; Bonanno, R. E.; Haynam, C. A.; Kauffman, R. L.; MacGowan, B. J.; Patterson, R. W., Jr.; Sawicki, R. H.; van Wonterghem, B. M.

2006-06-01

The National Ignition Facility (NIF) is a 192-beam laser facility presently under construction at LLNL. When completed, NIF will be a 1.8-MJ, 500-TW ultraviolet laser system. Its missions are to obtain fusion ignition and to perform high energy density experiments in support of the U.S. nuclear weapons stockpile. Four of the NIF beams have been commissioned to demonstrate laser performance and to commission the target area including target and beam alignment and laser timing. During this time, NIF demonstrated on a single-beam basis that it will meet its performance goals and demonstrated its precision and flexibility for pulse shaping, pointing, timing and beam conditioning. It also performed four important experiments for Inertial Confinement Fusion and High Energy Density Science. Presently, the project is installing production hardware to complete the project in 2009 with the goal to begin ignition experiments in 2010. An integrated plan has been developed including the NIF operations, user equipment such as diagnostics and cryogenic target capability, and experiments and calculations to meet this goal. This talk will provide NIF status, the plan to complete NIF, and the path to ignition.

Kr photoionized plasma induced by intense extreme ultraviolet pulses

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

Bartnik, A., E-mail: andrzej.bartnik@wat.edu.pl; Wachulak, P.; Fiedorowicz, H.

Irradiation of any gas with an intense EUV (extreme ultraviolet) radiation beam can result in creation of photoionized plasmas. The parameters of such plasmas can be significantly different when compared with those of the laser produced plasmas (LPP) or discharge plasmas. In this work, the photoionized plasmas were created in a krypton gas irradiated using an LPP EUV source operating at a 10 Hz repetition rate. The Kr gas was injected into the vacuum chamber synchronously with the EUV radiation pulses. The EUV beam was focused onto a Kr gas stream using an axisymmetrical ellipsoidal collector. The resulting low temperature Krmore » plasmas emitted electromagnetic radiation in the wide spectral range. The emission spectra were measured either in the EUV or an optical range. The EUV spectrum was dominated by emission lines originating from Kr III and Kr IV ions, and the UV/VIS spectra were composed from Kr II and Kr I lines. The spectral lines recorded in EUV, UV, and VIS ranges were used for the construction of Boltzmann plots to be used for the estimation of the electron temperature. It was shown that for the lowest Kr III and Kr IV levels, the local thermodynamic equilibrium (LTE) conditions were not fulfilled. The electron temperature was thus estimated based on Kr II and Kr I species where the partial LTE conditions could be expected.« less

Kr photoionized plasma induced by intense extreme ultraviolet pulses

NASA Astrophysics Data System (ADS)

Bartnik, A.; Wachulak, P.; Fiedorowicz, H.; Skrzeczanowski, W.

2016-04-01

Irradiation of any gas with an intense EUV (extreme ultraviolet) radiation beam can result in creation of photoionized plasmas. The parameters of such plasmas can be significantly different when compared with those of the laser produced plasmas (LPP) or discharge plasmas. In this work, the photoionized plasmas were created in a krypton gas irradiated using an LPP EUV source operating at a 10 Hz repetition rate. The Kr gas was injected into the vacuum chamber synchronously with the EUV radiation pulses. The EUV beam was focused onto a Kr gas stream using an axisymmetrical ellipsoidal collector. The resulting low temperature Kr plasmas emitted electromagnetic radiation in the wide spectral range. The emission spectra were measured either in the EUV or an optical range. The EUV spectrum was dominated by emission lines originating from Kr III and Kr IV ions, and the UV/VIS spectra were composed from Kr II and Kr I lines. The spectral lines recorded in EUV, UV, and VIS ranges were used for the construction of Boltzmann plots to be used for the estimation of the electron temperature. It was shown that for the lowest Kr III and Kr IV levels, the local thermodynamic equilibrium (LTE) conditions were not fulfilled. The electron temperature was thus estimated based on Kr II and Kr I species where the partial LTE conditions could be expected.

Laser one-dimensional range profile and the laser two-dimensional range profile of cylinders

NASA Astrophysics Data System (ADS)

Gong, Yanjun; Wang, Mingjun; Gong, Lei

2015-10-01

Laser one-dimensional range profile, that is scattering power from pulse laser scattering of target, is a radar imaging technology. The laser two-dimensional range profile is two-dimensional scattering imaging of pulse laser of target. Laser one-dimensional range profile and laser two-dimensional range profile are called laser range profile(LRP). The laser range profile can reflect the characteristics of the target shape and surface material. These techniques were motivated by applications of laser radar to target discrimination in ballistic missile defense. The radar equation of pulse laser is given in this paper. This paper demonstrates the analytical model of laser range profile of cylinder based on the radar equation of the pulse laser. Simulations results of laser one-dimensional range profiles of some cylinders are given. Laser range profiles of cylinder, whose surface material with diffuse lambertian reflectance, is given in this paper. Laser range profiles of different pulse width of cylinder are given in this paper. The influences of geometric parameters, pulse width, attitude on the range profiles are analyzed.

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

Multiwavelength self-pulsating fibre laser based on cascaded SPM spectral broadening and filtering

NASA Astrophysics Data System (ADS)

Rochette, Martin; Sun, Kai; Hernández-Cordero, Juan; Chen, Lawrence R.

2008-06-01

We experimentally demonstrate the operation of a laser based on self-phase modulation followed by offset spectral filtering. This laser has three operation modes: a continuous-wave mode, a self-pulsating mode where the laser self ignites and produces pulses, and a pulse-buffering mode where no new pulse is formed from spontaneous emission noise but only pulses already propagating or pulses injected in the laser cavity can be sustained. In the self-pulsating and pulse-buffering modes, the laser is multi-wavelength and continuously tunable over the entire gain band of the amplifiers. The output pulse width is quasi transform-limited with respect to the spectral-width of the filters used in the cavity. Overall, this device provides a simple alternative to pulsed laser source and also represents a promising approach for signal buffering.

Laser beam pulse formatting method

DOEpatents

Daly, T.P.; Moses, E.I.; Patterson, R.W.; Sawicki, R.H.

1994-08-09

A method for formatting a laser beam pulse using one or more delay loops is disclosed. The delay loops have a partially reflective beam splitter and a plurality of highly reflective mirrors arranged such that the laser beam pulse enters into the delay loop through the beam splitter and circulates therein along a delay loop length defined by the mirrors. As the laser beam pulse circulates within the delay loop a portion thereof is emitted upon each completed circuit when the laser beam pulse strikes the beam splitter. The laser beam pulse is thereby formatted into a plurality of sub-pulses. The delay loops are used in combination to produce complex waveforms by combining the sub-pulses using additive waveform synthesis. 8 figs.

Pulse-analysis-pulse investigation of femtosecond laser-induced periodic surface structures on silicon in air.

PubMed

Oboňa, J Vincenc; Skolski, J Z P; Römer, G R B E; in t Veld, A J Huis

2014-04-21

A new approach to experimentally investigate laser-induced periodic surface structures (LIPSSs) is introduced. Silicon was iteratively exposed to femtosecond laser pulses at λ = 800 nm and normal incidence in ambient air and at a fluence slightly over the single-pulse modification threshold. After each laser pulse, the topography of the surface was inspected by confocal microscopy. Subsequently, the sample was reproducibly repositioned in the laser setup, to be exposed to the next laser pulse. By this approach, the initiation and spatial evolution ("growth") of the LIPSSs were analyzed as function of the number of pulses applied. It was found that, after the first laser pulses, the ridges of the LIPSSs elevate, and valleys between the ridges deepen, by a few tens of nanometers relative to the initial surface. An electromagnetic model, discussed in earlier works, predicted that the spatial periodicity of LIPSSs decreases with the number of laser pulses applied. This implies material transport and reorganization of the irradiated material on the surface, due to each laser pulse. However, our experiments show a negligible shift of the lateral positions of the LIPSSs on the surface.