Generation of ultrashort pulses with minimum duration of 90\\ {\\text{fs}} in a hybrid mode-locked erbium-doped all-fibre ring laser

NASA Astrophysics Data System (ADS)

Dvoretskiy, D. A.; Sazonkin, S. G.; Voropaev, V. S.; Negin, M. A.; Leonov, S. O.; Pnev, A. B.; Karasik, V. E.; Denisov, L. K.; Krylov, A. A.; Davydov, V. A.; Obraztsova, E. D.

2016-11-01

Regimes of ultrashort pulse generation in an erbium-doped all-fibre ring laser with hybrid mode locking based on single-wall carbon - boron nitride nanotubes and the nonlinear Kerr effect in fibre waveguides are studied. Stable dechirped ultrashort pulses are obtained with a duration of ˜ 90 {\\text{fs}}, a repetition rate of ˜ 42.2 {\\text{MHz}}, and an average output power of ˜ 16.7 {\\text{mW}}, which corresponds to a pulse energy of ˜ 0.4 {\\text{nJ}} and a peak laser power of ˜ 4.4 {\\text{kW}}.

Femtosecond (191 fs) NaY(WO4)2 Tm,Ho-codoped laser at 2060 nm.

PubMed

Lagatsky, A A; Han, X; Serrano, M D; Cascales, C; Zaldo, C; Calvez, S; Dawson, M D; Gupta, J A; Brown, C T A; Sibbett, W

2010-09-15

We report, for the first time to our knowledge, femtosecond-pulse operation of a Tm,Ho:NaY(WO(4))(2) laser at around 2060 nm. Transform-limited 191 fs pulses are produced with an average output power of 82 mW at a 144 MHz pulse repetition frequency. Maximum output power of up to 155 mW is generated with a corresponding pulse duration of 258 fs. An ion-implanted InGaAsSb quantum-well-based semiconductor saturable absorber mirror is used for passive mode-locking maintenance.

Broadly tunable femtosecond mode-locking in a Tm:KYW laser near 2 μm.

PubMed

Lagatsky, A A; Calvez, S; Gupta, J A; Kisel, V E; Kuleshov, N V; Brown, C T A; Dawson, M D; Sibbett, W

2011-05-09

Efficient mode-locking in a Tm:KY(WO(4))(2) laser is demonstrated by using InGaAsSb quantum-well SESAMs. Self-starting ultrashort pulse generation was realized in the 1979-2074 nm spectral region. Maximum average output power up to 411 mW was produced around 1986 nm with the corresponding pulse duration and repetition rate of 549 fs and 105 MHz respectively. Optimised pulse durations of 386 fs were produced with an average power of 235 mW at 2029 nm. © 2011 Optical Society of America

Strong electromagnetic pulses generated in high-intensity laser-matter interactions

NASA Astrophysics Data System (ADS)

Rączka, P.; Dubois, J.-L.; Hulin, S.; Rosiński, M.; Zaraś-Szydłowska, A.; Badziak, J.

2018-01-01

Results are reported of an experiment performed at the Eclipse laser facility in CELIA, Bordeaux, on the generation of strong electromagnetic pulses. Measurements were performed of the target neutralization current, the total target charge and the tangential component of the magnetic field for the laser energies ranging from 45 mJ to 92 mJ with the pulse duration approximately 40 fs, and for the pulse durations ranging from 39 fs to 1000 fs, with the laser energy approximately 90 mJ. It was found that the values obtained for thick (mm scale) Cu targets are visibly higher than values reported in previous experiments, which is argued to be a manifestation of a strong dependence of the target electric polarization process on the laser contrast and hence on the amount of preplasma. It was also found that values obtained for thin (μm scale) Al foils were visibly higher than values for thick Cu targets, especially for pulse durations longer than 100 fs. The correlations between the total target charge versus the maximum value of the target neutralization current, and the maximum value of the tangential component of the magnetic field versus the total target charge were analysed. They were found to be in very good agreement with correlations seen in data from previous experiments, which provides a good consistency check on our experimental procedures.

Time- and frequency-dependent model of time-resolved coherent anti-Stokes Raman scattering (CARS) with a picosecond-duration probe pulse

NASA Astrophysics Data System (ADS)

Stauffer, Hans U.; Miller, Joseph D.; Slipchenko, Mikhail N.; Meyer, Terrence R.; Prince, Benjamin D.; Roy, Sukesh; Gord, James R.

2014-01-01

The hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) technique presents a promising alternative to either fs time-resolved or ps frequency-resolved CARS in both gas-phase thermometry and condensed-phase excited-state dynamics applications. A theoretical description of time-dependent CARS is used to examine this recently developed probe technique, and quantitative comparisons of the full time-frequency evolution show excellent accuracy in predicting the experimental vibrational CARS spectra obtained for two model systems. The interrelated time- and frequency-domain spectral signatures of gas-phase species produced by hybrid fs/ps CARS are explored with a focus on gas-phase N2 vibrational CARS, which is commonly used as a thermometric diagnostic of combusting flows. In particular, we discuss the merits of the simple top-hat spectral filter typically used to generate the ps-duration hybrid fs/ps CARS probe pulse, including strong discrimination against non-resonant background that often contaminates CARS signal. It is further demonstrated, via comparison with vibrational CARS results on a time-evolving solvated organic chromophore, that this top-hat probe-pulse configuration can provide improved spectral resolution, although the degree of improvement depends on the dephasing timescales of the observed molecular modes and the duration and timing of the narrowband final pulse. Additionally, we discuss the virtues of a frequency-domain Lorentzian probe-pulse lineshape and its potential for improving the hybrid fs/ps CARS technique as a diagnostic in high-pressure gas-phase thermometry applications.

A table-top monochromator for tunable femtosecond XUV pulses generated in a semi-infinite gas cell: Experiment and simulations

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

Conta, A. von; Huppert, M.; Wörner, H. J.

2016-07-15

We present a new design of a time-preserving extreme-ultraviolet (XUV) monochromator using a semi-infinite gas cell as a source. The performance of this beamline in the photon-energy range of 20 eV–42 eV has been characterized. We have measured the order-dependent XUV pulse durations as well as the flux and the spectral contrast. XUV pulse durations of ≤40 fs using 32 fs, 800 nm driving pulses were measured on the target. The spectral contrast was better than 100 over the entire energy range. A simple model based on the strong-field approximation is presented to estimate different contributions to the measured XUVmore » pulse duration. On-axis phase-matching calculations are used to rationalize the variation of the photon flux with pressure and intensity.« less

Theoretical exploration of control factors for the high-order harmonic generation (HHG) spectrum in two-color field.

PubMed

Huang, Xinting; Yang, Dapeng; Yao, Li

2014-09-15

In this work, the laser-parameter effects on the high-order harmonic generation (HHG) spectrum and attosecond trains by mixing two-color laser field, a visible light field of 800 nm and a mid-infrared (mid-IR) laser pulses of 2400 nm, are theoretically demonstrated for the first time. Different schemes are applied to discuss the function of intensity, carrier-envelope phase (CEP) and pulse duration on the generation of an isolated attosecond pulse. As a consequence, an isolated 16as pulse is obtained by Fourier transforming an ultrabroad XUV continuum of 208 eV with the fundamental field of duration of 6 fs, 9×10(14)W/cm2 of intensity, the duration of 12 fs, the CEPs of the two driving pulses of -π and the relative strength ratio √R=0.2. Copyright © 2014 Elsevier B.V. All rights reserved.

152 fs nanotube-mode-locked thulium-doped all-fiber laser

PubMed Central

Wang, Jinzhang; Liang, Xiaoyan; Hu, Guohua; Zheng, Zhijian; Lin, Shenghua; Ouyang, Deqin; Wu, Xu; Yan, Peiguang; Ruan, Shuangchen; Sun, Zhipei; Hasan, Tawfique

2016-01-01

Ultrafast fiber lasers with broad bandwidth and short pulse duration have a variety of applications, such as ultrafast time-resolved spectroscopy and supercontinuum generation. We report a simple and compact all-fiber thulium-doped femtosecond laser mode-locked by carbon nanotubes. The oscillator operates in slightly normal cavity dispersion at 0.055 ps2, and delivers 152 fs pulses with 52.8 nm bandwidth and 0.19 nJ pulse energy. This is the shortest pulse duration and the widest spectral width demonstrated from Tm-doped all-fiber lasers based on 1 or 2 dimensional nanomaterials, underscoring their growing potential as versatile saturable absorber materials. PMID:27374764

Nonlinear side effects of fs pulses inside corneal tissue during photodisruption

NASA Astrophysics Data System (ADS)

Heisterkamp, A.; Ripken, T.; Mamom, T.; Drommer, W.; Welling, H.; Ertmer, W.; Lubatschowski, H.

In order to evaluate the potential for refractive surgery, fs laser pulses of 150-fs pulse duration were used to process corneal tissue of dead and living animal eyes. By focusing the laser radiation down to spot sizes of several microns, very precise cuts could be achieved inside the treated cornea, accompanied with minimum collateral damage to the tissue by thermal or mechanical effects. During histo-pathological analysis by light and transmission electron microscopy considerable side effects of fs photodisruption were found. Due to the high intensities at the focal region several nonlinear effects occurred. Self-focusing, photodissociation, UV-light production were observed, leading to streak formation inside the cornea.

Kilohertz Cr:forsterite regenerative amplifier.

PubMed

Evans, J M; Petri Evi, V; Alfano, R R; Fu, Q

1998-11-01

We report on a tunable regenerative amplifier that is operational in the near-infrared spectral region from 1230 to 1280 nm based on the vibronic laser material Cr:forsterite. Utilizing the technique of chirped-pulse amplification, we generated pulses as short as 150 fs at 1255 nm at a repetition rate of 1 kHz. Pulse amplification of more than 5 x 10(5) times was observed, with recorded output pulse energies of 34 muJ . Implementation of a second-harmonic generator yielded 110-fs-duration pulses of 7-muJ energy at 625 nm.

Nuclear interference in the Coulomb explosion of H2+ in short vuv laser fields.

PubMed

Førre, Morten; Barmaki, Samira; Bachau, Henri

2009-03-27

We report ab initio calculations of H2+ three-photon ionization by vuv/fs 10(12) W/cm(2) laser pulses including electronic and vibrational degrees of freedom in the Born-Oppenheimer approximation. The initial nuclear wave packet of H2+(1ssigma(g)) is assumed to be equal to the H2 vibrational ground state. For pulse durations longer than 10 fs, we find an unexpected modulation in the kinetic energy spectra of the correlated fragments (H++H+). It is shown that the structures in the spectra originate from the interference between a direct and a sequential dissociation channel. While the first channel is open even for relatively short pulses, the sequential one only opens for pulse durations longer than 10 fs. In the latter case we show that interference between the two components results in a modulated kinetic energy release spectrum in the dissociation channel 3dsigma(g), which is reflected in the ionization spectrum.

Comparison of chirped-probe-pulse and hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering for combustion thermometry.

PubMed

Richardson, Daniel R; Stauffer, Hans U; Roy, Sukesh; Gord, James R

2017-04-10

A comparison is made between two ultrashort-pulse coherent anti-Stokes Raman scattering (CARS) thermometry techniques-hybrid femtosecond/picosecond (fs/ps) CARS and chirped-probe-pulse (CPP) fs-CARS-that have become standards for high-repetition-rate thermometry in the combustion diagnostics community. These two variants of fs-CARS differ only in the characteristics of the ps-duration probe pulse; in hybrid fs/ps CARS a spectrally narrow, time-asymmetric probe pulse is used, whereas a highly chirped, spectrally broad probe pulse is used in CPP fs-CARS. Temperature measurements were performed using both techniques in near-adiabatic flames in the temperature range 1600-2400 K and for probe time delays of 0-30 ps. Under these conditions, both techniques are shown to exhibit similar temperature measurement accuracies and precisions to previously reported values and to each other. However, it is observed that initial calibration fits to the spectrally broad CPP results require more fitting parameters and a more robust optimization algorithm and therefore significantly increased computational cost and complexity compared to the fitting of hybrid fs/ps CARS data. The optimized model parameters varied more for the CPP measurements than for the hybrid fs/ps measurements for different experimental conditions.

Commercial mode-locked vertical external cavity surface emitting lasers

NASA Astrophysics Data System (ADS)

Lubeigt, Walter; Bialkowski, Bartlomiej; Lin, Jipeng; Head, C. Robin; Hempler, Nils; Maker, Gareth T.; Malcolm, Graeme P. A.

2017-02-01

In recent years, M Squared Lasers have successfully commercialized a range of mode-locked vertical external cavity surface emitting lasers (VECSELs) operating between 920-1050nm and producing picosecond-range pulses with average powers above 1W at pulse repetition frequencies (PRF) of 200MHz. These laser products offer a low-cost, easy-to-use and maintenance-free tool for the growing market of nonlinear microscopy. However, in order to present a credible alternative to ultrafast Ti-sapphire lasers, pulse durations below 200fs are required. In the last year, efforts have been directed to reduce the pulse duration of the Dragonfly laser system to below 200fs with a target average power above 1W at a PRF of 200MHz. This paper will describe and discuss the latest efforts undertaken to approach these targets in a laser system operating at 990nm. The relatively low PRF operation of Dragonfly lasers represents a challenging requirement for mode-locked VECSELs due to the very short upper state carrier lifetime, on the order of a few nanoseconds, which can lead to double pulsing behavior in longer cavities as the time between consecutive pulses is increased. Most notably, the design of the Dragonfly VECSEL cavity was considerably modified and the laser system extended with a nonlinear pulse stretcher and an additional compression stage. The improved Dragonfly laser system achieved pulse duration as short as 130fs with an average power of 0.85W.

Three-photon excitation source at 1250 nm generated in a dual zero dispersion wavelength nonlinear fiber

DOE PAGES

Domingue, Scott R.; Bartels, Randy A.

2014-12-04

Here, we demonstrate 1250 nm pulses generated in dual-zero dispersion photonic crystal fiber capable of three-photon excitation fluorescence microscopy. The total power conversion efficiency from the 28 fs seed pulse centered at 1075 nm to pulses at 1250 nm, including coupling losses from the nonlinear fiber, is 35%, with up to 67% power conversion efficiency of the fiber coupled light. Frequency-resolved optical gating measurements characterize 1250 nm pulses at 0.6 nJ and 2 nJ, illustrating the change in nonlinear spectral phase accumulation with pulse energy even for nonlinear fiber lengths < 50 mm. The 0.6 nJ pulse has a 26more » fs duration and is the shortest nonlinear fiber derived 1250 nm pulse yet reported (to the best of our knowledge). The short pulse durations and energies make these pulses a viable route to producing light at 1250 nm for multiphoton microscopy, which we we demonstrate here, via a three-photon excitation fluorescence microscope.« less

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Ultrafast control of strong light-matter coupling

NASA Astrophysics Data System (ADS)

Lange, Christoph; Cancellieri, Emiliano; Panna, Dmitry; Whittaker, David M.; Steger, Mark; Snoke, David W.; Pfeiffer, Loren N.; West, Kenneth W.; Hayat, Alex

2018-01-01

We dynamically modulate strong light-matter coupling in a GaAs/AlGaAs microcavity using intense ultrashort laser pulses tuned below the interband exciton energy, which induce a transient Stark shift of the cavity polaritons. For 225-fs pulses, shorter than the cavity Rabi cycle period of 1000 fs, this shift decouples excitons and cavity photons for the duration of the pulse, interrupting the periodic energy exchange between photonic and electronic states. For 1500-fs pulses, longer than the Rabi cycle period, however, the Stark shift does not affect the strong coupling. The two regimes are marked by distinctly different line shapes in ultrafast reflectivity measurements—regardless of the Stark field intensity. The crossover marks the transition from adiabatic to diabatic switching of strong light-matter coupling.

500 MW peak power degenerated optical parametric amplifier delivering 52 fs pulses at 97 kHz repetition rate.

PubMed

Rothhardt, J; Hädrich, S; Röser, F; Limpert, J; Tünnermann, A

2008-06-09

We present a high peak power degenerated parametric amplifier operating at 1030 nm and 97 kHz repetition rate. Pulses of a state-of-the art fiber chirped-pulse amplification (FCPA) system with 840 fs pulse duration and 410 microJ pulse energy are used as pump and seed source for a two stage optical parametric amplifier. Additional spectral broadening of the seed signal in a photonic crystal fiber creates enough bandwidth for ultrashort pulse generation. Subsequent amplification of the broadband seed signal in two 1 mm BBO crystals results in 41 microJ output pulse energy. Compression in a SF 11 prism compressor yields 37 microJ pulses as short as 52 fs. Thus, pulse shortening of more than one order of magnitude is achieved. Further scaling in terms of average power and pulse energy seems possible and will be discussed, since both concepts involved, the fiber laser and the parametric amplifier have the reputation to be immune against thermo-optical effects.

Atomistic simulations of ultra-short pulse laser ablation of aluminum: validity of the Lambert-Beer law

NASA Astrophysics Data System (ADS)

Eisfeld, Eugen; Roth, Johannes

2018-05-01

Based on hybrid molecular dynamics/two-temperature simulations, we study the validity of the application of Lambert-Beer's law, which is conveniently used in various modeling approaches of ultra-short pulse laser ablation of metals. The method is compared to a more rigorous treatment, which involves solving the Helmholtz wave equation for different pulse durations ranging from 100 fs to 5 ps and a wavelength of 800 nm. Our simulations show a growing agreement with increasing pulse durations, and we provide appropriate optical parameters for all investigated pulse durations.

Generation and subsequent amplification of few-cycle femtosecond pulses from a picosecond pump laser

NASA Astrophysics Data System (ADS)

Mukhin, I. B.; Kuznetsov, I. I.; Palashov, O. V.

2018-04-01

Using a new approach, in which generation of femtosecond pulses as short as a few field cycles is implemented directly from the radiation of a picosecond pump laser, pulses with the microjoule energy, the repetition rate 10 kHz, and the duration less than 26 fs are generated in the spectral range 1.3 ‑ 1.4 μm. In the process of generating this radiation, use was made of a method providing passive phase stabilisation of the carrier oscillation of the electromagnetic field and its slow envelope. The radiation spectrum was converted into the range of parametric amplification in the BBO crystal by the broadband second harmonic generation; the pulse was parametrically amplified up to the microjoule level and compressed by chirped mirrors to a duration of 28 fs.

Single shot speckle and coherence analysis of the hard X-ray free electron laser LCLS

DOE PAGES

Lee, Sooheyong; Roseker, W.; Gutt, C.; ...

2013-10-08

The single shot based coherence properties of hard x-ray pulses from the Linac Coherent Light Source (LCLS) were measured by analyzing coherent diffraction patterns from nano-particles and gold nanopowder. The intensity histogram of the small angle x-ray scattering ring from nano-particles reveals the fully transversely coherent nature of the LCLS beam with a number of transverse modemore » $$\\langle$$M s$$\\rangle$$ = 1.1. On the other hand, the speckle contrasts measured at a large wavevector yields information about the longitudinal coherence of the LCLS radiation after a silicon (111) monochromator. The quantitative agreement between our data and the simulation confirms a mean coherence time of 2.2 fs and a x-ray pulse duration of 29 fs. Lastly the observed reduction of the speckle contrast generated by x-rays with pulse duration longer than 30 fs indicates ultrafast dynamics taking place at an atomic length scale prior to the permanent sample damage.« less

Compact fiber CPA system based on a CFBG stretcher and CVBG compressor with matched dispersion profile.

PubMed

Bartulevicius, Tadas; Frankinas, Saulius; Michailovas, Andrejus; Vasilyeu, Ruslan; Smirnov, Vadim; Trepanier, Francois; Rusteika, Nerijus

2017-08-21

In this work, a compact fiber chirped pulse amplification system exploiting a tandem of a chirped fiber Bragg grating stretcher and a chirped volume Bragg grating compressor with matched chromatic dispersion is presented. Chirped pulses of 230 ps duration were amplified in a Yb-doped fiber amplifier and re-compressed to 208 fs duration with good fidelity. The compressed pulse duration was fine-tuned by temperature gradient along the fiber Bragg grating stretcher.

Low-loss flake-graphene saturable absorber mirror for laser mode-locking at sub-200-fs pulse duration

NASA Astrophysics Data System (ADS)

Cunning, B. V.; Brown, C. L.; Kielpinski, D.

2011-12-01

Saturable absorbers are a key component for mode-locking femtosecond lasers. Polymer films containing graphene flakes have recently been used in transmission as laser mode-lockers but suffer from high nonsaturable loss, limiting their application in low-gain lasers. Here, we present a saturable absorber mirror based on a film of pure graphene flakes. The device is used to mode lock an erbium-doped fiber laser, generating pulses with state-of-the-art, sub-200-fs duration. The laser characteristic indicates that the film exhibits low nonsaturable loss (13% per pass) and large absorption modulation depth (45% of low-power absorption).

Two-Photon Excited Fluorescence from Biological Aerosol Particles

DTIC Science & Technology

2010-09-29

in material damage. We overcame these limitations by building a band-limited Yb-doped fiber laser with no dispersion compensation [9], as the master...master oscillator was an all-normal- dispersion Yb-doped fiber laser [9], followed by high- dispersion fiber for stretching the pulses, a single-mode...of ~670 fs in duration, and its expected transform-limited pulse width for a normal- dispersion laser with this spectral width would be ~454 fs [10

Optical pulse compression in dispersion decreasing photonic crystal fiber.

PubMed

Travers, J C; Stone, J M; Rulkov, A B; Cumberland, B A; George, A K; Popov, S V; Knight, J C; Taylor, J R

2007-10-01

Improvements to tapered photonic crystal fiber (PCF) fabrication have allowed us to make up to 50 m long PCF tapers with loss as low as 30 dB/km. We discuss the design constraints for tapered PCFs used for adiabatic soliton compression and demonstrate over 15 times compression of pulses from over 830 fs to 55 fs duration at a wavelength of 1.06 lm, an order of magnitude improvement over previous results.

Wavelength and pulse duration tunable ultrafast fiber laser mode-locked with carbon nanotubes.

PubMed

Li, Diao; Jussila, Henri; Wang, Yadong; Hu, Guohua; Albrow-Owen, Tom; C T Howe, Richard; Ren, Zhaoyu; Bai, Jintao; Hasan, Tawfique; Sun, Zhipei

2018-02-09

Ultrafast lasers with tunable parameters in wavelength and time domains are the choice of light source for various applications such as spectroscopy and communication. Here, we report a wavelength and pulse-duration tunable mode-locked Erbium doped fiber laser with single wall carbon nanotube-based saturable absorber. An intra-cavity tunable filter is employed to continuously tune the output wavelength for 34 nm (from 1525 nm to 1559 nm) and pulse duration from 545 fs to 6.1 ps, respectively. Our results provide a novel light source for various applications requiring variable wavelength or pulse duration.

Generation of high-energy sub-20 fs pulses tunable in the 250-310 nm region by frequency doubling of a high-power noncollinear optical parametric amplifier.

PubMed

Beutler, Marcus; Ghotbi, Masood; Noack, Frank; Brida, Daniele; Manzoni, Cristian; Cerullo, Giulio

2009-03-15

We report on the generation of powerful sub-20 fs deep UV pulses with 10 microJ level energy and broadly tunable in the 250-310 nm range. These pulses are produced by frequency doubling a high-power noncollinear optical parametric amplifier and compressed by a pair of MgF2 prisms to an almost transform-limited duration. Our results provide a power scaling by an order of magnitude with respect to previous works.

An investigation on 800 nm femtosecond laser ablation of K9 glass in air and vacuum

NASA Astrophysics Data System (ADS)

Xu, Shi-zhen; Yao, Cai-zhen; Dou, Hong-qiang; Liao, Wei; Li, Xiao-yang; Ding, Ren-jie; Zhang, Li-juan; Liu, Hao; Yuan, Xiao-dong; Zu, Xiao-tao

2017-06-01

Ablation rates of K9 glass were studied as a function of femtosecond laser fluences. The central wavelength was 800 nm, and pulse durations of 35 fs and 500 fs in air and vacuum were employed. Ablation thresholds of 0.42 J/cm2 and 2.1 J/cm2 were obtained at 35 fs and 500 fs, respectively, which were independent with the ambient conditions and depend on the incident pulse numbers due to incubation effects. The ablation rate of 35 fs pulse laser increased with the increasing of laser fluence in vacuum, while in air condition, it slowly increased to a plateau at high fluence. The ablation rate of 500 fs pulse laser showed an increase at low fluence and a slow drop of ablation rate was observed at high fluence in air and vacuum, which may due to the strong defocusing effects associated with the non-equilibrium ionization of air, and/or the shielding effects of conduction band electrons (CBEs) produced by multi-photon ionization and impact ionization in K9 glass surface. The typical ablation morphologies, e.g. smooth zone and laser-induced periodic surface structures (LIPSS) were also presented and illustrated.

Diode-pumped Kerr-lens mode-locked femtosecond Yb:YAG ceramic laser

NASA Astrophysics Data System (ADS)

Zi-Ye, Gao; Jiang-Feng, Zhu; Ke, Wang; Jun-Li, Wang; Zhao-Hua, Wang; Zhi-Yi, Wei

2016-02-01

We experimentally demonstrated a diode-pumped Kerr-lens mode-locked femtosecond laser based on an Yb:YAG ceramic. Stable laser pulses with 97-fs duration, 2.8-nJ pulse energy, and 320-mW average power were obtained. The femtosecond oscillator operated at a central wavelength of 1049 nm and a repetition rate of 115 MHz. To the best of our knowledge, this is the first demonstration of a Kerr-lens mode-locked operation in a diode-pumped Yb:YAG ceramic laser with sub-100 fs pulse duration. Project supported by the National Major Scientific Instrument Development Project of China (Grant No. 2012YQ120047), the National Natural Science Foundation of China (Grant No. 61205130), and the Fundamental Research Funds for the Central Universities, China (Grant No. JB140502).

Formation of laser-induced periodic surface structures on fused silica upon two-color double-pulse irradiation

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

Höhm, S.; Herzlieb, M.; Rosenfeld, A.

2013-12-16

The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of fused silica with multiple irradiation sequences consisting of laser pulse pairs (50 fs single-pulse duration) of two different wavelengths (400 and 800 nm) is studied experimentally. Parallel polarized double-pulse sequences with a variable delay Δt between −10 and +10 ps and between the individual fs-laser pulses were used to investigate the LIPSS periods versus Δt. These two-color experiments reveal the importance of the ultrafast energy deposition to the silica surface by the first laser pulse for LIPSS formation. The second laser pulse subsequently reinforces the previously seeded spatial LIPSSmore » frequencies.« less

Sub-10-fs control of dissociation pathways in the hydrogen molecular ion with a few-pulse attosecond pulse train

NASA Astrophysics Data System (ADS)

Nabekawa, Yasuo; Furukawa, Yusuke; Okino, Tomoya; Amani Eilanlou, A.; Takahashi, Eiji J.; Yamanouchi, Kaoru; Midorikawa, Katsumi

2016-09-01

The control of the electronic states of a hydrogen molecular ion by photoexcitation is considerably difficult because it requires multiple sub-10 fs light pulses in the extreme ultraviolet (XUV) wavelength region with a sufficiently high intensity. Here, we demonstrate the control of the dissociation pathway originating from the 2pσu electronic state against that originating from the 2pπu electronic state in a hydrogen molecular ion by using a pair of attosecond pulse trains in the XUV wavelength region with a train-envelope duration of ~4 fs. The switching time from the peak to the valley in the oscillation caused by the vibrational wavepacket motion in the 1sσg ground electronic state is only 8 fs. This result can be classified as the fastest control, to the best of our knowledge, of a molecular reaction in the simplest molecule on the basis of the XUV-pump and XUV-probe scheme.

Experimental study of fs-laser induced sub-100-nm periodic surface structures on titanium.

PubMed

Nathala, Chandra S R; Ajami, Ali; Ionin, Andrey A; Kudryashov, Sergey I; Makarov, Sergey V; Ganz, Thomas; Assion, Andreas; Husinsky, Wolfgang

2015-03-09

In this work the formation of laser-induced periodic surface structures (LIPSS) on a titanium surface upon irradiation by linearly polarized femtosecond (fs) laser pulses with a repetition rate of 1 kHz in air environment was studied experimentally. In particular, the dependence of high-spatial-frequency-LIPSS (HSFL) characteristics on various laser parameters: fluence, pulse number, wavelength (800 nm and 400 nm), pulse duration (10 fs - 550 fs), and polarization was studied in detail. In comparison with low-spatial-frequency-LIPSS (LSFL), the HSFL emerge at a much lower fluence with orientation perpendicular to the ridges of the LSFL. It was observed that these two types of LIPSS demonstrate different fluence, shot number and wavelength dependencies, which suggest their origin is different. Therefore, the HSFL formation mechanism cannot be described by the widely accepted interference model developed for describing LSFL formation.

Broadband spectral shaping in regenerative amplifier based on modified polarization-encoded chirped pulse amplification

NASA Astrophysics Data System (ADS)

Wang, Xinliang; Lu, Xiaoming; Liu, Yanqi; Xu, Yi; Wang, Cheng; Li, Shuai; Yu, Linpeng; Liu, Xingyan; Liu, Keyang; Xu, Rongjie; Leng, Yuxin

2018-06-01

We present an intra-cavity spectral shaping method to suppress the spectral narrowing in a Ti:sapphire (Ti:Sa) regenerative amplifier. The spectral shaping is realized by manipulating the stored energies of two Ti:Sa crystals with orthogonal c-axes, changing the length of a quartz plate, and rotating a broadband achromatic half-wave plate. Using this method, in our proof-of-concept experiment, an 84-nm-(FWHM)-broadband amplified pulse with an energy gain larger than 106 is obtained, which supports a 17.8 fs Fourier-transform-limited pulse duration. The pulse is compressed to 18.9 fs.

Solid-density plasma expansion in intense ultra-short laser irradiation measured on nanometer scale and in real time

NASA Astrophysics Data System (ADS)

Kluge, T.; Metzkes, J.; Pelka, A.; Laso Garcia, A.; Prencipe, I.; Bussmann, M.; Zeil, K.; Schoenherr, T.; Hartley, N.; Gutt, C.; Galtier, E.; Nam, I.; Lee, Hj; McBride, Ee; Glenzer, S.; Huebner, U.; Roedel, C.; Nakatsutsumi, M.; Roedel, M.; Rehwald, M.; Garten, M.; Zacharias, M.; Schramm, U.; Cowan, T. E.

2017-10-01

Small Angle X-ray Scattering (SAXS) is discussed to allow unprecedented direct measurements limited only by the probe X-ray wavelength and duration. Here we present the first direct in-situ measurement of intense short-pulse laser - solid interaction that allows nanometer and high temporal resolution at the same time. A 120 fs laser pulse with energy 1 J was focused on a silicon membrane. The density was probed with an X-ray beam of 49 fs duration by SAXS. Despite prepulses, we can exclude premature bulk expansion. The plasma expansion is triggered only shortly before the main pulse, when an expansion of 10 nm within less than 200 fs was measured. Analysis of scattering patterns allows the first direct verification of numerical simulations. Supported by DOE FWP 100182, SF00515; EC FP7 LASERLAB-EUROPE/CHARPAC (contract 284464); German Federal Ministry of Education and Research (BMBF) under Contract Number 03Z1O511; MG and MZ supported by the European Union's Horizon 2020 No 654220.

Comparison of femtosecond- and nanosecond-two-photon-absorption laser-induced fluorescence (TALIF) of atomic oxygen in atmospheric-pressure plasmas

NASA Astrophysics Data System (ADS)

Schmidt, Jacob B.; Sands, Brian; Scofield, James; Gord, James R.; Roy, Sukesh

2017-05-01

Absolute number densities of atomic species produced by nanosecond (ns)-duration, repetitively pulsed electric discharges are measured by two-photon-absorption laser-induced fluorescence (TALIF). Unique to this work is the development of femtosecond-laser-based TALIF (fs-TALIF) that offers a number of advantages over more conventional nanosecond (ns)-pulse-duration laser techniques, such as higher-fidelity quenching rate measurements over a wide pressure range, significantly reduced photolytic interference (including photo-dissociation and photo-ionization), ability to collect two-dimensional images of atomic-species number densities with high spatial resolution aided by higher signal level, and efficient and accurate measurements of atomic-species number densities due to the higher repetition rates of the laser. For full quantification of these advantages, atomic-oxygen TALIF signals are collected from an atmospheric-pressure plasma jet employing both ns- and fs-duration laser-excitation pulses and the results are compared and contrasted.

On-axis non-linear effects with programmable Dammann lenses under femtosecond illumination.

PubMed

Pérez Vizcaíno, Jorge; Mendoza-Yero, Omel; Borrego-Varillas, Rocío; Mínguez-Vega, Gladys; Vázquez de Aldana, Javier R; Láncis, Jesús

2013-05-15

We demonstrate the utilization of Dammann lenses codified onto a spatial light modulator (SLM) for triggering non-linear effects. With continuous wave illumination Dammann lenses are binary phase optical elements that generate a set of equal intensity foci. We theoretically calculate the influence of ultrashort pulse illumination on the uniformity of the generated pattern, which is affected by chromatic aberration for pulses with temporal widths lower than 100 fs. The simulations also indicate that acceptable uniformity can be achieved for pulses of several fs by shortening the distance among foci which can be easily modified with the SLM. Multifocal second-harmonic generation (SHG) and on-axis multiple filamentation are produced and actively controlled in β-BaB2O4 (BBO) and fused silica samples, respectively, with an amplified Ti: Sapphire femtosecond laser of 30 fs pulse duration. Experimental results are in very good agreement with theoretical calculations.

Erbium:ytterbium fiber-laser system delivering watt-level femtosecond pulses using divided pulse amplification

NASA Astrophysics Data System (ADS)

Herda, Robert; Zach, Armin

2015-03-01

We present an Erbium:Ytterbium codoped fiber-amplifer system based on Divided-Pulses-Amplification (DPA) for ultrashort pulses. The output from a saturable-absorber mode-locked polarization-maintaining (PM) fiber oscillator is amplified in a PM normal-dispersion Erbium-doped fiber. After this stage the pulses are positively chirped and have a duration of 2.0 ps at an average power of 93 mW. A stack of 5 birefringent Yttrium-Vanadate crystals divides these pulses 32 times. We amplify these pulses using a double-clad Erbium:Ytterbium codoped fiber pumped through a multimode fiber combiner. The pulses double pass the amplifier and recombine in the crystals using non-reciprocal polarization 90° rotation by a Faraday rotating mirror. Pulses with a duration of 144 fs are obtained after separation from the input beam using a polarizing beam splitter cube. These pulses have an average power of 1.85 W at a repetition rate of 80 MHz. The generation of femtosecond pulses directly from the amplifier was enabled by a positively chirped seed pulse, normally dispersive Yttrium-Vanadate crystals, and anomalously dispersive amplifier fibers. Efficient frequency doubling to 780 nm with an average power of 725 mW and a pulse duration of 156 fs is demonstrated. In summary we show a DPA setup that enables the generation of femtosecond pulses at watt-level at 1560 nm without the need for further external dechirping and demonstrate a good pulse quality by efficient frequency doubling. Due to the use of PM fiber components and a Faraday rotator the setup is environmentally stable.

Standard measurement procedures for the characterization of fs-laser optical components

NASA Astrophysics Data System (ADS)

Starke, Kai; Ristau, Detlev; Welling, Herbert

2003-05-01

Ultra-short pulse laser systems are considered as promising tools in the fields of precise micro-machining and medicine applications. In the course of the development of reliable table top laser systems, a rapid growth of ultra-short pulse applications could be observed during the recent years. The key for improving the performance of high power laser systems is the quality of the optical components concerning spectral characteristics, optical losses and the power handling capability. In the field of ultra-short pulses, standard measurement procedures in quality management have to be validated in respect to effects induced by the extremely high peak power densities. The present work, which is embedded in the EUREKA-project CHOCLAB II, is predominantly concentrated on measuring the multiple-pulse LIDT (ISO 11254-2) in the fs-regime. A measurement facility based on a Ti:Sapphire-CPA system was developed to investigate the damage behavior of optical components. The set-up was supplied with an improved pulse energy detector discriminating the influence of pulse-to-pulse energy fluctuations on the incidence of damage. Aditionally, a laser-calorimetric measurement facility determining the absorption (ISO 11551) utilizing a fs-Ti:Sapphire laser was accomplished. The investigation for different pulse durations between 130 fs and 1 ps revealed a drastic increase of absorption in titania coatings for ultra-short pulses.

Pulse compression of a high-power thin disk laser using rod-type fiber amplifiers.

PubMed

Saraceno, C J; Heckl, O H; Baer, C R E; Südmeyer, T; Keller, U

2011-01-17

We report on two pulse compressors for a high-power thin disk laser oscillator using rod-type fiber amplifiers. Both systems are seeded by a standard SESAM modelocked thin disk laser that delivers 16 W of average power at a repetition rate of 10.6 MHz with a pulse energy of 1.5 μJ and a pulse duration of 1 ps. We discuss two results with different fiber parameters with different trade-offs in pulse duration, average power, damage and complexity. The first amplifier setup consists of a Yb-doped fiber amplifier with a 2200 μm2 core area and a length of 55 cm, resulting in a compressed average power of 55 W with 98-fs pulses at a repetition rate of 10.6 MHz. The second system uses a shorter 36-cm fiber with a larger core area of 4500 μm2. In a stretcher-free configuration we obtained 34 W of compressed average power and 65-fs pulses. In both cases peak powers of > 30 MW were demonstrated at several μJ pulse energies. The power scaling limitations due to damage and self-focusing are discussed.

Pulse duration dependent nonlinear optical response in black phosphorus dispersions

NASA Astrophysics Data System (ADS)

Tang, Shana; He, Zhiliang; Liang, Guowen; Chen, Si; Ge, Yanqi; Sang, David K.; Lu, Jianxin; Lu, Shunbin; Wen, Qiao; Zhang, Han

2018-01-01

Black phosphorus (BP), is the most thermodynamically stable allotrope of phosphorus, the narrow direct band gap and the strong light-matter interaction make BP a promising nonlinear optical (NLO) nano-material. In this paper, we use the open aperture Z- scan method to measure the NLO property of BP dispersion. Saturable absorption was observed in the BP material through the excitation of Ti: sapphire laser at 800 nm. Three different excitation pulse duration (100 fs, 1 ps and 10 ps) were used in the experiments, and BP exhibited different NLO performance. The results show that nonlinear absorption coefficient and figure of merit of BP nanosheets are proportional to the pulse duration while saturable intensity is opposite to pulse duration.

Monolithic hybrid optics for focusing ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Fuchs, U.

2014-03-01

Almost any application of ultrashort laser pulses involves focusing them in order to reach high intensities and/or small spot sizes as needed for micro-machining or Femto-LASIK. Hence, it is indispensable to be able to understand pulse front distortion caused by real world optics. Focusing causes pulse front distortion due to aberrations, dispersion and diffraction. Thus, the spatio-temporal profile of ultrashort laser is altered, which increases automatically the pulse duration and the focusing spot. Consequently, the main advantage of having ultrashort laser pulses - pulse durations way below 100 fs - can be lost in that one last step of the experimental set-up by focusing them unfavorable. Since compensating for dispersion, aberration and diffraction effects is quite complicated and not always possible, we pursue a different approach. We present a specially designed monolithic hybrid optics comprising refraction and diffraction effects for tight spatial and temporal focusing of ultrashort laser pulses. Both aims can be put into practice by having a high numerical aperture (NA = 0.35) and low internal dispersion at the same time. The focusing properties are very promising, due to a design, which provides diffraction limited focusing for 100 nm bandwidth at 780 nm center wavelength. Thus, pulses with durations as short as 10 fs can be focused without pulse front distortion. The outstanding performance of this optics is shown in theory and experimentally. Above that, such focusing optics are easily adapted to their special purpose - changing the center wavelength, achromatic bandwidth or even correcting for focusing into material is possible.

Intracellular cavitation as a mechanism of short-pulse laser injury to the retinal pigment epithelium

NASA Astrophysics Data System (ADS)

Kelly, Michael William

This research was primarily motivated to determine the retinal injury mechanism from ultra-short pulse (<1ns) lasers. The American National Standards Institute, ANSI, standards for safe retinal exposures, and mechanisms for injury, are established for pulse durations longer than 1 ns. Little data exists for shorter pulse durations. High temperatures and pressures, generated within pigmented melanosomes, leads to mechanically mediated injury for such exposures. We used nanosecond time resolved imaging to evaluate transient photo-mechanical effects on isolated melanosomes, pigmented cell cultures, and the retinal pigment epithelium, RPE, ex-vivo. Exposures between 20 ns and 100 fs were performed. We developed a unique ex-vivo model to examine transient events directly on the RPE. Evaluation of cell viability was accomplished in real time, minutes after the exposure. The threshold for cavitation (bubble formation) around single melanosomes corresponded with the threshold for intracellular cavitation and cell killing, in the nanosecond and picosecond domain. Shock waves, formed around melanosomes following sub-nanosecond exposures, did not affect the mechanism for cell killing at threshold. Although the wavelength was increased for shorter exposures (3 ps, 300 fs, and 100 fs) the threshold for intracellular cavitation decreased. All results were compared with data collected by others, using live animal models.

Tunable femtosecond laser based on the Nd3+:BaLaGa 3O 7 disordered crystal

NASA Astrophysics Data System (ADS)

Agnesi, A.; Pirzio, F.; Tartara, L.; Ugolotti, E.; Zhang, H.; Wang, J.; Yu, H.; Petrov, V.

2014-03-01

We demonstrate clear inhomogeneous linewidth broadening for the disordered laser crystal Nd:BaLaGa3O7 (Nd:BLG), which is very promising for the replacement of Nd:glass for ultrafast sources in multiwatt power applications. A Nd:BLG laser oscillator passively mode-locked and pumped by a Ti:sapphire laser generated pulses of 316-fs duration at 1060 nm, whose spectrum completely fills the fluorescence peak at such wavelength. More interestingly, sub-picosecond pulses were smoothly tunable in a 20-nm range, from 1070 to 1090 nm. The shortest pulses achieved were 290 fs long, centered at 1075 nm.

Ion-coincidence momentum imaging of three-body Coulomb explosion of formaldehyde in ultrashort intense laser fields

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

Fushitani, M.; Matsuda, A.; Hishikawa, A., E-mail: hishi@chem.nagoya-u.ac.jp

Three-body Coulomb explosion of formaldehyde (H{sub 2}CO) in intense 7- and 35-fs laser fields (1.3 × 10{sup 15} W/cm{sup 2}) has been investigated by using ion-coincidence momentum imaging technique. Two types of explosion pathways from the triply charged state, H{sub 2}CO{sup 3+} → (i) H{sup +} + H{sup +} + CO{sup +} and (ii) H{sup +} + CH{sup +} + O{sup +}, have been identified. It is shown from the momentum correlation of the fragment ions of pathway (i), that the geometrical structure of the molecule is essentially frozen along the H-C-H bending coordinate for the 7-fs case. On the othermore » hand, for a longer pulse duration (35 fs), structural deformation along the C-H stretching and H-C-H bending coordinates is identified, which is ascribed to the nuclear dynamics in the dication states populated within the laser pulse duration.« less

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

NASA Astrophysics Data System (ADS)

Tawfik, Walid

2015-06-01

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

Nonlinear resonance scattering of femtosecond X-ray pulses on atoms in plasmas

NASA Astrophysics Data System (ADS)

Rosmej, F. B.; Astapenko, V. A.; Lisitsa, V. S.; Moroz, N. N.

2017-11-01

It is shown that for sufficiently short pulses the resonance scattering probability becomes a nonlinear function of the pulse duration. For fs X-ray pulses scattered on atoms in plasmas maxima and minima develop in the nonlinear regime whereas in the limit of long pulses the probability becomes linear and turns over into the standard description of the electromagnetic pulse scattering. Numerical calculations are carried out in terms of a generalized scattering probability for the total time of pulse duration including fine structure splitting and ion Doppler broadening in hot plasmas. For projected X-ray monocycles, the generalized nonlinear approach differs by 1-2 orders of magnitude from the standard theory.

Materials processing by use of a Ti:Sapphire laser with automatically-adjustable pulse duration

NASA Astrophysics Data System (ADS)

Kamata, M.; Imahoko, T.; Ozono, K.; Obara, M.

We have developed an automatic pulsewidth-adjustable femtosecond Ti:Sapphire laser system that can generate an output of 50 fs-1 ps in duration, and sub-mJ/pulse at a repetition rate of 1 kpps. The automatic pulse compressor enables one to control the pulsewidth in the range of 50 fs-1 ps by use of a personal computer (PC). The compressor can change the distance in-between and the tilt angle of the grating pairs by use of two stepping motors and two piezo-electric transducer(PZT) driven actuators, respectively. Both are controlled by a PC. Therefore, not only control of the pulsewidth, but also of the optical chirp becomes easy. By use of this femtosecond laser system, we fabricated a waveguide in fused quartz. The numerical aperture is chosen to 0.007 to loosely focus the femtosecond laser. The fabricated waveguides are well controllable by the incident laser pulsewidth. We also demonstrated the ablation processing of hydroxyapatite (Ca10(PO4)6(OH)2), which is a key component of human tooth and human bone for orthopedics and dentistry. With pulsewidth tunable output from 50 fs through 2 ps at 1 kpps, the chemical content of calcium and phosphorus is kept unchanged before and after 50-fs-2-ps laser ablation. We also demonstrated the precise ablation processing of human tooth enamel with 2 ps Ti:Sapphire laser.

Linear ultrafast dynamics of plasmon and magnetic resonances in nanoparticles

NASA Astrophysics Data System (ADS)

Lazzarini, Carlo Maria; Tadzio, Levato; Fitzgerald, Jamie M.; Sánchez-Gil, José A.; Giannini, Vincenzo

2017-12-01

In this study we present an analytical description of the ultrafast localized surface plasmon and magnetic resonance dynamics in a single nanoparticle (Ag or Si), driven by an ultrashort (fs time scale) Gaussian pulse. Three possible scenarios have been found depending on the incident field, i.e., pulse duration much shorter than, similar to, and much longer than the localized surface plasmon resonance (LSPR) lifetime. A rich physics arises for τpulse<τLSPR , even in the linear regime. The surface plasmon dynamics is manifested as (i) a temporal delay of the surface plasmon excitation with regard to the freely propagating pulse and as (ii) a negative exponential tail after the exciting pulse is over. In addition, for sub-fs pulses clear oscillations in the near-field decay have been observed. A similar scenario has been observed considering a nonabsorbing Si sphere. Nanoparticle resonance dynamics may lead to a wealth of new phenomena and applications in nanophotonics such as multipole order resonance interference, pulse-induced delay or temporal shaping on the fs scale, high harmonic generation, attosecond near-field pulse sources, and electron acceleration from metasurface or 3D engineered nanostructures.

Femtosecond versus picosecond laser pulses for film-free laser bioprinting.

PubMed

Petit, Stephane; Kérourédan, Olivia; Devillard, Raphael; Cormier, Eric

2017-11-01

We investigate the properties of microjets in the context of film-free laser induced forward transfer in the femtosecond and picosecond regimes. The influence of the pulse duration (ranging from 0.4 to 12 ps) and the energy (ranging from 6 to 12 μJ) is systematically studied on the height, diameter, speed, volume, and shape of the jets. The 400 fs pulses generate thin and stable jets compatible with bioprinting, while 14 ps pulses generate more unstable jets. A pulse duration around 8 ps seems, therefore, to be an interesting trade-off to cover many bio-applications of microjets generated by lasers.

Pulse generation without gain-bandwidth limitation in a laser with self-similar evolution.

PubMed

Chong, A; Liu, H; Nie, B; Bale, B G; Wabnitz, S; Renninger, W H; Dantus, M; Wise, F W

2012-06-18

With existing techniques for mode-locking, the bandwidth of ultrashort pulses from a laser is determined primarily by the spectrum of the gain medium. Lasers with self-similar evolution of the pulse in the gain medium can tolerate strong spectral breathing, which is stabilized by nonlinear attraction to the parabolic self-similar pulse. Here we show that this property can be exploited in a fiber laser to eliminate the gain-bandwidth limitation to the pulse duration. Broad (∼200 nm) spectra are generated through passive nonlinear propagation in a normal-dispersion laser, and these can be dechirped to ∼20-fs duration.

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.

The role of plasma density scale length on the laser pulse propagation and scattering in relativistic regime

NASA Astrophysics Data System (ADS)

Pishdast, Masoud; Ghasemi, Seyed Abolfazl; Yazdanpanah, Jamal Aldin

2017-10-01

The role of plasma density scale length on two short and long laser pulse propagation and scattering in under dense plasma have been investigated in relativistic regime using 1 D PIC simulation. In our simulation, different density scale lengths and also two short and long pulse lengths with temporal pulse duration τL = 60 fs and τL = 300 fs , respectively have been used. It is found that laser pulse length and density scale length have considerable effects on the energetic electron generation. The analysis of total radiation spectrum reveals that, for short laser pulses and with reducing density scale length, more unstable electromagnetic modes grow and strong longitudinal electric field generates which leads to the generation of more energetic plasma particles. Meanwhile, the dominant scattering mechanism is Raman scattering and tends to Thomson scattering for longer laser pulse.

Intrastromal refractive sugery with ultrashort laser pulses in living animals

NASA Astrophysics Data System (ADS)

Heisterkamp, Alexander; Mamom, Thanongsak; Kermani, Omid; Drommer, Wolfgang; Welling, Herbert; Ertmer, Wolfgang; Lubatschowski, Holger

2002-06-01

In order to perform refractive surgery, fs-laser pulses of 130-fs pulse duration were focused into animal cornea. By focusing the radiation down to spot-sizes of 5 micrometers , very precise cuts could be achieved inside the treated eyes, accompanied with minimum collateral damage to the tissue by thermal or mechanical effects. Due to these low side effects, micrometers -cutting precisions at preparing of corneal flaps and lenticules can be achieved. Thus, animal studies with 8 living rabbits were performed, in which intrastromal lenticules and flaps were created and extracted. Wound healing reactions were studied by histo- pathological analysis of the treated eyes in intervals at one, 7, 14 and 28 days after surgery. The treated eyes showed mild wound healing reactions with comparable results to what is known from Excimer-LASIK. Moreover the use of the fs-laser offered new possibilities in preparation of corneal flaps, providing advantages to the use of the mechanical keratome.

Fabrication of demultiplexer for T bps optical signals by using spincoated squarylium dye J-aggregates exhibiting femtosecond optical response

NASA Astrophysics Data System (ADS)

Iwasa, Izumi; Furuki, Makoto; Tian, Minquan; Sato, Yasuhiro; Pu, Lyong S.; Tatsuura, Setoshi; Wada, Osamu

2001-06-01

We fabricated spincoated films of squarylium dye (SQ) J- aggregates exhibiting femtosecond optical response at room temperature. Optical dynamics measurements revealed that the saturable absorption of the SQ J-aggregates film exhibited a decay time of less than 100 fs at a pump energy of 80 fJ/micrometer2. With this ultrafast SQ optical film, four- output demultiplex operation for T bps pulses was demonstrated. A series of 4 optical pulses with 100 fs duration and 1 ps interval (corresponding to 1 T bps signals) were irradiated onto the SQ film synchronized with a 100 fs gate pulse at a finite angle. Four demultiplexed signals were clearly observed at different areas on the CCD camera. Multi- output serial-to-parallel demultiplexer for T bps optical signals can be formed using the SQ J-aggregates film.

Autoionizing states driven by stochastic electromagnetic fields

NASA Astrophysics Data System (ADS)

Mouloudakis, G.; Lambropoulos, P.

2018-01-01

We have examined the profile of an isolated autoionizing resonance driven by a pulse of short duration and moderately strong field. The analysis has been based on stochastic differential equations governing the time evolution of the density matrix under a stochastic field. Having focused our quantitative analysis on the 2{{s}}2{{p}}({}1{{P}}) resonance of helium, we have investigated the role of field fluctuations and of the duration of the pulse. We report surprisingly strong distortion of the profile, even for peak intensity below the strong field limit. Our results demonstrate the intricate connection between intensity and pulse duration, with the latter appearing to be the determining influence, even for a seemingly short pulse of 50 fs. Further effects that would arise under much shorter pulses are discussed.

Observation of femtosecond X-ray interactions with matter using an X-ray–X-ray pump–probe scheme

PubMed Central

Inoue, Ichiro; Inubushi, Yuichi; Sato, Takahiro; Tono, Kensuke; Katayama, Tetsuo; Kameshima, Takashi; Ogawa, Kanade; Togashi, Tadashi; Owada, Shigeki; Amemiya, Yoshiyuki; Tanaka, Takashi; Hara, Toru

2016-01-01

Resolution in the X-ray structure determination of noncrystalline samples has been limited to several tens of nanometers, because deep X-ray irradiation required for enhanced resolution causes radiation damage to samples. However, theoretical studies predict that the femtosecond (fs) durations of X-ray free-electron laser (XFEL) pulses make it possible to record scattering signals before the initiation of X-ray damage processes; thus, an ultraintense X-ray beam can be used beyond the conventional limit of radiation dose. Here, we verify this scenario by directly observing femtosecond X-ray damage processes in diamond irradiated with extraordinarily intense (∼1019 W/cm2) XFEL pulses. An X-ray pump–probe diffraction scheme was developed in this study; tightly focused double–5-fs XFEL pulses with time separations ranging from sub-fs to 80 fs were used to excite (i.e., pump) the diamond and characterize (i.e., probe) the temporal changes of the crystalline structures through Bragg reflection. It was found that the pump and probe diffraction intensities remain almost constant for shorter time separations of the double pulse, whereas the probe diffraction intensities decreased after 20 fs following pump pulse irradiation due to the X-ray–induced atomic displacement. This result indicates that sub-10-fs XFEL pulses enable conductions of damageless structural determinations and supports the validity of the theoretical predictions of ultraintense X-ray–matter interactions. The X-ray pump–probe scheme demonstrated here would be effective for understanding ultraintense X-ray–matter interactions, which will greatly stimulate advanced XFEL applications, such as atomic structure determination of a single molecule and generation of exotic matters with high energy densities. PMID:26811449

Architecture and Bloch-Maxwell modelling of multi-mJ 100 fs fully-coherent soft X-ray laser based on X-ray CPA

NASA Astrophysics Data System (ADS)

Zeitoun, Ph.; Oliva, E.; Fajardo, M.; Cheriaux, G.; Le, T. T. T.; Li, L.; Pitman, M.; Ros, D.; Sebban, S.; Velarde, P.

2012-07-01

By seeding amplifying plasmas pumped with the so-called Transient collisionnal excitation scheme, the amplified pulse seems to be limited to an energy of several 10's of μJ. Aiming to attain several mJ, we study the seeding of plasma pumped by long laser pulse. Thanks to our time-dependent Maxwell-Bloch code, we demonstrate that direct seeding with femtosecond pulse is inefficient. We also study the amplification of pulse train with the drawback of re-synchronizing the pulses. We proposed and studied the amplification of high harmonic seed stretched by a grating pair, amplified finally compressed. We consider off-axis diffraction on the gratings for maximizing their efficiency. Considering the phase deformation induced by the amplification and the spectral narrowing the final pulse is 230 fs in duration and 5 mJ.

Architecture and Bloch-Maxwell modelling of multi-mJ 100 fs fully-coherent soft X-ray laser based on X-ray CPA

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

Zeitoun, Ph.; Oliva, E.; Fajardo, M.

2012-07-09

By seeding amplifying plasmas pumped with the so-called Transient collisionnal excitation scheme, the amplified pulse seems to be limited to an energy of several 10's of {mu}J. Aiming to attain several mJ, we study the seeding of plasma pumped by long laser pulse. Thanks to our time-dependent Maxwell-Bloch code, we demonstrate that direct seeding with femtosecond pulse is inefficient. We also study the amplification of pulse train with the drawback of re-synchronizing the pulses. We proposed and studied the amplification of high harmonic seed stretched by a grating pair, amplified finally compressed. We consider off-axis diffraction on the gratings formore » maximizing their efficiency. Considering the phase deformation induced by the amplification and the spectral narrowing the final pulse is 230 fs in duration and 5 mJ.« less

Femtosecond optical injection of intact plant cells using a reconfigurable platform

NASA Astrophysics Data System (ADS)

Mitchell, Claire A.; Kalies, Stefan; Cizmar, Tomas; Bellini, Nicola; Kubasik-Thayil, Anisha; Heisterkamp, Alexander; Torrance, Lesley; Roberts, Alison G.; Gunn-Moore, Frank J.; Dholakia, Kishan

2014-03-01

The use of ultrashort-pulsed lasers for molecule delivery and transfection has proved to be a non-invasive and highly efficient technique for a wide range of mammalian cells. This present study investigates the effectiveness of femtosecond photoporation in plant cells, a hard-to-manipulate yet agriculturally relevant cell type, specifically suspension tobacco BY-2 cells. Both spatial and temporal shaping of the light field is employed to optimise the delivery of membrane impermeable molecules into plant cells using a reconfigurable optical system designed to be able to switch easily between different spatial modes and pulse durations. The use of a propagation invariant Bessel beam was found to increase the number of cells that could be viably optoinjected, when compared to the use of a Gaussian beam. Photoporation with a laser producing sub-12 fs pulses, coupled with a dispersion compensation system to retain the pulse duration at focus, reduced the power required for efficient optical injection by 1.5-1.8 times when compared to a photoporation with a 140 fs laser output.

Generation of 70 fs broadband pulses in a hybrid nonlinear amplification system with mode-locked Yb:YAG ceramic oscillator

NASA Astrophysics Data System (ADS)

Liu, Yang; Wang, Chao; Luo, Daping; Yang, Chao; Li, Jiang; Ge, Lin; Pan, Yubai; Li, Wenxue

2017-12-01

We demonstrate the passively mode-locked laser performances of bulk Yb:YAG ceramic prepared by non-aqueous tape casting, which generates initial pulses in temporal width of 3 ps and spectrum width of 3 nm without intra-cavity dispersion management. The ceramic laser is further used as seeding oscillator in a fiber nonlinear amplification system, where ultrashort pulses in maximum output power of ˜100 W and pulse duration of 70 fs are achieved. Moreover, the laser spectrum is broadened to be ˜41 nm due to self-phase modulation effects in the gain fiber, overcoming the narrow spectrum limitations of ceramic materials. Our approach opens a new avenue for power-scaling and spectrum-expanding of femtosecond ceramic lasers.

Start-to-end simulation of single-particle imaging using ultra-short pulses at the European X-ray Free-Electron Laser

DOE PAGES

Fortmann-Grote, Carsten; Buzmakov, Alexey; Jurek, Zoltan; ...

2017-09-01

Single-particle imaging with X-ray free-electron lasers (XFELs) has the potential to provide structural information at atomic resolution for non-crystalline biomolecules. This potential exists because ultra-short intense pulses can produce interpretable diffraction data notwithstanding radiation damage. This paper explores the impact of pulse duration on the interpretability of diffraction data using comprehensive and realistic simulations of an imaging experiment at the European X-ray Free-Electron Laser. In conclusion, it is found that the optimal pulse duration for molecules with a few thousand atoms at 5 keV lies between 3 and 9 fs.

Start-to-end simulation of single-particle imaging using ultra-short pulses at the European X-ray Free-Electron Laser

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

Fortmann-Grote, Carsten; Buzmakov, Alexey; Jurek, Zoltan

Single-particle imaging with X-ray free-electron lasers (XFELs) has the potential to provide structural information at atomic resolution for non-crystalline biomolecules. This potential exists because ultra-short intense pulses can produce interpretable diffraction data notwithstanding radiation damage. This paper explores the impact of pulse duration on the interpretability of diffraction data using comprehensive and realistic simulations of an imaging experiment at the European X-ray Free-Electron Laser. In conclusion, it is found that the optimal pulse duration for molecules with a few thousand atoms at 5 keV lies between 3 and 9 fs.

Dynamic model of target charging by short laser pulse interactions

NASA Astrophysics Data System (ADS)

Poyé, A.; Dubois, J.-L.; Lubrano-Lavaderci, F.; D'Humières, E.; Bardon, M.; Hulin, S.; Bailly-Grandvaux, M.; Ribolzi, J.; Raffestin, D.; Santos, J. J.; Nicolaï, Ph.; Tikhonchuk, V.

2015-10-01

A model providing an accurate estimate of the charge accumulation on the surface of a metallic target irradiated by a high-intensity laser pulse of fs-ps duration is proposed. The model is confirmed by detailed comparisons with specially designed experiments. Such a model is useful for understanding the electromagnetic pulse emission and the quasistatic magnetic field generation in laser-plasma interaction experiments.

Dynamic model of target charging by short laser pulse interactions.

PubMed

Poyé, A; Dubois, J-L; Lubrano-Lavaderci, F; D'Humières, E; Bardon, M; Hulin, S; Bailly-Grandvaux, M; Ribolzi, J; Raffestin, D; Santos, J J; Nicolaï, Ph; Tikhonchuk, V

2015-10-01

A model providing an accurate estimate of the charge accumulation on the surface of a metallic target irradiated by a high-intensity laser pulse of fs-ps duration is proposed. The model is confirmed by detailed comparisons with specially designed experiments. Such a model is useful for understanding the electromagnetic pulse emission and the quasistatic magnetic field generation in laser-plasma interaction experiments.

23RD International Conference on Phenomena in Ionized Gases, Volume 1

DTIC Science & Technology

1998-12-01

irradiation of clusters by intense laser pulses [8], but with a variation of the cathode... intensity is much less intense in transformed explosively to a plasma by a focused water than in gases. Then, to avoid too noisy line pulsed laser beam...evolution of particle species. The optical ultrashort , down to 10 fs duration, laser pulse [8]. source is approximated as a quazimonochromatic Part

Reconfigurable wavefront sensor for ultrashort pulses.

PubMed

Bock, Martin; Das, Susanta Kumar; Fischer, Carsten; Diehl, Michael; Börner, Peter; Grunwald, Ruediger

2012-04-01

A highly flexible Shack-Hartmann wavefront sensor for ultrashort pulse diagnostics is presented. The temporal system performance is studied in detail. Reflective operation is enabled by programming tilt-tolerant microaxicons into a liquid-crystal-on-silicon spatial light modulator. Nearly undistorted pulse transfer is obtained by generating nondiffracting needle beams as subbeams. Reproducible wavefront analysis and spatially resolved second-order autocorrelation are demonstrated at incident angles up to 50° and pulse durations down to 6 fs.

Nearly fully compressed 1053 nm pulses directly obtained from 800 nm laser-seeded photonic crystal fiber below zero dispersion point

NASA Astrophysics Data System (ADS)

Refaeli, Zaharit; Shamir, Yariv; Ofir, Atara; Marcus, Gilad

2018-02-01

We report a simple robust and broadly spectral-adjustable source generating near fully compressed 1053 nm 62 fs pulses directly out of a highly-nonlinear photonic crystal fiber. A dispersion-nonlinearity balance of 800 nm Ti:Sa 20 fs pulses was obtained initially by negative pre-chirping and then launching the pulses into the fibers' normal dispersion regime. Following a self-phase modulation spectral broadening, some energy that leaked below the zero dispersion point formed a soliton whose central wavelength could be tuned by Self-Frequency-Raman-Shift effect. Contrary to a common approach of power, or, fiber-length control over the shift, here we continuously varied the state of polarization, exploiting the Raman and Kerr nonlinearities responsivity for state of polarization. We obtained soliton pulses with central wavelength tuned over 150 nm, spanning from well below 1000 to over 1150 nm, of which we could select stable pulses around the 1 μm vicinity. With linewidth of > 20 nm FWHM Gaussian-like temporal-shape pulses with 62 fs duration and near flat phase structure we confirmed high quality pulse source. We believe such scheme can be used for high energy or high power glass lasers systems, such as Nd or Yb ion-doped amplifiers and systems.

Negatively-chirped laser enables nonlinear excitation and nanoprocessing with sub-20-fs pulses

NASA Astrophysics Data System (ADS)

Uchugonova, A.; Müller, J.; Bückle, R.; Tempea, G.; Isemann, A.; Stingl, A.; König, K.

2008-02-01

It has long been considered that the advantages emerging from employing chirp pre-compensation in nonlinear microscopy were overweighed by the complexity of prism- or grating-based compressors. These concerns were refuted with the advent of dispersive-mirrors-based compressors that are compact, user-friendly and sufficiently accurate to support sub-20-fs pulse delivery. Recent advances in the design of dispersive multilayer mirrors resulted in improved bandwidth (covering now as much as half of the gain bandwidth of Ti:Sapphire) and increased dispersion per bounce (one reflection off a state-of-the-art dispersive mirror pre-compensates the dispersion corresponding to >10mm of glass). The compressor built with these mirrors is sufficiently compact to be integrated in the housing of a sub-12-fs Ti:Sapphire oscillator. A complete scanning nonlinear microscope (FemtOgene, JenLab GmbH) equipped with highly-dispersive, large-NA objectives (Zeiss EC Plan-Neofluoar 40x/1.3, Plan-Neofluar 63x/1,25 Oil) was directly seeded with this negatively chirped laser. The pulse duration was measured at the focus of the objectives by inserting a scanning autocorrelator in the beam path between the laser and the microscope and recording the second order interferometric autocorrelation traces with the detector integrated in the microscope. Pulse durations <20fs were measured with both objectives. The system has been applied for two-photon imaging, transfection and optical manipulation of stem cells. Here we report on the successful transfection of human stem cells by transient optoporation of the cell membrane with a low mean power of < 7 mW and a short μs beam dwell time. Optically transfected cells were able to reproduce. The daughter cell expressed also green fluorescent proteins (GFP) indicating the successful modification of the cellular DNA.

Core-pumped mode-locked ytterbium-doped fiber laser operating around 980 nm

NASA Astrophysics Data System (ADS)

Zhou, Yue; Dai, Yitang; Li, Jianqiang; Yin, Feifei; Dai, Jian; Zhang, Tian; Xu, Kun

2018-07-01

In this letter, we first demonstrate a core-pumped passively mode-locked all-normal-dispersion ytterbium-doped fiber oscillator based on nonlinear polarization evolution operating around 980 nm. The dissipative soliton fiber laser pulse can be compressed down to 250 fs with 1 nJ pulse energy, and the slope efficiency of the oscillator can be as high as 19%. To improve the dissipative soliton laser output spectrum smoothness, we replace the birefringent plate based intracavity filter with a diffraction-grating based filter. The output pulse duration can then be further compressed down to 180 fs with improved spectral-smoothness. These schemes have potential applications in seeding cryogenic Yb:YLF amplifiers and underwater exploration of marine resources.

Generation of 103 fs mode-locked pulses by a gain linewidth-variable Nd,Y:CaF2 disordered crystal.

PubMed

Qin, Z P; Xie, G Q; Ma, J; Ge, W Y; Yuan, P; Qian, L J; Su, L B; Jiang, D P; Ma, F K; Zhang, Q; Cao, Y X; Xu, J

2014-04-01

We have demonstrated a diode-pumped passively mode-locked femtosecond Nd,Y:CaF2 disordered crystal laser for the first time to our knowledge. By choosing appropriate Y-doping concentration, a broad fluorescence linewidth of 31 nm has been obtained from the gain linewidth-variable Nd,Y:CaF2 crystal. With the Nd,Y:CaF2 disordered crystal as gain medium, the mode-locked laser generated pulses with pulse duration as short as 103 fs, average output power of 89 mW, and repetition rate of 100 MHz. To our best knowledge, this is the shortest pulse generated from Nd-doped crystal lasers so far. The research results show that the Nd,Y:CaF2 disordered crystal will be a potential alternative as gain medium of repetitive chirped pulse amplification for high-peak-power lasers.

Electron acceleration by laser produced wake field: Pulse shape effect

NASA Astrophysics Data System (ADS)

Malik, Hitendra K.; Kumar, Sandeep; Nishida, Yasushi

2007-12-01

Analytical expressions are obtained for the longitudinal field (wake field: Ex), density perturbations ( ne') and the potential ( ϕ) behind a laser pulse propagating in a plasma with the pulse duration of the electron plasma period. A feasibility study on the wake field is carried out with Gaussian-like (GL) pulse, rectangular-triangular (RT) pulse and rectangular-Gaussian (RG) pulse considering one-dimensional weakly nonlinear theory ( ne'/n0≪1), and the maximum energy gain acquired by an electron is calculated for all these three types of the laser pulse shapes. A comparative study infers that the RT pulse yields the best results: In its case maximum electron energy gain is 33.5 MeV for a 30 fs pulse duration whereas in case of GL (RG) pulse of the same duration the gain is 28.6 (28.8)MeV at the laser frequency of 1.6 PHz and the intensity of 3.0 × 10 18 W/m 2. The field of the wake and hence the energy gain get enhanced for the higher laser frequency, larger pulse duration and higher laser intensity for all types of the pulses.

Surface nanotexturing of tantalum by laser ablation in water

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

Barmina, E V; Simakin, Aleksandr V; Shafeev, Georgii A

2009-01-31

Surface nanotexturing of tantalum by ablation with short laser pulses in water has been studied experimentally using three ablation sources: a neodymium laser with a pulse duration of 350 ps, an excimer laser (248 nm) with a pulse duration of 5 ps and a Ti:sapphire laser with a pulse duration of 180 fs. The morphology of the nanotextured surfaces has been examined using a nanoprofilometer and field emission scanning electron microscope. The results demonstrate that the average size of the hillocks produced on the target surface depends on the laser energy density and is {approx}200 nm at an energy densitymore » approaching the laser-melting threshold of tantalum and a pulse duration of 350 ps. Their surface density reaches 10{sup 6} cm{sup -2}. At a pulse duration of 5 ps, the average hillock size is 60-70 nm. Nanotexturing is accompanied by changes in the absorption spectrum of the tantalum surface in the UV and visible spectral regions. The possible mechanisms of surface nanotexturing and potential applications of this effect are discussed. (nanostructures)« less

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

Generation of energetic femtosecond green pulses based on an OPCPA-SFG scheme.

PubMed

Mero, M; Sipos, A; Kurdi, G; Osvay, K

2011-05-09

Femtosecond green pulses were generated from broadband pulses centered at 800 nm and quasi-monochromatic pulses centered at 532 nm using noncollinear optical parametric chirped pulse amplification (NOPCPA) followed by sum frequency mixing. In addition to amplifying the 800-nm pulses, the NOPCPA stage pumped by a Q-switched, injection seeded Nd:YAG laser also provided broadband idler pulses at 1590 nm. The signal and idler pulses were sum frequency mixed using achromatic and chirp assisted phase matching yielding pulses near 530 nm with a bandwidth of 12 nm and an energy in excess of 200 μJ. The generated pulses were recompressed with a grating compressor to a duration of 150 fs. The technique is scalable to high energies, broader bandwidths, and shorter pulse durations with compensation for higher order chirps and dedicated engineering of the interacting beams. © 2011 Optical Society of America

Start-to-end simulation of single-particle imaging using ultra-short pulses at the European X-ray Free-Electron Laser

PubMed Central

Buzmakov, Alexey; Jurek, Zoltan; Loh, Ne-Te Duane; Samoylova, Liubov; Santra, Robin; Schneidmiller, Evgeny A.; Tschentscher, Thomas; Yakubov, Sergey; Yoon, Chun Hong; Yurkov, Michael V.; Ziaja-Motyka, Beata; Mancuso, Adrian P.

2017-01-01

Single-particle imaging with X-ray free-electron lasers (XFELs) has the potential to provide structural information at atomic resolution for non-crystalline biomolecules. This potential exists because ultra-short intense pulses can produce interpretable diffraction data notwithstanding radiation damage. This paper explores the impact of pulse duration on the interpretability of diffraction data using comprehensive and realistic simulations of an imaging experiment at the European X-ray Free-Electron Laser. It is found that the optimal pulse duration for molecules with a few thousand atoms at 5 keV lies between 3 and 9 fs. PMID:28989713

Femtosecond diffraction dynamics of laser-induced periodic surface structures on fused silica

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

Hoehm, S.; Rosenfeld, A.; Krueger, J.

2013-02-04

The formation of laser-induced periodic surface structures (LIPSS) on fused silica upon irradiation with linearly polarized fs-laser pulses (50 fs pulse duration, 800 nm center wavelength) is studied experimentally using a transillumination femtosecond time-resolved (0.1 ps-1 ns) pump-probe diffraction approach. This allows to reveal the generation dynamics of near-wavelength-sized LIPSS showing a transient diffraction at specific spatial frequencies even before a corresponding permanent surface relief was observed. The results confirm that the ultrafast energy deposition to the materials surface plays a key role and triggers subsequent physical mechanisms such as carrier scattering into self-trapped excitons.

Picosecond transient backward stimulated Raman scattering and pumping of femtosecond dye lasers

NASA Astrophysics Data System (ADS)

Arrivo, Steven M.; Spears, Kenneth G.; Sipior, Jeffrey

1995-02-01

We report studies of transient, backward stimulated, Raman scattering (TBSRS) in solvents with a 10 Hz, 27 ps, 532 nm pump laser. The TBSRS effect was used to create pulses at 545 nm and 630 nm with durations of 2-3 ps and 5-10 μJ of energy. The duration, energy and fluctuations of the Raman pulse were studied as a function of pump energy and focal parameters. A 5 μJ Raman pulse was amplified in either a Raman amplifier or two stage dye amplifier to 1 mJ levels. A 545 nm pulse of 3 ps duration was generated in CCl 4 and was then used to pump a short cavity dye laser (SCDL). The SCDL oscillator and a 5 stage dye amplifier provided a pulse of 700 fs and 400 μJ that was tunable near 590 nm.

Isolated Attosecond Pulse Generation without the Need to Stabilize the Carrier-Envelope Phase of Driving Lasers

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

Gilbertson, Steve; Khan, Sabih D.; Wu Yi

2010-08-27

Single isolated attosecond pulses can be extracted from a pulse train with an ultrafast gate in the generation target. By setting the gate width sufficiently narrow with the generalized double optical gating, we demonstrate that single isolated attosecond pulses can be generated with any arbitrary carrier-envelope phase value of the driving laser. The carrier-envelope phase only affects the photon flux, not the pulse duration or contrast. Our results show that isolated attosecond pulses can be generated using carrier-envelope phase unstabilized 23 fs pulses directly from chirped pulse amplifiers.

Direct writing of continuous and discontinuous sub-wavelength periodic surface structures on single-crystalline silicon using femtosecond laser

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

Kuladeep, Rajamudili; Sahoo, Chakradhar; Narayana Rao, Desai, E-mail: dnrsp@uohyd.ernet.in, E-mail: dnr-laserlab@yahoo.com

Laser-induced ripples or uniform arrays of continuous near sub-wavelength or discontinuous deep sub-wavelength structures are formed on single-crystalline silicon (Si) by femtosecond (fs) laser direct writing technique. Laser irradiation was performed on Si wafers at normal incidence in air and by immersing them in dimethyl sulfoxide using linearly polarized Ti:sapphire fs laser pulses of ∼110 fs pulse duration and ∼800 nm wavelength. Morphology studies of laser written surfaces reveal that sub-wavelength features are oriented perpendicular to laser polarization, while their morphology and spatial periodicity depend on the surrounding dielectric medium. The formation mechanism of the sub-wavelength features is explained by interferencemore » of incident laser with surface plasmon polaritons. This work proves the feasibility of fs laser direct writing technique for the fabrication of sub-wavelength features, which could help in fabrication of advanced electro-optic devices.« less

Detection of carbon monoxide (CO) in sooting hydrocarbon flames using femtosecond two-photon laser-induced fluorescence (fs-TPLIF)

NASA Astrophysics Data System (ADS)

Wang, Yejun; Kulatilaka, Waruna D.

2018-01-01

Ultrashort-pulse, femtosecond (fs)-duration, two-photon laser-induced fluorescence (fs-TPLIF) measurements of carbon monoxide (CO) are reported in rich, sooting hydrocarbon flames. CO-TPLIF detection using conventional nanosecond or picosecond lasers are often plagued by photochemical interferences, specifically under fuel-rich flames conditions. In the current study, we investigate the commonly used CO two-photon excitation scheme of the B1Σ+ ← X1Σ+ electronic transition, using approximately 100-fs-duration excitation pulses. Fluorescence emission was observed in the Ångström band originating from directly populated B1Σ+ upper state, as well as, in the third positive band from collisionally populated b3Σ+ upper state. The current work was focused on the Ångström band emission. Interference from nascent C2 emissions originating from hot soot particles in the flame could be reduced to a negligible level using a narrower detection gate width. In contrast, avoiding interferences from laser-generated C2 Swan-band emissions required specific narrowband spectral filtering in sooting flame conditions. The observed less than quadratic laser pulse energy dependence of the TPLIF signal suggests the presence of strong three-photon ionization and stimulated emission processes. In a range of CH4/air and C2H4/air premixed flames investigated, the measured CO fluorescence signals agree well with the calculated equilibrium CO number densities. Reduced-interference CO-TPLIF imaging in premixed C2H4/O2/N2 jet flames is also reported.

Ultrafast Imaging of Electronic Motion in Atoms and Molecules

DTIC Science & Technology

2016-01-12

pulses were measured with a home-made faraday cup and laser-triggered streak camera, respectively. Both are retractable and can measure the beam in...100 fs. The charge and duration of the electron pulses were measured with a home-made faraday cup and laser-triggered streak camera, respectively... faraday cup and laser-triggered streak camera, respectively. Both are retractable and can measure the beam in-situ. The gun was shown to generate pulses

Intense, carrier frequency and bandwidth tunable quasi single-cycle pulses from an organic emitter covering the Terahertz frequency gap

PubMed Central

Vicario, C.; Monoszlai, B.; Jazbinsek, M.; Lee, S. -H.; Kwon, O. -P.; Hauri, C. P.

2015-01-01

In Terahertz (THz) science, one of the long-standing challenges has been the formation of spectrally dense, single-cycle pulses with tunable duration and spectrum across the frequency range of 0.1–15 THz (THz gap). This frequency band, lying between the electronically and optically accessible spectra hosts important molecular fingerprints and collective modes which cannot be fully controlled by present strong-field THz sources. We present a method that provides powerful single-cycle THz pulses in the THz gap with a stable absolute phase whose duration can be continuously selected between 68 fs and 1100 fs. The loss-free and chirp-free technique is based on optical rectification of a wavelength-tunable pump pulse in the organic emitter HMQ-TMS that allows for tuning of the spectral bandwidth from 1 to more than 7 octaves over the entire THz gap. The presented source tunability of the temporal carrier frequency and spectrum expands the scope of spectrally dense THz sources to time-resolved nonlinear THz spectroscopy in the entire THz gap. This opens new opportunities towards ultrafast coherent control over matter and light. PMID:26400005

Directly driven source of multi-gigahertz, sub-picosecond optical pulses

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

Messerly, Michael J.; Dawson, Jay W.; Barty, Christopher P.J.

2015-10-20

A robust, compact optical pulse train source is described, with the capability of generating sub-picosecond micro-pulse sequences, which can be periodic as well as non-periodic, and at repetition rates tunable over decades of baseline frequencies, from MHz to multi-GHz regimes. The micro-pulses can be precisely controlled and formatted to be in the range of many ps in duration to as short as several fs in duration. The system output can be comprised of a continuous wave train of optical micro-pulses or can be programmed to provide gated bursts of macro-pulses, with each macro-pulse consisting of a specific number of micro-pulsesmore » or a single pulse picked from the higher frequency train at a repetition rate lower than the baseline frequency. These pulses could then be amplified in energy anywhere from the nJ to MJ range.« less

Time-Space Position of Warm Dense Matter in Laser Plasma Interaction Process

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

Cao, L F; Uschmann, I; Forster, E

2006-09-25

Laser plasma interaction experiments have been perform performed using an fs Titanium Sapphire laser. Plasmas have been generated from planar PMMA targets using single laser pulses with 3.3 mJ pulse energy, 50 fs pulse duration at 800 nm wavelength. Electron density distributions of the plasmas in different delay times have been characterized by means of Nomarski Interferometry. Experimental data were cautiously compared with relevant 1D numerical simulation. Finally these results provide a first experience of searching for the time-space position of the so-called warm dense plasma in an ultra fast laser target interaction process. These experiments aim to prepare nearmore » solid-density plasmas for Thomson scattering experiments using the short wavelength free-electron laser FLASH, DESY Hamburg.« less

Combined Yb/Nd driver for optical parametric chirped pulse amplifiers.

PubMed

Michailovas, Kirilas; Baltuska, Andrius; Pugzlys, Audrius; Smilgevicius, Valerijus; Michailovas, Andrejus; Zaukevicius, Audrius; Danilevicius, Rokas; Frankinas, Saulius; Rusteika, Nerijus

2016-09-19

We report on the developed front-end/pump system for optical parametric chirped pulse amplifiers. The system is based on a dual output fiber oscillator/power amplifier which seeds and assures all-optical synchronization of femtosecond Yb and picosecond Nd laser amplifiers operating at a central wavelength of 1030 nm and 1064 nm, respectively. At the central wavelength of 1030 nm, the fiber oscillator generates partially stretched 4 ps pulses with the spectrum supporting a <120 fs pulse duration and pulse energy of 0.45 nJ. The energy of generated 1064 nm pulses is 0.15 nJ, which is sufficient for the efficient seeding of high-contrast Nd:YVO chirped pulse regenerative amplifier/post amplifier systems generating 9 mJ pulses compressible to 16 ps duration. The power amplification stages, based on Nd:YAG crystals, provide 62 mJ pulses compressible to 20 ps pulse duration at a repetition rate of 1 kHz. Further energy scaling currently is prevented by limited dimensions of the diffraction gratings, which, because of the fast progress in MLD grating manufacturing technologies is only a temporary obstacle.

Ultrafast saturable absorption in TiS2 induced by non-equilibrium electrons and the generation of a femtosecond mode-locked laser.

PubMed

Tian, Xiangling; Wei, Rongfei; Liu, Meng; Zhu, Chunhui; Luo, Zhichao; Wang, Fengqiu; Qiu, Jianrong

2018-05-24

Non-equilibrium electrons induced by ultrafast laser excitation in a correlated electron material can disturb the Fermi energy as well as optical nonlinearity. Here, non-equilibrium electrons translate a semiconductor TiS2 material into a plasma to generate broad band nonlinear optical saturable absorption with a sub-picosecond recovery time of ∼768 fs (corresponding to modulation frequencies over 1.3 THz) and a modulation response up to ∼145%. Based on this optical nonlinear modulator, a stable femtosecond mode-locked pulse with a pulse duration of ∼402 fs and a pulse train with a period of ∼175.5 ns is observed in the all-optical system. The findings indicate that non-equilibrium electrons can promote a TiS2-based saturable absorber to be an ultrafast switch for a femtosecond pulse output.

Dynamics of femtosecond laser-induced periodic surface structures on silicon by high spatial and temporal resolution imaging

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

Jia, X., E-mail: jiaxin@sdju.edu.cn; Department of Mathematics and Physics, Shanghai Dianji University, Shanghai 201306; Jia, T. Q., E-mail: tqjia@phy.ecnu.edu.cn

2014-04-14

The formation dynamics of periodic ripples induced by femtosecond laser pulses (pulse duration τ = 50 fs and central wavelength λ = 800 nm) are studied by a collinear pump-probe imaging technique with a temporal resolution of 1 ps and a spatial resolution of 440 nm. The ripples with periods close to the laser wavelength begin to appear upon irradiation of two pump pulses at surface defects produced by the prior one. The rudiments of periodic ripples emerge in the initial tens of picoseconds after fs laser irradiation, and the ripple positions keep unmoved until the formation processes complete mainly in a temporal span of 1500 ps. Themore » results suggest that the periodic deposition of laser energy during the interaction between femtosecond laser pulses and sample surface plays a dominant role in the formation of periodic ripples.« less

Development of experimental techniques for the characterization of ultrashort photon pulses of extreme ultraviolet free-electron lasers

NASA Astrophysics Data System (ADS)

Düsterer, S.; Rehders, M.; Al-Shemmary, A.; Behrens, C.; Brenner, G.; Brovko, O.; DellAngela, M.; Drescher, M.; Faatz, B.; Feldhaus, J.; Frühling, U.; Gerasimova, N.; Gerken, N.; Gerth, C.; Golz, T.; Grebentsov, A.; Hass, E.; Honkavaara, K.; Kocharian, V.; Kurka, M.; Limberg, Th.; Mitzner, R.; Moshammer, R.; Plönjes, E.; Richter, M.; Rönsch-Schulenburg, J.; Rudenko, A.; Schlarb, H.; Schmidt, B.; Senftleben, A.; Schneidmiller, E. A.; Siemer, B.; Sorgenfrei, F.; Sorokin, A. A.; Stojanovic, N.; Tiedtke, K.; Treusch, R.; Vogt, M.; Wieland, M.; Wurth, W.; Wesch, S.; Yan, M.; Yurkov, M. V.; Zacharias, H.; Schreiber, S.

2014-12-01

One of the most challenging tasks for extreme ultraviolet, soft and hard x-ray free-electron laser photon diagnostics is the precise determination of the photon pulse duration, which is typically in the sub 100 fs range. Nine different methods, able to determine such ultrashort photon pulse durations, were compared experimentally at FLASH, the self-amplified spontaneous emission free-electron laser at DESY in Hamburg, in order to identify advantages and disadvantages of different methods. Radiation pulses at a wavelength of 13.5 and 24.0 nm together with the corresponding electron bunch duration were measured by indirect methods like analyzing spectral correlations, statistical fluctuations, and energy modulations of the electron bunch and also by direct methods like autocorrelation techniques, terahertz streaking, or reflectivity changes of solid state samples. In this paper, we present a comprehensive overview of the various techniques and a comparison of the individual experimental results. The information gained is of utmost importance for the future development of reliable pulse duration monitors indispensable for successful experiments with ultrashort extreme ultraviolet pulses.

Widely tunable 11 GHz femtosecond fiber laser based on a nonmode-locked source [Widely tunable 11 GHz femtosecond fiber laser based on a non-modelocked source

DOE PAGES

Prantil, Matthew A.; Cormier, Eric; Dawson, Jay W.; ...

2013-08-19

An 11 GHz fiber laser built on a modulated CW platform is described and characterized. This compact, vibrationinsensitive, fiber based system can be operated at wavelengths compatible with high energy fiber technology, is driven by an RF signal directly, and is tunable over a wide range of drive frequencies. The demonstration system when operated at 1040 nm is capable of 50 ns bursts of 575 micro-pulses produced at a macro-pulse rate of 83 kHz where the macro-pulse and micro-pulse energies are 1.8 μJ and 3.2 nJ respectively. Micro-pulse durations of 850 fs are demonstrated. Finally, we discuss extensions to shortermore » duration.« less

Chirped pulse Raman amplification in warm plasma: towards controlling saturation

PubMed Central

Yang, X.; Vieux, G.; Brunetti, E.; Ersfeld, B.; Farmer, J. P.; Hur, M. S.; Issac, R. C.; Raj, G.; Wiggins, S. M.; Welsh, G. H.; Yoffe, S. R.; Jaroszynski, D. A.

2015-01-01

Stimulated Raman backscattering in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers because plasma is fully broken down and withstands extremely high electric fields. Plasma also has unique nonlinear optical properties that allow simultaneous compression of optical pulses to ultra-short durations. However, current measured efficiencies are limited to several percent. Here we investigate Raman amplification of short duration seed pulses with different chirp rates using a chirped pump pulse in a preformed plasma waveguide. We identify electron trapping and wavebreaking as the main saturation mechanisms, which lead to spectral broadening and gain saturation when the seed reaches several millijoules for durations of 10’s – 100’s fs for 250 ps, 800 nm chirped pump pulses. We show that this prevents access to the nonlinear regime and limits the efficiency, and interpret the experimental results using slowly-varying-amplitude, current-averaged particle-in-cell simulations. We also propose methods for achieving higher efficiencies. PMID:26290153

Design and calibration of zero-additional-phase SPIDER

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

Baum, Peter; Riedle, Eberhard

2005-09-01

Zero-additional-phase spectral phase interferometry for direct electric field reconstruction (ZAP-SPIDER) is a novel technique for measuring the temporal shape and phase of ultrashort optical pulses directly at the interaction point of a spectroscopic experiment. The scheme is suitable for an extremely wide wavelength region from the ultraviolet to the near infrared. We present a comprehensive description of the experimental setup and design guidelines to effectively apply the technique to various wavelengths and pulse durations. The calibration of the setup and procedures to check the consistency of the measurement are discussed in detail. We show experimental data for various center wavelengthsmore » and pulse durations down to 7 fs to verify the applicability to a wide range of pulse parameters.« less

Instrumental development of a quasi-relativistic ultrashort electron beam source for electron diffractions and spectroscopies

NASA Astrophysics Data System (ADS)

Shin, Young-Min; Figora, Michael

2017-10-01

A stable femtosecond electron beam system has been configured for time-resolved pump-probe experiments. The ultrafast electron diffraction (UED) system is designed with a sub-MeV photoelectron beam source pulsed by a femtosecond UV laser and nondispersive beamline components, including a bunch compressor—a pulsed S-band klystron is installed and fully commissioned with 5.5 MW peak power in a 2.5 μs pulse length. A single-cell RF photo-gun is designed to produce 1.6-16 pC electron bunches in a photoemission mode with 150 fs pulse duration at 0.5-1 MeV. The measured RF system jitters are within 1% in magnitude and 0.2° in phase, which would induce 3.4 keV and 0.25 keV of ΔE, corresponding to 80 fs and 5 fs of Δt, respectively. Our particle-in-cell simulations indicate that the designed bunch compressor reduces the time-of-arrival jitter by about an order of magnitude. The transport and focusing optics of the designed beamline with the bunch compressor enables an energy spread within 10-4 and a bunch length (electron probe) within <500 fs. In this paper, the design analysis and instrumental test results are presented along with the development of the quasi-relativistic UED system.

Instrumental development of a quasi-relativistic ultrashort electron beam source for electron diffractions and spectroscopies.

PubMed

Shin, Young-Min; Figora, Michael

2017-10-01

A stable femtosecond electron beam system has been configured for time-resolved pump-probe experiments. The ultrafast electron diffraction (UED) system is designed with a sub-MeV photoelectron beam source pulsed by a femtosecond UV laser and nondispersive beamline components, including a bunch compressor-a pulsed S-band klystron is installed and fully commissioned with 5.5 MW peak power in a 2.5 μs pulse length. A single-cell RF photo-gun is designed to produce 1.6-16 pC electron bunches in a photoemission mode with 150 fs pulse duration at 0.5-1 MeV. The measured RF system jitters are within 1% in magnitude and 0.2° in phase, which would induce 3.4 keV and 0.25 keV of ΔE, corresponding to 80 fs and 5 fs of Δt, respectively. Our particle-in-cell simulations indicate that the designed bunch compressor reduces the time-of-arrival jitter by about an order of magnitude. The transport and focusing optics of the designed beamline with the bunch compressor enables an energy spread within 10 -4 and a bunch length (electron probe) within <500 fs. In this paper, the design analysis and instrumental test results are presented along with the development of the quasi-relativistic UED system.

Propagation of ultrashort laser pulses in water: linear absorption and onset of nonlinear spectral transformation.

PubMed

Sokolov, Alexei V; Naveira, Lucas M; Poudel, Milan P; Strohaber, James; Trendafilova, Cynthia S; Buck, William C; Wang, Jieyu; Strycker, Benjamin D; Wang, Chao; Schuessler, Hans; Kolomenskii, Alexandre; Kattawar, George W

2010-01-20

We study propagation of short laser pulses through water and use a spectral hole filling technique to essentially perform a sensitive balanced comparison of absorption coefficients for pulses of different duration. This study is motivated by an alleged violation of the Bouguer-Lambert-Beer law at low light intensities, where the pulse propagation is expected to be linear, and by a possible observation of femtosecond optical precursors in water. We find that at low intensities, absorption of laser light is determined solely by its spectrum and does not directly depend on the pulse duration, in agreement with our earlier work and in contradiction to some work of others. However, as the laser fluence is increased, interaction of light with water becomes nonlinear, causing energy exchange among the pulse's spectral components and resulting in peak-intensity dependent (and therefore pulse-duration dependent) transmission. For 30 fs pulses at 800 nm center wavelength, we determine the onset of nonlinear propagation effects to occur at a peak value of about 0.12 mJ/cm(2) of input laser energy fluence.

Subpicosecond thin-disk laser oscillator with pulse energies of up to 25.9 microjoules by use of an active multipass geometry.

PubMed

Neuhaus, Joerg; Bauer, Dominik; Zhang, Jing; Killi, Alexander; Kleinbauer, Jochen; Kumkar, Malte; Weiler, Sascha; Guina, Mircea; Sutter, Dirk H; Dekorsy, Thomas

2008-12-08

The pulse shaping dynamics of a diode-pumped laser oscillator with active multipass cell was studied experimentally and numerically. We demonstrate the generation of high energy subpicosecond pulses with a pulse energy of up to 25.9 microJ at a pulse duration of 928 fs directly from a thin-disk laser oscillator. These results are achieved by employing a selfimaging active multipass geometry operated in ambient atmosphere. Stable single pulse operation has been obtained with an average output power in excess of 76 W and at a repetition rate of 2.93 MHz. Self starting passive mode locking was accomplished using a semiconductor saturable absorber mirror. The experimental results are compared with numerical simulations, showing good agreement including the appearance of Kelly sidebands. Furthermore, a modified soliton-area theorem for approximating the pulse duration is presented. (c) 2008 Optical Society of America

Optical setup for two-colour experiments at the low density matter beamline of FERMI

NASA Astrophysics Data System (ADS)

Finetti, Paola; Demidovich, Alexander; Plekan, Oksana; Di Fraia, Michele; Cucini, Riccardo; Callegari, Carlo; Cinquegrana, Paolo; Sigalotti, Paolo; Ivanov, Rosen; Danailov, Miltcho B.; Fava, Claudio; De Ninno, Giovanni; Coreno, Marcello; Grazioli, Cesare; Feifel, Raimund; Squibb, Richard J.; Mazza, Tommaso; Meyer, Michael; Prince, Kevin C.

2017-11-01

The low density matter beamline of the free electron laser facility FERMI is dedicated to the study of atomic, molecular and cluster systems, and here we describe the optical setup available for two-colour experiments. Samples can be exposed to ultrashort pulses from a Ti:Sapphire source (fundamental, or second or third harmonic), and ultrashort light pulses of FERMI in the EUV/soft x-ray region with a well-defined temporal delay, and negligible jitter (<10 fs) compared to the pulse durations (40-100 fs). Detection schemes available include electron, ion and optical spectroscopy. The majority of experiments using this apparatus are pump-and-probe, where either wavelength can be pump or probe, but the system is also useful for other techniques, such as multi-photon spectroscopy, cross-correlation measurements and alignment of molecules in space.

Femtosecond laser-induced periodic surface structure on the Ti-based nanolayered thin films

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

Petrović, Suzana M.; Gaković, B.; Peruško, D.

2013-12-21

Laser-induced periodic surface structures (LIPSSs) and chemical composition changes of Ti-based nanolayered thin films (Al/Ti, Ni/Ti) after femtosecond (fs) laser pulses action were studied. Irradiation is performed using linearly polarized Ti:Sapphire fs laser pulses of 40 fs pulse duration and 800 nm wavelength. The low spatial frequency LIPSS (LSFL), oriented perpendicular to the laser polarization with periods slightly lower than the irradiation wavelength, was typically formed at elevated laser fluences. On the contrary, high spatial frequency LIPSS (HSFL) with uniform period of 155 nm, parallel to the laser light polarization, appeared at low laser fluences, as well as in themore » wings of the Gaussian laser beam distribution for higher used fluence. LSFL formation was associated with the material ablation process and accompanied by the intense formation of nanoparticles, especially in the Ni/Ti system. The composition changes at the surface of both multilayer systems in the LSFL area indicated the intermixing between layers and the substrate. Concentration and distribution of all constitutive elements in the irradiated area with formed HSFLs were almost unchanged.« less

Intense terahertz pulses from SLAC electron beams using coherent transition radiation.

PubMed

Wu, Ziran; Fisher, Alan S; Goodfellow, John; Fuchs, Matthias; Daranciang, Dan; Hogan, Mark; Loos, Henrik; Lindenberg, Aaron

2013-02-01

SLAC has two electron accelerators, the Linac Coherent Light Source (LCLS) and the Facility for Advanced Accelerator Experimental Tests (FACET), providing high-charge, high-peak-current, femtosecond electron bunches. These characteristics are ideal for generating intense broadband terahertz (THz) pulses via coherent transition radiation. For LCLS and FACET respectively, the THz pulse duration is typically 20 and 80 fs RMS and can be tuned via the electron bunch duration; emission spectra span 3-30 THz and 0.5 THz-5 THz; and the energy in a quasi-half-cycle THz pulse is 0.2 and 0.6 mJ. The peak electric field at a THz focus has reached 4.4 GV/m (0.44 V/Å) at LCLS. This paper presents measurements of the terahertz pulses and preliminary observations of nonlinear materials response.

Optimization of the parameters for intrastromal refractive surgery with ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Heisterkamp, Alexander; Ripken, Tammo; Lubatschowski, Holger; Welling, Herbert; Dommer, Wolfgang; Luetkefels, Elke; Mamom, Thanongsak; Ertmer, Wolfgang

2001-06-01

Focussing femtosecond laser pulses into a transparent media, such as corneal tissue, leads to optical breakdown, generation of a micro-plasma and, thus, a cutting effect inside the tissue. To proof the potential of fs-lasers in refractive surgery, three-dimensional cutting within the corneal stroma was evaluated. With the use of ultrashort laser pulses within the LASIK procedure (laser in situ keratomileusis) possible complications in handling of a mechanical knife, the microkeratome, can be reduced by using the treatment laser as the keratome itself. To study woundhealing effects, animal studies were carried out in rabbit specimen. The surgical outcome was analyzed by means of histological sections, as well as light and scanning electron microscopy. Dependencies on the dispersion caused by focussing optics were evaluated and optimized. Thus, pulse energies well below 1 (mu) J were sufficient to perform the intrastromal cuts. The laser pulses with a duration of 180 fs and energies of 0.5-100 (mu) J were provided by a modelocked frequency doubled erbium fiber-laser with subsequent chirped pulse amplification in a titanium sapphire amplifier at up to 3 kHz.

TW-class hollow-fiber compressor with tunable pulse duration (Conference Presentation)

NASA Astrophysics Data System (ADS)

Boehle, Frederik; Vernier, Aline; Kretschmar, Martin; Jullien, Aurélie; Kovacs, Mate; Romero, Rosa M.; Crespo, Helder M.; Simon, Peter; Nagy, Tamas; Lopez-Martens, Rodrigo

2017-05-01

CEP-stable few-cycle light pulses find numerous applications in attosecond science, most notably the production of isolated attosecond pulses for studying ultrafast electronic processes in matter [1]. Scaling up the pulse energy of few-cycle pulses could extend the scope of applications to even higher intensity processes, such as attosecond dynamics of relativistic plasma mirrors [2]. Hollow fiber compressors are widely used to produce few-cycle pulses with excellent spatiotemporal quality [3], where octave-spanning broadened spectra can be temporally compressed to sub-2-cycle duration [4,5]. Several tricks help increase the output energy: using circularly polarized light [6], applying a pressure gradient along the fiber [7] or even temporal multiplexing [8]. The highest pulse energy of 5 mJ at 5 fs pulse duration was achieved by using a hollow fiber in pressure gradient mode [9] but in this case no CEP stabilization was achieved, which is crucial for most applications of few-cycle pulses. Nevertheless, it did show that in order to scale up the peak power, the effective length and area mode of the fiber had to be increased proportionally, thereby requiring the use of longer waveguides with larger apertures. Thanks to an innovative design utilizing stretched flexible capillaries [10], we recently demonstrated the generation CEP-stable sub-4fs pulses with 3mJ energy using a 2m length 450mm bore hollow fiber in pressure gradient mode [11]. Here, we show that a stretched hollow-fiber compressor operated in pressure gradient mode can generate relativistic intensity pulses with continuously tunable waveform down to almost a single cycle (3.5fs at 750nm central wavelength). The pulses are characterized online using an integrated d-scan device directly under vacuum [12]. While the pulse shape is tuned, all other pulse characteristics, such as energy, pointing stability and focal distribution remain the same on target, making it possible to explore the dynamics of plasma mirrors using controllable relativistic-intensity light waveforms at 1kHz. [1] Krausz and Ivanov, Rev. Mod. Phys. 81, 163 (2009). [2] Borot et al., Nature Phys. 8, 417-421 (2012). [3] Nisoli et al., Appl. Phys. Lett. 68, 2793-2795 (1996). [4] Park et al., Opt. Lett. 34, 2342-2344 (2009). [5] Schweinberger et al., Opt. Lett. 37, 3573-5 (2012). [6] Chen et al., Opt. Lett. 34, 1588-1590 (2009). [7] Suda et al., Appl. Phys. Lett. 86, 111116 (2005). [8] Jacqmin et al., Opt. Lett. 40, 709-712 (2015) [9] Bohman et al., Opt. Lett. 35, 1887-9 (2010). [10] Nagy et al., Appl. Opt. 47, 3264-3268 (2008). [11] Boehle et al., Las. Phys. Lett. 11, 095401 (2014). [12] Miranda et al., Opt. Express 20, 18732-43 (2012)

Strong electromagnetic pulses generated in high-intensity short-pulse laser interactions with thin foil targets

NASA Astrophysics Data System (ADS)

Rączka, P.; Dubois, J.-L.; Hulin, S.; Tikhonchuk, V.; Rosiński, M.; Zaraś-Szydłowska, A.; Badziak, J.

2017-12-01

Measurements are reported of the target neutralization current, the target charge, and the tangential component of the magnetic field generated as a result of laser-target interaction by pulses with the energy in the range of 45 mJ to 92 mJ on target and the pulse duration from 39 fs to 1000 fs. The experiment was performed at the Eclipse facility in CELIA, Bordeaux. The aim of the experiment was to extend investigations performed for the thick (mm scale) targets to the case of thin (micrometer thickness) targets in a way that would allow for a straightforward comparison of the results. We found that thin foil targets tend to generate 20 to 50 percent higher neutralization current and the target charge than the thick targets. The measurement of the tangential component of the magnetic field had shown that the initial spike is dominated by the 1 ns pulse consistent with the 1 ns pulse of the neutralization current, but there are some differences between targets of different type on sub-ns scale, which is an effect going beyond a simple picture of the target acting as an antenna. The sub-ns structure appears to be reproducible to surprising degree. We found that there is in general a linear correlation between the maximum value of the magnetic field and the maximum neutralization current, which supports the target-antenna picture, except for pulses hundreds of fs long.

Diode-pumped Kerr-lens mode-locked Yb:CaGdAlO4 laser with tunable wavelength

NASA Astrophysics Data System (ADS)

Gao, Ziye; Zhu, Jiangfeng; Wang, Junli; Wang, Zhaohua; Wei, Zhiyi; Xu, Xiaodong; Zheng, Lihe; Su, Liangbi; Xu, Jun

2016-01-01

We experimentally demonstrated a wavelength tunable Kerr-lens mode-locked femtosecond laser based on an Yb:CaGdAlO4 (Yb:CGA) crystal. The Kerr-lens mode-locked wavelength tuning range was from 1043.5 to 1076 nm, as broad as 32.5 nm, by slightly tilting the end mirror. Pulses as short as 60 fs were generated at the central wavelength of 1043.8 nm with an average output power of 66 mW. By using an output coupler with 1.5% transmittance, the Kerr-lens mode-locked average output power reached 127 mW with a pulse duration of 81 fs at a central wavelength of 1049.5 nm.

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

NASA Astrophysics Data System (ADS)

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

2017-05-01

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

Mode locking of a ring cavity semiconductor diode laser

NASA Astrophysics Data System (ADS)

Desbiens, Louis; Yesayan, Ararat; Piche, Michel

2000-12-01

We report new results on the generation and characterization of picosecond pulses from a self-mode-locked semiconductor diode laser. The active medium (InGaAs, 830-870 nm) is a semiconductor optical amplifier whose facets are cut at angle and AR coated. The amplifier is inserted in a three-minor ring cavity. Mode locking is purely passive; it takes place for specific alignment conditions. Trains of counterpropagating pulses are produced, with pulse duration varying from 1 .2 to 2 ps. The spectra of the counterpropagatmg pulses do not fully overlap; their central wavelengths differ by a few nm. The pulse repetition rate has been varied from 0.3 to 3 GHz. The pulses have been compressed to less than 500-fs duration with a grating pair. We discuss some of the potential physical mechanisms that could be involved in the dynamics of the mode-locked regime. Hysteresis in the LI curve has been observed. To characterize the pulses, we introduce the idea of a Pulse Quality Factor, where the pulse duration and spectral width are calculated from the second-order moments of the measured intensity autocorrelation and power spectral density.

Towards shot-noise limited diffraction experiments with table-top femtosecond hard x-ray sources.

PubMed

Holtz, Marcel; Hauf, Christoph; Weisshaupt, Jannick; Salvador, Antonio-Andres Hernandez; Woerner, Michael; Elsaesser, Thomas

2017-09-01

Table-top laser-driven hard x-ray sources with kilohertz repetition rates are an attractive alternative to large-scale accelerator-based systems and have found widespread applications in x-ray studies of ultrafast structural dynamics. Hard x-ray pulses of 100 fs duration have been generated at the Cu K α wavelength with a photon flux of up to 10 9 photons per pulse into the full solid angle, perfectly synchronized to the sub-100-fs optical pulses from the driving laser system. Based on spontaneous x-ray emission, such sources display a particular noise behavior which impacts the sensitivity of x-ray diffraction experiments. We present a detailed analysis of the photon statistics and temporal fluctuations of the x-ray flux, together with experimental strategies to optimize the sensitivity of optical pump/x-ray probe experiments. We demonstrate measurements close to the shot-noise limit of the x-ray source.

Towards shot-noise limited diffraction experiments with table-top femtosecond hard x-ray sources

PubMed Central

Holtz, Marcel; Hauf, Christoph; Weisshaupt, Jannick; Salvador, Antonio-Andres Hernandez; Woerner, Michael; Elsaesser, Thomas

2017-01-01

Table-top laser-driven hard x-ray sources with kilohertz repetition rates are an attractive alternative to large-scale accelerator-based systems and have found widespread applications in x-ray studies of ultrafast structural dynamics. Hard x-ray pulses of 100 fs duration have been generated at the Cu Kα wavelength with a photon flux of up to 109 photons per pulse into the full solid angle, perfectly synchronized to the sub-100-fs optical pulses from the driving laser system. Based on spontaneous x-ray emission, such sources display a particular noise behavior which impacts the sensitivity of x-ray diffraction experiments. We present a detailed analysis of the photon statistics and temporal fluctuations of the x-ray flux, together with experimental strategies to optimize the sensitivity of optical pump/x-ray probe experiments. We demonstrate measurements close to the shot-noise limit of the x-ray source. PMID:28795079

Nanosurgery of cells and chromosomes using near-infrared twelve-femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Uchugonova, Aisada; Lessel, Matthias; Nietzsche, Sander; Zeitz, Christian; Jacobs, Karin; Lemke, Cornelius; König, Karsten

2012-10-01

Laser-assisted surgery based on multiphoton absorption of near-infrared laser light has great potential for high precision surgery at various depths within the cells and tissues. Clinical applications include refractive surgery (fs-LASIK). The non-contact laser method also supports contamination-free cell nanosurgery. In this paper we describe usage of an ultrashort femtosecond laser scanning microscope for sub-100 nm surgery of human cells and metaphase chromosomes. A mode-locked 85 MHz Ti:Sapphire laser with an M-shaped ultrabroad band spectrum (maxima: 770 nm/830 nm) and an in situ pulse duration at the target ranging from 12 fs up to 3 ps was employed. The effects of laser nanoprocessing in cells and chromosomes have been quantified by atomic force microscopy. These studies demonstrate the potential of extreme ultrashort femtosecond laser pulses at low mean milliwatt powers for sub-100 nm surgery of cells and cellular organelles.

Space-Time Characterization of Laser Plasma Interactions in the Warm Dense Matter Regime

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

Cao, L F; Uschmann, I; Forster, E

2008-04-30

Laser plasma interaction experiments have been performed using a fs Titanium Sapphire laser. Plasmas have been generated from planar PMMA targets using single laser pulses with 3.3 mJ pulse energy, 50 fs pulse duration at 800 nm wavelength. The electron density distributions of the plasmas in different delay times have been characterized by means of Nomarski Interferometry. Experimental data were compared with hydrodynamic simulation. First results to characterize the plasma density and temperature as a function of space and time are obtained. This work aims to generate plasmas in the warm dense matter (WDM) regime at near solid-density in anmore » ultra-fast laser target interaction process. Plasmas under these conditions can serve as targets to develop x-ray Thomson scattering as a plasma diagnostic tool, e.g., using the VUV free-electron laser (FLASH) at DESY Hamburg.« less

Electron diffraction using ultrafast electron bunches from a laser-wakefield accelerator at kHz repetition rate

NASA Astrophysics Data System (ADS)

He, Z.-H.; Thomas, A. G. R.; Beaurepaire, B.; Nees, J. A.; Hou, B.; Malka, V.; Krushelnick, K.; Faure, J.

2013-02-01

We show that electron bunches in the 50-100 keV range can be produced from a laser wakefield accelerator using 10 mJ, 35 fs laser pulses operating at 0.5 kHz. It is shown that using a solenoid magnetic lens, the electron bunch distribution can be shaped. The resulting transverse and longitudinal coherence is suitable for producing diffraction images from a polycrystalline 10 nm aluminum foil. The high repetition rate, the stability of the electron source, and the fact that its uncorrelated bunch duration is below 100 fs make this approach promising for the development of sub-100 fs ultrafast electron diffraction experiments.

Demonstration of periodic nanostructure formation with less ablation by double-pulse laser irradiation on titanium

NASA Astrophysics Data System (ADS)

Furukawa, Yuki; Sakata, Ryoichi; Konishi, Kazuki; Ono, Koki; Matsuoka, Shusaku; Watanabe, Kota; Inoue, Shunsuke; Hashida, Masaki; Sakabe, Shuji

2016-06-01

By pairing femtosecond laser pulses (duration ˜40 fs and central wavelength ˜810 nm) at an appropriate time interval, a laser-induced periodic surface structure (LIPSS) is formed with much less ablation than one formed with a single pulse. On a titanium plate, a pair of laser pulses with fluences of 70 and 140 mJ/cm2 and a rather large time interval (>10 ps) creates a LIPSS with an interspace of 600 nm, the same as that formed by a single pulse of 210 mJ/cm2, while the double pulse ablates only 4 nm, a quarter of the ablation depth of a single pulse.

Enhancement cavities for zero-offset-frequency pulse trains.

PubMed

Holzberger, S; Lilienfein, N; Trubetskov, M; Carstens, H; Lücking, F; Pervak, V; Krausz, F; Pupeza, I

2015-05-15

The optimal enhancement of broadband optical pulses in a passive resonator requires a seeding pulse train with a specific carrier-envelope-offset frequency. Here, we control the phase of the cavity mirrors to tune the offset frequency for which a given comb is optimally enhanced. This enables the enhancement of a zero-offset-frequency train of sub-30-fs pulses to multi-kW average powers. The combination of pulse duration, power, and zero phase slip constitutes a crucial step toward the generation of attosecond pulses at multi-10-MHz repetition rates. In addition, this control affords the enhancement of pulses generated by difference-frequency mixing, e.g., for mid-infrared spectroscopy.

Bright betatron X-ray radiation from a laser-driven-clustering gas target

PubMed Central

Chen, L. M.; Yan, W. C.; Li, D. Z.; Hu, Z. D.; Zhang, L.; Wang, W. M.; Hafz, N.; Mao, J. Y.; Huang, K.; Ma, Y.; Zhao, J. R.; Ma, J. L.; Li, Y. T.; Lu, X.; Sheng, Z. M.; Wei, Z. Y.; Gao, J.; Zhang, J.

2013-01-01

Hard X-ray sources from femtosecond (fs) laser-produced plasmas, including the betatron X-rays from laser wakefield-accelerated electrons, have compact sizes, fs pulse duration and fs pump-probe capability, making it promising for wide use in material and biological sciences. Currently the main problem with such betatron X-ray sources is the limited average flux even with ultra-intense laser pulses. Here, we report ultra-bright betatron X-rays can be generated using a clustering gas jet target irradiated with a small size laser, where a ten-fold enhancement of the X-ray yield is achieved compared to the results obtained using a gas target. We suggest the increased X-ray photon is due to the existence of clusters in the gas, which results in increased total electron charge trapped for acceleration and larger wiggling amplitudes during the acceleration. This observation opens a route to produce high betatron average flux using small but high repetition rate laser facilities for applications. PMID:23715033

Design and performance of an astigmatism-compensated self-mode-locked ring-cavity Ti:sapphire laser

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

Shen, Y.; Dai, J.; Wang, Q.

1996-12-31

Based on the nonlinear ABCD matrix and the renormalized q-parameter for Gaussian-beam propagation, self-focusing in conjunction with a spatial gain profile for self-mode locking in a ring-cavity Ti:sapphire laser is analyzed. In the experiment, an astigmatism-compensated self-mode-locked ring-cavity Ti:sapphire laser is demonstrated, and self-mode-locked operation is achieved in both bidirection and unidirection with pulse durations as short as 36 fs and 32 fs, respectively. The experimental observations are in good agreement with theoretical predictions.

Influence of dispersion stretching of ultrashort UV laser pulse on the critical power for self-focusing

NASA Astrophysics Data System (ADS)

Ionin, A. A.; Mokrousova, D. V.; Piterimov, D. A.; Seleznev, L. V.; Sinitsyn, D. V.; Sunchugasheva, E. S.

2018-04-01

The critical power for self-focusing in air for ultrashort ultraviolet laser pulses, stretched due to dispersion from 90 to 730 fs, was experimentally measured. It was shown that the pulse duration enhancement due to its propagation in condensed media leads to an almost linear decrease in the critical power for self-focusing. It was also observed that when the pulse peak power exceeds the critical one, the maximum of linear plasma distribution along the ultraviolet laser filament does not shift in the direction opposite to the laser pulse propagation, as observed for infrared laser filaments, but remains at the geometrical focus.

Carrier-envelope-offset phase control of ultrafast optical rectification in resonantly excited semiconductors.

PubMed

Van Vlack, C; Hughes, S

2007-04-20

Ultrashort pulse light-matter interactions in a semiconductor are investigated within the regime of resonant optical rectification. Using pulse envelope areas of around 1.5-3.5 pi, a single-shot dependence on carrier-envelope-offset phase (CEP) is demonstrated for 5 fs pulse durations. A characteristic phase map is predicted for several different frequency regimes using parameters for thin-film GaAs. We subsequently suggest a possible technique to extract the CEP, in both sign and amplitude, using a solid state detector.

Optimization of interaction conditions for efficient short laser pulse amplification by stimulated Brillouin scattering in the strongly coupled regime

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

Chiaramello, M.; Riconda, C.; Amiranoff, F.

Plasma amplification of low energy, a short (∼100–500 fs) laser pulse by an energetic long (∼10 ps) pulse via strong coupling Stimulated Brillouin Backscattering is investigated with an extensive analysis of one-dimensional particle-in-cell simulations. Parameters relevant to nowadays experimental conditions are investigated. The obtained seed pulse spectra are analyzed as a function of the interaction conditions such as plasma profile, pulses delay, and seed or pulse duration. The factors affecting the amount of energy transferred are determined, and the competition between Brillouin-based amplification and parasitic Raman backscattering is analyzed, leading to the optimization of the interaction conditions.

Characteristics of light reflected from a dense ionization wave with a tunable velocity.

PubMed

Zhidkov, A; Esirkepov, T; Fujii, T; Nemoto, K; Koga, J; Bulanov, S V

2009-11-20

An optically dense ionization wave (IW) produced by two femtosecond (approximately 10/30 fs) laser pulses focused cylindrically and crossing each other may become an efficient coherent x-ray converter in accordance with the Semenova-Lampe theory. The resulting velocity of a quasiplane IW in the vicinity of pulse intersection changes with the angle between the pulses from the group velocity of ionizing pulses to infinity allowing a tuning of the wavelength of x rays and their bunching. The x-ray spectra after scattering of a lower frequency and long coherent light pulse change from the monochromatic to high order harmoniclike with the duration of the ionizing pulses.

Femtosecond pulses generated from a synchronously pumped chromium-doped forsterite laser

NASA Technical Reports Server (NTRS)

Seas, A.; Petricevic, V.; Alfano, R. R.

1993-01-01

Kerr lens mode-locking (KLM) has become a standard method to produce femtosecond pulses from tunable solid state lasers. High power inside the laser resonator propagating through the laser-medium with nonlinear index of refraction, coupled with the stability conditions of the laser modes in the resonator, result in a passive amplitude modulation which explains the mechanism for pulse shortening. Recently, chromium doped forsterite was shown to exhibit similar pulse behavior. A successful attempt to generate femtosecond pulses from a synchronously pumped chromium-doped forsterite laser with intracavity dispersion compensation is reported. Stable, transform limited pulses with duration of 105 fs were routinely generated, tunable between 1240 to 1270 nm.

Tunable femtosecond near-infrared source based on a Yb:LYSO-laser-pumped optical parametric oscillator

NASA Astrophysics Data System (ADS)

Wen-Long, Tian; Zhao-Hua, Wang; Jiang-Feng, Zhu; Zhi-Yi, Wei

2016-01-01

We demonstrate a widely tunable near-infrared source from 767 nm to 874 nm generated by the intracavity second harmonic generation (SHG) in an optical parametric oscillator pumped by a Yb:LYSO solid-state laser. The home-made Yb:LYSO oscillator centered at 1035 nm delivers an average power of 2 W and a pulse duration as short as 351 fs. Two MgO doped periodically poled lithium niobates (MgO:PPLN) with grating periods of 28.5-31.5 μm in steps of 0.5 μm and 19.5-21.3 μm in steps of 0.2 μm are used for the OPO and intracavity SHG, respectively. The maximum average output power of 180 mW at 798 nm was obtained and the output pulses have pulse duration of 313 fs at 792 nm if a sech2-pulse shape was assumed. In addition, tunable signal femtosecond pulses from 1428 nm to 1763 nm are also realized with the maximum average power of 355 mW at 1628 nm. Project supported by the National Key Basic Research Program of China (Grant No. 2013CB922402), the National Key Scientific Instruments Development Program of China (Grant No. 2012YQ120047), the National Natural Science Foundation of China (Grant Nos. 61205130 and 11174361), and the Key Deployment Project of Chinese Academy of Sciences (Grant No. KJZD-EW-L11-03).

Development of an applicator for multiphoton PDT

NASA Astrophysics Data System (ADS)

Graschew, Georgi; Bastian, Matthias; Rakowsky, Stefan; Roelofs, Theo A.; Balanos, Evangelos; Schlag, Peter M.; Steinmeyer, Gunter; Elsaesser, Thomas

2004-09-01

Multiphoton excitation of photosensitizers for laser induced fluorescence diagnosis (LIFD) and photodynamic therapy (PDT) of tumors has the advantage of greater tissue penetration due to the longer wavelength of irradiation. However, multiphoton LIFD and PDT are presently not clinically applicable as there are no applicators available for the delivery of the pulsed laser radiation to the operating room. As an approach, in this contribution the beam delivery through photonic crystal fibers has been investigated. Pulses of a Ti:sapphire laser of 100 fs pulse duration and an average power of 150 mW have been transported through such a fiber of 25 m length and the resulting pulses show the absence of nonlinear contributions but still a broadening of the pulse to 2 ps due to the dispersion of the fiber. It is planned to compensate this broadening by a grating in front of the fiber. Alternatively, the transport of laser radiation of 150 fs and 100 mW through a mirror-joint-arm used for conventional CO2 lasers has been tested showing no broadening of the laser pulses. Two-photon photodynamic activity of mTHPC-CMPEG4 shall serve as a test of the laser light transport system.

Multi-mJ energy extraction using Yb-fiber based coherent pulse stacking amplification of fs pulses (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ruppe, John M.; Pei, Hanzhang; Chen, Siyun; Sheikhsofla, Morteza; Wilcox, Russell B.; Nees, John A.; Galvanauskas, Almantas

2017-03-01

We report multi-mJ energy (>5mJ) extraction from femtosecond-pulse Yb-doped fiber CPA using coherent pulse stacking amplification (CPSA) technique. This high energy extraction has been enabled by amplifying 10's of nanosecond long pulse sequence, and by using 85-µm core Yb-doped CCC fiber based power amplification stage. The CPSA system consists of 1-GHz repetition rate mode-locked fiber oscillator, followed by a pair of fast phase and amplitude electro-optic modulators, a diffraction-grating based pulse stretcher, a fiber amplifier chain, a GTI-cavity based pulse stacker, and a diffraction grating pulse compressor. Electro-optic modulators are used to carve out from the 1-GHz mode-locked pulse train an amplitude and phase modulated pulse burst, which after stretching and amplification, becomes equal-amplitude pulse burst consisting of 27 stretched pulses, each approximately 1-ns long. Initial pulse-burst shaping accounts for the strong amplifier saturation effects, so that it is compensated at the power amplifier output. This 27-pulse burst is then coherently stacked into a single pulse using a multiplexed sequence of 5 GTI cavities. The compact-footprint 4+1 multiplexed pulse stacker consists of 4 cavities having rountrip of 1 ns, and one Herriott-cell folded cavity - with 9ns roundtrip. After stacking, stretched pulses are compressed down to the bandwidth-limited 300 fs duration using a standard diffraction-grating pulse compressor.

Optimization of infrared two-color multicycle field synthesis for intense-isolated-attosecond-pulse generation

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

Lan Pengfei; Takahashi, Eiji J.; Midorikawa, Katsumi

2010-11-15

We present the optimization of the two-color synthesis method for generating an intense isolated attosecond pulse (IAP) in the multicycle regime. By mixing an infrared assistant pulse with a Ti:sapphire main pulse, we show that an IAP can be produced using a multicycle two-color pulse with a duration longer than 30 fs. We also discuss the influence of the carrier-envelope phase (CEP) and the relative intensity on the generation of IAPs. By optimizing the wavelength of the assistant field, IAP generation becomes insensitive to the CEP slip. Therefore, the optimized two-color method enables us to relax the requirements of pulsemore » duration and easily produce the IAP with a conventional multicycle laser pulse. In addition, it enables us to markedly suppress the ionization of the harmonic medium. This is a major advantage for efficiently generating intense IAPs from a neutral medium by applying the appropriate phase-matching and energy-scaling techniques.« less

Demonstration of periodic nanostructure formation with less ablation by double-pulse laser irradiation on titanium

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

Furukawa, Yuki; Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502; Advanced Research Center for Beam Science, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011

By pairing femtosecond laser pulses (duration ∼40 fs and central wavelength ∼810 nm) at an appropriate time interval, a laser-induced periodic surface structure (LIPSS) is formed with much less ablation than one formed with a single pulse. On a titanium plate, a pair of laser pulses with fluences of 70 and 140 mJ/cm{sup 2} and a rather large time interval (>10 ps) creates a LIPSS with an interspace of 600 nm, the same as that formed by a single pulse of 210 mJ/cm{sup 2}, while the double pulse ablates only 4 nm, a quarter of the ablation depth of a single pulse.

Efficient graphene saturable absorbers on D-shaped optical fiber for ultrashort pulse generation

PubMed Central

Zapata, J. D.; Steinberg, D.; Saito, L. A. M.; de Oliveira, R. E. P.; Cárdenas, A. M.; de Souza, E. A. Thoroh

2016-01-01

We demonstrated a method to construct high efficiency saturable absorbers based on the evanescent light field interaction of CVD monolayer graphene deposited on side-polished D-shaped optical fiber. A set of samples was fabricated with two different core-graphene distances (0 and 1 μm), covered with graphene ranging between 10 and 25 mm length. The mode-locking was achieved and the best pulse duration was 256 fs, the shortest pulse reported in the literature with CVD monolayer graphene in EDFL. As result, we find a criterion between the polarization relative extinction ratio in the samples and the pulse duration, which relates the better mode-locking performance with the higher polarization extinction ratio of the samples. This criterion also provides a better understanding of the graphene distributed saturable absorbers and their reproducible performance as optoelectronic devices for optical applications. PMID:26856886

Generating femtosecond optical pulses tunable from 2 to 3  μm with a silica-based all-fiber laser system.

PubMed

Anashkina, E A; Andrianov, A V; Yu Koptev, M; Muravyev, S V; Kim, A V

2014-05-15

Femtosecond pulses with broad tunability in the range of 2-3 μm are generated in a germanate-glass core silica-glass cladding fiber with a driving pulse at 2 μm produced by an all-fiber laser system consisting of an Er:fiber source at 1.6 μm, a Raman fiber shifter, and a Tm:fiber amplifier. We demonstrate optical pulses with a duration of the order of 100 fs that are the shortest ones reported in the 2.5-3 μm range obtained by fiber laser systems.

Fibre amplifier based on an ytterbium-doped active tapered fibre for the generation of megawatt peak power ultrashort optical pulses

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

Koptev, M Yu; Anashkina, E A; Lipatov, D S

2015-05-31

We report a new ytterbium-doped active tapered fibre used in the output amplifier stage of a fibre laser system for the generation of megawatt peak power ultrashort pulses in the microjoule energy range. The tapered fibre is single-mode at its input end (core and cladding diameters of 10 and 80 μm) and multimode at its output end (diameters of 45 and 430 μm), but ultrashort pulses are amplified in a quasi-single-mode regime. Using a hybrid Er/Yb fibre system comprising an erbium master oscillator and amplifier at a wavelength near 1.5 μm, a nonlinear wavelength converter to the 1 μm rangemore » and a three-stage ytterbium-doped fibre amplifier, we obtained pulses of 1 μJ energy and 7 ps duration, which were then compressed by a grating-pair dispersion compressor with 60% efficiency to a 130 fs duration, approaching the transform-limited pulse duration. The present experimental data agree well with numerical simulation results for pulse amplification in the threestage amplifier. (extreme light fields and their applications)« less

Nonphasematched broadband THz amplification and reshaping in a dispersive chi(3) medium.

PubMed

Koys, Martin; Noskovicova, Eva; Velic, Dusan; Lorenc, Dusan

2017-06-12

We theoretically investigate non-phasematched broadband THz amplification in dispersive chi(3) media. A short 100 fs pump pulse is interacting with a temporally matched second harmonic pulse and a weak THz signal through the four wave mixing process and a significant broadband THz amplification and reshaping is observed. The pulse evolution dynamics is explored by numerically solving a set of generalized Nonlinear Schroedinger equations. The influence of incident pulse chirp, pulse duration and the role of wavelength, THz seed frequency and losses are evaluated separately. It is found that a careful choice of incident parameters can provide a broadband THz output and/or a significant increase of THz peak power.

Femtosecond fiber CPA system based on picosecond master oscillator and power amplifier with CCC fiber.

PubMed

Želudevičius, J; Danilevičius, R; Viskontas, K; Rusteika, N; Regelskis, K

2013-03-11

Results of numerical and experimental investigations of the simple fiber CPA system seeded by nearly bandwidth-limited pulses from the picosecond oscillator are presented. We utilized self-phase modulation in a stretcher fiber to broaden the pulse spectrum and dispersion of the fiber to stretch pulses in time. During amplification in the ytterbium-doped CCC fiber, gain-shaping and self-phase modulation effects were observed, which improved pulse compression with a bulk diffraction grating compressor. After compression with spectral filtering, pulses with the duration of 400 fs and energy as high as 50 µJ were achieved, and the output beam quality was nearly diffraction-limited.

Laser-induced breakdown spectroscopy using mid-infrared femtosecond pulses

DOE PAGES

Hartig, K. C.; Colgan, J.; Kilcrease, D. P.; ...

2015-07-30

Here, we report on a laser-induced breakdown spectroscopy (LIBS) experiment driven by mid-infrared (2.05-μm) fs pulses, in which time-resolved emission spectra of copper were studied. Ab-initio modeling is consistent with the results of new fs measurements at 2.05 μm and traditional 800-nm fs-LIBS. Ablation by mid-infrared fs pulses results in a plasma with a lower plasma density and temperature compared to fs-LIBS performed at shorter laser wavelength. LIBS driven by mid-infrared fs pulses results in a signal-to-background ratio ~50% greater and a signal-to-noise ratio ~40% lower than fs-LIBS at near-infrared laser wavelength.

Green-diode-pumped femtosecond Ti:Sapphire laser with up to 450 mW average power.

PubMed

Gürel, K; Wittwer, V J; Hoffmann, M; Saraceno, C J; Hakobyan, S; Resan, B; Rohrbacher, A; Weingarten, K; Schilt, S; Südmeyer, T

2015-11-16

We investigate power-scaling of green-diode-pumped Ti:Sapphire lasers in continuous-wave (CW) and mode-locked operation. In a first configuration with a total pump power of up to 2 W incident onto the crystal, we achieved a CW power of up to 440 mW and self-starting mode-locking with up to 200 mW average power in 68-fs pulses using semiconductor saturable absorber mirror (SESAM) as saturable absorber. In a second configuration with up to 3 W of pump power incident onto the crystal, we achieved up to 650 mW in CW operation and up to 450 mW in 58-fs pulses using Kerr-lens mode-locking (KLM). The shortest pulse duration was 39 fs, which was achieved at 350 mW average power using KLM. The mode-locked laser generates a pulse train at repetition rates around 400 MHz. No complex cooling system is required: neither the SESAM nor the Ti:Sapphire crystal is actively cooled, only air cooling is applied to the pump diodes using a small fan. Because of mass production for laser displays, we expect that prices for green laser diodes will become very favorable in the near future, opening the door for low-cost Ti:Sapphire lasers. This will be highly attractive for potential mass applications such as biomedical imaging and sensing.

A Dual-Colour Architecture for Pump-Probe Spectroscopy of Ultrafast Magnetization Dynamics in the Sub-10-femtosecond Range.

PubMed

Gonçalves, C S; Silva, A S; Navas, D; Miranda, M; Silva, F; Crespo, H; Schmool, D S

2016-03-15

Current time-resolution-limited dynamic measurements clearly show the need for improved techniques to access processes on the sub-10-femtosecond timescale. To access this regime, we have designed and constructed a state-of-the-art time-resolved magneto-optic Kerr effect apparatus, based on a new dual-color scheme, for the measurement of ultrafast demagnetization and precessional dynamics in magnetic materials. This system can operate well below the current temporal ranges reported in the literature, which typically lie in the region of around 50 fs and above. We have used a dual-colour scheme, based on ultra broadband hollow-core fibre and chirped mirror pulse compression techniques, to obtain unprecedented sub-8-fs pump and probe pulse durations at the sample plane. To demonstrate the capabilities of this system for ultrafast demagnetization and precessional dynamics studies, we have performed measurements in a ferrimagnetic GdFeCo thin film. Our study has shown that the magnetization shows a sudden drop within the first picosecond after the pump pulse, a fast recovery (remagnetization) within a few picoseconds, followed by a clear oscillation or precession during a slower magnetization recovery. Moreover, we have experimentally confirmed for the first time that a sub-10-fs pulse is able to efficiently excite a magnetic system such as GdFeCo.

Experimental demonstration of a single-spike hard-X-ray free-electron laser starting from noise

DOE PAGES

Marinelli, A.; MacArthur, J.; Emma, P.; ...

2017-10-09

In this letter, we report the experimental demonstration of single-spike hard-X-ray free-electron laser pulses starting from noise with multi-eV bandwidth. Here, this is accomplished by shaping a low-charge electron beam with a slotted emittance spoiler and by adjusting the transport optics to optimize the beam-shaping accuracy. Based on elementary free-electron laser scaling laws, we estimate the pulse duration to be less than 1 fs full-width at half-maximum.

High-power thulium-doped fibre laser with intracavity dispersion management

NASA Astrophysics Data System (ADS)

Krylov, Aleksandr A.; Chernyshova, M. A.; Chernykh, D. S.; Senatorov, A. K.; Tupitsyn, I. M.; Kryukov, P. G.; Dianov, Evgenii M.

2012-05-01

This paper reports a scheme for the generation and amplification of pico- and femtosecond pulses in the range 1.93-1.97 μm using thulium-doped silica fibres. Group velocity dispersion (GVD) management in the cavity of the thulium-doped fibre laser oscillator is ensured by a single-mode germanosilicate fibre (75 mol % GeO2 in the core) with a positive GVD. Pulses are obtained down to 200 fs in duration and up to 56 nJ in energy.

Experimental demonstration of a single-spike hard-X-ray free-electron laser starting from noise

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

Marinelli, A.; MacArthur, J.; Emma, P.

In this letter, we report the experimental demonstration of single-spike hard-X-ray free-electron laser pulses starting from noise with multi-eV bandwidth. Here, this is accomplished by shaping a low-charge electron beam with a slotted emittance spoiler and by adjusting the transport optics to optimize the beam-shaping accuracy. Based on elementary free-electron laser scaling laws, we estimate the pulse duration to be less than 1 fs full-width at half-maximum.

Laser-driven ion acceleration: methods, challenges and prospects

NASA Astrophysics Data System (ADS)

Badziak, J.

2018-01-01

The recent development of laser technology has resulted in the construction of short-pulse lasers capable of generating fs light pulses with PW powers and intensities exceeding 1021 W/cm2, and has laid the basis for the multi-PW lasers, just being built in Europe, that will produce fs pulses of ultra-relativistic intensities ~ 1023 - 1024 W/cm2. The interaction of such an intense laser pulse with a dense target can result in the generation of collimated beams of ions of multi-MeV to GeV energies of sub-ps time durations and of extremely high beam intensities and ion fluencies, barely attainable with conventional RF-driven accelerators. Ion beams with such unique features have the potential for application in various fields of scientific research as well as in medical and technological developments. This paper provides a brief review of state-of-the art in laser-driven ion acceleration, with a focus on basic ion acceleration mechanisms and the production of ultra-intense ion beams. The challenges facing laser-driven ion acceleration studies, in particular those connected with potential applications of laser-accelerated ion beams, are also discussed.

Regenerative Amplification of Femtosecond Pulses: Design andConstruction of a sub-100fs, muon J Laser System

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

Schumacher, Andreas B.

1996-10-01

Femtosecond lasers are a powerful tool for a wealth of applications in physics, chemistry and biology. In most cases, however, their use is fundamentally restricted to a rather narrow spectral range. This thesis deals with the construction and characterization of a femtosecond light source for spectroscopic applications which overcomes that restriction. It is demonstrated how the output of a continuously pumped Ti:sapphire femtosecond oscillator is amplified to the μJ level,while the pulse duration remains below 100 fs. A combination of continuous pumping, acousto-optic switching and Ti:Al 2O 3 as a gain medium allows amplification at high repetition rates. By focusingmore » the high energy pulses into a sapphire crystal, a broad-band continuum can be generated, extended in wavelengths over several hundred nanometers. To accomplish amplification of three orders of magnitude while maintaining the pulse length, a regenerative multipass amplifier system was built. The thesis describes theoretical design, realization and characterization of the system. Theoretical calculations and preliminary measurements were carried out and allow a critical evaluation of the final performance.« less

Formation and Properties of Laser-Induced Periodic Surface Structures on Different Glasses.

PubMed

Gräf, Stephan; Kunz, Clemens; Müller, Frank A

2017-08-10

The formation and properties of laser-induced periodic surface structures (LIPSS) was investigated on different technically relevant glasses including fused silica, borosilicate glass, and soda-lime-silicate glass under irradiation of fs-laser pulses characterized by a pulse duration τ = 300 fs and a laser wavelength λ = 1025 nm. For this purpose, LIPSS were fabricated in an air environment at normal incidence with different laser peak fluence, pulse number, and repetition frequency. The generated structures were characterized by using optical microscopy, scanning electron microscopy, focused ion beam preparation and Fast-Fourier transformation. The results reveal the formation of LIPSS on all investigated glasses. LIPSS formation on soda-lime-silicate glass is determined by remarkable melt-formation as an intra-pulse effect. Differences between the different glasses concerning the appearing structures, their spatial period and their morphology were discussed based on the non-linear absorption behavior and the temperature-dependent viscosity. The findings facilitate the fabrication of tailored LIPSS-based surface structures on different technically relevant glasses that could be of particular interest for various applications.

Formation and Properties of Laser-Induced Periodic Surface Structures on Different Glasses

PubMed Central

Kunz, Clemens; Müller, Frank A.

2017-01-01

The formation and properties of laser-induced periodic surface structures (LIPSS) was investigated on different technically relevant glasses including fused silica, borosilicate glass, and soda-lime-silicate glass under irradiation of fs-laser pulses characterized by a pulse duration τ = 300 fs and a laser wavelength λ = 1025 nm. For this purpose, LIPSS were fabricated in an air environment at normal incidence with different laser peak fluence, pulse number, and repetition frequency. The generated structures were characterized by using optical microscopy, scanning electron microscopy, focused ion beam preparation and Fast-Fourier transformation. The results reveal the formation of LIPSS on all investigated glasses. LIPSS formation on soda-lime-silicate glass is determined by remarkable melt-formation as an intra-pulse effect. Differences between the different glasses concerning the appearing structures, their spatial period and their morphology were discussed based on the non-linear absorption behavior and the temperature-dependent viscosity. The findings facilitate the fabrication of tailored LIPSS-based surface structures on different technically relevant glasses that could be of particular interest for various applications. PMID:28796180

Generation and parametric amplification of broadband chirped pulses in the near-infrared

NASA Astrophysics Data System (ADS)

Marcinkevičiūtė, A.; Michailovas, K.; Butkus, R.

2018-05-01

We demonstrate generation and optical parametric amplification of broadband chirped pulses in the range of 1.8- 2 . 5 μm. The setup is built around Ti:sapphire oscillator as a seed source and 1 kHz Nd:YAG laser system as a pump source. Visible broadband seed pulses are temporally stretched and amplified in a non-collinear optical parametric amplifier before being mixed with fundamental harmonic of the pump laser. Difference frequency generation between positively-chirped broadband pulses centered at 0 . 7 μm and non-chirped narrowband pulses at 1064 nm produces negatively-chirped wide spectral bandwidth pulses in the infrared. After subsequent parametric amplification, pulses with more than 0.5 mJ energy were obtained with spectral bandwidth supporting transform-limited pulse durations as short as 23 fs.

Two-stage optical parametric chirped-pulse amplifier using sub-nanosecond pump pulse generated by stimulated Brillouin scattering compression

NASA Astrophysics Data System (ADS)

Ogino, Jumpei; Miyamoto, Sho; Matsuyama, Takahiro; Sueda, Keiichi; Yoshida, Hidetsugu; Tsubakimoto, Koji; Miyanaga, Noriaki

2014-12-01

We demonstrate optical parametric chirped-pulse amplification (OPCPA) based on two-beam pumping, using sub-nanosecond pulses generated by stimulated Brillouin scattering compression. Seed pulse energy, duration, and center wavelength were 5 nJ, 220 ps, and ˜1065 nm, respectively. The 532 nm pulse from a Q-switched Nd:YAG laser was compressed to ˜400 ps in heavy fluorocarbon FC-40 liquid. Stacking of two time-delayed pump pulses reduced the amplifier gain fluctuation. Using a walk-off-compensated two-stage OPCPA at a pump energy of 34 mJ, a total gain of 1.6 × 105 was obtained, yielding an output energy of 0.8 mJ. The amplified chirped pulse was compressed to 97 fs.

Control of periodic surface structures on silicon by combined temporal and polarization shaping of femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Fraggelakis, F.; Stratakis, E.; Loukakos, P. A.

2018-06-01

We demonstrate the capability to exercise advanced control on the laser-induced periodic surface structures (LIPSS) on silicon by combining the effect of temporal shaping, via tuning the interpulse temporal delay between double femtosecond laser pulses, along with the independent manipulation of the polarization state of each of the individual pulses. For this, cross-polarized (CP) as well as counter-rotating (CR) double circularly polarized pulses have been utilized. The pulse duration was 40 fs and the central wavelength of 790 nm. The linearly polarized double pulses are generated by a modified Michelson interferometer allowing the temporal delay between the pulses to vary from Δτ = -80 ps to Δτ = +80 ps with an accuracy of 0.2 fs. We show the significance of fluence balance between the two pulse components and its interplay with the interpulse delay and with the order of arrival of the individually polarized pulse components of the double pulse sequence on the final surface morphology. For the case of CR pulses we found that when the pulses are temporally well separated the surface morphology attains no axial symmetry. But strikingly, when the two CP pulses temporally overlap, we demonstrate, for the first time in our knowledge, the detrimental effect that the phase delay has on the ripple orientation. Our results provide new insight showing that temporal pulse shaping in combination with polarization control gives a powerful tool for drastically controlling the surface nanostructure morphology.

Nanosurgery of cells and chromosomes using near-infrared twelve-femtosecond laser pulses.

PubMed

Uchugonova, Aisada; Lessel, Matthias; Nietzsche, Sander; Zeitz, Christian; Jacobs, Karin; Lemke, Cornelius; König, Karsten

2012-10-01

ABSTRACT. Laser-assisted surgery based on multiphoton absorption of near-infrared laser light has great potential for high precision surgery at various depths within the cells and tissues. Clinical applications include refractive surgery (fs-LASIK). The non-contact laser method also supports contamination-free cell nanosurgery. In this paper we describe usage of an ultrashort femtosecond laser scanning microscope for sub-100 nm surgery of human cells and metaphase chromosomes. A mode-locked 85 MHz Ti:Sapphire laser with an M-shaped ultrabroad band spectrum (maxima: 770  nm/830  nm) and an in situ pulse duration at the target ranging from 12 fs up to 3 ps was employed. The effects of laser nanoprocessing in cells and chromosomes have been quantified by atomic force microscopy. These studies demonstrate the potential of extreme ultrashort femtosecond laser pulses at low mean milliwatt powers for sub-100 nm surgery of cells and cellular organelles.

Near monochromatic 20 Me V proton acceleration using fs laser irradiating Au foils in target normal sheath acceleration regime

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

Torrisi, L., E-mail: Lorenzo.Torrisi@unime.it; Ceccio, G.; Cannavò, A.

2016-04-15

A 200 mJ laser pulse energy, 39 fs-pulse duration, 10 μm focal spot, p-polarized radiation has been employed to irradiate thin Au foils to produce proton acceleration in the forward direction. Gold foils were employed to produce high density relativistic electrons emission in the forward direction to generate a high electric field driving the ion acceleration. Measurements were performed by changing the focal position in respect of the target surface. Proton acceleration was monitored using fast SiC detectors in time-of-flight configuration. A high proton energy, up to about 20 Me V, with a narrow energy distribution, was obtained in particular conditions dependingmore » on the laser parameters, the irradiation conditions, and a target optimization.« less

A Bright Future for Serial Femtosecond Crystallography with XFELs.

PubMed

Johansson, Linda C; Stauch, Benjamin; Ishchenko, Andrii; Cherezov, Vadim

2017-09-01

X-ray free electron lasers (XFELs) have the potential to revolutionize macromolecular structural biology due to the unique combination of spatial coherence, extreme peak brilliance, and short duration of X-ray pulses. A recently emerged serial femtosecond (fs) crystallography (SFX) approach using XFEL radiation overcomes some of the biggest hurdles of traditional crystallography related to radiation damage through the diffraction-before-destruction principle. Intense fs XFEL pulses enable high-resolution room-temperature structure determination of difficult-to-crystallize biological macromolecules, while simultaneously opening a new era of time-resolved structural studies. Here, we review the latest developments in instrumentation, sample delivery, data analysis, crystallization methods, and applications of SFX to important biological questions, and conclude with brief insights into the bright future of structural biology using XFELs. Copyright © 2017 Elsevier Ltd. All rights reserved.

FS laser processing of bio-polymer thin films for studying cell-to-substrate specific response

NASA Astrophysics Data System (ADS)

Daskalova, A.; Nathala, Chandra S. R.; Kavatzikidou, P.; Ranella, A.; Szoszkiewicz, R.; Husinsky, W.; Fotakis, C.

2016-09-01

The use of ultra-short pulses for nanoengineering of biomaterials opens up possibilities for biological, medical and tissue engineering applications. Structuring the surface of a biomaterial into arrays with micro- and nanoscale features and architectures, defines new roadmaps to innovative engineering of materials. Thin films of novel collagen/elastin composite and gelatin were irradiated by Ti:sapphire fs laser in air at central wavelength 800 nm, with pulse durations in the range of 30 fs. The size and shape as well as morphological forms occurring in the resulted areas of interaction were analyzed as a function of irradiation fluence and number of pulses by atomic force microscopy (AFM). The fs interaction regime allows generation of well defined micro porous surface arrays. In this study we examined a novel composite consisting of collagen and elastin in order to create a biodegradable matrix to serve as a biomimetic surface for cell attachment. Confocal microscopy images of modified zones reveal formation of surface fringe patterns with orientation direction alongside the area of interaction. Outside the crater rim a wave-like topography pattern is observed. Structured, on a nanometer scale, surface array is employed for cell-culture experiments for testing cell's responses to substrate morphology. Mice fibroblasts migration was monitored after 3 days cultivation period using FESEM. We found that fibroblasts cells tend to migrate and adhere along the laser modified zones. The performed study proved that the immobilized collagen based biofilms suite as a template for successful fibroblasts cell guidance and orientation. Fs laser induced morphological modification of biomimetic materials exhibit direct control over fibroblasts behaviour due to induced change in their wettability state.

Precise ablation of dental hard tissues with ultra-short pulsed lasers. Preliminary exploratory investigation on adequate laser parameters.

PubMed

Bello-Silva, Marina Stella; Wehner, Martin; Eduardo, Carlos de Paula; Lampert, Friedrich; Poprawe, Reinhart; Hermans, Martin; Esteves-Oliveira, Marcella

2013-01-01

This study aimed to evaluate the possibility of introducing ultra-short pulsed lasers (USPL) in restorative dentistry by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages, such as thermal damage of irradiated substrate. USPL ablation of dental hard tissues was investigated in two phases. Phase 1--different wavelengths (355, 532, 1,045, and 1,064 nm), pulse durations (picoseconds and femtoseconds) and irradiation parameters (scanning speed, output power, and pulse repetition rate) were assessed for enamel and dentin. Ablation rate was determined, and the temperature increase measured in real time. Phase 2--the most favorable laser parameters were evaluated to correlate temperature increase to ablation rate and ablation efficiency. The influence of cooling methods (air, air-water spray) on ablation process was further analyzed. All parameters tested provided precise and selective tissue ablation. For all lasers, faster scanning speeds resulted in better interaction and reduced temperature increase. The most adequate results were observed for the 1064-nm ps-laser and the 1045-nm fs-laser. Forced cooling caused moderate changes in temperature increase, but reduced ablation, being considered unnecessary during irradiation with USPL. For dentin, the correlation between temperature increase and ablation efficiency was satisfactory for both pulse durations, while for enamel, the best correlation was observed for fs-laser, independently of the power used. USPL may be suitable for cavity preparation in dentin and enamel, since effective ablation and low temperature increase were observed. If adequate laser parameters are selected, this technique seems to be promising for promoting the laser-assisted, minimally invasive approach.

Double-Wall Carbon Nanotube Hybrid Mode-Locker in Tm-doped Fibre Laser: A Novel Mechanism for Robust Bound-State Solitons Generation

NASA Astrophysics Data System (ADS)

Chernysheva, Maria; Bednyakova, Anastasia; Al Araimi, Mohammed; Howe, Richard C. T.; Hu, Guohua; Hasan, Tawfique; Gambetta, Alessio; Galzerano, Gianluca; Rümmeli, Mark; Rozhin, Aleksey

2017-03-01

The complex nonlinear dynamics of mode-locked fibre lasers, including a broad variety of dissipative structures and self-organization effects, have drawn significant research interest. Around the 2 μm band, conventional saturable absorbers (SAs) possess small modulation depth and slow relaxation time and, therefore, are incapable of ensuring complex inter-pulse dynamics and bound-state soliton generation. We present observation of multi-soliton complex generation in mode-locked thulium (Tm)-doped fibre laser, using double-wall carbon nanotubes (DWNT-SA) and nonlinear polarisation evolution (NPE). The rigid structure of DWNTs ensures high modulation depth (64%), fast relaxation (1.25 ps) and high thermal damage threshold. This enables formation of 560-fs soliton pulses; two-soliton bound-state with 560 fs pulse duration and 1.37 ps separation; and singlet+doublet soliton structures with 1.8 ps duration and 6 ps separation. Numerical simulations based on the vectorial nonlinear Schr¨odinger equation demonstrate a transition from single-pulse to two-soliton bound-states generation. The results imply that DWNTs are an excellent SA for the formation of steady single- and multi-soliton structures around 2 μm region, which could not be supported by single-wall carbon nanotubes (SWNTs). The combination of the potential bandwidth resource around 2 μm with the soliton molecule concept for encoding two bits of data per clock period opens exciting opportunities for data-carrying capacity enhancement.

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.

Self-calibrating d-scan: measuring ultrashort laser pulses on-target using an arbitrary pulse compressor.

PubMed

Alonso, Benjamín; Sola, Íñigo J; Crespo, Helder

2018-02-19

In most applications of ultrashort pulse lasers, temporal compressors are used to achieve a desired pulse duration in a target or sample, and precise temporal characterization is important. The dispersion-scan (d-scan) pulse characterization technique usually involves using glass wedges to impart variable, well-defined amounts of dispersion to the pulses, while measuring the spectrum of a nonlinear signal produced by those pulses. This works very well for broadband few-cycle pulses, but longer, narrower bandwidth pulses are much more difficult to measure this way. Here we demonstrate the concept of self-calibrating d-scan, which extends the applicability of the d-scan technique to pulses of arbitrary duration, enabling their complete measurement without prior knowledge of the introduced dispersion. In particular, we show that the pulse compressors already employed in chirped pulse amplification (CPA) systems can be used to simultaneously compress and measure the temporal profile of the output pulses on-target in a simple way, without the need of additional diagnostics or calibrations, while at the same time calibrating the often-unknown differential dispersion of the compressor itself. We demonstrate the technique through simulations and experiments under known conditions. Finally, we apply it to the measurement and compression of 27.5 fs pulses from a CPA laser.

Femtosecond-laser surface modification and micropatterning of diamond-like nanocomposite films to control friction on the micro and macroscale

NASA Astrophysics Data System (ADS)

Pimenov, S. M.; Zavedeev, E. V.; Arutyunyan, N. R.; Zilova, O. S.; Shupegin, M. L.; Jaeggi, B.; Neuenschwander, B.

2017-10-01

Laser surface micropatterning (texturing) of hard materials and coatings is an effective technique to improve tribological systems. In the paper, we have investigated the laser-induced surface modifications and micropatterning of diamond-like nanocomposite (DLN) films (a-C:H,Si:O) using IR and visible femtosecond (fs) lasers, focusing on the improvement of frictional properties of laser-patterned films on the micro and macroscale. The IR and visible fs-lasers, operating at λ = 1030 nm and λ = 515 nm wavelengths (pulse duration 320 fs and pulse repetition rate 101 kHz), are used to fabricate different patterns for subsequent friction tests. The IR fs-laser is applied to produce hill-like micropatterns under conditions of surface graphitization and incipient ablation, and the visible fs-laser is used for making microgroove patterns in DLN films under ablation conditions. Regimes of irradiation with low-energy IR laser pulses are chosen to produce graphitized micropatterns. For these regimes, results of numerical calculations of the temperature and graphitized layer growth are presented to show good correlation with surface relief modifications, and the features of fs-laser graphitization are discussed based on Raman spectroscopy analysis. Using lateral force microscopy, the role of surface modifications (graphitization, nanostructuring) in the improved microfriction properties is investigated. New data of the influence of capillary forces on friction forces, which strongly changes the microscale friction behaviour, are presented for a wide range of loads (from nN to μN) applied to Si tips. In macroscopic ball-on-disk tests, a pair-dependent friction behaviour of laser-patterned films is observed. The first experimental data of the improved friction properties of laser-micropatterned DLN films under boundary lubricated sliding conditions are presented. The obtained results show the DLN films as an interesting coating material suitable for laser patterning applications in tribology.

Interaction of Intense Short Laser Pulses with Air and Dielectric Materials

NASA Astrophysics Data System (ADS)

Eisenmann, S.; Katzir, Y.; Zigler, A.; Fibich, G.; Louzon, E.; Ehrlich, Y.; Henis, Z.; Pecker, S.; Fisher, D.; Fraenkel, M.

A study of the propagation of intense short laser pulses in air and the interaction of these pulses with distant targets is described. It is shown that the beam filamentation pattern can be controlled by introducing beam astigmatism. In addition, it is demonstrated that the collapse distance of intense femtosecond laser beams scales as P-1/2 for input powers that are moderately above the critical power for self focusing, and that at higher powers the collapse distance scales as P-1. Related to the interaction of intense short pulses with distant targets, it is measured that the threshold fluence for optical damage in wide gap materials is lower by up to 20% for negatively chirped pulses than for positively chirped, at pulse durations ranging from 60 fs to 1 ps.

Optimal design of similariton fiber lasers without gain-bandwidth limitation.

PubMed

Li, Xingliang; Zhang, Shumin; Yang, Zhenjun

2017-07-24

We have numerically investigated broadband high-energy similariton fiber lasers, demonstrated that the self-similar evolution of pulses can locate in a segment of photonic crystal fiber without gain-bandwidth limitation. The effects of various parameters, including the cavity length, the spectral filter bandwidth, the pump power, the length of the photonic crystal fiber and the output coupling ratio have also been studied in detail. Using the optimal parameters, a single pulse with spectral width of 186.6 nm, pulse energy of 23.8 nJ, dechirped pulse duration of 22.5 fs and dechirped pulse peak power of 1.26 MW was obtained. We believe that this detailed analysis of the behaviour of pulses in the similariton regime may have major implications in the development of broadband high-energy fiber lasers.

Scattering Response of Sucrose Clusters with Intense XFEL Pulses in Water Window

NASA Astrophysics Data System (ADS)

Ho, Phay; Benedikt Daurer, Benedikt; Bielecki, Johan; Hantke, Max; Maia, Filipe; Knight, Chris; Hajdu, Janos; Young, Linda; Bostedt, Christoph

2017-04-01

We present a combined experimental and theoretical study about the effects of non-linear x-ray ionization dynamics on the scattering response of molecular clusters in the soft x-ray regime that includes and goes beyond the water window. Nanosized sucrose clusters were irradiated with intense XFEL pulses (photon energy from 500 to 1500 eV and pulse duration of 180 fs). Surprisingly, the measured scattering signals near the oxygen K-edge in the water window are found to be substantially smaller than those at higher photon energies. We employ Monte-Carlo/Molecular Dynamics calculations to investigate the x-ray processes as a function of pulse parameters (photon energy, bandwidth and pulse duration) and cluster size. We demonstrate the important role of resonant excitation (RE) in the molecular scattering response in the water window. In particular, 1s ->2p RE cycling enabled in the oxygen atom/ion provide additional ionization pathways which, combined with the long pulse duration, lead to substantial reduction in scattering power of sugar clusters for photon energies just below the oxygen K-edge. Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, US Dept of Energy, Contract DE-AC02-06CH11357.

Low Group Delay Dispersion Optical Coating for Broad Bandwidth High Reflection at 45° Incidence, P Polarization of Femtosecond Pulses with 900 nm Center Wavelength

DOE PAGES

Bellum, John C.; Field, Ella S.; Winstone, Trevor B.; ...

2016-03-01

We describe an optical coating design suitable for broad bandwidth high reflection (BBHR) at 45° angle of incidence (AOI), P polarization (Ppol) of femtosecond (fs) laser pulses whose wavelengths range from 800 to 1000 nm. The design process is guided by quarter-wave HR coating properties. Our design must afford low group delay dispersion (GDD) for reflected light over the broad, 200 nm bandwidth in order to minimize temporal broadening of the fs pulses due to dispersive alteration of relative phases between their frequency components. The design should also be favorable to high laser-induced damage threshold (LIDT). We base the coatingmore » on TiO 2/SiO 2 layer pairs produced by means of e-beam evaporation with ion-assisted deposition, and use OptiLayer Thin Film Software to explore designs starting with TiO 2/SiO 2 layers having thicknesses in a reverse chirped arrangement. This approach led to a design with R > 99% from 800 to 1000 nm and GDD < 20 fs 2 from 843 to 949 nm (45° AOI, Ppol). The design’s GDD behaves in a smooth way, suitable for GDD compensation techniques, and its electric field intensities show promise for high LIDTs. Reflectivity and GDD measurements for the initial test coating indicate good performance of the BBHR design. Subsequent coating runs with improved process calibration produced two coatings whose HR bands satisfactorily meet the design goals. Lastly, for the sake of completeness, we summarize our previously reported transmission spectra and LIDT test results with 800 ps, 8 ps and 675 fs pulses for these two coatings, and present a table of the LIDT results we have for all of our TiO 2/SiO 2 BBHR coatings, showing the trends with test laser pulse duration from the ns to sub-ps regimes.« less

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.

Joint quantum measurement using unbalanced array detection.

PubMed

Beck, M; Dorrer, C; Walmsley, I A

2001-12-17

We have measured the joint Q-function of a highly multimode field using unbalanced heterodyne detection with a charge-coupled device array detector. We use spectral interferometry between a weak signal field and a strong, 100 fs duration local oscillator pulse to reconstruct the joint quadrature amplitude statistics of about 25 temporal modes. By adjusting the time delay between the signal and local oscillator pulses we are able to shift all the classical noise to modes distinct from the signal. This obviates the need to use a balanced detector.

Tungsten diselenide for mode-locked erbium-doped fiber lasers with short pulse duration

NASA Astrophysics Data System (ADS)

Liu, Wenjun; Liu, Mengli; OuYang, Yuyi; Hou, Huanran; Ma, Guoli; Lei, Ming; Wei, Zhiyi

2018-04-01

In this paper, a WSe2 film prepared by chemical vapor deposition (CVD) is transferred onto a tapered fiber, and a WSe2 saturable absorber (SA) is fabricated. In order to measure the third-order optical nonlinearity of the WSe2, the Z-scan technique is applied. The modulation depth of the WSe2 SA is measured as being 21.89%. Taking advantage of the remarkable nonlinear absorption characteristic of the WSe2 SA, a mode-locked erbium-doped fiber laser is demonstrated at 1557.4 nm with a bandwidth of 25.8 nm and signal to noise ratio of 96 dB. To the best of our knowledge, the pulse duration of 163.5 fs is confirmed to be the shortest compared with previous mode-locked fiber lasers based on transition-metal dichalcogenides SAs. These results indicate that WSe2 is a powerful competitor in the application of ultrashort pulse lasers.

Normal dispersion femtosecond fiber optical parametric oscillator.

PubMed

Nguyen, T N; Kieu, K; Maslov, A V; Miyawaki, M; Peyghambarian, N

2013-09-15

We propose and demonstrate a synchronously pumped fiber optical parametric oscillator (FOPO) operating in the normal dispersion regime. The FOPO generates chirped pulses at the output, allowing significant pulse energy scaling potential without pulse breaking. The output average power of the FOPO at 1600 nm was ∼60  mW (corresponding to 1.45 nJ pulse energy and ∼55% slope power conversion efficiency). The output pulses directly from the FOPO were highly chirped (∼3  ps duration), and they could be compressed outside of the cavity to 180 fs by using a standard optical fiber compressor. Detailed numerical simulation was also performed to understand the pulse evolution dynamics around the laser cavity. We believe that the proposed design concept is useful for scaling up the pulse energy in the FOPO using different pumping wavelengths.

Extension of supercontinuum spectrum, generated in polarization-maintaining photonic crystal fiber, using chirped femtosecond pulses

NASA Astrophysics Data System (ADS)

Vengelis, Julius; Jarutis, Vygandas; Sirutkaitis, Valdas

2018-01-01

We present results of experimental and numerical investigation of supercontinuum (SC) generation in polarization-maintaining photonic crystal fiber (PCF) using chirped femtosecond pulses. The initial unchirped pump pulse source was a mode-locked Yb:KGW laser generating 52-nJ energy, 110-fs duration pulses at 1030 nm with a 76-MHz repetition rate. The nonlinear medium was a 32-cm-long polarization-maintaining PCF manufactured by NKT Photonics A/S. We demonstrated the influence of pump pulse chirp on spectral characteristics of a SC. We showed that by chirping pump pulses positively or negatively one can obtain a broader SC spectrum than in the case of unchirped pump pulses at the same peak power. Moreover, the extension can be controlled by changing the amount of pump pulse chirp. Numerical simulation results also indicated that pump pulse chirp yields an extension of SC spectrum.

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

PubMed Central

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

2017-01-01

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

Dominance of hole-boring radiation pressure acceleration regime with thin ribbon of ionized solid hydrogen

NASA Astrophysics Data System (ADS)

Psikal, J.; Matys, M.

2018-04-01

Laser-driven proton acceleration from novel cryogenic hydrogen target of the thickness of tens of microns irradiated by multiPW laser pulse is investigated here for relevant laser parameters accessible in near future. It is demonstrated that the efficiency of proton acceleration from relatively thick hydrogen solid ribbon largely exceeds the acceleration efficiency for a thinner ionized plastic foil, which can be explained by enhanced hole boring (HB) driven by laser ponderomotive force in the case of light ions and lower target density. Three-dimensional particle-in-cell (PIC) simulations of laser pulse interaction with relatively thick hydrogen target show larger energies of protons accelerated in the target interior during the HB phase and reduced energies of protons accelerated from the rear side of the target by quasistatic electric field compared with the results obtained from two-dimensional PIC calculations. Linearly and circularly polarized multiPW laser pulses of duration exceeding 100 fs show similar performance in terms of proton acceleration from both the target interior as well as from the rear side of the target. When ultrashort pulse (∼30 fs) is assumed, the number of accelerated protons from the target interior is substantially reduced.

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

NASA Astrophysics Data System (ADS)

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

2018-02-01

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

Femtosecond Laser Texturing of Surfaces for Tribological Applications

PubMed Central

Kirner, Sabrina V.; Griepentrog, Michael; Spaltmann, Dirk

2018-01-01

Laser texturing is an emerging technology for generating surface functionalities on basis of optical, mechanical, or chemical properties. Taking benefit of laser sources with ultrashort (fs) pulse durations features outstanding precision of machining and negligible rims or burrs surrounding the laser-irradiation zone. Consequently, additional mechanical or chemical post-processing steps are usually not required for fs-laser surface texturing (fs-LST). This work aimed to provide a bridge between research in the field of tribology and laser materials processing. The paper reviews the current state-of-the-art in fs-LST, with a focus on the tribological performance (friction and wear) of specific self-organized surface structures (so-called ripples, grooves, and spikes) on steel and titanium alloys. On the titanium alloy, specific sickle-shaped hybrid micro-nanostructures were also observed and tribologically tested. Care is taken to identify accompanying effects affecting the materials hardness, superficial oxidation, nano- and microscale topographies, and the role of additives contained in lubricants, such as commercial engine oil. PMID:29762544

Femtosecond Laser Texturing of Surfaces for Tribological Applications.

PubMed

Bonse, Jörn; Kirner, Sabrina V; Griepentrog, Michael; Spaltmann, Dirk; Krüger, Jörg

2018-05-15

Laser texturing is an emerging technology for generating surface functionalities on basis of optical, mechanical, or chemical properties. Taking benefit of laser sources with ultrashort (fs) pulse durations features outstanding precision of machining and negligible rims or burrs surrounding the laser-irradiation zone. Consequently, additional mechanical or chemical post-processing steps are usually not required for fs-laser surface texturing (fs-LST). This work aimed to provide a bridge between research in the field of tribology and laser materials processing. The paper reviews the current state-of-the-art in fs-LST, with a focus on the tribological performance (friction and wear) of specific self-organized surface structures (so-called ripples, grooves, and spikes) on steel and titanium alloys. On the titanium alloy, specific sickle-shaped hybrid micro-nanostructures were also observed and tribologically tested. Care is taken to identify accompanying effects affecting the materials hardness, superficial oxidation, nano- and microscale topographies, and the role of additives contained in lubricants, such as commercial engine oil.

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

Meshalkin, Yu P; Popova, N A; Nikolin, V P

The influence of femtosecond radiation of a titaniumsapphire laser on cells of the transplantable ascitic tumour Krebs-2 was studied. After in vitro irradiation by the pulsed fundamentalharmonic radiation with the wavelength 800 nm, pulse duration 30 fs, repetition rate 1 kHz, mean power 100 and 300 mW and exposure time 3 min, as well as by the second-harmonic radiation (40 nm, 50 fs, 120 mW), all cells were diffusely stained by the vital stain trypan blue, which may be an evidence of their death or abnormalities of membrane permeability. However, implantation of such cells to experimental animals led to formationmore » of tumours at the transplantation site with the kinetics slightly different from the control one. In the group of mice to which the cells were inoculated after irradiation with second harmonic pulses of titanium-sapphire laser the inhibition of tumour growth was observed due to partial death of cells under the action of UV spectral components. To explain the mechanism of the observed phenomenon the possibility of pore formation (photoporation) in the cell membrane, described earlier in the papers on foreign DNA transfection into cells, is considered.« less

A novel setup for femtosecond pump-repump-probe IR spectroscopy with few cycle CEP stable pulses.

PubMed

Bradler, Maximilian; Werhahn, Jasper C; Hutzler, Daniel; Fuhrmann, Simon; Heider, Rupert; Riedle, Eberhard; Iglev, Hristo; Kienberger, Reinhard

2013-08-26

We present a three-color mid-IR setup for vibrational pump-repump-probe experiments with a temporal resolution well below 100 fs and a freely selectable spectral resolution of 20 to 360 cm(-1) for the pump and repump. The usable probe range without optical realignment is 900 cm(-1). The experimental design employed is greatly simplified compared to the widely used setups, highly robust and includes a novel means for generation of tunable few-cycle pulses with stable carrier-envelope phase. A Ti:sapphire pump system operating with 1 kHz and a modest 150 fs pulse duration supplies the total pump energy of just 0.6 mJ. The good signal-to-noise ratio of the setup allows the determination of spectrally resolved transient probe changes smaller than 6·10(-5) OD at 130 time delays in just 45 minutes. The performance of the spectrometer is demonstrated with transient IR spectra and decay curves of HDO molecules in lithium nitrate trihydrate and ice and a first all MIR pump-repump-probe measurement.

Probe-pulse optimization for nonresonant suppression in hybrid fs/ps coherent anti-Stokes Raman scattering at high temperature.

PubMed

Miller, Joseph D; Slipchenko, Mikhail N; Meyer, Terrence R

2011-07-04

Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) offers accurate thermometry at kHz rates for combustion diagnostics. In high-temperature flames, selection of probe-pulse characteristics is key to simultaneously optimizing signal-to-nonresonant-background ratio, signal strength, and spectral resolution. We demonstrate a simple method for enhancing signal-to-nonresonant-background ratio by using a narrowband Lorentzian filter to generate a time-asymmetric probe pulse with full-width-half-maximum (FWHM) pulse width of only 240 fs. This allows detection within just 310 fs after the Raman excitation for eliminating nonresonant background while retaining 45% of the resonant signal at 2000 K. The narrow linewidth is comparable to that of a time-symmetric sinc2 probe pulse with a pulse width of ~2.4 ps generated with a conventional 4-f pulse shaper. This allows nonresonant-background-free, frequency-domain vibrational spectroscopy at high temperature, as verified using comparisons to a time-dependent theoretical fs/ps CARS model.

High-energy infrared femtosecond pulses generated by dual-chirped optical parametric amplification.

PubMed

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

2015-11-01

We demonstrate high-energy infrared femtosecond pulse generation by a dual-chirped optical parametric amplification (DC-OPA) scheme [Opt. Express19, 7190 (2011)]. By employing a 100 mJ pump laser, a signal pulse energy exceeding 20 mJ at a wavelength of 1.4 μm was achieved before dispersion compensation. A total output energy of 33 mJ was recorded. Under a further energy scaling condition, the signal pulse was compressed to an almost transform-limited duration of 27 fs using a fused silica prism compressor. Since the DC-OPA scheme is efficient and energy scalable, design parameters for obtaining 100 mJ level infrared pulses are presented, which are suitable as driver lasers for the energy scaling of high-order harmonic generation with sub-keV photon energy.

Ultrashort pulse high repetition rate laser system for biological tissue processing

DOEpatents

Neev, Joseph; Da Silva, Luiz B.; Matthews, Dennis L.; Glinsky, Michael E.; Stuart, Brent C.; Perry, Michael D.; Feit, Michael D.; Rubenchik, Alexander M.

1998-01-01

A method and apparatus is disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates. The duration of each laser pulse is on the order of about 1 fs to less than 50 ps such that energy deposition is localized in a small depth and occurs before significant hydrodynamic motion and thermal conduction, leading to collateral damage, can take place. The depth of material removed per pulse is on the order of about 1 micrometer, and the minimal thermal and mechanical effects associated with this ablation method allows for high repetition rate operation, in the region 10 to over 1000 Hertz, which, in turn, achieves high material removal rates. The input laser energy per ablated volume of tissue is small, and the energy density required to ablate material decreases with decreasing pulse width. The ablation threshold and ablation rate are only weakly dependent on tissue type and condition, allowing for maximum flexibility of use in various biological tissue removal applications. The use of a chirped-pulse amplified Titanium-doped sapphire laser is disclosed as the source in one embodiment.

Ultrashort pulse high repetition rate laser system for biological tissue processing

DOEpatents

Neev, J.; Da Silva, L.B.; Matthews, D.L.; Glinsky, M.E.; Stuart, B.C.; Perry, M.D.; Feit, M.D.; Rubenchik, A.M.

1998-02-24

A method and apparatus are disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates. The duration of each laser pulse is on the order of about 1 fs to less than 50 ps such that energy deposition is localized in a small depth and occurs before significant hydrodynamic motion and thermal conduction, leading to collateral damage, can take place. The depth of material removed per pulse is on the order of about 1 micrometer, and the minimal thermal and mechanical effects associated with this ablation method allows for high repetition rate operation, in the region 10 to over 1000 Hertz, which, in turn, achieves high material removal rates. The input laser energy per ablated volume of tissue is small, and the energy density required to ablate material decreases with decreasing pulse width. The ablation threshold and ablation rate are only weakly dependent on tissue type and condition, allowing for maximum flexibility of use in various biological tissue removal applications. The use of a chirped-pulse amplified Titanium-doped sapphire laser is disclosed as the source in one embodiment. 8 figs.

1-MHz high power femtosecond Yb-doped fiber chirped-pulse amplifier

NASA Astrophysics Data System (ADS)

Hu, Zhong-Qi; Yang, Pei-Long; Teng, Hao; Zhu, Jiang-Feng; Wei, Zhi-Yi

2018-01-01

A practical femtosecond polarization-maintaining Yb-doped fiber amplifier enabling 153 fs transform-limited pulse duration with 32 μJ pulse energy at 1 MHz repetition rate corresponding to a peak power of 0.21 GW is demonstrated. The laser system based on chirped-pulse amplification (CPA) technique is seeded by a dispersion managed, nonlinear polarization evolution (NPE) mode-locked oscillator with spectrum bandwidth of 31 nm at 1040 nm and amplified by three fiber pre-amplifying stages and a rod type fiber main amplifying stage. The laser works with beam quality of M2 of 1.3 and power stability of 0.63% (root mean square, RMS) over 24 hours will be stable sources for industrial micromachining, medical therapy and scientific research.

Double-Wall Carbon Nanotube Hybrid Mode-Locker in Tm-doped Fibre Laser: A Novel Mechanism for Robust Bound-State Solitons Generation

PubMed Central

Chernysheva, Maria; Bednyakova, Anastasia; Al Araimi, Mohammed; Howe, Richard C. T.; Hu, Guohua; Hasan, Tawfique; Gambetta, Alessio; Galzerano, Gianluca; Rümmeli, Mark; Rozhin, Aleksey

2017-01-01

The complex nonlinear dynamics of mode-locked fibre lasers, including a broad variety of dissipative structures and self-organization effects, have drawn significant research interest. Around the 2 μm band, conventional saturable absorbers (SAs) possess small modulation depth and slow relaxation time and, therefore, are incapable of ensuring complex inter-pulse dynamics and bound-state soliton generation. We present observation of multi-soliton complex generation in mode-locked thulium (Tm)-doped fibre laser, using double-wall carbon nanotubes (DWNT-SA) and nonlinear polarisation evolution (NPE). The rigid structure of DWNTs ensures high modulation depth (64%), fast relaxation (1.25 ps) and high thermal damage threshold. This enables formation of 560-fs soliton pulses; two-soliton bound-state with 560 fs pulse duration and 1.37 ps separation; and singlet+doublet soliton structures with 1.8 ps duration and 6 ps separation. Numerical simulations based on the vectorial nonlinear Schr¨odinger equation demonstrate a transition from single-pulse to two-soliton bound-states generation. The results imply that DWNTs are an excellent SA for the formation of steady single- and multi-soliton structures around 2 μm region, which could not be supported by single-wall carbon nanotubes (SWNTs). The combination of the potential bandwidth resource around 2 μm with the soliton molecule concept for encoding two bits of data per clock period opens exciting opportunities for data-carrying capacity enhancement. PMID:28287159

Comparative study of CW, nanosecond- and femtosecond-pulsed laser microcutting of AZ31 magnesium alloy stents.

PubMed

Gökhan Demir, Ali; Previtali, Barbara

2014-06-01

Magnesium alloys constitute an interesting solution for cardiovascular stents due to their biocompatibility and biodegradability in human body. Laser microcutting is the industrially accepted method for stent manufacturing. However, the laser-material interaction should be well investigated to control the quality characteristics of the microcutting process that concern the surface roughness, chemical composition, and microstructure of the final device. Despite the recent developments in industrial laser systems, a universal laser source that can be manipulated flexibly in terms of process parameters is far from reality. Therefore, comparative studies are required to demonstrate processing capabilities. In particular, the laser pulse duration is a key factor determining the processing regime. This work approaches the laser microcutting of AZ31 Mg alloy from the perspective of a comparative study to evaluate the machining capabilities in continuous wave (CW), ns- and fs-pulsed regimes. Three industrial grade machining systems were compared to reach a benchmark in machining quality, productivity, and ease of postprocessing. The results confirmed that moving toward the ultrashort pulse domain the machining quality increases, but the need for postprocessing remains. The real advantage of ultrashort pulsed machining was the ease in postprocessing and maintaining geometrical integrity of the stent mesh after chemical etching. Resultantly, the overall production cycle time was shortest for fs-pulsed laser system, despite the fact that CW laser system provided highest cutting speed.

Parasitic lasing suppression in large-aperture Ti:sapphire amplifiers by optimizing the seed-pump time delay

NASA Astrophysics Data System (ADS)

Chu, Y. X.; Liang, X. Y.; Yu, L. H.; Xu, L.; Lu, X. M.; Liu, Y. Q.; Leng, Y. X.; Li, R. X.; Xu, Z. Z.

2013-05-01

Theoretical and experimental investigations are carried out to determine the influence of the time delay between the input seed pulse and pump pulses on transverse parasitic lasing in a Ti:sapphire amplifier with a diameter of 80 mm, which is clad by a refractive index-matched liquid doped with an absorber. When the time delay is optimized, a maximum output energy of 50.8 J is achieved at a pump energy of 105 J, which corresponds to a conversion efficiency of 47.5%. Based on the existing compressor, the laser system achieves a peak power of 1.26 PW with a 29.0 fs pulse duration.

A practical topological insulator saturable absorber for mode-locked fiber laser

PubMed Central

Yan, Peiguang; Lin, Rongyong; Ruan, Shuangchen; Liu, Aijiang; Chen, Hao; Zheng, Yuequn; Chen, Sifan; Guo, Chunyu; Hu, Juguang

2015-01-01

A novel saturable absorber (SA) was fabricated by coating the topological insulator (TI) film on microfiber using pulsed laser deposition (PLD) method. The TISA device had an insertion loss of ~1.25 dB, a saturable intensity of 26.7 MW/cm2, a modulation depth of ~5.7%, and a nonsaturable loss of 20.5%. Upon employing this SA device, we established a passively mode-locked EDFL and achieved nearly free-chirped soliton pulse with 286 fs of pulse duration and >73 dB of signal to noise ratio (SNR). This result clearly evidences that the PLD is an effective scheme for practical SA device fabrication. PMID:25732598

Hybrid femtosecond/picosecond rotational coherent anti-Stokes Raman scattering temperature and concentration measurements using two different picosecond-duration probes.

PubMed

Kearney, Sean P; Scoglietti, Daniel J; Kliewer, Christopher J

2013-05-20

A hybrid fs/ps pure-rotational CARS scheme is characterized in furnace-heated air at temperatures from 290 to 800 K. Impulsive femtosecond excitation is used to prepare a rotational Raman coherence that is probed with a ps-duration beam generated from an initially broadband fs pulse that is bandwidth limited using air-spaced Fabry-Perot etalons. CARS spectra are generated using 1.5- and 7.0-ps duration probe beams with corresponding coarse and narrow spectral widths. The spectra are fitted using a simple phenomenological model for both shot-averaged and single-shot measurements of temperature and oxygen mole fraction. Our single-shot temperature measurements exhibit high levels of precision and accuracy when the spectrally coarse 1.5-ps probe beam is used, demonstrating that high spectral resolution is not required for thermometry. An initial assessment of concentration measurements in air is also provided, with best results obtained using the higher resolution 7.0-ps probe. This systematic assessment of the hybrid CARS technique demonstrates its utility for practical application in low-temperature gas-phase systems.

Highly efficient and high-power diode-pumped femtosecond Yb:LYSO laser

NASA Astrophysics Data System (ADS)

Tian, Wenlong; Wang, Zhaohua; Zhu, Jiangfeng; Zheng, Lihe; Xu, Jun; Wei, Zhiyi

2017-04-01

A diode-pumped high-power femtosecond Yb:LYSO laser with high efficiency is demonstrated. With a semiconductor saturable absorber mirror for passive mode-locking and a Gires-Tournois interferometer mirror for intracavity dispersion compensation, stable mode-locking pulses of 297 fs duration at 1042 nm were obtained. The maximum average power of 3.07 W was realized under 5.17 W absorbed pump power, corresponding to as high as 59.4% opt-opt efficiency. The single pulse energy and peak power are about 35.5 nJ and 119.5 kW, respectively.

The nature of multiphoton fluorescence from red blood cells

NASA Astrophysics Data System (ADS)

Saytashev, Ilyas; Murphy, Michael; Osseiran, Sam; Spence, Dana M.; Evans, Conor L.; Dantus, Marcos

2016-03-01

We report on the nature of multiphoton excited fluorescence observed from human erythrocytes (red blood cells RBC's) and their "ghosts" following 800nm sub-15 fs excitation. The detected optical signal is assigned as two-photon excited fluorescence from hemoglobin. Our findings are supported by wavelength-resolved fluorescence lifetime decay measurements using time-correlated single photon counting system from RBC's, their ghosts as well as in vitro samples of various fluorophores including riboflavin, NADH, NAD(P)H, hemoglobin. We find that low-energy and short-duration pulses allow two-photon imaging of RBC's, but longer more intense pulses lead to their destruction.

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

PubMed

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

2005-01-01

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

Generation of sub-100-fs pulses from a CW mode-locked chromium-doped forsterite laser

NASA Technical Reports Server (NTRS)

Seas, A.; Petricevic, V.; Alfano, R. R.

1992-01-01

Generation of femtosecond pulses from a continuous-wave mode-locked chromium-doped forsterite laser is reported. The forsterite laser was actively mode locked by using an acoustooptic modulator operating at 78 MHz with two Brewster high-dispersion glass prisms for intracavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(00) mode with 85 mW of continuous power (with 1 percent output coupler), tunable over 1230-1280 nm. The shortest pulses measured had a 60-fs pulse width.

Influence of different approaches for dynamical performance optimization of monolithic passive colliding-pulse mode-locked laser diodes emitting around 850 nm

NASA Astrophysics Data System (ADS)

Prziwarka, T.; Klehr, A.; Wenzel, H.; Fricke, J.; Bugge, F.; Weyers, M.; Knigge, A.; Tränkle, G.

2018-02-01

Monolithic laser diodes which generate short infrared pulses in the picosecond and sub-picosecond ranges with high peak power are ideal sources for many applications like e.g. THz-time-domain spectroscopy (TDS) scanning systems. The achievable THz bandwidth is limited by the length of the optical pulses. Due to the fact that colliding-pulse mode locking (CPM) leads to the shortest pulses which could reached by passive mode locking, we experimentally investigated in detail the dynamical and electro optical performance of InGaAsP based quantum well CPM laser diodes with well-established vertical layer structures. Simple design modifications whose implementation is technically easy were realized. Improvements of the device performance in terms of pulse duration, output power, and noise properties are presented in dependence on the different adaptions. From the results we extract an optimized configuration with which we have reached pulses with durations of ≍1.5 ps, a peak power of > 1 W and a pulse-to-pulse timing jitter < 200 fs. The laser diodes emit pulses at a wavelength around 850 nm with a repetition frequency of ≍ 12.4 GHz and could be used as pump source for GaAs antennas to generate THz-radiation. Approaches for reducing pulse width, increasing output power, and improving noise performance are described.

Femtosecond timing distribution and control for next generation accelerators and light sources

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

Chen, Li -Jin

Femtosecond Timing Distribution At LCLS Free-electron-lasers (FEL) have the capability of producing high photon flux from the IR to the hard x-ray wavelength range and to emit femtosecond and eventually even attosecond pulses. This makes them an ideal tool for fundamental as well as applied re-search. Timing precision at the Stanford Linear Coherent Light Source (LCLS) between the x-ray FEL (XFEL) and ultrafast optical lasers is currently no better than 100 fs RMS. Ideally this precision should be much better and could be limited only by the x-ray pulse duration, which can be as short as a few femtoseconds. Anmore » increasing variety of science problems involving electron and nuclear dynamics in chemical and material systems will become accessible as the timing improves to a few femtoseconds. Advanced methods of electron beam conditioning or pulse injection could allow the FEL to achieve pulse durations less than one femtosecond. The objective of the work described in this proposal is to set up an optical timing distribution system based on mode locked Erbium doped fiber lasers at LCLS facility to improve the timing precision in the facility and allow time stamping with a 10 fs precision. The primary commercial applications for optical timing distributions systems are seen in the worldwide accelerator facilities and next generation light sources community. It is reasonable to expect that at least three major XFELs will be built in the next decade. In addition there will be up to 10 smaller machines, such as FERMI in Italy and Maxlab in Sweden, plus the market for upgrading already existing facilities like Jefferson Lab. The total market is estimated to be on the order of a 100 Million US Dollars. The company owns the exclusive rights to the IP covering the technology enabling sub-10 fs synchronization systems. Testing this technology, which has set records in a lab environment, at LCLS, hence in a real world scenario, is an important corner stone of bringing the technology to market.« less

Techniques for the characterization of sub-10-fs optical pulses: a comparison

NASA Astrophysics Data System (ADS)

Gallmann, L.; Sutter, D. H.; Matuschek, N.; Steinmeyer, G.; Keller, U.

Several methods have been proposed for the phase and amplitude characterization of sub-10-fs pulses with nJ energies. An overview of these techniques is presented, with a focus on the comparison of second-harmonic generation frequency-resolved optical gating (SHG-FROG) and spectral phase interferometry for direct electric-field reconstruction (SPIDER). We describe a collinear FROG variant based on type-II phase-matching that completely avoids the geometrical blurring artifact and use both this and SPIDER for the characterization of sub-10-fs Ti:sapphire laser pulses. The results of both methods are compared in an extensive statistical analysis. From this first direct experimental comparison of FROG and SPIDER, guidelines for accurate measurements of sub-10-fs pulses are derived. We point out limitations of both methods for pulses in this ultrashort pulse regime.

Fabrication of amorphous micro-ring arrays in crystalline silicon using ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Fuentes-Edfuf, Yasser; Garcia-Lechuga, Mario; Puerto, Daniel; Florian, Camilo; Garcia-Leis, Adianez; Sanchez-Cortes, Santiago; Solis, Javier; Siegel, Jan

2017-05-01

We demonstrate a simple way to fabricate amorphous micro-rings in crystalline silicon using direct laser writing. This method is based on the fact that the phase of a thin surface layer can be changed into the amorphous phase by irradiation with a few ultrashort laser pulses (800 nm wavelength and 100 fs duration). Surface-depressed amorphous rings with a central crystalline disk can be fabricated without the need for beam shaping, featuring attractive optical, topographical, and electrical properties. The underlying formation mechanism and phase change pathway have been investigated by means of fs-resolved microscopy, identifying fluence-dependent melting and solidification dynamics of the material as the responsible mechanism. We demonstrate that the lateral dimensions of the rings can be scaled and that the rings can be stitched together, forming extended arrays of structures not limited to annular shapes. This technique and the resulting structures may find applications in a variety of fields such as optics, nanoelectronics, and mechatronics.

In-vitro photo-translocation of antiretroviral drug delivery into TZMbl cells

NASA Astrophysics Data System (ADS)

Malabi, Rudzani; Manoto, Sello; Ombinda-Lemboumba, Saturnin; Maaza, Malik; Mthunzi-Kufa, Patience

2017-02-01

The current human immunodeficiency virus (HIV) treatment regime possesses the ability to diminish the viral capacity to unnoticeable levels; however complete eradication of the virus cannot be achieved while latent HIV-1 reservoirs go unchallenged. Therapeutic targeting of HIV therefore requires further investigation and current therapies need modification in order to address HIV eradication. This deflects research towards investigating potential novel antiretroviral drug delivery systems. The use of femtosecond (fs) laser pulses in promoting targeted optical drug delivery of antiretroviral drugs (ARVs) into TZMbl cells revolves around using ultrafast laser pulses that have high peak powers, which precisely disrupt the cell plasma membrane in order to allow immediate transportation and expression of exogenous material into the live mammalian cells. A photo-translocation optical setup was built and validated by characterisation of the accurate parameters such as wavelength (800 nm) and pulse duration (115 fs). Optimisation of drug translocation parameters were done by performing trypan blue translocation studies. Cellular responses were determined via cell viability (Adenosine Triphosphate activity) and cell cytotoxicity (Lactate Dehydrogenase) assays which were done to study the influence of the drugs and laser exposure on the cells. After laser irradiation, high cell viability was observed and low toxicity levels were observed after exposure of the cells to both the ARVs and the laser. Our results confirmed that, with minimal damage and high therapeutic levels of ARVs, the fs laser assisted drug delivery system is efficient with benefits of non-invasive and non-toxic treatment to the cells.

Bright half-cycle optical radiation from relativistic wavebreaking

NASA Astrophysics Data System (ADS)

Miao, Bo; Goers, Andy; Hine, George; Feder, Linus; Salehi, Fatholah; Wahlstrand, Jared; Milchberg, Howard

2015-11-01

Wavebreaking injection of electrons into relativistic plasma wakes generated in near-critical density hydrogen plasmas by sub-terawatt laser pulses is observed to generate an extremely energetic and ultra-broadband radiation flash. The flash is coherent, with a bandwidth of Δλ / λ ~ 0 . 7 consistent with half-cycle optical emission of duration ~ 1 fs from violent unidirectional acceleration of electrons to light speed from rest over a distance much less than the radiated wavelength. We studied the temporal duration and coherence of the flash by interfering it in the frequency domain with a well-characterized Xe supercontinuum pulse. Fringes across the full flash spectrum were observed with high visibility, and the extracted flash spectral phase supports it being a nearly transform-limited pulse. To our knowledge, this is the first evidence of bright half-cycle optical emission. This research is supported by the Defense Threat Reduction Agency, the US Department of Energy, and the Air Force Office of Scientific Research.

Ultrafast Dynamics of a Nucleobase Analogue Illuminated by a Short Intense X-ray Free Electron Laser Pulse

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

Nagaya, K.; Motomura, K.; Kukk, E.

Understanding x-ray radiation damage is a crucial issue for both medical applications of x rays and x-ray free-electron-laser (XFEL) science aimed at molecular imaging. Decrypting the charge and fragmentation dynamics of nucleobases, the smallest units of a macro-biomolecule, contributes to a bottom-up understanding of the damage via cascades of phenomena following x-ray exposure. We investigate experimentally and by numerical simulations the ultrafast radiation damage induced on a nucleobase analogue (5-iodouracil) by an ultrashort (10 fs) high-intensity radiation pulse generated by XFEL at SPring-8 Angstrom Compact free electron Laser (SACLA). The present study elucidates a plausible underlying radiosensitizing mechanism of 5-iodouracil.more » This mechanism is independent of the exact composition of 5-iodouracil and thus relevant to other such radiosensitizers. Furthermore, we found that despite a rapid increase of the net molecular charge in the presence of iodine, and of the ultrafast release of hydrogen, the other atoms are almost frozen within the 10-fs duration of the exposure. Finally, this validates single-shot molecular imaging as a consistent approach, provided the radiation pulse used is brief enough.« less

Toward compact and ultra-intense laser-based soft x-ray lasers

NASA Astrophysics Data System (ADS)

Sebban, S.; Depresseux, A.; Oliva, E.; Gautier, J.; Tissandier, F.; Nejdl, J.; Kozlova, M.; Maynard, G.; Goddet, J. P.; Tafzi, A.; Lifschitz, A.; Kim, H. T.; Jacquemot, S.; Rousseau, P.; Zeitoun, P.; Rousse, A.

2018-01-01

We report here recent work on an optical field ionized (OFI), high-order harmonic-seeded EUV laser. The amplifying medium is a plasma of nickel-like krypton obtained by OFI when focusing a 1 J, 30 fs, circularly-polarized, infrared pulse into a krypton-filled gas cell or krypton gas jet. The lasing transition is the 3d94d (J = 0) → 3d94p (J = 1) transition of Ni-like krypton ions at 32.8 nm and is pumped by collisions with hot electrons. The gain dynamics was probed by seeding the amplifier with a high-order harmonic pulse at different delays. The gain duration monotonically decreased from 7 ps to an unprecedented shortness of 450 fs full width at half-maximum as the amplification peak rose from 150 to 1200 with an increase of the plasma density from 3 × 1018 to 1.2 × 1020 cm-3. The integrated energy of the EUV laser pulse was also measured, and found to be around 2 μJ. It is to be noted that in the ASE mode, longer amplifiers were achieved (up to 2 cm), yielding EUV outputs up to 14 μJ.

Influence of femtosecond laser radiation on cells of the transplantable tumour Krebs-2

NASA Astrophysics Data System (ADS)

Meshalkin, Yu P.; Popova, N. A.; Nikolin, V. P.; Kaledin, V. I.; Kirpichnikov, A. V.; Pestryakov, Efim V.

2012-06-01

The influence of femtosecond radiation of a titaniumsapphire laser on cells of the transplantable ascitic tumour Krebs-2 was studied. After in vitro irradiation by the pulsed fundamentalharmonic radiation with the wavelength 800 nm, pulse duration 30 fs, repetition rate 1 kHz, mean power 100 and 300 mW and exposure time 3 min, as well as by the second-harmonic radiation (40 nm, 50 fs, 120 mW), all cells were diffusely stained by the vital stain trypan blue, which may be an evidence of their death or abnormalities of membrane permeability. However, implantation of such cells to experimental animals led to formation of tumours at the transplantation site with the kinetics slightly different from the control one. In the group of mice to which the cells were inoculated after irradiation with second harmonic pulses of titanium-sapphire laser the inhibition of tumour growth was observed due to partial death of cells under the action of UV spectral components. To explain the mechanism of the observed phenomenon the possibility of pore formation (photoporation) in the cell membrane, described earlier in the papers on foreign DNA transfection into cells, is considered.

Ultrafast Dynamics of a Nucleobase Analogue Illuminated by a Short Intense X-ray Free Electron Laser Pulse

DOE PAGES

Nagaya, K.; Motomura, K.; Kukk, E.; ...

2016-06-16

Understanding x-ray radiation damage is a crucial issue for both medical applications of x rays and x-ray free-electron-laser (XFEL) science aimed at molecular imaging. Decrypting the charge and fragmentation dynamics of nucleobases, the smallest units of a macro-biomolecule, contributes to a bottom-up understanding of the damage via cascades of phenomena following x-ray exposure. We investigate experimentally and by numerical simulations the ultrafast radiation damage induced on a nucleobase analogue (5-iodouracil) by an ultrashort (10 fs) high-intensity radiation pulse generated by XFEL at SPring-8 Angstrom Compact free electron Laser (SACLA). The present study elucidates a plausible underlying radiosensitizing mechanism of 5-iodouracil.more » This mechanism is independent of the exact composition of 5-iodouracil and thus relevant to other such radiosensitizers. Furthermore, we found that despite a rapid increase of the net molecular charge in the presence of iodine, and of the ultrafast release of hydrogen, the other atoms are almost frozen within the 10-fs duration of the exposure. Finally, this validates single-shot molecular imaging as a consistent approach, provided the radiation pulse used is brief enough.« less

Soft x-ray plasma-based seeded multistage amplification chain.

PubMed

Oliva, Eduardo; Fajardo, Marta; Li, Lu; Sebban, Stephane; Ros, David; Zeitoun, Philippe

2012-10-15

To date, plasma-based soft x-ray lasers have demonstrated experimentally 1 μJ, 1 ps (1 MW) pulses. This Letter reports extensive study using time-dependant Maxwell-Bloch code of seeding millimeter scale plasmas that store more than 100 mJ in population inversion. Direct seeding of these plasmas has to overcome very strong amplified spontaneous emission (ASE) as well as prevent wake-field amplification. Below 100 nJ injected energy, seed produces pulses with picosecond duration. To overcome this limitation, a new scheme has been studied, taking advantage of a plasma preamplifier that dramatically increases the seed energy prior to entering the main plasma amplifier leading to ASE and wake-free, fully coherent 21.6 μJ, 80 fs pulses (0.27 GW).

Femtosecond solid-state laser based on a few-layered black phosphorus saturable absorber.

PubMed

Su, Xiancui; Wang, Yiran; Zhang, Baitao; Zhao, Ruwei; Yang, Kejian; He, Jingliang; Hu, Qiangqiang; Jia, Zhitai; Tao, Xutang

2016-05-01

In this Letter, a high-quality, few-layered black phosphorus (BP) saturable absorber (SA) was fabricated successfully, and a femtosecond solid-state laser modulated by BP-SA was experimentally demonstrated for the first time, to the best of our knowledge. Pulses as short as 272 fs were achieved with an average output power of 0.82 W, corresponding to the pulse energy of 6.48 nJ and peak power of 23.8 MW. So far, these represent the shortest pulse duration and highest output power ever obtained with a BP-based mode-locked solid-state laser. The results indicate the promising potential of few-layered BP-SA for applications in solid-state femtosecond mode-locked lasers.

Long-period fiber grating fabricated by 800 nm femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Zhang, Yani; Xi, Yaru; Liu, Sicong; Jiang, Peng; Zhao, Ya; Xu, Qiang

2018-02-01

In this paper, the long period fiber gratings (LPFGs) in standard SMF-28 telecommunication fibers without hydrogen loading were inscribed by using point-to-point direct writing method of femtosecond laser pulses with pulse duration of 100 fs, repetition rate of 1kHz and a central wavelength of 800 nm. The LPFGs with different spectral characteristics were fabricated by adjusting grating period, grating length and duty ratio. The results show that the resonant peak wavelengths shift to the long-wave direction with the increase of the grating length increasing. The variations of duty ratio will lead to the generation of resonance rejection band of LPFGs from singlepeak to multi-peak plus lesser out-of-band loss.

Ultra-fast movies of thin-film laser ablation

NASA Astrophysics Data System (ADS)

Domke, Matthias; Rapp, Stephan; Schmidt, Michael; Huber, Heinz P.

2012-11-01

Ultra-short-pulse laser irradiation of thin molybdenum films from the glass substrate side initiates an intact Mo disk lift off free from thermal effects. For the investigation of the underlying physical effects, ultra-fast pump-probe microscopy is used to produce stop-motion movies of the single-pulse ablation process, initiated by a 660-fs laser pulse. The ultra-fast dynamics in the femtosecond and picosecond ranges are captured by stroboscopic illumination of the sample with an optically delayed probe pulse of 510-fs duration. The nanosecond and microsecond delay ranges of the probe pulse are covered by an electronically triggered 600-ps laser. Thus, the setup enables an observation of general laser ablation processes from the femtosecond delay range up to the final state. A comparison of time- and space-resolved observations of film and glass substrate side irradiation of a 470-nm molybdenum layer reveals the driving mechanisms of the Mo disk lift off initiated by glass-side irradiation. Observations suggest that a phase explosion generates a liquid-gas mixture in the molybdenum/glass interface about 10 ps after the impact of the pump laser pulse. Then, a shock wave and gas expansion cause the molybdenum layer to bulge, while the enclosed liquid-gas mixture cools and condenses at delay times in the 100-ps range. The bulging continues for approximately 20 ns, when an intact Mo disk shears and lifts off at a velocity of above 70 m/s. As a result, the remaining hole is free from thermal effects.

Observation of 690 MV m -1 Electron Accelerating Gradient with a Laser-Driven Dielectric Microstructure

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

Wootton, K. P.; Wu, Z.; Cowan, B. M.

Acceleration of electrons using laser-driven dielectric microstructures is a promising technology for the miniaturization of particle accelerators. In this work, experimental results are presented of relativistic electron acceleration with 690±100 MVm -1 gradient. This is a record-high accelerating gradient for a dielectric microstructure accelerator, nearly doubling the previous record gradient. To reach higher acceleration gradients the present experiment employs 90 fs duration laser pulses.

Nonlinear excitation fluorescence microscopy: source considerations for biological applications

NASA Astrophysics Data System (ADS)

Wokosin, David L.

2008-02-01

Ultra-short-pulse solid-state laser sources have improved contrast within fluorescence imaging and also opened new windows of investigation in biological imaging applications. Additionally, the pulsed illumination enables harmonic scattering microscopy which yields intrinsic structure, symmetry and contrast from viable embryos, cells and tissues. Numerous human diseases are being investigated by the combination of (more) intact dynamic tissue imaging of cellular function with gene-targeted specificity and electrophysiology context. The major limitation to more widespread use of multi-photon microscopy has been the complete system cost and added complexity above and beyond commercial camera and confocal systems. The current status of all-solid-state ultrafast lasers as excitation sources will be reviewed since these lasers offer tremendous potential for affordable, reliable, "turnkey" multiphoton imaging systems. This effort highlights the single box laser systems currently commercially available, with defined suggestions for the ranges for individual laser parameters as derived from a biological and fluorophore limited perspective. The standard two-photon dose is defined by 800nm, 10mW, 200fs, and 80Mhz - at the sample plane for tissue culture cells, i.e. after the full scanning microscope system. Selected application-derived excitation wavelengths are well represented by 700nm, 780nm, ~830nm, ~960nm, 1050nm, and 1250nm. Many of the one-box lasers have fixed or very limited excitation wavelengths available, so the lasers will be lumped near 780nm, 800nm, 900nm, 1050nm, and 1250nm. The following laser parameter ranges are discussed: average power from 200mW to 2W, pulse duration from 70fs to 700fs, pulse repetition rate from 20MHz to 200MHz, with the laser output linearly polarized with an extinction ratio at least 100:1.

Laser lift-off scribing of the CZTSe thin-film solar cells at different pulse durations

DOE PAGES

Markauskas, Edgaras; Gečys, Paulius; Repins, Ingrid; ...

2017-04-27

Here, the transition to fully sized solar modules requires additional three-step laser structuring processes to preserve small-scale cell efficiencies over the large areas. The adjacent cell isolation (the P3 scribe) was found to be the most sensitive process in the case of laser induced damage. The laser induced layer lift-off mechanism seems to be a very attractive process for the P3 patterning, since almost all the laser affected material is removed by mechanical spallation. However, a laser induced layer spallation behavior together with scribe electrical validation under the different laser pulse durations was not investigated extensively in the past. Therefore,more » we report our novel results on the P2 and P3 laser lift-off processing of the Cu 2ZnSn(S, Se 4) (CZTSe) thin-film solar cells covering the pulse duration range from 300 fs to 60 ps. Shorter sub-ps pulses enabled us to process smaller P2 and P3 craters, although the lift-off threshold fluences were higher compared to the longer ps pulses. In the case of the layer lift-off, the laser radiation had to penetrate through the layer stack down to the CZTSe/Mo interface. At shorter sub-ps pulses, the nonlinear effects triggered absorption of the laser radiation in the bulk of the material, resulting in increased damage of the CZTSe layer. The Raman measurements confirmed the CZTSe surface stoichiometry changes for shorter pulses. Furthermore, shorter pulses induced higher electrical conductivity of a scribe, resulting in lower photo-electrical efficiency during the mini-module simulation. In the case of the P3 lift-off scribing, the 10 ps pulses were more favorable than shorter femtosecond pulses.« less

Laser lift-off scribing of the CZTSe thin-film solar cells at different pulse durations

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

Markauskas, Edgaras; Gečys, Paulius; Repins, Ingrid

Here, the transition to fully sized solar modules requires additional three-step laser structuring processes to preserve small-scale cell efficiencies over the large areas. The adjacent cell isolation (the P3 scribe) was found to be the most sensitive process in the case of laser induced damage. The laser induced layer lift-off mechanism seems to be a very attractive process for the P3 patterning, since almost all the laser affected material is removed by mechanical spallation. However, a laser induced layer spallation behavior together with scribe electrical validation under the different laser pulse durations was not investigated extensively in the past. Therefore,more » we report our novel results on the P2 and P3 laser lift-off processing of the Cu 2ZnSn(S, Se 4) (CZTSe) thin-film solar cells covering the pulse duration range from 300 fs to 60 ps. Shorter sub-ps pulses enabled us to process smaller P2 and P3 craters, although the lift-off threshold fluences were higher compared to the longer ps pulses. In the case of the layer lift-off, the laser radiation had to penetrate through the layer stack down to the CZTSe/Mo interface. At shorter sub-ps pulses, the nonlinear effects triggered absorption of the laser radiation in the bulk of the material, resulting in increased damage of the CZTSe layer. The Raman measurements confirmed the CZTSe surface stoichiometry changes for shorter pulses. Furthermore, shorter pulses induced higher electrical conductivity of a scribe, resulting in lower photo-electrical efficiency during the mini-module simulation. In the case of the P3 lift-off scribing, the 10 ps pulses were more favorable than shorter femtosecond pulses.« less

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.

Cavity-dumped femtosecond optical parametric oscillator based on periodically poled stoichiometric lithium tantalate

NASA Astrophysics Data System (ADS)

Yoon, E.; Joo, T.

2016-03-01

A synchronously pumped cavity-dumped femtosecond optical parametric oscillator (OPO) based on a periodically poled stoichiometric lithium tantalate (PPSLT) crystal is reported. The OPO runs in positive group velocity dispersion (GVD) mode to deliver high pulse energy at high repetition rate. It delivers pulse energy over 130 nJ up to 500 kHz and 70 nJ at 1 MHz of repetition rate at 1100 nm. Pulse duration is as short as 42 fs, and the OPO is tunable in the near infrared region from 1050 to 1200 nm. Dispersion property of the OPO was also explored. The cavity-dumped output carries a positive GVD, which can be compensated easily by an external prism pair, and large negative third order dispersion (TOD), which results in a pedestal in the pulse shape. Approaches to obtain clean pulse shape by reducing the large TOD are proposed.

Selective laser melting of hypereutectic Al-Si40-powder using ultra-short laser pulses

NASA Astrophysics Data System (ADS)

Ullsperger, T.; Matthäus, G.; Kaden, L.; Engelhardt, H.; Rettenmayr, M.; Risse, S.; Tünnermann, A.; Nolte, S.

2017-12-01

We investigate the use of ultra-short laser pulses for the selective melting of Al-Si40-powder to fabricate complex light-weight structures with wall sizes below 100 μ {m} combined with higher tensile strength and lower thermal expansion coefficient in comparison to standard Al-Si alloys. During the cooling process using conventional techniques, large primary silicon particles are formed which impairs the mechanical and thermal properties. We demonstrate that these limitations can be overcome using ultra-short laser pulses enabling the rapid heating and cooling in a non-thermal equilibrium process. We analyze the morphology characteristics and micro-structures of single tracks and thin-walled structures depending on pulse energy, repetition rate and scanning velocity utilizing pulses with a duration of 500 {fs} at a wavelength of 1030 {nm}. The possibility to specifically change and optimize the microstructure is shown.

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

Passively mode-locked soliton femtosecond pulses employing graphene saturable absorber

NASA Astrophysics Data System (ADS)

Lau, K. Y.; Muhammad, F. D.; Latif, A. A.; Abu Bakar, M. H.; Yusoff, Z.; Mahdi, M. A.

2017-09-01

We demonstrate a passively mode-locked fiber laser incorporating graphene thin film (GTF) as saturable absorber (SA). The SA is fabricated by sandwiching the GTF between two single mode fiber ferrules through a fiber adaptor. The transmission loss at 1560 nm and non-linear saturation absorption modulation depth for GTF-SA are 0.8 dB and 2.90%, respectively. An erbium-doped fiber laser cavity is constructed to verify the functionality of GTF-SA and is designed to have net anomalous dispersion. It generates large spectral width of 4.99 nm with pulse repetition rate of 9.655 MHz and pulse width of 670 fs. Net anomalous dispersion and time bandwidth product higher than the sech2 transform-limited pulse validate the experimental result. In short, we demonstrate high performance GTF-SA that is able to generate ultrafast pulse duration in femtosecond range effortlessly with simple and green SA fabrication procedures.

A 12.1-W SESAM mode-locked Yb:YAG thin disk laser

NASA Astrophysics Data System (ADS)

Yingnan, Peng; Zhaohua, Wang; Dehua, Li; Jiangfeng, Zhu; Zhiyi, Wei

2016-05-01

Pumped by a 940 nm fiber-coupled diode laser, a passively mode-locked Yb:YAG thin disk oscillator was demonstrated with a semiconductor saturable absorber mirror (SESAM). 12.1 W mode-locked pulses were obtained with pulse duration of 698 fs at the repetition rate of 57.43 MHz. Measurement showed that the beam quality was close to the diffraction limit. Project supported by the National Key Basic Research Program of China (Grant No. 2013CB922402), the National Major Instrument Program of China (Grant No. 2012YQ120047), and the National Natural Science Foundation of China (Grant No. 61210017).

Pico-second laser materials interactions: mechanisms, material lifetime and performance optimization Ted Laurence(14-ERD-014)

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

Laurence, Ted A.

2016-12-14

Laser-induced damage with ps pulse widths straddles the transition from intrinsic, multiphoton ionization- and avalanche ionization-based ablation with fs pulses to defectdominated, thermal-based damage with ns pulses. We investigated the morphology and scaling of damage for commonly used silica and hafnia coatings as well as fused silica. Using carefully calibrated laser-induced damage experiments, in situ imaging, and high-resolution optical microscopy, atomic force microscopy, and scanning electron microscopy, we showed that defects play an important role in laser-induced damage for pulse durations as short as 1 ps. Three damage morphologies were observed: standard material ablation, ultra-high density pits, and isolated absorbers.more » For 10 ps and longer, the isolated absorbers limited the damage performance of the coating materials. We showed that damage resulting from the isolated absorbers grows dramatically with subsequent pulses for sufficient fluences. For hafnia coatings, we used electric field modeling and experiments to show that isolated absorbers near the surface were affected by the chemical environment (vacuum vs. air) for pulses as short as 10 ps. Coupled with the silica results, these results suggested that improvements in the performance in the 10 -60 ps range have not reached fundamental limits. These findings motivate new efforts, including a new SI LDRD in improving the laser-damage performance of multi-layer dielectric coatings. A damage test facility for ps pulses was developed and automated, and was used for testing production optics for ARC. The resulting software was transferred to other laser test facilities for fs pulses and multiple wavelengths with 30 ps pulses. Additionally, the LDRD supported the retention and promotion of an important staff scientist in high-resolution dynamic microscopy and laser-damage testing.« less

Broadband supercontinuum generation with femtosecond pulse width in erbium-doped fiber laser (EDFL)

NASA Astrophysics Data System (ADS)

Rifin, S. N. M.; Zulkifli, M. Z.; Hassan, S. N. M.; Munajat, Y.; Ahmad, H.

2016-11-01

We demonstrate two flat plateaus and the low-noise spectrum of supercontinuum generation (SCG) in a highly nonlinear fiber (HNLF), injected by an amplified picosecond pulse seed of a carbon nanotube-based passively mode locked erbium-doped fiber laser. A broad spectrum of width approximately 1090 nm spanning the range 1130-2220 nm is obtained and the pulse width is compressed to the shorter duration of 70 fs. Variations of the injected peak power up to 33.78 kW into the HNLF are compared and the broad spectrum SCG profiles slightly expand for each of the injected peak powers. This straightforward configuration of SCG offers low output power and ultra-narrow femtosecond pulse width. The results facilitate the development of all fiber time-domain spectroscopy systems based on the photoconductive antenna technique.

Ultra-Intense Short-Pulse Pair Creation Using the Texas Petawatt Laser

NASA Astrophysics Data System (ADS)

Liang, Edison; Henderson, Alexander; Clarke, Taylor; Taylor, Devin; Chaguine, Petr; Serratto, Kristina; Riley, Nathan; Dyer, Gilliss; Donovan, Michael; Ditmire, Todd

2013-10-01

We report results from the 2012 pair creation experiment using the Texas Petawatt Laser. Up to 1011 positrons per steradian were detected using 100 Joule pulses from the Texas Petawatt Laser to irradiate gold targets, with peak laser intensities up to 1.9 × 1021W/cm2 and pulse durations as short as 130 fs. Positron-to-electron ratios exceeding 20% were measured on some shots. The positron energy, positron yield per unit laser energy, and inferred positron density are significantly higher than those reported in previous experiments. This confirms that, for a given laser energy, higher intensity and shorter pulses irradiating thicker targets are more favorable for pair creation. Narrow-band high-energy positrons up to 23 MeV were observed from thin targets. Supported by DOE Grant DE-SC-0001481 and Rice FIF.

Commercial mode-locked vertical external cavity surface emitting lasers

NASA Astrophysics Data System (ADS)

Head, C. Robin; Paboeuf, David; Ortega, Tiago; Lubeigt, Walter; Bialkowski, Bartlomiej; Lin, Jipeng; Hempler, Nils; Maker, Gareth T.; Malcolm, Graeme P. A.

2018-02-01

This paper presents the latest efforts in the development of commercial optically-pumped semiconductor disk lasers (SDLs) at M Squared Lasers. Two types of SDLs are currently being developed: an ultrafast system and a continuous wave single frequency system under the names of Dragonfly and Infinite, respectively. Both offer a compact, low-cost, easy-to-use and maintenance-free tool for a range of growing markets including nonlinear microscopy and quantum technology. To facilitate consumer uptake of the SDL technology, the performance specifications aim to closely match the currently employed systems. An extended Dragonfly system is being developed targeting the nonlinear microscopy market, which typically requires 1-W average power pulse trains with pulse durations below 200 fs. The pulse repetition frequency (PRF) of the commonly used laser systems, typically Titanium-sapphire lasers, is 80 MHz. This property is particularly challenging for mode-locked SDLs which tend to operate at GHz repetition rates, due to their short upper state carrier lifetime. Dragonfly has found a compromise at 200 MHz to balance mode-locking instabilities with a low PRF. In the ongoing development of Dragonfly, additional pulse compression and nonlinear spectral broadening stages are used to obtain pulse durations as short as 130 fs with an average power of 0.85 W, approaching the required performance. A variant of the Infinite system was adapted to provide a laser source suitable for the first stage of Sr atom cooling at 461 nm. Such a source requires average powers of approximately 1 W with a sub-MHz linewidth. As direct emission in the blue is not a viable approach at this stage, an SDL emitting at 922 nm followed by an M Squared Lasers SolTiS ECD-X doubler is currently under development. The SDL oscillator delivered >1 W of single frequency (RMS frequency noise <150kHz) light at 922 nm.

Ultrafast gigantic photo-response in (EDO-TTF)2PF6 initiated by 10-fs laser pulses

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

Schoenlein, Robert William; Itatani, Jiro; Rini, Matteo

2006-08-07

We photo-exited a charge-ordered organic salt (EDO-TTF)2PF6 with sub-10-fs optical pulses. The photo-induced metallic phase appeared within 80-fs after pumping, characterized by large changes in reflectivity (DELTA R/R~0.8) followed by strong coherent phonon modulation

Investigations of gain redshift in high peak power Ti:sapphire laser systems

NASA Astrophysics Data System (ADS)

Wu, Fenxiang; Yu, Linpeng; Zhang, Zongxin; Li, Wenkai; Yang, Xiaojun; Wu, Yuanfeng; Li, Shuai; Wang, Cheng; Liu, Yanqi; Lu, Xiaoming; Xu, Yi; Leng, Yuxin

2018-07-01

Gain redshift in high peak power Ti:sapphire laser systems can result in narrowband spectral output and hence lengthen the compressed pulse duration. In order to realize broadband spectral output in 10 PW-class Ti:sapphire lasers, the influence on gain redshift induced by spectral pre-shaping, gain distribution of cascaded amplifiers and Extraction During Pumping (EDP) technique have been investigated. The theoretical and experimental results show that the redshift of output spectrum is sensitive to the spectral pre-shaping and the gain distribution of cascaded amplifiers, while insensitive to the pumping scheme with or without EDP. Moreover, the output spectrum from our future 10 PW Ti:sapphire laser is theoretically analyzed based on the investigations above, which indicates that a Fourier-transform limited (FTL) pulse duration of 21 fs can be achieved just by optimizing the spectral pre-shaping and gain distribution in 10 PW-class Ti:sapphire lasers.

Cell optoporation with a sub-15 fs and a 250-fs laser

NASA Astrophysics Data System (ADS)

Breunig, Hans Georg; Batista, Ana; Uchugonova, Aisada; König, Karsten

2016-06-01

We employed two commercially available femtosecond lasers, a Ti:sapphire and a ytterbium-based oscillator, to directly compare from a user's practical point-of-view in one common experimental setup the efficiencies of transient laser-induced cell membrane permeabilization, i.e., of so-called optoporation. The experimental setup consisted of a modified multiphoton laser-scanning microscope employing high-NA focusing optics. An automatic cell irradiation procedure was realized with custom-made software that identified cell positions and controlled relevant hardware components. The Ti:sapphire and ytterbium-based oscillators generated broadband sub-15-fs pulses around 800 nm and 250-fs pulses at 1044 nm, respectively. A higher optoporation rate and posttreatment viability were observed for the shorter fs pulses, confirming the importance of multiphoton effects for efficient optoporation.

All-fiber polarization locked vector soliton laser using carbon nanotubes.

PubMed

Mou, C; Sergeyev, S; Rozhin, A; Turistyn, S

2011-10-01

We report an all-fiber mode-locked erbium-doped fiber laser (EDFL) employing carbon nanotube (CNT) polymer composite film. By using only standard telecom grade components, without any complex polarization control elements in the laser cavity, we have demonstrated polarization locked vector solitons generation with duration of ~583 fs, average power of ~3 mW (pulse energy of 118 pJ) at the repetition rate of ~25.7 MHz. © 2011 Optical Society of America

Pulse compression at 1.06 μm in dispersion-decreasing holey fibers

NASA Astrophysics Data System (ADS)

Tse, M. L. V.; Horak, P.; Price, J. H. V.; Poletti, F.; He, F.; Richardson, D. J.

2006-12-01

We report compression of low-power femtosecond pulses at 1.06 μm in a dispersion-decreasing holey fiber. Near-adiabatic compression of 130 fs pulses down to 60 fs has been observed. Measured spectra and pulse shapes agree well with numerical simulations. Compression factors of ten are possible in optimized fibers.

Nonlinear bubble nucleation and growth following filament and white-light continuum generation induced by a single-shot femtosecond laser pulse into dielectrics based on consideration of the time scale

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

Mizushima, Yuki; Saito, Takayuki, E-mail: saito.takayuki@shizuoka.ac.jp

Bubble nucleation and growth following plasma channeling (filament) and white-light continuum in liquid irradiated by a single-shot fs-pulse were experimentally investigated with close observation of the time scale. Making full use of a new confocal system and time-resolved visualization techniques, we obtained evidence suggestive of a major/minor role of the non-linear/thermal effects during the fs-pulse-induced bubble's fountainhead (10{sup −13} s) and growth (10{sup −7} s), which was never observed with the use of the ns-pulse (i.e., optic cavitation). In this context, the fs-pulse-induced bubble is not an ordinary optic cavitation but rather is nonlinear-optic cavitation. We present the intrinsic differencesmore » in the dominant-time domain of the fs-pulse and ns-pulse excitation, and intriguingly, a mere hundred femtoseconds' excitation predetermines the size of the bubble appearing several microseconds after irradiation. That is, the nucleation happens temporally beyond a six-order-of-magnitude difference.« less

Recurrence of febrile seizure in Yazd, Iran.

PubMed

Fallah, Razieh; Karbasi, Sedighah Akhavan

2010-01-01

Febrile seizure (FS) is the most common problem in pediatric neurology. The purpose of this study was to determine FS recurrence frequency and to evaluate its risk factors. In a descriptive retrospective study, 139 children with first FS, admitted between March 2004 and August 2005 in Yazd Shaheed Sadoughi Hospital, were followed. Seventy-six boys and 63 girls with a mean age of 2.03 +/- 1.21 years were followed for 25.1 +/- 5.5 months. Thirty-seven percent had FS recurrence, with a mean recurrence time of 6.7 +/- 5.9 months. Sixty-five percent of infants and 30% of children >1 year old had FS recurrence. Sixty-three percent of those with seizure occurring in <1 hour of fever duration had FS recurrence, while only 33% of those with seizure after >1 hour of fever duration had FS recurrence. Seizures in children <1 year old and in <1 hour of fever duration were risk factors for FS recurrence.

Atomistic three-dimensional coherent x-ray imaging of nonbiological systems

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

Ho, Phay J.; Knight, Chris; Tegze, Miklos

We computationally study the resolution limits for three-dimensional coherent x-ray diffractive imaging of heavy, nonbiological systems using Ar clusters as a prototype. We treat electronic and nuclear dynamics on an equal footing and remove the frozen-lattice approximation often used in electronic damage studies. We explore the achievable resolution as a function of pulse parameters (fluence level, pulse duration, and photon energy) and particle size. The contribution of combined lattice and electron dynamics is not negligible even for 2 fs pulses, and the Compton scattering is less deleterious than in biological systems for atomic-scale imaging. Although free-electron scattering represents a significantmore » background, we find that recovery of the original structure is in principle possible with 3 angstrom resolution for particles of 11 nm diameter.« less

High-power Femtosecond Optical Parametric Amplification at 1 kHz in BiB(3)O(6) pumped at 800 nm.

PubMed

Petrov, Valentin; Noack, Frank; Tzankov, Pancho; Ghotbi, Masood; Ebrahim-Zadeh, Majid; Nikolov, Ivailo; Buchvarov, Ivan

2007-01-22

Substantial power scaling of a travelling-wave femtosecond optical parametric amplifier, pumped near 800 nm by a 1 kHz Ti:sapphire laser amplifier, is demonstrated using monoclinic BiB(3)O(6) in a two stage scheme with continuum seeding. Total energy output (signal plus idler) exceeding 1 mJ is achieved, corresponding to an intrinsic conversion efficiency of approximately 32% for the second stage. The tunability extends from 1.1 to 2.9 microm. The high parametric gain and broad amplification bandwidth of this crystal allowed the maintenance of the pump pulse duration, leading to pulse lengths less than 140 fs, both for the signal and idler pulses, even at such high output levels.

Atomistic three-dimensional coherent x-ray imaging of nonbiological systems

DOE PAGES

Ho, Phay J.; Knight, Chris; Tegze, Miklos; ...

2016-12-12

We computationally study the resolution limits for three-dimensional coherent x-ray diffractive imaging of heavy, nonbiological systems using Ar clusters as a prototype. We treat electronic and nuclear dynamics on an equal footing and remove the frozen-lattice approximation often used in electronic damage studies. We explore the achievable resolution as a function of pulse parameters (fluence level, pulse duration, and photon energy) and particle size. The contribution of combined lattice and electron dynamics is not negligible even for 2 fs pulses, and the Compton scattering is less deleterious than in biological systems for atomic-scale imaging. Although free-electron scattering represents a significantmore » background, we find that recovery of the original structure is in principle possible with 3 angstrom resolution for particles of 11 nm diameter.« less

Characterization and compression of dissipative-soliton-resonance pulses in fiber lasers

PubMed Central

Li, Daojing; Li, Lei; Zhou, Junyu; Zhao, Luming; Tang, Dingyuan; Shen, Deyuan

2016-01-01

We report numerical and experimental studies of dissipative-soliton-resonance (DSR) in a fiber laser with a nonlinear optical loop mirror. The DSR pulse presents temporally a flat-top profile and a clamped peak power. Its spectrum has a rectangle profile with characteristic steep edges. It shows a unique behavior as pulse energy increases: The rectangle part of the spectrum is unchanged while the newly emerging spectrum sits on the center part and forms a peak. Experimental observations match well with the numerical results. Moreover, the detailed evolution of the DSR pulse compression is both numerically and experimentally demonstrated for the first time. An experimentally obtained DSR pulse of 63 ps duration is compressed down to 760 fs, with low-intensity pedestals using a grating pair. Before being compressed to its narrowest width, the pulse firstly evolves into a cat-ear profile, and the corresponding autocorrelation trace shows a crown shape, which distinguishes itself from properties of other solitons formed in fiber lasers. PMID:27025189

Elemental and Isotopic Analysis of Uranium Oxide an NIST Glass Standards by FEMTOSECOND-LA-ICP-MIC-MS

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

Ebert, Chris; Zamzow, Daniel S.; McBay, Eddie H.

2009-06-01

The objective of this work was to test and demonstrate the analytical figures of merit of a femtosecond-laser ablation (fs-LA) system coupled with an inductively coupled plasma-multi-ion collector-mass spectrometer (ICP-MIC-MS). The mobile fs-LA sampling system was designed and assembled at Ames Laboratory and shipped to Oak Ridge National Laboratory (ORNL), where it was integrated with an ICP-MIC-MS. The test period of the integrated systems was February 2-6, 2009. Spatially-resolved analysis of particulate samples is accomplished by 100-shot laser ablation using a fs-pulsewidth laser and monitoring selected isotopes in the resulting ICP-MS transient signal. The capability of performing high sensitivity, spatiallymore » resolved, isotopic analyses with high accuracy and precision and with virtually no sample preparation makes fs-LA-ICP-MIC-MS valuable for the measurement of actinide isotopes at low concentrations in very small samples for nonproliferation purposes. Femtosecond-LA has been shown to generate particles from the sample that are more representative of the bulk composition, thereby minimizing weaknesses encountered in previous work using nanosecond-LA (ns-LA). The improvement of fs- over ns-LA sampling arises from the different mechanisms for transfer of energy into the sample in these two laser pulse-length regimes. The shorter duration fs-LA pulses induce less heating and cause less damage to the sample than the longer ns pulses. This results in better stoichiometric sampling (i.e., a closer correlation between the composition of the ablated particles and that of the original solid sample), which improves accuracy for both intra- and inter-elemental analysis. The primary samples analyzed in this work are (a) solid uranium oxide powdered samples having different {sup 235}U to {sup 238}U concentration ratios, and (b) glass reference materials (NIST 610, 612, 614, and 616). Solid uranium oxide samples containing {sup 235}U in depleted, natural, and enriched abundances were analyzed as particle aggregates immobilized in a collodion substrate. The uranium oxide samples were nuclear reference materials (CRMs U0002, U005-A, 129-A, U015, U030-A, and U050) obtained from New Brunswick Laboratory-USDOE.« less

Tribological performance of titanium samples oxidized by fs-laser radiation, thermal heating, or electrochemical anodization

NASA Astrophysics Data System (ADS)

Kirner, S. V.; Slachciak, N.; Elert, A. M.; Griepentrog, M.; Fischer, D.; Hertwig, A.; Sahre, M.; Dörfel, I.; Sturm, H.; Pentzien, S.; Koter, R.; Spaltmann, D.; Krüger, J.; Bonse, J.

2018-04-01

Commercial grade-1 titanium samples (Ti, 99.6%) were treated using three alternative methods, (i) femtosecond laser processing, (ii) thermal heat treatment, and (iii) electrochemical anodization, respectively, resulting in the formation of differently conditioned superficial titanium oxide layers. The laser processing (i) was carried out by a Ti:sapphire laser (pulse duration 30 fs, central wavelength 790 nm, pulse repetition rate 1 kHz) in a regime of generating laser-induced periodic surface structures (LIPSS). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning setup for the processing of several square-millimeters large surface areas covered homogeneously by these nanostructures. The differently oxidized titanium surfaces were characterized by optical microscopy, micro Raman spectroscopy, variable angle spectroscopic ellipsometry, and instrumented indentation testing. The tribological performance was characterized in the regime of mixed friction by reciprocating sliding tests against a sphere of hardened steel in fully formulated engine oil as lubricant. The specific tribological performance of the differently treated surfaces is discussed with respect to possible physical and chemical mechanisms.

Formation of laser-induced periodic surface structures on niobium by femtosecond laser irradiation

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

Pan, A.; Dias, A.; Gomez-Aranzadi, M.

2014-05-07

The surface morphology of a Niobium sample, irradiated in air by a femtosecond laser with a wavelength of 800 nm and pulse duration of 100 fs, was examined. The period of the micro/nanostructures, parallel and perpendicularly oriented to the linearly polarized fs-laser beam, was studied by means of 2D Fast Fourier Transform analysis. The observed Laser-Induced Periodic Surface Structures (LIPSS) were classified as Low Spatial Frequency LIPSS (periods about 600 nm) and High Spatial Frequency LIPSS, showing a periodicity around 300 nm, both of them perpendicularly oriented to the polarization of the incident laser wave. Moreover, parallel high spatial frequency LIPSS were observedmore » with periods around 100 nm located at the peripheral areas of the laser fingerprint and overwritten on the perpendicular periodic gratings. The results indicate that this method of micro/nanostructuring allows controlling the Niobium grating period by the number of pulses applied, so the scan speed and not the fluence is the key parameter of control. A discussion on the mechanism of the surface topology evolution was also introduced.« less

X-ray emission as a potential hazard during ultrashort pulse laser material processing

NASA Astrophysics Data System (ADS)

Legall, Herbert; Schwanke, Christoph; Pentzien, Simone; Dittmar, Günter; Bonse, Jörn; Krüger, Jörg

2018-06-01

In laser machining with ultrashort laser pulses unwanted X-ray radiation in the keV range can be generated when a critical laser intensity is exceeded. Even if the emitted X-ray dose per pulse is low, high laser repetition rates can lead to an accumulation of X-ray doses beyond exposure safety limits. For 925 fs pulse duration at a center wavelength of 1030 nm, the X-ray emission was investigated up to an intensity of 2.6 × 1014 W/cm2. The experiments were performed in air with a thin disk laser at a repetition rate of 400 kHz. X-ray spectra and doses were measured for various planar target materials covering a wide range of the periodic table from aluminum to tungsten. Without radiation shielding, the measured radiation doses at this high repetition rate clearly exceed the regulatory limits. Estimations for an adequate radiation shielding are provided.

Conceptual design of sub-exa-watt system by using optical parametric chirped pulse amplification

NASA Astrophysics Data System (ADS)

Kawanaka, J.; Tsubakimoto, K.; Yoshida, H.; Fujioka, K.; Fujimoto, Y.; Tokita, S.; Jitsuno, T.; Miyanaga, N.; Gekko-EXA Design Team

2016-03-01

A 50 PW ultrahigh-peak-power laser has been conceptually designed, which is based on optical parametric chirped pulse amplification (OPCPA). A 250 J DPSSL and a flash- lamp-pumped kJ laser are adopted as new repeatable pump source. The existed LFEX-laser with more than ten kilo joules are used in the final amplifier stage and the OPCPA with the 2x2 tiled pump beams in random phase has been proposed with several ten centimeter aperture. A pulse duration of amplified pulses is set at less than 10 fs. A broadband OPCPA with ∼500 nm of the gain spectral width near 1 μm is required. A partially deuterated KDP (p-DKDP) crystal is one of the most promising nonlinear crystals and our numerical calculation ensured such ultra-broad gain width. p-DKDP crystals with several deuteration ratio have been successfully grown.

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.

Ultrafast laser induced periodic sub-wavelength aluminum surface structures and nanoparticles in air and liquids

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

Kuladeep, Rajamudili; Dar, Mudasir H.; Rao, D. Narayana, E-mail: dnrsp@uohyd.ac.in, E-mail: dnr-laserlab@yahoo.com

2014-09-21

In this communication, we demonstrate the generation of laser-induced periodic sub-wavelength surface structures (LIPSS) or ripples on a bulk aluminum (Al) and Al nanoparticles (NPs) by femtosecond (fs) laser direct writing technique. Laser irradiation was performed on Al surface at normal incidence in air and by immersing in ethanol (C₂H₅OH) and water (H₂O) using linearly polarized Ti:sapphire fs laser pulses of ~110 fs pulse duration and ~800 nm wavelength. Field emission scanning electron microscope is utilized for imaging surface morphology of laser written structures and it reveals that the spatial periodicity as well as the surface morphology of the LIPSSmore » depends on the surrounding dielectric medium and also on the various laser irradiation parameters. The observed LIPSS have been classified as low spatial frequency LIPSS which are perpendicularly oriented to the laser polarization with a periodicity from 460 to 620 nm and high spatial frequency LIPSS which spectacles a periodicity less than 100 nm with the orientation parallel to the polarization of the incident laser beam. Fabricated colloidal solutions, which contain the Al NPs, were characterized by UV-Vis absorption spectroscopy and transmission electron microscopy (TEM). TEM results reveal the formation of internal cavities in Al NPs both in ethanol and water. Formation mechanism of LIPSS and cavities inside the nanoparticles are discussed in detail.« less

Third order nonlinear optical properties of bismuth zinc borate glasses

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

Shanmugavelu, B.; Ravi Kanth Kumar, V. V., E-mail: ravi.phy@pondiuni.edu.in; Kuladeep, R.

2013-12-28

Third order nonlinear optical characterization of bismuth zinc borate glasses are reported here using different laser pulse durations. Bismuth zinc borate glasses with compositions xBi{sub 2}O{sub 3}-30ZnO-(70-x) B{sub 2}O{sub 3} (where x = 30, 35, 40, and 45 mol. %) have been prepared by melt quenching method. These glasses were characterized by Raman, UV-Vis absorption, and Z scan measurements. Raman and UV-Vis spectroscopic results indicate that non-bridging oxygens increase with increase of bismuth content in the glass. Nonlinear absorption and refraction behavior in the nanosecond (ns), picosecond (ps), and femtosecond (fs) time domains were studied in detail. Strong reverse saturable absorption due tomore » dominant two-photon absorption (TPA) was observed with both ps and fs excitations. In the case of ns pulse excitations, TPA and free-carrier absorption processes contribute for the nonlinear absorption. Two-photon absorption coefficient (β) and the absorption cross section due to free carriers (σ{sub e}) are estimated by theoretical fit of the open aperture Z-scan measurements and found to be dependent on the amount of bismuth oxide in the glass composition. In both ns and fs regimes the sign and magnitude of the third order nonlinearity are evaluated, and the optical limiting characteristics are also reported.« less

Thomson Parabola Spectrometer: a powerful tool for on-line plasma analysis

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

Altana, C.; Muoio, A.; Schillaci, F.

2015-07-01

In this paper we report on a new powerful and self-consistent analysis technique aimed in order to get information online on laser generated plasmas. Performance of the method has been carried out during two set of measurement by using two different lasers. The first set of data has been collected at LENS Laboratory of INFN-LNS in Catania by using a laser which produces pulses having energies of 2 J and temporal duration of 6 ns, while the second set of data has been collected at ILIL of INO-CNR in Pisa with a laser system capable of delivering pulses of upmore » to 10 mJ in 40 fs. (authors)« less

Increased x-ray conversion efficiency from ultra high contrast, relativistic laser pulse irradiation of large aspect ratio, vertically aligned nanowires

NASA Astrophysics Data System (ADS)

Hollinger, R. C.; Bargsten, C.; Shlyaptsev, V. N.; Kaymak, V.; Pukhov, A.; Capeluto, M. G.; Wang, Y.; Wang, S.; Rockwood, A.; Curtis, A.; Rocca, J. J.

2016-10-01

Recent experiments at Colorado State University have shown that the effective trapping of clean, Joule-level fs laser pulses of relativistic intensity in arrays of high aspect ratio aligned nanowire creates multi-kev, near solid density, large scale (>4um deep) plasmas. The drastically decreased radiative life time and increased hydrodynamic cooling time from these plasmas increases the x-ray conversion efficiency. We measured a record conversion efficiency of 10% into hv>1KeV photons (2pi steradians), and of 0.3% for hv>6KeV. The experiments used Au and Ni nanowires of 55nm, 80nm and 100nm in diameter with 12% of solid density irradiated by high contrast (>1012) pulses of 60fs FWHM duration from a frequency doubled Ti:Sa laser at intensities of I =5x1019Wcm-2. We also present preliminary results on x-ray emission from Rhodium nanowires in the 19-22KeV range and demonstrate the potential of this picosecond X-ray source in flash radiography. This work was supported by the Fusion Energy Program, Office of Science of the U.S Department of Energy, and by the Defense Threat Reduction Agency Grant HDTRA-1-10-1-0079.

Passivation of black phosphorus saturable absorbers for reliable pulse formation of fiber lasers

NASA Astrophysics Data System (ADS)

Na, Dongsoo; Park, Kichul; Park, Ki-Hwan; Song, Yong-Won

2017-11-01

Black phosphorus (BP) has attracted increasing attention due to its unique electrical properties. In addition, the outstanding optical nonlinearity of BP has been demonstrated in various ways. Its functionality as a saturable absorber, in particular, has been validated in demonstrations of passive mode-locked lasers. However, normally, the performance of BP is degraded eventually by both thermal and chemical damage in ambient conditions. The passivation of BP is the critical issue to guarantee a stable performance of the optical devices. We quantitatively characterized the mode-locked lasers operated by BP saturable absorbers with diversified passivation materials such as polydimethylsiloxane (PDMS) or Al2O3, considering the atomic structure of the materials, and therefore the hydro-permeability of the passivation layers. Unlike the BP layers without passivation, we demonstrated that the Al2O3-passivated BP layer was protected from the surface oxidation reaction in the long-term, and the PDMS-passivated one had a short-term blocking effect. The quantitative analysis showed that the time-dependent characteristics of the pulsed laser without passivation were changed with respect to the pulse duration, spectral width, and time-bandwidth product displaying 550 fs, 2.8 nm, and 0.406, respectively. With passivation, the changes were limited to <43 fs, <0.3 nm, and <0.012, respectively.

Passivation of black phosphorus saturable absorbers for reliable pulse formation of fiber lasers.

PubMed

Na, Dongsoo; Park, Kichul; Park, Ki-Hwan; Song, Yong-Won

2017-11-24

Black phosphorus (BP) has attracted increasing attention due to its unique electrical properties. In addition, the outstanding optical nonlinearity of BP has been demonstrated in various ways. Its functionality as a saturable absorber, in particular, has been validated in demonstrations of passive mode-locked lasers. However, normally, the performance of BP is degraded eventually by both thermal and chemical damage in ambient conditions. The passivation of BP is the critical issue to guarantee a stable performance of the optical devices. We quantitatively characterized the mode-locked lasers operated by BP saturable absorbers with diversified passivation materials such as polydimethylsiloxane (PDMS) or Al 2 O 3 , considering the atomic structure of the materials, and therefore the hydro-permeability of the passivation layers. Unlike the BP layers without passivation, we demonstrated that the Al 2 O 3 -passivated BP layer was protected from the surface oxidation reaction in the long-term, and the PDMS-passivated one had a short-term blocking effect. The quantitative analysis showed that the time-dependent characteristics of the pulsed laser without passivation were changed with respect to the pulse duration, spectral width, and time-bandwidth product displaying 550 fs, 2.8 nm, and 0.406, respectively. With passivation, the changes were limited to <43 fs, <0.3 nm, and <0.012, respectively.

Polarization methods for diode laser excitation of solid state lasers

DOEpatents

Holtom, Gary R.

2008-11-25

A mode-locked laser employs a coupled-polarization scheme for efficient longitudinal pumping by reshaped laser diode bars. One or more dielectric polarizers are configured to reflect a pumping wavelength having a first polarization and to reflect a lasing wavelength having a second polarization. A Yb-doped gain medium can be used that absorbs light having a first polarization and emits light having a second polarization. Using such pumping with laser cavity dispersion control, pulse durations of less than 100 fs can be achieved.

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.

Efficient and controllable thermal ablation induced by short-pulsed HIFU sequence assisted with perfluorohexane nanodroplets.

PubMed

Chang, Nan; Lu, Shukuan; Qin, Dui; Xu, Tianqi; Han, Meng; Wang, Supin; Wan, Mingxi

2018-07-01

A HIFU sequence with extremely short pulse duration and high pulse repetition frequency can achieve thermal ablation at a low acoustic power using inertial cavitation. Because of its cavitation-dependent property, the therapeutic outcome is unreliable when the treatment zone lacks cavitation nuclei. To overcome this intrinsic limitation, we introduced perfluorocarbon nanodroplets as extra cavitation nuclei into short-pulsed HIFU-mediated thermal ablation. Two types of nanodroplets were used with perfluorohexane (PFH) as the core material coated with bovine serum albumin (BSA) or an anionic fluorosurfactant (FS) to demonstrate the feasibility of this study. The thermal ablation process was recorded by high-speed photography. The inertial cavitation activity during the ablation was revealed by sonoluminescence (SL). The high-speed photography results show that the thermal ablation volume increased by ∼643% and 596% with BSA-PFH and FS-PFH, respectively, than the short-pulsed HIFU alone at an acoustic power of 19.5 W. Using nanodroplets, much larger ablation volumes were created even at a much lower acoustic power. Meanwhile, the treatment time for ablating a desired volume significantly reduced in the presence of nanodroplets. Moreover, by adjusting the treatment time, lesion migration towards the HIFU transducer could also be avoided. The SL results show that the thermal lesion shape was significantly dependent on the inertial cavitation in this short-pulsed HIFU-mediated thermal ablation. The inertial cavitation activity became more predictable by using nanodroplets. Therefore, the introduction of PFH nanodroplets as extra cavitation nuclei made the short-pulsed HIFU thermal ablation more efficient by increasing the ablation volume and speed, and more controllable by reducing the acoustic power and preventing lesion migration. Copyright © 2018. Published by Elsevier B.V.

Femtosecond laser induced photodynamic therapy on 5-ALA treated SKMEL-30 cells: an efficient theranostic strategy to combat melanoma.

PubMed

Kars, Meltem Demirel; Kara, Reyhan; Gündoğdu, Yasemin; Kepceoğlu, Abdullah; Kılıç, Hamdi Şükür

2014-06-01

Photodynamic therapy (PDT) is a type of photo-chemotherapy that is based on the application of photosensitizer and irradiation of the region by laser sources. Photosensitizer and light interaction will develop reactive oxygen radicals ((1)O2) in the cells and elimination of cells by apoptosis or necrosis. Metastatic skin cancer cells SKMEL-30 were treated by 5-ALA in dark and then they were irradiated by 90-femtosecond (fs) laser with different pulse powers for different durations. The effects of 5-ALA mediated photodynamic therapy on the cells were determined by XTT proliferation kit and by flow cytometry measurements of Annexin V, 7-AAD and mitochondrial membrane potential alterations. Fluorescent accumulation of protoporphyrin IX was investigated by fluorometry and confocal laser microscope. The viability tests for SKMEL-30 cells treated with different 5-ALA doses and femtosecond laser power and durations demonstrated that 635 nm, 45 mW pulse energy at 90 fs laser pulse applications for 60 sec to 1mM 5-ALA exposed cells decreased the cell proliferation by 30%. Flow cytometric measurements exhibit that PDT caused 63% of mitochondria membrane potential alteration, 30% of cell death in the population by apoptosis and 39% of cells by necrosis. There was 1mM 5-ALA exposure that also exhibited about 32% accumulation of fluorescence in the cells. The pretreatment of the cells with the precursor 5-ALA lets the imaging due to increased protoporphyrin IX fluorescence. This treatment method may be proposed as an effective theranostic strategy for melanoma because of its rapid and effective anticancer consequences. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Investigating radiation induced damage processes with femtosecond x-ray pulses (Conference Presentation)

NASA Astrophysics Data System (ADS)

Song, Changyong

2017-05-01

Interest in high-resolution structure investigation has been zealous, especially with the advent of X-ray free electron lasers (XFELs). The intense and ultra-short X-ray laser pulses ( 10 GW) pave new routes to explore structures and dynamics of single macromolecules, functional nanomaterials and complex electronic materials. In the last several years, we have developed XFEL single-shot diffraction imaging by probing ultrafast phase changes directly. Pump-probe single-shot imaging was realized by synchronizing femtosecond (<10 fs in FWHM) X-ray laser (probe) with femtosecond (50 fs) IR laser (pump) at better than 1 ps resolution. Nanoparticles under intense fs-laser pulses were investigated with fs XFEL pulses to provide insight into the irreversible particle damage processes with nanoscale resolution. Research effort, introduced, aims to extend the current spatio-temporal resolution beyond the present limit. We expect this single-shot dynamic imaging to open new science opportunity with XFELs.

Manipulating femtosecond spin-orbit torques with laser pulse sequences to control magnetic memory states and ringing

NASA Astrophysics Data System (ADS)

Lingos, P. C.; Wang, J.; Perakis, I. E.

2015-05-01

Femtosecond (fs) coherent control of collective order parameters is important for nonequilibrium phase dynamics in correlated materials. Here, we propose such control of ferromagnetic order based on using nonadiabatic optical manipulation of electron-hole (e -h ) photoexcitations to create fs carrier-spin pulses with controllable direction and time profile. These spin pulses are generated due to the time-reversal symmetry breaking arising from nonperturbative spin-orbit and magnetic exchange couplings of coherent photocarriers. By tuning the nonthermal populations of exchange-split, spin-orbit-coupled semiconductor band states, we can excite fs spin-orbit torques that control complex magnetization pathways between multiple magnetic memory states. We calculate the laser-induced fs magnetic anisotropy in the time domain by using density matrix equations of motion rather than the quasiequilibrium free energy. By comparing to pump-probe experiments, we identify a "sudden" out-of-plane magnetization canting displaying fs magnetic hysteresis, which agrees with switchings measured by the static Hall magnetoresistivity. This fs transverse spin-canting switches direction with magnetic state and laser frequency, which distinguishes it from the longitudinal nonlinear optical and demagnetization effects. We propose that sequences of clockwise or counterclockwise fs spin-orbit torques, photoexcited by shaping two-color laser-pulse sequences analogous to multidimensional nuclear magnetic resonance (NMR) spectroscopy, can be used to timely suppress or enhance magnetic ringing and switching rotation in magnetic memories.

CNT-based saturable absorbers with scalable modulation depth for Thulium-doped fiber lasers operating at 1.9 μm

PubMed Central

Sobon, Grzegorz; Duzynska, Anna; Świniarski, Michał; Judek, Jarosław; Sotor, Jarosław; Zdrojek, Mariusz

2017-01-01

In this work, we demonstrate a comprehensive study on the nonlinear parameters of carbon nanotube (CNT) saturable absorbers (SA) as a function of the nanotube film thickness. We have fabricated a set of four saturable absorbers with different CNT thickness, ranging from 50 to 200 nm. The CNTs were fabricated via a vacuum filtration technique and deposited on fiber connector end facets. Each SA was characterized in terms of nonlinear transmittance (i.e. optical modulation depth) and tested in a Thulium-doped fiber laser. We show, that increasing the thickness of the CNT layer significantly increases the modulation depth (up to 17.3% with 200 nm thick layer), which strongly influences the central wavelength of the laser, but moderately affects the pulse duration. It means, that choosing the SA with defined CNT thickness might be an efficient method for wavelength-tuning of the laser, without degrading the pulse duration. In our setup, the best performance in terms of bandwidth and pulse duration (8.5 nm and 501 fs, respectively) were obtained with 100 nm thick CNT layer. This is also, to our knowledge, the first demonstration of a fully polarization-maintaining mode-locked Tm-doped laser based on CNT saturable absorber. PMID:28368014

Food insecurity is associated with poor sleep outcomes among US adults.

PubMed

Ding, Meng; Keiley, Margaret K; Garza, Kimberly B; Duffy, Patricia A; Zizza, Claire A

2015-03-01

Although food insecure (FI) adults are at risk of chronic conditions, little research attention is given to their health behaviors, such as sleep. We examined the associations between adult food security status and sleep duration, sleep latency, and sleep complaints reported to a health care professional. Our population-based sample included 5637 men and 5264 women (≥22 y) who participated in the NHANES 2005-2010. Food security status was assessed with USDA's 10-item adult Food Security Survey Module. Self-reported information about sleep duration, sleep latency, and sleep complaints to a health care professional were used as sleep outcomes. Multiple linear, stratified by sex, and logistic regression models were used to estimate the association between food security status and the 3 sleep outcomes. Very low food secure (FS) women reported significantly shorter sleep duration than fully FS women (difference: -30 ± 5.2 min; P < 0.01); however, no relation to sleep duration was observed among men. Among men, participants who were marginally FS (4 ± 1.1 min), low FS (4 ± 1.7 min), and very low FS (5 ± 1.8 min) reported significantly longer sleep latency than fully FS men (P < 0.05), but no association with sleep latency was observed among women. The divergent patterns in sleep duration and latency were likely because of our reference groups reporting undesirable sleep outcomes; fully FS men reported inadequate sleep and fully FS women reported long sleep latency. Among both men and women, marginally FS (OR: 1.64; 95% CI: 1.24, 2.16), low FS (OR: 1.63; 95% CI: 1.16, 2.30), and very low FS (OR: 1.99; 95% CI: 1.36, 2.92) participants were more likely to report sleep complaints than their fully FS counterparts (P < 0.05). Poor sleep quantity and quality may predispose FI adults to adverse health outcomes. © 2015 American Society for Nutrition.

Photoimaging of the multiple filamentation of femtosecond laser pulses in poly(methyl methacrylate) doped with 2,2-difluoro-4-(9-anthracyl)-6-methyl-1,3,2-dioxaborine

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

Kulchin, Yu N; Vitrik, O B; Chekhlenok, A A

2013-12-31

We have studied the filamentation of femtosecond laser pulses (λ = 800 nm, ∼42 fs pulse duration) in poly(methyl methacrylate) doped with 2,2-difluoro-4-(9-anthracyl)-6-methyl-1,3,2- dioxaborine and the associated photomodification of the material. The results demonstrate that multiple filamentation occurs at pulse energies above 5 μJ. At a pulse energy of 1.5 mJ, it is accompanied by supercontinuum generation. The average filament length in PMMA is 9 mm and the filament diameter is ∼10 μm. An incident power density of ∼10{sup 12} W cm{sup -2} ensures inscription of the filament pattern owing to two-photon photochemical processes. Preliminary exposure to continuous light atmore » λ = 400 nm enables an ordered filament pattern to be written. (interaction of laser radiation with matter)« less

Temperature control of the ultra-short laser pulse compression in a one-dimensional photonic band gap structure with nematic liquid crystal as a defect layer

NASA Astrophysics Data System (ADS)

Shiri, Ramin; Safari, Ebrahim; Bananej, Alireza

2018-04-01

We investigate numerically the controllable chirped pulse compression in a one-dimensional photonic structure containing a nematic liquid crystal defect layer using the temperature dependent refractive index of the liquid crystal. We consider the structure under irradiation by near-infrared ultra-short laser pulses polarized parallel to the liquid crystal director at a normal angle of incidence. It is found that the dispersion behaviour and consequently the compression ability of the system can be changed in a controlled manner due to the variation in the defect temperature. When the temperature increased from 290 to 305 K, the transmitted pulse duration decreased from 75 to 42 fs in the middle of the structure, correspondingly. As a result, a novel low-loss tunable pulse compressor with a really compact size and high compression factor is achieved. The so-called transfer matrix method is utilized for numerical simulations of the band structure and reflection/transmission spectra of the structure under investigation.

Rippled area formed by surface plasmon polaritons upon femtosecond laser double-pulse irradiation of silicon.

PubMed

Derrien, Thibault J-Y; Krüger, Jörg; Itina, Tatiana E; Höhm, Sandra; Rosenfeld, Arkadi; Bonse, Jörn

2013-12-02

The formation of near-wavelength laser-induced periodic surface structures (LIPSS) on silicon upon irradiation with sequences of Ti:sapphire femtosecond laser pulse pairs (pulse duration 150 fs, central wavelength 800 nm) is studied theoretically. For this purpose, the nonlinear generation of conduction band electrons in silicon and their relaxation is numerically calculated using a two-temperature model approach including intrapulse changes of optical properties, transport, diffusion and recombination effects. Following the idea that surface plasmon polaritons (SPP) can be excited when the material turns from semiconducting to metallic state, the "SPP active area" is calculated as function of fluence and double-pulse delay up to several picoseconds and compared to the experimentally observed rippled surface areas. Evidence is presented that multi-photon absorption explains the large increase of the rippled area for temporally overlapping pulses. For longer double-pulse delays, relevant relaxation processes are identified. The results demonstrate that femtosecond LIPSS on silicon are caused by the excitation of SPP and can be controlled by temporal pulse shaping.

Polymers Used as Fuel for Laser Plasma Thrusters in Small Satellites

DTIC Science & Technology

2006-09-12

irradiation fluences 100 ns after the laser pulse . The velocity of the maximum intensity versus the irradiation fluence is plotted in Fig. 61. The...The first region can be assigned to ionized elements that have been accelerated by a fs laser pulse induced coulomb explosion on the sample surface...acquired for ns laser pulses , plasma studies for fs laser pulse irradiation were performed. This data allowed a comparison of thrust

Solving the jitter problem in microwave compressed ultrafast electron diffraction instruments: Robust sub-50 fs cavity-laser phase stabilization

PubMed Central

Otto, M. R.; René de Cotret, L. P.; Stern, M. J.; Siwick, B. J.

2017-01-01

We demonstrate the compression of electron pulses in a high-brightness ultrafast electron diffraction instrument using phase-locked microwave signals directly generated from a mode-locked femtosecond oscillator. Additionally, a continuous-wave phase stabilization system that accurately corrects for phase fluctuations arising in the compression cavity from both power amplification and thermal drift induced detuning was designed and implemented. An improvement in the microwave timing stability from 100 fs to 5 fs RMS is measured electronically, and the long-term arrival time stability (>10 h) of the electron pulses improves to below our measurement resolution of 50 fs. These results demonstrate sub-relativistic ultrafast electron diffraction with compressed pulses that is no longer limited by laser-microwave synchronization. PMID:28852686

Ultrafast spintronics roadmap: from femtosecond spin current pulses to terahertz non-uniform spin dynamics via nano-confined spin transfer torques (Conference Presentation)

NASA Astrophysics Data System (ADS)

Melnikov, Alexey; Razdolski, Ilya; Alekhin, Alexandr; Ilin, Nikita; Meyburg, Jan; Diesing, Detlef; Roddatis, Vladimir; Rungger, Ivan; Stamenova, Maria; Sanvito, Stefano; Bovensiepen, Uwe

2016-10-01

Further development of spintronics requires miniaturization and reduction of characteristic timescales of spin dynamics combining the nanometer spatial and femtosecond temporal ranges. These demands shift the focus of interest towards the fundamental open question of the interaction of femtosecond spin current (SC) pulses with a ferromagnet (FM). The spatio-temporal properties of the spin transfer torque (STT) exerted by ultrashort SC pulses on the FM open the time domain for studying STT fingerprint on spatially non-uniform magnetization dynamics. Using the sensitivity of magneto-induced second harmonic generation to SC, we develop technique for SC monitoring. With 20 fs resolution, we demonstrate the generation of 250 fs-long SC pulses in Fe/Au/Fe/MgO(001) structures. Their temporal profile indicates (i) nearly-ballistic hot electron transport in Au and (ii) that the pulse duration is primarily determined by the thermalization time of laser-excited hot carriers in Fe. Together with strongly spin-dependent Fe/Au interface transmission calculated for these carriers, this suggests the non-thermal spin-dependent Seebeck effect dominating the generation of ultrashort SC pulses. The analysis of SC transmission/reflection at the Au/Fe interface shows that hot electron spins orthogonal to the Fe magnetization rotate gaining huge parallel (anti-parallel) projection in transmitted (reflected) SC. This is accompanied by a STT-induced perturbation of the magnetization localized at the interface, which excites the inhomogeneous high-frequency spin dynamics in the FM. Time-resolved magneto-optical studies reveal the excitation of several standing spin wave modes in the Fe film with their spectrum extending up to 0.6 THz and indicating the STT spatial confinement to 2 nm.

Femtosecond laser-controlled self-assembly of amorphous-crystalline nanogratings in silicon

NASA Astrophysics Data System (ADS)

Puerto, Daniel; Garcia-Lechuga, Mario; Hernandez-Rueda, Javier; Garcia-Leis, Adianez; Sanchez-Cortes, Santiago; Solis, Javier; Siegel, Jan

2016-07-01

Self-assembly (SA) of molecular units to form regular, periodic extended structures is a powerful bottom-up technique for nanopatterning, inspired by nature. SA can be triggered in all classes of solid materials, for instance, by femtosecond laser pulses leading to the formation of laser-induced periodic surface structures (LIPSS) with a period slightly shorter than the laser wavelength. This approach, though, typically involves considerable material ablation, which leads to an unwanted increase of the surface roughness. We present a new strategy to fabricate high-precision nanograting structures in silicon, consisting of alternating amorphous and crystalline lines, with almost no material removal. The strategy can be applied to static irradiation experiments and can be extended into one and two dimensions by scanning the laser beam over the sample surface. We demonstrate that lines and areas with parallel nanofringe patterns can be written by an adequate choice of spot size, repetition rate and scan velocity, keeping a constant effective pulse number (N eff) per area for a given laser wavelength. A deviation from this pulse number leads either to inhomogeneous or ablative structures. Furthermore, we demonstrate that this approach can be used with different laser systems having widely different wavelengths (1030 nm, 800 nm, 400 nm), pulse durations (370 fs, 100 fs) and repetition rates (500 kHz, 100 Hz, single pulse) and that the grating period can also be tuned by changing the angle of laser beam incidence. The grating structures can be erased by irradiation with a single nanosecond laser pulse, triggering recrystallization of the amorphous stripes. Given the large differences in electrical conductivity between the two phases, our structures could find new applications in nanoelectronics.

Femtosecond laser-controlled self-assembly of amorphous-crystalline nanogratings in silicon.

PubMed

Puerto, Daniel; Garcia-Lechuga, Mario; Hernandez-Rueda, Javier; Garcia-Leis, Adianez; Sanchez-Cortes, Santiago; Solis, Javier; Siegel, Jan

2016-07-01

Self-assembly (SA) of molecular units to form regular, periodic extended structures is a powerful bottom-up technique for nanopatterning, inspired by nature. SA can be triggered in all classes of solid materials, for instance, by femtosecond laser pulses leading to the formation of laser-induced periodic surface structures (LIPSS) with a period slightly shorter than the laser wavelength. This approach, though, typically involves considerable material ablation, which leads to an unwanted increase of the surface roughness. We present a new strategy to fabricate high-precision nanograting structures in silicon, consisting of alternating amorphous and crystalline lines, with almost no material removal. The strategy can be applied to static irradiation experiments and can be extended into one and two dimensions by scanning the laser beam over the sample surface. We demonstrate that lines and areas with parallel nanofringe patterns can be written by an adequate choice of spot size, repetition rate and scan velocity, keeping a constant effective pulse number (N eff) per area for a given laser wavelength. A deviation from this pulse number leads either to inhomogeneous or ablative structures. Furthermore, we demonstrate that this approach can be used with different laser systems having widely different wavelengths (1030 nm, 800 nm, 400 nm), pulse durations (370 fs, 100 fs) and repetition rates (500 kHz, 100 Hz, single pulse) and that the grating period can also be tuned by changing the angle of laser beam incidence. The grating structures can be erased by irradiation with a single nanosecond laser pulse, triggering recrystallization of the amorphous stripes. Given the large differences in electrical conductivity between the two phases, our structures could find new applications in nanoelectronics.

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.

Time- and frequency-dependent model of time-resolved coherent anti-Stokes Raman scattering (CARS) with a picosecond-duration probe pulse.

PubMed

Stauffer, Hans U; Miller, Joseph D; Slipchenko, Mikhail N; Meyer, Terrence R; Prince, Benjamin D; Roy, Sukesh; Gord, James R

2014-01-14

The hybrid femtosecond∕picosecond coherent anti-Stokes Raman scattering (fs∕ps CARS) technique presents a promising alternative to either fs time-resolved or ps frequency-resolved CARS in both gas-phase thermometry and condensed-phase excited-state dynamics applications. A theoretical description of time-dependent CARS is used to examine this recently developed probe technique, and quantitative comparisons of the full time-frequency evolution show excellent accuracy in predicting the experimental vibrational CARS spectra obtained for two model systems. The interrelated time- and frequency-domain spectral signatures of gas-phase species produced by hybrid fs∕ps CARS are explored with a focus on gas-phase N2 vibrational CARS, which is commonly used as a thermometric diagnostic of combusting flows. In particular, we discuss the merits of the simple top-hat spectral filter typically used to generate the ps-duration hybrid fs∕ps CARS probe pulse, including strong discrimination against non-resonant background that often contaminates CARS signal. It is further demonstrated, via comparison with vibrational CARS results on a time-evolving solvated organic chromophore, that this top-hat probe-pulse configuration can provide improved spectral resolution, although the degree of improvement depends on the dephasing timescales of the observed molecular modes and the duration and timing of the narrowband final pulse. Additionally, we discuss the virtues of a frequency-domain Lorentzian probe-pulse lineshape and its potential for improving the hybrid fs∕ps CARS technique as a diagnostic in high-pressure gas-phase thermometry applications.

Interaction dynamics of fs-laser induced cavitation bubbles and their impact on the laser-tissue-interaction of modern ophthalmic laser systems

NASA Astrophysics Data System (ADS)

Tinne, N.; Ripken, T.; Lubatschowski, H.; Heisterkamp, A.

2011-07-01

A today well-known laser based treatment in ophthalmology is the LASIK procedure which nowadays includes cutting of the corneal tissue with ultra-short laser pulses. Instead of disposing a microkeratome for cutting a corneal flap, a focused ultra-short laser pulse is scanned below the surface of biological tissue causing the effect of an optical breakdown and hence obtaining a dissection. Inside the tissue, the energy of the laser pulses is absorbed by non-linear processes; as a result a cavitation bubble expands and ruptures the tissue. Hence, positioning of several optical breakdowns side by side generates an incision. Due to a reduction of the amount of laser energy, with a moderate duration of treatment at the same time, the current development of ultra-short pulse laser systems points to higher repetition rates in the range of even Megahertz instead of tens or hundreds of Kilohertz. In turn, this results in a pulse overlap and therefor a probable occurrence of interaction between different optical breakdowns and respectively cavitation bubbles of adjacent optical breakdowns. While the interaction of one single laser pulse with biological tissue is analyzed reasonably well experimentally and theoretically, the interaction of several spatial and temporal following pulses is scarcely determined yet. Thus, the aim of this study is to analyse the dynamic and interaction of two cavitation bubbles by using high speed photography. The applied laser pulse energy, the energy ratio and the spot distance between different cavitation bubbles were varied. Depending on a change of these parameters different kinds of interactions such as a flattening and deformation of bubble shape or jet formation are observed. The effects will be discussed regarding the medical ophthalmic application of fs-lasers. Based on these results a further research seems to be inevitable to comprehend and optimize the cutting effect of ultra-short pulse laser systems with high (> 500 kHz) repetition rates.

Environmentally stable all-PM all-fiber giant chirp oscillator.

PubMed

Erkintalo, Miro; Aguergaray, Claude; Runge, Antoine; Broderick, Neil G R

2012-09-24

We report on an environmentally stable giant chirp oscillator operating at 1030 nm. Thanks to the use of a nonlinear amplifying loop mirror as the mode-locker, we are able to extract pulse energies in excess of 10 nJ from a robust all-PM cavity with no free-space elements. Extensive numerical simulations reveal that the output oscillator energy and duration can simply be up-scaled through the lengthening of the cavity with suitably positioned single-mode fiber. Experimentally, using different cavity lengths we have achieved environmentally stable mode-locking at 10, 3.7 and 1.7 MHz with corresponding pulse energies of 2.3, 10 and 16 nJ. In all cases external grating-pair compression below 400 fs has been demonstrated.

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.

Mimicking bug-like surface structures and their fluid transport produced by ultrashort laser pulse irradiation of steel

NASA Astrophysics Data System (ADS)

Kirner, S. V.; Hermens, U.; Mimidis, A.; Skoulas, E.; Florian, C.; Hischen, F.; Plamadeala, C.; Baumgartner, W.; Winands, K.; Mescheder, H.; Krüger, J.; Solis, J.; Siegel, J.; Stratakis, E.; Bonse, J.

2017-12-01

Ultrashort laser pulses with durations in the fs-to-ps range were used for large area surface processing of steel aimed at mimicking the morphology and extraordinary wetting behaviour of bark bugs (Aradidae) found in nature. The processing was performed by scanning the laser beam over the surface of polished flat sample surfaces. A systematic variation of the laser processing parameters (peak fluence and effective number of pulses per spot diameter) allowed the identification of different regimes associated with characteristic surface morphologies (laser-induced periodic surface structures, i.e., LIPSS, grooves, spikes, etc.). Moreover, different laser processing strategies, varying laser wavelength, pulse duration, angle of incidence, irradiation atmosphere, and repetition rates, allowed to achieve a range of morphologies that resemble specific structures found on bark bugs. For identifying the ideal combination of parameters for mimicking bug-like structures, the surfaces were inspected by scanning electron microscopy. In particular, tilted micrometre-sized spikes are the best match for the structure found on bark bugs. Complementary to the morphology study, the wetting behaviour of the surface structures for water and oil was examined in terms of philic/phobic nature and fluid transport. These results point out a route towards reproducing complex surface structures inspired by nature and their functional response in technologically relevant materials.

Phase-matching of attosecond XUV supercontinuum

NASA Astrophysics Data System (ADS)

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

2008-05-01

Adding a weak second harmonic field to an ellipticity dependent polarization gating field allowed for the production of XUV supercontinua from longer (˜10 fs) input pulses in argon. The spectra support 200 as single isolated pulses. This technique, dubbed double optical gating (DOG), demonstrated a large enhancement of the harmonic yield as compared with polarization gating. These results can be attributed to the reduced depletion of the ground state of the target from the leading edge of the pulse and the increased intensity inside the polarization gate width. Through optimization of the harmonic generation process under the phase matching conditions, we were able to further increase the harmonic flux. The parameters included the target gas pressure, laser focus position, input pulse duration, and polarization gate width. By varying the CE phase of the pulse, we were able to verify that the results were indeed from DOG due to its unique 2 pi dependence on the harmonic spectrum. We were able to extend our results to neon. Its higher ionization potential allowed an extension of the harmonic cutoff for the production of even shorter pulses.

40-fs hydrogen Raman laser

NASA Astrophysics Data System (ADS)

Didenko, N. V.; Konyashchenko, A. V.; Kostryukov, P. V.; Losev, L. L.; Pazyuk, V. S.; Tenyakov, S. Yu; Molchanov, V. Ya; Chizhikov, S. I.; Yushkov, K. B.

2015-12-01

40-fs first Stokes pulses at a wavelength of 1.2 μm were generated in a hydrogen SRS-converter pumped by orthogonally polarised double chirped pulses of a Ti : sapphire laser. To obtain a Stokes pulse close to a transform-limited one, a programmed acousto-optic dispersive delay line was placed between the master oscillator and regenerative amplifier. The energy efficiency of Stokes radiation conversion reached 22%.

Imaging and control of interfering wave packets in a dissociating molecule.

PubMed

Skovsen, Esben; Machholm, Mette; Ejdrup, Tine; Thøgersen, Jan; Stapelfeldt, Henrik

2002-09-23

Using two identical 110 femtosecond (fs) optical pulses separated by 310 fs, we launch two dissociative wave packets in I2. We measure the square of the wave function as a function of both the internuclear separation, /Psi(R)/(2), and of the internuclear velocity, /Psi(v(R))/(2), by ionizing the dissociating molecule with an intense 20 fs probe pulse. Strong interference is observed in both /Psi(R)/(2) and in /Psi(v(R))/(2). The interference, and therefore the shape of the wave function, is controlled through the phase difference between the two dissociation pulses in good agreement with calculations.

Correlation of fetal oxygen saturation to fetal heart rate patterns. Evaluation of fetal pulse oximetry with two different oxisensors.

PubMed

Luttkus, A K; Friedmann, W; Homm-Luttkus, C; Dudenhausen, J W

1998-03-01

The purpose of this study was the correlation of fetal oxygen saturation values to various fetal heart rate patterns, as well as to oxygen saturation values obtained by fetal blood analysis. These objectives need to be evaluated from the perspective that two generations of fetal oxisensors have been used. Two different oxisensor systems (FS10: 660+890 nm and FS14: 735+890 nm) and a blinded pulse oximeter (type N400, Nellcor Puritan Bennett) were utilized to monitor 112 fetuses. All data, including oxygen saturation, fetal heart rate patterns, signal and contact quality were stored on a personal computer and evaluated after delivery. The following median fetal oxygen saturation values were obtained: during reassuring fetal heart rate sequences 54% with the oxisensor FS10 and 48% with the newer FS14 oxisensor, during intervals of variable decelerations 43% with the FS10 oxisensor and 40% with the FS14 oxisensor. These differences between values obtained during normal and abnormal fetal heart rate patterns are significant. Due to non-reassuring fetal heart rate patterns 81 fetal blood analyses were performed. The values of pulse oximetry were 9% higher (6% for the FS14) than those of spectrophotometry. Correlation of both methods was r=0.66 (0.74 for the FS14). In combination with fetal heart rate monitoring, fetal pulse oximetry promises a better differentiation between low and high risk heart rate patterns. Oxygen saturation values from intermittent fetal blood sampling reassure the clinician concerning the accuracy of this new method of intrapartum fetal surveillance and underline the increased quality of the new generation of oxisensor using light of a wavelength of 735 and 890 nm.

InP/InGaP quantum-dot SESAM mode-locked Alexandrite laser

NASA Astrophysics Data System (ADS)

Ghanbari, Shirin; Fedorova, Ksenia A.; Krysa, Andrey B.; Rafailov, Edik U.; Major, Arkady

2018-02-01

A semiconductor saturable absorber mirror (SESAM) passively mode-locked Alexandrite laser was demonstrated. Using an InP/InGaP quantum-dot saturable absorber mirror, pulse duration of 420 fs at 774 nm was obtained. The laser was pumped at 532 nm and generated 325 mW of average output power in mode-locked regime with a pump power of 7.12 W. To the best of our knowledge, this is the first report of a passively mode-locked Alexandrite laser using SESAM in general and quantum-dot SESAM in particular.

Passively mode-locked tunable fiber laser in a soliton regime

NASA Astrophysics Data System (ADS)

Endo, Michiyuki; Ghosh, Gorachand

1999-04-01

A stable, passively mode-locked erbium-doped fiber resonator is developed to generate tunable optical pulses with durations of 270 - 325 fs in the soliton regime. The lasing wavelength is tuned continuously over a wavelength range of 60 nm by rotating a bulk band-pass filter inserted in the resonator with a repetition frequency of 45.4 MHz. We reduced the timing jitter by minimizing the intensity fluctuation of the pump source using a feedback loop and by controlling the influence of airflow and temperature fluctuation of the resonator in a sealed box.

PLEIADES: High Peak Brightness, Subpicosecond Thomson Hard-X-ray source

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

Kuba, J; Anderson, S G; Barty, C J

2003-12-15

The Picosecond Laser-Electron Inter-Action for the Dynamic Evaluation of Structures (PLEIADES) facility, is a unique, novel, tunable (10-200 keV), ultrafast (ps-fs), hard x-ray source that greatly extends the parameter range reached by existing 3rd generation sources, both in terms of x-ray energy range, pulse duration, and peak brightness at high energies. First light was observed at 70 keV early in 2003, and the experimental data agrees with 3D codes developed at LLNL. The x-rays are generated by the interaction of a 50 fs Fourier-transform-limited laser pulse produced by the TW-class FALCON CPA laser and a highly focused, relativistic (20-100 MeV),more » high brightness (1 nC, 0.3-5 ps, 5 mm.mrad, 0.2% energy spread) photo-electron bunch. The resulting x-ray brightness is expected to exceed 10{sup 20} ph/mm{sup 2}/s/mrad{sup 2}/0.1% BW. The beam is well-collimated (10 mrad divergence over the full spectrum, 1 mrad for a single color), and the source is a unique tool for time-resolved dynamic measurements in matter, including high-Z materials.« less

Tribological performance of sub-100-nm femtosecond laser-induced periodic surface structures on titanium

NASA Astrophysics Data System (ADS)

Bonse, J.; Höhm, S.; Koter, R.; Hartelt, M.; Spaltmann, D.; Pentzien, S.; Rosenfeld, A.; Krüger, J.

2016-06-01

Sub-100-nm laser-induced periodic surface structures (LIPSS) were processed on bulk titanium (Ti) surfaces by femtosecond laser pulse irradiation in air (30 fs pulse duration, 790 nm wavelength). The laser peak fluence, the spatial spot overlap, and the number of overscans were optimized in a sample-scanning geometry in order to obtain large surface areas (5 mm × 5 mm) covered homogeneously by the LIPSS. The laser-processed regions were characterized by optical microscopy (OM), white light interference microscopy (WLIM) and scanning electron microscopy (SEM). The friction coefficient of the nanostructured surfaces was tested during 1000 cycles under reciprocal sliding conditions (1 Hz, 1.0 N normal load) against a 10-mm diameter ball of hardened 100Cr6 steel, both in paraffin oil and in engine oil used as lubricants. Subsequently, the corresponding wear tracks were qualified by OM, SEM, and energy dispersive X-ray analyses (EDX). The results of the tribological tests are discussed and compared to that obtained for near wavelength-sized fs-LIPSS, processed under somewhat different irradiation conditions. Some constraints for a beneficial effect of LIPSS on the tribological performance are provided.

0.27 GW Soft X-Ray Pulse Using a Plasma-Based Amplification Chain

NASA Astrophysics Data System (ADS)

Oliva, E.; Fajardo, M.; Velarde, P.; Ros, D.; Sebban, S.; Zeitoun, P.

Seeding plasma-based soft-x-ray lasers (PBSXRL) with high order harmonics (HOH) has been demonstrated in plasmas created from gas targets (Zeitoun et al. in Nature 431:426, 2004 and solid targets (Wang et al. in Nat. Photonics 2:94, 2008), obtaining 1 μJ, 1 ps pulses. Reaching multi-microJoule, hundreds of fs regime is the ultimate goal. Recent papers (Oliva et al. in Opt. Lett. 34(17):2640-2642, 2009; Phys. Rev. E 82(5):056408, 2010) showed that increasing the width (up to 1 mm) of the plasma increases the amplification surface and improves the gain zone properties. Up to 20 μJ could be extracted when seeding but the temporal duration and profile was not studied. Simulations show that the HOH is weakly amplified whereas most of the energy is within a long (several picoseconds) wake induced by the HOH (Al'miev et al. in Phys. Rev. Lett. 99(12):123902, 2007; Kim et al. in Phys. Rev. Lett. 104:053901, 2010). Amplified Spontaneous Emission (ASE) is also present in the output beam. Using the 1D Maxwell-Bloch code DeepOne (Oliva et al. in Phys. Rev. A 84(1):013811, 2011) we will show that fully coherent, wake and ASE-suppressed, 21.6 μJ, 80 fs pulse can be obtained when optimizing at the same time both the seed and the plasma conditions.

Underwater femtosecond laser micromachining of thin nitinol tubes for medical coronary stent manufacture

NASA Astrophysics Data System (ADS)

Muhammad, Noorhafiza; Li, Lin

2012-06-01

Microprofiling of medical coronary stents has been dominated by the use of Nd:YAG lasers with pulse lengths in the range of a few milliseconds, and material removal is based on the melt ejection with a high-pressure gas. As a result, recast and heat-affected zones are produced, and various post-processing procedures are required to remove these defects. This paper reports a new approach of machining stents in submerged conditions using a 100-fs pulsed laser. A comparison is given of dry and underwater femtosecond laser micromachining techniques of nickel-titanium alloy (nitinol) typically used as the material for coronary stents. The characteristics of laser interactions with the material have been studied. A femtosecond Ti:sapphire laser system (wavelength of 800 nm, pulse duration of 100 fs, repetition rate of 1 kHz) was used to perform the cutting process. It is observed that machining under a thin water film resulted in no presence of heat-affected zone, debris, spatter or recast with fine-cut surface quality. At the optimum parameters, the results obtained with dry cutting showed nearly the same cut surface quality as with cutting under water. However, debris and recast formation still appeared on the dry cut, which is based on material vaporization. Physical processes involved during the cutting process in a thin water film, i.e. bubble formation and shock waves, are discussed.

Compact 1.5-GHz intra-burst repetition rate Yb-doped all-PM-fiber laser system for ablation-cooled material removal

NASA Astrophysics Data System (ADS)

Akcaalan, Onder; Kalaycioglu, Hamit; Ilday, F. Omer

Although fs fiber laser systems are powerful technologies for material and tissue processing, limited ablation rates and high energy are drawbacks. Recently, we identified a new regime of laser-material interaction, ablation-cooled laser material removal, where the repetition rate has to be high enough so that the targeted spot size cannot cool down substantially by heat conduction which scales down ablation threshold by several orders of magnitude and reduces thermal effects to the bulk of the target. This opens the door to simplified laser systems for processing. In order to exploit this regime in tissue processing, a compact all-PM-fiber laser amplifier system with an intra-burst repetition rate of 1.5 GHz is developed on a 40 x 65 cm platform. The system is able to produce bursts ranging from 20-ns to 65-ns duration with 20 uJ to 80 uJ total energy, respectively, and pulses with up to 2 uJ individual energy and burst repetition rate ranging from 25 kHz to 200 kHz. The seed signal is generated by a home-built all-normal dispersion oscillator with 385 MHz repetition rate and converted to approximately 1.5 GHz by a multiplier. Amplified pulses are compressed to approximately 250-fs, the shortest pulse width for burst-mode fiber laser systems known to date.

MW peak power Er/Yb-doped fiber femtosecond laser amplifier at 1.5 µm center wavelength

NASA Astrophysics Data System (ADS)

Han, Seongheum; Jang, Heesuk; Kim, Seungman; Kim, Young-Jin; Kim, Seung-Woo

2017-08-01

An erbium (Er)/ytterbium (Yb) co-doped double-clad fiber is configured to amplify single-mode pulses with a high average power of 10 W at a 1.5 µm center wavelength. The pulse duration at the exit of the Er/Yb fiber amplifier is measured to be ~440 fs after grating-based compression. The whole single-mode operation of the amplifier system permits the M 2-value of the output beam quality to be evaluated better than 1.05. By tuning the repetition rate from 100 MHz down to 600 kHz, the pulse peak power is scaled up to 19.1 MW to be the highest ever reported using an Er/Yb single-mode fiber. The proposed amplifier system is well suited for strong-power applications such as free-space LIDAR, non-thermal machining and medical surgery.

Few-femtosecond time-resolved measurements of X-ray free-electron lasers.

PubMed

Behrens, C; Decker, F-J; Ding, Y; Dolgashev, V A; Frisch, J; Huang, Z; Krejcik, P; Loos, H; Lutman, A; Maxwell, T J; Turner, J; Wang, J; Wang, M-H; Welch, J; Wu, J

2014-04-30

X-ray free-electron lasers, with pulse durations ranging from a few to several hundred femtoseconds, are uniquely suited for studying atomic, molecular, chemical and biological systems. Characterizing the temporal profiles of these femtosecond X-ray pulses that vary from shot to shot is not only challenging but also important for data interpretation. Here we report the time-resolved measurements of X-ray free-electron lasers by using an X-band radiofrequency transverse deflector at the Linac Coherent Light Source. We demonstrate this method to be a simple, non-invasive technique with a large dynamic range for single-shot electron and X-ray temporal characterization. A resolution of less than 1 fs root mean square has been achieved for soft X-ray pulses. The lasing evolution along the undulator has been studied with the electron trapping being observed as the X-ray peak power approaches 100 GW.

Generation of 1.5-octave intense infrared pulses by nonlinear interactions in DAST crystal

NASA Astrophysics Data System (ADS)

Vicario, C.; Monoszlai, B.; Arisholm, G.; Hauri, C. P.

2015-09-01

Infrared pulses with large spectral width extending from 1.2 to 3.4 μm are generated in the organic crystal DAST (4-N, N-dimethylamino-4‧-N‧-methylstilbazolium tosylate). The input pulse has a central wavelength of 1.5 μm and 65 fs duration. With 2.8 mJ input energy we obtained up to 700 μJ in the broadened spectrum. The output can be easily scaled up in energy by increasing the crystal size together with the energy and the beam size of the pump. The ultra-broad spectrum is ascribed to cascaded second order processes mediated by the exceptionally large effective χ 2 nonlinearity of DAST, but the shape of the spectrum indicates that a delayed χ 3 process may also be involved. Numerical simulations reproduce the experimental results qualitatively and provide an insight in the mechanisms underlying the asymmetric spectral broadening.

Nanosurgery with near-infrared 12-femtosecond and picosecond laser pulses

NASA Astrophysics Data System (ADS)

Uchugonova, Aisada; Zhang, Huijing; Lemke, Cornelius; König, Karsten

2011-03-01

Laser-assisted surgery based on multiphoton absorption of NIR laser light has great potential for high precision surgery at various depths within the cells and tissues. Clinical applications include refractive surgery (fs-LASIK). The non-contact laser method also supports contamination-free cell nanosurgery. Here we apply femtosecond laser scanning microscopes for sub-100 nm surgery of human cells and metaphase chromosomes. A mode-locked 85 MHz Ti:Sapphire laser with an M-shaped ultrabroad band spectrum (maxima: 770 nm/830 nm) with an in situ pulse duration at the target ranging from 12 femtoseconds up to 3 picoseconds was employed. The effects of laser nanoprocessing in cells and chromosomes have been quantified by atomic force microscopy (AFM) and electron microscopy. These studies demonstrate the potential of extreme ultrashort femtosecond laser pulses at low mean milliwatt powers for sub-100 nm surgery.

Ultrafast transmission electron microscopy using a laser-driven field emitter: Femtosecond resolution with a high coherence electron beam.

PubMed

Feist, Armin; Bach, Nora; Rubiano da Silva, Nara; Danz, Thomas; Möller, Marcel; Priebe, Katharina E; Domröse, Till; Gatzmann, J Gregor; Rost, Stefan; Schauss, Jakob; Strauch, Stefanie; Bormann, Reiner; Sivis, Murat; Schäfer, Sascha; Ropers, Claus

2017-05-01

We present the development of the first ultrafast transmission electron microscope (UTEM) driven by localized photoemission from a field emitter cathode. We describe the implementation of the instrument, the photoemitter concept and the quantitative electron beam parameters achieved. Establishing a new source for ultrafast TEM, the Göttingen UTEM employs nano-localized linear photoemission from a Schottky emitter, which enables operation with freely tunable temporal structure, from continuous wave to femtosecond pulsed mode. Using this emission mechanism, we achieve record pulse properties in ultrafast electron microscopy of 9Å focused beam diameter, 200fs pulse duration and 0.6eV energy width. We illustrate the possibility to conduct ultrafast imaging, diffraction, holography and spectroscopy with this instrument and also discuss opportunities to harness quantum coherent interactions between intense laser fields and free-electron beams. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Dual-wavelength, mode-locked erbium-doped fiber laser employing a graphene/polymethyl-methacrylate saturable absorber.

PubMed

Lau, K Y; Abu Bakar, M H; Muhammad, F D; Latif, A A; Omar, M F; Yusoff, Z; Mahdi, M A

2018-05-14

Mode-locked fiber laser incorporating a saturable absorber is an attractive configuration due to its stability and simple structure. In this work, we demonstrate a dual-wavelength passively mode-locked erbium-doped fiber laser employing a graphene/polymethyl-methacrylate saturable absorber. A laser resonator is developed based on dual cavity architecture with unidirectional signal oscillation, which is connected by a fiber branch sharing a common gain medium and saturable absorber. Dual wavelength mode-locked fiber lasers are observed at approximately 1530 and 1560 nm with 22.6 mW pump power threshold. Soliton pulse circulates in the laser cavity with pulse duration of 900 and 940 fs at shorter and longer wavelengths, respectively. This work presents a viable option in developing a low threshold mode-locked laser source with closely spaced dual wavelength femtosecond pulses in the C-band wavelength region.

Repetition frequency scaling of an all-polarization maintaining erbium-doped mode-locked fiber laser based on carbon nanotubes saturable absorber

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

Sotor, J., E-mail: jaroslaw.sotor@pwr.edu.pl; Sobon, G.; Abramski, K. M.

We demonstrate an all-polarization maintaining (PM), mode-locked erbium (Er)-doped fiber laser based on a carbon nanotubes (CNT) saturable absorber (SA). The laser resonator was maximally simplified by using only one passive hybrid component and a pair of fiber connectors with deposited CNTs. The repetition frequency (F{sub rep}) of such a cost-effective and self-starting mode-locked laser was scaled from 54.3 MHz to 358.6 MHz. The highest F{sub rep} was obtained when the total cavity length was shortened to 57 cm. The laser allows ultrashort pulse generation with the duration ranging from 240 fs to 550 fs. Because the laser components were based on PMmore » fibers the laser was immune to the external perturbations and generated laniary polarized light with the degree of polarization (DOP) of 98.7%.« less

The effect of fibromyalgia syndrome to gravidity, parity and duration of breastfeeding; A prospective study from Turkey.

PubMed

Tulay, Koca Tuba; Emrullah, Tanrikut; Aydin, Arslan; Ciledag, Ozdemir Filiz

2016-01-01

Fibromyalgia syndrome (FS) is a chronic pain disorder usually affecting women in their fertile period of life. However, the relationship between FS and pregnancy has not been studied in depth. The effect of FS on the course of pregnancy is poorly investigated in the current literature. Here we aimed to investigate the effects of FS to menarche age, gravidity, parity and duration of breastfeeding. One hundred and eighty-seven non-pregnant females attending between March 2015-June 2015, to Malatya State Hospital Physical Medicine and Rehabilitation Outpatient Clinic, were included in this prospective study. One hundred eleven (111) of them were diagnosed with FS according to the American Rheumatology Association (ACR) 2010 criteria and were defined as group 1; group 2 comprised of seventy six (76) non-pregnant healthy volunteers. All participants were asked about their menarche age, marriage age, gravidity, parity, duration of breastfeeding by conducting a basic questionnaire survey. Patients' body mass index (BMI) were recorded. Depression parameters were evaluated by Beck Depression Scale (BDS). The average age of the patients was 39.04±9.21 (FS) and 38.47±9.65 (Control) years; first menarche age was at 13.28±1.38 (FS) and 13.59±1.54 years (Control), and marriage age was 20.1±3.62 (FS) and 20.69±3.90 years (Control), respectively. No statistically significant difference was found (p=0.598) between BMI values (FS, 27.76±4.95; Control 26.90±4.56 kg/m(2)). The results from both groups were similar in terms of gravidity, parity, and breastfeeding duration, with no statistically significant differences (p=0.252, 0.093, 0.075, respectively). The only significant difference was found in the depression parameter. The BDS results were statistically different between the groups, found higher in FS group (p=0.000). FS occurs as a result of symptoms such as mood disorder, anxiety, cognitive and sleep disorders, and also hormonal changes; no exact cause has yet been established. The syndrome usually occurs during fertile period of young female. According to the findings of our study, FS has no negative effect on the outcome of gravidity, parity, and duration of breastfeeding in Turkish women. Further studies about the effects of FS on the course of pregnancy are required.

Optimizing Ti:Sapphire laser for quantitative biomedical imaging

NASA Astrophysics Data System (ADS)

James, Jeemol; Thomsen, Hanna; Hanstorp, Dag; Alemán Hérnandez, Felipe Ademir; Rothe, Sebastian; Enger, Jonas; Ericson, Marica B.

2018-02-01

Ti:Sapphire lasers are powerful tools in the field of scientific research and industry for a wide range of applications such as spectroscopic studies and microscopic imaging where tunable near-infrared light is required. To push the limits of the applicability of Ti:Sapphire lasers, fundamental understanding of the construction and operation is required. This paper presents two projects, (i) dealing with the building and characterization of custom built tunable narrow linewidth Ti:Sapphire laser for fundamental spectroscopy studies; and the second project (ii) the implementation of a fs-pulsed commercial Ti:Sapphire laser in an experimental multiphoton microscopy platform. For the narrow linewidth laser, a gold-plated diffraction grating with a Littrow geometry was implemented for highresolution wavelength selection. We demonstrate that the laser is tunable between 700 to 950 nm, operating in a pulsed mode with a repetition rate of 1 kHz and maximum average output power around 350 mW. The output linewidth was reduced from 6 GHz to 1.5 GHz by inserting an additional 6 mm thick etalon. The bandwidth was measured by means of a scanning Fabry Perot interferometer. Future work will focus on using a fs-pulsed commercial Ti:Sapphire laser (Tsunami, Spectra physics), operating at 80 MHz and maximum average output power around 1 W, for implementation in an experimental multiphoton microscopy set up dedicated for biomedical applications. Special focus will be on controlling pulse duration and dispersion in the optical components and biological tissue using pulse compression. Furthermore, time correlated analysis of the biological samples will be performed with the help of time correlated single photon counting module (SPCM, Becker&Hickl) which will give a novel dimension in quantitative biomedical imaging.

Noninvasive intratissue refractive index shaping (IRIS) of the cornea with blue femtosecond laser light.

PubMed

Xu, Lisen; Knox, Wayne H; DeMagistris, Margaret; Wang, Nadan; Huxlin, Krystel R

2011-10-17

To test the feasibility of intratissue refractive index shaping (IRIS) in living corneas by using 400-nm femtosecond (fs) laser pulses (blue-IRIS). To test the hypothesis that the intrinsic two-photon absorption of the cornea allows blue-IRIS to be performed with greater efficacy than when using 800-nm femtosecond laser pulses. Fresh cat corneas were obtained postmortem and cut into six wedges. Blue laser pulses at 400 nm, with 100-fs pulse duration at 80 MHz were used to micromachine phase gratings into each corneal wedge at scanning speeds from 1 to 15 mm/s. Grating lines were 1 μm wide, 5 μm apart, and 150 μm below the anterior corneal surface. Refractive index (RI) changes in micromachined regions were measured immediately by recording the diffraction efficiency of inscribed gratings. Six hours later, the corneas were processed for histology, and TUNEL staining was performed to assess whether blue-IRIS causes cell death. Scanning at 1 and 2 mm/s caused overt corneal damage in the form of bubbles and burns. At faster scanning speeds (5, 10, and 15 mm/s), phase gratings were created in the corneal stroma, which were shown to be pure RI changes ranging from 0.037 to 0.021 in magnitude. The magnitude of RI change was inversely related to scanning speed. TUNEL staining showed cell death only around bubbles and burns. Blue-IRIS can be performed safely and effectively in living cornea. Compared with near-infrared laser pulses, blue-IRIS enhances both achievable RI change and scanning speed without the need to dope the tissue with two-photon sensitizers, increasing the clinical applicability of this technique.

Noninvasive Intratissue Refractive Index Shaping (IRIS) of the Cornea with Blue Femtosecond Laser Light

PubMed Central

Xu, Lisen; Knox, Wayne H.; DeMagistris, Margaret; Wang, Nadan

2011-01-01

Purpose. To test the feasibility of intratissue refractive index shaping (IRIS) in living corneas by using 400-nm femtosecond (fs) laser pulses (blue-IRIS). To test the hypothesis that the intrinsic two-photon absorption of the cornea allows blue-IRIS to be performed with greater efficacy than when using 800-nm femtosecond laser pulses. Methods. Fresh cat corneas were obtained postmortem and cut into six wedges. Blue laser pulses at 400 nm, with 100-fs pulse duration at 80 MHz were used to micromachine phase gratings into each corneal wedge at scanning speeds from 1 to 15 mm/s. Grating lines were 1 μm wide, 5 μm apart, and 150 μm below the anterior corneal surface. Refractive index (RI) changes in micromachined regions were measured immediately by recording the diffraction efficiency of inscribed gratings. Six hours later, the corneas were processed for histology, and TUNEL staining was performed to assess whether blue-IRIS causes cell death. Results. Scanning at 1 and 2 mm/s caused overt corneal damage in the form of bubbles and burns. At faster scanning speeds (5, 10, and 15 mm/s), phase gratings were created in the corneal stroma, which were shown to be pure RI changes ranging from 0.037 to 0.021 in magnitude. The magnitude of RI change was inversely related to scanning speed. TUNEL staining showed cell death only around bubbles and burns. Conclusions. Blue-IRIS can be performed safely and effectively in living cornea. Compared with near-infrared laser pulses, blue-IRIS enhances both achievable RI change and scanning speed without the need to dope the tissue with two-photon sensitizers, increasing the clinical applicability of this technique. PMID:21931133

Laser-induced periodic surface structures on titanium upon single- and two-color femtosecond double-pulse irradiation.

PubMed

Höhm, Sandra; Rosenfeld, Arkadi; Krüger, Jörg; Bonse, Jörn

2015-10-05

Single- and two-color double-fs-pulse experiments were performed on titanium to study the dynamics of the formation of laser-induced periodic surface structures (LIPSS). A Mach-Zehnder inter-ferometer generated polarization controlled (parallel or cross-polarized) double-pulse sequences in two configurations - either at 800 nm only, or at 400 and 800 nm wavelengths. The inter-pulse delays of the individual 50-fs pulses ranged up to some tens of picoseconds. Multiple of these single- or two-color double-fs-pulse sequences were collinearly focused by a spherical mirror to the sample surface. In both experimental configurations, the peak fluence of each individual pulse was kept below its respective ablation threshold and only the joint action of both pulses lead to the formation of LIPSS. Their resulting characteristics were analyzed by scanning electron microscopy and the periods were quantified by Fourier analyses. The LIPSS periods along with the orientation allow a clear identification of the pulse which dominates the energy coupling to the material. A plasmonic model successfully explains the delay-dependence of the LIPSS on titanium and confirms the importance of the ultrafast energy deposition stage for LIPSS formation.

Dispersion management for a sub-10-fs, 10 TW optical parametric chirped-pulse amplifier.

PubMed

Tavella, Franz; Nomura, Yutaka; Veisz, Laszlo; Pervak, Vladimir; Marcinkevicius, Andrius; Krausz, Ferenc

2007-08-01

We report the amplification of three-cycle, 8.5 fs optical pulses in a near-infrared noncollinear optical parametric chirped-pulse amplifier (OPCPA) up to energies of 80 mJ. Improved dispersion management in the amplifier by means of a combination of reflection grisms and a chirped-mirror stretcher allowed us to recompress the amplified pulses to within 6% of their Fourier limit. The novel ultrabroad, ultraprecise dispersion control technology presented in this work opens the way to scaling multiterawatt technology to even shorter pulses by optimizing the OPCPA bandwidth.

Femtosecond laser pulse distortion in Ti:sapphire multipass amplifier by atomic phase shifts

NASA Astrophysics Data System (ADS)

Hwang, Seungjin; Jeong, Jihoon; Cho, Seryeyohan; Lee, Jongmin; Yu, Tae Jun

2017-11-01

We have derived modified Frantz-Nodvik equations that simultaneously account for atomic phase shift (APS) and gain depletion as the chirped laser pulse passes through a gain medium, and have analyzed the effect of temporal pulse distortion in a Ti:sapphire multipass amplifier chain. The combination of APS and gain depletion distorted a temporal pulse and decreased the peak power. The pulse width increased from 21.3 fs to 22.8 fs and the peak power reduced to 89% for the PW class Ti:sapphire CPA laser system in the particular conditions.

Self-phase modulation of submicrojoule femtosecond pulses in a hollow-core photonic-crystal fiber

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

Konorov, S.O.; Sidorov-Biryukov, D.A.; Zheltikov, A.M.

Hollow-core photonic-crystal fibers (PCFs) capable of transporting sub-100-fs pulses of Ti:sapphire laser radiation in one of their transmission peaks centered around 800 nm have been designed and demonstrated. These fibers are shown to enhance self-phase modulation of submicrojoule 100-fs Ti:sapphire laser pulses, allowing a spectral bandwidth of 35 nm to be achieved with an 8-cm PCF sample.

Laser-induced periodic surface structures on 6H-SiC single crystals using temporally delayed femtosecond laser double-pulse trains

NASA Astrophysics Data System (ADS)

Song, Juan; Tao, Wenjun; Song, Hui; Gong, Min; Ma, Guohong; Dai, Ye; Zhao, Quanzhong; Qiu, Jianrong

2016-04-01

In this paper, a time-delay-adjustable double-pulse train with 800-nm wavelength, 200-fs pulse duration and a repetition rate of 1 kHz, produced by a collinear two-beam optical system like a Mach-Zehnder interferometer, was employed for irradiation of 6H-SiC crystal. The dependence of the induced structures on time delay of double-pulse train for parallel-polarization configuration was studied. The results show that as the time delay of collinear parallel-polarization dual-pulse train increased, the induced near-subwavelength ripples (NSWRs) turn from irregular rippled pattern to regularly periodic pattern and have their grooves much deepened. The characteristics timescale for this transition is about 6.24 ps. Besides, the areas of NSWR were found to decay exponentially for time delay from 0 to 1.24 ps and then slowly increase for time delay from 1.24 to 14.24 ps. Analysis shows that multiphoton ionization effect, grating-assisted surface plasmon coupling effect, and timely intervene of second pulse in a certain physical stage experienced by 6H-SiC excited upon first pulse irradiation may contribute to the transition of morphology details.

Fundus oculi pigmentation studies simulating the fs-LASIK process Fundus oculi pigmentation studies simulating the fs-LASIK process

NASA Astrophysics Data System (ADS)

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

2012-06-01

The femtosecond-laser in situ keratomileusis (fs-LASIK) technique has successfully entered the refractive surgery market to correct ametropia by cutting transparent corneal tissue with ultra-short laser pulses based on photodisruption. The laser pulses in the near infrared range (NIR) generate a laser-induced breakdown (LIOB) in the cornea. By propagating through the eye, a certain amount of the pulse is deposited in the cornea and the remaining energy interacts with the strong absorbing tissue behind. Due to the absorption by the retinal pigment epithelium and the transfer of the thermal energy to surrounding tissue, the transmitted energy can induce damage to the retina. The aim of this project was to find out the threshold influences concerning the tissue and the correlation between the results of the macroscopical appraisal and the fundus oculi pigmentation by simulating the fs-LASIK procedure with two various laser systems in the continuous wave (CW) and fs-regime. Therefore ex-vivo determinations were carried out macroscopically and histopathologically on porcine tissue.

Investigation of possible fs-LASIK induced retinal damage

NASA Astrophysics Data System (ADS)

Schumacher, S.; Sander, M.; Stolte, A.; Doepke, C.; Baumgaertner, W.; Lubatschowski, H.

2006-02-01

Rapid development of new laser technologies enabled the application of ultra short lasers in refractive surgery. Focused ultra short laser pulses in near-infrared spectral range can generate a laser induced breakdown (LIB) in the cornea, which will disrupt the tissue. Cutting depth and position can be established by varying the laser focus. The fs-LASIK technique allows both flap and lenticule to be formed by using fs-pulses without the presence of any mechanical impact. During the cutting process not all of the pulse energy is deposited into the cornea; approximately half of the remaining energy propagates through the eye and reaches the retina. Though defocused, the transmitted energy can still induce damage to the retina due to absorption by the retinal pigment epithelium and the transfer of thermal energy to surrounding tissue. The fs-LASIK process was simulated with two laser systems; one continous-wave and one in the fs-regime. For the simulation the exposure time and focusing numerical aperature which defines the retinal spot size were varied. The Damage thresholds of the laser beam exposed eyes were determined in terms of ophthalmoscopic and histopathologic observations.

Formation of short high-power laser radiation pulses in excimer mediums

NASA Astrophysics Data System (ADS)

Losev, V. F., Sr.; Ivanov, N. G.; Panchenko, Yu. N.

2007-06-01

Presently an excimer mediums continue are examined as one of variants for formation of powerful and over powerful pulses of laser radiation with duration from units of nanosecond up to tens femtosecond. The researches on such powerful installations as "NIKE" (USA) and << SUPER ASHURA >>, Japan) proceed in this direction. The main advantage of excimer mediums is the opportunity to work in a frequency mode, absence of restriction on the size of active area, high uniformity of a gas working medium, high efficiency (up to 10 %) and wide spectral range of laser radiation (KrF, XeCl ~ 2nm, XeF (C-A), Xe IICl ~ 50-100 nanometers). Research in area of high quality laser beams formation in excimer mediums and its amplification in high power amplifiers are carried out the long time in Institute of High Current Electronics SB RAS, Tomsk, Russia. The wide aperture XeCl laser system of MELS-4k is used for these investigations. Last time we take part in program on development of high power excimer laser system with a petawatt level of power. This system supposes the formation and amplification high quality laser beams with different pulse duration from units of nanosecond up to tens femtosecond. We research the possibility of laser beams formation in excimer mediums with ps-ns pulse duration having the low noise and divergence near to diffraction limit. In other hand, we are developing the wide aperture XeF(C-A) amplifier with optical pump on base electron accelerator. According to our estimations of the XeF(C-A) amplifier based on the converter of e-beam energy to the Xe II* fluorescence at 172 nm will allow to obtain up to 100 TW peak power in a 30 fs pulse.

Sub-wavelength ripples in fused silica after irradiation of the solid/liquid interface with ultrashort laser pulses.

PubMed

Böhme, R; Vass, C; Hopp, B; Zimmer, K

2008-12-10

Laser-induced backside wet etching (LIBWE) is performed using ultrashort 248 nm laser pulses with a pulse duration of 600 fs to obtain sub-wavelength laser-induced periodic surface structures (LIPSS) on the back surface of fused silica which is in contact with a 0.5 mol l(-1) solution of pyrene in toluene. The LIPSS are strictly one-dimensional patterns, oriented parallel to the polarization of the laser radiation, and have a constant period of about 140 nm at all applied laser fluences (0.33-0.84 J cm(-2)) and pulse numbers (50-1000 pulses). The LIPSS amplitude varies due to the inhomogeneous fluence in the laser spot. The LIPSS are examined with scanning electron microscopy (SEM) and atomic force microscopy (AFM). Their power spectral density (PSD) distribution is analysed at a measured area of 10 µm × 10 µm. The good agreement of the measured and calculated LIPSS periods strongly supports a mechanism based on the interference of surface-scattered and incident waves.

Femtosecond Mode-locked Fiber Laser at 1 μm Via Optical Microfiber Dispersion Management.

PubMed

Wang, Lizhen; Xu, Peizhen; Li, Yuhang; Han, Jize; Guo, Xin; Cui, Yudong; Liu, Xueming; Tong, Limin

2018-03-16

Mode-locked Yb-doped fiber lasers around 1 μm are attractive for high power applications and low noise pulse train generation. Mode-locked fiber lasers working in soliton and stretched-pulse regime outperform others in terms of the laser noise characteristics, mechanical stability and easy maintenance. However, conventional optical fibers always show a normal group velocity dispersion around 1 μm, leading to the inconvenience for necessary dispersion management. Here we show that optical microfibers having a large anomalous dispersion around 1 μm can be integrated into mode-locked Yb-doped fiber lasers with ultralow insertion loss down to -0.06 dB, enabling convenient dispersion management of the laser cavity. Besides, optical microfibers could also be adopted to spectrally broaden and to dechirp the ultrashort pulses outside the laser cavity, giving rise to a pulse duration of about 110 fs. We believe that this demonstration may facilitate all-fiber format high-performance ultrashort pulse generation at 1 μm and may find applications in precision measurements, large-scale facility synchronization and evanescent-field-based optical sensing.

Widely tunable mid-infrared fiber laser source based on soliton self-frequency shift in microstructured tellurite fiber.

PubMed

Koptev, M Yu; Anashkina, E A; Andrianov, A V; Dorofeev, V V; Kosolapov, A F; Muravyev, S V; Kim, A V

2015-09-01

A turnkey fiber laser source generating high-quality pulses with a spectral sech shape and Fourier transform-limited duration of order 100 fs widely tunable in the 1.6-2.65 μm range is presented. It is based on Raman soliton self-frequency shifting in the suspended-core microstructured TeO2-WO3-La2O3 glass fiber pumped by a hybrid Er/Tm fiber system. Detailed experimental and theoretical studies, which are in a very good agreement, of nonlinear pulse dynamics in the tellurite fiber with carefully measured and calculated parameters are reported. A quantitatively verified numerical model is used to show Raman soliton shift in the range well beyond 3 μm for increased pump energy.

Reducing noise in a Raman quantum memory.

PubMed

Bustard, Philip J; England, Duncan G; Heshami, Khabat; Kupchak, Connor; Sussman, Benjamin J

2016-11-01

Optical quantum memories are an important component of future optical and hybrid quantum technologies. Raman schemes are strong candidates for use with ultrashort optical pulses due to their broad bandwidth; however, the elimination of deleterious four-wave mixing noise from Raman memories is critical for practical applications. Here, we demonstrate a quantum memory using the rotational states of hydrogen molecules at room temperature. Polarization selection rules prohibit four-wave mixing, allowing the storage and retrieval of attenuated coherent states with a mean photon number 0.9 and a pulse duration 175 fs. The 1/e memory lifetime is 85.5 ps, demonstrating a time-bandwidth product of ≈480 in a memory that is well suited for use with broadband heralded down-conversion and fiber-based photon sources.

EUV emission stimulated by use of dual laser pulses from continus liquid microjet targets

NASA Astrophysics Data System (ADS)

Higashiguchi, Takeshi; Rajyaguru, Chirag; Sasaki, Wataru; Kubodera, Shoichi

2004-11-01

A continuous water-jet or water-jet mixed with LiF with several tens μm diameter was formed in a vacuum chamber through a small capillary nozzle. Usage of two laser pulses is an efficient way to produce EUV emission, since a density and temperature of a plasma formed by the first laser pulse are regulated by the second laser pulse. By adjusting the delay of the second pulse, one could maximize the EUV emission. A subpicosecond Ti:Sapphire laser at a wavelength of 800 nm produced a maximum energy around 30 mJ. The beam was divided by a Michelson interferometer, which produced two laser pulses with energies of 5 mJ. The pulse duration was adjusted around 300 fs (FWHM). Both beams were focused on a micro-jet using a lens with a focal length of 15 cm. The delay time between the two pulses was varied from 100 to 800 ps by use of an optical delay line. Clear enhancement of the EUV emission yield was observed when the delay between the two pulses was around 500 ps. The experimentally observed delay agrees reasonably well with that of a plasma to expand to its critical density of 10^21 cm-3.

Femtosecond laser induced concentric semi-circular periodic surface structures on silicon based on the quasi-plasmonic annular nanostructure.

PubMed

Han, Weina; Liu, Furong; Yuan, Yanping; Li, Xiaowei; Wang, Qingsong; Wang, Shaojun; Jiang, Lan

2018-05-04

In this study, we report polarization-dependent concentric circular periodic surface structures on Si induced by a single shot femtosecond (fs) laser pulse based on pre-processed quasi-plasmonic annular-shaped nanostructure. An abnormal annular-shaped energy deposition of the fundamental fs laser pulse can be found by using dual-wavelength superposition of the fundamental frequency (ω) and the second-harmonic frequency (2ω) of an fs Ti:sapphire laser, which is confirmed by real beam shape detection. Based on the annular-shaped energy distribution of dual-wavelength fs laser, a concentric quasi-plasmonic corral nanostructure can be imprinted on the Au thin film. Surface plasmon polaritons (SPPs) excitations on the planar metallic nanostructures enable the manipulation of light on subwavelength scales. Thus, the pre-processed concentric quasi-plasmonic corral nanostructure can act as a precursor for the subsequent SPPs excitation and propagation by the fs laser irradiation. Using this technique, polarization-dependent semi-circular periodic surface structures on silicon can be found by the irradiation of fs laser pulse with only one shot. This research provides an additional freedom for the laser induced periodic surface structure (LIPSS) modulation based on the modulation of SPPs excitation and propagation, which plays an important role in the formation of LIPSS.

Femtosecond laser induced concentric semi-circular periodic surface structures on silicon based on the quasi-plasmonic annular nanostructure

NASA Astrophysics Data System (ADS)

Han, Weina; Liu, Furong; Yuan, Yanping; Li, Xiaowei; Wang, Qingsong; Wang, Shaojun; Jiang, Lan

2018-07-01

In this study, we report polarization-dependent concentric circular periodic surface structures on Si induced by a single shot femtosecond (fs) laser pulse based on pre-processed quasi-plasmonic annular-shaped nanostructure. An abnormal annular-shaped energy deposition of the fundamental fs laser pulse can be found by using dual-wavelength superposition of the fundamental frequency (ω) and the second-harmonic frequency (2ω) of an fs Ti:sapphire laser, which is confirmed by real beam shape detection. Based on the annular-shaped energy distribution of dual-wavelength fs laser, a concentric quasi-plasmonic corral nanostructure can be imprinted on the Au thin film. Surface plasmon polaritons (SPPs) excitations on the planar metallic nanostructures enable the manipulation of light on subwavelength scales. Thus, the pre-processed concentric quasi-plasmonic corral nanostructure can act as a precursor for the subsequent SPPs excitation and propagation by the fs laser irradiation. Using this technique, polarization-dependent semi-circular periodic surface structures on silicon can be found by the irradiation of fs laser pulse with only one shot. This research provides an additional freedom for the laser induced periodic surface structure (LIPSS) modulation based on the modulation of SPPs excitation and propagation, which plays an important role in the formation of LIPSS.

Tetravalent chromium (Cr(4+)) as laser-active ion for tunable solid-state lasers

NASA Technical Reports Server (NTRS)

Seas, A.; Petricevic, V.; Alfano, Robert R.

1993-01-01

Major accomplishments under NASA grant NAG-1-1346 are summarized. (1) numerical modeling of the four mirror astigmatically compensated, Z-fold cavity was performed and several design parameters to be used for the construction of a femtosecond forsterite laser were revealed by simulation. (2) femtosecond pulses from a continuous wave mode-locked chromium doped forsterite laser were generated. The forsterite laser was actively mode-locked using an acousto-optic modulator operating at 78 MHz with two Brewster high dispersion glass prisms for intra-cavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(sub 00) mode with 85 mW of continuous power tunable over 1230-1280 nm. The shortest pulses of 60-fs pulsewidth were measured. (3) Self-mode-locked operation of the Cr:forsterite laser was achieved. Synchronous pumping was used to mode lock the forsterite laser resulting in picosecond pulses, which in turn provided the starting mechanism for self-mode-locking. The pulses generated had an FWHM of 105 fs and were tunable between 1230-1270 nm. (4) Numerical calculations indicated that the pair of SF 14 prisms used in the cavity compensated for quadratic phase but introduced a large cubic phase term. Further calculations of other optical glasses indicated that a pair of SFN 64 prisms can introduce the same amount of quadratic phase as SF 14 prisms but introduce a smaller cubic phase. When the SF 14 prisms were replaced by SFN 64 prisms the pulsewidth was reduced to 50 fs. Great improvement was observed in the stability of the self mode-locked forsterite laser and in the ease of achieving mode locking. Using the same experimental arrangement and a new forsterite crystal with improved FOM the pulse width was reduced to 36 fs.

Visible continuum pulses based on enhanced dispersive wave generation for endogenous fluorescence imaging.

PubMed

Cui, Quan; Chen, Zhongyun; Liu, Qian; Zhang, Zhihong; Luo, Qingming; Fu, Ling

2017-09-01

In this study, we demonstrate endogenous fluorescence imaging using visible continuum pulses based on 100-fs Ti:sapphire oscillator and a nonlinear photonic crystal fiber. Broadband (500-700 nm) and high-power (150 mW) continuum pulses are generated through enhanced dispersive wave generation by pumping femtosecond pulses at the anomalous dispersion region near zero-dispersion wavelength of high-nonlinear photonic crystal fibers. We also minimize the continuum pulse width by determining the proper fiber length. The visible-wavelength two-photon microscopy produces NADH and tryptophan images of mice tissues simultaneously. Our 500-700 nm continuum pulses support extending nonlinear microscopy to visible wavelength range that is inaccessible to 100-fs Ti:sapphire oscillators and other applications requiring visible laser pulses.

Optical and thermal properties in ultrafast laser surface nanostructuring on biodegradable polymer

NASA Astrophysics Data System (ADS)

Yada, Shuhei; Terakawa, Mitsuhiro

2015-03-01

We investigate the effect of optical and thermal properties in laser-induced periodic surface structures (LIPSS) formation on a poly-L-lactic acid (PLLA), a biodegradable polymer. Surface properties of biomaterials are known to be one of the key factors in tissue engineering. Methods to process biomaterial surfaces have been studied widely to enhance cell adhesive and anisotropic properties. LIPSS formation has advantages in a dry processing which is able to process complex-shaped surfaces without using a toxic chemical component. LIPSS, however, was difficult to be formed on PLLA due to its thermal and optical properties compared to other polymers. To obtain new perspectives in effect of these properties above, LIPSS formation dependences on wavelength, pulse duration and repetition rate have been studied. At 800 nm of incident wavelength, high-spatial frequency LIPSS (HSFL) was formed after applying 10000 femtosecond pulses at 1.0 J/cm2 in laser fluence. At 400 nm of the wavelength, HSFL was formed at fluences higher than 0.20 J/cm2 with more than 3000 pulses. Since LIPSS was less formed with lower repetition rate, certain heat accumulation may be required for LIPSS formation. With the pulse duration of 2.0 ps, higher laser fluence as well as number of pulses compared to the case of 120 fs was necessary. This indicates that multiphoton absorption process is essential for LIPSS formation. Study on biodegradation modification was also performed.

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.

Laser System for Photoelectron and X-Ray Production in the PLEIADES Compton Light Source

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

Gibson, D J; Barty, C J; Betts, S M

2005-04-21

The PLEIADES (Picosecond Laser-Electron Interaction for the Dynamic Evaluation of Structures) facility provides tunable short x-ray pulses with energies of 30-140 keV and pulse durations of 0.3-5 ps by scattering an intense, ultrashort laser pulse off a 35-75 MeV electron beam. Synchronization of the laser and electron beam is obtained by using a photoinjector gun, and using the same laser system to generate the electrons and the scattering laser. The Ti Ti:Sapphire, chirped pulse amplification based 500 mJ, 50 fs, 810 nm scattering laser and the similar 300 {micro}J, 5 ps, 266 nm photoinjector laser systems are detailed. Additionally, anmore » optical parametric chirped pulse amplification (OPCPA) system is studied as a replacement for part of the scattering laser front end. Such a change would significantly simplify the set-up the laser system by removing the need for active switching optics, as well as increase the pre-pulse contrast ratio which will be important when part of the scattering laser is used as a pump beam in pump-probe diffraction experiments using the ultrashort tunable x-rays generated as the probe.« less

Recombination emissions and spectral blueshift of pump radiation from ultrafast laser induced plasma in a planar water microjet

NASA Astrophysics Data System (ADS)

Anija, M.; Philip, Reji

2009-09-01

We report spectroscopic investigations of an ultrafast laser induced plasma generated in a planar water microjet. Plasma recombination emissions along with the spectral blueshift and broadening of the pump laser pulse contribute to the total emission. The laser pulses are of 100 fs duration, and the incident intensity is around 10 15 W/cm 2. The dominant mechanisms leading to plasma formation are optical tunnel ionization and collisional ionization. Spectrally resolved polarization measurements show that the high frequency region of the emission is unpolarized whereas the low frequency region is polarized. Results indicate that at lower input intensities the emission arises mainly from plasma recombinations, which is accompanied by a weak blueshift of the incident laser pulse. At higher input intensities strong recombination emissions are seen, along with a broadening and asymmetric spectral blueshift of the pump laser pulse. From the nature of the blueshifted laser pulse it is possible to deduce whether the rate of change of free electron density is a constant or variable within the pulse lifetime. Two input laser intensity regimes, in which collisional and tunnel ionizations are dominant respectively, have been thus identified.

Unified model of plasma formation, bubble generation and shock wave emission in water for fs to ns laser pulses (Conference Presentation)

NASA Astrophysics Data System (ADS)

Liang, Xiao-Xuan; Freidank, Sebastian; Linz, Norbert; Paltauf, Günther; Zhang, Zhenxi; Vogel, Alfred

2017-03-01

We developed modeling tools for optical breakdown events in water that span various phases reaching from breakdown initiation via solvated electron generation, through laser induced-plasma formation and temperature evolution in the focal spot to the later phases of cavitation bubble dynamics and shock wave emission and applied them to a large parameter space of pulse durations, wavelengths, and pulse energies. The rate equation model considers the interplay of linear absorption, photoionization, avalanche ionization and recombination, traces thermalization and temperature evolution during the laser pulse, and portrays the role of thermal ionization that becomes relevant for T > 3000 K. Modeling of free-electron generation includes recent insights on breakdown initiation in water via multiphoton excitation of valence band electrons into a solvated state at Eini = 6.6 eV followed by up-conversion into the conduction band level that is located at 9.5 eV. The ability of tracing the temperature evolution enabled us to link the model of laser-induced plasma formation with a hydrodynamic model of plasma-induced pressure evolution and phase transitions that, in turn, traces bubble generation and dynamics as well as shock wave emission. This way, the amount of nonlinear energy deposition in transparent dielectrics and the resulting material modifications can be assessed as a function of incident laser energy. The unified model of plasma formation and bubble dynamics yields an excellent agreement with experimental results over the entire range of investigated pulse durations (femtosecond to nanosecond), wavelengths (UV to IR) and pulse energies.

Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering.

PubMed

Miller, Joseph D; Roy, Sukesh; Slipchenko, Mikhail N; Gord, James R; Meyer, Terrence R

2011-08-01

High-repetition-rate, single-laser-shot measurements are important for the investigation of unsteady flows where temperature and species concentrations can vary significantly. Here, we demonstrate single-shot, pure-rotational, hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps RCARS) thermometry based on a kHz-rate fs laser source. Interferences that can affect nanosecond (ns) and ps CARS, such as nonresonant background and collisional dephasing, are eliminated by selecting an appropriate time delay between the 100-fs pump/Stokes pulses and the pulse-shaped 8.4-ps probe. A time- and frequency-domain theoretical model is introduced to account for rotational-level dependent collisional dephasing and indicates that the optimal probe-pulse time delay is 13.5 ps to 30 ps. This time delay allows for uncorrected best-fit N2-RCARS temperature measurements with ~1% accuracy. Hence, the hybrid fs/ps RCARS approach can be performed with kHz-rate laser sources while avoiding corrections that can be difficult to predict in unsteady flows.

Single-shot gas-phase thermometry using pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering

NASA Astrophysics Data System (ADS)

Miller, Joseph D.; Roy, Sukesh; Slipchenko, Mikhail N.; Gord, James R.; Meyer, Terrence R.

2011-08-01

High-repetition-rate, single-laser-shot measurements are important for the investigation of unsteady flows where temperature and species concentrations can vary significantly. Here, we demonstrate single-shot, pure-rotational, hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps RCARS) thermometry based on a kHz-rate fs laser source. Interferences that can affect nanosecond (ns) and ps CARS, such as nonresonant background and collisional dephasing, are eliminated by selecting an appropriate time delay between the 100-fs pump/Stokes pulses and the pulse-shaped 8.4-ps probe. A time- and frequency-domain theoretical model is introduced to account for rotational-level dependent collisional dephasing and indicates that the optimal probe-pulse time delay is 13.5 ps to 30 ps. This time delay allows for uncorrected best-fit N2-RCARS temperature measurements with ~1% accuracy. Hence, the hybrid fs/ps RCARS approach can be performed with kHz-rate laser sources while avoiding corrections that can be difficult to predict in unsteady flows.

Femtosecond laser processing of NiPd single and 5x(Ni/Pd) multilayer thin films

NASA Astrophysics Data System (ADS)

Petrović, S.; Gaković, B.; Zamfirescu, M.; Radu, C.; Peruško, D.; Radak, B.; Ristoscu, C.; Zdravković, S.; Luculescu, C. L.; Mihailescu, I. N.

2017-09-01

Modification of single and complex nickel-palladium samples by laser processing in the femtosecond time domain was studied. The samples were processed by focused Ti:Sapphire laser beam (Clark CPA-2101) with 775 nm laser wavelength, 2 kHz repetition rate, 200 fs pulse duration. The laser-induced morphological modifications have shown dependence on the applied fluences and number of laser pulses. The formed surface nanostructures on the single NiPd/Si and multilayer 5x(Ni/Pd)/Si systems are compared with individual Ni and Pd thin films. The results show an increase in surface roughness, formation of parallel periodic surface structures, appearance of hydrodynamic features and ablation of surface material. At low number of pulses (less than 10 pulses) and low pulse energies range (not over 1.7 μJ), the two types of laser-induced periodic surface structure (LIPSS) can be observed: low and high spatial frequency LIPSS (HSFL and LSFL). For all samples, the measured LSFL periods were 720 nm for the ripples created solely on thin film surfaces during the single pulse action. In the case of the multi-pulse irradiation, the periodicities of created LSFLs on the all investigated thin films have shown tendency to reduction with increasing of pulse energies.

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.

Single-shot pulse duration and intensity diagnostic for 10-ps MeV gamma pulses based on interferometry

NASA Astrophysics Data System (ADS)

Peng, Bo-dong; Hei, Dong-wei; Song, Yan; Liu, Jun; Zhao, Jun

2018-04-01

To measure the temporal width and the intensity evolution versus time of a MeV gamma pulse generated by a Compton Scatter Source, a time-space conversion method is proposed. This design is based on the consideration that the temporal length of the MeV pulse is proportional to the spatial length of the pulse in a certain semiconductor. The spatial length and the intensity evolution versus time of the MeV pulse can be obtained by recording the region of the refractive index change that is induced by the MeV pulse. The simulation suggests that the equivalent temporal spread of a mono-energy MeV δ pulse in a bulk semiconductor is on the order of picoseconds and does not vary significantly with photon energy and material type. According to our analysis, the excess carrier generation time, excess carrier diffusion and recombination do not significantly influence the temporal resolution of this method. The temporal response of the refractive index change to a MeV pulse is also fast enough to meet the measurement requirements. The signal generation process for measuring a 10-ps MeV pulse with a 200-fs probe beam is analyzed, revealing that the transverse size of the MeV pulse does not influence the temporal resolution of this method.

High-Average-Power Diffraction Pulse-Compression Gratings Enabling Next-Generation Ultrafast Laser Systems

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

Alessi, D.

Pulse compressors for ultrafast lasers have been identified as a technology gap in the push towards high peak power systems with high average powers for industrial and scientific applications. Gratings for ultrashort (sub-150fs) pulse compressors are metallic and can absorb a significant percentage of laser energy resulting in up to 40% loss as well as thermal issues which degrade on-target performance. We have developed a next generation gold grating technology which we have scaled to the petawatt-size. This resulted in improvements in efficiency, uniformity and processing as compared to previous substrate etched gratings for high average power. This new designmore » has a deposited dielectric material for the grating ridge rather than etching directly into the glass substrate. It has been observed that average powers as low as 1W in a compressor can cause distortions in the on-target beam. We have developed and tested a method of actively cooling diffraction gratings which, in the case of gold gratings, can support a petawatt peak power laser with up to 600W average power. We demonstrated thermo-mechanical modeling of a grating in its use environment and benchmarked with experimental measurement. Multilayer dielectric (MLD) gratings are not yet used for these high peak power, ultrashort pulse durations due to their design challenges. We have designed and fabricated broad bandwidth, low dispersion MLD gratings suitable for delivering 30 fs pulses at high average power. This new grating design requires the use of a novel Out Of Plane (OOP) compressor, which we have modeled, designed, built and tested. This prototype compressor yielded a transmission of 90% for a pulse with 45 nm bandwidth, and free of spatial and angular chirp. In order to evaluate gratings and compressors built in this project we have commissioned a joule-class ultrafast Ti:Sapphire laser system. Combining the grating cooling and MLD technologies developed here could enable petawatt laser systems to operate at 50kW average power.« less

Engineering model for ultrafast laser microprocessing

NASA Astrophysics Data System (ADS)

Audouard, E.; Mottay, E.

2016-03-01

Ultrafast laser micro-machining relies on complex laser-matter interaction processes, leading to a virtually athermal laser ablation. The development of industrial ultrafast laser applications benefits from a better understanding of these processes. To this end, a number of sophisticated scientific models have been developed, providing valuable insights in the physics of the interaction. Yet, from an engineering point of view, they are often difficult to use, and require a number of adjustable parameters. We present a simple engineering model for ultrafast laser processing, applied in various real life applications: percussion drilling, line engraving, and non normal incidence trepanning. The model requires only two global parameters. Analytical results are derived for single pulse percussion drilling or simple pass engraving. Simple assumptions allow to predict the effect of non normal incident beams to obtain key parameters for trepanning drilling. The model is compared to experimental data on stainless steel with a wide range of laser characteristics (time duration, repetition rate, pulse energy) and machining conditions (sample or beam speed). Ablation depth and volume ablation rate are modeled for pulse durations from 100 fs to 1 ps. Trepanning time of 5.4 s with a conicity of 0.15° is obtained for a hole of 900 μm depth and 100 μm diameter.

Betatron x-ray radiation from laser-plasma accelerators driven by femtosecond and picosecond laser systems

NASA Astrophysics Data System (ADS)

Albert, F.; Lemos, N.; Shaw, J. L.; King, P. M.; Pollock, B. B.; Goyon, C.; Schumaker, W.; Saunders, A. M.; Marsh, K. A.; Pak, A.; Ralph, J. E.; Martins, J. L.; Amorim, L. D.; Falcone, R. W.; Glenzer, S. H.; Moody, J. D.; Joshi, C.

2018-05-01

A comparative experimental study of betatron x-ray radiation from laser wakefield acceleration in the blowout and self-modulated regimes is presented. Our experiments use picosecond duration laser pulses up to 150 J (self-modulated regime) and 60 fs duration laser pulses up to 10 J (blowout regime), for plasmas with electronic densities on the order of 1019 cm-3. In the self-modulated regime, where betatron radiation has been very little studied compared to the blowout regime, electrons accelerated in the wake of the laser pulse are subject to both the longitudinal plasma and transverse laser electrical fields. As a result, their motion within the wake is relatively complex; consequently, the experimental and theoretical properties of the x-ray source based on self-modulation differ from the blowout regime of laser wakefield acceleration. In our experimental configuration, electrons accelerated up to about 250 MeV and betatron x-ray spectra with critical energies of about 10-20 keV and photon fluxes between 108 and 1010 photons/eV Sr are reported. Our experiments open the prospect of using betatron x-ray radiation for applications, and the source is competitive with current x-ray backlighting methods on multi-kilojoule laser systems.

256 fs, 2 nJ soliton pulse generation from MoS2 mode-locked fiber laser

NASA Astrophysics Data System (ADS)

Jiang, Zike; Chen, Hao; Li, Jiarong; Yin, Jinde; Wang, Jinzhang; Yan, Peiguang

2017-12-01

We demonstrate an Er-doped fiber laser (EDFL) mode-locked by a MoS2 saturable absorber (SA), delivering a 256 fs, 2 nJ soliton pulse at 1563.4 nm. The nonlinear property of the SA prepared by magnetron sputtering deposition (MSD) is measured with a modulation depth (MD) of ∼19.48% and a saturable intensity of 4.14 MW/cm2. To the best of our knowledge, the generated soliton pulse has the highest pulse energy of 2 nJ among the reported mode-locked EDFLs based on transition metal dichalcogenides (TMDs). Our results indicate that MSD-grown SAs could offer an exciting platform for high pulse energy and ultrashort pulse generation.

Terahertz generation from laser-driven ultrafast current propagation along a wire target

NASA Astrophysics Data System (ADS)

Zhuo, H. B.; Zhang, S. J.; Li, X. H.; Zhou, H. Y.; Li, X. Z.; Zou, D. B.; Yu, M. Y.; Wu, H. C.; Sheng, Z. M.; Zhou, C. T.

2017-01-01

Generation of intense coherent THz radiation by obliquely incidenting an intense laser pulse on a wire target is studied using particle-in-cell simulation. The laser-accelerated fast electrons are confined and guided along the surface of the wire, which then acts like a current-carrying line antenna and under appropriate conditions can emit electromagnetic radiation in the THz regime. For a driving laser intensity ˜3 ×1018W /cm2 and pulse duration ˜10 fs, a transient current above 10 KA is produced on the wire surface. The emission-cone angle of the resulting ˜0.15 mJ (˜58 GV/m peak electric field) THz radiation is ˜30∘ . The conversion efficiency of laser-to-THz energy is ˜0.75 % . A simple analytical model that well reproduces the simulated result is presented.

Investigation Of Plasma Critical Surface Rippling By Harmonics Generation In Laser Plasmas

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

Racz, E.; Foeldes, I. B.; Szatmari, S.

2006-01-15

Experiments were carried out by a tightly focused, prepulse-free hybrid KrF excimer-dye laser system (700fs pulse duration, 248nm wavelength, 15mJ pulse energy). Intense 2{omega}, 3{omega} and near threshold 4{omega} were generated in laser plasmas on solid surfaces for p- and s-polarized 1.5{center_dot}1017 W/cm2 radiation intensity. Directionality and polarization properties were investigated depending on the laser intensity and polarization. The observations showed diffuse propagation of harmonics for intensities above 1016 W/cm2 and the polarization of harmonics was mixed for the highest intensities. The explanation of these results is surface rippling of the plasma critical surface because of the Rayleigh-Taylor instability, whichmore » is an intrinsic consequence of the unstable balance between light pressure and plasma expansion.« less

Dynamics of plasma expansion and shockwave formation in femtosecond laser-ablated aluminum plumes in argon gas at atmospheric pressures

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

Miloshevsky, Alexander; Harilal, Sivanandan S.; Miloshevsky, Gennady, E-mail: gennady@purdue.edu

2014-04-15

Plasma expansion with shockwave formation during laser ablation of materials in a background gasses is a complex process. The spatial and temporal evolution of pressure, temperature, density, and velocity fields is needed for its complete understanding. We have studied the expansion of femtosecond (fs) laser-ablated aluminum (Al) plumes in Argon (Ar) gas at 0.5 and 1 atmosphere (atm). The expansion of the plume is investigated experimentally using shadowgraphy and fast-gated imaging. The computational fluid dynamics (CFD) modeling is also carried out. The position of the shock front measured by shadowgraphy and fast-gated imaging is then compared to that obtained frommore » the CFD modeling. The results from the three methods are found to be in good agreement, especially during the initial stage of plasma expansion. The computed time- and space-resolved fields of gas-dynamic parameters have provided valuable insights into the dynamics of plasma expansion and shockwave formation in fs-pulse ablated Al plumes in Ar gas at 0.5 and 1 atm. These results are compared to our previous data on nanosecond (ns) laser ablation of Al [S. S. Harilal et al., Phys. Plasmas 19, 083504 (2012)]. It is observed that both fs and ns plumes acquire a nearly spherical shape at the end of expansion in Ar gas at 1 atm. However, due to significantly lower pulse energy of the fs laser (5 mJ) compared to pulse energy of the ns laser (100 mJ) used in our studies, the values of pressure, temperature, mass density, and velocity are found to be smaller in the fs laser plume, and their time evolution occurs much faster on the same time scale. The oscillatory shock waves clearly visible in the ns plume are not observed in the internal region of the fs plume. These experimental and computational results provide a quantitative understanding of plasma expansion and shockwave formation in fs-pulse and ns-pulse laser ablated Al plumes in an ambient gas at atmospheric pressures.« less

High power parallel ultrashort pulse laser processing

NASA Astrophysics Data System (ADS)

Gillner, Arnold; Gretzki, Patrick; Büsing, Lasse

2016-03-01

The class of ultra-short-pulse (USP) laser sources are used, whenever high precession and high quality material processing is demanded. These laser sources deliver pulse duration in the range of ps to fs and are characterized with high peak intensities leading to a direct vaporization of the material with a minimum thermal damage. With the availability of industrial laser source with an average power of up to 1000W, the main challenge consist of the effective energy distribution and disposition. Using lasers with high repetition rates in the MHz region can cause thermal issues like overheating, melt production and low ablation quality. In this paper, we will discuss different approaches for multibeam processing for utilization of high pulse energies. The combination of diffractive optics and conventional galvometer scanner can be used for high throughput laser ablation, but are limited in the optical qualities. We will show which applications can benefit from this hybrid optic and which improvements in productivity are expected. In addition, the optical limitations of the system will be compiled, in order to evaluate the suitability of this approach for any given application.

Direct analysis of intact biological macromolecules by low-energy, fiber-based femtosecond laser vaporization at 1042 nm wavelength with nanospray postionization mass spectrometry.

PubMed

Shi, Fengjian; Flanigan, Paul M; Archer, Jieutonne J; Levis, Robert J

2015-03-17

A fiber-based laser with a pulse duration of 435 fs and a wavelength of 1042 nm was used to vaporize biological macromolecules intact from the condensed phase into the gas phase for nanospray postionization and mass analysis. Laser vaporization of dried standard protein samples from a glass substrate by 10 Hz bursts of 20 pulses having 10 μs pulse separation and <50 μJ pulse energy resulted in signal comparable to a metal substrate. The protein signal observed from an aqueous droplet on a glass substrate was negligible compared to either a droplet on metal or a thin film on glass. The mass spectra generated from dried and aqueous protein samples by the low-energy, fiber laser were similar to the results from high-energy (500 μJ), 45-fs, 800-nm Ti:sapphire-based femtosecond laser electrospray mass spectrometry (LEMS) experiments, suggesting that the fiber-based femtosecond laser desorption mechanism involves a nonresonant, multiphoton process, rather than thermal- or photoacoustic-induced desorption. Direct analysis of whole blood performed without any pretreatment resulted in features corresponding to hemoglobin subunit-heme complex ions. The observation of intact molecular ions with low charge states from protein, and the tentatively assigned hemoglobin α subunit-heme complex from blood suggests that fiber-based femtosecond laser vaporization is a "soft" desorption source at a laser intensity of 2.39 × 10(12) W/cm(2). The low-energy, turnkey fiber laser demonstrates the potential of a more robust and affordable laser for femtosecond laser vaporization to deliver biological macromolecules into the gas phase for mass analysis.

Two-colour hard X-ray free-electron laser with wide tunability.

PubMed

Hara, Toru; Inubushi, Yuichi; Katayama, Tetsuo; Sato, Takahiro; Tanaka, Hitoshi; Tanaka, Takashi; Togashi, Tadashi; Togawa, Kazuaki; Tono, Kensuke; Yabashi, Makina; Ishikawa, Tetsuya

2013-01-01

Ultrabrilliant, femtosecond X-ray pulses from X-ray free-electron lasers (XFELs) have promoted the investigation of exotic interactions between intense X-rays and matters, and the observation of minute targets with high spatio-temporal resolution. Although a single X-ray beam has been utilized for these experiments, the use of multiple beams with flexible and optimum beam parameters should drastically enhance the capability and potentiality of XFELs. Here we show a new light source of a two-colour double-pulse (TCDP) XFEL in hard X-rays using variable-gap undulators, which realizes a large and flexible wavelength separation of more than 30% with an ultraprecisely controlled time interval in the attosecond regime. Together with sub-10-fs pulse duration and multi-gigawatt peak powers, the TCDP scheme enables us to elucidate X-ray-induced ultrafast transitions of electronic states and structures, which will significantly contribute to the advancement of ultrafast chemistry, plasma and astronomical physics, and quantum X-ray optics.

Next Generation Driver for Attosecond and Laser-plasma Physics.

PubMed

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

2017-07-12

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

Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering for gas-phase temperature measurements

NASA Astrophysics Data System (ADS)

Miller, Joseph Daniel

Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) is employed for quantitative gas-phase temperature measurements in combustion processes and heated flows. In this approach, ultrafast 100-fs laser pulses are used to induce vibrational and rotational transitions in N2 and O2, while a third spectrally narrowed picosecond pulse is used to probe the molecular response. Temporal suppression of the nonresonant contribution and elimination of collisional effects are achieved by delay of the probe pulse, while sufficient spectral resolution is maintained for frequency-domain detection and thermometry. A theoretical framework is developed to model experimental spectra by phenomenologically describing the temporal evolution of the vibrational and rotational wavepackets as a function of temperature and pressure. Interference-free, single-shot vibrational fs/ps CARS thermometry is demonstrated at 1-kHz from 1400-2400 K in a H2-air flame, with accuracy better than 3%. A time-asymmetric exponential pulse shape is introduced to optimize nonresonant suppression with a 103 reduction at a probe delay of 0.31 ps. Low-temperature single-shot thermometry (300-700 K) with better than 1.5% accuracy is demonstrated using a fully degenerate rotational fs/ps CARS scheme, and the influence of collision energy transfer on thermometry error is quantified at atmospheric pressure. Interference-free thermometry, without nonresonant contributions and collision-induced error, is demonstrated for the first time using rotational fs/ps CARS at room temperature and pressures from 1-15 atm. Finally, the temporal and spectral resolution of fs/ps CARS is exploited for transition-resolved time-domain measurements of N2 and O2 self-broadened S-branch Raman linewidths at pressures of 1-20 atm.

Characteristics of optical parametric oscillator synchronously pumped by Yb:KGW laser and based on periodically poled potassium titanyl phosphate crystal

NASA Astrophysics Data System (ADS)

Vengelis, Julius; Tumas, Adomas; Pipinytė, Ieva; Kuliešaitė, Miglė; Tamulienė, Viktorija; Jarutis, Vygandas; Grigonis, Rimantas; Sirutkaitis, Valdas

2018-03-01

We present experimental data and numerical simulation results obtained during investigation of synchronously pumped optical parametric oscillator (SPOPO) pumped by femtosecond Yb:KGW laser (central wavelength at 1033 nm). The nonlinear medium for parametric generation was periodically poled potassium titanyl phosphate crystal (PPKTP). Maximum parametric light conversion efficiency from pump power to signal power was more than 37.5% at λs=1530 nm wavelength, whereas the achieved signal wave continuous tuning range was from 1470 nm to 1970 nm with signal pulse durations ranging from 91 fs to roughly 280 fs. We demonstrated wavelength tuning by changing cavity length and PPKTP crystal grating period and also discussed net cavity group delay dispersion (GDD) influence on SPOPO output radiation characteristics. The achieved high pump to signal conversion efficiency and easy wavelength tuning make this device a very promising alternative to Ti:sapphire based SPOPOs as a source of continuously tunable femtosecond laser radiation in the near and mid-IR range.

Design of a 2 kA, 30 fs Rf-Photoinjector for Waterbag Compression

NASA Astrophysics Data System (ADS)

van der Geer, S. B.; Luiten, O. J.; de Loos, M. J.

Because uniformly filled ellipsoidal ‘waterbag’ bunches have linear self-fields in all dimensions, they do not suffer from space-charge induced brightness degradation. This in turn allows very efficient longitudinal compression of high-brightness bunches at sub or mildly relativistic energies, a parameter regime inaccessible up to now due to detrimental effects of non-linear space-charge forces. To demonstrate the feasibility of this approach, we investigate ballistic bunching of 1 MeV, 100 pC waterbag electron bunches, created in a half-cell rf-photogun, by means of a two-cell booster-compressor. Detailed GPT simulations of this table-top set-up are presented, including realistic fields, 3D space-charge effects, path-length differences and image charges at the cathode. It is shown that with a single 10MW S-band klystron and fields of 100 MV/m, 2kA peak current is attainable with a pulse duration of only 30 fs at a transverse normalized emittance of 1.5 μm.

Dynamics of electron injection in a laser-wakefield accelerator

NASA Astrophysics Data System (ADS)

Xu, J.; Buck, A.; Chou, S.-W.; Schmid, K.; Shen, B.; Tajima, T.; Kaluza, M. C.; Veisz, L.

2017-08-01

The detailed temporal evolution of the laser-wakefield acceleration process with controlled injection, producing reproducible high-quality electron bunches, has been investigated. The localized injection of electrons into the wakefield has been realized in a simple way—called shock-front injection—utilizing a sharp drop in plasma density. Both experimental and numerical results reveal the electron injection and acceleration process as well as the electron bunch's temporal properties. The possibility to visualize the plasma wave gives invaluable spatially resolved information about the local background electron density, which in turn allows for an efficient suppression of electron self-injection before the controlled process of injection at the sharp density jump. Upper limits for the electron bunch duration of 6.6 fs FWHM, or 2.8 fs (r.m.s.) were found. These results indicate that shock-front injection not only provides stable and tunable, but also few-femtosecond short electron pulses for applications such as ultrashort radiation sources, time-resolved electron diffraction or for the seeding of further acceleration stages.

Sub-picosecond streak camera measurements at LLNL: From IR to x-rays

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

Kuba, J; Shepherd, R; Booth, R

An ultra fast, sub-picosecond resolution streak camera has been recently developed at the LLNL. The camera is a versatile instrument with a wide operating wavelength range. The temporal resolution of up to 300 fs can be achieved, with routine operation at 500 fs. The streak camera has been operated in a wide wavelength range from IR to x-rays up to 2 keV. In this paper we briefly review the main design features that result in the unique properties of the streak camera and present its several scientific applications: (1) Streak camera characterization using a Michelson interferometer in visible range, (2)more » temporally resolved study of a transient x-ray laser at 14.7 nm, which enabled us to vary the x-ray laser pulse duration from {approx}2-6 ps by changing the pump laser parameters, and (3) an example of a time-resolved spectroscopy experiment with the streak camera.« less

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

PubMed Central

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

2016-01-01

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

Frequency comb based on a narrowband Yb-fiber oscillator: pre-chirp management for self-referenced carrier envelope offset frequency stabilization.

PubMed

Lim, Jinkang; Chen, Hung-Wen; Chang, Guoqing; Kärtner, Franz X

2013-02-25

Laser frequency combs are normally based on mode-locked oscillators emitting ultrashort pulses of ~100-fs or shorter. In this paper, we present a self-referenced frequency comb based on a narrowband (5-nm bandwidth corresponding to 415-fs transform-limited pulses) Yb-fiber oscillator with a repetition rate of 280 MHz. We employ a nonlinear Yb-fiber amplifier to both amplify the narrowband pulses and broaden their optical spectrum. To optimize the carrier envelope offset frequency (fCEO), we optimize the nonlinear pulse amplification by pre-chirping the pulses at the amplifier input. An optimum negative pre-chirp exists, which produces a signal-to-noise ratio of 35 dB (100 kHz resolution bandwidth) for the detected fCEO. We phase stabilize the fCEO using a feed-forward method, resulting in 0.64-rad (integrated from 1 Hz to 10 MHz) phase noise for the in-loop error signal. This work demonstrates the feasibility of implementing frequency combs from a narrowband oscillator, which is of particular importance for realizing large line-spacing frequency combs based on multi-GHz oscillators usually emitting long (>200 fs) pulses.

650-nJ pulses from a cavity-dumped Yb:fiber-pumped ultrafast optical parametric oscillator

NASA Astrophysics Data System (ADS)

Lamour, Tobias P.; Reid, Derryck T.

2011-08-01

Sub-250-fs pulses with energies of up to 650 nJ and peak powers up to 2.07 MW were generated from a cavity-dumped optical parametric oscillator, synchronously-pumped at 15.3 MHz with sub-400-fs pulses from an Yb:fiber laser. The average beam quality factor of the dumped output was M2 ~1.2 and the total relative-intensity noise was 8 mdBc, making the system a promising candidate for ultrafast laser inscription of infrared materials.

Inactivation of Viruses by Coherent Excitations with a Low Power Visible Femtosecond Laser

DTIC Science & Technology

2007-06-05

visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density...was greater than or equal to 50 MW/cm2. The inactivation of M13 phages was determined by plaque counts and had been found to depend on the pulse width...visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power

Ultrashort pulse laser ablation of dielectrics: Thresholds, mechanisms, role of breakdown

PubMed Central

Mirza, Inam; Bulgakova, Nadezhda M.; Tomáštík, Jan; Michálek, Václav; Haderka, Ondřej; Fekete, Ladislav; Mocek, Tomáš

2016-01-01

In this paper, we establish connections between the thresholds and mechanisms of the damage and white-light generation upon femtosecond laser irradiation of wide-bandgap transparent materials. On the example of Corning Willow glass, evolution of ablation craters, their quality, and white-light emission were studied experimentally for 130-fs, 800-nm laser pulses. The experimental results indicate co-existence of several ablation mechanisms which can be separated in time. Suppression of the phase explosion mechanism of ablation was revealed at the middle of the irradiation spots. At high laser fluences, air ionization was found to strongly influence ablation rate and quality and the main mechanisms of the influence are analysed. To gain insight into the processes triggered by laser radiation in glass, numerical simulations have been performed with accounting for the balance of laser energy absorption and its distribution/redistribution in the sample, including bremsstrahlung emission from excited free-electron plasma. The simulations have shown an insignificant role of avalanche ionization at such short durations of laser pulses while pointing to high average energy of electrons up to several dozens of eV. At multi-pulse ablation regimes, improvement of crater quality was found as compared to single/few pulses. PMID:27991543

Trends in laser micromachining

NASA Astrophysics Data System (ADS)

Gaebler, Frank; van Nunen, Joris; Held, Andrew

2016-03-01

Laser Micromachining is well established in industry. Depending on the application lasers with pulse length from μseconds to femtoseconds and wavelengths from 1064nm and its harmonics up to 5μm or 10.6μm are used. Ultrafast laser machining using pulses with pico or femtosecond duration pulses is gaining traction, as it offers very precise processing of materials with low thermal impact. Large-scale industrial ultrafast laser applications show that the market can be divided into various sub segments. One set of applications demand low power around 10W, compact footprint and are extremely sensitive to the laser price whilst still demanding 10ps or shorter laser pulses. A second set of applications are very power hungry and only become economically feasible for large scale deployments at power levels in the 100+W class. There is also a growing demand for applications requiring fs-laser pulses. In our presentation we would like to describe these sub segments by using selected applications from the automotive and electronics industry e.g. drilling of gas/diesel injection nozzles, dicing of LED substrates. We close the presentation with an outlook to micromachining applications e.g. glass cutting and foil processing with unique new CO lasers emitting 5μm laser wavelength.

Ultrashort pulse laser ablation of dielectrics: Thresholds, mechanisms, role of breakdown

NASA Astrophysics Data System (ADS)

Mirza, Inam; Bulgakova, Nadezhda M.; Tomáštík, Jan; Michálek, Václav; Haderka, Ondřej; Fekete, Ladislav; Mocek, Tomáš

2016-12-01

In this paper, we establish connections between the thresholds and mechanisms of the damage and white-light generation upon femtosecond laser irradiation of wide-bandgap transparent materials. On the example of Corning Willow glass, evolution of ablation craters, their quality, and white-light emission were studied experimentally for 130-fs, 800-nm laser pulses. The experimental results indicate co-existence of several ablation mechanisms which can be separated in time. Suppression of the phase explosion mechanism of ablation was revealed at the middle of the irradiation spots. At high laser fluences, air ionization was found to strongly influence ablation rate and quality and the main mechanisms of the influence are analysed. To gain insight into the processes triggered by laser radiation in glass, numerical simulations have been performed with accounting for the balance of laser energy absorption and its distribution/redistribution in the sample, including bremsstrahlung emission from excited free-electron plasma. The simulations have shown an insignificant role of avalanche ionization at such short durations of laser pulses while pointing to high average energy of electrons up to several dozens of eV. At multi-pulse ablation regimes, improvement of crater quality was found as compared to single/few pulses.

Ultrashort pulse laser ablation of dielectrics: Thresholds, mechanisms, role of breakdown.

PubMed

Mirza, Inam; Bulgakova, Nadezhda M; Tomáštík, Jan; Michálek, Václav; Haderka, Ondřej; Fekete, Ladislav; Mocek, Tomáš

2016-12-19

In this paper, we establish connections between the thresholds and mechanisms of the damage and white-light generation upon femtosecond laser irradiation of wide-bandgap transparent materials. On the example of Corning Willow glass, evolution of ablation craters, their quality, and white-light emission were studied experimentally for 130-fs, 800-nm laser pulses. The experimental results indicate co-existence of several ablation mechanisms which can be separated in time. Suppression of the phase explosion mechanism of ablation was revealed at the middle of the irradiation spots. At high laser fluences, air ionization was found to strongly influence ablation rate and quality and the main mechanisms of the influence are analysed. To gain insight into the processes triggered by laser radiation in glass, numerical simulations have been performed with accounting for the balance of laser energy absorption and its distribution/redistribution in the sample, including bremsstrahlung emission from excited free-electron plasma. The simulations have shown an insignificant role of avalanche ionization at such short durations of laser pulses while pointing to high average energy of electrons up to several dozens of eV. At multi-pulse ablation regimes, improvement of crater quality was found as compared to single/few pulses.

Ultrafast spectroscopy of coherent phonon in carbon nanotubes using sub-5-fs visible pulses

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

Kobayashi, Takayoshi; JST, CREST, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075 Japan; Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan

2016-02-01

In the last two decades, nano materials are attracting many scientists’ interest for both basic and application viewpoints. In order to understand the properties of nano systems it is needed to understand the dynamic properties which control the specific properties of the systems. All the primary processes in nano systems are taking place in femtosecond regime. Our group has been able to stably generate visible to near-infrared sub-5-fs laser pulses using a noncollinear optical parametric amplifier (NOPA) by the combination of various novel techniques including non-collinear optical parametric amplifier, pulse compression by a prism pair and grating pair. We applymore » the sub-5-fs pulses to study real-time coherent phonon in a one-dimensional system of carbon nanotubes. We determine exciton-phonon coupling mechanisms by observing the breathing mode in semiconducting carbon nanotubes and show the effect of electronic transition affected by the vibrational mode.« less

Breaking the Attosecond, Angstrom and TV/M Field Barriers with Ultra-Fast Electron Beams

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

Rosenzweig, James; Andonian, Gerard; Fukasawa, Atsushi

2012-06-22

Recent initiatives at UCLA concerning ultra-short, GeV electron beam generation have been aimed at achieving sub-fs pulses capable of driving X-ray free-electron lasers (FELs) in single-spike mode. This use of very low Q beams may allow existing FEL injectors to produce few-100 attosecond pulses, with very high brightness. Towards this end, recent experiments at the LCLS have produced {approx}2 fs, 20 pC electron pulses. We discuss here extensions of this work, in which we seek to exploit the beam brightness in FELs, in tandem with new developments in cryogenic undulator technology, to create compact accelerator-undulator systems that can lase belowmore » 0.15 {angstrom}, or be used to permit 1.5 {angstrom} operation at 4.5 GeV. In addition, we are now developing experiments which use the present LCLS fs pulses to excite plasma wakefields exceeding 1 TV/m, permitting a table-top TeV accelerator for frontier high energy physics applications.« less

Femtosecond laser-induced periodic surface structures on silicon upon polarization controlled two-color double-pulse irradiation.

PubMed

Höhm, Sandra; Herzlieb, Marcel; Rosenfeld, Arkadi; Krüger, Jörg; Bonse, Jörn

2015-01-12

Two-color double-fs-pulse experiments were performed on silicon wafers to study the temporally distributed energy deposition in the formation of laser-induced periodic surface structures (LIPSS). A Mach-Zehnder interferometer generated parallel or cross-polarized double-pulse sequences at 400 and 800 nm wavelength, with inter-pulse delays up to a few picoseconds between the sub-ablation 50-fs-pulses. Multiple two-color double-pulse sequences were collinearly focused by a spherical mirror to the sample. The resulting LIPSS characteristics (periods, areas) were analyzed by scanning electron microscopy. A wavelength-dependent plasmonic mechanism is proposed to explain the delay-dependence of the LIPSS. These two-color experiments extend previous single-color studies and prove the importance of the ultrafast energy deposition for LIPSS formation.

Energy-resolved coherent diffraction from laser-driven electronic motion in atoms

NASA Astrophysics Data System (ADS)

Shao, Hua-Chieh; Starace, Anthony F.

2017-10-01

We investigate theoretically the use of energy-resolved ultrafast electron diffraction to image laser-driven electronic motion in atoms. A chirped laser pulse is used to transfer the valence electron of the lithium atom from the ground state to the first excited state. During this process, the electronic motion is imaged by 100-fs and 1-fs electron pulses in energy-resolved diffraction measurements. Simulations show that the angle-resolved spectra reveal the time evolution of the energy content and symmetry of the electronic state. The time-dependent diffraction patterns are further interpreted in terms of the momentum transfer. For the case of incident 1-fs electron pulses, the rapid 2 s -2 p quantum beat motion of the target electron is imaged as a time-dependent asymmetric oscillation of the diffraction pattern.

Generation of Ultrashort Pulses from Chromium - Forsterite Laser

NASA Astrophysics Data System (ADS)

Seas, Antonios

This thesis discusses the generation of ultrashort pulses from the chromium-doped forsterite laser, the various designs, construction and operation of forsterite laser systems capable of generating picosecond and femtosecond pulses in the near infrared. Various mode-locking techniques including synchronous optical pumping, active mode-locking, and self-mode-locking were successfully engineered and implemented. Active and synchronously pumped mode-locking using a three mirror, astigmatically compensated cavity design and a forsterite crystal with a figure of merit of 26 (FOM = alpha_{rm 1064nm} /alpha_{rm 1250nm }) generated pulses with FWHM of 49 and 260 ps, respectively. The tuning range of the mode-locked forsterite laser in both cases was determined to be in the order of 100 nm limited only by the dielectric coatings of the mirrors used in the cavity. The slope efficiency was measured to be 12.5% for synchronous pumping and 9.1% for active mode-locking. A four mirror astigmatically compensated cavity was found to be more appropriate for mode-locking. Active mode-locking using the four-mirror cavity generated pulses with FWHM of 31 ps. The pulsewidth was further reduced to 6 ps by using a forsterite crystal with a higher figure of merit (FOM = 39). Pulsewidth-bandwidth measurements indicated the presence of chirp in the output pulses. Numerical calculation of the phase characteristics of various optical materials indicated that a pair of prisms made of SF 14 optical glass can be used in the cavity in order to compensate for the chirp. The insertion of the prisms in the cavity resulted in a reduction of the pulsewidth from 6 ps down to 900 fs. Careful optimization of the laser cavity resulted in the generation of stable 90-fs pulses. Pulses as short as 60 fs were generated and self-mode-locked mode of operation using the Cr:forsterite laser was demonstrated for the first time. Pure self-mode-locking was next achieved generating 105-fs pulses tunable between 1230-1270 nm. Numerical calculations of the cubic phase characteristics of the prism pair used indicated that the pair of SF 14 prisms compensated for quadratic phase but introduced a large cubic phase term. Numerical evaluation of other optical glasses indicated that a pair of SFN 64 prisms can introduce the same quadratic phase as SF 14 prisms but introduce a smaller cubic phase. When the SF 14 prisms were replaced by SFN 64 prisms the pulsewidth was reduced to 50 fs. Great improvement was also observed in the stability of the self-mode-locked forsterite laser and in the ease of achieving mode-locking. Using the same experimental arrangement and a forsterite crystal with improved FOM the pulse width was reduced to 36 fs.

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

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

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

2013-03-31

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

Industrial femtosecond lasers for machining of heat-sensitive polymers (Conference Presentation)

NASA Astrophysics Data System (ADS)

Hendricks, Frank; Bernard, Benjamin; Matylitsky, Victor V.

2017-03-01

Heat-sensitive materials, such as polymers, are used increasingly in various industrial sectors such as medical device manufacturing and organic electronics. Medical applications include implantable devices like stents, catheters and wires, which need to be structured and cut with minimum heat damage. Also the flat panel display market moves from LCD displays to organic LED (OLED) solutions, which utilize heat-sensitive polymer substrates. In both areas, the substrates often consist of multilayer stacks with different types of materials, such as metals, dielectric layers and polymers with different physical characteristic. The different thermal behavior and laser absorption properties of the materials used makes these stacks difficult to machine using conventional laser sources. Femtosecond lasers are an enabling technology for micromachining of these materials since it is possible to machine ultrafine structures with minimum thermal impact and very precise control over material removed. An industrial femtosecond Spirit HE laser system from Spectra-Physics with pulse duration <400 fs, pulse energies of >120 μJ and average output powers of >16 W is an ideal tool for industrial micromachining of a wide range of materials with highest quality and efficiency. The laser offers process flexibility with programmable pulse energy, repetition rate, and pulse width. In this paper, we provide an overview of machining heat-sensitive materials using Spirit HE laser. In particular, we show how the laser parameters (e.g. laser wavelength, pulse duration, applied energy and repetition rate) and the processing strategy (gas assisted single pass cut vs. multi-scan process) influence the efficiency and quality of laser processing.

Fast scintillation counter system and performance

NASA Technical Reports Server (NTRS)

Sasaki, H.; Nishioka, A.; Ohmori, N.; Kusumose, M.; Nakatsuka, T.; Horiki, T.; Hatano, Y.

1985-01-01

An experimental study of the fast scintillation counter (FS) system to observe a shower disk structure at Mt. Norikura is described, especially the system performance and a pulse wave-form by a single charge particles. The photomultiplier tube (PT) pulse appears at the leading edge of the main pulse. To remove this PT-pulse from the main pulse, the frame of the scintillator vessel was changed. The fast triggering system was made to decrease the dead time which came from the use of the function of the self triggering of the storage oscilloscope (OSC). To provide a new field on the multi-parameter study of the cosmic ray showers, the system response of the FS system also improved as a result of many considerations.

The analysis of photon pair source at telecom wavelength based on the BBO crystal (Conference Presentation)

NASA Astrophysics Data System (ADS)

Gajewski, Andrzej; Kolenderski, Piotr L.

2016-10-01

There are several problems that must be solved in order to increase the distance of quantum communication protocols based on photons as an information carriers. One of them is the dispersion, whose effects can be minimized by engineering spectral properties of transmitted photons. In particular, it is expected that positively correlated photon pairs can be very useful. We present the full characterization of a source of single photon pairs at a telecom wavelength based on type II spontaneous parametric down conversion (SPDC) process in a beta-barium borate (BBO) crystal. In the type II process, a pump photon, which is polarized extraordinarily, splits in a nonlinear medium into signal and idler photons, which are polarized perpendicularly to each other. In order for the process to be efficient a phase matching condition must be fulfilled. These conditions originate from momentum and energy conservation rules and put severe restrictions on source parameters. Seemingly, these conditions force the photon pair to be negatively correlated in their spectral domain. However, it is possible to achieve positive correlation for pulsed pumping. The experimentally available degrees of freedom of a source are the width of the pumping beam, the collected modes' widths, the length of the nonlinear crystal and the duration of the pumping pulse. In our numerical model we use the following figures of merit: the pair production rate, the efficiency of photon coupling into a single mode fiber, the spectral correlation of the coupled photon pair. The last one is defined as the Pearson correlation parameter for a joint spectral distribution. The aim here is to find the largest positive spectral correlation and the highest coupling efficiency. By resorting to the numerical model Ref. [1] we showed in Ref. [2], that by careful adjustment of the pump's and the collected modes' characteristics, one can optimize any of the source's parameters. Our numerical outcomes conform to the experimental results presented in Refs [3,4]. Here we investigate typical, experimentally available source parameters: the widths of the pump beam and collected modes ranging from 20μm to 500m, the crystal length ranging from 1mm to 7.5mm while the pulse duration is set to 50fs, 100fs or 150fs. We achieve the correlation coefficient value as high as approximately 0.8, or - for different values of parameters - coupling efficiency equal to 0.76.

High precision and high aspect ratio laser drilling: challenges and solutions

NASA Astrophysics Data System (ADS)

Uchtmann, Hermann; He, Chao; Gillner, Arnold

2016-03-01

Laser drilling is a very versatile tool to produce high accuracy bores in small and large geometries using different technologies. In large and deep hole drilling laser drilling can be found in drilling cooling holes into turbomachinery components such as turbine blades. In micro drilling, the technology is used for the generation of nozzles and filters. However, especially in macro drilling, the process often causes microstructure changes and induces defects such as recast layers and cracks. The defects are caused by the melt dominated drilling process by using pulse durations in the range of some 100 μm up to a few ms. A solution of this problem is the use of ultrashort pulsed laser radiation with pulse durations in the range of some 100 fs up to a few ps, however with the disadvantage of long drilling times. Thus, the aim of this work is to combine the productive process by using ms pulsed fiber laser radiation with subsequent ablation of existing recast layers at the hole wall by using ultrashort pulsed laser radiation. By using fast scanning techniques the recast layer can be avoided almost completely. With a similar technology also very small hole can be produced. Using a rotating dove prism a circular oscillation of the laser spots is performed and holes are drilled at intervals in 1 mm thick stainless steel (1.4301) by ultra-short laser pulses of 7 ps at 515 nm. The formation of hole and the behavior of energy deposition differ from other drilling strategies due to the helical revolution. The temporal evolution of the hole shape is analyzed by means of SEM techniques from which three drilling phases can be distinguished.

Ultrafast gigantic photo-response in charge-ordered organic salt (EDO-TTF)2PF6 on 10-fs time scales

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

Itatani, J.; Rini, M.; Cavalleri, A.

2008-08-01

The initial dynamics of photo-induced phase transition in charge-ordered organic salt (EDO-TTF){sub 2}PF{sub 6} was investigated using 10-fs near-infrared laser pulses. We observed sub-20-fs gigantic photo-responses (|{Delta}R/R|>100%) due to intra-molecular vibration and a clear signature of a structural bottleneck ({approx}50 fs) for the first time.

CW and femtosecond operation of a diode-pumped Yb:BaY(2)F(8) laser.

PubMed

Galzerano, G; Coluccelli, N; Gatti, D; Di Lieto, A; Tonelli, M; Laporta, P

2010-03-15

We report for the first time on laser action of a diode-pumped Yb:BaY(2)F(8) crystal. Both CW and femtosecond operations have been demonstrated at room-temperature conditions. A maximum output power of 0.56 W, a slope efficiency of 34%, and a tunability range from 1013 to 1067 nm have been obtained in CW regime. Transform-limited pulse trains with a minimum duration of 275 fs, an average power of 40 mW, and a repetition rate of 83 MHz have been achieved in a passive mode-locked regime using a semiconductor saturable absorber mirror.

Multi-Watt femtosecond optical parametric master oscillator power amplifier at 43 MHz.

PubMed

Mörz, Florian; Steinle, Tobias; Steinmann, Andy; Giessen, Harald

2015-09-07

We present a high repetition rate mid-infrared optical parametric master oscillator power amplifier (MOPA) scheme, which is tunable from 1370 to 4120nm. Up to 4.3W average output power are generated at 1370nm, corresponding to a photon conversion efficiency of 78%. Bandwidths of 6 to 12nm with pulse durations between 250 and 400fs have been measured. Strong conversion saturation over the whole signal range is observed, resulting in excellent power stability. The system consists of a fiber-feedback optical parametric oscillator that seeds an optical parametric power amplifier. Both systems are pumped by the same Yb:KGW femtosecond oscillator.

Femtosecond soliton source with fast and broad spectral tunability.

PubMed

Masip, Martin E; Rieznik, A A; König, Pablo G; Grosz, Diego F; Bragas, Andrea V; Martinez, Oscar E

2009-03-15

We present a complete set of measurements and numerical simulations of a femtosecond soliton source with fast and broad spectral tunability and nearly constant pulse width and average power. Solitons generated in a photonic crystal fiber, at the low-power coupling regime, can be tuned in a broad range of wavelengths, from 850 to 1200 nm using the input power as the control parameter. These solitons keep almost constant time duration (approximately 40 fs) and spectral widths (approximately 20 nm) over the entire measured spectra regardless of input power. Our numerical simulations agree well with measurements and predict a wide working wavelength range and robustness to input parameters.

High power Yb:CALGO ultrafast regenerative amplifier for industrial application

NASA Astrophysics Data System (ADS)

Caracciolo, E.; Guandalini, A.; Pirzio, F.; Kemnitzer, M.; Kienle, F.; Agnesi, A.; Aus der Au, J.

2017-02-01

We present a high-power, single-crystal based, Yb:CALGO regenerative amplifier. The system delivers more than 50 W output power in continuous-wave regime, with diffraction limited beam quality. In Q-switching regime the spectrum is centered at 1043 nm and is 11 nm wide. In regenerative amplification experiments we achieved 34 W at 500 kHz with 12.7 nm FWHM wide spectra centered at 1044 nm seeding with a broadly tunable, single-prism SESAM mode-locked Yb:CALGO laser providing 9 nm wide spectra at 1049 nm. Pulse duration after compression was 140 fs, with excellent beam quality (M2 < 1.25).

Toward compact and ultra-intense laser driven soft x-ray lasers (Conference Presentation)

NASA Astrophysics Data System (ADS)

Sebban, Stéphane

2017-05-01

We report here recent work on an optical-field ionized (OFI), high-order harmonic-seeded EUV laser. The amplifying medium is a plasma of nickel-like krypton obtained by optical field ionization focusing a 1 J, 30 fs, circularly- polarized, infrared pulse into a krypton-filled gas cell or krypton gas jet. The lasing transition is the 3d94p (J=0) --> 3d94p (J=1) transition of Ni-like krypton ions at 32.8 nm and is pumped by collisions with hot electrons. The polarization of the HH-seeded EUV laser beam was studied using an analyzer composed of three grazing incidence EUV multilayer mirrors able to spin under vacuum. For linear polarization, the Malus law has been recovered while in the case of a circularly-polarized seed, the EUV signal is insensitive to the rotation of the analyzer, bearing testimony to circularly polarized. The gain dynamics was probed by seeding the amplifier with a high-order harmonic pulse at different delays. The gain duration monotonically decreased from 7 ps to an unprecedented shortness of 450 fs FWHM as the amplification peak rose from 150 to 1,200 with an increase of the plasma density from 3 × 1018 cm-3 up to 1.2 × 1020 cm-3. The integrated energy of the EUV laser pulse was also measured, and found to be around 2 μJ. It is to be noted that in the ASE mode, longer amplifiers were achieved (up to 3 cm), yielding EUV outputs up to 14 μJ.

Hydrogen scrambling in ethane induced by intense laser fields: statistical analysis of coincidence events.

PubMed

Kanya, Reika; Kudou, Tatsuya; Schirmel, Nora; Miura, Shun; Weitzel, Karl-Michael; Hoshina, Kennosuke; Yamanouchi, Kaoru

2012-05-28

Two-body Coulomb explosion processes of ethane (CH(3)CH(3)) and its isotopomers (CD(3)CD(3) and CH(3)CD(3)) induced by an intense laser field (800 nm, 1.0 × 10(14) W/cm(2)) with three different pulse durations (40 fs, 80 fs, and 120 fs) are investigated by a coincidence momentum imaging method. On the basis of statistical treatment of the coincidence data, the contributions from false coincidence events are estimated and the relative yields of the decomposition pathways are determined with sufficiently small uncertainties. The branching ratios of the two body decomposition pathways of CH(3)CD(3) from which triatomic hydrogen molecular ions (H(3)(+), H(2)D(+), HD(2)(+), D(3)(+)) are ejected show that protons and deuterons within CH(3)CD(3) are scrambled almost statistically prior to the ejection of a triatomic hydrogen molecular ion. The branching ratios were estimated by statistical Rice-Ramsperger-Kassel-Marcus calculations by assuming a transition state with a hindered-rotation of a diatomic hydrogen moiety. The hydrogen scrambling dynamics followed by the two body decomposition processes are discussed also by using the anisotropies in the ejection directions of the fragment ions and the kinetic energy distribution of the two body decomposition pathways.

Laser induced periodic surface structuring on Si by temporal shaped femtosecond pulses.

PubMed

Almeida, G F B; Martins, R J; Otuka, A J G; Siqueira, J P; Mendonca, C R

2015-10-19

We investigated the effect of temporal shaped femtosecond pulses on silicon laser micromachining. By using sinusoidal spectral phases, pulse trains composed of sub-pulses with distinct temporal separations were generated and applied to the silicon surface to produce Laser Induced Periodic Surface Structures (LIPSS). The LIPSS obtained with different sub-pulse separation were analyzed by comparing the intensity of the two-dimensional fast Fourier Transform (2D-FFT) of the AFM images of the ripples (LIPSS). It was observed that LIPSS amplitude is more emphasized for the pulse train with sub-pulses separation of 128 fs, even when compared with the Fourier transform limited pulse. By estimating the carrier density achieved at the end of each pulse train, we have been able to interpret our results with the Sipe-Drude model, that predicts that LIPSS efficacy is higher for a specific induced carrier density. Hence, our results indicate that temporal shaping of the excitation pulse, performed by spectral phase modulation, can be explored in fs-laser microstructuring.

Polarization and Thickness Dependent Absorption Properties of Black Phosphorus: New Saturable Absorber for Ultrafast Pulse Generation

PubMed Central

Li, Diao; Jussila, Henri; Karvonen, Lasse; Ye, Guojun; Lipsanen, Harri; Chen, Xianhui; Sun, Zhipei

2015-01-01

Black phosphorus (BP) has recently been rediscovered as a new and interesting two-dimensional material due to its unique electronic and optical properties. Here, we study the linear and nonlinear optical properties of BP flakes. We observe that both the linear and nonlinear optical properties are anisotropic and can be tuned by the film thickness in BP, completely different from other typical two-dimensional layered materials (e.g., graphene and the most studied transition metal dichalcogenides). We then use the nonlinear optical properties of BP for ultrafast (pulse duration down to ~786 fs in mode-locking) and large-energy (pulse energy up to >18 nJ in Q-switching) pulse generation in fiber lasers at the near-infrared telecommunication band ~1.5 μm. We observe that the output of our BP based pulsed lasers is linearly polarized (with a degree-of-polarization ~98% in mode-locking, >99% in Q-switching, respectively) due to the anisotropic optical property of BP. Our results underscore the relatively large optical nonlinearity of BP with unique polarization and thickness dependence, and its potential for polarized optical pulse generation, paving the way to BP based nonlinear and ultrafast photonic applications (e.g., ultrafast all-optical polarization switches/modulators, frequency converters etc.). PMID:26514090

X-ray laser–induced electron dynamics observed by femtosecond diffraction from nanocrystals of Buckminsterfullerene

PubMed Central

Abbey, Brian; Dilanian, Ruben A.; Darmanin, Connie; Ryan, Rebecca A.; Putkunz, Corey T.; Martin, Andrew V.; Wood, David; Streltsov, Victor; Jones, Michael W. M.; Gaffney, Naylyn; Hofmann, Felix; Williams, Garth J.; Boutet, Sébastien; Messerschmidt, Marc; Seibert, M. Marvin; Williams, Sophie; Curwood, Evan; Balaur, Eugeniu; Peele, Andrew G.; Nugent, Keith A.; Quiney, Harry M.

2016-01-01

X-ray free-electron lasers (XFELs) deliver x-ray pulses with a coherent flux that is approximately eight orders of magnitude greater than that available from a modern third-generation synchrotron source. The power density of an XFEL pulse may be so high that it can modify the electronic properties of a sample on a femtosecond time scale. Exploration of the interaction of intense coherent x-ray pulses and matter is both of intrinsic scientific interest and of critical importance to the interpretation of experiments that probe the structures of materials using high-brightness femtosecond XFEL pulses. We report observations of the diffraction of extremely intense 32-fs nanofocused x-ray pulses by a powder sample of crystalline C60. We find that the diffraction pattern at the highest available incident power significantly differs from the one obtained using either third-generation synchrotron sources or XFEL sources operating at low output power and does not correspond to the diffraction pattern expected from any known phase of crystalline C60. We interpret these data as evidence of a long-range, coherent dynamic electronic distortion that is driven by the interaction of the periodic array of C60 molecular targets with intense x-ray pulses of femtosecond duration. PMID:27626076

Terahertz generation from laser-driven ultrafast current propagation along a wire target.

PubMed

Zhuo, H B; Zhang, S J; Li, X H; Zhou, H Y; Li, X Z; Zou, D B; Yu, M Y; Wu, H C; Sheng, Z M; Zhou, C T

2017-01-01

Generation of intense coherent THz radiation by obliquely incidenting an intense laser pulse on a wire target is studied using particle-in-cell simulation. The laser-accelerated fast electrons are confined and guided along the surface of the wire, which then acts like a current-carrying line antenna and under appropriate conditions can emit electromagnetic radiation in the THz regime. For a driving laser intensity ∼3×10^{18}W/cm^{2} and pulse duration ∼10 fs, a transient current above 10 KA is produced on the wire surface. The emission-cone angle of the resulting ∼0.15 mJ (∼58 GV/m peak electric field) THz radiation is ∼30^{∘}. The conversion efficiency of laser-to-THz energy is ∼0.75%. A simple analytical model that well reproduces the simulated result is presented.

Comparative studies of efficiency droop in polar and non-polar InGaN quantum wells

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

Davies, M. J.; Dawson, P.; Hammersley, S.

We report on a comparative study of efficiency droop in polar and non-polar InGaN quantum well structures at T = 10 K. To ensure that the experiments were carried out with identical carrier densities for any particular excitation power density, we used laser pulses of duration ∼100 fs at a repetition rate of 400 kHz. For both types of structures, efficiency droop was observed to occur for carrier densities of above 7 × 10{sup 11 }cm{sup −2 }pulse{sup −1} per quantum well; also both structures exhibited similar spectral broadening in the droop regime. These results show that efficiency droop is intrinsic in InGaN quantum wells, whether polar or non-polar,more » and is a function, specifically, of carrier density.« less

High intensity surface plasma waves, theory and PIC simulations

NASA Astrophysics Data System (ADS)

Raynaud, M.; Héron, A.; Adam, J.-C.

2018-01-01

With the development of intense (>1019 W cm-2) short pulses (≤25 fs) laser with very high contrast, surface plasma wave (SPW) can be explored in the relativistic regime. As the SPW propagates with a phase velocity close to the speed of light it may results in a strong acceleration of electron bunches along the surface permitting them to reach relativistic energies. This may be important e.g. for applications in the field of plasma-based accelerators. We investigate in this work the excitation of SPWs on grating preformed over-dense plasmas for laser intensities ranging from 1019 up to 1021 W cm-2. We discuss the nature of the interaction with respect to the solid case in which surface plasmon can be resonantly excited with weak laser intensity. In particular, we show the importance of the pulse duration and focalization of the laser beam on the amplitude of the SPW.

Using femtosecond laser to fabricate highly precise interior three-dimensional microstructures in polymeric flow chip

PubMed Central

Lee, Chia-Yu; Chang, Ting-Chou; Wang, Shau-Chun; Chien, Chih-Wei; Cheng, Chung-Wei

2010-01-01

This paper reports using femtosecond laser marker to fabricate the three-dimensional interior microstructures in one closed flow channel of plastic substrate. Strip-like slots in the dimensions of 800 μm×400 μm×65 μm were ablated with pulse Ti:sapphire laser at 800 nm (pulse duration of ∼120 fs with 1 kHz repetition rate) on acrylic slide. After ablation, defocused beams were used to finish the surface of microstructures. Having finally polished with sonication, the laser fabricated structures are highly precise with the arithmetic roughness of 1.5 and 4.5 nm. Fabricating such highly precise microstructures cannot be accomplished with nanosecond laser marking or other mechanical drilling methods. In addition, since laser ablation can directly engrave interior microstructures in one closed chip, glue smearing problems to damage molded microstructures possibly to occur during the chip sealing procedures can be avoided too. PMID:21079695

Using femtosecond laser to fabricate highly precise interior three-dimensional microstructures in polymeric flow chip.

PubMed

Lee, Chia-Yu; Chang, Ting-Chou; Wang, Shau-Chun; Chien, Chih-Wei; Cheng, Chung-Wei

2010-10-18

This paper reports using femtosecond laser marker to fabricate the three-dimensional interior microstructures in one closed flow channel of plastic substrate. Strip-like slots in the dimensions of 800 μm×400 μm×65 μm were ablated with pulse Ti:sapphire laser at 800 nm (pulse duration of ∼120 fs with 1 kHz repetition rate) on acrylic slide. After ablation, defocused beams were used to finish the surface of microstructures. Having finally polished with sonication, the laser fabricated structures are highly precise with the arithmetic roughness of 1.5 and 4.5 nm. Fabricating such highly precise microstructures cannot be accomplished with nanosecond laser marking or other mechanical drilling methods. In addition, since laser ablation can directly engrave interior microstructures in one closed chip, glue smearing problems to damage molded microstructures possibly to occur during the chip sealing procedures can be avoided too.

A stabilized optical frequency comb based on an Er-doped fiber femtosecond laser

NASA Astrophysics Data System (ADS)

Xia, Chuanqing; Wu, Tengfei; Zhao, Chunbo; Xing, Shuai

2018-03-01

An optical frequency comb based on a 250 MHz home-made Er-doped fiber femtosecond laser is presented in this paper. The Er-doped fiber laser has a ring cavity and operates mode-locked in femtosecond regime with the technique of nonlinear polarization rotation. The pulse duration is 118 fs and the spectral width is 30 nm. A part of the femtosecond laser is amplified in Er-doped fiber amplifier before propagating through a piece of highly nonlinear fiber for expanding the spectrum. The carrier-envelope offset frequency of the comb which has a signal-to-noise ratio more than 35 dB is extracted by means of f-2f beating. It demonstrates that both carrier-envelope offset frequency and repetition frequency keep phase locked to a Rubidium atomic clock simultaneously for 2 hours. The frequency stabilized fiber combs will be increasingly applied in optical metrology, attosecond pulse generation, and absolute distance measurement.

Surface treatment of CFRP composites using femtosecond laser radiation

NASA Astrophysics Data System (ADS)

Oliveira, V.; Sharma, S. P.; de Moura, M. F. S. F.; Moreira, R. D. F.; Vilar, R.

2017-07-01

In the present work, we investigate the surface treatment of carbon fiber-reinforced polymer (CFRP) composites by laser ablation with femtosecond laser radiation. For this purpose, unidirectional carbon fiber-reinforced epoxy matrix composites were treated with femtosecond laser pulses of 1024 nm wavelength and 550 fs duration. Laser tracks were inscribed on the material surface using pulse energies and scanning speeds in the range 0.1-0.5 mJ and 0.1-5 mm/s, respectively. The morphology of the laser treated surfaces was investigated by field emission scanning electron microscopy. We show that, by using the appropriate processing parameters, a selective removal of the epoxy resin can be achieved, leaving the carbon fibers exposed. In addition, sub-micron laser induced periodic surface structures (LIPSS) are created on the carbon fibers surface, which may be potentially beneficial for the improvement of the fiber to matrix adhesion in adhesive bonds between CFRP parts.

Ultrashort pulse generation in mode-locked erbium-doped fiber lasers with tungsten disulfide saturable absorber

NASA Astrophysics Data System (ADS)

Liu, Mengli; Liu, Wenjun; Pang, Lihui; Teng, Hao; Fang, Shaobo; Wei, Zhiyi

2018-01-01

Tungsten disulfide (WS2), as one of typical transition metal dichalcogenides with the characteristics of strong nonlinear polarization and wide bandgap, has been widely used in such fields as biology and optoelectronics. With the magnetron sputtering technique, the saturable absorber (SA) is prepared by depositing WS2 and Au film on the tapered fiber. The heat elimination and damage threshold can be improved for the WS2 SA with evanescent field interaction. Besides, the Au film is deposited on the surface of the WS2 film to improve their reliability and avoid being oxidized. The fabricated SA has a modulation depth of 14.79%. With this SA, we obtain a relatively stable mode-locked fiber laser with the pulse duration of 288 fs, the repetition rate of 41.4 MHz and the signal to noise ratio of 58 dB.

PAL-XFEL soft X-ray scientific instruments and X-ray optics: First commissioning results

NASA Astrophysics Data System (ADS)

Park, Sang Han; Kim, Minseok; Min, Changi-Ki; Eom, Intae; Nam, Inhyuk; Lee, Heung-Soo; Kang, Heung-Sik; Kim, Hyeong-Do; Jang, Ho Young; Kim, Seonghan; Hwang, Sun-min; Park, Gi-Soo; Park, Jaehun; Koo, Tae-Yeong; Kwon, Soonnam

2018-05-01

We report an overview of soft X-ray scientific instruments and X-ray optics at the free electron laser (FEL) of the Pohang Accelerator Laboratory, with selected first-commissioning results. The FEL exhibited a pulse energy of 200 μJ/pulse, a pulse width of <50 fs full width at half maximum, and an energy bandwidth of 0.44% at a photon energy of 850 eV. Monochromator resolving power of 10 500 was achieved. The estimated total time resolution between optical laser and X-ray pulses was <270 fs. A resonant inelastic X-ray scattering spectrometer was set up; its commissioning results are also reported.

Direct generation of 128-fs Gaussian pulses from a compensation-free fiber laser using dual mode-locking mechanisms

NASA Astrophysics Data System (ADS)

Peng, Junsong; Zhan, Li; Gu, Zhaochang; Qian, Kai; Luo, Shouyu; Shen, Qishun

2012-03-01

We have experimentally demonstrated the direct generation of 128-fs pulses in an all-anomalous-dispersion all-fiber mode-locked laser. The laser is free of dispersion compensation in the cavity based on standard single mode fiber (SMF). The time-bandwidth product is 0.536. The laser is achieved by using two mode-lockers, one is nonlinear polarization rotation (NPR), and the other is nonlinear amplifying loop mirror. The coexistence of dual mode-locking mechanisms can decrease the cavity length to 12-m, and also results in producing high-quality pulses with a Gaussian shape both on the pulse profile and spectrum, but without Kelly sidebands.

Pre-chirp managed nonlinear amplification in fibers delivering 100  W, 60  fs pulses.

PubMed

Liu, Wei; Schimpf, Damian N; Eidam, Tino; Limpert, Jens; Tünnermann, Andreas; Kärtner, Franz X; Chang, Guoqing

2015-01-15

We demonstrate a pre-chirp managed Yb-doped fiber laser system that outputs 75 MHz, 130 W spectrally broadened pulses, which are compressed by a diffraction-grating pair to 60 fs with average powers as high as 100 W. Fine tuning the pulse chirp prior to amplification leads to high-quality compressed pulses. Detailed experiments and numerical simulation reveal that the optimum pre-chirp group-delay dispersion increases from negative to positive with increasing output power for rod-type high-power fiber amplifiers. The resulting laser parameters are suitable for extreme nonlinear optics applications such as frequency conversion in femtosecond enhancement cavities.

Measurement of ultrashort laser pulses using single-crystal films of 4-aminobenzophenone

NASA Astrophysics Data System (ADS)

Bhowmik, Achintya K.; Tan, Shida; Ahyi, Ayayi C.; Dharmadhikari, J. A.; Dharmadhikari, A. K.; Mathur, D.

2007-12-01

Single-crystal thin-film of an organic second-order nonlinear optical material, 4-aminobenzophenone (ABP), is used to measure the pulsewidth of a Ti-Sapphire laser producing ˜45 fs pulses at 1 kHz repetition rate, by the non-collinear second-harmonic generation (SHG) intensity autocorrelation technique. These films are suitable for measurements over a broad wavelength range, down to 780 nm, due to their wide optical transparency. The single-crystal film with thickness (˜3 μm) less than the coherence length requires no phase-matching for efficient broadband SHG. Pulse walk-off due to group-velocity mismatch (GVM) and temporal broadening of the pulses due to group-velocity dispersion (GVD) are found to be negligible. These effects have been estimated for pulse width down to few-cycle pulses (˜10 fs), and the analyses show that these films can be used to characterize such ultrashort optical pulses.

The Physics of Ultrabroadband Frequency Comb Generation and Optimized Combs for Measurements in Fundamental Physics

DTIC Science & Technology

2016-07-02

beams Superresolution machining Threshold effect of ablation means that structure diameter is less than the beam diameter fs pulses at 800 nm yield 200...Approved for public release: distribution unlimited. Applications of Bessel beams Superresolution machining Threshold effect of ablation means that... Superresolution machining Threshold effect of ablation means that structure diameter is less than the beam diameter fs pulses at 800 nm yield 200 nm

Self-mode-locked chromium-doped forsterite laser generates 50-fs pulses

NASA Technical Reports Server (NTRS)

Seas, A.; Petricevic, V.; Alfano, R. R.

1993-01-01

Stable transform-limited (delta nu-delta tau = 0.32) femtosecond pulses with a FWHM of 50 fs were generated from a self-mode-locked chromium-doped forsterite laser. The forsterite laser was synchronously pumped by a CW mode-locked Nd:YAG (82 MHz) laser that generated picosecond pulses (200-300 ps) and provided the starting mechanism for self-mode-locked operation. Maximum output power was 45 mW for 3.9 W of absorbed pumped power with the use of an output coupler with 1 percent transmission. The self-mode-locked forsterite laser was tuned from 1240 to 1270 nm.

Tetravalent chromium (Cr(4+)) as laser-active ion for tunable solid-state lasers

NASA Technical Reports Server (NTRS)

Seas, A.; Petricevic, V.; Alfano, Robert R.

1992-01-01

Generation of femtosecond pulses from a continuous-wave mode-locked chromium-doped forsterite (Cr(4+):Mg2SiO4) laser has been accomplished. The forsterite laser was actively mode-locked using an acousto-optic modulator operating at 78 MHz with two Brewster high-dispersion glass prisms for intra-cavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(sub 00) mode with 85 mW of continuous power (with 1 percent output coupler), tunable over 1230-1280 nm. The shortest pulses of 60-fs pulsewidth were measured.

65-fs Yb-doped all-fiber laser using tapered fiber for nonlinearity and dispersion management.

PubMed

Yang, Peilong; Teng, Hao; Fang, Shaobo; Hu, Zhongqi; Chang, Guoqing; Wang, Junli; Wei, Zhiyi

2018-04-15

We implement an ultrafast Yb-doped all-fiber laser which incorporates tapered single-mode fibers for managing nonlinearity and dispersion. The tapered fiber placed in the oscillator cavity aims to broaden the optical spectrum of the intracavity pulse. At the oscillator output, we use another tapered fiber to perform pulse compression. The resulting 66.1-MHz Yb-doped all-fiber oscillator self-starts and generates 0.4-nJ, 65-fs pulses, which can serve as a compact and robust seed source for subsequent high-power, high-energy amplifiers.

All-fiber high-power monolithic femtosecond laser at 1.59 µm with 63-fs pulse width

NASA Astrophysics Data System (ADS)

Hekmat, M. J.; Omoomi, M.; Gholami, A.; Yazdabadi, A. Bagheri; Abdollahi, M.; Hamidnejad, E.; Ebrahimi, A.; Normohamadi, H.

2018-01-01

In this research, by adopting an alternative novel approach to ultra-short giant pulse generation which basically originated from difficulties with traditional employed methods, an optimized Er/Yb co-doped double-clad fiber amplifier is applied to boost output average power of single-mode output pulses to a high level of 2-W at 1.59-µm central wavelength. Output pulses of approximately 63-fs pulse width at 52-MHz repetition rate are obtained in an all-fiber monolithic laser configuration. The idea of employing parabolic pulse amplification for stretching output pulses together with high-power pulse amplification using Er/Yb co-doped active fibers for compressing and boosting output average power plays crucial role in obtaining desired results. The proposed configuration enjoys massive advantages over previously reported literature which make it well-suited for high-power precision applications such as medical surgery. Detailed dynamics of pulse stretching and compressing in active fibers with different GVD parameters are numerically and experimentally investigated.

Prospects of Using High-Intensity THz Pulses To Induce Ultrafast Temperature-Jumps in Liquid Water.

PubMed

Mishra, Pankaj Kr; Bettaque, Vincent; Vendrell, Oriol; Santra, Robin; Welsch, Ralph

2018-06-01

Ultrashort, high-intensity terahertz (THz) pulses, e.g., generated at free-electron laser facilities, allow for direct investigation as well as the driving of intermolecular modes in liquids like water and thus will deepen our understanding of the hydrogen bonding network. In this work, the temperature-jump (T-jump) of water induced by THz radiation is simulated for ten different THz frequencies in the range from 3 to 30 THz and five different pulse intensities in the range from 1 × 10 11 to 5 × 10 12 W/cm 2 employing both ab initio molecular dynamics (AIMD) and force field molecular dynamics (FFMD) approaches. The most efficient T-jump can be achieved with 16 THz pulses. Three distinct T-jump mechanisms can be uncovered. For all cases, the T-jump mechanism proceeds within tens of femtoseconds (fs). For frequencies between 10 and 25 THz, most of the energy is initially transferred to the rotational degrees of freedom. Subsequently, the energy is redistributed to the translational and intramolecular vibrational degrees of freedom within a maximum of 500 fs. For the lowest frequencies considered (7 THz and below), translational and rotational degrees of freedom are heated within tens of fs as the THz pulse also couples to the intermolecular vibrations. Subsequently, the intramolecular vibrational modes are heated within a few hundred fs. At the highest frequencies considered (25 THz and above), vibrational and rotational degrees of freedom are heated within tens of fs, and energy redistribution to the translational degrees of freedom happens within several hundred fs. Both AIMD and FFMD simulations show a similar dependence of the T-jump on the frequency employed. However, the FFMD simulations overestimate the total energy transfer around the main peak and drop off too fast toward frequencies higher and lower than the main peak. These differences can be rationalized by missing elements, such as the polarizability, in the TIP4P/2005f force field employed. The feasibility of performing experiments at the studied frequencies and intensities as well as important issues such as energy efficiency, penetration depth, and focusing are discussed.

Microstructure formation on liquid metal surface under pulsed action

NASA Astrophysics Data System (ADS)

Genin, D. E.; Beloplotov, D. V.; Panchenko, A. N.; Tarasenko, V. F.

2018-04-01

Experimental study and theoretical analysis of growth of microstructures (microtowers) on liquid metals by fs laser pulses have been carried out. Theoretical analysis has been performed on the basis of the two-temperature model. Compared to ns laser pulses, in fs irradiation regimes the heat-affected zone is strongly localized resulting in much larger temperatures and temperature gradients. In the experimental irradiation regimes, the surface temperature of liquid metals studied may reach or even exceed a critical level that culminates in phase explosion or direct atomization of a metal surface layer. However, before explosive ablation starts, a stress wave with an amplitude up to several GPa is formed which demolishes oxide covering. Moreover, at high laser fluences laser-induced breakdown is developed in oxide layer covering the metal surface that leads to destruction/ablation of oxide without damaging metal underneath. An overall scenario of microstructure growth with fs laser pulses is similar to that obtained for ns irradiation regimes though the growth threshold is lower due to smaller heat-conduction losses. Also we managed to obtain microstructures formation by the action of spark discharge.

Pulsewidth-dependent nature of laser-induced DNA damage in RPE cells

NASA Astrophysics Data System (ADS)

Hall, Rebecca M.; Glickman, Randolph D.; Rockwell, Benjamin A.; Kumar, Neeru; Noojin, Gary D.

2001-07-01

Ultrashort pulse laser radiation may produce cellular damage through unique mechanisms. Primary cultures of bovine retinal pigment epithelial (RPE) cells were exposed to the out put of a Ti:Sapphire laser producing 30 fs (mode-locked) pulses, 44 amplified fs pulses, or continuous wave exposures at 800 nm. Laser exposures at and below the damage threshold were studied. DNA damage was detected using single cell gel electrophoresis (comet assay). Unexposed (control) cells produced short tails with low tail moments. In contrast, all laser-exposed cells showed some degree of DNA fragmentation, but the size and shape of the resulting comets differed among the various modalities. CW-exposed cells produced generally light and relatively compact tails, suggesting fewer and larger DNA fragments, while mode-locked laser exposures (30 fs pulses) resulted in large and diffuse comets, indicating the DNA was fragmented into many very small pieces. Work is continuing to define the relationship of laser pulsewidth and intensity with the degree of DNA fragmentation. These results suggest that DNA damage may result from multiple mechanisms of laser-cell interaction, including multiphoton absorption.

Anisotropy modulations of femtosecond laser pulse induced periodic surface structures on silicon by adjusting double pulse delay.

PubMed

Han, Weina; Jiang, Lan; Li, Xiaowei; Wang, Qingsong; Li, Hao; Lu, YongFeng

2014-06-30

We demonstrate that the polarization-dependent anisotropy of the laser-induced periodic surface structure (LIPSS) on silicon can be adjusted by designing a femtosecond laser pulse train (800 nm, 50 fs, 1 kHz). By varying the pulse delay from 100 to 1600 fs within a double pulse train to reduce the deposited pulse energy, which weakens the directional surface plasmon polarition (SPP)-laser energy coupling based on the initial formed ripple structure, the polarization-dependent geometrical morphology of the LIPSS evolves from a nearly isotropic circular shape to a somewhat elongated elliptical shape. Meanwhile, the controllable anisotropy of the two-dimensional scanned-line widths with different directions is achieved based on a certain pulse delay combined with the scanning speed. This can effectively realize better control over large-area uniform LIPSS formation. As an example, we further show that the large-area LIPSS can be formed with different scanning times under different pulse delays.

Strong electromagnetic pulses generated in laser-matter interactions with 10TW-class fs laser

NASA Astrophysics Data System (ADS)

Rączka, Piotr; Rosiński, Marcin; Zaraś-Szydłowska, Agnieszka; Wołowski, Jerzy; Badziak, Jan

2018-01-01

The results of an experiment on the generation of electromagnetic pulses (EMP) in the interaction of 10TW fs pulses with thick (mm scale) and thin foil (μm scale) targets are described. Such pulses, with frequencies in the GHz range, may pose a threat to safe and reliable operation of high-power, high-intensity laser facilities. The main point of the experiment is to investigate the fine temporal structure of such pulses using an oscilloscope capable of measurements at very high sampling rate. It is found that the amazing reproducibility of such pulses is confirmed at this high sampling rate. Furthermore, the differences between the EMP signals generated from thick and thin foil targets are clearly seen, which indicates that besides electric polarization of the target and the target neutralization current there may be other factors essential for the EMP emission.

Ultrashort laser pulse driven inverse free electron laser accelerator experiment

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

Moody, J. T.; Anderson, S. G.; Anderson, G.

In this paper we discuss the ultrashort pulse high gradient Inverse Free Electron laser accelerator experiment carried out at the Lawrence Livermore National Laboratory which demonstrated gra- dients exceeding 200 MV/m using a 4 TW 100 fs long 800 nm Ti:Sa laser pulse. Due to the short laser and electron pulse lengths, synchronization was determined to be one of the main challenges in this experiment. This made necessary the implementation of a single-shot, non destructive, electro-optic sampling based diagnostics to enable time-stamping of each laser accelerator shot with < 100 fs accuracy. The results of this experiment are expected tomore » pave the way towards the development of future GeV-class IFEL accelerators.« less

Ultrashort laser pulse driven inverse free electron laser accelerator experiment

DOE PAGES

Moody, J. T.; Anderson, S. G.; Anderson, G.; ...

2016-02-29

In this paper we discuss the ultrashort pulse high gradient Inverse Free Electron laser accelerator experiment carried out at the Lawrence Livermore National Laboratory which demonstrated gra- dients exceeding 200 MV/m using a 4 TW 100 fs long 800 nm Ti:Sa laser pulse. Due to the short laser and electron pulse lengths, synchronization was determined to be one of the main challenges in this experiment. This made necessary the implementation of a single-shot, non destructive, electro-optic sampling based diagnostics to enable time-stamping of each laser accelerator shot with < 100 fs accuracy. The results of this experiment are expected tomore » pave the way towards the development of future GeV-class IFEL accelerators.« less

Air-guided photonic-crystal-fiber pulse-compression delivery of multimegawatt femtosecond laser output for nonlinear-optical imaging and neurosurgery

NASA Astrophysics Data System (ADS)

Lanin, Aleksandr A.; Fedotov, Il'ya V.; Sidorov-Biryukov, Dmitrii A.; Doronina-Amitonova, Lyubov V.; Ivashkina, Olga I.; Zots, Marina A.; Sun, Chi-Kuang; Ömer Ilday, F.; Fedotov, Andrei B.; Anokhin, Konstantin V.; Zheltikov, Aleksei M.

2012-03-01

Large-core hollow photonic-crystal fibers (PCFs) are shown to enable a fiber-format air-guided delivery of ultrashort infrared laser pulses for neurosurgery and nonlinear-optical imaging. With an appropriate dispersion precompensation, an anomalously dispersive 15-μm-core hollow PCF compresses 510-fs, 1070-nm light pulses to a pulse width of about 110 fs, providing a peak power in excess of 5 MW. The compressed PCF output is employed to induce a local photodisruption of corpus callosum tissues in mouse brain and is used to generate the third harmonic in brain tissues, which is captured by the PCF and delivered to a detector through the PCF cladding.

Laser ablation mechanism of transparent layers on semiconductors with ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Rublack, Tino; Hartnauer, Stefan; Mergner, Michael; Muchow, Markus; Seifert, Gerhard

2011-12-01

Transparent dielectric layers on semiconductors are used as anti-reflection coatings both for photovoltaic applications and for mid-infrared optical elements. We have shown recently that selective ablation of such layers is possible using ultrashort laser pulses at wavelengths being absorbed by the semiconductor. To get a deeper understanding of the ablation mechanism, we have done ablation experiments for different transparent materials, in particular SiO2 and SixNy on silicon, using a broad range of wavelengths ranging from UV to IR, and pulse durations between 50 and 2000 fs. The characterization of the ablated regions was done by light microscopy and atomic force microscopy (AFM). Utilizing laser wavelengths above the silicon band gap, selective ablation of the dielectric layer without noticeable damage of the opened silicon surface is possible. In contrast, ultrashort pulses (1-2 ps) at mid-infrared wavelengths already cause damage in the silicon at lower intensities than in the dielectric layer, even when a vibrational resonance (e.g. at λ = 9.26 μm for SiO2) is addressed. The physical processes behind this, on the first glance counterintuitive, observation will be discussed.

Laser micro-machining strategies for transparent brittle materials using ultrashort pulsed lasers

NASA Astrophysics Data System (ADS)

Bernard, Benjamin; Matylitsky, Victor

2017-02-01

Cutting and drilling of transparent materials using short pulsed laser systems are important industrial production processes. Applications ranging from sapphire cutting, hardened glass processing, and flat panel display cutting, to diamond processing are possible. The ablation process using a Gaussian laser beam incident on the topside of a sample with several parallel overlapping lines leads to a V-shaped structured groove. This limits the structuring depth for a given kerf width. The unique possibility for transparent materials to start the ablation process from the backside of the sample is a well-known strategy to improve the aspect ratio of the ablated features. This work compares the achievable groove depth depending on the kerf width for front-side and back-side ablation and presents the best relation between the kerf width and number of overscans. Additionally, the influence of the number of pulses in one burst train on the ablation efficiency is investigated. The experiments were carried out using Spirit HE laser from Spectra-Physics, with the features of adjustable pulse duration from <400 fs to 10 ps, three different repetition rates (100 kHz, 200 kHz and 400 kHz) and average output powers of >16 W ( at 1040 nm wavelength).

High-power femtosecond-terahertz pulse induces a wound response in mouse skin

PubMed Central

Kim, Kyu-Tae; Park, Jaehun; Jo, Sung Jin; Jung, Seonghoon; Kwon, Oh Sang; Gallerano, Gian Piero; Park, Woong-Yang; Park, Gun-Sik

2013-01-01

Terahertz (THz) technology has emerged for biomedical applications such as scanning, molecular spectroscopy, and medical imaging. Although a thorough assessment to predict potential concerns has to precede before practical utilization of THz source, the biological effect of THz radiation is not yet fully understood with scant related investigations. Here, we applied a femtosecond-terahertz (fs-THz) pulse to mouse skin to evaluate non-thermal effects of THz radiation. Analysis of the genome-wide expression profile in fs-THz-irradiated skin indicated that wound responses were predominantly mediated by transforming growth factor-beta (TGF-β) signaling pathways. We validated NFκB1- and Smad3/4-mediated transcriptional activation in fs-THz-irradiated skin by chromatin immunoprecipitation assay. Repeated fs-THz radiation delayed the closure of mouse skin punch wounds due to up-regulation of TGF-β. These findings suggest that fs-THz radiation initiate a wound-like signal in skin with increased expression of TGF-β and activation of its downstream target genes, which perturbs the wound healing process in vivo. PMID:23907528

Bright broadband coherent fiber sources emitting strongly blue-shifted resonant dispersive wave pulses

PubMed Central

Tu, Haohua; Lægsgaard, Jesper; Zhang, Rui; Tong, Shi; Liu, Yuan; Boppart, Stephen A.

2013-01-01

We predict and realize the targeted wavelength conversion from the 1550-nm band of a fs Er:fiber laser to an isolated band inside 370-850 nm, corresponding to a blue-shift of 700-1180 nm. The conversion utilizes resonant dispersive wave generation in widely available optical fibers with good efficiency (~7%). The converted band has a large pulse energy (~1 nJ), high spectral brightness (~1 mW/nm), and broad Gaussian-like spectrum compressible to clean transform-limited ~17 fs pulses. The corresponding coherent fiber sources open up portable applications of optical parametric oscillators and dual-output synchronized ultrafast lasers. PMID:24104233

Selective cell response on natural polymer bio-interfaces textured by femtosecond laser

NASA Astrophysics Data System (ADS)

Daskalova, A.; Trifonov, A.; Bliznakova, I.; Nathala, C.; Ajami, A.; Husinsky, W.; Declercq, H.; Buchvarov, I.

2018-02-01

This study reports on the evaluation of laser processed natural polymer-chitosan, which is under consideration as a biointerface used for temporary applications as skin and cartilage substitutes. It is employed for tissue engineering purposes, since it possesses a significant degree of biocompatibility and biodegradability. Chitosan-based thin films were processed by femtosecond laser radiation to enhance the surface properties of the material. Various geometry patterns were produced on polymer surfaces and employed to examine cellular adhesion and orientation. The topography of the modified zones was observed using scanning electron microscopy and confocal microscopy. Test of the material cytotoxicity was performed by evaluating the life/dead cell correlation. The obtained results showed that texturing with femtosecond laser pulses is appropriate method to initiate a predefined cellular response. Formation of surface modifications in the form of foams with an expansion of the material was created under laser irradiation with a number of applied laser pulses from N = 1-5. It is shown that irradiation with N > 5 results in disturbance of microfoam. Material characterization reveals a decrease in water contact angle values after laser irradiation of chitosan films. Consequently, changes in surface roughness of chitosan thin-film surface result in its functionalization. Cultivation of MC3T3 and ATMSC cells show cell orientational migration concerning different surface patterning. The influence of various pulse durations (varying from τ = 30-500 fs) over biofilms surface was examined regarding the evolution of surface morphology. The goal of this study was to define the optimal laser conditions (laser energy, number of applied pulses, and pulse duration) to alter surface wettability properties and porosity to improve material performance. The acquired set of results indicate the way to tune the surface properties to optimize cell-interface interaction.

Dynamic optical arbitrary waveform shaping based on cascaded optical modulators of single FBG.

PubMed

Chen, Jingyuan; Li, Peili

2015-08-10

A dynamic optical arbitrary waveform generation (O-AWG) with amplitude and phase independently controlled in optical modulators of single fiber Bragg Grating (FBG) has been proposed. This novel scheme consists of several optical modulators. In the optical modulator (O-MOD), a uniform FBG is used to filter spectral component of the input signal. The amplitude is controlled by fiber stretcher (FS) in Mach-Zehnder interference (MZI) structure through interference of two MZI arms. The phase is manipulated via the second FS in the optical modulator. This scheme is investigated by simulation. Consequently, optical pulse trains with different waveforms as well as pulse trains with nonuniform pulse intensity, pulse spacing and pulse width within each period are obtained through FSs adjustment to alter the phase shifts of signal in each O-MOD.

0.4-1.4 μm Visible to Near-Infrared Widely Broadened Super Continuum Generation with Er-doped Ultrashort Pulse Fiber Laser System

NASA Astrophysics Data System (ADS)

Nishizawa, Norihiko; Mitsuzawa, Hideyuki; Sumimura, Kazuhiko

2009-03-01

Visible to near-infrared widely broadened super continuum generation is demonstrated using ultrashort-pulse fiber laser system. Er-doped fiber chirped-pulse amplification system operated at 1550 nm in wavelength is used for the amplifier system, which generated ultrashort-pulse of 112 fs in FWHM with output power of 160 mW, on average. Almost pedestal free 200 fs second harmonic generation pulse is generated at 780 nm region using periodically poled LiNbO3 and conversion efficiency is as high as 37%. 0.45-1.40 μm widely broadened super continuum is generated in highly nonlinear photonic crystal fiber and spectrum flatness is within ±6 dB. All of the fiber devices are fusion spliced so that this system shows a good stability.

Parametric amplification of 100 fs mid-infrared pulses in ZnGeP₂ driven by a Ho:YAG chirped-pulse amplifier.

PubMed

Kanai, Tsuneto; Malevich, Pavel; Kangaparambil, Sarayoo Sasidharan; Ishida, Kakuta; Mizui, Makoto; Yamanouchi, Kaoru; Hoogland, Heinar; Holzwarth, Ronald; Pugzlys, Audrius; Baltuska, Andrius

2017-02-15

We report on the parametric generation of 100 fs sub-6-cycle 40 μJ pulses with the center wavelength at 5.2 μm using a 1 ps 2.1 μm pump laser and a dispersion management scheme based on bulk material. Our optically synchronized amplifier chain consists of a Ho:YAG chirped-pulse amplifier and white-light-seeded optical parametric amplifiers providing simultaneous passive carrier-envelope phase locking of three ultrashort longwave pulses at the pump, signal, and idler wavelengths corresponding, respectively, to 2.1, 3.5, and 5.2 μm. We also demonstrate bandwidth enhancement and efficient control over nonlinear spectral phase in the regime of cascaded χ² nonlinearity in ZnGeP₂.

Switchable Q-switched and modelocked operation in ytterbium doped fiber laser under all-normal-dispersion configuration

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

Mukhopadhyay, Pranb K., E-mail: pkm@rrcat.gov.in; Gupta, Pradeep K.; Singh, Chandra Pal

2015-03-15

We have constructed an Yb-doped fiber laser in all-normal-dispersion configuration which can be independently operated in Q-switched or modelocked configuration with the help of a simple fiber optic ring resonator (FORR). In the presence of FORR, the laser operates in Q-switched mode producing stable pulses in the range of 1 μs-200 ns with repetition rate in the range of 45 kHz-82 kHz. On the other hand, the laser can be easily switched to mode-locked operation by disjoining the FORR loop producing train of ultrashort pulses of ∼5 ps duration (compressible to ∼150 fs) at ∼38 MHz repetition rate. The transmissionmore » characteristics of FORR in combination with the nonlinear polarization rotation for passive Q-switching operation is numerically investigated and experimentally verified. The laser can serve as a versatile seed source for power amplifier which can be easily configured for application in the fields that require different pulsed fiber lasers.« less

ZnO synthesized in air by fs laser irradiation on metallic Zn thin films

NASA Astrophysics Data System (ADS)

Esqueda-Barrón, Y.; Herrera, M.; Camacho-López, S.

2018-05-01

We present results on rapid femtosecond laser synthesis of nanostructured ZnO. We used metallic Zn thin films to laser scan along straight tracks, until forming nanostructured ZnO. The synthesis dependence on laser irradiation parameters such as the per pulse fluence, integrated fluence, laser scan speed, and number of scans were explored carefully. SEM characterization showed that the morphology of the obtained ZnO is dictated by the integrated fluence and the laser scan speed; micro Raman and XRD results allowed to identify optimal laser processing conditions for getting good quality ZnO; and cathodoluminescence measurements demonstrated that a single laser scan at high per pulse laser fluence, but a medium integrated laser fluence and a medium laser scan speed favors a low density of point-defects in the lattice. Electrical measurements showed a correlation between resistivity of the laser produced ZnO and point-defects created during the synthesis. Transmittance measurements showed that, the synthesized ZnO can reach down to the supporting fused silica substrate under the right laser irradiation conditions. The physical mechanism for the formation of ZnO, under ultrashort pulse laser irradiation, is discussed in view of the distinct times scales given by the laser pulse duration and the laser pulse repetition rate.

Nanostructure array plasmas generated by femtosecond pulses at highly relativistic intensities

NASA Astrophysics Data System (ADS)

Hollinger, R. C.; Wong, Y.; Wong, S.; Rockwood, A.; Glasby, J.; Shlyaptsev, V.; Rocca, J. J.; Capeluto, M. G.; Kaymak, V.; Pukhov, A.

2017-10-01

The irradiation of high aspect ratio ordered nanostructure arrays with ultra-high contrast femtosecond laser pulses of relativistic intensity provides a unique combination of nearly complete optical absorption and drastically enhanced light penetration into near-solid density targets. This allows the material to be volumetrically heated deep into the ultra-high energy density regime. In previous experiments we have shown that irradiation of Ni and Au nanostructures with femtosecond pulses focused to an intensity of 5x1018 Wcm-2 generate multi-KeV near solid density plasmas in which atoms are ionized to the Ni+26 and Au+52 charge states. Here we present the first results of the irradiation of nanostructure arrays with highly relativistic pulses of intensities up to 5x1021Wcm-2. Silver and Rhodium nanowire arrays were irradiated with frequency-doubled pulses of 30 fs duration from a petawatt-class Ti:Sa laser. Time integrated x-ray spectra show the presence of He-like and Li-like emission. Results of experiments conducted with a variety of different nanowires diameters with a range of interwire spacings will be presented and compared to the result of 3D particle-in-cell-simulations. This work was supported by the Fusion Energy Program, Office of Science of the U.S Department of Energy.

Highly periodic laser-induced nanostructures on thin Ti and Cu foils for potential application in laser ion acceleration

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

Das, Susanta Kumar, E-mail: skdasfpy@kiit.ac.in; Andreev, Alexander; Braenzel, Julia

2016-03-21

The feasibility of femtosecond laser-induced periodic nanostructures on thin Ti and Cu foils (thickness down to 1 μm) is demonstrated. At pulse durations of 120 fs and a wavelength of 400 nm, periods of 61 nm to 320 nm were obtained. Particle-in-cell simulations of laser ion acceleration processes with such nanostructured targets indicate their potential for high energy particle physics applications. In particular, a measurable enhancement of the proton cut-off energy and a significant enhancement of the number of accelerated particles compared to non- or weakly structured targets of same thickness and material are expected.

Mode-locked solid state lasers using diode laser excitation

DOEpatents

Holtom, Gary R [Boston, MA

2012-03-06

A mode-locked laser employs a coupled-polarization scheme for efficient longitudinal pumping by reshaped laser diode bars. One or more dielectric polarizers are configured to reflect a pumping wavelength having a first polarization and to reflect a lasing wavelength having a second polarization. An asymmetric cavity provides relatively large beam spot sizes in gain medium to permit efficient coupling to a volume pumped by a laser diode bar. The cavity can include a collimation region with a controlled beam spot size for insertion of a saturable absorber and dispersion components. Beam spot size is selected to provide stable mode locking based on Kerr lensing. Pulse durations of less than 100 fs can be achieved in Yb:KGW.

Mid-IR lasers based on transition metal and rare-earth ion doped crystals

NASA Astrophysics Data System (ADS)

Mirov, S.; Fedorov, V.; Martyshkin, D.; Moskalev, I.; Mirov, M.; Vasilyev, S.

2015-05-01

We report a novel design of CW Cr2+:ZnS/ZnSe laser systems and demonstrate record output powers of 27.5 W at 2.45 μm and 13.9 W at 2.94 μm with slope efficiencies of 63.7% and 37.4%, respectively. Power scaling of ultra-fast Cr2+:ZnS/ZnSe Kerr mode-locked lasers beyond 2 W level, as well as the shortest pulse duration of 29 fs, are also reported. New development of Fe:ZnSe laser with average output power > 35 W at 4.1 μm output wavelength and 100 Hz pulse repetition rate (PRR) was achieved in a nonselective cavity. With intracavity prim selector, wavelength tunability of 3.88-4.17 μm was obtained with maximum average output power of 23 W. We also report new results on Tm-fiber pumped passively and actively Q-switched Ho:YAG laser systems. High peak power actively Q-switched Ho:YAG laser demonstrates stable operation with pulse energy > 50 mJ, 12 ns pulse duration, and 100-1000 Hz PRR which correspondents to more than 4 MW peak power. The actively Q-switched Ho:YAG laser system optimized for high repetition rate delivers 40 W average output power at 10-100 kHz PRR. The Ho:YAG laser with passive Q-switcher demonstrates constant 5 mJ output energy from 200 Hz to 2.23 kHz PRR with optical slope efficiency with respect to Tm-fiber laser of ~43%.

Robust, low-noise, polarization-maintaining mode-locked Er-fiber laser with a planar lightwave circuit (PLC) device as a multi-functional element.

PubMed

Kim, Chur; Kwon, Dohyeon; Kim, Dohyun; Choi, Sun Young; Cha, Sang Jun; Choi, Ki Sun; Yeom, Dong-Il; Rotermund, Fabian; Kim, Jungwon

2017-04-15

We demonstrate a new planar lightwave circuit (PLC)-based device, integrated with a 980/1550 wavelength division multiplexer, an evanescent-field-interaction-based saturable absorber, and an output tap coupler, which can be employed as a multi-functional element in mode-locked fiber lasers. Using this multi-functional PLC device, we demonstrate a simple, robust, low-noise, and polarization-maintaining mode-locked Er-fiber laser. The measured full-width at half-maximum bandwidth is 6 nm centered at 1555 nm, corresponding to 217 fs transform-limited pulse duration. The measured RIN and timing jitter are 0.22% [10 Hz-10 MHz] and 6.6 fs [10 kHz-1 MHz], respectively. Our results show that the non-gain section of mode-locked fiber lasers can be easily implemented as a single PLC chip that can be manufactured by a wafer-scale fabrication process. The use of PLC processes in mode-locked lasers has the potential for higher manufacturability of low-cost and robust fiber and waveguide lasers.

Ambient Molecular Analysis of Biological Tissue Using Low-Energy, Femtosecond Laser Vaporization and Nanospray Postionization Mass Spectrometry

NASA Astrophysics Data System (ADS)

Shi, Fengjian; Flanigan, Paul M.; Archer, Jieutonne J.; Levis, Robert J.

2016-03-01

Direct analysis of plant and animal tissue samples by laser electrospray mass spectrometry (LEMS) was investigated using low-energy, femtosecond duration laser vaporization at wavelengths of 800 and 1042 nm followed by nanospray postionization. Low-energy (<50 μJ), fiber-based 1042 nm LEMS (F-LEMS) allowed interrogation of the molecular species in fresh flower petal and leaf samples using 435 fs, 10 Hz bursts of 20 pulses from a Ytterbium-doped fiber laser and revealed comparable results to high energy (75-1120 μJ), 45 fs, 800 nm Ti:Sapphire-based LEMS (Ti:Sapphire-LEMS) measurements. Anthocyanins, sugars, and other metabolites were successfully detected and revealed the anticipated metabolite profile for the petal and leaf samples. Phospholipids, especially phosphatidylcholine, were identified from a fresh mouse brain section sample using Ti:Sapphire-LEMS without the application of matrix. These lipid features were suppressed in both the fiber-based and Ti:Sapphire-based LEMS measurements when the brain sample was prepared using the optimal cutting temperature compounds that are commonly used in animal tissue cryosections.

Analysis of laser damage tests on coatings designed for broad bandwidth high reflection of femtosecond pulses

DOE PAGES

Bellum, John Curtis; Winstone, Trevor; Lamaignere, Laurent; ...

2016-08-25

We designed an optical coating based on TiO 2/SiO 2 layer pairs for broad bandwidth high reflection (BBHR) at 45-deg angle of incidence (AOI), P polarization of femtosecond (fs) laser pulses of 900-nm center wavelength, and produced the coatings in Sandia’s large optics coater by reactive, ion-assisted e-beam evaporation. This paper reports on laser-induced damage threshold (LIDT) tests of these coatings. The broad HR bands of BBHR coatings pose challenges to LIDT tests. An ideal test would be in a vacuum environment appropriate to a high energy, fs-pulse, petawatt-class laser, with pulses identical to its fs pulses. Short of thismore » would be tests over portions of the HR band using nanosecond or sub-picosecond pulses produced by tunable lasers. Such tests could, e.g., sample 10-nm-wide wavelength intervals with center wavelengths tunable over the broad HR band. Alternatively, the coating’s HR band could be adjusted by means of wavelength shifts due to changing the AOI of the LIDT tests or due to the coating absorbing moisture under ambient conditions. In conclusion, we had LIDT tests performed on the BBHR coatings at selected AOIs to gain insight into their laser damage properties and analyze how the results of the different LIDT tests compare.« less

Analysis of laser damage tests on coatings designed for broad bandwidth high reflection of femtosecond pulses

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

Bellum, John Curtis; Winstone, Trevor; Lamaignere, Laurent

We designed an optical coating based on TiO 2/SiO 2 layer pairs for broad bandwidth high reflection (BBHR) at 45-deg angle of incidence (AOI), P polarization of femtosecond (fs) laser pulses of 900-nm center wavelength, and produced the coatings in Sandia’s large optics coater by reactive, ion-assisted e-beam evaporation. This paper reports on laser-induced damage threshold (LIDT) tests of these coatings. The broad HR bands of BBHR coatings pose challenges to LIDT tests. An ideal test would be in a vacuum environment appropriate to a high energy, fs-pulse, petawatt-class laser, with pulses identical to its fs pulses. Short of thismore » would be tests over portions of the HR band using nanosecond or sub-picosecond pulses produced by tunable lasers. Such tests could, e.g., sample 10-nm-wide wavelength intervals with center wavelengths tunable over the broad HR band. Alternatively, the coating’s HR band could be adjusted by means of wavelength shifts due to changing the AOI of the LIDT tests or due to the coating absorbing moisture under ambient conditions. In conclusion, we had LIDT tests performed on the BBHR coatings at selected AOIs to gain insight into their laser damage properties and analyze how the results of the different LIDT tests compare.« less

Femtosecond laser spectroscopy of the rhodopsin photochromic reaction: a concept for ultrafast optical molecular switch creation (ultrafast reversible photoreaction of rhodopsin).

PubMed

Smitienko, Olga; Nadtochenko, Victor; Feldman, Tatiana; Balatskaya, Maria; Shelaev, Ivan; Gostev, Fedor; Sarkisov, Oleg; Ostrovsky, Mikhail

2014-11-11

Ultrafast reverse photoreaction of visual pigment rhodopsin in the femtosecond time range at room temperature is demonstrated. Femtosecond two-pump probe experiments with a time resolution of 25 fs have been performed. The first рump pulse at 500 nm initiated cis-trans photoisomerization of rhodopsin chromophore, 11-cis retinal, which resulted in the formation of the primary ground-state photoproduct within a mere 200 fs. The second pump pulse at 620 nm with a varying delay of 200 to 3750 fs relative to the first рump pulse, initiated the reverse phototransition of the primary photoproduct to rhodopsin. The results of this photoconversion have been observed on the differential spectra obtained after the action of two pump pulses at a time delay of 100 ps. It was found that optical density decreased at 560 nm in the spectral region of bathorhodopsin absorption and increased at 480 nm, where rhodopsin absorbs. Rhodopsin photoswitching efficiency shows oscillations as a function of the time delay between two рump pulses. The quantum yield of reverse photoreaction initiated by the second pump pulse falls within the range 15%±1%. The molecular mechanism of the ultrafast reversible photoreaction of visual pigment rhodopsin may be used as a concept for the development of an ultrafast optical molecular switch.

Monolithic polarization maintaining fiber chirped pulse amplification (CPA) system for high energy femtosecond pulse generation at 1.03 µm.

PubMed

Kim, Kyungbum; Peng, Xiang; Lee, Wangkuen; Gee, Sangyoun; Mielke, Michael; Luo, Tao; Pan, Lei; Wang, Qing; Jiang, Shibin

2015-02-23

A monolithic polarization maintaining fiber chirped pulse amplification system with 25 cm Yb(3+)-doped high efficiency media fiber that generates 62 µJ sub-400 fs pulses with 25 W at 1.03 µm has recently been demonstrated.

Pulsed laser deposition to synthesize the bridge structure of artificial nacre: Comparison of nano- and femtosecond lasers

NASA Astrophysics Data System (ADS)

Melaibari, Ammar A.; Molian, Pal

2012-11-01

Nature offers inspiration to new adaptive technologies that allow us to build amazing shapes and structures such as nacre using synthetic materials. Consequently, we have designed a pulsed laser ablation manufacturing process involving thin film deposition and micro-machining to create hard/soft layered "brick-bridge-mortar" nacre of AlMgB14 (hard phase) with Ti (soft phase). In this paper, we report pulsed laser deposition (PLD) to mimic brick and bridge structures of natural nacre in AlMgB14. Particulate formation inherent in PLD is exploited to develop the bridge structure. Mechanical behavior analysis of the AlMgB14/Ti system revealed that the brick is to be 250 nm thick, 9 μm lateral dimensions while the bridge (particle) is to have a diameter of 500 nm for a performance equivalent to natural nacre. Both nanosecond (ns) and femtosecond (fs) pulsed lasers were employed for PLD in an iterative approach that involves varying pulse energy, pulse repetition rate, and target-to-substrate distance to achieve the desired brick and bridge characteristics. Scanning electron microscopy, x-ray photoelectron spectroscopy, and optical profilometer were used to evaluate the film thickness, particle size and density, stoichiometry, and surface roughness of thin films. Results indicated that both ns-pulsed and fs-pulsed lasers produce the desired nacre features. However, each laser may be chosen for different reasons: fs-pulsed laser is preferred for much shorter deposition time, better stoichiometry, uniform-sized particles, and uniform film thickness, while ns-pulsed laser is favored for industrial acceptance, reliability, ease of handling, and low cost.

Passive, active, and hybrid mode-locking in a self-optimized ultrafast diode laser

NASA Astrophysics Data System (ADS)

Alloush, M. Ali; Pilny, Rouven H.; Brenner, Carsten; Klehr, Andreas; Knigge, Andrea; Tränkle, Günther; Hofmann, Martin R.

2018-02-01

Semiconductor lasers are promising sources for generating ultrashort pulses. They are directly electrically pumped, allow for a compact design, and therefore they are cost-effective alternatives to established solid-state systems. Additionally, their emission wavelength depends on the bandgap which can be tuned by changing the semiconductor materials. Theoretically, the obtained pulse width can be few tens of femtoseconds. However, the generated pulses are typically in the range of several hundred femtoseconds only. Recently, it was shown that by implementing a spatial light modulator (SLM) for phase and amplitude control inside the resonator the optical bandwidth can be optimized. Consequently, by using an external pulse compressor shorter pulses can be obtained. We present a Fourier-Transform-External-Cavity setup which utilizes an ultrafast edge-emitting diode laser. The used InGaAsP diode is 1 mm long and emits at a center wavelength of 850 nm. We investigate the best conditions for passive, active and hybrid mode-locking operation using the method of self-adaptive pulse shaping. For passive mode-locking, the bandwidth is increased from 2.34 nm to 7.2 nm and ultrashort pulses with a pulse width of 216 fs are achieved after external pulse compression. For active and hybrid mode-locking, we also increased the bandwidth. It is increased from 0.26 nm to 5.06 nm for active mode-locking and from 3.21 nm to 8.7 nm for hybrid mode-locking. As the pulse width is strongly correlated with the bandwidth of the laser, we expect further reduction in the pulse duration by increasing the bandwidth.

Mode-locking peculiarities in an all-fiber erbium-doped ring ultrashort pulse laser with a highly-nonlinear resonator

NASA Astrophysics Data System (ADS)

Dvoretskiy, Dmitriy A.; Sazonkin, Stanislav G.; Kudelin, Igor S.; Orekhov, Ilya O.; Pnev, Alexey B.; Karasik, Valeriy E.; Denisov, Lev K.

2017-12-01

Today ultrashort pulse (USP) fiber lasers are in great demand in a frequency metrology field, THz pulse spectroscopy, optical communication, quantum optics application, etc. Therefore mode-locked (ML) fiber lasers have been extensively investigated over the last decade due the number of scientific, medical and industrial applications. It should be noted, that USP fiber lasers can be treated as an ideal platform to expand future applications due to the complex ML nonlinear dynamics in a laser resonator. Up to now a series of novel ML regimes have been investigated e.g. self-similar pulses, noise-like pulses, multi-bound solitons and soliton rain generation. Recently, we have used a highly nonlinear germanosilicate fiber (with germanium oxides concentration in the core 50 mol. %) inside the resonator for more reliable and robust launching of passive mode-locking based on the nonlinear polarization evolution effect in fibers. In this work we have measured promising and stable ML regimes such as stretched pulses, soliton rain and multi-bound solitons formed in a highly-nonlinear ring laser and obtained by intracavity group velocity dispersion (GVD) variation in slightly negative region. As a result, we have obtained the low noise ultrashort pulse generation with duration < 250 fs (more than 20 bound pulses when obtained multi-bound soliton generation with intertemporal width 5 ps) at a repetition rate 11.3 MHz (with signal-to-noise ratio at fundamental frequency > 59 dB) and relative intensity noise <-101 dBc / Hz.

Electronically tunable femtosecond all-fiber optical parametric oscillator for multi-photon microscopy

NASA Astrophysics Data System (ADS)

Hellwig, Tim; Brinkmann, Maximilian; Fallnich, Carsten

2018-02-01

We present a femtosecond fiber-based optical parametric oscillator (FOPO) for multiphoton microscopy with wavelength tuning by electronic repetition rate tuning in combination with a dispersive filter in the FOPO cavity. The all-spliced, all-fiber FOPO cavity is based on polarization-maintaining fibers and a broadband output coupler, allowing to get access to the resonant signal pulses as well as the idler pulses simultaneously. The system was pumped by a gain-switched fiber-coupled laser diode emitting pulses at a central wavelength of 1030 nm and an electronically tunable repetition frequency of about 2 MHz. The pump pulses were amplified in an Ytterbium fiber amplifier system with a pulse duration after amplification of 13 ps. Tuning of the idler (1140 nm - 1300 nm) and signal wavelengths (850 nm - 940 nm) was achieved by changing the repetition frequency of the pump laser by about 4 kHz. The generated signal pulses reached a pulse energy of up to 9.2 nJ at 920 nm and were spectrally broadened to about 6 nm in the FOPO by a combination of self-phase and cross-phase modulation. We showed external compression of the idler pulses at 920 nm to about 430 fs and appleid them to two-photon excitation microscopy with green fluorescent dyes. The presented system constitutes an important step towards a fully fiber-integrated all-electronically tunable and, thereby, programmable light source and already embodies a versatile and flexible light source for applications, e.g., for smart microscopy.

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.

Increase of intrinsic emittance induced by multiphoton photoemission from copper cathodes illuminated by femtosecond laser pulses

NASA Astrophysics Data System (ADS)

An, Chenjie; Zhu, Rui; Xu, Jun; Liu, Yaqi; Hu, Xiaopeng; Zhang, Jiasen; Yu, Dapeng

2018-05-01

Electron sources driven by femtosecond laser have important applications in many aspects, and the research about the intrinsic emittance is becoming more and more crucial. The intrinsic emittance of polycrystalline copper cathode, which was illuminated by femtosecond pulses (FWHM of the pulse duration was about 100 fs) with photon energies above and below the work function, was measured with an extremely low bunch charge (single-electron pulses) based on free expansion method. A minimum emittance was obtained at the photon energy very close to the effective work function of the cathode. When the photon energy decreased below the effective work function, emittance increased rather than decreased or flattened out to a constant. By investigating the dependence of photocurrent density on the incident laser intensity, we found the emission excited by pulsed photons with sub-work-function energies contained two-photon photoemission. In addition, the portion of two-photon photoemission current increased with the reduction of photon energy. We attributed the increase of emittance to the effect of two-photon photoemission. This work shows that conventional method of reducing the photon energy of excited light source to approach the room temperature limit of the intrinsic emittance may be infeasible for femtosecond laser. There would be an optimized photon energy value near the work function to obtain the lowest emittance for pulsed laser pumped photocathode.

Femtosecond fiber laser additive manufacturing and welding for 3D manufacturing

NASA Astrophysics Data System (ADS)

Huang, Huan; Nie, Bai; Wan, Peng; Yang, Lih-Mei; Bai, Shuang; Liu, Jian

2015-03-01

Due to the unique ultra-short pulse duration and high peak power, femtosecond (fs) laser has emerged as a powerful tool for many applications but has rarely been studied for 3D printing. In this paper, welding of both bulk and powder materials is demonstrated for the first time by using high energy and high repetition rate fs fiber lasers. It opens up new scenarios and opportunities for 3D printing with the following advantages - greater range of materials especially with high melting temperature, greater-than-ever level of precision (sub-micron) and less heat-affected-zone (HAZ). Mechanical properties (strength and hardness) and micro-structures (grain size) of the fabricated parts are investigated. For dissimilar materials bulk welding, good welding quality with over 210 MPa tensile strength is obtained. Also full melting of the micron-sized refractory powders with high melting temperature (above 3000 degree C) is achieved for the first time. 3D parts with shapes like ring and cube are fabricated. Not only does this study explore the feasibility of melting dissimilar and high melting temperature materials using fs lasers, but it also lays out a solid foundation for 3D printing of complex structure with designed compositions, microstructures and properties. This can greatly benefit the applications in automobile, aerospace and biomedical industries, by producing parts like nozzles, engines and miniaturized biomedical devices.

Generation of an isolated sub-40-as pulse using two-color laser pulses: Combined chirp effects

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

Feng, Liqiang; Chu, Tianshu; Institute for Computational Sciences and Engineering, Laboratory of New Fiber Materials and Modern Textile, the Growing Base for State Key Laboratory, Qingdao University, Qingdao, 266071

2011-11-15

In this paper, we theoretically discuss the combined chirp effects on the isolated attosecond generation when a model Ar is exposed to an intense 5-fs, 800-nm fundamental chirped pulse combined with a weak 10-fs, 1200-nm controlling chirped pulse. It shows that for the case of the chirp parameters {beta}{sub 1} = 6.1 (corresponding to the 800-nm field) and {beta}{sub 2} = 4.0 (corresponding to the 1200-nm field), both the harmonic cutoff energy and the supercontinuum can be remarkably extended resulting in a 663-eV bandwidth. Moreover, due to the introduction of the chirps, the short quantum path is selected to contributemore » to the harmonic spectrum. Finally, by superposing a properly selected harmonic spectrum in the supercontinuum region, an isolated pulse as short as 31 as (5 as) is generated without (with) phase compensation.« less

Gigahertz repetition rate, sub-femtosecond timing jitter optical pulse train directly generated from a mode-locked Yb:KYW laser.

PubMed

Yang, Heewon; Kim, Hyoji; Shin, Junho; Kim, Chur; Choi, Sun Young; Kim, Guang-Hoon; Rotermund, Fabian; Kim, Jungwon

2014-01-01

We show that a 1.13 GHz repetition rate optical pulse train with 0.70 fs high-frequency timing jitter (integration bandwidth of 17.5 kHz-10 MHz, where the measurement instrument-limited noise floor contributes 0.41 fs in 10 MHz bandwidth) can be directly generated from a free-running, single-mode diode-pumped Yb:KYW laser mode-locked by single-wall carbon nanotube-coated mirrors. To our knowledge, this is the lowest-timing-jitter optical pulse train with gigahertz repetition rate ever measured. If this pulse train is used for direct sampling of 565 MHz signals (Nyquist frequency of the pulse train), the jitter level demonstrated would correspond to the projected effective-number-of-bit of 17.8, which is much higher than the thermal noise limit of 50 Ω load resistance (~14 bits).

LIAD-fs scheme for studies of ultrafast laser interactions with gas phase biomolecules.

PubMed

Calvert, C R; Belshaw, L; Duffy, M J; Kelly, O; King, R B; Smyth, A G; Kelly, T J; Costello, J T; Timson, D J; Bryan, W A; Kierspel, T; Rice, P; Turcu, I C E; Cacho, C M; Springate, E; Williams, I D; Greenwood, J B

2012-05-14

Laser induced acoustic desorption (LIAD) has been used for the first time to study the parent ion production and fragmentation mechanisms of a biological molecule in an intense femtosecond (fs) laser field. The photoacoustic shock wave generated in the analyte substrate (thin Ta foil) has been simulated using the hydrodynamic HYADES code, and the full LIAD process has been experimentally characterised as a function of the desorption UV-laser pulse parameters. Observed neutral plumes of densities >10(9) cm(-3) which are free from solvent or matrix contamination demonstrate the suitability and potential of the source for studying ultrafast dynamics in the gas phase using fs laser pulses. Results obtained with phenylalanine show that through manipulation of fundamental femtosecond laser parameters (such as pulse length, intensity and wavelength), energy deposition within the molecule can be controlled to allow enhancement of parent ion production or generation of characteristic fragmentation patterns. In particular by reducing the pulse length to a timescale equivalent to the fastest vibrational periods in the molecule, we demonstrate how fragmentation of the molecule can be minimised whilst maintaining a high ionisation efficiency. This journal is © the Owner Societies 2012

Cell perforation mediated by plasmonic bubbles generated by a single near infrared femtosecond laser pulse.

PubMed

Boutopoulos, Christos; Bergeron, Eric; Meunier, Michel

2016-01-01

We report on transient membrane perforation of living cancer cells using plasmonic gold nanoparticles (AuNPs) enhanced single near infrared (NIR) femtosecond (fs) laser pulse. Under optimized laser energy fluence, single pulse treatment (τ = 45 fs, λ = 800 nm) resulted in 77% cell perforation efficiency and 90% cell viability. Using dark field and ultrafast imaging, we demonstrated that the generation of submicron bubbles around the AuNPs is the necessary condition for the cell membrane perforation. AuNP clustering increased drastically the bubble generation efficiency, thus enabling an effective laser treatment using low energy dose in the NIR optical therapeutical window. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

80-GHz AlGaInAs/InP 1.55 μm colliding-pulse mode-locked laser with low divergence angle and timing jitter

NASA Astrophysics Data System (ADS)

Hou, L. P.; Haji, M.; Li, C.; Qiu, B. C.; Bryce, A. C.

2011-07-01

We present an 80-GHz λ ~ 1.55 μm passively colliding-pulse mode-locked laser based on a novel AlGaInAs/InP epitaxial structure, which consists of a strained 3-quantum-well active layer incorporated with a passive far-field reduction layer. The device generated 910 fs pulses with a state-of-art timing jitter value of 190 fs (4 - 80 MHz), while demonstrating a low divergence angle (12.7°×26.3°) with two fold butt coupling efficiency to a flat cleaved single mode fiber when compared with the conventional mode-locked laser.

Hybrid fs/ps CARS for Sooting and Particle-laden Flames

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

Hoffmeister, Kathryn N. Gabet; Guildenbecher, Daniel Robert; Kearney, Sean P.

2015-12-01

We report the application of ultrafast rotational coherent anti-Stokes Raman scattering (CARS) for temperature and relative oxygen concentration measurements in the plume emanating from a burning aluminized ammonium perchlorate propellant strand. Combustion of these metal-based propellants is a particularly hostile environment for laserbased diagnostics, with intense background luminosity, scattering and beam obstruction from hot metal particles that can be as large as several hundred microns in diameter. CARS spectra that were previously obtained using nanosecond pulsed lasers in an aluminumparticle- seeded flame are examined and are determined to be severely impacted by nonresonant background, presumably as a result of themore » plasma formed by particulateenhanced laser-induced breakdown. Introduction of fs/ps laser pulses enables CARS detection at reduced pulse energies, decreasing the likelihood of breakdown, while simultaneously providing time-gated elimination of any nonresonant background interference. Temperature probability densities and temperature/oxygen correlations were constructed from ensembles of several thousand single-laser-shot measurements from the fs/ps rotational CARS measurement volume positioned within 3 mm or less of the burning propellant surface. Preliminary results in canonical flames are presented using a hybrid fs/ps vibrational CARS system to demonstrate our progress towards acquiring vibrational CARS measurements for more accurate temperatures in the very high temperature propellant burns.« less

High incidence of rainbow glare after femtosecond laser assisted-LASIK using the upgraded FS200 femtosecond laser.

PubMed

Zhang, Yu; Chen, Yue-Guo

2018-03-05

To compare the incidence of rainbow glare (RG) after femtosecond laser assisted-LASIK (FS-LASIK) using the upgraded FS200 femtosecond laser with different flap cut parameter settings. A consecutive series of 129 patients (255 eyes) who underwent FS-LASIK for correcting myopia and/or astigmatism using upgraded WaveLight FS200 femtosecond laser with the original settings was included in group A. Another consecutive series of 129 patients (255 eyes) who underwent FS-LASIK using upgraded WaveLight FS200 femtosecond laser with flap cut parameter settings changed (decreased pulse energy, spot and line separation) was included in group B. The incidence and fading time of RG, confocal microscopic image and postoperative clinical results were compared between the two groups. There were no differences between the two groups in age, baseline refraction, excimer laser ablation depth, postoperative uncorrected visual acuity and refraction. The incidence rate of RG in group A (35/255, 13.73%) was significantly higher than that in group B (4/255, 1.57%) (P < 0.05). The median fading time was 3 months in group A and 1 month in group B (P > 0.05).The confocal microscopic images showed wider laser spot spacing in group A than group B. The incidence of RG was significantly correlated with age and grouping (P < 0.05). The upgraded FS200 femtosecond laser with original flap cut parameter settings could increase the incidence of RG. The narrower grating size and lower pulse energy could ameliorate this side effect.

Proton acceleration by a pair of successive ultraintense femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Ferri, J.; Senje, L.; Dalui, M.; Svensson, K.; Aurand, B.; Hansson, M.; Persson, A.; Lundh, O.; Wahlström, C.-G.; Gremillet, L.; Siminos, E.; DuBois, T. C.; Yi, L.; Martins, J. L.; Fülöp, T.

2018-04-01

We investigate the target normal sheath acceleration of protons in thin aluminum targets irradiated at a relativistic intensity by two time-separated ultrashort (35 fs) laser pulses. When the full-energy laser pulse is temporally split into two identical half-energy pulses, and using target thicknesses of 3 and 6 μm, we observe experimentally that the second half-pulse boosts the maximum energy and charge of the proton beam produced by the first half-pulse for time delays below ˜0.6-1 ps. Using two-dimensional particle-in-cell simulations, we examine the variation of the proton energy spectra with respect to the time-delay between the two pulses. We demonstrate that the expansion of the target front surface caused by the first pulse significantly enhances the hot-electron generation by the second pulse arriving after a few hundreds of fs time delay. This enhancement, however, does not suffice to further accelerate the fastest protons driven by the first pulse once three-dimensional quenching effects have set in. This implies a limit to the maximum time delay that leads to proton energy enhancement, which we theoretically determine.

Tunable, continuous-wave Ti:sapphire channel waveguide lasers written by femtosecond and picosecond laser pulses.

PubMed

Grivas, Christos; Corbari, Costantino; Brambilla, Gilberto; Lagoudakis, Pavlos G

2012-11-15

Fabrication and cw lasing at 798.25 nm is reported for femtosecond (fs) and picosecond (ps) laser-inscribed channel waveguides in Ti:sapphire crystals. Lasing in channels written by fs (ps) pulses was obtained above a threshold of 84 mW (189 mW) with a maximum output power and a slope efficiency of 143 mW (45 mW) and 23.5% (7.1%), respectively. The emission wavelength was tuned over a 170 nm range by using a birefringent filter in an external cavity.

Accelerating protons to therapeutic energies with ultraintense, ultraclean, and ultrashort laser pulses

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

Bulanov, Stepan S.; Brantov, Andrei; Bychenkov, Valery Yu.

2008-05-15

Proton acceleration by high-intensity laser pulses from ultrathin foils for hadron therapy is discussed. With the improvement of the laser intensity contrast ratio to 10{sup -11} achieved on the Hercules laser at the University of Michigan, it became possible to attain laser-solid interactions at intensities up to 10{sup 22} W/cm{sup 2} that allows an efficient regime of laser-driven ion acceleration from submicron foils. Particle-in-cell (PIC) computer simulations of proton acceleration in the directed Coulomb explosion regime from ultrathin double-layer (heavy ions/light ions) foils of different thicknesses were performed under the anticipated experimental conditions for the Hercules laser with pulse energiesmore » from 3 to 15 J, pulse duration of 30 fs at full width half maximum (FWHM), focused to a spot size of 0.8 {mu}m (FWHM). In this regime heavy ions expand predominantly in the direction of laser pulse propagation enhancing the longitudinal charge separation electric field that accelerates light ions. The dependence of the maximum proton energy on the foil thickness has been found and the laser pulse characteristics have been matched with the thickness of the target to ensure the most efficient acceleration. Moreover, the proton spectrum demonstrates a peaked structure at high energies, which is required for radiation therapy. Two-dimensional PIC simulations show that a 150-500 TW laser pulse is able to accelerate protons up to 100-220 MeV energies.« less

Accelerating protons to therapeutic energies with ultraintense, ultraclean, and ultrashort laser pulses

PubMed Central

Bulanov, Stepan S.; Brantov, Andrei; Bychenkov, Valery Yu.; Chvykov, Vladimir; Kalinchenko, Galina; Matsuoka, Takeshi; Rousseau, Pascal; Reed, Stephen; Yanovsky, Victor; Krushelnick, Karl; Litzenberg, Dale William; Maksimchuk, Anatoly

2008-01-01

Proton acceleration by high-intensity laser pulses from ultrathin foils for hadron therapy is discussed. With the improvement of the laser intensity contrast ratio to 10−11 achieved on the Hercules laser at the University of Michigan, it became possible to attain laser-solid interactions at intensities up to 1022 W∕cm2 that allows an efficient regime of laser-driven ion acceleration from submicron foils. Particle-in-cell (PIC) computer simulations of proton acceleration in the directed Coulomb explosion regime from ultrathin double-layer (heavy ions∕light ions) foils of different thicknesses were performed under the anticipated experimental conditions for the Hercules laser with pulse energies from 3 to 15 J, pulse duration of 30 fs at full width half maximum (FWHM), focused to a spot size of 0.8 μm (FWHM). In this regime heavy ions expand predominantly in the direction of laser pulse propagation enhancing the longitudinal charge separation electric field that accelerates light ions. The dependence of the maximum proton energy on the foil thickness has been found and the laser pulse characteristics have been matched with the thickness of the target to ensure the most efficient acceleration. Moreover, the proton spectrum demonstrates a peaked structure at high energies, which is required for radiation therapy. Two-dimensional PIC simulations show that a 150–500 TW laser pulse is able to accelerate protons up to 100–220 MeV energies. PMID:18561651

Multiphoton near-infrared femtosecond laser pulse-induced DNA damage with and without the photosensitizer proflavine.

PubMed

Shafirovich, V; Dourandin, A; Luneva, N P; Singh, C; Kirigin, F; Geacintov, N E

1999-03-01

The excitation of pBr322 supercoiled plasmid DNA with intense near-IR 810 nm fs laser pulses by a simultaneous multiphoton absorption mechanism results in single-strand breaks after treatment of the irradiated samples with Micrococcus luteus UV endonuclease. This enzyme cleaves DNA strands at sites of cyclobutane dimers that are formed by the simultaneous absorption of three (or more) 810 nm IR photons (pulse width approximately 140 fs, 76 MHz pulse repetition, average power output focused through 10x microscope objective is approximately 1.2 MW/cm2). Direct single-strand breaks (without treatment with M. luteus) were not observed under these conditions. However, in the presence of 6 microM of the intercalator proflavine (PF), both direct single- and double-strand breaks are observed under conditions where substantial fractions of undamaged supercoiled DNA molecules are still present. The fraction of direct double-strand breaks is 30 +/- 5% of all measurable strand cleavage events, is independent of dosage (up to 6.4 GJ/cm2) and is proportional to In, where I is the average power/area of the 810 nm fs laser pulses, and n = 3 +/- 1. The nicking of two DNA strands in the immediate vicinity of the excited PF molecules gives rise to this double-strand cleavage. In contrast, excitation of the same samples under low-power, single-photon absorption conditions (approximately 400-500 nm) gives rise predominantly to single-strand breaks, but some double-strand breaks are observed at the higher dosages. Thus, single-photon excitation with 400-500 nm light and multiphoton activation of PF by near-IR fs laser pulses produces different distributions of single- and double-strand breaks. These results suggest that DNA strand cleavage originates from unrelaxed, higher excited states when PF is excited by simultaneous IR multiphoton absorption processes.

Enhanced laser proton acceleration by target ablation on a femtosecond laser system

NASA Astrophysics Data System (ADS)

Liao, Q.; Wu, M. J.; Gong, Z.; Geng, Y. X.; Xu, X. H.; Li, D. Y.; Shou, Y. R.; Zhu, J. G.; Li, C. C.; Yang, M.; Li, T. S.; Lu, H. Y.; Ma, W. J.; Zhao, Y. Y.; Lin, C.; Yan, X. Q.

2018-06-01

Proton acceleration during the interaction of an ultraintense (6 × 1019 W/cm2) femtosecond (fs) laser pulse with a thin (2.5 μm) foil target pre-ablated by a picosecond (ps) pulse is experimentally and numerically investigated. Enhancements in both proton cut-off energy and charge are observed with the target ablation due to a large number of energetic electrons generated from the preformed preplasma in front of the target. The enhanced proton beams are successfully collected at 4-9 MeV with ±4% energy spread and then transported to the irradiating platform. The results show that for the interaction between fs laser pulse and μm-thickness target, proton energy and charge can be enhanced by target ablation using a ps laser pulse, which is valuable for application like cancer radiotherapy.

Optical field ionization of atoms and ions using ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Fittinghoff, D. N.

1993-12-01

This dissertation research is an investigation of the strong optical field ionization of atoms and ions by 120-fs, 614-run laser pulses and 130-fs, 800-nm laser pulses. The experiments have shown ionization that is enhanced above the predictions of sequential tunneling models for He(+2), Ne(+2), and Ar(+2). The ion yields for He(+1), Ne(sup +1) and Ar(sup +1) agree well with the theoretical predictions of optical tunneling models. Investigation of the polarization dependence of the ionization indicates that the enhancements are consistent with a nonsequential ionization mechanism in which the linearly polarized field drives the electron wavefunction back toward the ion core and causes double ionization through inelastic e-2e scattering. These investigations have initiated a number of other studies by other groups and are of current scientific interest in the fields of high-irradiance laser-matter interactions and production of high-density plasmas. This work involved the following: (1) Understanding the characteristic nature of the ion yields produced by tunneling ionization through investigation of analytic solutions for tunneling at optical frequencies. (2) Extensive characterization of the pulses produced by 614-nm and 800-ran ultrashort pulse lasers. Absolute calibration of the irradiance scale produced shows the practicality of the inverse problem--measuring peak laser irradiance using ion yields. (3) Measuring the ion yields for three noble gases using linear, circular and elliptical polarizations of laser pulses at 614-nm and 800-nm. The measurements are some of the first measurements for pulse widths as low as 120-fs.

High-resolution single-shot spectral monitoring of hard x-ray free-electron laser radiation

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

Makita, M.; Karvinen, P.; Zhu, D.

We have developed an on-line spectrometer for hard x-ray free-electron laser (XFEL) radiation based on a nanostructured diamond diffraction grating and a bent crystal analyzer. Our method provides high spectral resolution, interferes negligibly with the XFEL beam, and can withstand the intense hard x-ray pulses at high repetition rates of >100 Hz. The spectrometer is capable of providing shot-to-shot spectral information for the normalization of data obtained in scientific experiments and optimization of the accelerator operation parameters. We have demonstrated these capabilities of the setup at the Linac Coherent Light Source, in self-amplified spontaneous emission mode at full energy ofmore » >1 mJ with a 120 Hz repetition rate, obtaining a resolving power of Ε/δΕ > 3 × 10 4. In conclusion, the device was also used to monitor the effects of pulse duration down to 8 fs by analysis of the spectral spike width.« less

High e+/e– ratio dense pair creation with 10 21W.cm –2 laser irradiating solid targets

DOE PAGES

Liang, E.; Clarke, T.; Henderson, A.; ...

2015-09-14

In this study, we report results of new pair creation experiments using ~100 Joule pulses of the Texas Petawatt Laser to irradiate solid gold and platinum targets, with intensities up to ~1.9 × 10 21 W.cm –2 and pulse durations as short as ~130 fs. Positron to electron (e+/e–) ratios >15% were observed for many thick disk and rod targets, with the highest e+/e– ratio reaching ~50% for a Pt rod. The inferred pair yield was ~ few ×10 10 with emerging pair density reaching ~10 15/cm 3 so that the pair skin depth becomes < pair jet transverse size.more » These results represent major milestones towards the goal of creating a significant quantity of dense pair-dominated plasmas with e+/e– approaching 100% and pair skin depth << pair plasma size, which will have wide-ranging applications to astrophysics and fundamental physics.« less

High-resolution single-shot spectral monitoring of hard x-ray free-electron laser radiation

DOE PAGES

Makita, M.; Karvinen, P.; Zhu, D.; ...

2015-10-16

We have developed an on-line spectrometer for hard x-ray free-electron laser (XFEL) radiation based on a nanostructured diamond diffraction grating and a bent crystal analyzer. Our method provides high spectral resolution, interferes negligibly with the XFEL beam, and can withstand the intense hard x-ray pulses at high repetition rates of >100 Hz. The spectrometer is capable of providing shot-to-shot spectral information for the normalization of data obtained in scientific experiments and optimization of the accelerator operation parameters. We have demonstrated these capabilities of the setup at the Linac Coherent Light Source, in self-amplified spontaneous emission mode at full energy ofmore » >1 mJ with a 120 Hz repetition rate, obtaining a resolving power of Ε/δΕ > 3 × 10 4. In conclusion, the device was also used to monitor the effects of pulse duration down to 8 fs by analysis of the spectral spike width.« less

Emerging trends in X-ray spectroscopic studies of plasma produced by intense laser beams

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

Arora, V., E-mail: arora@rrcat.gov.in; Chakera, J. A.; Naik, P. A.

2015-07-31

X-ray line emission from hot dense plasmas, produced by ultra-short high intensity laser systems, has been studied experimentally in recent years for applications in materials science as well as for back-lighter applications. By virtue of the CPA technology, several laser facilities delivering pulses with peak powers in excess of one petawatt (focused intensities > 10{sup 20} W-cm{sup −2}) have either been commissioned across the globe during the last few years or are presently under construction. On the other hand, hard x-ray sources on table top, generating ultra-short duration x-rays at a repetition rate up to 10 kHz, are routinely available formore » time resolved x-ray diffraction studies. In this paper, the recent experiments on x-ray spectroscopic studies of plasma produced by 45 fs, Ti:sapphire laser pulses (focused iintensity > 10{sup 18} W-cm{sup −2}) at RRCAT Indore will be presented.« less

All-fiber thulium/holmium-doped mode-locked laser by tungsten disulfide saturable absorber

NASA Astrophysics Data System (ADS)

Yu, Hao; Zheng, Xin; Yin, Ke; Cheng, Xiang'ai; Jiang, Tian

2017-01-01

A passively mode-locked thulium/holmium-doped fiber laser (THDFL) based on tungsten disulfide (WS2) saturable absorber (SA) was demonstrated. The WS2 nanosheets were prepared by liquid phase exfoliation method and the SA was fabricated by depositing the few-layer WS2 nanosheets on the surface of a fiber taper. The modulation depth, saturable intensity, and non-saturable loss of this SA were measured to be 8.2%, 0.82 GW cm-2, and 29.4%, respectively. Based on this SA, a stable mode-locked laser operated at 1.91 µm was achieved with pulse duration of 825 fs and repetition rate of 15.49 MHz, and signal-to-noise ratio (SNR) of 67 dB. Meanwhile, by increasing the pump power and adjusting the position of polarization controller, harmonic mode-locking operations were obtained. These results showed that the WS2 nanosheet-based SA could be served as a desirable candidate for a short-pulse mode locker at 2 µm wavelength.

Laser induced periodic surface structures on pyrolytic carbon prosthetic heart valve

NASA Astrophysics Data System (ADS)

Stepak, Bogusz D.; Łecka, Katarzyna M.; Płonek, Tomasz; Antończak, Arkadiusz J.

2016-12-01

Laser-induced periodic surface structures (LIPSS) can appear in different forms such as ripples, grooves or cones. Those highly periodic wavy surface features which are frequently smaller than incident light wavelength bring possibility of nanostructuring of many different materials. Furthermore, by changing laser parameters one can obtain wide spectrum of periodicities and geometries. The aim of this research was to determine possibility of nanostructuring pyrolytic carbon (PyC) heart valve leaflets using different irradiation conditions. The study was performed using two laser sources with different pulse duration (15 ps, 450 fs) as well as different wavelengths (1064, 532, 355 nm). Both low and high spatial frequency LIPSS were observed for each set of irradiation parameters. In case femtosecond laser pulses we obtained deep subwavelength ripple period which was even ten times smaller than applied wavelength. Obtained ripple period was ranging from 90 up to 860 nm. Raman spectra revealed the increase of disorder after laser irradiation which was comparable for both pico- and femtosecond laser.

Interaction Mechanisms of Cavitation Bubbles Induced by Spatially and Temporally Separated fs-Laser Pulses

PubMed Central

Tinne, Nadine; Kaune, Brigitte; Krüger, Alexander; Ripken, Tammo

2014-01-01

The emerging use of femtosecond lasers with high repetition rates in the MHz regime together with limited scan speed implies possible mutual optical and dynamical interaction effects of the individual cutting spots. In order to get more insight into the dynamics a time-resolved photographic analysis of the interaction of cavitation bubbles is presented. Particularly, we investigated the influence of fs-laser pulses and their resulting bubble dynamics with various spatial as well as temporal separations. Different time courses of characteristic interaction effects between the cavitation bubbles were observed depending on pulse energy and spatio-temporal pulse separation. These ranged from merely no interaction to the phenomena of strong water jet formation. Afterwards, the mechanisms are discussed regarding their impact on the medical application of effective tissue cutting lateral to the laser beam direction with best possible axial precision: the mechanical forces of photodisruption as well as the occurring water jet should have low axial extend and a preferably lateral priority. Furthermore, the overall efficiency of energy conversion into controlled mechanical impact should be maximized compared to the transmitted pulse energy and unwanted long range mechanical side effects, e.g. shock waves, axial jet components. In conclusion, these experimental results are of great importance for the prospective optimization of the ophthalmic surgical process with high-repetition rate fs-lasers. PMID:25502697

Controlled energy deposition and void-like modification inside transparent solids by two-color tightly focused femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Potemkin, Fedor; Mareev, Evgeniy; Bezsudnova, Yulia; Platonenko, Victor; Bravy, Boris; Gordienko, Vyacheslav

2017-04-01

We report a bulk void-like micromodification of fused silica using two-color μJ-energy level tightly focused (NA = 0.5) co-propagating seeding (visible, 0.62 μm) and heating (near-IR, 1.24 μm) femtosecond laser pulses with online third harmonic diagnostics of created microplasmas as well as subsequent laser-induced void-like defects. It has been shown experimentally and theoretically that production of seeding electrons through multiphoton ionization by visible laser pulses paves the way for controllability of the energy deposition and laser-induced micromodification via carrier heating by delayed infrared laser pulses inside the material. Experimental results demonstrate wide possibilities to increase the density of energy deposited up to 6 kJ cm-3 inside the dielectric by tight focusing of two color fs-laser pulses and elliptical polarization for infrared heating fs-laser pulses. The developed theoretical approach predicts the enhancement of deposited energy density up to 9 kJ cm-3 using longer (mid-IR) wavelengths for heating laser pulses.

Investigation of giant Kerr nonlinearity in quantum cascade lasers using mid-infrared femtosecond pulses

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

Cai, Hong; Liu, Sheng; Department of Physics, University of Maryland, Baltimore County

2015-02-02

We study the Kerr nonlinearity of quantum cascade lasers (QCLs) by coupling resonant and off-resonant mid-infrared (mid-IR) femtosecond (fs) pulses into an active QCL waveguide. We observe an increase in the spectral width of the transmitted fs pulses as the coupled mid-infrared (mid-IR) pulse power increases. This is explained by the self-phase modulation effect due to the large Kerr nonlinearity of QCL waveguides. We further confirm this effect by observing the intensity dependent far-field profile of the transmitted mid-IR pulses, showing the pulses undergo self-focusing as they propagate through the active QCL due to the intensity dependent refractive index. Wemore » experimentally estimate the nonlinear refractive index n{sub 2} of a QCL to be ∼8 × 10{sup −9 }cm{sup 2}/W using the far-field beam profile of the transmitted pulses. The finite-difference time-domain simulations of QCL waveguides with Kerr nonlinearity incorporated show similar behavior to the experimental results.« less

Inverse Calibration Free fs-LIBS of Copper-Based Alloys

NASA Astrophysics Data System (ADS)

Smaldone, Antonella; De Bonis, Angela; Galasso, Agostino; Guarnaccio, Ambra; Santagata, Antonio; Teghil, Roberto

2016-09-01

In this work the analysis by Laser Induced Breakdown Spectroscopy (LIBS) technique of copper-based alloys having different composition and performed with fs laser pulses is presented. A Nd:Glass laser (Twinkle Light Conversion, λ = 527 nm at 250 fs) and a set of bronze and brass certified standards were used. The inverse Calibration-Free method (inverse CF-LIBS) was applied for estimating the temperature of the fs laser induced plasma in order to achieve quantitative elemental analysis of such materials. This approach strengthens the hypothesis that, through the assessment of the plasma temperature occurring in fs-LIBS, straightforward and reliable analytical data can be provided. With this aim the capability of the here adopted inverse CF-LIBS method, which is based on the fulfilment of the Local Thermodynamic Equilibrium (LTE) condition, for an indirect determination of the species excitation temperature, is shown. It is reported that the estimated temperatures occurring during the process provide a good figure of merit between the certified and the experimentally determined composition of the bronze and brass materials, here employed, although further correction procedure, like the use of calibration curves, can be demanded. The reported results demonstrate that the inverse CF-LIBS method can be applied when fs laser pulses are used even though the plasma properties could be affected by the matrix effects restricting its full employment to unknown samples provided that a certified standard having similar composition is available.

Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber

NASA Astrophysics Data System (ADS)

Jia, Chenglai; Shastri, Bhavin J.; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R.; Saad, Mohammed; Chen, Lawrence R.

2016-11-01

Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm3+:ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber.

PubMed

Jia, Chenglai; Shastri, Bhavin J; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R; Saad, Mohammed; Chen, Lawrence R

2016-11-02

Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm 3+ :ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

Effectively Single-Mode Self-Recovering Ultrafast Nonlinear Nanowire Surface Plasmons

NASA Astrophysics Data System (ADS)

Tuniz, Alessandro; Weidlich, Stefan; Schmidt, Markus A.

2018-04-01

We report on a regime for surface-plasmon propagation, which is robust to defects and effectively single mode, and we exploit it for accessing the ultrafast nonlinear response of gold on centimeter-long subwavelength-diameter cylindrical nanowires. The hybrid plasmonic-photonic platform is formed by a gold nanowire, monolithically integrated into the core of an optical fiber. We show that, despite the dual-waveguide nature of this structure, the long-range surface plasmon is the only effectively propagating mode in the near infrared, which self-recovers in the presence of gaps via a light-recapturing effect. This self-recovery overcomes detrimental effects of wire discontinuities and enables measurements of the ultrafast nonlinearity of gold, which we perform for a 28-fs pulse duration.

Ultralow-threshold Kerr-lens mode-locked Ti:Al(2)O(3) laser.

PubMed

Kowalevicz, A M; Schibli, T R; Kärtner, F X; Fujimoto, J G

2002-11-15

An ultralow-threshold Kerr-lens mode-locked Ti:Al(2)O(3) laser achieved by use of an extended cavity design is demonstrated. Mode-locking thresholds as low as 156 mW are achieved. Pulses with durations as short as 14 fs and bandwidths of >100 nm with output powers of ~15 mW at 50-MHz repetition rates are generated by only 200 mW of pump power. Reducing the pump power requirements to a factor of 10x less than required by most conventional Kerr-lens mode-locked lasers permits inexpensive, low-power pump lasers to be used. This will facilitate the development of low-cost, high-performance femtosecond Ti:Al(2)O(3) laser technology.

Femtosecond laser-induced surface structures on carbon fibers.

PubMed

Sajzew, Roman; Schröder, Jan; Kunz, Clemens; Engel, Sebastian; Müller, Frank A; Gräf, Stephan

2015-12-15

The influence of different polarization states during the generation of periodic nanostructures on the surface of carbon fibers was investigated using a femtosecond laser with a pulse duration τ=300  fs, a wavelength λ=1025  nm, and a peak fluence F=4  J/cm². It was shown that linear polarization results in a well-aligned periodic pattern with different orders of magnitude concerning their period and an alignment parallel and perpendicular to fiber direction, respectively. For circular polarization, both types of uniform laser-induced periodic surface structures (LIPSS) patterns appear simultaneously with different dominance in dependence on the position at the fiber surface. Their orientation was explained by the polarization-dependent absorptivity and the geometrical anisotropy of the carbon fibers.

Pulse-Shaping-Based Nonlinear Microscopy: Development and Applications

NASA Astrophysics Data System (ADS)

Flynn, Daniel Christopher

The combination of optical microscopy and ultrafast spectroscopy make the spatial characterization of chemical kinetics on the femtosecond time scale possible. Commercially available octave-spanning Ti:Sapphire oscillators with sub-8 fs pulse durations can drive a multitude of nonlinear transitions across a significant portion of the visible spectrum with minimal average power. Unfortunately, dispersion from microscope objectives broadens pulse durations, decreases temporal resolution and lowers the peak intensities required for driving nonlinear transitions. In this dissertation, pulse shaping is used to compress laser pulses after the microscope objective. By using a binary genetic algorithm, pulse-shapes are designed to enable selective two-photon excitation. The pulse-shapes are demonstrated in two-photon fluorescence of live COS-7 cells expressing GFP-variants mAmetrine and tdTomato. The pulse-shaping approach is applied to a new multiphoton fluorescence resonance energy transfer (FRET) stoichiometry method that quantifies donor and acceptor molecules in complex, as well as the ratio of total donor to acceptor molecules. Compared to conventional multi-photon imaging techniques that require laser tuning or multiple laser systems to selectively excite individual fluorophores, the pulse-shaping approach offers rapid selective multifluorphore imaging at biologically relevant time scales. By splitting the laser beam into two beams and building a second pulse shaper, a pulse-shaping-based pump-probe microscope is developed. The technique offers multiple imaging modalities, such as excited state absorption (ESA), ground state bleach (GSB), and stimulated emission (SE), enhancing contrast of structures via their unique quantum pathways without the addition of contrast agents. Pulse-shaping based pump-probe microscopy is demonstrated for endogenous chemical-contrast imaging of red blood cells. In the second section of this dissertation, ultrafast spectroscopic techniques are used to characterize structure-function relationships of two-photon absorbing GFP-type probes and optical limiting materials. Fluorescence lifetimes of GFP-type probes are shown to depend on functional group substitution position, therefore, enabling the synthesis of designer probes for the possible study of conformation changes and aggregation in biological systems. Similarly, it is determined that small differences in the structure and dimensionality of organometallic macrocycles result in a diverse set of optical properties, which serves as a basis for the molecular level design of nonlinear optical materials.

TruMicro Series 2000 sub-400 fs class industrial fiber lasers: adjustment of laser parameters to process requirements

NASA Astrophysics Data System (ADS)

Kanal, Florian; Kahmann, Max; Tan, Chuong; Diekamp, Holger; Jansen, Florian; Scelle, Raphael; Budnicki, Aleksander; Sutter, Dirk

2017-02-01

The matchless properties of ultrashort laser pulses, such as the enabling of cold processing and non-linear absorption, pave the way to numerous novel applications. Ultrafast lasers arrived in the last decade at a level of reliability suitable for the industrial environment.1 Within the next years many industrial manufacturing processes in several markets will be replaced by laser-based processes due to their well-known benefits: These are non-contact wear-free processing, higher process accuracy or an increase of processing speed and often improved economic efficiency compared to conventional processes. Furthermore, new processes will arise with novel sources, addressing previously unsolved challenges. One technical requirement for these exciting new applications will be to optimize the large number of available parameters to the requirements of the application. In this work we present an ultrafast laser system distinguished by its capability to combine high flexibility and real time process-inherent adjustments of the parameters with industry-ready reliability. This industry-ready reliability is ensured by a long experience in designing and building ultrashort-pulse lasers in combination with rigorous optimization of the mechanical construction, optical components and the entire laser head for continuous performance. By introducing a new generation of mechanical design in the last few years, TRUMPF enabled its ultrashort-laser platforms to fulfill the very demanding requirements for passively coupling high-energy single-mode radiation into a hollow-core transport fiber. The laser architecture presented here is based on the all fiber MOPA (master oscillator power amplifier) CPA (chirped pulse amplification) technology. The pulses are generated in a high repetition rate mode-locked fiber oscillator also enabling flexible pulse bursts (groups of multiple pulses) with 20 ns intra-burst pulse separation. An external acousto-optic modulator (XAOM) enables linearization and multi-level quad-loop stabilization of the output power of the laser.2 In addition to the well-established platform latest developments addressed single-pulse energies up to 50 μJ and made femtosecond pulse durations available for the TruMicro Series 2000. Beyond these stabilization aspects this laser architecture together with other optical modules and combined with smart laser control software enables process-driven adjustments of the parameters (e. g. repetition rate, multi-pulse functionalities, pulse energy, pulse duration) by external signals, which will be presented in this work.

[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.

Direct observation of a photochemical activation energy: a case study of acetone photodissociation

NASA Astrophysics Data System (ADS)

Koch, Markus; Heim, Pascal; Thaler, Bernhard; Kitzler, Markus; Ernst, Wolfgang E.

2017-06-01

The ability to observe and quantify the conversion of electronic potential energy to vibrational kinetic energy in a molecule after photoexcitation is essential to understand and control the outcome of photoinduced molecular fragmentation. We exploit the high selectivity of photoelectron-photoion coincidence detection to distinguish different relaxation channels and observe the fragmentation behavior of each channel. We demonstrate the concept by investigating the fragmentation of gas-phase acetone molecules initiated by three-photon excitation to high lying Rydberg states between 9.0 and 9.5 eV above the ground state. By applying variations of the photon energy, pulse duration (100-200 fs) and pulse energy, we are able to fully characterize the fragmentation process. Rydberg states between 5s and 8s are populated, which undergo ultrafast internal conversion to lower states. The corresponding non-adiabatic dynamics in the neutral molecule cause the conversion of electronic to vibrational energy, leading to fragmentation. Our scheme allows us to directly measure the activation energy for fragmentation of acetone to an acetyl ion and a methyl radical, which we determine to be (0.79 ± 0.04) eV. Longer laser pulses result in an increased fragment-to-parent ratio, representing a higher probability for relaxation because the relaxation time constants are comparable to the pulse duration. Upon excitation to Rydberg states at 9.5 eV we surprisingly observe reduced fragmentation, although ˜2 eV are coupled into vibrational energy, indicating that different relaxation pathways become active, which results in a change of the redistribution of vibrational energy within the molecule. Fragmentation due to subsequent excitation of the cation is found to play a minor role.

Combined multiphoton imaging and automated functional enucleation of porcine oocytes using femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Kuetemeyer, Kai; Lucas-Hahn, Andrea; Petersen, Bjoern; Lemme, Erika; Hassel, Petra; Niemann, Heiner; Heisterkamp, Alexander

2010-07-01

Since the birth of ``Dolly'' as the first mammal cloned from a differentiated cell, somatic cell cloning has been successful in several mammalian species, albeit at low success rates. The highly invasive mechanical enucleation step of a cloning protocol requires sophisticated, expensive equipment and considerable micromanipulation skill. We present a novel noninvasive method for combined oocyte imaging and automated functional enucleation using femtosecond (fs) laser pulses. After three-dimensional imaging of Hoechst-labeled porcine oocytes by multiphoton microscopy, our self-developed software automatically identified the metaphase plate. Subsequent irradiation of the metaphase chromosomes with the very same laser at higher pulse energies in the low-density-plasma regime was used for metaphase plate ablation (functional enucleation). We show that fs laser-based functional enucleation of porcine oocytes completely inhibited the parthenogenetic development without affecting the oocyte morphology. In contrast, nonirradiated oocytes were able to develop parthenogenetically to the blastocyst stage without significant differences to controls. Our results indicate that fs laser systems have great potential for oocyte imaging and functional enucleation and may improve the efficiency of somatic cell cloning.

XUV-induced reactions in benzene on sub-10 fs timescale: nonadiabatic relaxation and proton migration.

PubMed

Galbraith, M C E; Smeenk, C T L; Reitsma, G; Marciniak, A; Despré, V; Mikosch, J; Zhavoronkov, N; Vrakking, M J J; Kornilov, O; Lépine, F

2017-08-02

Unraveling ultrafast dynamical processes in highly excited molecular species has an impact on our understanding of chemical processes such as combustion or the chemical composition of molecular clouds in the universe. In this article we use short (<7 fs) XUV pulses to produce excited cationic states of benzene molecules and probe their dynamics using few-cycle VIS/NIR laser pulses. The excited states produced by the XUV pulses lie in an especially complex spectral region where multi-electronic effects play a dominant role. We show that very fast τ ≈ 20 fs nonadiabatic processes dominate the relaxation of these states, in agreement with the timescale expected for most excited cationic states in benzene. In the CH 3 + fragmentation channel of the doubly ionized benzene cation we identify pathways that involve structural rearrangement and proton migration to a specific carbon atom. Further, we observe non-trivial transient behavior in this fragment channel, which can be interpreted either in terms of propagation of the nuclear wavepacket in the initially excited electronic state of the cation or as a two-step electronic relaxation via an intermediate state.

Low threshold L-band mode-locked ultrafast fiber laser assisted by microfiber-based carbon nanotube saturable absorber

NASA Astrophysics Data System (ADS)

Lau, K. Y.; Ng, E. K.; Abu Bakar, M. H.; Abas, A. F.; Alresheedi, M. T.; Yusoff, Z.; Mahdi, M. A.

2018-04-01

We demonstrate a passively mode-locked erbium-doped fiber laser in L-band wavelength region with low mode-locking threshold employing a 1425 nm pump wavelength. The mode-locking regime is generated by microfiber-based saturable absorber using carbon nanotube-polymer composite in a ring cavity. This carbon nanotube saturable absorber shows saturation intensity of 9 MW/cm2. In this work, mode-locking laser threshold is observed at 36.4 mW pump power. At the maximum pump power of 107.6 mW, we obtain pulse duration at full-width half-maximum point of 490 fs and time bandwidth product of 0.33, which corresponds to 3-dB spectral bandwidth of 5.8 nm. The pulse repetition rate remains constant throughout the experiment at 5.8 MHz due to fixed cavity length of 35.5 m. Average output power and pulse energy of 10.8 mW and 1.92 nJ are attained respectively through a 30% laser output extracted from the mode-locked cavity. This work highlights the feasibility of attaining a low threshold mode-locked laser source to be employed as seed laser in L-band wavelength region.

Scaling high-order harmonic generation from laser-solid interactions to ultrahigh intensity.

PubMed

Dollar, F; Cummings, P; Chvykov, V; Willingale, L; Vargas, M; Yanovsky, V; Zulick, C; Maksimchuk, A; Thomas, A G R; Krushelnick, K

2013-04-26

Coherent x-ray beams with a subfemtosecond (<10(-15)  s) pulse duration will enable measurements of fundamental atomic processes in a completely new regime. High-order harmonic generation (HOHG) using short pulse (<100  fs) infrared lasers focused to intensities surpassing 10(18)  W cm(-2) onto a solid density plasma is a promising means of generating such short pulses. Critical to the relativistic oscillating mirror mechanism is the steepness of the plasma density gradient at the reflection point, characterized by a scale length, which can strongly influence the harmonic generation mechanism. It is shown that for intensities in excess of 10(21)  W cm(-2) an optimum density ramp scale length exists that balances an increase in efficiency with a growth of parametric plasma wave instabilities. We show that for these higher intensities the optimal scale length is c/ω0, for which a variety of HOHG properties are optimized, including total conversion efficiency, HOHG divergence, and their power law scaling. Particle-in-cell simulations show striking evidence of the HOHG loss mechanism through parametric instabilities and relativistic self-phase modulation, which affect the produced spectra and conversion efficiency.

Strong-Field Emission From High Aspect Ratio Si Emitter Arrays

NASA Astrophysics Data System (ADS)

Keathley, Phillip; Swanwick, Michael; Sell, Alexander; Putnam, William; Guerrera, Stephen; Velásquez-García, Luis; Kärtner, Franz

2013-03-01

We discuss photoelectron emission from an arrays of high aspect ratio, sharp Si emitters both experimentally and theoretically. The structures are prepared from highly doped single-crystal silicon having a pencil-like shape with end radii of curvature of around 10 nm. The tips were illuminated at a grazing incidence of roughly 84deg.with a laser pulse having a center wavelength of 800 nm, and a pulse duration of 35 fs from a regenerative amplifier system. Native oxide coated Si tips were characterized using a time of flight (TOF) electron energy spectrometer. An annealing process was observed, resulting in a red shift of the energy spectra along with an increased electron yield. Total current yield from samples having the oxide stripped were also studied. Apeak total emission of 0.68 pC/bunch, corresponding to around 1.5x103 electrons/tip/pulse was observed at a DC bias of 70 V. Both spectral and current characterization results are consistent with a stong-field photoemission process at the surface of the tip apex. This work was funded by Defense Advanced Research Projects Agency (DARPA)/Microsystems Technology Office and the Space and Naval Warfare Systems Center (SPAWAR) under contract N66001-11-1-4192.

Enhancement of stability of aqueous suspension of alumina nanoparticles by femtosecond laser irradiation

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

Seo, Youngsang; Ha, Jeonghong; Kim, Dongsik, E-mail: dskim87@postech.ac.kr

2015-09-21

In this work, we report substantially enhanced colloidal stability of aqueous nanoparticle suspensions by ultrashort laser pulse irradiation. A Ti:Sapphire femtosecond laser (wavelength: 800 nm; pulse duration: 50 fs at full width at half maximum) was used to modify the electrochemical properties of nanoparticle suspensions at laser fluences below the particle ablation threshold. The colloidal stability of the suspension was evaluated by zeta potential and dynamic light scattering (DLS). The DLS results along with the images from transmission electron microscopy revealed that the laser irradiation caused no distinct morphological change to the individual alumina particles, but a substantial portion of themore » clustered particles was fragmented by the laser pulses, decreasing the apparent size of the suspended particles. Also, X-ray photoelectron spectroscopy analysis indicates that the laser irradiation modified the surface chemistry of the alumina particles. The stabilizing capability of the proposed technique was turned out to be better than that of conventional ultrasonic treatments. The stability of the laser-treated sample with no added surfactant was maintained for up to 30 days, without requiring an additional homogenizing process such as magnetic stirring.« less

Optical Waveguides Written in Silicon with Femtosecond Laser

NASA Astrophysics Data System (ADS)

Pavlov, Ihor; Tokel, Onur; Pavlova, Svitlana; Kadan, Viktor; Makey, Ghaith; Turnali, Ahmed; Ilday, Omer

Silicon is one of the most widely used materials in modern technology, ranging from electronics and Si-photonics to microfluidic and sensor applications. Despite the long history of Si-based devices, and the strong demand for opto-electronical integration, 3D Si laser processing technology is still challenging. Recently, nanosecond-pulsed laser was used to fabricate embedded holographic elements in Si. However, until now, there was no demonstration of femtosecond-laser-written optical elements inside Si. In this paper, we present optical waveguides written deep inside Si with 1.5 um femtosecond laser. The laser beam, with 2 uJ pulse energy and 350 fs pulse duration focused inside Si sample, produces permanent modification of Si. By moving the lens along the beam direction we were able to produce optical waveguides up to 5 mm long. The diameter of the waveguide is measured to be 10 um. The waveguides were characterized with both optical shadowgraphy and far field imaging after CW light coupling. We observed nearly single mode propagation of light inside of the waveguide. The obtained difference of refractive index inside of the waveguide, is 2.5*10-4. TUBITAK Grant 113M930, TUBITAK Grant 114F256.

Morphological effects of nanosecond- and femtosecond-pulsed laser ablation on human middle ear ossicles

NASA Astrophysics Data System (ADS)

Ilgner, Justus F.; Wehner, Martin; Lorenzen, Johann; Bovi, Manfred; Westhofen, Martin

2004-07-01

Introduction: Since the early 1980's, a considerable number of different laser systems have been introduced into reconstructive middle ear surgery. Depending on the ablation mode, however, pressure transients or thermal load to inner ear structures continue to be subject to discussion. Material and methods: We examined single spot ablations by a nanosecond-pulsed, frequency-tripled Nd:YAG-Laser (355 nm, beam diameter 10 μm, pulse rate 2 kHz, power 250 mW) on isolated human mallei. In a second set-up, a similar system (355 nm, beam diameter 20 μm, pulse rate 10 kHz, power 160-1500 mW) was coupled to a scanner to examine the morphology of bone surface ablation over an area of 1mm2. A third set-up employed a femtosecond-pulsed CrLiSAF-Oscillator (850 nm, pulse duration 100 fs, pulse energy 40μJ, beam diameter 36 μm, pulse rate 1 kHz) to compare these results with the former and with those obtained from a commercially available Er:YAG laser for ear surgery (Zeiss ORL E, 2940 nm, single pulse, energy 10-25 mJ). Results: In set-up 1 and 2, thermal effects in terms of marginal carbonization were visible in all single spot ablations of 1 s and longer. With ablations of 0.5 seconds, precise cutting margins with preservation of surrounding tissue could be observed. Cooling with saline solution resulted in no carbonization at 1500 mW and a scan speed of 500 mm/s. Set-up 3 equally showed no carbonization, although scanning times were longer and ablation less pronounced. Conclusion: Ultrashort pulsed laser systems could potentially aid further refinement of reconstructive microsurgery of the middle ear.

Octave-spanning mid-infrared pulses by plasma generation in air pumped with an Yb:KGW source

PubMed Central

Huang, Jinqing; Parobek, Alexander; Ganim, Ziad

2016-01-01

Femtosecond mid-infrared (IR) supercontinuum generation in gas media provides a broadband source suited for time-domain spectroscopies and microscopies. This technology has largely utilized <100 fs Ti:sapphire pump lasers. In this Letter, we describe the first plasma generation mid-IR source based on a 1030 nm, 171 fs Yb:KGW laser system; when its first three harmonics are focused in air, a conical mode supercontinuum is generated that spans <1000 to 2700 cm−1 with a 190 pJ pulse energy and 0.5% RMS stability. PMID:27805634

160 W 800 fs Yb:YAG single crystal fiber amplifier without CPA.

PubMed

Markovic, Vesna; Rohrbacher, Andreas; Hofmann, Peter; Pallmann, Wolfgang; Pierrot, Simonette; Resan, Bojan

2015-10-05

We demonstrate a compact and simple two-stage Yb:YAG single crystal fiber amplifier which delivers 160 W average power, 800 fs pulses without chirped pulse amplification. This is the highest average power of femtosecond laser based on SCF. Additionally, we demonstrate the highest small signal gain of 32.5 dB from the SCF in the first stage and the highest extraction efficiency of 42% in the second stage. The excellent performance of the second stage was obtained using the bidirectional pumping scheme, which is applied to SCF for the first time.

Numerical analysis of breakdown dynamics dependence on pulse width in laser-induced damage in fused silica: Role of optical system

NASA Astrophysics Data System (ADS)

Hamam, Kholoud A.; Gamal, Yosr E. E.-D.

2018-06-01

We report a numerical investigation of the breakdown and damage in fused silica caused by ultra-short laser pulses. The study based on a modified model (Gaabour et al., 2012) that solves the rate equation numerically for the electron density evolution during the laser pulse, under the combined effect of both multiphoton and electron impact ionization processes. Besides, electron loss processes due to diffusion out of the focal volume and recombination are also considered in this analysis. The model is applied to investigate the threshold intensity dependence on laser pulse width in the experimental measurements that are given by Liu et al. (2005). In this experiment, a Ti-sapphire laser source operating at 800 nm with pulse duration varies between 240 fs and 2.5 ps is used to irradiate a bulk of fused silica with dimensions 10 × 5 × 3 mm. The laser beam was focused into the bulk using two optical systems with effective numerical apertures (NA) 0.126 and 0.255 to give beam spot radius at the focus of the order 2.0 μm and 0.95 μm respectively. Reasonable agreement between the calculated thresholds and the measured ones is attained. Moreover, a study is performed to examine the respective role of the physical processes of the breakdown of fused silica in relation to the pulse width and focusing optical system. The analysis revealed a real picture of the location and size of the generated plasma.

Formation of 100-nm periodic structures on a titanium surface by exploiting the oxidation and third harmonic generation induced by femtosecond laser pulses.

PubMed

Li, Xian-Feng; Zhang, Cheng-Yun; Li, Hui; Dai, Qiao-Feng; Lan, Sheng; Tie, Shao-Long

2014-11-17

Periodic surface structures with periods as small as about one-tenth of the irradiating femtosecond (fs) laser light wavelength were created on the surface of a titanium (Ti) foil by exploiting laser-induced oxidation and third harmonic generation (THG). They were achieved by using 100-fs laser pulses with a repetition rate of 1 kHz and a wavelength ranging from 1.4 to 2.2 μm. It was revealed that an extremely thin TixOy layer was formed on the surface of the Ti foil after irradiating fs laser light with a fluence smaller than the ablation threshold of Ti, leading to a significant enhancement in THG which may exceed the ablation threshold of TixOy. As compared with Ti, the maximum efficacy factor for TixOy appears at a larger normalized wavevector in the direction perpendicular to the polarization of the fs laser light. As a result, the THG-dominated laser ablation of TixOy induces 100-nm periodic structures parallel to the polarization of the fs laser light. The depth of the periodic structures was found to be ~10 nm by atomic force microscopy and the formation of the thin TixOy layer was verified by energy dispersive X-ray spectroscopy.

Vector similariton erbium-doped all-fiber laser generating sub-100-fs nJ pulses at 100 MHz.

PubMed

Olivier, Michel; Piché, Michel

2016-02-08

Erbium-doped mode-locked fiber lasers with repetition rates comparable to those of solid-state lasers and generating nJ pulses are required for many applications. Our goal was to design a fiber laser that would meet such requirements, that could be built at relatively low cost and that would be reliable and robust. We thus developed a high-fundamental-repetition-rate erbium-doped all-fiber laser operating in the amplifier similariton regime. Experimental characterization shows that this laser, which is mode-locked by nonlinear polarization evolution, emits 76-fs pulses with an energy of 1.17 nJ at a repetition rate of 100 MHz. Numerical simulations support the interpretation of self-similar evolution of the pulse in the gain fiber. More specifically we introduce the concept of vector similariton in fiber lasers. The coupled x- and y- polarization components of such a pulse have a pulse profile with a linear chirp and their combined power profile evolves self-similarly when the nonlinear asymptotic regime is reached in the gain fiber.

Production and characterization of titanium (Ti), platinum (Pt) and tantalum (Ta) thin films for native DNA biosensors

NASA Astrophysics Data System (ADS)

Genç, Eminegül; Kepceoǧlu, Abdullah; Gezgin, Serap Yiǧit; Kars, Meltem Demirel; Kılıç, Hamdi Şükür

2017-02-01

The use of the femtosecond (fs) laser pulses for ablation applications have several advantageous and Laser-Induced Forward Transfer (LIFT) is an ablation-driven transfer process. The use of fs laser pulses for LIFT is gaining a great attraction nowadays. The most of the Direct Writing (DW) methods are laser based techniques and the LIFT technique is the one of them. This spectacular technique allows high resolution without lithographic processes. In this study, we have grown Ti, Pt and Ta thin films on the microscope slides by Pulse Laser Deposition (PLD) technique using Nd:YAG laser in the high vacuum condition. As a result, thin films produced in this work is a good candidate to produce native DNA biosensors based on LIFT technique.

What are the intensities and line-shapes of the twenty four polarization terms in coherent anti-Stokes Raman spectroscopy?

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

Niu, Kai; Lee, Soo-Y., E-mail: sooying@ntu.edu.sg

Coherent anti-Stokes Raman spectroscopy (CARS) is conventionally described by just one diagram/term where the three electric field interactions act on the ket side in a Feynman dual time-line diagram in a specific time order of pump, Stokes and probe pulses. In theory, however, any third-order nonlinear spectroscopy with three different electric fields interacting with a molecule can be described by forty eight diagrams/terms. They reduce to just 24 diagrams/terms if we treat the time ordering of the electric field interactions on the ket independently of those on the bra, i.e. the ket and bra wave packets evolve independently. The twentymore » four polarization terms can be calculated in the multidimensional, separable harmonic oscillator model to obtain the intensities and line-shapes. It is shown that in fs/ps CARS, for the two cases of off-resonance CARS in toluene and resonance CARS in rhodamine 6G, where we use a fs pump pulse, a fs Stokes pulse and a ps probe pulse, we obtain sharp vibrational lines in four of the polarization terms where the pump and Stokes pulses can create a vibrational coherence on the ground electronic state, while the spectral line-shapes of the other twenty terms are broad and featureless. The conventional CARS term with sharp vibrational lines is the dominant term, with intensity at least one order of magnitude larger than the other terms.« less

What are the intensities and line-shapes of the twenty four polarization terms in coherent anti-Stokes Raman spectroscopy?

NASA Astrophysics Data System (ADS)

Niu, Kai; Lee, Soo-Y.

2015-12-01

Coherent anti-Stokes Raman spectroscopy (CARS) is conventionally described by just one diagram/term where the three electric field interactions act on the ket side in a Feynman dual time-line diagram in a specific time order of pump, Stokes and probe pulses. In theory, however, any third-order nonlinear spectroscopy with three different electric fields interacting with a molecule can be described by forty eight diagrams/terms. They reduce to just 24 diagrams/terms if we treat the time ordering of the electric field interactions on the ket independently of those on the bra, i.e. the ket and bra wave packets evolve independently. The twenty four polarization terms can be calculated in the multidimensional, separable harmonic oscillator model to obtain the intensities and line-shapes. It is shown that in fs/ps CARS, for the two cases of off-resonance CARS in toluene and resonance CARS in rhodamine 6G, where we use a fs pump pulse, a fs Stokes pulse and a ps probe pulse, we obtain sharp vibrational lines in four of the polarization terms where the pump and Stokes pulses can create a vibrational coherence on the ground electronic state, while the spectral line-shapes of the other twenty terms are broad and featureless. The conventional CARS term with sharp vibrational lines is the dominant term, with intensity at least one order of magnitude larger than the other terms.

Ultrafast breakdown of dielectrics: new insight from double pump-probe experiments (Conference Presentation)

NASA Astrophysics Data System (ADS)

Guizard, Stéphane; Mouskeftaras, Alexandros; Bildé, Allan; Klimentov, Sergey M.; Fedorov, Nikita

2017-05-01

We investigate the mechanisms involved in the modification of dielectric materials by ultrashort laser pulses. We show that the use of a double pulse (fundamental and second harmonic of a Ti-Sa laser) excitation scheme allows getting new insight in the fundamental processes that occur during the interaction. We first measure the optical breakdown (OB) threshold map (intensity of first pulse versus intensity of second pulse) in various materials (Al2O3, MgO, α-SiO2). Using a simple model that includes multiphoton excitation followed by carrier heating in the conduction band, and assuming that OB occurs when a critical amount of energy is deposited in the material, we can satisfactorily reproduce this evolution of optical breakdown thresholds. The results demonstrate the dominant role of carrier heating in the energy transfer from the laser pulse to the solid. This important phenomenon is also highlighted by the kinetic energy distribution of photoelectrons observed in a photoemission experiment performed under similar conditions of double pulse excitation. Furthermore, we show, in the case of α-SiO2, that the formation of self-trapped exciton is in competition with the heating mechanism and thus play an important role especially when the pulse duration exceeds a few 100 fs. Finally, also in quartz or silica, we observe that the initial electronic excitation plays a key role in the formation of surface ripples and that their characteristics are determined by the first pulse, even at intensities well below OB threshold. The consequence of all these experimental results in the domain of UV or VUV induce damage will be discussed. In particular we demonstrate the possibility to dramatically increase the ablation efficiency by VUV light by using such double pulse scheme.

FIBER AND INTEGRATED OPTICS: Amplification of femtosecond pulses in single-mode fiber waveguides activated with Er3+ ions

NASA Astrophysics Data System (ADS)

Grudinin, A. B.; Dianov, Evgenii M.; Korobkin, D. V.; Prokhorov, A. M.; Semenov, V. A.; Khrushchev, I. Yu

1990-08-01

An experimental investigation was made of the process of amplification of femtosecond pulses in single-mode fiber waveguides activated with erbium ions. The amplified pulses were compressed from 80 to 55 fs in the course of their propagation. The energy of the pulses was estimated to be 5 nJ. The maximum gain was 26 dB.

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

High Current, Multi-Filament Photoconductive Semiconductor Switching

DTIC Science & Technology

2011-06-01

linear PCSS triggered with a 100 fs laser pulse . Figure 1. A generic photoconductive semiconductor switch rapidly discharges a charged capacitor...switching is the most critical challenge remaining for photoconductive semiconductor switch (PCSS) applications in Pulsed Power. Many authors have...isolation and control, pulsed or DC charging, and long device lifetime, provided the current per filament is limited to 20-30A for short pulse (10

Development and Implementation of High Bandwidth Pulsed Microactuators for Sub and Supersonic Applications

DTIC Science & Technology

2012-06-15

Microactuators of High –Speed Flow Control”, AIAA- 2938 , 2011. 12. Kreth, P., Solomon, J.T., Alvi, F.S., “Resonance-Enhanced High Frequency Micro...paper 2938 , 2011. 34. Ali, M.Y., Solomon, J.T., Gustavsson, J., Kumar, R., Alvi, F.S., “Control of Supersonic Cavity Flows Using High Bandwidth Micro

Sub-100 fs pulses from an all-polarization maintaining Yb-fiber oscillator with an anomalous dispersion higher-order-mode fiber.

PubMed

Verhoef, A J; Zhu, L; Israelsen, S Møller; Grüner-Nielsen, L; Unterhuber, A; Kautek, W; Rottwitt, K; Baltuška, A; Fernández, A

2015-10-05

We present an Yb-fiber oscillator with an all-polarization-maintaining cavity with a higher-order-mode fiber for dispersion compensation. The polarization maintaining higher order mode fiber introduces not only negative second order dispersion but also negative third order dispersion in the cavity, in contrast to dispersion compensation schemes used in previous demonstrations of all-polarization maintaining Yb-fiber oscillators. The performance of the saturable absorber mirror modelocked oscillator, that employs a free space scheme for coupling onto the saturable absorber mirror and output coupling, was investigated for different settings of the intracavity dispersion. When the cavity is operated with close to zero net dispersion, highly stable 0.5-nJ pulses externally compressed to sub-100-fs are generated. These are to our knowledge the shortest pulses generated from an all-polarization-maintaining Yb-fiber oscillator. The spectral phase of the output pulses is well behaved and can be compensated such that wing-free Fourier transform limited pulses can be obtained. Further reduction of the net intracavity third order dispersion will allow generating broader output spectra and consequently shorter pulses, without sacrificing pulse fidelity.

Laser-induced periodic surface structures on zinc oxide crystals upon two-colour femtosecond double-pulse irradiation

NASA Astrophysics Data System (ADS)

Höhm, S.; Rosenfeld, A.; Krüger, J.; Bonse, J.

2017-03-01

In order to study the temporally distributed energy deposition in the formation of laser-induced periodic surface structures (LIPSS) on single-crystalline zinc oxide (ZnO), two-colour double-fs-pulse experiments were performed. Parallel or cross-polarised double-pulse sequences at 400 and 800 nm wavelength were generated by a Mach-Zehnder interferometer, exhibiting inter-pulse delays up to a few picoseconds between the sub-ablation 50-fs-pulses. Twenty two-colour double-pulse sequences were collinearly focused by a spherical mirror to the sample surface. The resulting LIPSS periods and areas were analysed by scanning electron microscopy. The delay-dependence of these LIPSS characteristics shows a dissimilar behaviour when compared to the semiconductor silicon, the dielectric fused silica, or the metal titanium. A wavelength-dependent plasmonic mechanism is proposed to explain the delay-dependence of the LIPSS on ZnO when considering multi-photon excitation processes. Our results support the involvement of nonlinear processes for temporally overlapping pulses. These experiments extend previous two-colour studies on the indirect semiconductor silicon towards the direct wide band-gap semiconductor ZnO and further manifest the relevance of the ultrafast energy deposition for LIPSS formation.

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.

Functional enucleation of porcine oocytes for somatic cell nuclear transfer using femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Kuetemeyer, K.; Lucas-Hahn, A.; Petersen, B.; Hassel, P.; Lemme, E.; Niemann, H.; Heisterkamp, A.

2010-02-01

Cloning of several mammalian species has been achieved by somatic cell nuclear transfer over the last decade. However, this method still results in very low efficiencies originating from biological and technical aspects. The highly-invasive mechanical enucleation belongs to the technical aspects and requires considerable micromanipulation skill. In this paper, we present a novel non-invasive method for combined oocyte imaging and automated functional enucleation using femtosecond (fs) laser pulses. After three-dimensional imaging of Hoechst-labeled porcine oocytes by multiphoton microscopy, our self-developed software automatically determined the metaphase plate position and shape. Subsequent irradiation of this volume with the very same laser at higher pulse energies in the low-density-plasma regime was used for metaphase plate ablation. We show that functional fs laser-based enucleation of porcine oocytes completely inhibited further embryonic development while maintaining intact oocyte morphology. In contrast, non-irradiated oocytes were able to develop to the blastocyst stage without significant differences to control oocytes. Our results indicate that fs laser systems offer great potential for oocyte imaging and enucleation as a fast, easy to use and reliable tool which may improve the efficiency of somatic cell clone production.

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

Hoffmeister, Kathryn N. Gabet; Guildenbecher, Daniel Robert; Kearney, Sean P.

We report the application of ultrafast rotational coherent anti-Stokes Raman scattering (CARS) for temperature and relative oxygen concentration measurements in the plume emanating from a burning aluminized ammonium perchlorate propellant strand. Combustion of these metal-based propellants is a particularly hostile environment for laserbased diagnostics, with intense background luminosity, scattering and beam obstruction from hot metal particles that can be as large as several hundred microns in diameter. CARS spectra that were previously obtained using nanosecond pulsed lasers in an aluminumparticle- seeded flame are examined and are determined to be severely impacted by nonresonant background, presumably as a result of themore » plasma formed by particulateenhanced laser-induced breakdown. Introduction of fs/ps laser pulses enables CARS detection at reduced pulse energies, decreasing the likelihood of breakdown, while simultaneously providing time-gated elimination of any nonresonant background interference. Temperature probability densities and temperature/oxygen correlations were constructed from ensembles of several thousand single-laser-shot measurements from the fs/ps rotational CARS measurement volume positioned within 3 mm or less of the burning propellant surface. Preliminary results in canonical flames are presented using a hybrid fs/ps vibrational CARS system to demonstrate our progress towards acquiring vibrational CARS measurements for more accurate temperatures in the very high temperature propellant burns.« less

New experimental platform to study high density laser-compressed matter

DOE PAGES

Doppner, T.; LePape, S.; Ma, T.; ...

2014-09-26

We have developed a new experimental platform at the Linac Coherent Light Source (LCLS) which combines simultaneous angularly and spectrally resolved x-ray scatteringmeasurements. This technique offers a new insights on the structural and thermodynamic properties of warm dense matter. The < 50 fs temporal duration of the x-ray pulse provides near instantaneous snapshots of the dynamics of the compression. We present a proof of principle experiment for this platform to characterize a shock-compressed plastic foil. We observe the disappearance of the plastic semi-crystal structure and the formation of a compressed liquid ion-ion correlation peak. As a result, the plasma parametersmore » of shock-compressed plastic can be measured as well, but requires an averaging over a few tens of shots.« less

Large-scale studies of ion acceleration in laser-generated plasma at intensities from 1010 W/cm2 to 1019 W/cm2

NASA Astrophysics Data System (ADS)

Torrisi, L.

2018-02-01

A large-scale study of ion acceleration in laser-generated plasma, extended to intensities from 1010 W/cm2 up to 1019 W/cm2, is presented. Aluminium thick and thin foils were irradiated in high vacuum using different infrared lasers and pulse durations from ns up to fs scale. Plasma was monitored mainly using SiC detectors employed in time-of-flight configuration. Protons and aluminium ions, at different energies and yields, were measured as a function of the laser intensity. The discontinuity region between particle acceleration from both the backward plasma (BPA) in thick targets and the forward plasma in thin foils in the target normal sheath acceleration (TNSA) regimes were investigated.

Multipass OPCPA system at 100 kHz pumped by a CPA-free solid-state amplifier.

PubMed

Ahrens, J; Prochnow, O; Binhammer, T; Lang, T; Schulz, B; Frede, M; Morgner, U

2016-04-18

We present a compact few-cycle 100 kHz OPCPA system pumped by a CPA-free picosecond Nd:YVO₄ solid-state amplifier with all-optical synchronization to an ultra-broadband Ti:sapphire oscillator. This pump approach shows an exceptional conversion rate into the second harmonic of almost 78%. Efficient parametric amplification was realized by a two stage double-pass scheme with following chirped mirror compressor. The amount of superfluorescence was measured by an optical cross-correlation. Pulses with a duration of 8.7 fs at energies of 18 µJ are demonstrated. Due to the peak power of 1.26 GW, this simple OPCPA approach forms an ideal high repetition rate driving source for high-order harmonic generation.

Effects of electron relaxation on multiple harmonic generation from metal surfaces with femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Karatzas, N. E.; Georges, A. T.

2006-11-01

Calculations are presented for the first four (odd and even) harmonics of an 800 nm laser from a gold surface, with pulse widths ranging from 100 down to 14 fs. For peak laser intensities above 1 GW/cm 2 the harmonics are enhanced because of a partial depletion of the initial electron states. At 10 11 W/cm 2 of peak laser intensity the calculated conversion efficiency for 2nd-harmonic generation is 3 × 10 -9, while for the 5th-harmonic it is 10 -10. The generated harmonic pulses are broadened and delayed relative to the laser pulse because of the finite relaxation times of the excited electronic states. The finite electron relaxation times cause also the broadening of the autocorrelations of the laser pulses obtained from surface harmonic generation by two time-delayed identical pulses. Comparison with recent experimental results shows that the response time of an autocorrelator using nonlinear optical processes in a gold surface is shorter than the electron relaxation times. This seems to indicate that for laser pulses shorter than ˜30 fs, the fast nonresonant channel for multiphoton excitation via continuum-continuum transitions in metals becomes important as the resonant channel becomes slow (relative to the laser pulse) and less efficient.

Intensity noise reduction of a high-power nonlinear femtosecond fiber amplifier based on spectral-breathing self-similar parabolic pulse evolution

NASA Astrophysics Data System (ADS)

Wang, Sijia; Liu, Bowen; Song, Youjian; Hu, Minglie

2016-04-01

We report on a simple passive scheme to reduce the intensity noise of high-power nonlinear fiber amplifiers by use of the spectral-breathing parabolic evolution of the pulse amplification with an optimized negative initial chirp. In this way, the influences of amplified spontaneous emission (ASE) on the amplifier intensity noise can be efficiently suppressed, owing to the lower overall pulse chirp, shorter spectral broadening distance, as well as the asymptotic attractive nature of self-similar pulse amplification. Systematic characterizations of the relative intensity noise (RIN) of a free-running nonlinear Yb-doped fiber amplifier are performed over a series of initial pulse parameters. Experiments show that the measured amplifier RIN increases respect to the decreased input pulse energy, due to the increased amount of ASE noise. For pulse amplification with a proper negative initial chirp, the increase of RIN is found to be smaller than with a positive initial chirp, confirming the ASE noise tolerance of the proposed spectral-breathing parabolic amplification scheme. At the maximum output average power of 27W (25-dB amplification gain), the incorporation of an optimum negative initial chirp (-0.84 chirp parameter) leads to a considerable amplifier root-mean-square (rms) RIN reduction of ~20.5% (integrated from 10 Hz to 10 MHz Fourier frequency). The minimum amplifier rms RIN of 0.025% (integrated from 1 kHz to 5 MHz Fourier frequency) is obtained along with the transform-limited compressed pulse duration of 55fs. To our knowledge, the demonstrated intensity noise performance is the lowest RIN level measured from highpower free-running femtosecond fiber amplifiers.

PROCEEDING OF THE SEEDED X-RAY FREE ELECTRON LASER WORKSHOP.

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

WANG,X.J.; MURPHY,J.B.; YU,L.H.

2002-12-13

The underlying theory of a high gain free electron laser (FEL) has existed for two decades [1-2], but it is only in the last few years that these novel radiation sources have been realized experimentally. Several high gain FELs have successfully reached saturation in the infrared, visible and the VUV portion of the spectrum: the High Gain Harmonic Generation (HGHG) free electron lasers [3] at BNL and the Self Amplified Spontaneous Emission (SASE) FELs at LEUTL, VISA and TTF [4-6]. The outstanding challenges for future FELs are to extend high gain FELs to the X-ray regime, improve the longitudinal coherencemore » of the radiation using seeded FEL schemes and generate ultrashort pulses (<100 fs). The National Synchrotron Light Source (NSLS) of the Brookhaven National Laboratory (BNL) sponsored a Seeded X-ray Free Electron Laser Workshop on December 13-14, 2002 to explore these challenging issues. Representatives from BNL, DESY, LBNL, SLAC and UCLA made presentations on the novel schemes under consideration at their laboratories. Workshop participants had a lively discussion on the feasibility, performance and R&D issues associated with the seeded XFEL schemes. An improvement of the electron beam quality will certainly be necessary to drive the XFEL. Self-seeding SASE, cascaded HGHG, and SASE pulse compression FELs show the most promise for producing short pulse X-rays. Of these, only the self-seeded and HGHG schemes generate longitudinally coherent radiation. While the pulse length in the self-seeded scheme is determined by the electron bunch length ({approx}100 fs), the pulse length in the HGHG scheme is determined by the short pulse seed laser, and so can be much shorter ({approx} 20 fs).« less

Bringing PW-class lasers to XFELs (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tomizawa, Hiromitsu

2017-06-01

Experimental researches using high power optical lasers combined with free electron lasers (FELs) open new frontiers in high energy density (HED) sciences. Probing and pumping capabilities are dramatically improved due to the brightness of the XFEL pulses with ultrafast duration. Besides, the peak intensities of Ti:sapphire laser Chirped Pulse Amplification (CPA) systems reach petawatt (PW)-class with operating in few tens of fs and commercially available at a few Hz of repetition rate. We have been developing an experimental platform for HED sciences using high power, high intensity optical lasers at the XFEL facility, SACLA.Currently, an experimental platform with a dual 0.5 PW Ti:Sapphire laser system is under beam commissioning for experiments combined with the SACLA's x-ray beam for research objectives that require more peak power in the optical laser pulses with a few tens of fs. The optical laser system is designed to deliver two laser beams simultaneously with the maximum power of 0.5 PW in each into a target chamber located in an experimental hutch 6 (EH6) at BL2, which was recently commissioned as a SACLA's 2nd hard x-ray beamline. A focusing capability using sets of compound refractive lenses will be applied to increase the x-ray fluence on the target sample. One of the most key issues for the integrated experimental platform is development of diagnostics that meets requirements both from the high power laser (e.g. resistance to harsh environments) and from the XFEL (e.g. adaptation to the available data acquisition system). The status and future perspective of the development including automatic laser alignment systems will be reported in the presentation. We will discuss the most promising and important new physics experiments that will be enabled by the combination of PW-class lasers and the world-class FEL's x-ray beam.

PULSAR: A High-Repetition-Rate, High-Power, CE Phase-Locked Laser for the J.R. Macdonald Laboratory at Kansas State University

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

Ben-Itzhak, Itzik; Carnes, Kevin D.; Cocke, C. Lew

2014-05-09

This instrumentation grant funded the development and installation of a state-of-the-art laser system to be used for the DOE funded research at the J.R. Macdonald Laboratory at Kansas State University. Specifically, we purchased a laser based on the KMLABs Red-Dragon design, which has a high repetition rate of 10-20 kHz crucial for multi-parameter coincidence measurements conducted in our lab. This laser system is carrier-envelope phase (CEP) locked and provides pulses as short as 21 fs directly from the amplifier (see details below). In addition, we have developed a pulse compression setup that provides sub 5 fs pulses and a CEPmore » tagging capability that allows for long measurements of CEP dependent processes.« less

Anharmonic resonance absorption of short laser pulses in clusters: A molecular dynamics simulation study

NASA Astrophysics Data System (ADS)

Mahalik, S. S.; Kundu, M.

2016-12-01

Linear resonance (LR) absorption of an intense 800 nm laser light in a nano-cluster requires a long laser pulse >100 fs when Mie-plasma frequency ( ω M ) of electrons in the expanding cluster matches the laser frequency (ω). For a short duration of the pulse, the condition for LR is not satisfied. In this case, it was shown by a model and particle-in-cell (PIC) simulations [Phys. Rev. Lett. 96, 123401 (2006)] that electrons absorb laser energy by anharmonic resonance (AHR) when the position-dependent frequency Ω [ r ( t ) ] of an electron in the self-consistent anharmonic potential of the cluster satisfies Ω [ r ( t ) ] = ω . However, AHR remains to be a debate and still obscure in multi-particle plasma simulations. Here, we identify AHR mechanism in a laser driven cluster using molecular dynamics (MD) simulations. By analyzing the trajectory of each MD electron and extracting its Ω [ r ( t ) ] in the self-generated anharmonic plasma potential, it is found that electron is outer ionized only when AHR is met. An anharmonic oscillator model, introduced here, brings out most of the features of MD electrons while passing the AHR. Thus, we not only bridge the gap between PIC simulations, analytical models, and MD calculations for the first time but also unequivocally prove that AHR process is a universal dominant collisionless mechanism of absorption in the short pulse regime or in the early time of longer pulses in clusters.

All-fiber mode-locked erbium-doped ring laser based on a highly-nonlinear resonator with a low-noise ultrashort pulse generation

NASA Astrophysics Data System (ADS)

Kudelin, Igor S.; Dvoretskiy, Dmitriy A.; Sazonkin, Stanislav G.; Orekhov, Ilya O.; Pnev, Alexey B.; Karasik, Valeriy E.; Denisov, Lev K.

2018-04-01

Ultrashort pulse (USP) fiber lasers have found applications in such various fields as frequency metrology and spectroscopy, telecommunication systems, etc. For the last decade, mode-locking (ML) fiber lasers have been under carefully investigations for scientific, medical and industrial applications. Also, USP fiber sources can be treated as an ideal platform to expand future applications due to the complex ML nonlinear dynamics with a presence of high value of group velocity dispersion (GVD) and the third order dispersion in the resonator. For more reliable and robust launching of passive mode-locking based on a nonlinear polarization evolution, we used a highly nonlinear germanosilicate fiber (with germanium oxides concentration in the core 50 mol. %) inside the cavity and we have obtained ultrashort stretched pulses with a high peak power and energy. In this work relative intensity noise and frequency repetition stability is improved by applying isolator-polarizer (ISO-PM) with increased extinction ratio Pext and by compensation of intracavity group-velocity dispersion from the value β2 - 0.021 ps2 to - 0.0053 ps2 at 1550 nm. As a result, we have obtained the low-noise stretched pulse generation with duration 180 fs at a repetition rate 11.3 MHz (with signal-tonoise ratio at fundamental frequency 59 dB) with Allan deviation of a pulse repetition frequency for 1 s interval 5,7 * 10-9 and a relative intensity noise < -101 dBc / Hz.

Black phosphorus saturable absorber for ultrashort pulse generation

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

Sotor, J., E-mail: jaroslaw.sotor@pwr.edu.pl; Sobon, G.; Abramski, K. M.

Low-dimensional materials, due to their unique and versatile properties, are very interesting for numerous applications in electronics and optoelectronics. Recently rediscovered black phosphorus, with a graphite-like layered structure, can be effectively exfoliated up to the single atomic layer called phosphorene. Contrary to graphene, it possesses a direct band gap controllable by the number of stacked atomic layers. For those reasons, black phosphorus is now intensively investigated and can complement or replace graphene in various photonics and electronics applications. Here, we demonstrate that black phosphorus can serve as a broadband saturable absorber and can be used for ultrashort optical pulse generation.more » The mechanically exfoliated ∼300 nm thick layers of black phosphorus were transferred onto the fiber core, and under pulsed excitation at 1560 nm wavelength, its transmission increases by 4.6%. We have demonstrated that the saturable absorption of black phosphorus is polarization sensitive. The fabricated device was used to mode-lock an Er-doped fiber laser. The generated optical solitons with the 10.2 nm bandwidth and 272 fs duration were centered at 1550 nm. The obtained results unambiguously show that black phosphorus can be effectively used for ultrashort pulse generation with performances similar or even better than currently used graphene or carbon nanotubes. This application of black phosphorus proves its great potential to future practical use in photonics.« less

Carbon Nanotube-Poly(vinylalcohol) Nanocomposite Film Devices: Applications for Femtosecond Fiber Laser Mode Lockers and Optical Amplifier Noise Suppressors

NASA Astrophysics Data System (ADS)

Sakakibara, Youichi; Rozhin, Aleksey G.; Kataura, Hiromichi; Achiba, Yohji; Tokumoto, Madoka

2005-04-01

We fabricated single-wall carbon nanotube (SWNT)/poly(vinylalcohol) (PVA) nanocomposite freestanding films and examined their application in devices in which the saturable absorption of SWNTs at near-infrared optical telecommunication wavelengths can be utilized. In a passively mode-locked fiber laser, we integrated a 30-μm-thick SWNT/PVA film into a fiber connection adaptor with the film sandwiched by a pair of fiber ferrules. A ring fiber laser with a SWNT/PVA saturable absorber was operated very easily in the mode-locked short-pulse mode with a pulse width of about 500 fs. Reproducible stable device performance was confirmed. In examining noise suppression for optical amplifiers, mixed light of semiconductor amplified spontaneous emission (ASE) source and 370 fs laser pulses was passed through a 100-μm-thick SWNT/PVA film. The transmission loss of the femtosecond pulse light was smaller than that of the ASE light. This proved that the SWNT/PVA film has the ability to suppress ASE noise.

NRL Review, 2004

DTIC Science & Technology

2004-05-01

intense laser - matter interaction studies, including particle acceleration. A new 10 Hz ultrashort - pulse (40 fs), Ti:Sapphire...of high- intensity ultrashort laser pulses . He is the chief developer of the HELCAP laser propagation code. Prior to joining NRL, he was employed by...two short- pulse high- intensity lasers , the Table-Top Terawatt (T3) laser and the new Ti:Sapphire Femtosecond Laser (TFL) to study intense

Single-pass, efficient type-I phase-matched frequency doubling of high-power ultrashort-pulse Yb-fiber laser using LiB_3O_5

NASA Astrophysics Data System (ADS)

Shukla, Mukesh Kumar; Kumar, Samir; Das, Ritwick

2016-05-01

We report 48 % efficient single-pass second harmonic generation of high-power ultrashort-pulse ({≈ }250 fs) Yb-fiber laser by utilizing type-I phase matching in LiB_3O_5 (LBO) crystal. The choice of LBO among other borate crystals for high-power frequency doubling is essentially motivated by large thermal conductivity, low birefringence and weak group velocity dispersion. By optimally focussing the beam in a 4-mm-long LBO crystal, we have generated about 2.3 W of average power at 532 nm using 4.8 W of available pump power at 1064 nm. The ultrashort green pulses were found out to be near-transform limited sech^2 pulses with a pulse width of Δ τ ≈ 150 fs and being delivered at 78 MHz repetition rate. Due to appreciably low spatial walk-off angle for LBO ({≈ }0.4°), we obtain M^2<1.26 for the SH beam which signifies marginal distortion in comparison with the pump beam (M^2<1.15). We also discuss the impact of third-order optical nonlinearity of the LBO crystal on the generated ultrashort SH pulses.

175 fs-long pulses from a high-power single-mode Er-doped fiber laser at 1550 nm

NASA Astrophysics Data System (ADS)

Elahi, Parviz; Kalaycıoğlu, Hamit; Li, Huihui; Akçaalan, Önder; Ilday, F. Ömer

2017-11-01

Development of Er-doped ultrafast lasers have lagged behind the corresponding developments in Yb- and Tm-doped lasers, in particular, fiber lasers. Various applications benefit from operation at a central wavelength of 1.5 μm and its second harmonic, including emerging applications such as 3D processing of silicon and 3D printing based on two-photon polymerization. We report a simple, robust fiber master oscillator power amplifier operating at 1.55 μm, implementing chirp pulse amplification using single-mode fibers for diffraction-limited beam quality. The laser generates 80 nJ pulses at a repetition rate of 43 MHz, corresponding to an average power of 3.5 W, which can be compressed down to 175 fs. The generation of short pulses was achieved using a design which is guided by numerical simulations of pulse propagation and amplification and manages to overturn gain narrowing with self-phase modulation, without invoking excessive Raman scattering processes. The seed source for the two-stage amplifier is a dispersion-managed passively mode-locked oscillator, which generates a ∼40 nm-wide spectrum and 1.7-ps linearly chirped pulses.

Above scaling short-pulse ion acceleration from flat foil and ``Pizza-top Cone'' targets at the Trident laser facility

NASA Astrophysics Data System (ADS)

Flippo, Kirk; Hegelich, B. Manuel; Cort Gautier, D.; Johnson, J. Randy; Kline, John L.; Shimada, Tsutomu; Fernández, Juan C.; Gaillard, Sandrine; Rassuchine, Jennifer; Le Galloudec, Nathalie; Cowan, Thomas E.; Malekos, Steve; Korgan, Grant

2006-10-01

Ion-driven Fast Ignition (IFI) has certain advantages over electron-driven FI due to a possible large reduction in the amount of energy required. Recent experiments at the Los Alamos National Laboratory's Trident facility have yielded ion energies and efficiencies many times in excess of recent published scaling laws, leading to even more potential advantages of IFI. Proton energies in excess of 35 MeV have been observed from targets produced by the University of Nevada, Reno - dubbed ``Pizza-top Cone'' targets - at intensities of only 1x10^19 W/cm^2 with 20 joules in 600 fs. Energies in excess of 24 MeV were observed from simple flat foil targets as well. The observed energies, above any published scaling laws, are attributed to target production, preparation, and shot to shot monitoring of many laser parameters, especially the laser ASE prepulse level and laser pulse duration. The laser parameters are monitored in real-time to keep the laser in optimal condition throughout the run providing high quality, reproducible shots.

Reduction of timing jitter and intensity noise in normal-dispersion passively mode-locked fiber lasers by narrow band-pass filtering.

PubMed

Qin, Peng; Song, Youjian; Kim, Hyoji; Shin, Junho; Kwon, Dohyeon; Hu, Minglie; Wang, Chingyue; Kim, Jungwon

2014-11-17

Fiber lasers mode-locked with normal cavity dispersion have recently attracted great attention due to large output pulse energy and femtosecond pulse duration. Here we accurately characterized the timing jitter of normal-dispersion fiber lasers using a balanced cross-correlation method. The timing jitter characterization experiments show that the timing jitter of normal-dispersion mode-locked fiber lasers can be significantly reduced by using narrow band-pass filtering (e.g., 7-nm bandwidth filtering in this work). We further identify that the timing jitter of the fiber laser is confined in a limited range, which is almost independent of cavity dispersion map due to the amplifier-similariton formation by insertion of the narrow bandpass filter. The lowest observed timing jitter reaches 0.57 fs (rms) integrated from 10 kHz to 10 MHz Fourier frequency. The rms relative intensity noise (RIN) is also reduced from 0.37% to 0.02% (integrated from 1 kHz to 5 MHz Fourier frequency) by the insertion of narrow band-pass filter.

Experimental study of EUV mirror radiation damage resistance under long-term free-electron laser exposures below the single-shot damage threshold

PubMed Central

Makhotkin, Igor A.; Sobierajski, Ryszard; Chalupský, Jaromir; Tiedtke, Kai; de Vries, Gosse; Störmer, Michael; Scholze, Frank; Siewert, Frank; van de Kruijs, Robbert W. E.; Milov, Igor; Louis, Eric; Jacyna, Iwanna; Jurek, Marek; Klinger, Dorota; Syryanyy, Yevgen; Juha, Libor; Hájková, Věra; Saksl, Karel; Faatz, Bart; Keitel, Barbara; Plönjes, Elke; Toleikis, Sven; Loch, Rolf; Hermann, Martin; Strobel, Sebastian; Nienhuys, Han-Kwang; Gwalt, Grzegorz; Mey, Tobias; Enkisch, Hartmut

2018-01-01

The durability of grazing- and normal-incidence optical coatings has been experimentally assessed under free-electron laser irradiation at various numbers of pulses up to 16 million shots and various fluence levels below 10% of the single-shot damage threshold. The experiment was performed at FLASH, the Free-electron LASer in Hamburg, using 13.5 nm extreme UV (EUV) radiation with 100 fs pulse duration. Polycrystalline ruthenium and amorphous carbon 50 nm thin films on silicon substrates were tested at total external reflection angles of 20° and 10° grazing incidence, respectively. Mo/Si periodical multilayer structures were tested in the Bragg reflection condition at 16° off-normal angle of incidence. The exposed areas were analysed post-mortem using differential contrast visible light microscopy, EUV reflectivity mapping and scanning X-ray photoelectron spectroscopy. The analysis revealed that Ru and Mo/Si coatings exposed to the highest dose and fluence level show a few per cent drop in their EUV reflectivity, which is explained by EUV-induced oxidation of the surface. PMID:29271755

Experimental study of EUV mirror radiation damage resistance under long-term free-electron laser exposures below the single-shot damage threshold.

PubMed

Makhotkin, Igor A; Sobierajski, Ryszard; Chalupský, Jaromir; Tiedtke, Kai; de Vries, Gosse; Störmer, Michael; Scholze, Frank; Siewert, Frank; van de Kruijs, Robbert W E; Milov, Igor; Louis, Eric; Jacyna, Iwanna; Jurek, Marek; Klinger, Dorota; Nittler, Laurent; Syryanyy, Yevgen; Juha, Libor; Hájková, Věra; Vozda, Vojtěch; Burian, Tomáš; Saksl, Karel; Faatz, Bart; Keitel, Barbara; Plönjes, Elke; Schreiber, Siegfried; Toleikis, Sven; Loch, Rolf; Hermann, Martin; Strobel, Sebastian; Nienhuys, Han Kwang; Gwalt, Grzegorz; Mey, Tobias; Enkisch, Hartmut

2018-01-01

The durability of grazing- and normal-incidence optical coatings has been experimentally assessed under free-electron laser irradiation at various numbers of pulses up to 16 million shots and various fluence levels below 10% of the single-shot damage threshold. The experiment was performed at FLASH, the Free-electron LASer in Hamburg, using 13.5 nm extreme UV (EUV) radiation with 100 fs pulse duration. Polycrystalline ruthenium and amorphous carbon 50 nm thin films on silicon substrates were tested at total external reflection angles of 20° and 10° grazing incidence, respectively. Mo/Si periodical multilayer structures were tested in the Bragg reflection condition at 16° off-normal angle of incidence. The exposed areas were analysed post-mortem using differential contrast visible light microscopy, EUV reflectivity mapping and scanning X-ray photoelectron spectroscopy. The analysis revealed that Ru and Mo/Si coatings exposed to the highest dose and fluence level show a few per cent drop in their EUV reflectivity, which is explained by EUV-induced oxidation of the surface.

Performance of MgO:PPLN, KTA, and KNbO₃ for mid-wave infrared broadband parametric amplification at high average power.

PubMed

Baudisch, M; Hemmer, M; Pires, H; Biegert, J

2014-10-15

The performance of potassium niobate (KNbO₃), MgO-doped periodically poled lithium niobate (MgO:PPLN), and potassium titanyl arsenate (KTA) were experimentally compared for broadband mid-wave infrared parametric amplification at a high repetition rate. The seed pulses, with an energy of 6.5 μJ, were amplified using 410 μJ pump energy at 1064 nm to a maximum pulse energy of 28.9 μJ at 3 μm wavelength and at a 160 kHz repetition rate in MgO:PPLN while supporting a transform limited duration of 73 fs. The high average powers of the interacting beams used in this study revealed average power-induced processes that limit the scaling of optical parametric amplification in MgO:PPLN; the pump peak intensity was limited to 3.8  GW/cm² due to nonpermanent beam reshaping, whereas in KNbO₃ an absorption-induced temperature gradient in the crystal led to permanent internal distortions in the crystal structure when operated above a pump peak intensity of 14.4  GW/cm².

Key stages of material expansion in dielectrics upon femtosecond laser ablation revealed by double-color illumination time-resolved microscopy

NASA Astrophysics Data System (ADS)

Garcia-Lechuga, Mario; Solis, Javier; Siegel, Jan

2018-03-01

The physical origin of material removal in dielectrics upon femtosecond laser pulse irradiation (800 nm, 120 fs pulse duration) has been investigated at fluences slightly above ablation threshold. Making use of a versatile pump-probe microscopy setup, the dynamics and different key stages of the ablation process in lithium niobate have been monitored. The use of two different illumination wavelengths, 400 and 800 nm, and a rigorous image analysis combined with theoretical modelling, enables drawing a clear picture of the material excitation and expansion stages. Immediately after excitation, a dense electron plasma is generated. Few picoseconds later, direct evidence of a rarefaction wave propagating into the bulk is obtained, with an estimated speed of 3650 m/s. This process marks the onset of material expansion, which is confirmed by the appearance of transient Newton rings, which dynamically change during the expansion up to approximately 1 ns. Exploring delays up to 15 ns, a second dynamic Newton ring pattern is observed, consistent with the formation of a second ablation front propagating five times slower than the first one.

Two-octave spanning supercontinuum generation in stoichiometric silicon nitride waveguides pumped at telecom wavelengths.

PubMed

Porcel, Marco A G; Schepers, Florian; Epping, Jörn P; Hellwig, Tim; Hoekman, Marcel; Heideman, René G; van der Slot, Peter J M; Lee, Chris J; Schmidt, Robert; Bratschitsch, Rudolf; Fallnich, Carsten; Boller, Klaus-J

2017-01-23

We demonstrate supercontinuum generation in stoichiometric silicon nitride (Si₃N₄ in SiO₂) integrated optical waveguides, pumped at telecommunication wavelengths. The pump laser is a mode-locked erbium fiber laser at a wavelength of 1.56 µm with a pulse duration of 120 fs. With a waveguide-internal pulse energy of 1.4 nJ and a waveguide with 1.0 µm × 0.9 µm cross section, designed for anomalous dispersion across the 1500 nm telecommunication range, the output spectrum extends from the visible, at around 526 nm, up to the mid-infrared, at least to 2.6 µm, the instrumental limit of our detection. This output spans more than 2.2 octaves (454 THz at the -30 dB level). The measured output spectra agree well with theoretical modeling based on the generalized nonlinear Schrödinger equation. The infrared part of the supercontinuum spectra shifts progressively towards the mid-infrared, well beyond 2.6 µm, by increasing the width of the waveguides.

Homogeneous Emission Line Broadening in the Organo Lead Halide Perovskite CH3NH3PbI3-xClx.

PubMed

Wehrenfennig, Christian; Liu, Mingzhen; Snaith, Henry J; Johnston, Michael B; Herz, Laura M

2014-04-17

The organic-inorganic hybrid perovskites methylammonium lead iodide (CH3NH3PbI3) and the partially chlorine-substituted mixed halide CH3NH3PbI3-xClx emit strong and broad photoluminescence (PL) around their band gap energy of ∼1.6 eV. However, the nature of the radiative decay channels behind the observed emission and, in particular, the spectral broadening mechanisms are still unclear. Here we investigate these processes for high-quality vapor-deposited films of CH3NH3PbI3-xClx using time- and excitation-energy dependent photoluminescence spectroscopy. We show that the PL spectrum is homogenously broadened with a line width of 103 meV most likely as a consequence of phonon coupling effects. Further analysis reveals that defects or trap states play a minor role in radiative decay channels. In terms of possible lasing applications, the emission spectrum of the perovskite is sufficiently broad to have potential for amplification of light pulses below 100 fs pulse duration.

The generation of amplified spontaneous emission in high-power CPA laser systems.

PubMed

Keppler, Sebastian; Sävert, Alexander; Körner, Jörg; Hornung, Marco; Liebetrau, Hartmut; Hein, Joachim; Kaluza, Malte Christoph

2016-03-01

An analytical model is presented describing the temporal intensity contrast determined by amplified spontaneous emission in high-intensity laser systems which are based on the principle of chirped pulse amplification. The model describes both the generation and the amplification of the amplified spontaneous emission for each type of laser amplifier. This model is applied to different solid state laser materials which can support the amplification of pulse durations ≤350 fs . The results are compared to intensity and fluence thresholds, e.g. determined by damage thresholds of a certain target material to be used in high-intensity applications. This allows determining if additional means for contrast improvement, e.g. plasma mirrors, are required for a certain type of laser system and application. Using this model, the requirements for an optimized high-contrast front-end design are derived regarding the necessary contrast improvement and the amplified "clean" output energy for a desired focussed peak intensity. Finally, the model is compared to measurements at three different high-intensity laser systems based on Ti:Sapphire and Yb:glass. These measurements show an excellent agreement with the model.