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Sample records for measuring ultrashort pulses

  1. Measuring ultrashort pulses using frequency-resolved optical gating

    SciTech Connect

    Trebino, R.

    1993-12-01

    The purpose of this program is the development of techniques for the measurement of ultrafast events important in gas-phase combustion chemistry. Specifically, goals of this program include the development of fundamental concepts and spectroscopic techniques that will augment the information currently available with ultrafast laser techniques. Of equal importance is the development of technology for ultrafast spectroscopy. For example, methods for the production and measurement of ultrashort pulses at wavelengths important for these studies is an important goal. Because the specific vibrational motion excited in a molecule depends sensitively on the intensity, I(t), and the phase, {psi}(t), of the ultrashort pulse used to excite the motion, it is critical to measure both of these quantities for an individual pulse. Unfortunately, this has remained an unsolved problem for many years. Fortunately, this year, the authors present a technique that achieves this goal.

  2. Measurement of ultrashort pulses with a non-instantaneous nonlinearity

    SciTech Connect

    DeLong, K.W.; Ladera, C.L.; Trebino, R.; Kohler, B.; Wilson, K.R.

    1995-02-01

    We show how non-instantaneous nonlinearities can be used to characterize an ultrashort pulse in an extension of the Frequency-Resolved Optical Gating technique. We demonstrate this principle using the Raman effect in fused silica.

  3. Ultrashort Pulse Reflectometry (USPR) Density Profile Measurements on GAMMA-10

    NASA Astrophysics Data System (ADS)

    Domier, C. W.; Roh Luhmann, Y., Jr.; Mase, A.; Kubota, S.

    1999-11-01

    Ultrashort pulse reflectometry (USPR) involves time-of-flight measurements of extremely broadband, high speed chirped signals ( ns sweep times). A multichannel USPR system has been installed on the central cell of the GAMMA-10 mirror machine located at the University of Tsukuba, Japan. Here, the output from a 65 ps FWHM impulse generator is stretched and amplified to form a 10 ns duration, 11-18 GHz chirp signal. A five channel X-mode USPR receiver, with frequency channels at 12, 13, 15, 16 and 17 GHz, measures the double-pass time delay of each reflected subpacket simultaneously with 25 ps time resolution. Density profile and fluctuation data collected on GAMMA-10 will be presented.

  4. Effect of noise on Frequency-Resolved Optical Gating measurements of ultrashort pulses

    SciTech Connect

    Fittinghoff, D.N.; DeLong, K.W.; Ladera, C.L.; Trebino, R.

    1995-02-01

    We study the effects of noise in Frequency-Resolved Optical Gating measurements of ultrashort pulses. We quantify the measurement accuracy in the presence of additive, muliplicative, and quantization noise, and discuss filtering and pre-processing of the data.

  5. Time-dependent intensity and phase measurements of ultrashort laser pulses as short as 10 fs

    SciTech Connect

    DeLong, K.W.; Fittinghoff, D.N.; Ladera, C.L.; Trebino, R.; Taft, G.; Rundquist, A.; Murnane, M.M.; Kapteyn, H.C.; Christov, I.P.

    1995-05-01

    Frequency-Resolved Optical Gating (FROG) measures the time-dependent intensity and phase of an ultrashort laser pulse. Using FROG, we have tested theories for the operation of sub{minus}10 fs laser oscillators.

  6. Phase control and measurement of ultrashort optical pulses

    SciTech Connect

    Sullivan, A.; White, W.E.; Chu, K.C.; Heritage, J.P.

    1995-02-10

    We have used the Direct Optical Spectral Phase Measurement (DOSPM) technique to characterize the cubic phase tuning ability of our pulse stretcher. We have compared the measured phase to the phase determined from cross-correlation measurements.

  7. Ultrashort-laser-pulse measurement using swept beams.

    PubMed

    O'Shea, D; Kimmel, M; O'Shea, P; Trebino, R

    2001-09-15

    We demonstrate a frequency-resolved optical gating (FROG) device that uses a sweepshot geometry that combines the advantages of multishot and single-shot pulse-measurement devices, has only one moving part, a galvanometer, and requires no computer control. Like a multishot device, it focuses the beam to a small spot (rather than a line focus) and has a high intensity in the nonlinear medium. Like single-shot devices, it makes measurements quickly, generating an entire FROG trace on a single camera screen (rather than requiring many camera downloads). PMID:18049632

  8. Frequency-resolved optical gating measurement of ultrashort pulses by using single nanowire.

    PubMed

    Yu, Jiaxin; Liao, Feng; Gu, Fuxing; Zeng, Heping

    2016-01-01

    The use of ultrashort pulses for fundamental studies and applications has been increasing rapidly in the past decades. Along with the development of ultrashort lasers, exploring new pulse diagnositic approaches with higher signal-to-noise ratio have attracted great scientific and technological interests. In this work, we demonstrate a simple technique of ultrashort pulses characterization with a single semiconductor nanowire. By performing a frequency-resolved optical gating method with a ZnO nanowire coupled to tapered optical microfibers, the phase and amplitude of a pulse series are extracted. The generated signals from the transverse frequency conversion process can be spatially distinguished from the input, so the signal-to-noise ratio is improved and permits lower energy pulses to be identified. Besides, since the nanometer scale of the nonlinear medium provides relaxed phase-matching constraints, a measurement of 300-nm-wide supercontinuum pulses is achieved. This system is highly compatible with standard optical fiber systems, and shows a great potential for applications such as on-chip optical communication. PMID:27609521

  9. Frequency-resolved optical gating measurement of ultrashort pulses by using single nanowire

    PubMed Central

    Yu, Jiaxin; Liao, Feng; Gu, Fuxing; Zeng, Heping

    2016-01-01

    The use of ultrashort pulses for fundamental studies and applications has been increasing rapidly in the past decades. Along with the development of ultrashort lasers, exploring new pulse diagnositic approaches with higher signal-to-noise ratio have attracted great scientific and technological interests. In this work, we demonstrate a simple technique of ultrashort pulses characterization with a single semiconductor nanowire. By performing a frequency-resolved optical gating method with a ZnO nanowire coupled to tapered optical microfibers, the phase and amplitude of a pulse series are extracted. The generated signals from the transverse frequency conversion process can be spatially distinguished from the input, so the signal-to-noise ratio is improved and permits lower energy pulses to be identified. Besides, since the nanometer scale of the nonlinear medium provides relaxed phase-matching constraints, a measurement of 300-nm-wide supercontinuum pulses is achieved. This system is highly compatible with standard optical fiber systems, and shows a great potential for applications such as on-chip optical communication. PMID:27609521

  10. Phase retrieval and time-frequency methods in the measurement of ultrashort laser pulses

    SciTech Connect

    DeLong, K.W.; Fittinghoff, D.N.; Ladera, C.L.; Trebino, R.

    1995-02-01

    Recently several techniques have become available to measure the time- (or frequency-) dependent intensity and phase of ultrashort laser pulses. One of these, Frequency-Resolved Optical Gating (FROG), is rigorous and has achieved single-laser-shot operation. FROG combines the concepts of time-frequency analysis in the form of spectrogram generation (in order to create a two-dimensional problem), and uses a phase-retrieval-based algorithm to invert the experimental data to yield the intensity and phase of the laboratory laser pulse. In FROG it is easy to generate a spectrogram of the unknown signal, and inversion of the spectrogram to recover the signal is the main goal. Because the temporal width of a femtosecond laser pulse is much shorter than anything achievable by electronics, FROG uses the pulse to measure itself. In FROG, the laser pulse is split into two replicas of itself by a partially reflecting beamsplitter, and the two replicas interact with each other in a medium with an instantaneous nonlinear-optical response. This interaction generates a signal field that is then frequency-resolved using a spectrometer. The spectrum of the signal field is measured for all relevant values of the temporal delay between the two pulses. Here, the authors employ FROG and FROG related techniques to measure the time-dependent intensity and phase of an ultrashort laser pulse.

  11. Frequency-resolved optical-gating measurements of ultrashort pulses using surface third-harmonic generation

    SciTech Connect

    Tsang, T.; Krumbuegel, M.A.; DeLong, K.W.; Fittinghoff, D.N.; Trebino, R.

    1996-09-01

    We demonstrate what is to our knowledge the first frequency-resolved optical gating (FROG) technique to measure ultrashort pulses from an unamplified Ti:sapphire laser oscillator without direction-of-time ambiguity. This technique utilizes surface third-harmonic generation as the nonlinear-optical effect and, surprisingly, is the most sensitive third-order FROG geometry yet. {copyright} {ital 1996 Optical Society of America.}

  12. Measurement of complex ultrashort laser pulses using frequency-resolved optical gating

    NASA Astrophysics Data System (ADS)

    Xu, Lina

    This thesis contains three components of research: a detailed study of the performance of Frequency-Resolved Optical Gating (FROG) for measuring complex ultrashort laser pulses, a new method for measuring the arbitrary polarization state of an ultrashort laser pulse using Tomographic Ultrafast Retrieval of Transverse Light E-fields (TURTLE) technique, and new approach for measuring two complex pulses simultaneously using PG blind FROG. In recent decades, many techniques for measuring the full intensity and phase of ultrashort laser pulses have been proposed. These techniques include: Spectral Interferometry (SI)[1], Temporal Analysis by Dispersing a Pair of Light E-Field (TADPOLE)[2], Spectral Phase Interferometry for direct electric-field reconstruction (SPIDER)[3], and Frequency-Resolved Optical Gating (FROG)[4]. Each technique is actually a class of techniques that includes different variations on the original idea, such as SEA-SPIDER[5], ZAP SPIDER[6] are two variations of SPIDER. But most of these techniques for measuring ultrashort laser pulses either do not yield the complete time-dependent intensity and phase (e.g., autocorrelation), can at best only measure simple pulses (e.g., SPIDER), or need well characterized reference pulse. In this thesis, we compare the performance of three versions of FROG: second-harmonic-generation (SHG) FROG, polarization-gate (PG) FROG, and cross-correlation FROG (XFROG), the last of which requires a well-characterized reference pulse. We found that the XFROG algorithm converged in all cases and required only one initial guess. The PG FROG algorithm converged for 99% of the moderately complex pulses that we tried, and for over 95% of the most complex pulses (TBP ˜ 100). And the SHG FROG algorithm converged for 95% of the pulses that we tried and for over 80% of the most complex pulses. After some analysis, we found that noise filtering and adding more sampling points to the FROG trace solved the non-converging problems and we

  13. Simultaneous measurement of two ultrashort laser pulses from a single spectrogram in a single shot

    SciTech Connect

    Kane, D.J.; Rodriguez, G.; Taylor, A.J.; Clement, T.S. ||

    1997-04-01

    Frequency-resolved optical gating (FROG) is a technique that produces a spectrogram of an ultrashort laser pulse. The intensity and phase of the ultrashort laser pulse can be determined through solving for the phase of the spectrogram with an iterative, phase-retrieval algorithm. This work presents a new phase-retrieval algorithm that retrieves both the probe and the gate pulses independently by converting the FROG phase-retrieval problem to an eigenvector problem. The new algorithm is robust and general. It is tested theoretically by use of synthetic data sets and experimentally by use of single-shot, polarization-gate FROG. We independently and simultaneously characterize the electric field amplitude and phase of a pulse (probe) that was passed though 200 mm of BK7 glass and the amplitude of an unchanged pulse (gate) from an amplified Ti:sapphire laser. When the effect of the 200 mm of BK7 glass was removed mathematically from the probe, there was good agreement between the measured gate and the calculated, prechirped probe. {copyright} 1997 Optical Society of America

  14. Lasers for ultrashort light pulses

    SciTech Connect

    Herrmann, J.; Wilhelmi, B.

    1987-01-01

    The present rapid expansion of research work on picosecond lasers and their application makes it difficult to survey and comprehend the large number of publications in this field. This book aims to provide an introduction to the field starting with the very basic and moving on to an advanced level. Contents: Fundamentals of the interaction between light pulses and matter; Fundamentals of lasers for ultrashort light pulses; Methods of measurement; Active modelocking; Synchronously pumped lasers; Passive modelocking of dye lasers; Passive modelocking of solid state lasers; Nonstationary nonlinear optical processes; Ultrafast spectroscopy.

  15. Autocorrelation measurement of an ultra-short optical pulse using an electrically focus-tunable lens

    NASA Astrophysics Data System (ADS)

    Serna, Juan; Hamad, Abdullatif; Rueda, Edgar; Garcia, Hernando

    2015-10-01

    In this communication, a novel technique to measure the temporal width of an ultra-short optical pulse using an electrically focus-tunable lens (EFTL) is proposed and implemented (no need for a mechanical translation stage). The principle is based on the time delay experienced by the pulse when it passes through the deformed membrane of the EFTL as the focal length changes by an applied current. The resolution of the system is approximately 0.23 fs, with a total time delay of 0.69 ps. A typical autocorrelation can be performed in less than 5 s with an excellent Signal to Noise Ratio. The same technique can be implemented to study ultrafast phenomena like electronic relaxation or ultrafast fluorescence in a pump-probe configuration.

  16. Ultrashort-pulse measurement using noninstantaneous nonlinearities: Raman effects in frequency-resolved optical gating

    SciTech Connect

    DeLong, K.W.; Ladera, C.L.; Trebino, R.; Kohler, B.; Wilson, K.R.

    1995-03-01

    Ultrashort-pulse-characterization techniques generally require instantaneously responding media. We show that this is not the case for frequency-resolved optical gating (FROG). We include, as an example, the noninstantaneous Raman response of fused silica, which can cause errors in the retrieved pulse width of as much as 8% for a 25-fs pulse in polarization-gate FROG. We present a modified pulse-retrieval algorithm that deconvolves such slow effects and use it to retrieve pulses of any width. In experiments with 45-fs pulses this algorithm achieved better convergence and yielded a shorter pulse than previous FROG algorithms.

  17. Noise sensitivity in frequency-resolved optical-gating measurements of ultrashort pulses

    SciTech Connect

    Fittinghoff, D.N.; DeLong, K.W.; Trebino, R.; Ladera, C.L.

    1995-10-01

    Frequency-resolved optical gating (FROG), a technique for measuring ultrashort laser pulses, involves producing a spectrogram of the pulse and then retrieving the pulse intensity and phase with an iterative algorithm. We study how several types of noise---multiplicative, additive, and quantization---affect pulse retrieval. We define a convergence criterion and find that the algorithm converges to a reasonable pulse field, even in the presence of 10% noise. Specifically, with appropriate filtering, 1% rms retrieval error is achieved for 10% multiplicative noise, 10% additive noise, and as few as 8 bits of resolution. For additive and multiplicative noise the retrieval errors decrease roughly as the square root of the amount of noise. In addition, the background induced in the wings of the pulse by additive noise is equal to the amount of additive noise on the trace. Thus the dynamic range of the measured intensity and phase is limited by a noise floor equal to the amount of additive noise on the trace. We also find that, for best results, a region of zero intensity should surround the nonzero region of the trace. Consequently, in the presence of additive noise, baseline subtraction is important. We also find that Fourier low-pass filtering improves pulse retrieval without introducing significant distortion, especially in high-noise cases. We show that the field errors in the temporal and the spectral domains are equal. Overall, the algorithm performs well because the measured trace contains {ital N}{sup 2} data points for a pulse that has only 2{ital N} degrees of freedom; FROG has built in redundancy. {copyright} {ital 1995} {ital Optical} {ital Society} {ital of} {ital America}.

  18. Practical issues in ultrashort-laser-pulse measurement using frequency-resolved optical gating

    SciTech Connect

    DeLong, K.W.; Fittinghoff, D.N.; Trebino, R.

    1996-07-01

    The authors explore several practical experimental issues in measuring ultrashort laser pulses using the technique of frequency-resolved optical gating (FROG). They present a simple method for checking the consistency of experimentally measured FROG data with the independently measured spectrum and autocorrelation of the pulse. This method is a powerful way of discovering systematic errors in FROG experiments. They show how to determine the optimum sampling rate for FROG and show that this satisfies the Nyquist criterion for the laser pulse. They explore the low- and high-power limits to FROG and determine that femtojoule operation should be possible, while the effects of self-phase modulation limit the highest signal efficiency in FROG to 1%. They also show quantitatively that the temporal blurring due to a finite-thickness medium in single-shot geometries does not strongly limit the FROG technique. They explore the limiting time-bandwidth values that can be represented on a FROG trace of a given size. Finally, they report on a new measure of the FROG error that improves convergence in the presence of noise.

  19. A novel measurement scheme for the radial group delay of large-aperture ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Wu, Fenxiang; Xu, Yi; Li, Zhaoyang; Li, Wenkai; Lu, Jun; Wang, Cheng; Li, Yanyan; Liu, Yanqi; Lu, Xiaoming; Peng, Yujie; Wang, Ding; Leng, Yuxin; Li, Ruxin

    2016-05-01

    In femtosecond high-peak-power laser system, the radial group delay (RGD) of the pulse front introduced by conventional lens-based beam expanders can significantly decrease the achievable focal intensity, especially when it is larger than the pulse duration. In order to quantitatively analyze and compensate the RGD, a novel measurement scheme based on self-reference and second-order cross-correlation technology is proposed and applied to measure the RGD of the large-aperture ultra-short laser pulses directly. The measured result of the RGD in a 200 TW Ti:sapphire laser system is in good agreement with the theoretical calculation. To our knowledge, it is the first time to realize the direct RGD measurement of large-aperture ultra-short laser pulses.

  20. Ultrashort-pulse lasers machining

    SciTech Connect

    Banks, P S; Feit, M D; Nguyen, H T; Perry, M D, Stuart, B C

    1999-01-22

    A new type of material processing is enabled with ultrashort (t < 10 psec) laser pulses. Cutting, drilling, sculpting of all materials (biologic materials, ceramics, sapphire, silicon carbide, diamond, metals) occurs by new mechanisms which eliminate thermal shock or collateral damage. High precision machining to submicron tolerances is enabled resulting in high surface quality and negligible heat affected zone.

  1. Ultrashort-pulse laser machining

    SciTech Connect

    Banks, P S; Feit, M D; Nguyen, H T; Perry, M D; Rubenchik, A M; Sefcik, J A; Stuart, B C

    1998-09-01

    A new type of material processing is enabled with ultrashort (t < 10 ps) laser pulses. Cutting, drilling, sculpting of all materials (biologic materials, ceramics, sapphire, silicon carbide, diamond, metals) occurs by new mechanisms that eliminate thermal shock or collateral damage. High-precision machining to submicron tolerances is enabled resulting in high surface quality and negligible heat affected zone.

  2. Method and apparatus for measuring the intensity and phase of an ultrashort light pulse

    DOEpatents

    Kane, Daniel J.; Trebino, Rick P.

    1998-01-01

    The pulse shape I(t) and phase evolution x(t) of ultrashort light pulses are obtained using an instantaneously responding nonlinear optical medium to form a signal pulse. A light pulse, such a laser pulse, is split into a gate pulse and a probe pulse, where the gate pulse is delayed relative to the probe pulse. The gate pulse and the probe pulse are combined within an instantaneously responding optical medium to form a signal pulse functionally related to a temporal slice of the gate pulse corresponding to the time delay of the probe pulse. The signal pulse is then input to a wavelength-selective device to output pulse field information comprising intensity vs. frequency for a first value of the time delay. The time delay is varied over a range of values effective to yield an intensity plot of signal intensity vs. wavelength and delay. In one embodiment, the beams are overlapped at an angle so that a selected range of delay times is within the intersection to produce a simultaneous output over the time delays of interest.

  3. Measurement of edge density profiles of Large Helical Device plasmas using an ultrashort-pulse reflectometer.

    PubMed

    Yokota, Y; Mase, A; Kogi, Y; Bruskin, L G; Tokuzawa, T; Kawahata, K

    2008-05-01

    We report here on the application of an ultrashort-pulse reflectometer (USPR) to Large Helical Device in National Institute for Fusion Science. An impulse with picosecond pulse width is used as a source in an USPR. Since the bandwidth of a source is inversely related to the pulse width, we can utilize the frequency range of microwave to millimeter-wave by using wide band transmission lines. The density profiles can be reconstructed by collecting time-of-flight signal of each frequency component of an impulse reflected from each cutoff layer. Remote control system using super science information network has been introduced to the present USPR system. PMID:18513099

  4. Ultra-short pulse generator

    DOEpatents

    McEwan, T.E.

    1993-12-28

    An inexpensive pulse generating circuit is disclosed that generates ultra-short, 200 picosecond, and high voltage 100 kW, pulses suitable for wideband radar and other wideband applications. The circuit implements a nonlinear transmission line with series inductors and variable capacitors coupled to ground made from reverse biased diodes to sharpen and increase the amplitude of a high-voltage power MOSFET driver input pulse until it causes non-destructive transit time breakdown in a final avalanche shock wave diode, which increases and sharpens the pulse even more. 5 figures.

  5. Ultra-short pulse generator

    DOEpatents

    McEwan, Thomas E.

    1993-01-01

    An inexpensive pulse generating circuit is disclosed that generates ultra-short, 200 picosecond, and high voltage 100 kW, pulses suitable for wideband radar and other wideband applications. The circuit implements a nonlinear transmission line with series inductors and variable capacitors coupled to ground made from reverse biased diodes to sharpen and increase the amplitude of a high-voltage power MOSFET driver input pulse until it causes non-destructive transit time breakdown in a final avalanche shockwave diode, which increases and sharpens the pulse even more.

  6. Ultrashort X-ray pulse science

    SciTech Connect

    Chin, Alan Hap

    1998-05-01

    A variety of phenomena involves atomic motion on the femtosecond time-scale. These phenomena have been studied using ultrashort optical pulses, which indirectly probe atomic positions through changes in optical properties. Because x-rays can more directly probe atomic positions, ultrashort x-ray pulses are better suited for the study of ultrafast structural dynamics. One approach towards generating ultrashort x-ray pulses is by 90{sup o} Thomson scattering between terawatt laser pulses and relativistic electrons. Using this technique, the author generated {approx} 300 fs, 30 keV (0.4 {angstrom}) x-ray pulses. These x-ray pulses are absolutely synchronized with ultrashort laser pulses, allowing femtosecond optical pump/x-ray probe experiments to be performed. Using the right-angle Thomson scattering x-ray source, the author performed time-resolved x-ray diffraction studies of laser-perturbated InSb. These experiments revealed a delayed onset of lattice expansion. This delay is due to the energy relaxation from a dense electron-hole plasma to the lattice. The dense electron-hole plasma first undergoes Auger recombination, which reduces the carrier concentration while maintaining energy content. Longitudinal-optic (LO) phonon emission then couples energy to the lattice. LO phonon decay into acoustic phonons, and acoustic phonon propagation then causes the growth of a thermally expanded layer. Source characterization is instrumental in utilizing ultrashort x-ray pulses in time-resolved x-ray spectroscopies. By measurement of the electron beam diameter at the generation point, the pulse duration of the Thomson scattered x-rays is determined. Analysis of the Thomson scattered x-ray beam properties also provides a novel means of electron bunch characterization. Although the pulse duration is inferred for the Thomson scattering x-ray source, direct measurement is required for other x-ray pulse sources. A method based on the laser-assisted photoelectric effect (LAPE) has

  7. Method and apparatus for measuring the intensity and phase of one or more ultrashort light pulses and for measuring optical properties of materials

    DOEpatents

    Trebino, Rick P.; DeLong, Kenneth W.

    1996-01-01

    The intensity and phase of one or more ultrashort light pulses are obtained using a non-linear optical medium. Information derived from the light pulses is also used to measure optical properties of materials. Various retrieval techniques are employed. Both "instantaneously" and "non-instantaneously" responding optical mediums may be used.

  8. Ultrashort-pulse laser calligraphy

    NASA Astrophysics Data System (ADS)

    Yang, Weijia; Kazansky, Peter G.; Shimotsuma, Yasuhiko; Sakakura, Masaaki; Miura, Kiyotaka; Hirao, Kazuyuki

    2008-10-01

    Control of structural modifications inside silica glass by changing the front tilt of an ultrashort pulse is demonstrated, achieving a calligraphic style of laser writing. The phenomena of anisotropic bubble formation at the boundary of an irradiated region and modification transition from microscopic bubbles formation to self-assembled form birefringence are observed, and the physical mechanisms are discussed. The results provide the comprehensive evidence that the light beam with centrosymmetric intensity distribution can produce noncentrosymmetric material modifications.

  9. Focal spot measurement in ultra-intense ultra-short pulse laser facility

    NASA Astrophysics Data System (ADS)

    Liu, Lanqin; Peng, Hansheng; Zhou, Kainan; Wang, Xiaodong; Wang, Xiao; Zeng, Xiaoming; Zhu, Qihua; Huang, Xiaojun; Wei, Xiaofeng; Ren, Huan

    2005-06-01

    A peak power of 286-TW Ti:sapphire laser facility referred to as SILEX-I was successfully built at China Academy of Engineering Physics, for a pulse duration of 30 fs in a three-stage Ti:sapphire amplifier chain based on chirped-pulse amplification. The beam have a wavefront distortion of 0.63μm PV and 0.09μm RMS, and the focal spot with an f/2.2 OAP is 5.7μm, to our knowledge, this is the best far field obtained for high-power ultra-short pulse laser systems with no deformable mirror wavefront correction. The peak focused intensity of ~1021W /cm2 were expected.

  10. Ultrashort pulsed neutron source.

    PubMed

    Pomerantz, I; McCary, E; Meadows, A R; Arefiev, A; Bernstein, A C; Chester, C; Cortez, J; Donovan, M E; Dyer, G; Gaul, E W; Hamilton, D; Kuk, D; Lestrade, A C; Wang, C; Ditmire, T; Hegelich, B M

    2014-10-31

    We report on a novel compact laser-driven neutron source with an unprecedented short pulse duration (<50  ps) and high peak flux (>10(18)  n/cm(2)/s), an order of magnitude higher than any existing source. In our experiments, high-energy electron jets are generated from thin (<3  μm) plastic targets irradiated by a petawatt laser. These intense electron beams are employed to generate neutrons from a metal converter. Our method opens venues for enhancing neutron radiography contrast and for creating astrophysical conditions of heavy element synthesis in the laboratory. PMID:25396373

  11. Ultrashort Pulsed Neutron Source

    NASA Astrophysics Data System (ADS)

    Pomerantz, I.; McCary, E.; Meadows, A. R.; Arefiev, A.; Bernstein, A. C.; Chester, C.; Cortez, J.; Donovan, M. E.; Dyer, G.; Gaul, E. W.; Hamilton, D.; Kuk, D.; Lestrade, A. C.; Wang, C.; Ditmire, T.; Hegelich, B. M.

    2014-10-01

    We report on a novel compact laser-driven neutron source with an unprecedented short pulse duration (<50 ps ) and high peak flux (>1018 n /cm2/s ), an order of magnitude higher than any existing source. In our experiments, high-energy electron jets are generated from thin (<3 μ m ) plastic targets irradiated by a petawatt laser. These intense electron beams are employed to generate neutrons from a metal converter. Our method opens venues for enhancing neutron radiography contrast and for creating astrophysical conditions of heavy element synthesis in the laboratory.

  12. Single-shot temporal envelope measurement of ultrashort extreme-UV pulses by spatially encoded transmission gating.

    PubMed

    Chu, Hsu-hsin; Yang, Chi-Hsiang; Liu, Shih-Cheng; Wang, Jyhpyng

    2015-12-28

    Single-shot ultrashort extreme-UV(EUV) pulse waveform measurement is demonstrated by utilizing strong field ionization of H2 gas for transmission gating. A cross-propagating intense near-IR gate pulse ionizes the EUV absorbing H2 molecules into EUV-non-absorbing H2++ (two protons) and creates a time sweep of transmission encoded spatially across the EUV pulse. The temporal envelope is then retrieved from the lopsided spatial profile of the transmitted pulse. This method not only measures EUV temporal envelope for each single shot, but also determines timing jitter and envelope fluctuation statistically, thus is particularly useful for characterizing low-repetition-rate fluctuating EUV/soft x-ray sources. PMID:26832064

  13. Using phase retrieval to measure the intensity and phase of ultrashort pulses: Frequency-resolved optical gating

    SciTech Connect

    Trebino, R. ); Kane, D.J. )

    1993-05-01

    The authors recently introduced a new technique, frequency-resolved optical gating (FROG). For directly determining the full intensity I(t) and phase [var phi](t) of a single femtosecond pulse. By using almost any instantaneous nonlinear-optical interaction of two replicas of the ultrashort pulse to be measured, FROG involves measuring the spectrum of the signal pulse as a function of the delay between the replicas. The resulting trace of intensity versus frequency and delay yields an intuitive display of the pulse that is similar to the pulse spectrogram, except that the gate is a function of the pulse to be measured. The problem of inverting the FROG trace to obtain the pulse intensity and phase can also be considered a complex two-dimensional phase-retrieval problem. As a result, the FROG trace yields, in principle, an essentially unique pulse intensity and phase. It is shown that this is also the case in practice. An iterative-Fourier-transform algorithm is presented for inverting the FROG trace. The algorithm is unusual in its use of a novel constraint: the mathematical form of the signal field. Without the use of a support constraint, the algorithm performs quite well in practice, even for pulses with serious phase distortions and for experimental data with noise, although it occasionally stagnates when pulses with large intensity fluctuations are used. 49 refs., 15 figs.

  14. Ultrashort Laser Pulses in Physics and Chemistry

    SciTech Connect

    Naskrecki, Ryszard

    2007-11-26

    Study of physical and chemical events accompanying light-matter interaction in pico- and femtosecond time scale have become possible with the use of ultrashort laser pulses. With the progress in generation of ultrashort laser pulses, the ultrafast optical spectroscopy, as a tool for dynamic study, is still evolving rapidly.

  15. Measuring the intensity and phase of two ultrashort pulses on a single shot

    SciTech Connect

    DeLong, K.W.; Trebino, R.

    1994-12-31

    The method of Frequency-Resolved Optical Gating (FROG) allows one to measure the amplitude and phase of an arbitrary femtosecond pulse on a single laser shot. An extension of this method, which they call Twin Recovery of Excitation E-fields using FROG (TREEFROG) allows one to measure two separate laser pulses. The two dissimilar pulses are used to generate a single ``TREEFROG trace`` from a simple experimental apparatus, and the two pulse electric fields are determined using a modified FROG pulse-retrieval algorithm.

  16. Unstable multipulsing can be invisible to some ultrashort pulse measurement techniques

    NASA Astrophysics Data System (ADS)

    Rhodes, Michelle; Guang, Zhe; Trebino, Rick

    2016-03-01

    Multiple pulsing is a feature of most mode-locked ultrafast laser systems at very high pump powers, and slight variations in the pump power around certain regimes can cause sinusoidally-varying or even chaotic separations among pulses. The impact of this type of unstable multipulsing on modern pulse measurement methods has not been studied. We have performed calculations and simulations and find that allowing only the relative phase of a satellite pulse to vary causes the satellite to wash out of the SPIDER measurement completely. Although techniques like FROG and autocorrelation cannot accurately determine the precise properties of satellite pulses, they do succeed in seeing them.

  17. Generation and measurement of ultrashort pulses from the Stanford Superconducting Accelerator free-electron laser

    SciTech Connect

    Richman, B.A.; DeLong, K.W.; Trebino, R.

    1995-11-01

    The authors present results of frequency resolved optical gating (FROG) measurements on the Superconducting Accelerator (SCA) mid-IR free-electron laser (FEL) at Stanford. FROG retrieves complete amplitude and phase content of an optical pulse. First, they review the properties of FELs including the ability to tune wavelength and pulse length. In addition, the electron beam driving the FEL often affects the optical pulse shape. The SCA mid-IR FEL currently operates at wavelengths between 4 {micro}m and 10 {micro}m and its pulse length can be varied from 700 fs to 2 ps. They then describe details of the experimental layout and procedures particular to FELs and to the mid-IR. Finally, they show FROG measurements on the FEL including examples of nearly transform limited pulses, frequency chirped pulses, and pulses distorted by atmospheric water vapor absorption.

  18. Distortion of ultrashort pulses caused by aberrations

    NASA Astrophysics Data System (ADS)

    Horváth, Z. L.; Kovács, A. P.; Bor, Zs.

    The effect of the primary wave aberrations (spherical aberration, astigmatism and coma) on ultrashort pulses is studied by the Nijboer-Zernike theory. The results of the geometrical and the wave optical treatments are compared.

  19. Effect of Orbital Angular Momentum on Nondiffracting Ultrashort Optical Pulses

    NASA Astrophysics Data System (ADS)

    Ornigotti, Marco; Conti, Claudio; Szameit, Alexander

    2015-09-01

    We introduce a new class of nondiffracting optical pulses possessing orbital angular momentum. By generalizing the X -wave solution of the Maxwell equation, we discover the coupling between angular momentum and the temporal degrees of freedom of ultrashort pulses. The spatial twist of propagation invariant light pulse turns out to be directly related to the number of optical cycles. Our results may trigger the development of novel multilevel classical and quantum transmission channels free of dispersion and diffraction. They may also find application in the manipulation of nanostructured objects by ultrashort pulses and for novel approaches to the spatiotemporal measurements in ultrafast photonics.

  20. Effect of Orbital Angular Momentum on Nondiffracting Ultrashort Optical Pulses.

    PubMed

    Ornigotti, Marco; Conti, Claudio; Szameit, Alexander

    2015-09-01

    We introduce a new class of nondiffracting optical pulses possessing orbital angular momentum. By generalizing the X-wave solution of the Maxwell equation, we discover the coupling between angular momentum and the temporal degrees of freedom of ultrashort pulses. The spatial twist of propagation invariant light pulse turns out to be directly related to the number of optical cycles. Our results may trigger the development of novel multilevel classical and quantum transmission channels free of dispersion and diffraction. They may also find application in the manipulation of nanostructured objects by ultrashort pulses and for novel approaches to the spatiotemporal measurements in ultrafast photonics. PMID:26382668

  1. Characterization of partially coherent ultrashort XUV pulses

    NASA Astrophysics Data System (ADS)

    Bourassin-Bouchet, Charles; Couprie, Marie-Emmanuelle

    2015-05-01

    Modern ultrafast metrology relies on the postulate that the pulse to be measured is fully coherent, i.e. that it can be completely described by its spectrum and spectral phase. However, synthesizing fully coherent pulses is not always possible in practice, especially in the domain of emerging ultrashort X-ray sources where temporal metrology is strongly needed. As an example, the lack of longitudinal coherence, that is shot-to-shot fluctuations, of Free-Electron Lasers (FEL) has prevented so far their full amplitude and phase temporal characterization. To sort out this issue, we have adapted Frequency-Resolved Optical Gating (FROG), the first and one of the most widespread techniques for pulse characterization, to enable the measurement of partially coherent XUV pulses even down to the attosecond timescale. Especially, this technique allows one to overcome the sources of decoherence that normally prevent a pulse measurement, such as the spectrometer resolution or the presence of XUV/laser arrival time jitter.

  2. Ultrashort Laguerre-Gaussian pulses with angular and group velocity dispersion compensation.

    PubMed

    Zeylikovich, I; Sztul, H I; Kartazaev, V; Le, T; Alfano, R R

    2007-07-15

    Coherent optical vortices are generated from ultrashort 6.4 fs pulses. Our results demonstrate angular dispersion compensation of ultrashort 6.4 fs Laguerre-Gaussian (LG) pulses as well as what is believed to be the first direct autocorrelation measurement of 80 fs LG amplified pulses. A reflective-mirror-based 4f-compressor is proposed to compensate the angular and group velocity dispersion of the ultrashort LG pulses. PMID:17632631

  3. BBO crystal component design for ultra-short laser pulse measurement

    NASA Astrophysics Data System (ADS)

    Jia, Yudong; Zhang, Xiaoqing; Zhang, Tianyi; Lu, Lingling

    2014-09-01

    In this paper the mechanism of BBO crystal component for frequency resolved optical gating technique has been researched by mathematical modeling and Simulation. Research shows that thickness of the crystal and the phase matching angle are important parameters affecting the measurement performance. Crystal thickness determines the pulse width limit which this crystal can distinguish; when the phase condition is matched between the fundamental frequency and second-harmonic of light, the SHG efficiency of incident light is highest. According to the calculations, An BBO crystals with 3.5mm thickness, 20.56 degrees phase matching angle is adopted to realize the crystal component for tens to hundreds of femtoseconds pulse width measurement.

  4. Compact And Robust Laser Impulse Measurement Device, With Ultrashort Pulse Laser Ablation Results

    NASA Astrophysics Data System (ADS)

    Kremeyer, Kevin; Lapeyre, John; Hamann, Steven

    2008-04-01

    An impulse measurement device and analysis package was conceived, designed, constructed, tested, and demonstrated to be capable of: measuring nanoNewton-seconds to milliNewton-seconds of impulse due to laser-ablation; being transported as carry-on baggage; set-up and tear-down times of less than an hour; target exchange times of less than two minutes (targets can be ablated at multiple positions for thousands of shots); measurements in air and in vacuum; error of just a few percent; repeatability over a wide range of potential systematic error sources; and time between measurements, including ring-down and analysis, of less than 30 seconds. The instrument consists of a cantilever (i.e. leaf spring), whose time-dependent displacement/oscillation is measured and analyzed to determine the impulse imparted by a laser pulse to a target. These shapes are readily/commercially available, and any target material can be used, provided it can be fashioned in the form of a cantilever, or as a coating/film/tape, suitable for mounting on a cantilever of known geometry. The instrument was calibrated both statically and dynamically, and measurements were performed on brass, steel, and Aluminum, using laser pulses of ˜7 ns, ˜500 ps, and ˜500 fs. The results agree well with those published in the literature, with surface effects, atmosphere, and pre-/post-pulses demonstrating interesting effects and indicating areas for further study. These parameters should be carefully controlled and held constant during a series of measurements. The impulse imparted by ablation due to laser filaments in air was also explored.

  5. Spectral superresolution with ultrashort optical pulses.

    PubMed

    Berger, Naum K

    2012-01-10

    A superresolution technique for the measurement of transmission, reflection, and absorption spectra is proposed. An ultrashort laser pulse is propagated in a dispersive element and then periodically phase modulated. The temporal modulation is transformed into periodic spectral modulation, for which the number of harmonics, 2M+1, is determined by the modulation index. The modulated pulse is transmitted through (reflected from) the sample to be tested and measured by a spectrometer. By performing 2M+1 measurements for 2M+1 delays between the dispersed pulse and modulation signal, one can restore the spectral response of the sample with superresolution after simple processing. We numerically demonstrate the measurement of the transmission spectrum of an ultranarrow optical filter with a minimum feature of 0.43 pm by an optical spectrum analyzer with a 10 pm resolution. A twentyfold enhancement of the resolution is achieved in the presence of noise with a level of 0.1%. The advantage of the system is its full reconfigurability. PMID:22270515

  6. Nanopore formation in neuroblastoma cells following ultrashort electric pulse exposure

    NASA Astrophysics Data System (ADS)

    Roth, Caleb C.; Payne, Jason A.; Wilmink, Gerald J.; Ibey, Bennett L.

    2011-03-01

    Ultrashort or nanosecond electrical pulses (USEP) cause repairable damage to the plasma membranes of cells through formation of nanopores. These nanopores are able to pass small ions such as sodium, calcium, and potassium, but remain impermeable to larger molecules like trypan blue and propidium iodide. What remains uncertain is whether generation of nanopores by ultrashort electrical pulses can inhibit action potentials in excitable cells. In this paper, we explored the sensitivity of excitable cells to USEP using Calcium Green AM 1 ester fluorescence to measure calcium uptake indicative of nanopore formation in the plasma membrane. We determined the threshold for nanopore formation in neuroblastoma cells for three pulse parameters (amplitude, pulse width, and pulse number). Measurement of such thresholds will guide future studies to determine if USEP can inhibit action potentials without causing irreversible membrane damage.

  7. Ultrashort pulse chirp measurement via transverse second-harmonic generation in strontium barium niobate crystal

    SciTech Connect

    Trull, J.; Wang, B.; Parra, A.; Vilaseca, R.; Cojocaru, C.; Sola, I.; Sheng, Y.

    2015-06-01

    Pulse compression in dispersive strontium barium niobate crystal with a random size and distribution of the anti-parallel orientated nonlinear domains is observed via transverse second harmonic generation. The dependence of the transverse width of the second harmonic trace along the propagation direction allows for the determination of the initial chirp and duration of pulses in the femtosecond regime. This technique permits a real-time analysis of the pulse evolution and facilitates fast in-situ correction of pulse chirp acquired in the propagation through an optical system.

  8. Fundamentals and industrial applications of ultrashort pulsed lasers at Bosch

    NASA Astrophysics Data System (ADS)

    König, Jens; Bauer, Thorsten

    2011-03-01

    Fundamental results of ablation processes of metals with ultrashort laser pulses in the far threshold fluence regime are shown and discussed. Time-resolved measurements of the plasma transmission exhibit two distinctive minima. The minima occurring within the first nanoseconds can be attributed to electrons and sublimated material emitted from the target surface, whereas the subsequent minimum after several 10 ns is due to particles and droplets after a thermal boiling process. Industrial applications of ultrashort pulsed laser micro machining in the Bosch Group are also shown with the production of exhaust gas sensors and common rail diesel systems. Since 2007, ultrashort laser pulses are used at the BOSCH plant in Bamberg for producing lambda-probes, which are made of a special ceramic layer system and can measure the exhaust gas properties faster and more accurately. This enables further reduction of emissions by optimized combustion control. Since 2009, BOSCH uses ultrashort pulsed lasers for micro-structuring the injector of common rail diesel systems. A drainage groove allows a tight system even at increased pressures up to 2000 bar. Diesel injection is thus even more reliable, powerful and environment-friendly.

  9. New methods of generation of ultrashort laser pulses for ranging

    NASA Technical Reports Server (NTRS)

    Jelinkova, Helena; Hamal, Karel; Kubecek, V.; Prochazka, Ivan

    1993-01-01

    To reach the millimeter satellite laser ranging accuracy, the goal for nineties, new laser ranging techniques have to be applied. To increase the laser ranging precision, the application of the ultrashort laser pulses in connection with the new signal detection and processing techniques, is inevitable. The two wavelength laser ranging is one of the ways to measure the atmospheric dispersion to improve the existing atmospheric correction models and hence, to increase the overall system ranging accuracy to the desired value. We are presenting a review of several nonstandard techniques of ultrashort laser pulses generation, which may be utilized for laser ranging: compression of the nanosecond pulses using stimulated Brillouin and Raman backscattering; compression of the mode-locked pulses using Raman backscattering; passive mode-locking technique with nonlinear mirror; and passive mode-locking technique with the negative feedback.

  10. Neuromuscular disruption with ultrashort electrical pulses

    NASA Astrophysics Data System (ADS)

    Pakhomov, Andrei; Kolb, Juergen F.; Joshi, Ravindra P.; Schoenbach, Karl H.; Dayton, Thomas; Comeaux, James; Ashmore, John; Beason, Charles

    2006-05-01

    Experimental studies on single cells have shown that application of pulsed voltages, with submicrosecond pulse duration and an electric field on the order of 10 kV/cm, causes sudden alterations in the intracellular free calcium concentration, followed by immobilization of the cell. In order to examine electrical stimulation and incapacitation with such ultrashort pulses, experiments on anesthetized rats have been performed. The effect of single, 450 nanosecond monopolar pulses have been compared with that of single pulses with multi-microsecond duration (TASER pulses). Two conditions were explored: 1. the ability to elicit a muscle twitch, and, 2. the ability to suppress voluntary movement by using nanosecond pulses. The second condition is relevant for neuromuscular incapacitation. The preliminary results indicate that for stimulation microsecond pulses are advantageous over nanosecond pulses, whereas for incapacitation, the opposite seems to apply. The stimulation effects seem to scale with electrical charge, whereas the disruption effects don't follow a simple scaling law. The increase in intensity (time of incapacitation) for a given pulse duration, is increasing with electrical energy, but is more efficient for nanosecond than for microsecond pulses. This indicates different cellular mechanisms for incapacitation, most likely subcellular processes, which have been shown to become increasingly important when the pulse duration is shortened into the nanosecond range. If further studies can confirm these initial results, consequences of reduced pulse duration are a reduction in weight and volume of the pulse delivery system, and likely, because of the lower required energy for neuromuscular incapacitation, reduced safety risks.

  11. Compact Sources of Ultrashort Pulses

    NASA Astrophysics Data System (ADS)

    Duling, Irl N., III

    2006-11-01

    List of contributors; Acronyms and abbreviations; Preface; 1. Short pulse generation H. A. Haus; 2. Passive modelocking in solid state lasers Thomas Brabec, Stephen M. J. Kelly and Ferenc Krausz; 3. Compact modelocked solid state lasers pumped by laser diodes John R. M. Barr; 4. Modelocking of all-fiber lasers Irl N. Duling, III and Michael L. Dennis; 5. Nonlinear polarization evolution in passively modelocked fiber lasers Martin E. Fermann; 6. Ultrafast vertical cavity semiconductor lasers Wenbin Jiang and John Bowers; 7. High power ultrafast semiconductor for injection diode lasers Peter J. Delfyett; 8. The hybrid soliton pulse source Paul A. Morton; 9. Monolithic colliding pulse modelocked diode lasers Ming C. Wu and Young-Kai Chen; Index.

  12. High power ultrashort pulse lasers

    SciTech Connect

    Perry, M.D.

    1994-10-07

    Small scale terawatt and soon even petawatt (1000 terawatt) class laser systems are made possible by application of the chirped-pulse amplification technique to solid-state lasers combined with the availability of broad bandwidth materials. These lasers make possible a new class of high gradient accelerators based on the large electric fields associated with intense laser-plasma interactions or from the intense laser field directly. Here, we concentrate on the laser technology to produce these intense pulses. Application of the smallest of these systems to the production of high brightness electron sources is also introduced.

  13. The time resolved measurement of ultrashort terahertz-band electric fields without an ultrashort probe

    NASA Astrophysics Data System (ADS)

    Walsh, D. A.; Snedden, E. W.; Jamison, S. P.

    2015-05-01

    The time-resolved detection of ultrashort pulsed THz-band electric field temporal profiles without an ultrashort laser probe is demonstrated. A non-linear interaction between a narrow-bandwidth optical probe and the THz pulse transposes the THz spectral intensity and phase information to the optical region, thereby generating an optical pulse whose temporal electric field envelope replicates the temporal profile of the real THz electric field. This optical envelope is characterised via an autocorrelation based FROG (frequency resolved optical gating) measurement, hence revealing the THz temporal profile. The combination of a narrow-bandwidth, long duration, optical probe, and self-referenced FROG makes the technique inherently immune to timing jitter between the optical probe and THz pulse and may find particular application where the THz field is not initially generated via ultrashort laser methods, such as the measurement of longitudinal electron bunch profiles in particle accelerators.

  14. The time resolved measurement of ultrashort terahertz-band electric fields without an ultrashort probe

    SciTech Connect

    Walsh, D. A. Snedden, E. W.; Jamison, S. P.

    2015-05-04

    The time-resolved detection of ultrashort pulsed THz-band electric field temporal profiles without an ultrashort laser probe is demonstrated. A non-linear interaction between a narrow-bandwidth optical probe and the THz pulse transposes the THz spectral intensity and phase information to the optical region, thereby generating an optical pulse whose temporal electric field envelope replicates the temporal profile of the real THz electric field. This optical envelope is characterised via an autocorrelation based FROG (frequency resolved optical gating) measurement, hence revealing the THz temporal profile. The combination of a narrow-bandwidth, long duration, optical probe, and self-referenced FROG makes the technique inherently immune to timing jitter between the optical probe and THz pulse and may find particular application where the THz field is not initially generated via ultrashort laser methods, such as the measurement of longitudinal electron bunch profiles in particle accelerators.

  15. Nanoplasmonic generation of ultrashort EUV pulses

    NASA Astrophysics Data System (ADS)

    Choi, Joonhee; Lee, Dong-Hyub; Han, Seunghwoi; Park, In-Yong; Kim, Seungchul; Kim, Seung-Woo

    2012-10-01

    Ultrashort extreme-ultraviolet (EUV) light pulses are an important tool for time-resolved pump-probe spectroscopy to investigate the ultrafast dynamics of electrons in atoms and molecules. Among several methods available to generate ultrashort EUV light pulses, the nonlinear frequency upconversion process of high-harmonic generation (HHG) draws attention as it is capable of producing coherent EUV pulses with precise control of burst timing with respect to the driving near-infrared (NIR) femtosecond laser. In this report, we present and discuss our recent experimental data obtained by the plasmon-driven HHG method that generate EUV radiation by means of plasmonic nano-focusing of NIR femtosecond pulses. For experiment, metallic waveguides having a tapered hole of funnel shape inside were fabricated by adopting the focused-ion-beam process on a micro-cantilever substrate. The plasmonic field formed within the funnelwaveguides being coupled with the incident femtosecond pulse permitted intensity enhancement by a factor of ~350, which creates a hot spot of sub-wavelength size with intensities strong enough for HHG. Experimental results showed that with injection of noble gases into the funnel-waveguides, EUV radiation is generated up to wavelengths of 32 nm and 29.6 nm from Ar and Ne gas atoms, respectively. Further, it was observed that lower-order EUV harmonics are cut off in the HHG spectra by the tiny exit aperture of the funnel-waveguide.

  16. Ophthalmic applications of ultrashort pulsed lasers

    NASA Astrophysics Data System (ADS)

    Juhasz, Tibor; Spooner, Greg; Sacks, Zachary S.; Suarez, Carlos G.; Raksi, Ferenc; Zadoyan, Ruben; Sarayba, Melvin; Kurtz, Ronald M.

    2004-06-01

    Ultrashort laser pulses can be used to create high precision incision in transparent and translucent tissue with minimal damage to adjacent tissue. These performance characteristics meet important surgical requirements in ophthalmology, where femtosecond laser flap creation is becoming a widely used refractive surgery procedure. We summarize clinical findings with femtosecond laser flaps as well as early experiments with other corneal surgical procedures such as corneal transplants. We also review laser-tissue interaction studies in the human sclera and their consequences for the treatment of glaucoma.

  17. Ultrashort-pulse laser generated nanoparticles of energetic materials

    DOEpatents

    Welle, Eric J.; Tappan, Alexander S.; Palmer, Jeremy A.

    2010-08-03

    A process for generating nanoscale particles of energetic materials, such as explosive materials, using ultrashort-pulse laser irradiation. The use of ultrashort laser pulses in embodiments of this invention enables one to generate particles by laser ablation that retain the chemical identity of the starting material while avoiding ignition, deflagration, and detonation of the explosive material.

  18. Ultrashort Pulse Propagation in Nonlinear Dispersive Fibers

    NASA Astrophysics Data System (ADS)

    Agrawal, Govind P.

    Ultrashort optical pulses are often propagated through optical waveguides for a variety of applications including telecommunications and supercontinuum generation [1]. Typically the waveguide is in the form of an optical fiber but it can also be a planar waveguide. The material used to make the waveguide is often silica glass, but other materials such as silicon or chalcogenides have also been used in recent years. What is common to all such materials is they exhibit chromatic dispersion as well as the Kerr nonlinearity. The former makes the refractive index frequency dependent, whereas the latter makes it to depend on the intensity of light propagating through the medium [2]. Both of these effects become more important as optical pulses become shorter and more intense. For pulses not too short (pulse widths > 1 ns) and not too intense (peak powers < 10 mW), the waveguide plays a passive role (except for small optical losses) and acts as a transporter of optical pulses from one place to another, without significantly affecting their shape or spectrum. However, as pulses become shorter and more intense, both the dispersion and the Kerr nonlinearity start to affect the shape and spectrum of an optical pulse during its propagation inside the waveguide. This chapter focuses on silica fibers but similar results are expected for other waveguides made of different materials

  19. Fracture toughness of ultrashort pulse-bonded fused silica

    NASA Astrophysics Data System (ADS)

    Richter, S.; Naumann, F.; Zimmermann, F.; Tünnermann, A.; Nolte, S.

    2016-02-01

    We determined the bond interface strength of ultrashort pulse laser-welded fused silica for different processing parameters. To this end, we used a high repetition rate ultrashort pulse laser system to inscribe parallel welding lines with a specific V-shaped design into optically contacted fused silica samples. Afterward, we applied a micro-chevron test to measure the fracture toughness and surface energy of the laser-inscribed welding seams. We analyzed the influence of different processing parameters such as laser repetition rate and line separation on the fracture toughness and fracture surface energy. Welding the entire surface a fracture toughness of 0.71 {MPa} {m}^{1/2}, about 90 % of the pristine bulk material ({≈ } 0.8 {MPa} {m}^{1/2}), is obtained.

  20. Ceramic dentures manufactured with ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Werelius, Kristian; Weigl, Paul

    2004-06-01

    Conventional manufacturing of individual ceramic dental prosthesis implies a handmade metallic framework, which is then veneered with ceramic layers. In order to manufacture all-ceramic dental prosthesis a CAD/CAM system is necessary due to the three dimensional shaping of high strength ceramics. Most CAD/CAM systems presently grind blocks of ceramic after the construction process in order to create the prosthesis. Using high-strength ceramics, such as Hot Isostatic Pressed (HIP)-zirconia, this is limited to copings. Anatomically shaped fixed dentures have a sculptured surface with small details, which can't be created by existing grinding tools. This procedure is also time consuming and subject to significant loss in mechanical strength and thus reduced survival rate once inserted. Ultra-short laser pulses offer a possibility in machining highly complex sculptured surfaces out of high-strength ceramic with negligible damage to the surface and bulk of the ceramic. In order to determine efficiency, quality and damage, several laser ablation parameters such as pulse duration, pulse energy and ablation strategies were studied. The maximum ablation rate was found using 400 fs at high pulse energies. High pulse energies such as 200μJ were used with low damage in mechanical strength compared to grinding. Due to the limitation of available laser systems in pulse repetition rates and power, the use of special ablation strategies provide a possibility to manufacture fully ceramic dental prosthesis efficiently.

  1. Optical reprogramming with ultrashort femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Uchugonova, Aisada; Breunig, Hans G.; Batista, Ana; König, Karsten

    2015-03-01

    The use of sub-15 femtosecond laser pulses in stem cell research is explored with particular emphasis on the optical reprogramming of somatic cells. The reprogramming of somatic cells into induced pluripotent stem (iPS) cells can be evoked through the ectopic expression of defined transcription factors. Conventional approaches utilize retro/lenti-viruses to deliver genes/transcription factors as well as to facilitate the integration of transcription factors into that of the host genome. However, the use of viruses may result in insertional mutations caused by the random integration of genes and as a result, this may limit the use within clinical applications due to the risk of the formation of cancer. In this study, a new approach is demonstrated in realizing non-viral reprogramming through the use of ultrashort laser pulses, to introduce transcription factors into the cell so as to generate iPS cells.

  2. Ultra-short pulse propagation in complex optical systems.

    PubMed

    Fuchs, Ulrike; Zeitner, Uwe; Tünnermann, Andreas

    2005-05-16

    In application of ultra-short laser pulses the pulse parameters have to be controlled accurately. Hence the manipulation of the propagation behavior of ultra-short pulses requires for specially designed optics. We have developed a tool for the simulation of ultra-short laser pulse propagation through complex real optical systems based on a combination of ray-tracing and wave optical propagation methods. For the practical implementation of the approach two commercially available software packages have been linked together, which are ZEMAX and Virtual Optics Lab. The focussing properties of different lenses will be analyzed and the results are demonstrated. PMID:19495292

  3. Laser system using ultra-short laser pulses

    SciTech Connect

    Dantus, Marcos; Lozovoy, Vadim V.; Comstock, Matthew

    2009-10-27

    A laser system using ultrashort laser pulses is provided. In another aspect of the present invention, the system includes a laser, pulse shaper and detection device. A further aspect of the present invention employs a femtosecond laser and binary pulse shaping (BPS). Still another aspect of the present invention uses a laser beam pulse, a pulse shaper and a SHG crystal.

  4. Ultra-short ion and neutron pulse production

    DOEpatents

    Leung, Ka-Ngo; Barletta, William A.; Kwan, Joe W.

    2006-01-10

    An ion source has an extraction system configured to produce ultra-short ion pulses, i.e. pulses with pulse width of about 1 .mu.s or less, and a neutron source based on the ion source produces correspondingly ultra-short neutron pulses. To form a neutron source, a neutron generating target is positioned to receive an accelerated extracted ion beam from the ion source. To produce the ultra-short ion or neutron pulses, the apertures in the extraction system of the ion source are suitably sized to prevent ion leakage, the electrodes are suitably spaced, and the extraction voltage is controlled. The ion beam current leaving the source is regulated by applying ultra-short voltage pulses of a suitable voltage on the extraction electrode.

  5. Non-collinear spectral coherent combination of ultrashort laser pulses.

    PubMed

    Ionel, Laura; Ursescu, Daniel

    2016-04-01

    Non-collinear spectral coherent combining (NCSCC) of ultrashort pulses is analyzed. 2D modeling of the electromagnetic field is performed in case of NCSCC using two or three pulses with different wavelengths. In the case of two pulses, a potentially unwanted spatio-temporal structure of the field appears, corresponding to spatial and temporal modulation of the pulse. By using NCSCC of three 62 fs long pulses with different spectral composition, such spatial-temporal coupling is eliminated and the combined pulse duration in the focal region drops to less than half. The method is scalable to a large number of ultrashort pulses. PMID:27136998

  6. Dislocation structure produced by an ultrashort shock pulse

    SciTech Connect

    Matsuda, Tomoki Hirose, Akio; Sano, Tomokazu; Arakawa, Kazuto

    2014-11-14

    We found an ultrashort shock pulse driven by a femtosecond laser pulse on iron generates a different dislocation structure than the shock process which is on the nanosecond timescale. The ultrashort shock pulse produces a highly dense dislocation structure that varies by depth. According to transmission electron microscopy, dislocations away from the surface produce microbands via a network structure similar to a long shock process, but unlike a long shock process dislocations near the surface have limited intersections. Considering the dislocation motion during the shock process, the structure near the surface is attributed to the ultrashort shock duration. This approach using an ultrashort shock pulse will lead to understanding the whole process off shock deformation by clarifying the early stage.

  7. Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

    PubMed Central

    Hu, Wenqian; Shin, Yung C.; King, Galen B.

    2012-01-01

    Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a significant role in laser-material interaction, especially in the air environment1-11. Early plasma evolution has been captured through pump-probe shadowgraphy1-3 and interferometry1,4-7. However, the studied time frames and applied laser parameter ranges are limited. For example, direct examinations of plasma front locations and electron number densities within a delay time of 100 picosecond (ps) with respect to the laser pulse peak are still very few, especially for the ultrashort pulse of a duration around 100 femtosecond (fs) and a low power density around 1014 W/cm2. Early plasma generated under these conditions has only been captured recently with high temporal and spatial resolutions12. The detailed setup strategy and procedures of this high precision measurement will be illustrated in this paper. The rationale of the measurement is optical pump-probe shadowgraphy: one ultrashort laser pulse is split to a pump pulse and a probe pulse, while the delay time between them can be adjusted by changing their beam path lengths. The pump pulse ablates the target and generates the early plasma, and the probe pulse propagates through the plasma region and detects the non-uniformity of electron number density. In addition, animations are generated using the calculated results from the simulation model of Ref. 12 to illustrate the plasma formation and evolution with a very high resolution (0.04 ~ 1 ps). Both the experimental method and the simulation method can be applied to a broad range of time frames and laser parameters. These methods can be used to examine the early plasma generated not only from metals, but also from semiconductors and insulators. PMID:22806170

  8. Ultrashort pulse propagation in multiple-grating fiber structures.

    PubMed

    Chen, L R; Benjamin, S D; Smith, P W; Sipe, J E; Juma, S

    1997-03-15

    We propose a multiple-grating fiber structure that decomposes an ultrashort broadband optical pulse simultaneously in both wavelength and time. As an initial demonstration, we used a transform-limited 1-ps Gaussian pulse centered at 1.55 mu;m as the ultrashort broadband input into a three-grating fiber structure and generated three output pulses separated in wavelength and time with good correlation between experimental results and simulations. This device structure can be used to generate a multiwavelength train of pulses for use in wavelength-division-multiplexed systems or to implement frequency-domain encoding of coherent pulses for optical code-division multiple access. PMID:18183215

  9. Solitary Nanostructures Produced by Ultrashort Laser Pulse.

    PubMed

    Inogamov, Nail A; Zhakhovsky, Vasily V; Khokhlov, Viktor A; Petrov, Yury V; Migdal, Kirill P

    2016-12-01

    Laser-produced surface nanostructures show considerable promise for many applications while fundamental questions concerning the corresponding mechanisms of structuring are still debated. Here, we present a simple physical model describing those mechanisms happened in a thin metal film on dielectric substrate irradiated by a tightly focused ultrashort laser pulse. The main ingredients included into the model are (i) the film-substrate hydrodynamic interaction, melting and separation of the film from substrate with velocity increasing with increase of absorbed fluence; (ii) the capillary forces decelerating expansion of the expanding flying film; and (iii) rapid freezing into a solid state if the rate of solidification is comparable or larger than hydrodynamic velocities. The developed model and performed simulations explain appearance of microbump inside the focal spot on the film surface. The model follows experimental findings about gradual transformation of the bump from small parabolic to a conical shape and to the bump with a jet on its tip with increasing fluence. Disruption of the bump as a result of thinning down the liquid film to a few interatomic distances or due to mechanical break-off of solid film is described together with the jetting and formation of one or many droplets. Developed theory opens door for optimizing laser parameters for intended nanostructuring in applications. PMID:27044306

  10. Solitary Nanostructures Produced by Ultrashort Laser Pulse

    NASA Astrophysics Data System (ADS)

    Inogamov, Nail A.; Zhakhovsky, Vasily V.; Khokhlov, Viktor A.; Petrov, Yury V.; Migdal, Kirill P.

    2016-04-01

    Laser-produced surface nanostructures show considerable promise for many applications while fundamental questions concerning the corresponding mechanisms of structuring are still debated. Here, we present a simple physical model describing those mechanisms happened in a thin metal film on dielectric substrate irradiated by a tightly focused ultrashort laser pulse. The main ingredients included into the model are (i) the film-substrate hydrodynamic interaction, melting and separation of the film from substrate with velocity increasing with increase of absorbed fluence; (ii) the capillary forces decelerating expansion of the expanding flying film; and (iii) rapid freezing into a solid state if the rate of solidification is comparable or larger than hydrodynamic velocities. The developed model and performed simulations explain appearance of microbump inside the focal spot on the film surface. The model follows experimental findings about gradual transformation of the bump from small parabolic to a conical shape and to the bump with a jet on its tip with increasing fluence. Disruption of the bump as a result of thinning down the liquid film to a few interatomic distances or due to mechanical break-off of solid film is described together with the jetting and formation of one or many droplets. Developed theory opens door for optimizing laser parameters for intended nanostructuring in applications.

  11. Controlling plasma channels through ultrashort laser pulse filamentation

    NASA Astrophysics Data System (ADS)

    Ionin, Andrey A.; Seleznev, Leonid V.; Sunchugasheva, Elena S.

    2013-10-01

    A review of studies fulfilled at the Lebedev Institute in collaboration with the Moscow State University and Institute of Atmospheric Optics in Tomsk (Siberia) on influence of various characteristics of ultrashort laser pulse on plasma channels formed under its filamentation is presented. Filamentation of high-power laser pulses with wavefront controlled by a deformable mirror, with cross-sections spatially formed by various diaphragms and with different wavelengths was experimentally and numerically studied. An application of plasma channels formed due to filamentation of ultrashort laser pulse including a train of such pulses for triggering and guiding electric discharge is discussed.

  12. Buffering and trapping ultrashort optical pulses in concatenated Bragg gratings.

    PubMed

    Fu, Shenhe; Liu, Yikun; Li, Yongyao; Song, Liyan; Li, Juntao; Malomed, Boris A; Zhou, Jianying

    2013-12-01

    Strong retardation of ultrashort optical pulses, including their deceleration and stoppage in the form of Bragg solitons in a cascaded Bragg grating (BG) structure, is proposed. The manipulations of the pulses are carried out, using nonlinear effects, in a chirped BG segment which is linked, via a defect, to a uniform grating. The storage of the ultrashort pulses is shown to be very robust with respect to variations of the input field intensity, suggesting the feasibility of storing ultrafast optical pulses in such a structure. Physical estimates are produced for the BGs written in silicon. PMID:24281506

  13. Pulse front adaptive optics: a new method for control of ultrashort laser pulses.

    PubMed

    Sun, Bangshan; Salter, Patrick S; Booth, Martin J

    2015-07-27

    Ultrafast lasers enable a wide range of physics research and the manipulation of short pulses is a critical part of the ultrafast tool kit. Current methods of laser pulse shaping are usually considered separately in either the spatial or the temporal domain, but laser pulses are complex entities existing in four dimensions, so full freedom of manipulation requires advanced forms of spatiotemporal control. We demonstrate through a combination of adaptable diffractive and reflective optical elements - a liquid crystal spatial light modulator (SLM) and a deformable mirror (DM) - decoupled spatial control over the pulse front (temporal group delay) and phase front of an ultra-short pulse was enabled. Pulse front modulation was confirmed through autocorrelation measurements. This new adaptive optics technique, for the first time enabling in principle arbitrary shaping of the pulse front, promises to offer a further level of control for ultrafast lasers. PMID:26367595

  14. Plasma mediated ablation of biological tissues with ultrashort laser pulses

    SciTech Connect

    Oraevsky, A.A. |; DaSilva, L.B.; Feit, M.D.

    1995-03-08

    Plasma mediated ablation of collagen gels and porcine cornea was studied at various laser pulse durations in the range from 350 fs to 1 ns at 1,053 nm wavelength. A time resolved stress detection technique was employed to measure transient stress profiles and amplitudes. Optical microscopy was used to characterize ablation craters qualitatively, while a wide band acoustic transducer helped to quantify tissue mechanical response and the ablation threshold. The ablation threshold was measured as a function of laser pulse duration and linear absorption coefficient. For nanosecond pulses the ablation threshold was found to have a strong dependence on the linear absorption coefficient of the material. As the pulse length decreased into the subpicosecond regime the ablation threshold became insensitive to the linear absorption coefficient. The ablation efficiency was found to be insensitive to both the laser pulse duration and the linear absorption coefficient. High quality ablation craters with no thermal or mechanical damage to surrounding material were obtained with 350 fs laser pulses. The mechanism of optical breakdown at the tissue surface was theoretically investigated. In the nanosecond regime, optical breakdown proceeds as an electron collisional avalanche ionization initiated by thermal seed electrons. These seed electrons are created by heating of the tissue by linear absorption. In the ultrashort pulse range, optical breakdown is initiated by the multiphoton ionization of the irradiated medium (6 photons in case of tissue irradiated at 1,053 nm wavelength), and becomes less sensitive to the linear absorption coefficient. The energy deposition profile is insensitive to both the laser pulse duration and the linear absorption coefficient.

  15. Ultra-short pulses to signal neuronal growth cone machinery

    NASA Astrophysics Data System (ADS)

    Mathew, Manoj; Amat-Roldan, Ivan; Andres, Rosa; Cormack, Iain G.; Artigas, David; Soriano, Eduardo; Loza-Alvarez, Pablo

    2007-02-01

    Measurable change in the sensory motor machinery of growth cones are induced by non contact femtosecond laser. The focused laser beam with an average power of 3 mW was positioned at some distance away from the closest fillopodia of cortical neurons from primary cell cultures (mice E15). By identifying a set of preliminary parameters we were able to statistically analyze the phenomenological behavior of the fillopodia and classify the effects different conditions of laser light has on the growth cone. Results show that fillopodia become significantly biased towards the focused femtosecond laser light. The same experiment performed with continuous wave (CW) produced results which were indistinguishable from the case where there is no laser light present (placebo condition) indicating no clear effects of the CW laser light on the fillopodia at a distance. These findings show the potential for ultrashort pulsed light to become a new type of pathfinding cue for neuronal growth cones.

  16. Measurement of energy contrast of amplified ultrashort pulses using cross-polarized wave generation and spectral interferometry.

    PubMed

    Iliev, Marin; Meier, Amanda K; Galloway, Benjamin; Adams, Daniel E; Squier, Jeff A; Durfee, Charles G

    2014-07-28

    We present a method using spectral interferometry (SI) to characterize a pulse in the presence of an incoherent background such as amplified spontaneous emission (ASE). The output of a regenerative amplifier is interfered with a copy of the pulse that has been converted using third-order cross-polarized wave generation (XPW). The ASE shows as a pedestal background in the interference pattern. The energy contrast between the short-pulse component and the ASE is retrieved. The spectra of the interacting beams are obtained through an improvement to the self-referenced spectral interferometry (SRSI) analysis. PMID:25089416

  17. Modeling and simulation of ultra-short pulse amplification

    NASA Astrophysics Data System (ADS)

    Pflaum, Christoph; Hartmann, Rainer; Rahimi, Zhabiz

    2016-03-01

    Ultra-short pulses with high average power are required for a variety of technical and medical applications. Single, multi-pass, and regenerative amplifiers are used, in order to increase the power of ultra-short lasers. Typical laser crystals for such amplifiers include Ti:Sapphire or Yb:YAG laser crystals. Difficulties in the amplification of ultra-short pulses include gain narrowing effects and dispersion effects in the laser crystal. In particular, these complications arise, when a pulse stretcher is needed before amplification of the laser beam. We present a technique to model and simulate the amplification of ultra-short pulses. This technique allows to model both gain narrowing effects and decrease of beam quality caused by amplification of the laser beam. This requires a detailed 3-dimensional simulation of population inversion. Gain narrowing effects are taken into account by analyzing the gain of the spectrum of the laser beam. It is important to distinguish amplifiers with one or only two passes and a regenerative amplifier. These two different kind of amplifiers are modeled by different approaches. A regenerative amplifier is modeled by a set of time dependent rate equations. However, a single pass amplifier is modeled by a set of spatial dependent rate equations. In both cases, a system of rate equations arises from spectral discretization of the laser beam. Detailed simulation results are presented.

  18. Energy Characteristics of Radiators of Ultrashort Electromagnetic Pulses

    NASA Astrophysics Data System (ADS)

    Usychenko, V. G.; Usychenko, A. S.; Sorokin, L. N.

    2015-07-01

    It is shown that to use the maximum share of the energy of a unipolar ultrashort electric pulse, its duration and shape, as well as the transmitting antenna parameters should, be related to the receiver center frequency and passband in a certain manner. Distortions introduced by the propagation effects to the received-radiation spectrum shape increase with broadening radiation and receiver frequency bands.

  19. Ultrashort pulse laser microsurgery system with plasma luminescence feedback control

    SciTech Connect

    Kim, B.M.; Feit, M.D.; Rubenchik, A.M.; Gold, D.M.; Darrow, C.B.; Da Silva, L.B.

    1997-11-10

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue during ultrashort pulse laser (USPL) micro-spinal surgery. Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so that only bone tissue can be selectively ablated while preserving the spinal cord.

  20. 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.

  1. Controlling Plasma Channels through Ultrashort Laser Pulse Filamentation

    NASA Astrophysics Data System (ADS)

    Ionin, Andrey; Seleznev, Leonid; Sunchugasheva, Elena

    2013-09-01

    A review of studies fulfilled at the Lebedev Institute in collaboration with the Moscow State University and Institute of Atmospheric Optics in Tomsk on influence of various characteristics of ultrashort laser pulse on plasma channels formed under its filamentation is presented. Filamentation of high-power laser pulses with wavefront controlled by a deformable mirror, with cross-sections spatially formed by various diaphragms and with different wavelengths was experimentally and numerically studied. An application of plasma channels formed due to filamentation of ultrashort laser pulse including a train of such pulses for triggering and guiding long electric discharges is discussed. The research was supported by RFBR Grants 11-02-12061-ofi-m and 11-02-01100, and EOARD Grant 097007 through ISTC Project 4073 P

  2. Photoionization of noble-gas atoms by ultrashort electromagnetic pulses

    SciTech Connect

    Astapenko, V. A. Svita, S. Yu.

    2014-11-15

    The photoionization of atoms of noble gases (Ar, Kr, and Xe) by ultrashort electromagnetic pulses of a corrected Gaussian shape is studied theoretically. Computations are performed in the context of perturbation theory using a simple expression for the total probability of photoionization of an atom by electromagnetic pulses. The features of this process are revealed and analyzed for various ranges of the parameters of the problem.

  3. Filamentation of ultrashort laser pulses propagating in tenuous plasmas

    SciTech Connect

    Andreev, N. E.; Gorbunov, L. M.; Mora, P.; Ramazashvili, R. R.

    2007-08-15

    The filamentation of ultrashort laser pulses (shorter than a plasma period) propagating in tenuous plasmas is studied. In this regime relativistic and ponderomotive nonlinearities tend to cancel each other. Time-dependent residual nonlinear plasma response brings about the dynamical filamentation with the maximum unstable transverse wave number decreasing in the course of laser pulse propagation. Dynamics of a hot spot that seeds the filamentation instability is studied numerically and reveals a good agreement with the analytical results.

  4. Scattering of an ultrashort electromagnetic pulse in a plasma

    SciTech Connect

    Astapenko, V. A.

    2011-11-15

    An analytic approach is developed to describing how ultrashort electromagnetic pulses with a duration of one period or less at the carrier frequency are scattered in a plasma. Formulas are derived to calculate and analyze the angular and spectral probabilities of radiation scattering via two possible mechanisms-Compton and transition radiation channels-throughout the entire pulse. Numerical simulations were carried out for a Gaussian pulse. The effect of the phase of the carrier frequency relative to the pulse envelope on the scattering parameters is investigated.

  5. Deterministic processing of alumina with ultra-short laser pulses

    SciTech Connect

    Furmanski, J; Rubenchik, A M; Shirk, M D; Stuart, B C

    2007-06-27

    Ultrashort pulsed lasers can accurately ablate materials which are refractory, transparent, or are otherwise difficult to machine by other methods. The typical method of machining surfaces with ultrashort laser pulses is by raster scanning, or the machining of sequentially overlapping linear trenches. Experiments in which linear trenches were machined in alumina at various pulse overlaps and incident fluences are presented, and the dependence of groove depth on these parameters established. A model for the machining of trenches based on experimental data in alumina is presented, which predicts and matches observed trench geometry. This model is then used to predict optimal process parameters for the machining of trenches for maximal material removal rate for a given laser.

  6. Interaction of ultrashort laser pulses and silicon solar cells under short circuit conditions

    SciTech Connect

    Mundus, M. Giesecke, J. A.; Fischer, P.; Hohl-Ebinger, J.; Warta, W.

    2015-02-28

    Ultrashort pulse lasers are promising tools for numerous measurement purposes. Among other benefits their high peak powers allow for efficient generation of wavelengths in broad spectral ranges and at spectral powers that are orders of magnitude higher than in conventional light sources. Very recently this has been exploited for the establishment of sophisticated measurement facilities for electrical characterization of photovoltaic (PV) devices. As the high peak powers of ultrashort pulses promote nonlinear optical effects they might also give rise to nonlinear interactions with the devices under test that possibly manipulate the measurement outcome. In this paper, we present a comprehensive theoretical and experimental study of the nonlinearities affecting short circuit current (I{sub SC}) measurements of silicon (Si) solar cells. We derive a set of coupled differential equations describing the radiation-device interaction and discuss the nonlinearities incorporated in those. By a semi-analytical approach introducing a quasi-steady-state approximation and integrating a Green's function we solve the system of equations and obtain simulated I{sub SC} values. We validate the theoretical model by I{sub SC} ratios obtained from a double ring resonator setup capable for reproducible generation of various ultrashort pulse trains. Finally, we apply the model to conduct the most prominent comparison of I{sub SC} generated by ultrashort pulses versus continuous illumination. We conclude by the important finding that the nonlinearities induced by ultrashort pulses are negligible for the most common I{sub SC} measurements. However, we also find that more specialized measurements (e.g., of concentrating PV or Si-multijunction devices as well as highly localized electrical characterizations) will be biased by two-photon-absorption distorting the I{sub SC} measurement.

  7. Interaction of ultrashort laser pulses and silicon solar cells under short circuit conditions

    NASA Astrophysics Data System (ADS)

    Mundus, M.; Giesecke, J. A.; Fischer, P.; Hohl-Ebinger, J.; Warta, W.

    2015-02-01

    Ultrashort pulse lasers are promising tools for numerous measurement purposes. Among other benefits their high peak powers allow for efficient generation of wavelengths in broad spectral ranges and at spectral powers that are orders of magnitude higher than in conventional light sources. Very recently this has been exploited for the establishment of sophisticated measurement facilities for electrical characterization of photovoltaic (PV) devices. As the high peak powers of ultrashort pulses promote nonlinear optical effects they might also give rise to nonlinear interactions with the devices under test that possibly manipulate the measurement outcome. In this paper, we present a comprehensive theoretical and experimental study of the nonlinearities affecting short circuit current (ISC) measurements of silicon (Si) solar cells. We derive a set of coupled differential equations describing the radiation-device interaction and discuss the nonlinearities incorporated in those. By a semi-analytical approach introducing a quasi-steady-state approximation and integrating a Green's function we solve the system of equations and obtain simulated ISC values. We validate the theoretical model by ISC ratios obtained from a double ring resonator setup capable for reproducible generation of various ultrashort pulse trains. Finally, we apply the model to conduct the most prominent comparison of ISC generated by ultrashort pulses versus continuous illumination. We conclude by the important finding that the nonlinearities induced by ultrashort pulses are negligible for the most common ISC measurements. However, we also find that more specialized measurements (e.g., of concentrating PV or Si-multijunction devices as well as highly localized electrical characterizations) will be biased by two-photon-absorption distorting the ISC measurement.

  8. Cavity Optical Pulse Extraction: ultra-short pulse generation as seeded Hawking radiation

    PubMed Central

    Eilenberger, Falk; Kabakova, Irina V.; de Sterke, C. Martijn; Eggleton, Benjamin J.; Pertsch, Thomas

    2013-01-01

    We show that light trapped in an optical cavity can be extracted from that cavity in an ultrashort burst by means of a trigger pulse. We find a simple analytic description of this process and show that while the extracted pulse inherits its pulse length from that of the trigger pulse, its wavelength can be completely different. Cavity Optical Pulse Extraction is thus well suited for the development of ultrashort laser sources in new wavelength ranges. We discuss similarities between this process and the generation of Hawking radiation at the optical analogue of an event horizon with extremely high Hawking temperature. Our analytic predictions are confirmed by thorough numerical simulations. PMID:24060831

  9. Superfocusing of an ultrashort plasmon pulse by a conducting cone

    NASA Astrophysics Data System (ADS)

    Manuilovich, E. S.; Astapenko, V. A.; Golovinskii, P. A.

    2016-01-01

    We have shown theoretically the possibility of controlling nanoscale superfocusing of plasmons in a metal conical tip by modulating the carrier frequency of the pulse. The propagation of an ultrashort plasmon pulse in a metal nanoneedle is simulated numerically. The calculation is based on an asymptotic analytical solution of Maxwell's equations for electromagnetic wave propagation in a conical conductor in the vicinity of its apex, obtained by the approximate separation of variables in spherical coordinates. The dependence the field superfocusing on the conductor material, pulse chirp and propagation length is studied.

  10. Pathogen reduction in human plasma using an ultrashort pulsed laser.

    PubMed

    Tsen, Shaw-Wei D; Kingsley, David H; Kibler, Karen; Jacobs, Bert; Sizemore, Sara; Vaiana, Sara M; Anderson, Jeanne; Tsen, Kong-Thon; Achilefu, Samuel

    2014-01-01

    Pathogen reduction is a viable approach to ensure the continued safety of the blood supply against emerging pathogens. However, the currently licensed pathogen reduction techniques are ineffective against non-enveloped viruses such as hepatitis A virus, and they introduce chemicals with concerns of side effects which prevent their widespread use. In this report, we demonstrate the inactivation of both enveloped and non-enveloped viruses in human plasma using a novel chemical-free method, a visible ultrashort pulsed laser. We found that laser treatment resulted in 2-log, 1-log, and 3-log reductions in human immunodeficiency virus, hepatitis A virus, and murine cytomegalovirus in human plasma, respectively. Laser-treated plasma showed ≥70% retention for most coagulation factors tested. Furthermore, laser treatment did not alter the structure of a model coagulation factor, fibrinogen. Ultrashort pulsed lasers are a promising new method for chemical-free, broad-spectrum pathogen reduction in human plasma. PMID:25372037

  11. Pathogen Reduction in Human Plasma Using an Ultrashort Pulsed Laser

    PubMed Central

    Tsen, Shaw-Wei D.; Kingsley, David H.; Kibler, Karen; Jacobs, Bert; Sizemore, Sara; Vaiana, Sara M.; Anderson, Jeanne; Tsen, Kong-Thon; Achilefu, Samuel

    2014-01-01

    Pathogen reduction is a viable approach to ensure the continued safety of the blood supply against emerging pathogens. However, the currently licensed pathogen reduction techniques are ineffective against non-enveloped viruses such as hepatitis A virus, and they introduce chemicals with concerns of side effects which prevent their widespread use. In this report, we demonstrate the inactivation of both enveloped and non-enveloped viruses in human plasma using a novel chemical-free method, a visible ultrashort pulsed laser. We found that laser treatment resulted in 2-log, 1-log, and 3-log reductions in human immunodeficiency virus, hepatitis A virus, and murine cytomegalovirus in human plasma, respectively. Laser-treated plasma showed ≥70% retention for most coagulation factors tested. Furthermore, laser treatment did not alter the structure of a model coagulation factor, fibrinogen. Ultrashort pulsed lasers are a promising new method for chemical-free, broad-spectrum pathogen reduction in human plasma. PMID:25372037

  12. Grating configurations to compress extreme-ultraviolet ultrashort pulses.

    PubMed

    Frassetto, Fabio; Poletto, Luca

    2015-09-10

    It is here discussed the design of ultrafast extreme-ultraviolet (XUV) grating compressors that can be used to condition the spectral phase of ultrashort chirped pulses to compensate for the phase chirp and get closer to the Fourier limit. We discuss the two configurations that can be used to realize the compressor, the classical diffraction mount, and the off-plane one. The concept is applied to the realization of a XUV compressor with applications to free-electron lasers. PMID:26368974

  13. Optical feedback signal for ultrashort laser pulse ablation of tissue

    SciTech Connect

    Kim, B.-M.; Feit, M.D.; Rubenchik, A.M.; Mammini, B.M.; Da Silva, L.B.

    1997-07-01

    An optical feedback system for controlled precise tissue ablation is discussed. Our setup includes an ultrashort pulse laser (USPL), and a diagnostic system using analysis of either tissue fluorescence or plasma emission luminescence. Current research is focused on discriminating hard and soft tissues such as bone and spinal cord during surgery using either technique. Our experimental observations exhibit considerable spectroscopic contrast between hard and soft tissue, and both techniques offer promise for a practical diagnostic system.

  14. Broadening of ultra-short pulses propagating through weak-to-strong oceanic turbulence

    NASA Astrophysics Data System (ADS)

    Wang, Zhiqiang; Lu, Lu; Zhang, Pengfei; Fan, Chengyu; Ji, Xiaoling

    2016-05-01

    In this paper, the new approach of correlation function of the complex phase perturbed by oceanic turbulence is shown. Based on this new approach, the general formula of the two-frequency mutual coherence function (MCF) of ultra-short pulses in oceanic turbulence is derived. Using a temporal moments approach and combining with this new formula for the MCF, the analytical expression for the pulse width is deduced. Besides, the quantity of Rytov variance σR2 in oceanic turbulence is obtained, which is widely used as a measure of the strength of turbulence. In particular, the on-axis relative pulse broadening and turbulent effective coefficient of ultra-short pulses (i.e., femtosecond-picosecond regime) propagating through oceanic turbulence are investigated.

  15. Plasma Membrane Permeabilization by Trains of Ultrashort Electric Pulses

    PubMed Central

    Ibey, Bennett L.; Mixon, Dustin G.; Payne, Jason A.; Bowman, Angela; Sickendick, Karl; Wilmink, Gerald J.; Roach, W. Patrick; Pakhomov, Andrei G.

    2010-01-01

    Ultrashort electric pulses (USEP) cause long-lasting increase of cell membrane electrical conductance, and that a single USEP increased cell membrane electrical conductance proportionally to the absorbed dose (AD) with a threshold of about 10 mJ/g. The present study extends quantification of the membrane permeabilization effect to multiple USEP and employed a more accurate protocol that identified USEP effect as the difference between post- and pre-exposure conductance values (Δg) in individual cells. We showed that Δg can be increased by either increasing the number of pulses at a constant E-field, or by increasing the E-field at a constant number of pulses. For 60-ns pulses, an E-field threshold of 6 kV/cm for a single pulse was lowered to less than 1.7 kV/cm by applying 100-pulse or longer trains. However, the reduction of the E-field threshold was only achieved at the expense of a higher AD compared to a single pulse exposure. Furthermore, the effect of multiple pulses was not fully determined by AD, suggesting that cells permeabilized by the first pulse(s) in the train become less vulnerable to subsequent pulses. This explanation was corroborated by a model that treated multiple-pulse exposures as a series of single-pulse exposures and assumed an exponential decline of cell susceptibility to USEP as Δg increased after each pulse during the course of the train. PMID:20171148

  16. Ultrashort pulsed laser technology development program

    NASA Astrophysics Data System (ADS)

    Manke, Gerald C.

    2014-10-01

    The Department of Navy has been pursuing a technology development program for advanced, all-fiber, Ultra Short Pulsed Laser (USPL) systems via Small Business Innovative Research (SBIR) programs. Multiple topics have been published to promote and fund research that encompasses every critical component of a standard USPL system and enable the demonstration of mJ/pulse class systems with an all fiber architecture. This presentation will summarize published topics and funded programs.

  17. Optical generation of intense ultrashort magnetic pulses at the nanoscale

    NASA Astrophysics Data System (ADS)

    Tsiatmas, Anagnostis; Atmatzakis, Evangelos; Papasimakis, Nikitas; Fedotov, Vassili; Luk'yanchuk, Boris; Zheludev, Nikolay I.; García de Abajo, F. Javier

    2013-11-01

    Generating, controlling and sensing strong magnetic fields at ever shorter time and length scales is important for both fundamental solid-state physics and technological applications such as magnetic data recording. Here, we propose a scheme for producing strong ultrashort magnetic pulses localized at the nanoscale. We show that a bimetallic nanoring illuminated by femtosecond laser pulses responds with transient thermoelectric currents of picosecond duration, which in turn induce Tesla-scale magnetic fields in the ring cavity. Our method provides a practical way of generating intense nanoscale magnetic fields with great potential for materials characterization, terahertz radiation generation and data storage applications.

  18. Ultrashort pulse amplification in cryogenically cooled amplifiers

    DOEpatents

    Backus, Sterling J.; Kapteyn, Henry C.; Murnane, Margaret Mary

    2004-10-12

    A laser amplifier system amplifies pulses in a single "stage" from .about.10.sup.-9 joules to more than 10.sup.-3 joules, with average power of 1-10 watts, and beam quality M.sup.2 <2. The laser medium is cooled substantially below room temperature, as a means to improve the optical and thermal characteristics of the medium. This is done with the medium inside a sealed, evacuated or purged cell to avoid moisture or other materials condensing on the surface. A "seed" pulse from a separate laser is passed through the laser medium, one or more times, in any of a variety of configurations including single-pass, multiple-pass, and regenerative amplifier configurations.

  19. Ultrashort pulses in graphene with Coulomb impurities

    NASA Astrophysics Data System (ADS)

    Konobeeva, N. N.; Belonenko, M. B.

    2016-06-01

    We have investigated the propagation of an electromagnetic field in graphene with impurities, including the two-dimensional case. The spectrum of electrons for the graphene subsystem is taken from a model that takes into account Coulomb impurities. Based on Maxwell's equations, we have obtained an effective equation for the vector potential of the electromagnetic field. It has been revealed that the pulse shape depends on free parameters.

  20. Surface roughness and wettability of dentin ablated with ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Lü, Peijun; Sun, Yuchun; Wang, Yong

    2015-05-01

    The aim of this study was to evaluate the surface roughness and wettability of dentin following ultrashort pulsed laser ablation with different levels of fluence and pulse overlap (PO). Twenty-five extracted human teeth crowns were cut longitudinally into slices of approximately 1.5-mm thick and randomly divided into nine groups of five. Samples in groups 1 to 8 were ablated with an ultrashort pulsed laser through a galvanometric scanning system. Samples in group 9 were prepared using a mechanical rotary instrument. The surface roughness of samples from each group was then measured using a three-dimensional profile measurement laser microscope, and wettability was evaluated by measuring the contact angle of a drop of water on the prepared dentin surface using an optical contact angle measuring device. The results showed that both laser fluence and PO had an effect on dentin surface roughness. Specifically, a higher PO decreased dentin surface roughness and reduced the effect of high-laser fluence on decreasing the surface roughness in some groups. Furthermore, all ablated dentin showed a contact angle of approximately 0 deg, meaning that laser ablation significantly improved wettability. Adjustment of ultrashort pulsed laser parameters can, therefore, significantly alter dentin surface roughness and wettability.

  1. Comparison of ultrashort-pulse frequency-resolved-optical-gating traces for three common beam geometries

    SciTech Connect

    DeLong, K.W.; Trebino, R. ); Kane, D.J. )

    1994-09-01

    We recently introduced frequency-resolved optical gating (FROG), a technique for measuring the intensity and phase of an individual, arbitrary, ultrashort laser pulse. FROG can use almost any instantaneous optical nonlinearity, with the most common geometries being polarization gate, self-diffraction, and second-harmonic generation. The experimentally generated FROG trace is intuitive, visually appealing, and can yield quantitative information about the pulse parameters (such as temporal and spectral width and chirp). However, the qualitative and the quantitative features of the FROG trace depend strongly on the geometry used. We compare the FROG traces for several common ultrashort pulses for these three common geometries and, where possible, develop scaling rules that allow one to obtain quantitative information about the pulse directly from the experimental FROG trace. We illuminate the important features of the various FROG traces for transform-limited, linearly chirped, self-phase modulated, and nonlinearly chirped pulses, pulses with simultaneous linear chirp and self-phase modulation, and pulses with simultaneous linear chirp and cubic phase distortion, as well as double pulses, pulses with phase jumps, and pulses with complex intensity and phase substructure.

  2. The Quest for Ultra-Short X-Ray Pulses

    SciTech Connect

    Zholents, Alexander

    2011-03-09

    Chemical bonds form, change, or break on a femtosecond timescale. Recording a 'molecular movie' with an atomic-scale spatial resolution at the timescale set by atomic motion is a critical step in understanding these processes that can be accomplished by using ultra-short x-ray pulses. In the first part of this talk I will discuss several ideas for a generation of femtosecond x-ray pulses using spontaneous emission of electrons. Some of them, like the laser 'slicing' technique, are now routinely used at several storage-ring-based synchrotron light sources; others, like an rf orbit deflection technique, is under construction at the Advanced Photon Source. Nowadays, the femtosecond x-ray pulses are also routinely produced by x-ray free electron lasers (FELs). In the second part of this talk I will discuss how one can use FELs to obtain even shorter x-ray pulses down to attosecond timescale.

  3. Sudden perturbation of hydrogen atoms by intense ultrashort laser pulses

    SciTech Connect

    Lugovskoy, A. V.; Bray, I.

    2005-12-15

    We study theoretically how hydrogen atoms respond to intense ultrashort laser pulses of duration {tau} shorter than the inverse of the initial-state energy {epsilon}{sub i}{sup -1}. An analytical expression for the evolution operator S is derived up to the first order of the sudden perturbation approximation. This approximation treats the laser-atom interaction beyond the dipole approximation and yields S as a series in the small parameter {epsilon}{sub i}{tau}. It is shown that the effect of realistic laser pulses on atoms begins at the first order of {epsilon}{sub i}{tau}. Transitions between atomic (nlm) states of different m become possible due to the action of the pulse's magnetic field. Transitions between states of same m and arbitrary l become possible if the static Coulomb potential is taken into account during the pulse.

  4. Generation of ultrashort electron bunches by colliding laser pulses

    SciTech Connect

    Schroeder, C. B.; Lee, P. B.; Wurtele, J. S.; Esarey, E.; Leemans, W. P.

    1999-07-12

    A proposed laser-plasma based relativistic electron source [E. Esarey et al., Phys. Rev. Lett. 79, 2682 (1997)] using laser triggered injection of electrons is investigated. The source generates ultrashort electron bunches by dephasing and trapping background plasma electrons undergoing fluid oscillations in an excited plasma wake. The plasma electrons are dephased by colliding two counter-propagating laser pulses which generate a slow phase velocity beat wave. Laser pulse intensity thresholds for trapping and the optimal wake phase for injection are calculated. Numerical simulations of test particles, with prescribed plasma and laser fields, are used to verify analytic predictions and to study the longitudinal and transverse dynamics of the trapped plasma electrons. Simulations indicate that the colliding laser pulse injection scheme has the capability to produce relativistic femtosecond electron bunches with fractional energy spread of order a few percent and normalized transverse emittance less than 1 mm mrad using 1 TW injection laser pulses.

  5. Generation of ultrashort electron bunches by colliding laser pulses.

    PubMed

    Schroeder, C B; Lee, P B; Wurtele, J S; Esarey, E; Leemans, W P

    1999-05-01

    A proposed laser-plasma-based relativistic electron source [E. Esarey et al., Phys. Rev. Lett. 79, 2682 (1997)] using laser-triggered injection of electrons is investigated. The source generates ultrashort electron bunches by dephasing and trapping background plasma electrons undergoing fluid oscillations in an excited plasma wake. The plasma electrons are dephased by colliding two counterpropagating laser pulses which generate a slow phase velocity beat wave. Laser pulse intensity thresholds for trapping and the optimal wake phase for injection are calculated. Numerical simulations of test particles, with prescribed plasma and laser fields, are used to verify analytic predictions and to study the longitudinal and transverse dynamics of the trapped plasma electrons. Simulations indicate that the colliding laser pulse injection scheme has the capability to produce relativistic femtosecond electron bunches with fractional energy spread of order a few percent and normalized transverse emittance less than 1 mm mrad using 1 TW injection laser pulses. PMID:11969588

  6. An Ultra-Short Pulsed Neutron Source

    NASA Astrophysics Data System (ADS)

    Pomerantz, Ishay; McCary, Eddie; Meadows, Alexander R.; Arefiev, Alexey; Bernstein, Aaron C.; Chester, Clay; Cortez, Jose; Donovan, Michael E.; Dyer, Gilliss; Gaul, Erhard W.; Hamilton, David; Kuk, Donghoon; Lestrade, Arantxa; Wang, Chunhua; Ditmire, Todd; Hegelich, Manuel B.

    2014-10-01

    We report on a novel compact laser-driven neutron source with unprecedented short pulse duration (<50 ps) and high flux (>1018 neutrons/cm2/s), an order of magnitude higher than any existing source. In our experiments, high-energy electron jets are generated from thin (<1 μm) plastic targets irradiated by a petawatt laser. These intense electron beams are employed to generate neutrons from a metal converter. Our method opens venues for enhancing neutron radiography contrast, conducting time-resolved neutron-damage studies at their characteristic evolution time-scales and for creating astrophysical conditions of heavy element synthesis in the laboratory.

  7. Electrochemical nanostructuring with ultrashort voltage pulses.

    PubMed

    Kirchner, V; Xia, X; Schuster, R

    2001-05-01

    The application of nanosecond voltage pulses to electrodes provides three ways to conduct local electrochemistry on the micro- to nanometer scale. (1) The finite charging time of the double-layer capacity allows the machining of three-dimensional microstructures. (2) In an electrochemical scanning tunneling microscope, reactions are confined to the tunneling region, due to the depletion of the electrolyte in the tip--surface gap. (3) Ordering processes, following very fast electrochemical reactions, lead to unconventional island patterns on a surface. PMID:11352715

  8. Experimental study on double-pulse laser ablation of steel upon multiple parallel-polarized ultrashort-pulse irradiations

    NASA Astrophysics Data System (ADS)

    Schille, Joerg; Schneider, Lutz; Kraft, Sebastian; Hartwig, Lars; Loeschner, Udo

    2016-07-01

    In this paper, double-pulse laser processing is experimentally studied with the aim to explore the influence of ultrashort pulses with very short time intervals on ablation efficiency and quality. For this, sequences of 50 double pulses of varied energy and inter-pulse delay, as adjusted between 400 fs and 18 ns by splitting the laser beam into two optical paths of different length, were irradiated to technical-grade stainless steel. The depth and the volume of the craters produced were measured in order to evaluate the efficiency of the ablation process; the crater quality was analyzed by SEM micrographs. The results obtained were compared with craters produced with sequences of 50 single pulses and energies equal to the double pulse. It is demonstrated that double-pulse processing cannot exceed the ablation efficiency of single pulses of optimal fluence, but the ablation crater surface formed smoother if inter-pulse delay was in the range between 10 ns and 18 ns. In addition, the influence of pulse duration and energy distribution between the individual pulses of the double pulse on ablation was studied. For very short inter-pulse delay, no significant effect of energy variation within the double pulse on removal rate was found, indicating that the double pulse acts as a big single pulse of equal energy. Further, the higher removal efficiency was achieved when double-pulse processing using femtosecond pulses instead of picosecond pulses.

  9. Progress of diagnostics for coherent beam combination on ultrashort pulse

    NASA Astrophysics Data System (ADS)

    Ouyang, Xiaoping; Wang, Yang; Zhu, Baoqiang; Zhu, Jian; Zhu, Jianqiang

    2015-08-01

    Ultrashort pulse is important to exploring laser acceleration in many areas, such as fast ignition, advanced radiography capability. Petawatt laser should not only improve output energy on a single beam, but also combine multi-beams coherently. Diagnostics of temporal and phase synchronization is developed for coherent beam combination on a 10ps laser pulse. When two pulses are guided into the diagnostics, one goes through a temporal delay unit and a lens with a focal length 500mm, then arrives at detector unit, the other goes through a phase delay unit and the same lens, and then arrives at detector unit, too. First, temporal synchronization is adjusted by temporal delay unit and monitored by a cross-correlation generator in the detector unit. Second, phase synchronization is adjusted by phase delay unit and monitored by a far field interferogram in the detector unit. In our design, temporal resolution is 6.7fs in temporal synchronization, and phase resolution is 0.007π in phase synchronization. Experiment has proved that this diagnostics is useful to realize synchronization between two ultrashort pulses both in temporal and in spatial.

  10. Ultrashort pulse laser deposition of thin films

    DOEpatents

    Perry, Michael D.; Banks, Paul S.; Stuart, Brent C.

    2002-01-01

    Short pulse PLD is a viable technique of producing high quality films with properties very close to that of crystalline diamond. The plasma generated using femtosecond lasers is composed of single atom ions with no clusters producing films with high Sp.sup.3 /Sp.sup.2 ratios. Using a high average power femtosecond laser system, the present invention dramatically increases deposition rates to up to 25 .mu.m/hr (which exceeds many CVD processes) while growing particulate-free films. In the present invention, deposition rates is a function of laser wavelength, laser fluence, laser spot size, and target/substrate separation. The relevant laser parameters are shown to ensure particulate-free growth, and characterizations of the films grown are made using several diagnostic techniques including electron energy loss spectroscopy (EELS) and Raman spectroscopy.

  11. Magnetization dynamics using ultrashort magnetic field pulses

    NASA Astrophysics Data System (ADS)

    Tudosa, Ioan

    Very short and well shaped magnetic field pulses can be generated using ultra-relativistic electron bunches at Stanford Linear Accelerator. These fields of several Tesla with duration of several picoseconds are used to study the response of magnetic materials to a very short excitation. Precession of a magnetic moment by 90 degrees in a field of 1 Tesla takes about 10 picoseconds, so we explore the range of fast switching of the magnetization by precession. Our experiments are in a region of magnetic excitation that is not yet accessible by other methods. The current table top experiments can generate fields longer than 100 ps and with strength of 0.1 Tesla only. Two types of magnetic were used, magnetic recording media and model magnetic thin films. Information about the magnetization dynamics is extracted from the magnetic patterns generated by the magnetic field. The shape and size of these patterns are influenced by the dissipation of angular momentum involved in the switching process. The high-density recording media, both in-plane and perpendicular type, shows a pattern which indicates a high spin momentum dissipation. The perpendicular magnetic recording media was exposed to multiple magnetic field pulses. We observed an extended transition region between switched and non-switched areas indicating a stochastic switching behavior that cannot be explained by thermal fluctuations. The model films consist of very thin crystalline Fe films on GaAs. Even with these model films we see an enhanced dissipation compared to ferromagnetic resonance studies. The magnetic patterns show that damping increases with time and it is not a constant as usually assumed in the equation describing the magnetization dynamics. The simulation using the theory of spin-wave scattering explains only half of the observed damping. An important feature of this theory is that the spin dissipation is time dependent and depends on the large angle between the magnetization and the magnetic

  12. Correlation in double ionization of He by ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Feist, Johannes

    2008-05-01

    Double ionization of helium has long been of considerable interest in atomic physics since it provides insight into the role of electronic correlation in the full three-body Coulomb break-up process, which is of fundamental importance for the understanding of the dynamics in more complex atoms. The recent availability of attosecond XUV pulses allows to directly probe and possibly control the temporal structure of the ionization process. We have implemented an ab initio simulation of the interaction of ultrashort laser pulses with a helium atom. The wave function is represented in a time-dependent close- coupling (TDCC) scheme and time integration is performed utilizing the Arnoldi-Lanczos method. The spatial discretization employs an FEDVR basis, which lends itself to effective parallelization. We will present results on two-photon double ionization of He by ultrashort pulses over a wide range of photon energies. At low energies only non-sequential double ionization is possible (where both electrons share the energy of the photons, and consequently have to be ionized within a short period). For photon energies above 54.4,V (the ionization potential of the He^+ ground state), sequential double ionization is allowed. This process proceeds in two steps -- single ionization of He followed by ionization of the remaining He^+ ion. By using attosecond XUV pulses, these two separated stages of the sequential process are confined to within a short time interval of each other. We show that the angular distributions of the emitted electrons reveal the signature of a non-sequential process under the condition that sufficiently short pulses are used, while for longer pulses the sequential process completely dominates. The correlation time for double ionization can thus be directly observed using attosecond XUV pulses. This work was performed in collaboration with S. Nagele, R. Pazourek, E. Persson, B. I. Schneider, L. A. Collins, and J. Burgd"orfer.

  13. Temporal pulse cleaning by a self-diffraction process for ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Xie, Na; Zhou, Kainan; Sun, Li; Wang, Xiaodong; Guo, Yi; Li, Qing; Su, Jingqin

    2014-11-01

    Applying the self-diffraction process to clean ultrashort laser pulses temporally is a recently developed effective way to temporal contrast enhancement. In this paper, we attempt to clean ultrashort laser pulses temporally by the self-diffraction process. Experiments were carried out to study the temporal contrast improvement in the front-end system of an ultraintense and ultrashort laser facility, i.e. the super intense laser for experiment on the extremes (SILEX-I). The results show that the maximum conversion efficiency of the first-order self-diffraction (SD1) pulse is 11%. The temporal contrast of the SD1 signal is improved by two orders of magnitude, i.e. to 103, for a 2.4-ns prepulse with initial contrast of ~10. For a 5.5 -ns prepulse with initial contrast of 2×103, the temporal contrast of the SD1 signal is improved by more than three orders of magnitude.

  14. Development of an (e,2e) electron momentum spectroscopy apparatus using an ultrashort pulsed electron gun

    SciTech Connect

    Yamazaki, M.; Kasai, Y.; Oishi, K.; Nakazawa, H.; Takahashi, M.

    2013-06-15

    An (e,2e) apparatus for electron momentum spectroscopy (EMS) has been developed, which employs an ultrashort-pulsed incident electron beam with a repetition rate of 5 kHz and a pulse duration in the order of a picosecond. Its instrumental design and technical details are reported, involving demonstration of a new method for finding time-zero. Furthermore, EMS data for the neutral Ne atom in the ground state measured by using the pulsed electron beam are presented to illustrate the potential abilities of the apparatus for ultrafast molecular dynamics, such as by combining EMS with the pump-and-probe technique.

  15. Underwater acoustic wave generation by filamentation of terawatt ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Jukna, Vytautas; Jarnac, Amélie; Milián, Carles; Brelet, Yohann; Carbonnel, Jérôme; André, Yves-Bernard; Guillermin, Régine; Sessarego, Jean-Pierre; Fattaccioli, Dominique; Mysyrowicz, André; Couairon, Arnaud; Houard, Aurélien

    2016-06-01

    Acoustic signals generated by filamentation of ultrashort terawatt laser pulses in water are characterized experimentally. Measurements reveal a strong influence of input pulse duration on the shape and intensity of the acoustic wave. Numerical simulations of the laser pulse nonlinear propagation and the subsequent water hydrodynamics and acoustic wave generation show that the strong acoustic emission is related to the mechanism of superfilamention in water. The elongated shape of the plasma volume where energy is deposited drives the far-field profile of the acoustic signal, which takes the form of a radially directed pressure wave with a single oscillation and a very broad spectrum.

  16. Underwater acoustic wave generation by filamentation of terawatt ultrashort laser pulses.

    PubMed

    Jukna, Vytautas; Jarnac, Amélie; Milián, Carles; Brelet, Yohann; Carbonnel, Jérôme; André, Yves-Bernard; Guillermin, Régine; Sessarego, Jean-Pierre; Fattaccioli, Dominique; Mysyrowicz, André; Couairon, Arnaud; Houard, Aurélien

    2016-06-01

    Acoustic signals generated by filamentation of ultrashort terawatt laser pulses in water are characterized experimentally. Measurements reveal a strong influence of input pulse duration on the shape and intensity of the acoustic wave. Numerical simulations of the laser pulse nonlinear propagation and the subsequent water hydrodynamics and acoustic wave generation show that the strong acoustic emission is related to the mechanism of superfilamention in water. The elongated shape of the plasma volume where energy is deposited drives the far-field profile of the acoustic signal, which takes the form of a radially directed pressure wave with a single oscillation and a very broad spectrum. PMID:27415357

  17. Black phosphorus saturable absorber for ultrashort pulse generation

    SciTech Connect

    Sotor, J. Sobon, G.; Abramski, K. M.; Macherzynski, W.; Paletko, P.

    2015-08-03

    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. 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.

  18. Photonic crystal Fano laser: terahertz modulation and ultrashort pulse generation.

    PubMed

    Mork, J; Chen, Y; Heuck, M

    2014-10-17

    We suggest and analyze a laser with a mirror realized by Fano interference between a waveguide and a nanocavity. For small-amplitude modulation of the nanocavity resonance, the laser can be modulated at frequencies exceeding 1 THz, not being limited by carrier dynamics as for conventional lasers. For larger modulation, a transition from pure frequency modulation to the generation of ultrashort pulses is observed. The laser dynamics is analyzed by generalizing the field equation for conventional lasers to account for a dynamical mirror, described by coupled mode theory. PMID:25361259

  19. Ultrashort pulsed fiber laser welding and sealing of transparent materials.

    PubMed

    Huang, Huan; Yang, Lih-Mei; Liu, Jian

    2012-05-20

    In this paper, methods of welding and sealing optically transparent materials using an ultrashort pulsed (USP) fiber laser are demonstrated which overcome the limit of small area welding of optical materials. First, the interaction of USP fiber laser radiation inside glass was studied and single line welding results with different laser parameters were investigated. Then multiline scanning was used to obtain successful area bonding. Finally, complete four-edge sealing of fused silica substrates with a USP laser was demonstrated and the hermetic seal was confirmed by water immersion test. This laser microwelding technique can be extended to various applications in the semiconductor industry and precision optic manufacturing. PMID:22614601

  20. Plasma lenses for ultrashort multi-petawatt laser pulses

    SciTech Connect

    Palastro, J. P.; Gordon, D.; Hafizi, B.; Johnson, L. A.; Peñano, J.; Hubbard, R. F.; Helle, M.; Kaganovich, D.

    2015-12-15

    An ideal plasma lens can provide the focusing power of a small f-number, solid-state focusing optic at a fraction of the diameter. An ideal plasma lens, however, relies on a steady-state, linear laser pulse-plasma interaction. Ultrashort multi-petawatt (MPW) pulses possess broad bandwidths and extreme intensities, and, as a result, their interaction with the plasma lens is neither steady state nor linear. Here, we examine nonlinear and time-dependent modifications to plasma lens focusing, and show that these result in chromatic and phase aberrations and amplitude distortion. We find that a plasma lens can provide enhanced focusing for 30 fs pulses with peak power up to ∼1 PW. The performance degrades through the MPW regime, until finally a focusing penalty is incurred at ∼10 PW.

  1. Plasma lenses for ultrashort multi-petawatt laser pulses

    NASA Astrophysics Data System (ADS)

    Palastro, J. P.; Gordon, D.; Hafizi, B.; Johnson, L. A.; Peñano, J.; Hubbard, R. F.; Helle, M.; Kaganovich, D.

    2015-12-01

    An ideal plasma lens can provide the focusing power of a small f-number, solid-state focusing optic at a fraction of the diameter. An ideal plasma lens, however, relies on a steady-state, linear laser pulse-plasma interaction. Ultrashort multi-petawatt (MPW) pulses possess broad bandwidths and extreme intensities, and, as a result, their interaction with the plasma lens is neither steady state nor linear. Here, we examine nonlinear and time-dependent modifications to plasma lens focusing, and show that these result in chromatic and phase aberrations and amplitude distortion. We find that a plasma lens can provide enhanced focusing for 30 fs pulses with peak power up to ˜1 PW. The performance degrades through the MPW regime, until finally a focusing penalty is incurred at ˜10 PW.

  2. Ultrashort laser pulse driven inverse free electron laser accelerator experiment

    NASA Astrophysics Data System (ADS)

    Moody, J. T.; Anderson, S. G.; Anderson, G.; Betts, S.; Fisher, S.; Tremaine, A.; Musumeci, P.

    2016-02-01

    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 gradients 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, nondestructive, 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 to pave the way towards the development of future GeV-class IFEL accelerators.

  3. Extremely simple single-prism ultrashort- pulse compressor.

    PubMed

    Akturk, Selcuk; Gu, Xun; Kimmel, Mark; Trebino, Rick

    2006-10-16

    We have designed and demonstrated a very simple and compact ultrashort-pulse compressor using a single prism and a corner-cube. Our design is significantly easier to align and tune compared with previous designs. Angle-tuning the prism wavelength-tunes, and translating the corner cube varies the group-delay dispersion over a wide range. When tuned, the device automatically maintains zero angular dispersion, zero pulse-front tilt, zero spatial chirp, and unity magnification. The device can easily be built so that its output beam remains collinear with the input beam, and when the input beam or pulse compressor moves, the input and output beams remain collinear. PMID:19529405

  4. Sample preparation method for glass welding by ultrashort laser pulses yields higher seam strength

    SciTech Connect

    Cvecek, K.; Miyamoto, I.; Strauss, J.; Wolf, M.; Frick, T.; Schmidt, M.

    2011-05-01

    Glass welding by ultrashort laser pulses allows joining without the need of an absorber or a preheating and postheating process. However, cracks generated during the welding process substantially impair the joining strength of the welding seams. In this paper a sample preparation method is described that prevents the formation of cracks. The measured joining strength of samples prepared by this method is substantially higher than previously reported values.

  5. Laser-Material Interaction of Powerful Ultrashort Laser Pulses

    SciTech Connect

    Komashko, A

    2003-01-06

    Laser-material interaction of powerful (up to a terawatt) ultrashort (several picoseconds or shorter) laser pulses and laser-induced effects were investigated theoretically in this dissertation. Since the ultrashort laser pulse (USLP) duration time is much smaller than the characteristic time of the hydrodynamic expansion and thermal diffusion, the interaction occurs at a solid-like material density with most of the light energy absorbed in a thin surface layer. Powerful USLP creates hot, high-pressure plasma, which is quickly ejected without significant energy diffusion into the bulk of the material, Thus collateral damage is reduced. These and other features make USLPs attractive for a variety of applications. The purpose of this dissertation was development of the physical models and numerical tools for improvement of our understanding of the process and as an aid in optimization of the USLP applications. The study is concentrated on two types of materials - simple metals (materials like aluminum or copper) and wide-bandgap dielectrics (fused silica, water). First, key physical phenomena of the ultrashort light interaction with metals and the models needed to describe it are presented. Then, employing one-dimensional plasma hydrodynamics code enhanced with models for laser energy deposition and material properties at low and moderate temperatures, light absorption was self-consistently simulated as a function of laser wavelength, pulse energy and length, angle of incidence and polarization. Next, material response on time scales much longer than the pulse duration was studied using the hydrocode and analytical models. These studies include examination of evolution of the pressure pulses, effects of the shock waves, material ablation and removal and three-dimensional dynamics of the ablation plume. Investigation of the interaction with wide-bandgap dielectrics was stimulated by the experimental studies of the USLP surface ablation of water (water is a model of

  6. Nonresonant interaction of ultrashort electromagnetic pulses with multilevel quantum systems

    NASA Technical Reports Server (NTRS)

    Belenov, E.; Isakov, V.; Nazarkin, A.

    1994-01-01

    Some features of the excitation of multilevel quantum systems under the action of electromagnetic pulses which are shorter than the inverse frequency of interlevel transitions are considered. It is shown that the interaction is characterized by a specific type of selectivity which is not connected with the resonant absorption of radiation. The simplest three-level model displays the inverse population of upper levels. The effect of an ultrashort laser pulse on a multilevel molecule was regarded as an instant reception of the oscillation velocity by the oscillator and this approach showed an effective excitation and dissociation of the molecule. The estimations testify to the fact that these effects can be observed using modern femtosecond lasers.

  7. Optical modulation of astrocyte network using ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Yoon, Jonghee; Ku, Taeyun; Chong, Kyuha; Ryu, Seung-Wook; Choi, Chulhee

    2012-03-01

    Astrocyte, the most abundant cell type in the central nervous system, has been one of major topics in neuroscience. Even though many tools have been developed for the analysis of astrocyte function, there has been no adequate tool that can modulates astrocyte network without pharmaceutical or genetic interventions. Here we found that ultrashort pulsed laser stimulation can induce label-free activation of astrocytes as well as apoptotic-like cell death in a dose-dependent manner. Upon irradiation with high intensity pulsed lasers, the irradiated cells with short exposure time showed very rapid mitochondria fragmentation, membrane blebbing and cytoskeletal retraction. We applied this technique to investigate in vivo function of astrocyte network in the CNS: in the aspect of neurovascular coupling and blood-brain barrier. We propose that this noninvasive technique can be widely applied for in vivo study of complex cellular network.

  8. Ultrashort electron pulses as a four-dimensional diagnosis of plasma dynamics.

    PubMed

    Zhu, P F; Zhang, Z C; Chen, L; Li, R Z; Li, J J; Wang, X; Cao, J M; Sheng, Z M; Zhang, J

    2010-10-01

    We report an ultrafast electron imaging system for real-time examination of ultrafast plasma dynamics in four dimensions. It consists of a femtosecond pulsed electron gun and a two-dimensional single electron detector. The device has an unprecedented capability of acquiring a high-quality shadowgraph image with a single ultrashort electron pulse, thus permitting the measurement of irreversible processes using a single-shot scheme. In a prototype experiment of laser-induced plasma of a metal target under moderate pump intensity, we demonstrated its unique capability of acquiring high-quality shadowgraph images on a micron scale with a-few-picosecond time resolution. PMID:21034089

  9. ULTRASHORT LIGHT PULSES: Formation of subfemtosecond laser pulses in aperiodically poled nonlinear-optical crystals

    NASA Astrophysics Data System (ADS)

    Shutov, I. V.; Novikov, A. A.; Chirkin, A. S.

    2008-03-01

    The method of synthesis of ultrashort laser pulses in nonlinear aperiodically poled crystals based on the simultaneous generation of several higher optical harmonics is considered. The interaction of four waves with multiple frequencies involving three mutually coupled nonlinear three-frequency processes is studied. It is shown that by introducing intense laser radiation into a crystal, pulses of duration of the order of a few hundreds of attoseconds can be produced at the crystal output.

  10. Multiphoton photoemission from a copper cathode illuminated by ultrashort laser pulses in an RF photoinjector.

    PubMed

    Musumeci, P; Cultrera, L; Ferrario, M; Filippetto, D; Gatti, G; Gutierrez, M S; Moody, J T; Moore, N; Rosenzweig, J B; Scoby, C M; Travish, G; Vicario, C

    2010-02-26

    In this Letter we report on the use of ultrashort infrared laser pulses to generate a copious amount of electrons by a copper cathode in an rf photoinjector. The charge yield verifies the generalized Fowler-Dubridge theory for multiphoton photoemission. The emission is verified to be prompt using a two pulse autocorrelation technique. The thermal emittance associated with the excess kinetic energy from the emission process is comparable with the one measured using frequency tripled uv laser pulses. In the high field of the rf gun, up to 50 pC of charge can be extracted from the cathode using a 80 fs long, 2 microJ, 800 nm pulse focused to a 140 mum rms spot size. Taking into account the efficiency of harmonic conversion, illuminating a cathode directly with ir laser pulses can be the most efficient way to employ the available laser power. PMID:20366937

  11. Spatial and temporal temperature distribution of ultrashort pulse induced heat accumulation in glass

    NASA Astrophysics Data System (ADS)

    Richter, Sören; Hashimoto, Fumiya; Zimmermann, Felix; Ozeki, Yasuyuki; Itoh, Kazuyoshi; Tünnermann, Andreas; Nolte, Stefan

    2015-03-01

    We report on the first direct measurements of the laser induced temperature distribution after the absorption of multiple ultrashort laser pulses at high repetition rates in borosilicate glass. To this end, we developed an in-situ micro Raman setup to determine the temperature dependent ratio between Stokes and Anti-Stokes scattering. The results indicate a critical influence of the pulse energy on the induced temperature. In borosilicate glass, the maximal temperature directly after the excitation (pulse energy of 1100 nJ, repetition rate of 1 MHz, wavelength of 1044 nm, pulse duration of 600 fs, 2000 pulses per laser spot) is more than 5000 K and rapidly cools down within several hundreds of ns.

  12. Nanosurgery in live cells using ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Heisterkamp, Alexander; Maxwell, Iva Z.; Kumar, Sanjay; Underwood, J. M.; Nickerson, J. A.; Ingber, Donald E.; Mazur, Eric

    2005-04-01

    We selectively disrupted the cytoskeletal network of fixed and live bovine capillary endothelial cell using ultrashort laser pulses. We image the microtubules in the cytoskeleton of the cultured cells using green fluorescent protein. The cells are placed on a custom-built inverted fluorescence microscope setup, using a 1.4 NA oil-immersion objective to both image the cell and focus the laser radiation into the cell samples. The laser delivers 100-fs laser pulses centered at 800 nm at a repetition rate of 1 kHz; the typical energy delivered at the sample is 1-5nJ. The fluorescent image of the cell is captured with a CCD-camera at one frame per second. To determine the spatial discrimination of the laser cutting we ablated microtubules and actin fibers in fixed cells. At pulse energies below 2 nJ we obtain an ablation size of 200 nm. This low pulse energy and high spatial discrimination enable the application of this technique to live cells. We severed a single microtubule inside the live cells without affecting the cell's viability. The targeted microtubule snaps and depolymerizes after the cutting. This nanosurgery technique will further the understanding and modeling of stress and compression in the cytoskeletal network of live cells.

  13. Nonlinear Thomson scattering of an ultrashort laser pulse

    SciTech Connect

    Golovinski, P. A. Mikhin, E. A.

    2011-10-15

    The nonlinear scattering of an ultrashort laser pulse by free electrons is considered. The pulse is described in the 'Mexican hat' wavelet basis. The equation of motion for a charged particle in the field of a plane electromagnetic wave has an exact solution allowing, together with the instant spectrum approximation, the calculation of the intensity of nonlinear Thomson scattering for a high-intensity laser pulse. The spectral distribution of scattered radiation for the entire pulse duration is found by integrating with respect to time. The maximum of the emission spectrum of a free electron calculated in 10{sup 19}-10{sup 21} W/cm{sup 2} fields lies in the UV spectral region between 3 and 12 eV. A part of the continuous spectrum achieves high photon energies. One percent of the scattered energy for the field intensity 10{sup 20} W/cm{sup 2} is concentrated in the range h{omega} > 2.7 Multiplication-Sign 10{sup 2} eV, for a field intensity of 10{sup 21} W/cm{sup 2} in the range h{Omega} > 7.9 Multiplication-Sign 10{sup 2} eV, and for an intensity of 10{sup 22} W/cm{sup 2} in the range h{Omega} > 2.45 Multiplication-Sign 10{sup 5} eV. These results allow us to estimate nonlinear scattering as a source of hard X-rays.

  14. Generation of ultrashort electron bunches by colliding laser pulses

    SciTech Connect

    Schroeder, C.B.; Lee, P.B.; Wurtele, J.S.; Esarey, E.; Leemans, W.P.

    1999-07-01

    A proposed laser-plasma based relativistic electron source [E. Esarey {ital et al.}, Phys. Rev. Lett. {bold 79}, 2682 (1997)] using laser triggered injection of electrons is investigated. The source generates ultrashort electron bunches by dephasing and trapping background plasma electrons undergoing fluid oscillations in an excited plasma wake. The plasma electrons are dephased by colliding two counter-propagating laser pulses which generate a slow phase velocity beat wave. Laser pulse intensity thresholds for trapping and the optimal wake phase for injection are calculated. Numerical simulations of test particles, with prescribed plasma and laser fields, are used to verify analytic predictions and to study the longitudinal and transverse dynamics of the trapped plasma electrons. Simulations indicate that the colliding laser pulse injection scheme has the capability to produce relativistic femtosecond electron bunches with fractional energy spread of order a few percent and normalized transverse emittance less than 1 mm mrad using 1 TW injection laser pulses. {copyright} {ital 1999 American Institute of Physics.}

  15. Generation of ultrashort electron bunches by colliding laser pulses

    SciTech Connect

    Schroeder, C.B.; Lee, P.B.; Wurtele, J.S.; Esarey, E.; Leemans, W.P.

    1999-05-01

    A proposed laser-plasma-based relativistic electron source [E. Esarey {ital et al}., Phys. Rev. Lett. {bold 79}, 2682 (1997)] using laser-triggered injection of electrons is investigated. The source generates ultrashort electron bunches by dephasing and trapping background plasma electrons undergoing fluid oscillations in an excited plasma wake. The plasma electrons are dephased by colliding two counterpropagating laser pulses which generate a slow phase velocity beat wave. Laser pulse intensity thresholds for trapping and the optimal wake phase for injection are calculated. Numerical simulations of test particles, with prescribed plasma and laser fields, are used to verify analytic predictions and to study the longitudinal and transverse dynamics of the trapped plasma electrons. Simulations indicate that the colliding laser pulse injection scheme has the capability to produce relativistic femtosecond electron bunches with fractional energy spread of order a few percent and normalized transverse emittance less than 1 mm mrad using 1 TW injection laser pulses. {copyright} {ital 1999} {ital The American Physical Society}

  16. Ultra-short Pulse Laser Structuring of Molding Tools

    NASA Astrophysics Data System (ADS)

    Conrad, Daniel; Richter, Lars

    The machining of highly filled abrasive polymer plastics in injection molding processes determines high resistant tools in the industrial production. One of the most important points is a long durability of the molding tools to reduce the costs of production. Thus, the adhesion force and abrasion will be reduced with the help of defined surface properties. To achieve appropriate surface conditions, an ultra-short pulse laser is used for a micro structuring. Additional a laser polishing of the micro-structured surfaces to optimize the frictional properties is presented. This paper shows the research results of investigations on the laser modification of steel surfaces, to generate high-quality and wear-resistant surfaces for injection molding tools.

  17. Ultrashort laser pulse shaping for novel light fields and experimental biophysics

    NASA Astrophysics Data System (ADS)

    Rudhall, Andrew Peter

    Broadband spectral content is required to support ultrashort pulses. However this broadband content is subject to dispersion and hence the pulse duration of corresponding ultrashort pulses may be stretched accordingly. I used a commercially-available adaptive ultrashort pulse shaper featuring multiphoton intrapulse interference phase scan technology to characterise and compensate for the dispersion of the optical system in situ and conducted experimental and theoretical studies in various inter-linked topics relating to the light-matter interaction. Firstly, I examined the role of broadband ultrashort pulses in novel light-matter interacting systems involving optically co-trapped particle systems in which inter-particle light scattering occurs between optically-bound particles. Secondly, I delivered dispersion-compensated broadband ultrashort pulses in a dispersive microscope system to investigate the role of pulse duration in a biological light-matter interaction involving laser-induced cell membrane permeabilisation through linear and nonlinear optical absorption. Finally, I examined some of the propagation characteristics of broadband ultrashort pulse propagation using a computer-controlled spatial light modulator. The propagation characteristics of ultrashort pulses is of paramount importance for defining the light-matter interaction in systems. The ability to control ultrashort pulse propagation by using adaptive dispersion compensation enables chirp-free ultrashort pulses to be used in experiments requiring the shortest possible pulses for a specified spectral bandwidth. Ultrashort pulsed beams may be configured to provide high peak intensities over long propagation lengths, for example, using novel beam shapes such as Bessel-type beams, which has applications in biological light-matter interactions including phototransfection based on laser-induced cell membrane permeabilisation. The need for precise positioning of the beam focus on the cell membrane becomes

  18. Photon-induced positron annihilation lifetime spectroscopy using ultrashort laser-Compton-scattered gamma-ray pulses

    SciTech Connect

    Taira, Y.; Toyokawa, H.; Kuroda, R.; Yamamoto, N.; Adachi, M.; Tanaka, S.; Katoh, M.

    2013-05-15

    High-energy ultrashort gamma-ray pulses can be generated via laser Compton scattering with 90 Degree-Sign collisions at the UVSOR-II electron storage ring. As an applied study of ultrashort gamma-ray pulses, a new photon-induced positron annihilation lifetime spectroscopy approach has been developed. Ultrashort gamma-ray pulses with a maximum energy of 6.6 MeV and pulse width of 2.2 ps created positrons throughout bulk lead via pair production. Annihilation gamma rays were detected by a BaF{sub 2} scintillator mounted on a photomultiplier tube. A positron lifetime spectrum was obtained by measuring the time difference between the RF frequency of the electron storage ring and the detection time of the annihilation gamma rays. We calculated the response of the BaF{sub 2} scintillator and the time jitter caused by the variation in the total path length of the ultrashort gamma-ray pulses, annihilation gamma rays, and scintillation light using a Monte Carlo simulation code. The positron lifetime for bulk lead was successfully measured.

  19. Photon-induced positron annihilation lifetime spectroscopy using ultrashort laser-Compton-scattered gamma-ray pulses.

    PubMed

    Taira, Y; Toyokawa, H; Kuroda, R; Yamamoto, N; Adachi, M; Tanaka, S; Katoh, M

    2013-05-01

    High-energy ultrashort gamma-ray pulses can be generated via laser Compton scattering with 90° collisions at the UVSOR-II electron storage ring. As an applied study of ultrashort gamma-ray pulses, a new photon-induced positron annihilation lifetime spectroscopy approach has been developed. Ultrashort gamma-ray pulses with a maximum energy of 6.6 MeV and pulse width of 2.2 ps created positrons throughout bulk lead via pair production. Annihilation gamma rays were detected by a BaF2 scintillator mounted on a photomultiplier tube. A positron lifetime spectrum was obtained by measuring the time difference between the RF frequency of the electron storage ring and the detection time of the annihilation gamma rays. We calculated the response of the BaF2 scintillator and the time jitter caused by the variation in the total path length of the ultrashort gamma-ray pulses, annihilation gamma rays, and scintillation light using a Monte Carlo simulation code. The positron lifetime for bulk lead was successfully measured. PMID:23742543

  20. Photon-induced positron annihilation lifetime spectroscopy using ultrashort laser-Compton-scattered gamma-ray pulses

    NASA Astrophysics Data System (ADS)

    Taira, Y.; Toyokawa, H.; Kuroda, R.; Yamamoto, N.; Adachi, M.; Tanaka, S.; Katoh, M.

    2013-05-01

    High-energy ultrashort gamma-ray pulses can be generated via laser Compton scattering with 90° collisions at the UVSOR-II electron storage ring. As an applied study of ultrashort gamma-ray pulses, a new photon-induced positron annihilation lifetime spectroscopy approach has been developed. Ultrashort gamma-ray pulses with a maximum energy of 6.6 MeV and pulse width of 2.2 ps created positrons throughout bulk lead via pair production. Annihilation gamma rays were detected by a BaF2 scintillator mounted on a photomultiplier tube. A positron lifetime spectrum was obtained by measuring the time difference between the RF frequency of the electron storage ring and the detection time of the annihilation gamma rays. We calculated the response of the BaF2 scintillator and the time jitter caused by the variation in the total path length of the ultrashort gamma-ray pulses, annihilation gamma rays, and scintillation light using a Monte Carlo simulation code. The positron lifetime for bulk lead was successfully measured.

  1. Industrial beam delivery system for ultra-short pulsed laser

    NASA Astrophysics Data System (ADS)

    Funck, Max C.; Wedel, Björn; Kayander, Ilya; Niemeyer, Jörg

    2015-03-01

    Beam delivery systems are an integral part of industrial laser equipment. Separating laser source and application fiber optic beam delivery is employed wherever great flexibility is required. And today, fiber optic beam delivery of several kW average power is available for continuous wave operation using multimode step index fibers with core diameters of several 100 μm. However, during short-pulse or even ultra-short pulse laser operation step index fibers fail due to high power density levels and nonlinear effects such as self-focusing and induced scattering. Hollow core photonic crystal fibers (HC-PCF) are an alternative to traditional fibers featuring light propagation mostly inside a hollow core, enabling high power handling and drastically reduced nonlinear effects. These fibers have become available during the past decade and are used in research but also for fiber laser systems and exhibit a growing popularity. We report on using HC-PCF fibers and their integration into an industrial beam delivery package comparable to today's fiber optic standards and will discuss power handling, beam quality and efficiency as well as future prospects of this technology. In a preliminary industrial beam delivery setup 300 fs pulses at 100 W average power could be delivered.

  2. Dynamics Of Electronic Excitation Of Solids With Ultrashort Laser Pulse

    SciTech Connect

    Medvedev, Nikita; Rethfeld, Baerbel

    2010-10-08

    When ultrashort laser pulses irradiate a solid, photoabsorption by electrons in conduction band produces nonequilibrium highly energetic free electrons gas. We study the ionization and excitation of the electronic subsystem in a semiconductor and a metal (solid silicon and aluminum, respectively). The irradiating femtosecond laser pulse has a duration of 10 fs and a photon energy of h-bar {omega} = 38 eV. The classical Monte Carlo method is extended to take into account the electronic band structure and Pauli's principle for electrons excited to the conduction band. In the case of semiconductors this applies to the holes as well. Conduction band electrons and valence band holes induce secondary excitation and ionization processes which we simulate event by event. We discuss the transient electron dynamics with respect to the differences between semiconductors and metals. For metals the electronic distribution is split up into two branches: a low energy distribution as a slightly distorted Fermi-distribution and a long high energy tail. For the case of semiconductors it is split into two parts by the band gap. To thermalize, these excited electronic subsystems need longer times than the characteristic pulse duration. Therefore, the analysis of experimental data with femtosecond lasers must be based on non-equilibrium concepts.

  3. Laser wakefield acceleration by petawatt ultrashort laser pulses

    SciTech Connect

    Gorbunov, L.M.; Kalmykov, S.Yu.; Mora, P.

    2004-12-07

    An ultra-short (about 30 fs) petawatt laser pulse focused in a wide focal spot (about 100{mu}m) in rarefied plasma (n0 {approx} 1017cm-3) excites a nonlinear plasma wakefield which can accelerate injected electrons up to a GeV energy without pulse channelling. In these conditions, the laser pulse with an over-critical power for relativistic self-focusing propagates as in vacuum. The nonlinear quasi-plane wake plasma wave, whose amplitude and phase velocity vary along the laser path, effectively traps and accelerates injected electrons with a wide range of initial energies. Electrons accelerated along two Rayleigh lengths (about eight centimeters) gain the energy up to 1 GeV. In particular, the electrons trapped from quite a long ({tau}b {approx} 330 fs) non-resonant electron beamlet of 1 MeV particles eventually form a low emittance bunch with the energies in the range 900 {+-} 50 MeV. All these conclusions follow from the two-dimensional simulations performed in cylindrical geometry by fully relativistic time-averaged particle code WAKE.

  4. Precision resection of intestine using ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Beck, Rainer J.; Gora, Wojciech S.; Jayne, David; Hand, Duncan P.; Shephard, Jonathan D.

    2016-03-01

    Endoscopic resection of early colorectal neoplasms typically employs electrocautery tools, which lack precision and run the risk of full thickness thermal injury to the bowel wall with subsequent perforation. We present a means of endoluminal colonic ablation using picosecond laser pulses as a potential alternative to mitigate these limitations. High intensity ultrashort laser pulses enable nonlinear absorption processes, plasma generation, and as a consequence a predominantly non-thermal ablation regimen. Robust process parameters for the laser resection are demonstrated using fresh ex vivo pig intestine samples. Square cavities with comparable thickness to early colorectal neoplasms are removed for a wavelength of 1030 nm and 515 nm using a picosecond laser system. The corresponding histology sections exhibit in both cases only minimal collateral damage to the surrounding tissue. The ablation depth can be controlled precisely by means of the pulse energy. Overall, the application of ultrafast lasers for the resection of intestine enables significantly improved precision and reduced thermal damage to the surrounding tissue compared to conventional electrocautery.

  5. Ultra-short pulsed laser tissue ablation using focused laser beam

    NASA Astrophysics Data System (ADS)

    Jaunich, Megan K.; Raje, Shreya; Mitra, Kunal; Grace, Michael S.; Fahey, Molly; Spooner, Greg

    2008-02-01

    Short pulse lasers are used for a variety of therapeutic applications in medicine. Recently ultra-short pulse lasers have gained prominence due to the reduction in collateral thermal damage to surrounding healthy tissue during tissue ablation. In this paper, ultra-short pulsed laser ablation of mouse skin tissue is analyzed by assessing the extent of damage produced due to focused laser beam irradiation. The laser used for this study is a fiber-based desktop laser (Raydiance, Inc.) having a wavelength of 1552 nm and a pulse width of 1.3 ps. The laser beam is focused on the sample surface to a spot size on the order of 10 microns, thus producing high peak intensity necessary for precise clean ablation. A parametric study is performed on in vitro mouse tissue specimens and live anaesthetized mice with mammary tumors through variation of laser parameters such as time-averaged laser power, repetition rate, laser scanning rate and irradiation time. Radial temperature distribution is measured using thermal camera to analyze the heat affected zone. Temperature measurements are performed to assess the peak temperature rise attained during ablation. A detailed histological study is performed using frozen section technique to observe the nature and extent of laser-induced damages.

  6. Formation of ultrashort electron pulses in an electrostatic laser reflectron-deflector

    SciTech Connect

    Aseev, S A; Mironov, B N; Chekalin, S V; Minogin, V G

    2014-03-28

    The temporal compression of photoelectron pulses obtained by irradiation of the target by femtosecond electron pulses is analysed by using an electrostatic reflectron with a deflecting pulse laser field. It is shown that the use of a reflectron-deflector allows one both to generate and deflect ultrashort, ∼30-fs electron pulses with a countable number of electrons by focusing them into a given region with a focal size about tens of microns. It is found that the laser ponderomotive potential can play a role of a dispersive element in the electrostatic reflectron to spatially separate the electron pulses with different energies. (ultrashort electron pulses)

  7. Atomic processes in plasmas created by an ultra-short laser pulse

    NASA Astrophysics Data System (ADS)

    Audebert, P.; Lecherbourg, L.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Blancard, C.; Cossé, P.; Faussurier, G.; Shepherd, R.; Renaudin, P.

    2008-05-01

    Point projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient aluminum plasma created by an ultra-short laser pulse. 1s-2p and 1s-3p absorption lines of weakly ionized aluminum were measured for an extended range of densities in a relatively low-temperature regime. Independent plasma characterization was obtained from frequency domain interferometry (FDI) diagnostic and allows the interpretation of the absorption spectra in terms of spectral opacities. The experimental spectra are compared with opacity calculations using the density and temperature inferred from the analysis of the FDI data.

  8. Electron-beam-based sources of ultrashort x-ray pulses

    SciTech Connect

    Zholents, A. )

    2010-01-01

    A review of various methods for generation of ultrashort X-ray pulses using relativistic electron beam from conventional accelerators is presented. Both spontaneous and coherent emission of electrons are considered.

  9. Thin film surface processing by ultrashort laser pulses (USLP)

    NASA Astrophysics Data System (ADS)

    Scorticati, D.; Skolski, J. Z. P.; Römer, G. R. B. E.; Huis in't Veld, A. J.; Workum, M.; Theelen, M.; Zeman, M.

    2012-06-01

    In this work, we studied the feasibility of surface texturing of thin molybdenum layers on a borosilicate glass substrate with Ultra-Short Laser Pulses (USLP). Large areas of regular diffraction gratings were produced consisting of Laserinduced periodic surface structures (LIPSS). A short pulsed laser source (230 fs-10 ps) was applied using a focused Gaussian beam profile (15-30 μm). Laser parameters such as fluence, overlap (OL) and Overscans (OS), repetition frequency (100-200 kHz), wavelength (1030 nm, 515 nm and 343 nm) and polarization were varied to study the effect on periodicity, height and especially regularity of LIPSS obtained in layers of different thicknesses (150-400 nm). The aim was to produce these structures without cracking the metal layer and with as little ablation as possible. It was found that USLP are suitable to reach high power densities at the surface of the thin layers, avoiding mechanical stresses, cracking and delamination. A possible photovoltaic (PV) application could be found in texturing of thin film cells to enhance light trapping mechanisms.

  10. Holographic frequency resolved optical gating for spatio-temporal characterization of ultrashort optical pulse

    NASA Astrophysics Data System (ADS)

    Mehta, Nikhil; Yang, Chuan; Xu, Yong; Liu, Zhiwen

    2014-09-01

    We introduce a novel method for characterizing the spatio-temporal evolution of ultrashort optical field by recording the spectral hologram of frequency resolved optical gating (FROG) trace. We show that FROG holography enables the measurement of phase (up to an overall constant) and group delay of the pulse which cannot be measured by conventional FROG method. To illustrate our method, we perform numerical simulation to generate holographic collinear FROG (cFROG) trace of a chirped optical pulse and retrieve its complex profile at multiple locations as it propagates through a hypothetical dispersive medium. Further, we experimentally demonstrate our method by retrieving a 67 fs pulse at three axial locations in the vicinity of focus of an objective lens and compute its group delay.

  11. Bone tissue heating and ablation by short and ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Letfullin, Renat R.; Rice, Colin E. W.; George, Thomas F.

    2010-02-01

    Biological hard tissues, such as those found in bone and teeth, are complex tissues that build a strong mineral structure over an organic matrix framework. The laser-matter interaction for bone hard tissues holds great interest to laser surgery and laser dentistry; the use of short/ultrashort pulses, in particular, shows interesting behaviors not seen in continuous wave lasers. High laser energy densities in ultrashort pulses can be focused on a small irradiated surface (spot diameter is 10-50 μm) leading to rapid temperature rise and thermal ablation of the bone tissue. Ultrashort pulses, specifically those in the picosecond and femtosecond ranges, impose several challenges in modeling bone tissue response. In the present paper we perform time-dependent thermal simulations of short and ultrashort pulse laser-bone interactions in singlepulse and multipulse (set of ultrashort pulses) modes of laser heating. A comparative analysis for both radiation modes is discussed for laser heating of different types of the solid bone on the nanosecond, picosecond and femtosecond time scales. It is shown that ultrashort laser pulses with high energy densities can ablate bone tissue without heating tissues bordering the ablation creator. This reaction is particularly desirable as heat accumulation and thermal damage are the main factors affecting tissue regrowth rates, and thus patient recovery times.

  12. Ion acceleration in underdense plasmas by ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Lifschitz, A.; Sylla, F.; Kahaly, S.; Flacco, A.; Veltcheva, M.; Sanchez-Arriaga, G.; Lefebvre, E.; Malka, V.

    2014-03-01

    We report on the ion acceleration mechanisms that occur during the interaction of an intense and ultrashort laser pulse (I\\lambda^{2}>10^{18} \\text{W}\\,\\text{cm}^{-2}\\,\\mu \\text{m}^{2}) with an underdense helium plasma produced from an ionized gas jet target. In this unexplored regime, where the laser pulse duration is comparable to the inverse of the electron plasma frequency {{\\omega }_{pe}}, reproducible non-thermal ion bunches have been measured in the radial direction. The two He ion charge states present energy distributions with cutoff energies between 150 and 200 keV, and a striking energy gap around 50 keV appearing consistently for all the shots in a given density range. Fully electromagnetic particle-in-cell simulations explain the experimental behaviors. The acceleration results from a combination of target normal sheath acceleration and Coulomb explosion of a filament formed around the laser pulse propagation axis.

  13. Thin-disk multipass amplifier for ultrashort laser pulses with kilowatt average output power and mJ pulse energies

    NASA Astrophysics Data System (ADS)

    Negel, Jan-Philipp; Voss, Andreas; Abdou Ahmed, Marwan; Bauer, Dominik; Sutter, Dirk; Killi, Alexander; Graf, Thomas

    2014-05-01

    We report on a Yb:YAG thin-disk multipass amplifier for ultrashort laser pulses delivering an average output power of 1.1 kW which to the best of our knowledge is the highest output power reported from such a system so far. A modified commercial TruMicro5050 laser delivers the seed pulses with an average power of 80 W at a wavelength of 1030 nm, a pulse duration of 6.5 ps and a repetition rate of 800 kHz. These pulses are amplified to 1.38 mJ of pulse energy with a duration of 7.3 ps. To achieve this, we developed a scheme in which an array of 40 plane mirrors is used to geometrically fold the seed beam over the pumped thin-disk crystal. Exploiting the incoming linear polarization, an overall number of 40 double-passes through the disk was realized by using the backpath through the amplifier with the orthogonal linear polarization state. Thermal issues on the disk were mitigated by zero-phonon line pumping at a wavelength of 969 nm directly into the upper laser level and by employing a retroreflective mirror pair. The amplifier exhibits an optical efficiency of 44 % and a slope efficiency of 46 %. The beam quality was measured to be better than M2=1.25 at all power levels. As this system can deliver high pulse energies and high average output powers at the same time without the need of a CPA technique, it can be very suitable for high productivity material processing with ultrashort laser pulses.

  14. Fibre laser with a subterahertz repetition rate of ultrashort pulses in the telecom range

    NASA Astrophysics Data System (ADS)

    Andrianov, A. V.; Mylnikov, V. M.; Koptev, M. Yu; Muravyev, S. V.; Kim, A. V.

    2016-04-01

    We have investigated a new fibre laser configuration for the generation of ultrashort pulses at a repetition rate far exceeding the fundamental cavity frequency. The laser configuration includes a nonlinear amplifying mirror as an artificial saturable absorber for mode locking and a spectral comb filter for pulse separation stabilisation. Generation of trains and sequences of ultrashort pulses at a repetition rate tunable in the range 8 – 200 GHz has been demonstrated experimentally. The pulses generated by the laser have been shown to retain an ordered, equidistant structure on a nanosecond timescale.

  15. Scattering of an ultrashort electromagnetic radiation pulse by an atom in a broad spectral range

    SciTech Connect

    Astapenko, V. A.

    2011-02-15

    The scattering of an ultrashort electromagnetic pulse by atomic particles is described using a consistent quantum-mechanical approach taking into account excitation of a target and nondipole electromagnetic interaction, which is valid in a broad spectral range. This approach is applied to the scattering of single- and few-cycle pulses by a multielectron atom and a hydrogen atom. Scattering spectra are obtained for ultrashort pulses of different durations. The relative contribution of 'elastic' scattering of a single-cycle pulse by a hydrogen atom is studied in the high-frequency limit as a function of the carrier frequency and scattering angle.

  16. Ultra-short laser pulse generated by a microring resonator system for cancer cell treatment.

    PubMed

    Jalil, M A; Ong, C T; Saktioto, T; Daud, S; Aziz, M S; Yupapin, P P

    2013-06-01

    A microring resonator (MRRs) system incorporated with a add/drop filter is proposed in which ultra-short single, multi-temporal, and spatial optical soliton pulses are simulated and used to kill abnormal cells, tumors, and cancer. Chaotic signals are generated by a bright soliton pulse within a nonlinear MRRs system. Gold nanoparticles and ultra-short femtosecond/picosecond laser pulses' interaction holds great interest in laser nanomedicine. By using appropriate soliton input power and MRRs parameters, desired spatial and temporal signals can be generated over the spectrum. Results show that short temporal and spatial solitons pulse with FWHM = 712 fs and FWHM = 17.5 pm could be generated. The add/drop filter system is used to generate the high-capacity, ultra-short soliton pulses in the range of nanometer/second and picometer/second. PMID:22947143

  17. Ultrashort pulse high intensity laser illumination of a simple metal

    NASA Astrophysics Data System (ADS)

    Milchberg, H. M.; Freeman, R. R.; Davey, S. C.

    1988-10-01

    We have observed the self-reflection of intense, sub-picosecond 308 nm light pulse incident on a planar Al target and have inferred the electrical conductivity of solid density Al. The pulse lengths were sufficiently short that no significant expansion of the target occurred during the measurement.

  18. Novel oral applications of ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Wieger, V.; Wernisch, J.; Wintner, E.

    2007-02-01

    In the past decades, many efforts have been made to replace mechanical tools in oral applications by various laser systems. The reasons therefore are manifold: i) Friction causes high temperatures damaging adjacent tissue. ii) Smear layers and rough surfaces are produced. iii) Size and shape of traditional tools are often unsuitable for geometrically complicated incisions and for minimum invasive treatment. iv) Mechanical damage of the remaining tissue occurs. v) Online diagnosis for feedback is not available. Different laser systems in the µs and sub-&mrgs-pulse regime, among them Erbium lasers, have been tested in the hope to overcome the mentioned drawbacks and, to some extent, they represent the current state of the art with respect to commercial and hence practical application. In the present work the applicability of scanned ultrashort pulse lasers (USPLs) for biological hard tissue as well as dental restoration material removal was tested. It is shown that cavities with features superior to mechanically treated or Erbium laser ablated cavities can be generated if appropriate scan algorithms and optimum laser parameters are matched. Smooth cavity rims, no microcracks, melting or carbonisation and precise geometry are the advantages of scanned USLP ablation. For bone treatment better healing conditions are expected as the natural structure remains unaffected by the preparation procedure. The novelty of this work is represented by a comprehensive compilation of various experimental results intended to assess the performance of USPLs. In this context, various pulse durations in the picosecond and femtosecond regime were applied to dental and bone tissue as well as dental restoration materials which is considered to be indispensable for a complete assessment. Parameters like ablation rates describing the efficiency of the ablation process, and ablation thresholds were determined - some of them for the first time - and compared to the corresponding Erbium

  19. Hydrodynamic model for ultra-short pulse ablation of hard dental tissue

    SciTech Connect

    London, R.A.; Bailey, D.S.; Young, D.A.; Alley, W.E.; Feit, M.D.; Rubenchik, A.M.; Neev, J.

    1996-02-29

    A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 fsec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

  20. Interplay of diffraction and nonlinear effects in the propagation of ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Korpa, C. L.; Tóth, Gy; Hebling, J.

    2016-02-01

    We investigate the interplay of diffraction and nonlinear effects during the propagation of very short light pulses. Adapting the factorization approach to the problem at hand by keeping the transverse-derivative terms apart from the residual nonlinear contributions we derive an unidirectional propagation equation which is valid for weak dispersion and reduces to the slowly-evolving-wave-approximation in the case of paraxial rays. A comparison of the numerical simulation results for the two equations shows pronounced differences when self-focusing plays an important role. We devote special attention to modelling the propagation of ultrashort terahertz pulses taking into account diffraction as well as Kerr-type and second-order nonlinearities. Comparing the measured and simulated wave forms we deduce the value of the nonlinear refractive index of lithium niobate in the terahertz region to be three orders of magnitude larger than in the visible part of the spectrum.

  1. Detector response to high repetition rate ultra-short laser pulses. I

    NASA Astrophysics Data System (ADS)

    Zakharova, I. K.; Rafailov, Michael K.

    2015-05-01

    Optical nonlinearities in semiconductors and semiconductor detectors have been widely investigated and exploited for many scientific and industrial applications. The correlation of optical and electronic characteristics in these detector materials under exposure of ultra-short laser pulses at high pulse repetition rates is still not very well known. These effects may be quite beneficial for many applications ranging from chemical and biological sensing to light-induced superconductivity. In this paper, we discuss the effect of extended bleaching in order to demonstrate sensing applications of such phenomenon as an example. Pump-probe measurements in bulk semiconductors will be presented to quantify the transient absorption dynamics and relate this to the electronic response of the detector devices. This effect is not limited semiconductors and may affect other matter states and electronic structures, like dielectrics.

  2. Self-limited underdense microplasmas in bulk silicon induced by ultrashort laser pulses

    SciTech Connect

    Mouskeftaras, Alexandros; Clady, Raphaël; Sentis, Marc; Utéza, Olivier; Grojo, David; Rode, Andrei V.

    2014-11-10

    Two-photon ionization by focused femtosecond laser pulses initiates the development of micrometer-scale plasmas in the bulk of silicon. Using pump-and-probe transmission microscopy with infrared light, we investigate the space-time characteristics of these plasmas for laser intensities up to 10{sup 12 }W/cm{sup 2}. The measurements reveal a self-limitation of the excitation at a maximum free-carrier density of ≅10{sup 19 }cm{sup −3}, which is more than one order of magnitude below the threshold for permanent modification. The plasmas remain unchanged in the ∼100 ps timescale revealing slow carrier kinetics. The results underline the limits in local control of silicon dielectric permittivity, which are inherent to the use of single near-infrared ultrashort Gaussian pulses.

  3. Generation of circularly polarized attosecond pulses by intense ultrashort laser pulses from extended asymmetric molecular ions

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Bandrauk, André D.

    2011-08-01

    We present a method for generation of single circularly polarized attosecond pulses in extended asymmetric HHe2+ molecular ions. By employing an intense ultrashort circularly polarized laser pulse with intensity 4.0×1014 W/cm2, wavelength 400 nm, and duration 10 optical cycles, molecular high-order-harmonic generation (MHOHG) spectra with multiple plateaus exhibit characters of circular polarization. Using a classical laser-induced collision model, double collisions of continuum electrons first with neighboring ions and then second with parent ions are presented at a particular internuclear distance and confirmed from numerical solutions of a time-dependent Schrödinger equation. We analyze the MHOHG spectra with a Gabor time window and find that, due to the asymmetry of HHe2+, a single collision trajectory of continuum electrons with ions can produce circularly polarized harmonics, leading to single circularly polarized attosecond pulses for specific internuclear distances.

  4. Generation of circularly polarized attosecond pulses by intense ultrashort laser pulses from extended asymmetric molecular ions

    SciTech Connect

    Yuan, Kai-Jun; Bandrauk, Andre D.

    2011-08-15

    We present a method for generation of single circularly polarized attosecond pulses in extended asymmetric HHe{sup 2+} molecular ions. By employing an intense ultrashort circularly polarized laser pulse with intensity 4.0x10{sup 14} W/cm{sup 2}, wavelength 400 nm, and duration 10 optical cycles, molecular high-order-harmonic generation (MHOHG) spectra with multiple plateaus exhibit characters of circular polarization. Using a classical laser-induced collision model, double collisions of continuum electrons first with neighboring ions and then second with parent ions are presented at a particular internuclear distance and confirmed from numerical solutions of a time-dependent Schroedinger equation. We analyze the MHOHG spectra with a Gabor time window and find that, due to the asymmetry of HHe{sup 2+}, a single collision trajectory of continuum electrons with ions can produce circularly polarized harmonics, leading to single circularly polarized attosecond pulses for specific internuclear distances.

  5. Industrial grade fiber-coupled laser systems delivering ultrashort high-power pulses for micromachining

    NASA Astrophysics Data System (ADS)

    Pricking, Sebastian; Welp, Petra; Overbuschmann, Johannes; Nutsch, Sebastian; Gebs, Raphael; Fleischhaker, Robert; Kleinbauer, Jochen; Wolf, Martin; Budnicki, Aleksander; Sutter, Dirk H.; Killi, Alexander; Mielke, Michael

    2016-03-01

    We report on an industrial fiber-delivered laser system producing ultra-short pulses in the range of a few picoseconds down to a few hundred femtoseconds with high average power suitable for high-precision micromachining. The delivery fiber is a hollow-core photonic crystal fiber with a Kagomé shaped lattice and a hypocycloid core wall enabling the guiding of laser radiation over several meters with exceptionally low losses and preservation of high beam quality (M2<1.3). The mode-matching and coupling optics are integrated into the laser head providing a compact footprint without the need for external boxes. The laser head is carefully designed regarding its thermo-mechanical properties to allow a highly reliable coupling stability. The exchangeable delivery fiber is packaged using Trumpf's well established LLK-D connectors which offer a very high mechanical precision, the possibility to add water cooling, as well as full featured safety functions. The fiber is hermetically sealed and protected by a robust but flexible shield providing bend protection and break detection. We show the linear and nonlinear optical properties of the transported laser radiation and discuss its feasibility for pulse compression. Measurements are supported by simulation of pulse propagation by solving the nonlinear Schrödinger equation implementing the split-step Fourier method. In addition, mode properties are measured and confirmed by finite element method simulations. The presented industrial laser system offers the known advantages of ultra-short pulses combined with the flexibility of fiber delivery yielding a versatile tool perfectly suitable for all kinds of industrial micromachining applications.

  6. Generation of an ultra-short electrical pulse with width shorter than the excitation laser.

    PubMed

    Shi, Wei; Wang, Shaoqiang; Ma, Cheng; Xu, Ming

    2016-01-01

    We demonstrate experimentally a rare phenomenon that the width of an electrical response is shorter than that of the excitation laser. In this work, generation of an ultrashort electrical pulse is by a semi-insulating GaAs photoconductive semiconductor switch (PCSS) and the generated electrical pulse width is shorter than that of the excitation laser from diode laser. When the pulse width and energy of the excitation laser are fixed at 25.7 ns and 1.6 μJ respectively, the width of the generated electrical pulse width by 3-mm-gap GaAs PCSS at the bias voltage of 9 kV is only 7.3 ns. The model of photon-activated charge domain (PACD) is used to explain the peculiar phenomenon in our experiment. The ultrashort electrical pulse width is mainly relevant to the time interval of PACD from occurrence to disappearance in the mode. The shorter the time interval is, the narrower the electrical pulse width will become. In more general terms, our result suggests that in nonlinear regime a response signal can have a much short width than the excitation pulses. The result clearly indicates that generating ultrashort electrical pulses can be achieved without the need of ultrashort lasers. PMID:27273512

  7. Generation of an ultra-short electrical pulse with width shorter than the excitation laser

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Wang, Shaoqiang; Ma, Cheng; Xu, Ming

    2016-06-01

    We demonstrate experimentally a rare phenomenon that the width of an electrical response is shorter than that of the excitation laser. In this work, generation of an ultrashort electrical pulse is by a semi-insulating GaAs photoconductive semiconductor switch (PCSS) and the generated electrical pulse width is shorter than that of the excitation laser from diode laser. When the pulse width and energy of the excitation laser are fixed at 25.7 ns and 1.6 μJ respectively, the width of the generated electrical pulse width by 3-mm-gap GaAs PCSS at the bias voltage of 9 kV is only 7.3 ns. The model of photon-activated charge domain (PACD) is used to explain the peculiar phenomenon in our experiment. The ultrashort electrical pulse width is mainly relevant to the time interval of PACD from occurrence to disappearance in the mode. The shorter the time interval is, the narrower the electrical pulse width will become. In more general terms, our result suggests that in nonlinear regime a response signal can have a much short width than the excitation pulses. The result clearly indicates that generating ultrashort electrical pulses can be achieved without the need of ultrashort lasers.

  8. Generation of an ultra-short electrical pulse with width shorter than the excitation laser

    PubMed Central

    Shi, Wei; Wang, Shaoqiang; Ma, Cheng; Xu, Ming

    2016-01-01

    We demonstrate experimentally a rare phenomenon that the width of an electrical response is shorter than that of the excitation laser. In this work, generation of an ultrashort electrical pulse is by a semi-insulating GaAs photoconductive semiconductor switch (PCSS) and the generated electrical pulse width is shorter than that of the excitation laser from diode laser. When the pulse width and energy of the excitation laser are fixed at 25.7 ns and 1.6 μJ respectively, the width of the generated electrical pulse width by 3-mm-gap GaAs PCSS at the bias voltage of 9 kV is only 7.3 ns. The model of photon-activated charge domain (PACD) is used to explain the peculiar phenomenon in our experiment. The ultrashort electrical pulse width is mainly relevant to the time interval of PACD from occurrence to disappearance in the mode. The shorter the time interval is, the narrower the electrical pulse width will become. In more general terms, our result suggests that in nonlinear regime a response signal can have a much short width than the excitation pulses. The result clearly indicates that generating ultrashort electrical pulses can be achieved without the need of ultrashort lasers. PMID:27273512

  9. Optical Field Ionization of Atoms and Ions Using Ultrashort Laser Pulses

    NASA Astrophysics Data System (ADS)

    Fittinghoff, David Neal

    This dissertation research is an investigation of the strong optical field ionization of atoms and ions by 120-fs, 614-nm 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^{+1} and Ar^{+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: (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-nm 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 (number of ions produced versus irradiance) for three noble gases using linear, circular and elliptical polarizations of laser pulses.

  10. Ablation enhancement of silicon by ultrashort double-pulse laser ablation

    SciTech Connect

    Zhao, Xin; Shin, Yung C.

    2014-09-15

    In this study, the ultrashort double-pulse ablation of silicon is investigated. An atomistic simulation model is developed to analyze the underlying physics. It is revealed that the double-pulse ablation could significantly increase the ablation rate of silicon, compared with the single pulse ablation with the same total pulse energy, which is totally different from the case of metals. In the long pulse delay range (over 1 ps), the enhancement is caused by the metallic transition of melted silicon with the corresponding absorption efficiency. At ultrashort pulse delay (below 1 ps), the enhancement is due to the electron excitation by the first pulse. The enhancement only occurs at low and moderate laser fluence. The ablation is suppressed at high fluence due to the strong plasma shielding effect.

  11. Melanin and the cellular effects of ultrashort-pulse, near-infrared laser radiation

    NASA Astrophysics Data System (ADS)

    Glickman, Randolph D.; Kumar, Neeru; Rockwell, Benjamin A.; Noojin, Gary D.; Denton, Michael L.; Stolarski, David J.

    2003-07-01

    Our research into laser bioeffects has increasingly focused on cytotoxic mechanisms affecting genomic expression and programmed cellular stress responses. In the context of DNA damage, we previously reported that more DNA strand breaks were produced in cultured retinal pigment epithelium (RPE) cells exposed to ultrashort pulse, than to CW, near-infrared (NIR) laser radiation. To test the hypothesis that RPE melanin was the cellular chromophore responsible for mediating this damage, the experiments were repeated with a line of human-derived RPE cells that could be grown in culture expressing varying levels of pigmentation. Lightly-pigmented cells were either unexposed, or exposed to the output of a Ti:Sapphire laser producing 810 nm light in mode-locked pulses (48-fsec at 80 MHz), or as CW radiation. Cells were irradiated at 160 W/cm2 or 80 W/cm2 (the estimated ED50 or half-ED50 for a retinal lesion). Immediately following the laser exposure, cells were processed for the comet assay. Longer "comet" tails and larger "comet" areas indicated more DNA strand breaks. In lightly-pigmented RPE cells, the overall comet assay differences among the laser-exposed groups were smaller than those observed in our earlier experiments which utilized highly pigmented primary cells. The comet tail lengths of cells exposed to the mode-locked pulses at the ED50, however, were significantly longer than those of the controls or the CW-exposed cells. The other comet assay parameters examined (tail moment, comet area) did not show consistent differences among the groups. While these results support the involvement of melanin in the ultrashort pulse laser-induced damage to DNA, they do not exclude the involvement of other cellular chromophores. Some preliminary experiments describing other measures of cellular stress responses to laser-induced oxidative stress are described.

  12. Formation of plasma channels in air under filamentation of focused ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Ionin, A. A.; Seleznev, L. V.; Sunchugasheva, E. S.

    2015-03-01

    The formation of plasma channels in air under filamentation of focused ultrashort laser pulses was experimentally and theoretically studied together with theoreticians of the Moscow State University and the Institute of Atmospheric Optics. The influence of various characteristics of ultrashort laser pulses on these plasma channels is discussed. Plasma channels formed under filamentation of focused laser beams with a wavefront distorted by spherical aberration (introduced by adaptive optics) and by astigmatism, with cross-section spatially formed by various diaphragms and with different UV and IR wavelengths, were experimentally and numerically studied. The influence of plasma channels created by a filament of a focused UV or IR femtosecond laser pulse (λ = 248 nm or 740 nm) on characteristics of other plasma channels formed by a femtosecond pulse at the same wavelength following the first one with varied nanosecond time delay was also experimentally studied. An application of plasma channels formed due to the filamentation of focused UV ultrashort laser pulses including a train of such pulses and a combination of ultrashort and long (~100 ns) laser pulses for triggering and guiding long (~1 m) electric discharges is discussed.

  13. Reflectivity of plasmas created by high-intensity, ultra-short laser pulses

    SciTech Connect

    Gold, D.M.

    1994-06-01

    Experiments were performed to characterize the creation and evolution of high-temperature (T{sub e}{approximately}100eV), high-density (n{sub e}>10{sup 22}cm{sup {minus}3}) plasmas created with intense ({approximately}10{sup 12}-10{sup 16}W/cm{sup 2}), ultra-short (130fs) laser pulses. The principle diagnostic was plasma reflectivity at optical wavelengths (614nm). An array of target materials (Al, Au, Si, SiO{sub 2}) with widely differing electronic properties tested plasma behavior over a large set of initial states. Time-integrated plasma reflectivity was measured as a function of laser intensity. Space- and time-resolved reflectivity, transmission and scatter were measured with a spatial resolution of {approximately}3{mu}m and a temporal resolution of 130fs. An amplified, mode-locked dye laser system was designed to produce {approximately}3.5mJ, {approximately}130fs laser pulses to create and nonintrusively probe the plasmas. Laser prepulse was carefully controlled to suppress preionization and give unambiguous, high-density plasma results. In metals (Al and Au), it is shown analytically that linear and nonlinear inverse Bremsstrahlung absorption, resonance absorption, and vacuum heating explain time-integrated reflectivity at intensities near 10{sup 16}W/cm{sup 2}. In the insulator, SiO{sub 2}, a non-equilibrium plasma reflectivity model using tunneling ionization, Helmholtz equations, and Drude conductivity agrees with time-integrated reflectivity measurements. Moreover, a comparison of ionization and Saha equilibration rates shows that plasma formed by intense, ultra-short pulses can exist with a transient, non-equilibrium distribution of ionization states. All targets are shown to approach a common reflectivity at intensities {approximately}10{sup 16}W/cm{sup 2}, indicating a material-independent state insensitive to atomic or solid-state details.

  14. X-Ray Absorption Spectroscopy Of Thin Foils Irradiated By An Ultra-short Laser Pulse

    SciTech Connect

    Renaudin, P.; Blancard, C.; Cosse, P.; Faussurier, G.; Lecherbourg, L.; Audebert, P.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Shepherd, R.

    2007-08-02

    Point-projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient plasma created by an ultra-short laser pulse. The 1s-2p and 1s-3p absorption lines of weakly ionized aluminum and the 2p-3d absorption lines of bromine were measured over an extended range of densities in a low-temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. Assuming local thermodynamic equilibrium, spectral opacity calculations have been performed using the density and temperature inferred from the FDI diagnostic to compare to the measured absorption spectra. A good agreement is obtained when non-equilibrium effects due to non-stationary atomic physics are negligible at the x-ray probe time.

  15. X-Ray Absorption Spectroscopy Of Thin Foils Irradiated By An Ultra-short Laser Pulse

    NASA Astrophysics Data System (ADS)

    Renaudin, P.; Lecherbourg, L.; Blancard, C.; Cossé, P.; Faussurier, G.; Audebert, P.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Shepherd, R.

    2007-08-01

    Point-projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient plasma created by an ultra-short laser pulse. The 1s-2p and 1s-3p absorption lines of weakly ionized aluminum and the 2p-3d absorption lines of bromine were measured over an extended range of densities in a low-temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. Assuming local thermodynamic equilibrium, spectral opacity calculations have been performed using the density and temperature inferred from the FDI diagnostic to compare to the measured absorption spectra. A good agreement is obtained when non-equilibrium effects due to non-stationary atomic physics are negligible at the x-ray probe time.

  16. Precision drilling of metals and ceramics with short- and ultrashort-pulsed solid state lasers

    NASA Astrophysics Data System (ADS)

    Foehl, Christian; Breitling, Detlef; Jasper, Knut; Radtke, Joachim; Dausinger, Friedrich

    2002-02-01

    At the end of 1999 a German National Project called PRIMUS was established, the most important aim of which is to analyze the potential advantages of ultrashort pulses in combination with different drilling strategies and to obtain a better understanding of the ablation and drilling processes. This contribution will present the first results of this project. The advantages of short and ultrashort pulses in view of quality and efficiency will be discussed. It will be shown, that the use of suitable drilling technologies, such as e.g. helical drilling, and a specifically designed trepanning optic can significantly increase the quality of holes as well as expand the possible range of applications.

  17. Full-wave simulations on ultrashort-pulse reflectometry for helical plasmas

    SciTech Connect

    Hojo, H.; Fukuchi, A.; Itakura, A.; Mase, A.

    2004-10-01

    The full-wave simulations on ultrashort-pulse reflectometry for helical plasmas are studied based on the FDTD method in two dimensions. The propagation of an ultrashort-pulse electromagnetic wave is computed in helical plasmas modeled for the Large Helical Device magnetic field configuration. The density-profile reconstruction is performed by the Abel inversion method with the time delay data for the reflected waves from plasma, and it is shown that the reconstructed density profile coincides well with the original profile.

  18. Calculus removal on a root cement surface by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Kraft, Johan F.; Vestentoft, Kasper; Christensen, Bjarke H.; Løvschall, Henrik; Balling, Peter

    2008-01-01

    Ultrashort-pulse-laser ablation of dental calculus (tartar) and cement is performed on root surfaces. The investigation shows that the threshold fluence for ablation of calculus is a factor of two to three times smaller than that of a healthy root cement surface. This indicates that ultrashort laser pulses may provide an appropriate tool for selective removal of calculus with minimal damage to the underlying root cement. Future application of an in situ profiling technique allows convenient on-line monitoring of the ablation process.

  19. Space charge limited electron emission from a Cu surface under ultrashort pulsed laser irradiation

    SciTech Connect

    Wendelen, W.; Autrique, D.; Bogaerts, A.

    2010-10-08

    In this theoretical study, the electron emission from a copper surface under ultrashort pulsed laser irradiation is investigated using a one dimensional particle in cell model. Thermionic emission as well as multi-photon photoelectron emission were taken into account. The emitted electrons create a negative space charge above the target, consequently the generated electric field reduces the electron emission by several orders of magnitude. The simulations indicate that the space charge effect should be considered when investigating electron emission related phenomena in materials under ultrashort pulsed laser irradiation of metals.the word ''abstract,'' but do replace the rest of this text.

  20. Characterization of ultrashort pulse laser-produced miniature hohlraum XUV sources

    NASA Astrophysics Data System (ADS)

    McKelvey, Andrew; Raymond, Anthony; Zulick, Calvin; Maksimchuk, Anatoly; Nees, John; Yanovsky, Victor; Chvykov, Vladimir; Thomas, Alexander; Krushelnick, Karl

    2014-10-01

    Experiments at the National Ignition Facility (NIF) allow the radiative properties of dense, high-temperature matter to be studied at previously unreachable regimes, but are limited by cost and system availability. A scaled down system using ultra-short laser pulses and delivering energy to a much smaller hohlraum could be capable of reaching comparable energy densities by depositing the energy in a significantly smaller volume before ablation of the wall material closes the cavity. The laser is tightly focused through the cavity and then expands to illuminate the wall with an intensity closer to that of a long pulse laser. Experiments were performed on a number of short-pulse Ti:sapphire tabletop laser systems. Targets include cavities machined in bulk material using low laser powers, and then shot in situ with a single full power pulse as well as micron scale pre-fabricated targets. Spectral characteristics were measured using a flat-field soft X-ray spectrometer and a seven channel filtered photo cathode array. These broadband EUV sources may allow opacity and atomic physics measurements with plasma and radiation temperatures comparable to NIF type hohlraums, but with a significantly higher repetition rate and in a university scale system.

  1. Guiding of high intensity ultrashort laser pulses in plasma channels produced with the dual laser pulse ignitor-heater technique

    SciTech Connect

    Volfbeyn, P.; Leemans, W.P.

    1998-07-01

    The authors present results of experimental investigations of laser guiding in plasma channels. A new technique for plasma channel creation, the Ignitor-Heater scheme is proposed and experimentally tested in hydrogen and nitrogen. It makes use of two laser pulses. The Ignitor, an ultrashort (< 100 fs) laser pulse, is brought to a line focus using a cylindrical lens to ionize the gas. The Heater pulse (160 ps long) is used subsequently to heat the existing spark via inverse Bremsstrahlung. The hydrodynamic shock expansion creates a partially evacuated plasma channel with a density minimum on axis. Such a channel has properties of an optical waveguide. This technique allows creation of plasma channels in low atomic number gases, such as hydrogen, which is of importance for guiding of highly intense laser pulses. The channel density was diagnosed with time resolved longitudinal interferometry. From these measurements the plasma temperature was inferred. The guiding properties of the channels were tested by injecting a > 5 {times} 10{sup 17} W/cm{sup 2}, 75 fs laser pulse.

  2. Optical field ionization of atoms and ions using ultrashort laser pulses

    SciTech Connect

    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{sup +2}, Ne{sup +2} and Ar{sup +2}. The ion yields for He{sup +l}, Ne{sup +l} and Ar{sup +l} 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: (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.

  3. Application of time gating in the measurement of glucose level in a three-layer biotissue model by using ultrashort laser pulses

    SciTech Connect

    Kirillin, M Yu; Bykov, A V; Priezzhev, A V; Myllylae, R

    2008-05-31

    The efficiency of using the time-of-flight (TOF) method at a wavelength of 820 nm for detecting the changes in the optical properties of multilayer light scattering medium in connection with the problem of the glucose level detection in the human tissue is discussed. Pulses scattered from a three-layer biotissue phantom consisting of two skin layers and a blood layer between them, are calculated with the help of a program code based on the Monte Carlo algorithm for different glucose concentrations. Relative changes in the recorded signals caused by variations in the glucose content are analysed for different source - detector separations. It is shown that the maximum relative change in the total pulse energy is 7.2% and 4.8% for the anisotropy factor of the layer mimicking skin g = 0.9 and 0.7, respectively, and the change in the glucose concentration from 0 up to 500 mg dL{sup -1}. The use of time gating leads to the increase in these values up to 12% and 8.5%, respectively. The sensitivity maps are obtained which can be used to determine the optimal duration and the time delay of the time gate relative to the probe pulse for five values of the source - detector separations. (biophotonics)

  4. Application of time gating in the measurement of glucose level in a three-layer biotissue model by using ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Kirillin, M. Yu; Bykov, A. V.; Priezzhev, A. V.; Myllylä, R.

    2008-05-01

    The efficiency of using the time-of-flight (TOF) method at a wavelength of 820 nm for detecting the changes in the optical properties of multilayer light scattering medium in connection with the problem of the glucose level detection in the human tissue is discussed. Pulses scattered from a three-layer biotissue phantom consisting of two skin layers and a blood layer between them, are calculated with the help of a program code based on the Monte Carlo algorithm for different glucose concentrations. Relative changes in the recorded signals caused by variations in the glucose content are analysed for different source - detector separations. It is shown that the maximum relative change in the total pulse energy is 7.2% and 4.8% for the anisotropy factor of the layer mimicking skin g = 0.9 and 0.7, respectively, and the change in the glucose concentration from 0 up to 500 mg dL-1. The use of time gating leads to the increase in these values up to 12% and 8.5%, respectively. The sensitivity maps are obtained which can be used to determine the optimal duration and the time delay of the time gate relative to the probe pulse for five values of the source - detector separations.

  5. Characterization of a broadband interferometric autocorrelator for visible light with ultrashort blue laser pulses

    NASA Astrophysics Data System (ADS)

    Zürch, M.; Hoffmann, A.; Gräfe, M.; Landgraf, B.; Riediger, M.; Spielmann, Ch.

    2014-06-01

    We present a compact interferometric autocorrelator that allows the characterization of ultrashort laser pulses in the visible light domain (370-740 nm). The presented device uses a GaN photodiode with corresponding two-photon absorption. Different GaN and AlGaN photodiodes were characterized for this purpose. Despite AlGaN diodes have a better matched bandgap for this application, we have found that only the GaN diodes show sufficient nonlinear behavior. Using the autocorrelator we were able to characterize ultrashort frequency doubled Ti:Sapphire laser pulses with a pulse duration down to 18 fs in the second harmonic having just a few hundred nanojoules of pulse energy. The broadband behavior and extension towards the UV along with the need for only low energetic pulses are the novelties of this device.

  6. Deformation of ultra-short laser pulses by optical systems for laser scanners.

    PubMed

    Büsing, Lasse; Bonhoff, Tobias; Gottmann, Jens; Loosen, Peter

    2013-10-21

    Current experiments of processing glass with ultra-short laser pulses (< 1 ps) lead to scan angle depending processing results. This scan angle depending effect is examined by simulations of a common focusing lens for laser scanners. Due to dispersion, focusing lenses may cause pulse deformations and increase the pulse duration in the focal region. If the field angle of the incoming laser beam is variable, the pulse deformation may also vary as a function of the field angle. By ray tracing as well as wave optical simulations we investigate pulse deformations of optical systems for different scan angles. PMID:24150292

  7. Plasma luminescence feedback control system for precise ultrashort pulse laser tissue ablation

    NASA Astrophysics Data System (ADS)

    Kim, Beop-Min; Feit, Michael D.; Rubenchik, Alexander M.; Gold, David M.; Darrow, Christopher B.; Marion, John E., II; Da Silva, Luiz B.

    1998-05-01

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using an ultrashort pulse laser. Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so bone tissue is selectively ablated while preserving the spinal cord.

  8. Studies of Inactivation Mechanism of non-enveloped icosahedral viruses by a visible ultrashort pulsed laser

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The inactivation mechanism of ultrashort pulsed laser irradiation at a wavelength of 425 nm has been studied using two different-sized, non-enveloped icosahedral viruses, murine norovirus-1 (MNV-1) and human papillomavirus-16 (HPV-16) pseudovirions. Our experimental results are consistent with a mo...

  9. Ultrashort pulsed laser treatment inactivates viruses by inhibiting viral replication and transcription in the host nucleus

    PubMed Central

    Tsen, Shaw-Wei D.; Chapa, Travis; Beatty, Wandy; Xu, Baogang; Tsen, Kong-Thon; Achilefu, Samuel

    2014-01-01

    Ultrashort pulsed laser irradiation is a new method for virus reduction in pharmaceuticals and blood products. Current evidence suggests that ultrashort pulsed laser irradiation inactivates viruses through an impulsive stimulated Raman scattering process, resulting in aggregation of viral capsid proteins. However, the specific functional defect(s) in viruses inactivated in this manner have not been demonstrated. This information is critical for the optimization and the extension of this treatment platform to other applications. Toward this goal, we investigated whether viral internalization, replication, or gene expression in cells were altered by ultrashort pulsed laser irradiation. Murine Cytomegalovirus (MCMV), an enveloped DNA virus, was used as a model virus. Using electron and fluorescence microscopy, we found that laser-treated MCMV virions successfully internalized in cells, as evidenced by the detection of intracellular virions, which was confirmed by the detection of intracellular viral DNA via PCR. Although the viral DNA itself remained polymerase-amplifiable after laser treatment, no viral replication or gene expression was observed in cells infected with laser-treated virus. These results, along with evidence from previous studies, support a model whereby the laser treatment stabilizes the capsid, which inhibits capsid uncoating within cells. By targeting the mechanical properties of viral capsids, ultrashort pulsed laser treatment represents a unique potential strategy to overcome viral mutational escape, with implications for combatting emerging or drug-resistant pathogens. PMID:25086212

  10. Simple analytical derivation of the fields of an ultrashort tightly focused linearly polarized laser pulse

    NASA Astrophysics Data System (ADS)

    Salamin, Yousef I.

    2015-12-01

    Analytic expressions for the electric and magnetic fields of an ultrashort, tightly focused, linearly polarized laser pulse are derived, to lowest order of a truncated power-series expansion, from vector and scalar potentials. Clear steps are described for the analytic and numerical evaluation of higher-order terms in the series, to any desired accuracy.

  11. Plasma luminescence feedback control system for precise ultrashort pulse laser tissue ablation

    SciTech Connect

    Kim, B.M.; Feit, M.D.; Rubenchick, A.M.; Gold, D.M.; Darrown, C.B.; Da Silva, L.B.

    1998-01-01

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using ultrashort pulse laser (USPL). Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so that only bone tissue can be selectively ablated while preserving the spinal cord.

  12. Numerical calculation of nonlinear ultrashort laser pulse propagation in transparent Kerr media

    NASA Astrophysics Data System (ADS)

    Arnold, Cord L.; Heisterkamp, Alexander; Ertmer, Wolfgang; Lubatschowski, Holger

    2005-03-01

    In the focal region of tightly focused ultrashort laser pulses, sufficient high intensities to initialize nonlinear ionization processes are easily achieved. Due to these nonlinear ionization processes, mainly multiphoton ionization and cascade ionization, free electrons are generated in the focus resulting in optical breakdown. A model including both nonlinear pulse propagation and plasma generation is used to calculate numerically the interaction of ultrashort pulses with their self-induced plasma in the vicinity of the focus. The model is based on a (3+1)-dimensional nonlinear Schroedinger equation describing the pulse propagation coupled to a system of rate equations covering the generation of free electrons. It is applicable to any transparent Kerr medium, whose linear and nonlinear optical parameters are known. Numerical calculations based on this model are used to understand nonlinear side effects, such as streak formation, occurring in addition to optical breakdown during short pulse refractive eye surgeries like fs-LASIK. Since the optical parameters of water are a good first-order approximation to those of corneal tissue, water is used as model substance. The free electron density distribution induced by focused ultrashort pulses as well as the pulses spatio-temporal behavior are studied in the low-power regime around the critical power for self-focusing.

  13. Effect of pulse to pulse interactions on ultra-short pulse laser drilling of steel with repetition rates up to 10 MHz.

    PubMed

    Finger, Johannes; Reininghaus, Martin

    2014-07-28

    We report on the effect of pulse to pulse interactions during percussion drilling of steel using high power ps-laser radiation with repetition rates of up to 10 MHz and high average powers up to 80 W. The ablation rate per pulse is measured as a function of the pulse repetition rate for four fluences ranging from 500 mJ/cm2 up to 1500 mJ/cm2. For every investigated fluence an abrupt increase of the ablation rate per pulse is observed at a distinctive repetition rate. The onset repetition rate for this effect is strongly dependent on the applied pulse fluence. The origin of the increase of the ablation rate is attributed to the emergence of a melt based ablation processes, as Laser Scanning Microscopy (LSM) images show the occurrence of melt ejected material surrounding the drilling holes. A semi empirical model based on classical heat conduction including heat accumulation as well as pulse-particle interactions is applied to enable quantitative conclusions on the origin of the observed data. In agreement with previous studies, the acquired data confirm the relevance of these two effects for the fundamental description of materials processing with ultra-short pulsed laser radiation at high repetition rates and high average power. PMID:25089496

  14. Amplification of ultra-short optical pulses in a two-pump fiber optical parametric chirped pulse amplifier.

    PubMed

    Mussot, Arnaud; Kudlinski, Alexandre; d'Augères, Patrick Beaure; Hugonnot, Emmanuel

    2013-05-20

    We demonstrate with realistic numerical simulations that fiber optical parametric chirped pulse amplification is able to amplify ultra-short optical pulses. Such amplifiers driven by two-pump waves can amplify pulse bandwidth twice as large as the one of a single pump configuration. We show that pulses as short as 50 fs can be directly amplified. In addition, we take benefit from the saturation regime to achieve spectral broadening which makes possible to reduce pulse duration down to 15 fs. PMID:23736440

  15. Evaluation of specialty fibers and waveguides for ultrashort laser pulse propagation

    NASA Astrophysics Data System (ADS)

    Nguyen, Michael N.

    Ultrashort pulse lasers have become invaluable tools in many areas of science and technology. Optical waveguide or fiber delivery of ultrashort pulses would benefit numerous applications that require remote location of the laser or for addressing areas of low accessibility such as minimally invasive surgical procedures, multiphoton excitation microscopy, laser micromachining and high bandwidth telecommunications. However, the extremely high peak power and bandwidth associated with ultrashort pulses are prohibitive for most conventional waveguides that guide light in solid dielectric cores, the main drawbacks being dispersion, nonlinear effects, and damage via optical breakdown. The purpose of this study is to investigate the significant obstacles involved with implementing optical waveguides or fibers capable of delivering ultrashort pulses. In recent years, specialty fibers such as large mode-area (LMA) photonic crystal and photonic bandgap fibers have been developed, which exhibit remarkable properties such as single-mode guidance that is independent of core size and guidance in an air core respectively. In this thesis, two early prototypes of each of these fibers are investigated for their ability to deliver ultrashort pulses. Another specialty fiber, silver coated hollow silica waveguide, which was originally developed for delivery of infrared light from CO2 and Er:YAG lasers is shown to be a good candidate for single-mode delivery of gigawatt peak power pulses with minimal pulse distortion. Another potential fiber is comprised of multiple evanescently-coupled single-mode cores. This so-called multi-core fiber has demonstrated increased power handling in fiber lasers and amplifiers and was selected as a candidate for delivery of ultrashort pulses due to its scalable large mode-area and increased nonlinear threshold. A design for multi-core fibers is proposed that allows tailoring of the supermode distribution to obtain equal power distribution among all cores

  16. Plasma discreteness effects in the presence of an intense, ultrashort laser pulse

    SciTech Connect

    Savchenko, V.I.; Fisch, N.J.

    1996-03-01

    Discrete effects of the plasma irradiated by an ultrashort, intense laser pulse are investigated. Although, for most plasmas of interest, the damping of the laser pulse is due to collective plasma effects, in certain regimes the energy absorbed in the plasma microfields can be important. A scattering matrix is derived for an electron scattering off an ion in the presence of an intense laser field.

  17. LIGHT SOURCE: Terahertz emission in tenuous gases irradiated by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Wang, Wei-Min; Sheng, Zheng-Ming; Wit, Hui-Chun; Chen, Min; Li, Chun; Zhang, Jie; Mima, K.

    2009-06-01

    Mechanism of terahertz (THz) pulse generation in gases irradiated by ultrashort laser pulses is investigated theoretically. Quasi-static transverse currents produced by laser field ionization of gases and the longitudinal modulation in formed plasmas are responsible for the THz emission at the electron plasma frequency, as demonstrated by particle-in-cell simulations including field ionization. The THz field amplitude scaling with the laser amplitude within a large range is also discussed.

  18. Effect of transverse ponderomotive nonlinearity on the propagation of ultrashort laser pulses in a plasma channel

    SciTech Connect

    Upadhyay, Ajay K.; Singh, Ram Gopal; Singh, Vijay; Jha, Pallavi

    2008-12-15

    The present study deals with the propagation of an ultrashort narrow laser beam in a parabolic plasma channel. The effect of transverse ponderomotive nonlinearity on the propagation characteristics of the laser beam is analyzed. Using the variational technique, coupled equations describing the evolution of pulse length and spot size are obtained. The variation of intensity, of mismatched and matched laser pulses, with propagation distance is graphically depicted.

  19. Pulse front tilt measurement of femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Dimitrov, Nikolay; Stoyanov, Lyubomir; Stefanov, Ivan; Dreischuh, Alexander; Hansinger, Peter; Paulus, Gerhard G.

    2016-07-01

    In this work we report experimental investigations of an intentionally introduced pulse front tilt on femtosecond laser pulses by using an inverted field correlator/interferometer. A reliable criterion for the precision in aligning (in principle) dispersionless systems for manipulating ultrashort pulses is developed, specifically including cases when the pulse front tilt is a result of a desired spatio-temporal coupling. The results obtained using two low-dispersion diffraction gratings are in good qualitative agreement with the data from a previously developed analytical model and from an independent interferometric measurement.

  20. Reconstruction of edge density profiles on Large Helical Device using ultrashort-pulse reflectometrya)

    NASA Astrophysics Data System (ADS)

    Yokota, Yuya; Mase, Atsushi; Kogi, Yuichiro; Tokuzawa, Tokihiko; Kawahata, Kazuo; Nagayama, Yoshio; Hojo, Hitoshi

    2008-10-01

    Reflectometry has been expected to be one of the key diagnostics to measure density profiles. We have applied an ultrashort-pulse reflectometry (USPR) system to Large Helical Device in the National Institute for Fusion Science. Wide frequency band system is required to obtain wide density profile since an incident wave is reflected at the density layer corresponding to its cutoff frequency. The reflectometry utilizes an impulse with less than 30ps pulse width as a source. Since the bandwidth of an impulse has an inverse relation to the pulse width, we can cover the frequency range of micro- to millimeter waves (18-40GHz) with a single source. The density profiles can be reconstructed by collecting time-of-flight (TOF) signals for each frequency component of an impulse reflected from the corresponding cutoff layer. We utilize the signal record analysis (SRA) method to reconstruct the density profiles from the TOF signal. The effectiveness of the SRA method for the profile reconstruction is confirmed by a simulation study of the USPR using a finite-difference time domain method.

  1. Adaptive Bessel-autocorrelation of ultrashort pulses with phase-only spatial light modulators

    NASA Astrophysics Data System (ADS)

    Huferath-von Luepke, Silke; Bock, Martin; Grunwald, Ruediger

    2009-06-01

    Recently, we proposed a new approach of a noncollinear correlation technique for ultrashort-pulsed coherent optical signals which was referred to as Bessel-autocorrelator (BAC). The BAC-principle combines the advantages of Bessellike nondiffracting beams like stable propagation, angular robustness and self-reconstruction with the principle of temporal autocorrelation. In comparison to other phase-sensitive measuring techniques, autocorrelation is most straightforward and time-effective because of non-iterative data processing. The analysis of nonlinearly converted fringe patterns of pulsed Bessel-like beams reveals their temporal signature from details of fringe envelopes. By splitting the beams with axicon arrays into multiple sub-beams, transversal resolution is approximated. Here we report on adaptive implementations of BACs with improved phase resolution realized by phase-only liquid-crystal-on-silicon spatial light modulators (LCoS-SLMs). Programming microaxicon phase functions in gray value maps enables for a flexible variation of phase and geometry. Experiments on the diagnostics of few-cycle pulses emitted by a mode-locked Ti:sapphire laser oscillator at wavelengths around 800 nm with 2D-BAC and angular tuned BAC were performed. All-optical phase shift BAC and fringe free BAC approaches are discussed.

  2. Reconstruction of edge density profiles on Large Helical Device using ultrashort-pulse reflectometry.

    PubMed

    Yokota, Yuya; Mase, Atsushi; Kogi, Yuichiro; Tokuzawa, Tokihiko; Kawahata, Kazuo; Nagayama, Yoshio; Hojo, Hitoshi

    2008-10-01

    Reflectometry has been expected to be one of the key diagnostics to measure density profiles. We have applied an ultrashort-pulse reflectometry (USPR) system to Large Helical Device in the National Institute for Fusion Science. Wide frequency band system is required to obtain wide density profile since an incident wave is reflected at the density layer corresponding to its cutoff frequency. The reflectometry utilizes an impulse with less than 30 ps pulse width as a source. Since the bandwidth of an impulse has an inverse relation to the pulse width, we can cover the frequency range of micro- to millimeter waves (18-40 GHz) with a single source. The density profiles can be reconstructed by collecting time-of-flight (TOF) signals for each frequency component of an impulse reflected from the corresponding cutoff layer. We utilize the signal record analysis (SRA) method to reconstruct the density profiles from the TOF signal. The effectiveness of the SRA method for the profile reconstruction is confirmed by a simulation study of the USPR using a finite-difference time domain method. PMID:19044596

  3. X-ray absorption of a warm dense aluminum plasma created by an ultra-short laser pulse

    NASA Astrophysics Data System (ADS)

    Lecherbourg, L.; Renaudin, P.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Blancard, C.; Cossé, P.; Faussurier, G.; Shepherd, R.; Audebert, P.

    2007-05-01

    Point-projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient aluminum plasma created by an ultra-short laser pulse. The 1s-2p and 1s-3p absorption lines of weakly ionized aluminum were measured for an extended range of densities in a low-temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. A detailed opacity code using the density and temperature inferred from the FDI reproduce the measured absorption spectra except in the last stage of the recombination phase.

  4. Characterization of a High Efficiency, Ultrashort Pulse Shaper Incorporating a Reflective 4096-Element Spatial Light Modulator

    PubMed Central

    Field, Jeffrey J.; Planchon, Thomas A.; Amir, Wafa; Durfee, Charles G.; Squier, Jeff A.

    2009-01-01

    We demonstrate pulse shaping via arbitrary phase modulation with a reflective, 1×4096 element, liquid crystal spatial light modulator (SLM). The unique construction of this device provides a very high efficiency when the device is used for phase modulation only in a prism based pulse shaper, namely 85%. We also present a single shot characterization of the SLM in the spatial domain and a single shot characterization of the pulse shaper in the spectral domain. These characterization methods provide a detailed picture of how the SLM modifies the spectral phase of an ultrashort pulse. PMID:19562096

  5. Characterization of a high efficiency, ultrashort pulse shaper incorporating a reflective 4096-element spatial light modulator

    NASA Astrophysics Data System (ADS)

    Field, Jeffrey J.; Planchon, Thomas A.; Amir, Wafa; Durfee, Charles G.; Squier, Jeff A.

    2007-10-01

    We demonstrate pulse shaping via arbitrary phase modulation with a reflective, 1 × 4096 element, liquid crystal spatial light modulator (SLM). The unique construction of this device provides a very high efficiency when the device is used for phase modulation only in a prism based pulse shaper, namely 85%. We also present a single shot characterization of the SLM in the spatial domain and a single shot characterization of the pulse shaper in the spectral domain. These characterization methods provide a detailed picture of how the SLM modifies the spectral phase of an ultrashort pulse.

  6. Intense Isolated Ultrashort Attosecond Pulse Generation in a Multi-Cycle Three-Colour Laser Field

    NASA Astrophysics Data System (ADS)

    Zhang, Gang-Tai

    2014-12-01

    An efficient method for generating an intense isolated ultrashort attosecond pulse is presented theoretically. By adding a 267 nm controlling pulse to a multi-cycle two-colour field, not only the spectral cutoff and the yields of the harmonic spectrum are evidently enhanced, but also the selection of the single quantum path is realised. Then a high-efficiency supercontinuum with a 504 eV bandwidth and smooth structure is obtained, which enables the production of an intense isolated 30 as pulse. In addition, the influences of the laser parameters on the supercontinuum and isolated attosecond pulse are investigated.

  7. Ultrashort hard x-ray pulses generated by 90 degrees Thomson scattering

    SciTech Connect

    Chin, A.H.; Schoenlein, R.W.; Glover, T.E.

    1997-04-01

    Ultrashort x-ray pulses permit observation of fast structural dynamics in a variety of condensed matter systems. The authors have generated 300 femtosecond, 30 keV x-ray pulses by 90 degrees Thomson scattering between femtosecond laser pulses and relativistic electrons. The x-ray and laser pulses are synchronized on a femtosecond time scale, an important prerequisite for ultrafast pump-probe spectroscopy. Analysis of the x-ray beam properties also allows for electron bunch characterization on a femtosecond time scale.

  8. Controlling the Radiation Parameters of a Resonant Medium Excited by a Sequence of Ultrashort Superluminal Pulses

    NASA Astrophysics Data System (ADS)

    Arkhipov, R. M.; Arkhipov, M. V.; Belov, P. A.; Babushkin, I.; Tolmachev, Yu. A.

    2016-03-01

    We investigate the possibility of controlling the radiation parameters of a spatially periodic one-dimensional medium consisting of classical harmonic oscillators by means of a sequence of ultrashort pulses that propagate through the medium with a superluminal velocity. We show that, in the spectrum of the transient process, in addition to the radiation at a resonant frequency of oscillators, new frequencies arise that depend on the period of the spatial distribution of the oscillator density, the excitation velocity, and the angle of observation. We have examined in detail the case of excitation of the medium by a periodic sequence of ultrashort pulses that travel with a superluminal velocity. We show that it is possible to excite oscillations of complex shapes and to control the radiation parameters of the resonant medium by changing the relationship between the pulse repetition rate, the medium resonant frequency, and the new frequency.

  9. Sub-10 nm near-field localization by plasmonic metal nanoaperture arrays with ultrashort light pulses

    PubMed Central

    Lee, Hongki; Kim, Chulhong; Kim, Donghyun

    2015-01-01

    Near-field localization by ultrashort femtosecond light pulses has been investigated using simple geometrical nanoapertures. The apertures employ circular, rhombic, and triangular shapes to localize the distribution of surface plasmon. To understand the geometrical effect on the localization, aperture length and period of the nanoapertures were varied. Aperture length was shown to affect the performance more than aperture period due mainly to intra-aperture coupling of near-fields. Triangular apertures provided the strongest spatial localization below 10 nm in size as well as the highest enhancement of field intensity by more than 7000 times compared to the incident light pulse. Use of ultrashort pulses was found to allow much stronger light localization than with continuous-wave light. The results can be used for super-localization sensing and imaging applications where spatially localized fields can break through the limits in achieving improved sensitivity and resolution. PMID:26628326

  10. Quasi-monochromatic bound on ultrashort light-pulse transmission through fog.

    PubMed

    Shapiro, Jeffrey H

    2011-09-01

    The use of ultrashort (femtosecond duration) light pulses for line-of-sight free-space optical (FSO) communication through fog is receiving increasing attention. Assuming that the transmitter power is low enough to preclude nonlinear interactions, and that scattering-induced multipath spread is less than the reciprocal of the scattering-induced Doppler spread, it is shown that the average transmitter-to-receiver fractional energy transfer of an ultrafast FSO system cannot exceed that of a quasimonochromatic (nanosecond pulse duration) system operating at the optimum wavelength within the ultrafast system's spectrum. Thus, an ultrashort-pulse system is not a solution for high-data-rate FSO communication through fog, because, at best, it will reproduce on average the energy-transfer performance of a wavelength-optimized quasimonochromatic system. PMID:21886209

  11. Sub-10 nm near-field localization by plasmonic metal nanoaperture arrays with ultrashort light pulses.

    PubMed

    Lee, Hongki; Kim, Chulhong; Kim, Donghyun

    2015-01-01

    Near-field localization by ultrashort femtosecond light pulses has been investigated using simple geometrical nanoapertures. The apertures employ circular, rhombic, and triangular shapes to localize the distribution of surface plasmon. To understand the geometrical effect on the localization, aperture length and period of the nanoapertures were varied. Aperture length was shown to affect the performance more than aperture period due mainly to intra-aperture coupling of near-fields. Triangular apertures provided the strongest spatial localization below 10 nm in size as well as the highest enhancement of field intensity by more than 7000 times compared to the incident light pulse. Use of ultrashort pulses was found to allow much stronger light localization than with continuous-wave light. The results can be used for super-localization sensing and imaging applications where spatially localized fields can break through the limits in achieving improved sensitivity and resolution. PMID:26628326

  12. Single-shot spatiotemporal measurements of ultrashort THz waveforms using temporal electric-field cross correlation

    SciTech Connect

    Matlis, Nicholas; Plateau, Guillaume; van Tilborg, Jeroen; Leemans, Wim

    2011-06-17

    A new single-shot technique based on linear spectral interferometry between a temporally short reader pulse and a temporally long probe pulse is demonstrated for measuring the spatiotemporal phase and amplitude of an optical probe for use as an ultrafast diagnostic. The probe spatiotemporal field information is recovered, with a resolution set by the duration of the reader pulse, by applying a single Fourier transform operation to the interferogram image, without need of any reference data. The technique was used in conjunction with electro-optic sampling to measure waveforms of coherent, ultrashort THz pulses emitted by electron bunches from a laser-plasma accelerator with sub-50fs resolution. The presence of strong spatiotemporal coupling in the THz waveforms and of complex temporal electron-bunch structure was determined.

  13. Ultrashort laser pulse induced nanogratings in borosilicate glass

    SciTech Connect

    Zimmermann, Felix Richter, Sören; Plech, Anton; Tünnermann, Andreas; Nolte, Stefan

    2014-05-26

    We report on nanogratings inscribed by repetitive femtosecond laser pulses into the bulk of borosilicate glass. The irradiation produces small nanopores (10–20 nm thick) which start to self-organize in gratings as well as elongated sheets of up to 400 nm length. A quantitative description of the grating structure and its development are obtained by a combination of focused ion beam milling, scanning electron microscopy, and small angle X-ray scattering (SAXS). The SAXS partial invariant of the thin sheets is found to correlate well with the measured optical retardance. Compared to fused silica nanogratings borosilicate glass shows a much smaller retardance due to re-annealing of pores. In addition, the nanograting period strongly deviates from the well-known λ/2n prediction. We could observe periods down to 60 nm (at an inscribing wavelength of 800 nm). This has not been observed yet in other glasses.

  14. Electron acceleration driven by ultrashort and nonparaxial radially polarized laser pulses.

    PubMed

    Marceau, Vincent; April, Alexandre; Piché, Michel

    2012-07-01

    Exact closed-form solutions to Maxwell's equations are used to investigate the acceleration of electrons in vacuum driven by ultrashort and nonparaxial radially polarized laser pulses. We show that the threshold power above which significant acceleration takes place is greatly reduced by using a tighter focus. Moreover, electrons accelerated by tightly focused single-cycle laser pulses may reach around 80% of the theoretical energy gain limit, about twice the value previously reported with few-cycle paraxial pulses. Our results demonstrate that the direct acceleration of electrons in vacuum is well within reach of current laser technology. PMID:22743415

  15. Vibrational predissociation of methylnitrite using phase-locked ultrashort laser pulses

    NASA Technical Reports Server (NTRS)

    Dateo, Christopher E.; Metiu, Horia

    1993-01-01

    We solve numerically the time-dependent Schroedinger equation to study the behavior of a molecule interacting with two phase-locked ultrashort laser pulses. The 2D model used in the calculations mimics the properties of the CH3ONO molecule. The two pulses are identical except for their relative phase and are tuned to excite an upper electronic state of the molecule. After excitation the molecule predissociates, and we calculate the dependence of the NO yield and of the NO vibrational population on the delay time between the pulses.

  16. Ultrashort-pulse-train pump and dump excitation of a diatomic molecule

    SciTech Connect

    Araujo, Luis E. E. de

    2010-09-15

    An excitation scheme is proposed for transferring population between ground-vibrational levels of a molecule. The transfer is accomplished by pumping and dumping population with a pair of coherent ultrashort-pulse trains via a stationary state. By mismatching the teeth of the frequency combs associated with the pulse trains to the vibrational levels, high selectivity in the excitation, along with high transfer efficiency, is predicted. The pump-dump scheme does not suffer from spontaneous emission losses, it is insensitive to the pump-dump-train delay, and it requires only basic pulse shaping.

  17. Two-photon excitation of atoms by ultrashort electromagnetic pulses in a discrete spectrum

    NASA Astrophysics Data System (ADS)

    Astapenko, V. A.; Sakhno, S. V.

    2016-07-01

    The paper is devoted to the theoretical investigation of two-photon excitation of atom in a discrete energy spectrum by ultrashort electromagnetic pulses of femto- and subfemtosecond ranges of durations. An analytical expression for the total probability of the process is derived. Numerical simulations are made for hydrogen and sodium atoms. It is shown that the total probability of the process is nonlinear function of pulse duration and character of this function depends strongly on the frequency detuning of pulse carrier frequency from two-photon resonance.

  18. High-speed ultrashort pulse fiber ring laser using charcoal nanoparticles.

    PubMed

    Li, Wenbo; Hu, Hongyu; Zhang, Xiang; Zhao, Shuai; Fu, Kan; Dutta, Niloy K

    2016-03-20

    A mode-locked erbium-doped fiber ring laser that is easy to set up is proposed and experimentally demonstrated to generate a high-repetition-rate optical pulse train with an ultrashort pulse width. The laser combines a rational harmonic mode-locking technique and charcoal nanoparticles as saturable absorbers. Compared to a solely active mode-locking scheme, the scheme with charcoal nanoparticles can remove the supermodes and narrow the pulse width by a factor of 0.57 at a repetition rate of 20 GHz. Numerical simulation of the laser performance is also provided, which shows good agreement with the experimental results. PMID:27140546

  19. Nonlinear scattering of ultrashort laser pulses on two-level system

    NASA Astrophysics Data System (ADS)

    Astapenko, Valery A.; Sakhno, Sergey V.

    2015-05-01

    The presentation is devoted to the theoretical investigation of nonlinear scattering of ultrashort electromagnetic pulses (USP) on two-level quantum system. We consider the scattering of several types of USP, namely, so called corrected Gaussian pulse (CGP) and cosine wavelet pulse. Such pulses have no constant component in their spectrum in contrast with traditional Gaussian pulse. It should be noted that the presence of constant component in the limit of ultrashort pulse durations leads to unphysical results. The main purpose of the present work is the investigation of the change of pulse temporal shape after scattering as a function of initial phase at different distances from the target. Numerical calculations are based on the solution of Bloch equations and expression for scattering field strength via dipole moment of two-level system exposed by the action of incident USP. In our calculation we also account for the influence of refracting index of the air on electric field strength in the pulse after scattering.

  20. Multiple pulse thresholds in live eyes for ultrashort laser pulses in the near infrared

    NASA Astrophysics Data System (ADS)

    Stolarski, David J.; Cain, Clarence P.; Toth, Cynthia A.; Noojin, Gary D.; Rockwell, Benjamin A.

    1999-06-01

    Damage thresholds using multiple laser pulses to produce minimum visible lesions (MVL) in rhesus monkey eyes are reported for near-infrared (800 nm) at 130 femtoseconds. Previous studies by our research group using single pulses in the near-infrared (1060 nm) have determined damage thresholds and retinal spot size dependence. We report the first multiple pulse damage thresholds using femtosecond pulses. MVL thresholds at 1 hour and 24 hours postexposure were determined for 1, 100 and 1,000 pulses and we compare these with other reported multiple pulse thresholds. These new data will be added to the databank for retinal MVL's as a function of pulse repetition rate for this pulsewidth and a comparison will be made with the ANSI standard for multiple pulse exposures. Our measurements show that the retinal ED50 threshold/pulse in the paramacula decreases for increasing number of pulses. The MVL-ED50 at the threshold/pulse decreased by a factor of 4 (0.55 (mu) J to 0.13 (mu) J/pulse) for an increase from 1 to 100 pulses.

  1. Polarization sensitive anisotropic structuring of silicon by ultrashort light pulses

    SciTech Connect

    Zhang, Jingyu; Drevinskas, Rokas Beresna, Martynas; Kazansky, Peter G.

    2015-07-27

    Imprinting of anisotropic structures on the silicon surface by double pulse femtosecond laser irradiation is demonstrated. The origin of the polarization-induced anisotropy is explained in terms of interaction of linearly polarized second pulse with the wavelength-sized symmetric crater-shaped structure generated by the linearly polarized first pulse. A wavefront sensor is fabricated by imprinting an array of micro-craters. Polarization controlled anisotropy of the structures can be also explored for data storage applications.

  2. Ultra-short pulse laser deep drilling of C/SiC composites in air

    NASA Astrophysics Data System (ADS)

    Wang, Chunhui; Zhang, Litong; Liu, Yongsheng; Cheng, Guanghua; Zhang, Qing; Hua, Ke

    2013-06-01

    Ultra-short pulse laser machining is an important finishing technology for high hardness materials. In this study, it demonstrated that the ultra-short pulse laser can be used to drill the film cooling holes and square holes in aero-engine turbine blades made of C/SiC composites. Both the edges and bottoms of the drilling holes are covered with small particles. The following factors have a great effect on drilling holes according to this work: (1) circular holes can be processed only at a relative small helical lines spacing. (2) With the increase of laser scanning speed, the depth of holes reduces while the diameter rarely changes. (3) Through the holes of high aspect ratio can be obtained via high processing power.

  3. Modification of transparent materials with ultrashort laser pulses: What is energetically and mechanically meaningful?

    NASA Astrophysics Data System (ADS)

    Bulgakova, Nadezhda M.; Zhukov, Vladimir P.; Sonina, Svetlana V.; Meshcheryakov, Yuri P.

    2015-12-01

    A comprehensive analysis of laser-induced modification of bulk glass by single ultrashort laser pulses is presented which is based on combination of optical Maxwell-based modeling with thermoelastoplastic simulations of post-irradiation behavior of matter. A controversial question on free electron density generated inside bulk glass by ultrashort laser pulses in modification regimes is addressed on energy balance grounds. Spatiotemporal dynamics of laser beam propagation in fused silica have been elucidated for the regimes used for direct laser writing in bulk glass. 3D thermoelastoplastic modeling of material relocation dynamics under laser-induced stresses has been performed up to the microsecond timescale when all motions in the material decay. The final modification structure is found to be imprinted into material matrix already at sub-nanosecond timescale. Modeling results agree well with available experimental data on laser light transmission through the sample and the final modification structure.

  4. Modification of transparent materials with ultrashort laser pulses: What is energetically and mechanically meaningful?

    SciTech Connect

    Bulgakova, Nadezhda M.; Zhukov, Vladimir P.; Sonina, Svetlana V.; Meshcheryakov, Yuri P.

    2015-12-21

    A comprehensive analysis of laser-induced modification of bulk glass by single ultrashort laser pulses is presented which is based on combination of optical Maxwell-based modeling with thermoelastoplastic simulations of post-irradiation behavior of matter. A controversial question on free electron density generated inside bulk glass by ultrashort laser pulses in modification regimes is addressed on energy balance grounds. Spatiotemporal dynamics of laser beam propagation in fused silica have been elucidated for the regimes used for direct laser writing in bulk glass. 3D thermoelastoplastic modeling of material relocation dynamics under laser-induced stresses has been performed up to the microsecond timescale when all motions in the material decay. The final modification structure is found to be imprinted into material matrix already at sub-nanosecond timescale. Modeling results agree well with available experimental data on laser light transmission through the sample and the final modification structure.

  5. Chirp-free ultra-short pulses in complex nonlinear optical fibers

    NASA Astrophysics Data System (ADS)

    Jiang, Xiance; Liang, Jianchu; Cao, Jianzhong; Song, Jinxiang; Cai, Zebin

    2016-04-01

    Chirp-free ultra-short pulses propagating in optical fiber with complex parameters are investigated for the first time. The existence condition for such chirp-free ultrashort pulses is that the imaginary parts of the nonlinear terms, i.e., the nonlinear absorption coefficient (a2i), nonlinear dispersion coefficient (a4i) and imaginary Raman coefficient (a2i) fulfill a linear relationship a2i = a4i ω = -2/3 a5i ω . Bight solitons can stably propagate in such complex nonlinear optical fiber. It is found that the single Jacobi elliptic function solutions have two free parameters while hybrid Jacobi elliptic function solutions have only one free parameter.

  6. Optical coherence tomography of the retinal response to ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Toth, Cynthia A.; Narayan, Drew G.; Roach, William P.; Birngruber, Reginald; Boppart, Stephen A.; Hee, Michael R.; DiCarlo, Cheryl D.; Cain, Clarence P.; Noojin, Gary D.; Fujimoto, James G.

    1997-06-01

    Purpose: to assess the early in vivo evolution of tissue response and wound healing from ultrashort pulsed laser retinal lesions by correlating the cross sectional morphology from sequential optical coherence tomography with histopathologic sectioning. Methods: single ultrashort laser pulses were placed in the Macacca mulatta retina and evaluated by cross-section optical coherence tomography (OCT). These images were compared at selected time-points with corresponding histological sections. Results: OCT was able to detect the acute tissue injury from laser delivery and the evolution of the healing response over 8 days after laser delivery. These OCT images correlated well with histopathologic findings. Conclusion: analysis of the extent of initial laser lesions and the type of healing response can be performed in serial sequence with OCT providing new insight into the healing response form laser injury. This information correlates well with microscopic data.

  7. How to optimize ultrashort pulse laser interaction with glass surfaces in cutting regimes?

    NASA Astrophysics Data System (ADS)

    Bulgakova, Nadezhda M.; Zhukov, Vladimir P.; Collins, Adam R.; Rostohar, Danijela; Derrien, Thibault J.-Y.; Mocek, Tomáš

    2015-05-01

    The interaction of short and ultrashort pulse laser radiation with glass materials is addressed. Particular attention is paid to regimes which are important in industrial applications such as laser cutting, drilling, functionalization of material surfaces, etc. Different factors influencing the ablation efficiency and quality are summarized and their importance is illustrated experimentally. The effects of ambient gas ionization in front of the irradiated target are also analyzed. A possibility to enhance laser coupling with transparent solids by bi-wavelength irradiation is discussed.

  8. Research on optical damage to sodium chloride by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Gavasheli, Yu. O.; Komarov, P. S.; Ashitkov, S. I.; Savintsev, A. P.

    2016-06-01

    Thresholds of optical damage to sodium chloride by ultrashort laser pulses with a duration of about 40 fs are determined. Experiments were carried out using a terawatt titanium-sapphire laser device. p-polarized laser radiation at a wavelength of 800 nm fell on the specimen surface at an angle of 60°. Optical damage to the surface was observed when the critical electric field strength attained 94 MV/cm.

  9. Dynamics of ultrashort pulsed laser radiation induced non-thermal ablation of graphite

    NASA Astrophysics Data System (ADS)

    Reininghaus, M.; Kalupka, C.; Faley, O.; Holtum, T.; Finger, J.; Stampfer, C.

    2014-12-01

    We report on the dependence of a laser radiation induced ablation process of graphite on the applied pulse duration of ultrashort pulsed laser radiation smaller than 4 ps. The emerging so-called non-thermal ablation process of graphite has been confirmed to be capable to physically separate ultrathin graphitic layers from the surface of pristine graphite bulk crystal. This allows the deposition of ablated graphitic flakes on a substrate in the vicinity of the target. The observed ablation threshold determined at different pulse durations shows a modulation, which we ascribe to lattice motions along the c axis that are theoretically predicted to induce the non-thermal ablation process. In a simple approach, the ablation threshold can be described as a function of the energy penetration depth and the absorption of the applied ultrashort pulsed laser radiation. Based on the analysis of the pulse duration dependence of those two determining factors and the assumption of an invariant ablation process, we are able to reproduce the pulse duration dependence of the ablation threshold. Furthermore, the observed pulse duration dependences confirm the assumption of a fast material specific response of graphite target subsequent to optical excitation within the first 2 ps.

  10. Model for electron detachment from negative ions by ultrashort half-cycle electric-field pulses

    NASA Astrophysics Data System (ADS)

    Grozdanov, T. P.; Jaćimović, J.

    2009-01-01

    We study a model for electron detachment from negative ions by ultrashort unipolar electric pulses. The electron-atom interaction is described by the zero-range potential and the temporal dependence of the electric field is approximated by the Dirac δ functions. The case of a single pulse can be treated semianalytically and explicit expressions are obtained for momentum and energy distributions of detached electrons as well as for the total detachment probability. The determination of angular distribution involves numerical evaluation of a one-dimensional integral. The case of two alternating electric pulses requires numerical evaluation of more complicated integrals but leads to interesting effects caused by the quantum interference of the electronic wave packets produced during the interactions with the first and the second pulses. The differential and integral detachment probabilities are calculated and discussed for a variety of pulse strengths and time delays between the pulses.

  11. Spatiotemporal evolution of single-cycle and few-cycle ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Feng, Simin

    We investigate the spatiotemporal evolution of single- cycle and few-cycle ultrashort electromagnetic pulses. Exact solutions of the free space full vector Maxwell's equations are provided. These solutions are nonsinusoidal, nonstationary and nonseparable in space and time. They describe space-time localized wavepackets representing transmission of electromagnetic energy in free spare. In a manner similar to dispersion effects on broadband signals, diffraction effects on transversely confined ultrashort pulses in the single-cycle region cause significant pulse reshaping and waveform distortion as a consequence of spacetime coupling. Particularly in the paraxial region, the diffraction-induced Gouy phase shift plays a significant role in free space propagation to change the temporal waveform of the single-cycle pulses. As a result of the Gouy phase shift, the single- cycle pulse experiences polarity and time reversals as it passes through the focus. When such a pulse propagates in quadratic phase media, the accumulated Gouy phase shift results in nonstationary variation of absolute phase and temporal waveform distortion. We show that the physical origin of the Gouy phase shift is the transverse confinement of the extended wave and hence is related to the uncertainty principle of the fundamental physics. In the nonparaxial region, polarization of the electric field of single-cycle pulses cannot be represented by any of a simple ellipse, circle or straight line. In general the tip of the electric field vector moves along a cardioid and the polarization state changes during propagation. We also investigate the higher-order transverse modes of single-cycle pulses, particularly Hermite-Gaussian and Laguerre-Gaussian modes. The effects of space-time coupling is more significant in the higher-order transverse modes. These effects includes dark pulses, dark ring pulses, spiral pulses and vortex strings. Since Hermite-Gaussian or Laguerre-Gaussian modes of single- cycle

  12. Spectral property of ultrashort chirped pulsed Gaussian beams diffracted by Gaussian aperture in dispersive media

    NASA Astrophysics Data System (ADS)

    Zou, Qihui; Hu, Qianhuan; Guo, Jie; Duan, Xi; Tong, Shihong

    2015-10-01

    Based on the Fresnel-Kirchhoff diffraction integral and Fourier transform, the propagation equation and its Fourier spectrum for ultra-short chirped pulsed Gaussian beams diffracted by Gaussian aperture are derived in dispersive medium, and the frequency-domain analytical electric field are presented. The effects of relative aperture, transmission distance and chirp parameter on the axial spectral properties are illustrated with numerical calculation results, and the variations of off-axis power spectrum with relative aperture, transmission distance and off-axis radius are given. It is found that the axial power spectrum of ultra-short chirped pulsed Gaussian increases with increasing relative aperture, the axial spectral blue-shift increases and approaches an asymptotic value associated with chirp parameter and propagation distance. The axial spectra of ultra-short chirped pulsed Gaussian become broadened with increasing the absolute value of the chirp parameter. With increasing off-axis radius, the off-axis power spectrum reduce rapidly, and the distribution of spectra shifts to the left. The off-axis spectral redshift increases with increasing off-axis radius.

  13. Production of dense vapor targets for laser-plasma interaction studies with intense, ultra-short pulses

    SciTech Connect

    Bolton, P.R.; Eder, D.C.; Guethlein, G.; Stewart, R.E.; Young, P.E.

    1993-03-19

    The technique of laser-induced ablation of thin films from glass slide substrates has been investigated as a candidate vapor target production method for studies of both tunneling-driven x-ray/xuv recombination lasers and relativistic propagation using intense, ultra-short laser pulses. It is shown by simultaneous two-wavelength interferometry that particle densities of order 10{sup 19}/cm{sup 3} are readily achieved and that some intrinsic ionization accompanies the plume formation. Absorption measurements with both 100 picosecond and 125 femtosecond pulses are consistent with observed edge velocities near 10{sup 6} cm/sec. The level of ionization driven by the intense 125 femtosecond laser pulse has been coarsely estimated. Averaged estimates from spectral blue shifting of spectra transmitted through the plume are consistently lower than those obtained from evaluation of saturation intensity thresholds based on the sequential nonresonant optical field ionization (OFI) process.

  14. Hydrodynamic simulation of ultrashort pulse laser ablation of gold film

    NASA Astrophysics Data System (ADS)

    Yu, Dong; Jiang, Lan; Wang, Feng; Shi, Xuesong; Qu, Liangti; Lu, Yongfeng

    2015-06-01

    The electron collision frequency in a hydrodynamic model was improved to match the laser energy absorbed with experimental data. The model calculation was used to investigate the ablation depth and the dependence of the threshold fluence of gold film on pulse width and wavelength. Two methods for estimating the ablation depth are introduced here with their respective scope of application. The dependence of the threshold fluence of gold film on the pulse width of the laser with a 1053 nm center wavelength agreed well with the experimental data. It was also observed that for pulses shorter than ~200 ps, the threshold fluence showed linear dependence on the logarithm of pulse width and increased with the wavelength, which was different from previous results.

  15. Modeling of ultrashort pulse generation in mode-locked VECSELs

    NASA Astrophysics Data System (ADS)

    Kilen, I.; Koch, S. W.; Hader, J.; Moloney, J. V.

    2016-03-01

    We present a study of various models for the mode-locked pulse dynamics in a vertical external-cavity surface emitting laser with a saturable absorber. The semiconductor Bloch equations are used to model microscopically the light-matter interaction and the carrier dynamics. Maxwell's equations describe the pulse propagation. Scattering contributions due to higher order correlation effects are approximated using effective rates that are found from a comparison to solving the microscopic scattering equations on the second Born-Markov level. It is shown that the simulations result in the same mode-locked final state whether the system is initialized with a test pulse close to the final mode-locked pulse or the full field build-up from statistical noise is considered. The influence of the cavity design is studied. The longest pulses are found for a standard V-cavity while a linear cavity and a V-cavity with an high reflectivity mirror in the middle are shown to produce similar, much shorter pulses.

  16. Ultrashort pulse laser processing of hard tissue, dental restoration materials, and biocompatibles

    NASA Astrophysics Data System (ADS)

    Yousif, A.; Strassl, M.; Beer, F.; Verhagen, L.; Wittschier, M.; Wintner, E.

    2007-07-01

    During the last few years, ultra-short laser pulses have proven their potential for application in medical tissue treatment in many ways. In hard tissue ablation, their aptitude for material ablation with negligible collateral damage provides many advantages. Especially teeth representing an anatomically and physiologically very special region with less blood circulation and lower healing rates than other tissues require most careful treatment. Hence, overheating of the pulp and induction of microcracks are some of the most problematic issues in dental preparation. Up till now it was shown by many authors that the application of picosecond or femtosecond pulses allows to perform ablation with very low damaging potential also fitting to the physiological requirements indicated. Beside the short interaction time with the irradiated matter, scanning of the ultra-short pulse trains turned out to be crucial for ablating cavities of the required quality. One main reason for this can be seen in the fact that during scanning the time period between two subsequent pulses incident on the same spot is so much extended that no heat accumulation effects occur and each pulse can be treated as a first one with respect to its local impact. Extension of this advantageous technique to biocompatible materials, i.e. in this case dental restoration materials and titanium plasma-sprayed implants, is just a matter of consequence. Recently published results on composites fit well with earlier data on dental hard tissue. In case of plaque which has to be removed from implants, it turns out that removal of at least the calcified version is harder than tissue removal. Therefore, besides ultra-short lasers, also Diode and Neodymium lasers, in cw and pulsed modes, have been studied with respect to plaque removal and sterilization. The temperature increase during laser exposure has been experimentally evaluated in parallel.

  17. Ultra-short pulse propagation in multi-level media

    NASA Astrophysics Data System (ADS)

    Clader, B. David

    We consider the propagation of short, intense laser pulses through media consisting of two-level and three-level atoms. We derive the coupled Maxwell-Bloch (MB) equations, which describe such propagation. Many different physical situations have been studied by analyzing various limiting cases of these equations. Most of the recent work has relied on steady-state or adiabatic assumptions to simplify the analysis of the MB equations. However rapid progress has been made in recent years in developing analytic solution techniques that do not require these simplifications, such as BAcklund transformations, inverse scattering methods, and Darboux transformations. We use the Backlund solution method, to derive soliton solutions to the MB equations for various physical situations of interest in multi-level media. In addition we examine the experimental applicability of the exact solutions by numerically integrating the MB equations for more physically realistic pulse shapes and media preparations that may not permit analytic solutions. In two-level inverted gain media, we derive a pulse solution with group velocity exceeding the speed of light in vacuum (fast light). Numerical results confirm that such a pulse can exhibit fractional peak advances exceeding one pulse width despite spontaneous instabilites such as superfluorescence and stimulated instabilities related to the McCall-Hahn area theorem. In three-level Λ type media we derive soliton solutions for two pulses propagating through a medium prepared in an arbitrary mixed-state of the two ground states. We include a tunable parameter in the solutions that allows one to vary the medium between completely mixed state and completely pure-state superpositions known as "phaseonium". This flexibility allows one to study the interplay between stimulated Raman scattering, electromagnetically induced transparency (EIT), self induced transparency (SIT), and pulse matching. Past results have indicated that asymptotic pulse

  18. Effect Of The Anisotropy On The Transport In Plasmas Created By Ultra-Short Laser Pulse

    NASA Astrophysics Data System (ADS)

    Hasnaoui, A.; Bendib, A.

    2008-09-01

    The formation of a high anisotropic photoelectron distribution, as a result of the interaction of a powerful ultra-short laser pulse with a nonequilibrium and a collisionless plasma, in some aspects fundamentally changes the laser-material interaction mechanisms compared with a long pulse. In this work, using the initial conditions, the analytic solution of the Vlasov equation linearised with respect to the bi-Maxwellian distribution function is presented. To unsure the conservative properties, we have added formally the Krook collision term in the limit of a vanishing collision frequency. We have deduced the generalized transport coefficients, witch constitute very reliable closure relations for the collisionless anisotropic fluid equations.

  19. Ultrashort Optical Pulses in a Fermi Liquid and Duality of Gauge Gravitation

    NASA Astrophysics Data System (ADS)

    Konobeeva, N. N.; Belonenko, M. B.

    2016-07-01

    The problem of the propagation of ultrashort pulses, including both two-dimensional and three-dimensional pulses, in a Fermi liquid is considered with the help of representations of the duality of gauge gravitation. The electromagnetic field is considered classically on the basis of the Maxwell equations. The effective equation so obtained is analyzed numerically and the dynamics of the state of the electromagnetic field are elucidated in the planar case, and also when it is localized in two/three spatial dimensions.

  20. Effect Of The Anisotropy On The Transport In Plasmas Created By Ultra-Short Laser Pulse

    SciTech Connect

    Hasnaoui, A.; Bendib, A.

    2008-09-23

    The formation of a high anisotropic photoelectron distribution, as a result of the interaction of a powerful ultra-short laser pulse with a nonequilibrium and a collisionless plasma, in some aspects fundamentally changes the laser-material interaction mechanisms compared with a long pulse. In this work, using the initial conditions, the analytic solution of the Vlasov equation linearised with respect to the bi-Maxwellian distribution function is presented. To unsure the conservative properties, we have added formally the Krook collision term in the limit of a vanishing collision frequency. We have deduced the generalized transport coefficients, witch constitute very reliable closure relations for the collisionless anisotropic fluid equations.

  1. Imaging carrier and phonon transport in Si using ultrashort optical pulses

    SciTech Connect

    David H. Hurley; O. B. Wright; O. Matsuda; B. E. McCandless; S. Shinde

    2009-01-01

    A series of experiments have been conducted that microscopically image thermal diffusion and surface acoustic phonon propagation within a single crystallite of a polycrystalline Si sample. The experimental approach employs ultrashort optical pulses to generate an electron-hole plasma and a second probe pulse is used to image the evolution of the plasma. By decomposing the signal into a component that varies with delay time and a steady state component that varies with pump modulation frequency, the respective influence of carrier recombination and thermal diffusion are identified. Additionally, the coherent surface acoustic phonon component to the signal is imaged using a Sagnac interferometer to monitor optical phase.

  2. Electrochemical machining with ultrashort voltage pulses: modelling of charging dynamics and feature profile evolution.

    PubMed

    Kenney, Jason A; Hwang, Gyeong S

    2005-07-01

    A two-dimensional computational model is developed to describe electrochemical nanostructuring of conducting materials with ultrashort voltage pulses. The model consists of (1) a transient charging simulation to describe the evolution of the overpotentials at the tool and workpiece surfaces and the resulting dissolution currents and (2) a feature profile evolution tool which uses the level set method to describe either vertical or lateral etching of the workpiece. Results presented include transient currents at different separations between tool and workpiece, evolution of overpotentials and dissolution currents as a function of position along the workpiece, and etch profiles as a function of pulse duration. PMID:21727446

  3. A 5 Hz flashlamp pumped Cr:LiSAF multipass amplifier for ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Samad, R. E.; Nogueira, G. E. C.; Baldochi, S. L.; Vieira, N. D., Jr.

    2008-10-01

    We report here the operation, at 5 Hz, of a multipass flashlamp pumped Cr:LiSAF ultrashort pulse amplifier, presenting peak powers over 0.3 TW. This unusual high repetition rate was obtained by using a two-flashlamp pumping scheme, aiming at the minimization of the thermal load on the gain medium by the use of intracavity absorption filters. This cavity was used as a four-pass multipass amplifier in a hybrid Ti:sapphire/Cr:LiSAF system. The maximum amplification factor was 150, and the compressed pulse duration was 60 fs.

  4. Fields and propagation characteristics in vacuum of an ultrashort tightly focused radially polarized laser pulse

    NASA Astrophysics Data System (ADS)

    Salamin, Yousef I.

    2015-11-01

    Analytic expressions for the electric and magnetic fields of a radially polarized ultrashort and tightly focused laser pulse, propagating in vacuum, are derived from scalar and vector potentials satisfying simple initial conditions. It is shown that for a pulse of axial length comparable to a wavelength, only the zeroth (lowest-order) term in a power-series expansion of the vector potential is needed. A procedure is outlined which may be used to obtain the fields analytically, to any desired order. Most of the needed analytic work is done that would lead to the vector potential from which the fields may be derived and the main expressions are given.

  5. Medical applications of ultra-short pulse lasers

    SciTech Connect

    Kim, B M; Marion, J E

    1999-06-08

    The medical applications for ultra short pulse lasers (USPLs) and their associated commercial potential are reviewed. Short pulse lasers offer the surgeon the possibility of precision cutting or disruption of tissue with virtually no thermal or mechanical damage to the surrounding areas. Therefore the USPL offers potential improvement to numerous existing medical procedures. Secondly, when USPLs are combined with advanced tissue diagnostics, there are possibilities for tissue-selective precision ablation that may allow for new surgeries that cannot at present be performed. Here we briefly review the advantages of short pulse lasers, examine the potential markets both from an investment community perspective, and from the view. of the technology provider. Finally nominal performance and cost requirements for the lasers, delivery systems and diagnostics and the present state of development will be addressed.

  6. Optical trapping of nanoparticles by ultrashort laser pulses.

    PubMed

    Usman, Anwar; Chiang, Wei-Yi; Masuhara, Hiroshi

    2013-01-01

    Optical trapping with continuous-wave lasers has been a fascinating field in the optical manipulation. It has become a powerful tool for manipulating micrometer-sized objects, and has been widely applied in physics, chemistry, biology, material, and colloidal science. Replacing the continuous-wave- with pulsed-mode laser in optical trapping has already revealed some novel phenomena, including the stable trap, modifiable trapping positions, and controllable directional optical ejections of particles in nanometer scales. Due to two distinctive features; impulsive peak powers and relaxation time between consecutive pulses, the optical trapping with the laser pulses has been demonstrated to have some advantages over conventional continuous-wave lasers, particularly when the particles are within Rayleigh approximation. This would open unprecedented opportunities in both fundamental science and application. This Review summarizes recent advances in the optical trapping with laser pulses and discusses the electromagnetic formulations and physical interpretations of the new phenomena. Its aim is rather to show how beautiful and promising this field will be, and to encourage the in-depth study of this field. PMID:23738434

  7. Are ultrashort x-ray pulses likely to be less carcinogenic?

    NASA Astrophysics Data System (ADS)

    Waynant, Ronald W.; Ilev, Ilko K.; Mitra, Kunal

    2004-07-01

    With the development of femtosecond and shorter pulsewidth lasers and the ability to amplify these pulses to incredibly high pulsed power has come the ability to produce ultrashort pulses of x-rays. In previous years sessions of this conference we have proposed use of these ultrashort pulses of x-rays to produce high resolution, high image quality three dimensional x-ray images of breast and other areas of the body. Theoretical studies of the impact of increasing higher power of UV and X-Ray sources for sterilization lead us to question whether very short pulses of extremely high power (but low dose, i.e. J/cm2) may have less carcinogenic effect. If this is true, it could potentially allow greater use of such x-ray systems for breast cancer surveillance as well as other areas such as deep body inspection. In addition, it could allow for creation of better images by use of higher resolution, noise reduction and higher repetition rates. Better images should improve detection.

  8. Oral applications of ultra-short laser pulses: a new approach for gentle and painless treatment?

    NASA Astrophysics Data System (ADS)

    Yousif, A.; Strassl, M.; Wieger, V.; Zoppel, S.; Wintner, E.

    2006-05-01

    In dental hard tissue ablation, ultra-short laser pulses have proven sufficiently their potential for material ablation with negligible collateral damage providing many advantages. The absence of microcracks and the possibility to avoid overheating of the pulp during dental cavity preparation may be among the most important issues, the latter opening up an avenue for potential painless treatment. Beside the evident short interaction time of laser radiation with the irradiated tissue, scanning of the ultra-short pulse trains turned out to be crucial for ablating cavities of required quality and shape. Additionally, such a technique allows to treat larger areas like the ones dentists are used to work with, i.e. ~ 1 mm Ø.In this paper, an overview of different scanning methods together with the algorithms used and an assessment of their applicability is presented. A variety of pulse durations from ~100 fs up to several ps has been used by numerous authors over the last approximately ten years. Having employed 330 fs pulses, we present the corresponding ablation thresholds for dental hard tissue (enamel, dentine; human and bovine), for a number of dental restoration materials, as well as for different types of bovine bone. Dental implants frequently have to be cleaned from plaque being deposited around their necks in areas where the gums have already retreated. A preliminary investigation is presented on the applicability of ultra-short pulses with mentioned duration for the gentle cleaning of titanium implants focusing on the preservation of the special plasma-sprayed biocompatible implant surface.

  9. Coherent Control of Multiphoton Transitions in the Gas and Condensed Phases with Shaped Ultrashort Pulses

    SciTech Connect

    Marcos Dantus

    2008-09-23

    Controlling laser-molecule interactions has become an integral part of developing devices and applications in spectroscopy, microscopy, optical switching, micromachining and photochemistry. Coherent control of multiphoton transitions could bring a significant improvement of these methods. In microscopy, multi-photon transitions are used to activate different contrast agents and suppress background fluorescence; coherent control could generate selective probe excitation. In photochemistry, different dissociative states are accessed through two, three, or more photon transitions; coherent control could be used to select the reaction pathway and therefore the yield-specific products. For micromachining and processing a wide variety of materials, femtosecond lasers are now used routinely. Understanding the interactions between the intense femtosecond pulse and the material could lead to technologically important advances. Pulse shaping could then be used to optimize the desired outcome. The scope of our research program is to develop robust and efficient strategies to control nonlinear laser-matter interactions using ultrashort shaped pulses in gas and condensed phases. Our systematic research has led to significant developments in a number of areas relevant to the AMO Physics group at DOE, among them: generation of ultrashort phase shaped pulses, coherent control and manipulation of quantum mechanical states in gas and condensed phases, behavior of isolated molecules under intense laser fields, behavior of condensed phase matter under intense laser field and implications on micromachining with ultrashort pulses, coherent control of nanoparticles their surface plasmon waves and their nonlinear optical behavior, and observation of coherent Coulomb explosion processes at 10^16 W/cm^2. In all, the research has resulted in 36 publications (five journal covers) and nine invention disclosures, five of which have continued on to patenting

  10. Variational regularization of complex deautoconvolution and phase retrieval in ultrashort laser pulse characterization

    NASA Astrophysics Data System (ADS)

    Anzengruber, Stephan W.; Bürger, Steven; Hofmann, Bernd; Steinmeyer, Günter

    2016-03-01

    The SD-SPIDER method for the characterization of ultrashort laser pulses requires the solution of a nonlinear integral equation of autoconvolution type with a device-based kernel function. Taking into account the analytical background of a variational regularization approach for solving the corresponding ill-posed operator equation formulated in complex-valued L 2-spaces over finite real intervals, we suggest and evaluate numerical procedures using NURBS and the TIGRA method for calculating the regularized solutions in a stable manner. In this context, besides the complex deautoconvolution problem with noisy but full data, a phase retrieval problem is introduced which adapts to the experimental state of the art in laser optics. For the treatment of this problem facet, which is formulated as a tensor product operator equation, we derive the well-posedness of variational regularization methods. Case studies with synthetic and real optical data show the capability of the implemented approach as well as its limitations due to measurement deficits.

  11. Combined OCT and CARS using a single ultrashort pulse Ti:Sapphire laser

    NASA Astrophysics Data System (ADS)

    Hoffmann, Claudia; Hofer, Bernd; Unterhuber, Angelika; Poavzay, Boris; Morgner, Uwe; Drexler, Wolfgang

    2011-03-01

    Optical coherence tomography (OCT) is a non-invasive in vivo biomedical imaging modality capable of three-dimensional visualization of tissue morphology permitting imaging at high speed and sensitivity. Coherent Anti- Stokes Raman Scattering (CARS) is a nonlinear spectroscopic technique which provides molecular information due to a four wave mixing process. In order to extend the performance of OCT towards detecting the molecular fingerprint of biological samples a combined CARS/OCT setup has been developed that employs only a single ultrashort pulse Ti:Sapphire laser which enables high axial resolution OCT and simultaneously combined with a spectral shaper a CARS setup. During first measurements the same area of a sample was imaged twice, applying OCT and CARS consecutively. OCT was used to perform three-dimensional morphological screening. Due to CARS additional chemical information could be gained for two dimensions. The spectrum was modified computer controlled to match the requirements for the generation of a CARS signal whereas for OCT the unmodified spectrum was applied. Fluids such as dimethylsulfoxide (DMSO) and PBS were compared in a cuvette to demonstrate the functionality of the multimodal setup. As a biological sample a 100 m thickcr oss section through a human optic nerve surrounded by sclera was investigated.

  12. 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.

  13. Ultrashort-pulse laser machining system employing a parametric amplifier

    DOEpatents

    Perry, Michael D.

    2004-04-27

    A method and apparatus are provided for increasing the energy of chirped laser pulses to an output in the range 0.001 to over 10 millijoules at a repetition rate 0.010 to 100 kHz by using a two stage optical parametric amplifier utilizing a bulk nonlinear crystal wherein the pump and signal beam size can be independently adjusted in each stage.

  14. A broadly tunable autocorrelator for ultra-short, ultra-high power infrared optical pulses

    SciTech Connect

    Szarmes, E.B.; Madey, J.M.J.

    1995-12-31

    We describe the design of a crossed-beam, optical autocorrelator that uses an uncoated, birefringent beamsplitter to split a linearly polarized incident pulse into two orthogonally polarized pulses, and a Type II, SHG crystal to generate the intensity autocorrelation function. The uncoated beamsplitter accommodates extremely broad tunability while precluding any temporal distortion of ultrashort optical pulses at the dielectric interface, and the specific design provides efficient operation between 1 {mu}m and 4 {mu}m. Furthermore, the use of Type II SHG completely eliminates any single-beam doubling, so the autocorrelator can be operated at very shallow crossed-beam angles without generating a background pedestal. The autocorrelator has been constructed and installed in the Mark III laboratory at Duke University as a broadband diagnostic for ongoing compression experiments on the chirped-pulse FEL.

  15. Megawatt-scale average-power ultrashort pulses in an enhancement cavity.

    PubMed

    Carstens, H; Lilienfein, N; Holzberger, S; Jocher, C; Eidam, T; Limpert, J; Tünnermann, A; Weitenberg, J; Yost, D C; Alghamdi, A; Alahmed, Z; Azzeer, A; Apolonski, A; Fill, E; Krausz, F; Pupeza, I

    2014-05-01

    We investigate power scaling of ultrashort-pulse enhancement cavities. We propose a model for the sensitivity of a cavity design to thermal deformations of the mirrors due to the high circulating powers. Using this model and optimized cavity mirrors, we demonstrate 400 kW of average power with 250 fs pulses and 670 kW with 10 ps pulses at a central wavelength of 1040 nm and a repetition rate of 250 MHz. These results represent an average power improvement of one order of magnitude compared to state-of-the-art systems with similar pulse durations and will thus benefit numerous applications such as the further scaling of tabletop sources of hard x rays (via Thomson scattering of relativistic electrons) and of soft x rays (via high harmonic generation). PMID:24784054

  16. Laser induced damage in multilayer dielectric gratings due to ultrashort laser pulses. Revision 1

    SciTech Connect

    Shore, B.W.; Stuart, B.C.; Feit, M.D.; Rubenchik, A.M.; Perry, M.D.

    1995-07-11

    Chirped pulse amplification is increasingly used to produce intense ultrashort laser pulses. When high-efficiency gratings are the dispersive element, as in the LLNL Petawatt laser, their susceptibility to laser induced damage constitutes a limitation on the peak intensities that can be reached. To obtain robust gratings, it is necessary to understand the causes of short-pulse damage, and to recognize the range of design options for high efficiency gratings. Metal gratings owe their high efficiency to their high conductivity. To avoid the inevitable light absorption that accompanies conductivity, we have developed designs for high efficiency rejection gratings that use only transparent dielectric materials. These combine the reflectivity of a multi-layer dielectric stack with a diffraction grating. We report here our present understanding of short-pulse laser induced damage, as it applies to dielectric gratings.

  17. Laser induced damage in multilayer dielectric gratings due to ultrashort laser pulses

    SciTech Connect

    Shore, B.W.; Stuart, B.C.; Feit, M.D.; Rubenchik, A.M.; Perry, M.D.

    1995-05-26

    Chirped pulse amplification is increasingly used to produce intense ultrashort laser pulses. When high-efficiency gratings are the dispersive element, as in the LLNL Petawatt laser, their susceptibility to laser induced damage constitutes a limitation on the peak intensities that can be reached. To obtain robust gratings, it is necessary to understand the causes of short-pulse damage, and to recognize the range of design options for high efficiency gratings. Metal gratings owe their high efficiency to their high conductivity. To avoid the inevitable light absorption that accompanies conductivity, we have developed designs for high efficiency reflection gratings that use only transparent dielectric materials. These combine the reflectivity of a multilayer dielectric stack with a diffraction grating. We report here our present understanding of short-pulse laser induced damage, as it applies to dielectric gratings.

  18. Coherent population trapping via a continuum with a train of ultrashort pulses

    SciTech Connect

    Kuznetsova, Elena; Kolesov, Roman; Kocharovskaya, Olga

    2006-09-15

    We consider the coherent population trapping effect with a train of ultrashort pulses in a {lambda}-type system with two bound states and a continuum replacing the upper state. Population transfer to the continuum can be totally suppressed provided that the splitting between the bound states is a multiple of the pulse repetition rate. Compared to the traditional case with only two laser fields coupling the bound states to the continuum, CPT with a pulse train allows one to avoid incoherent population losses due to interaction of the fields with 'wrong' transitions, which results in only partial suppression of ionization. A method of suppression of excited-state absorption of pumping radiation in laser crystals, with pumping in the form of the pulse train, is proposed. As a particular example pumping dynamics of a Ti{sup 3+}:YAlO{sub 3} crystal using this technique is numerically analyzed.

  19. Chromium carbide thin films deposited by ultra-short pulse laser deposition

    NASA Astrophysics Data System (ADS)

    Teghil, R.; Santagata, A.; De Bonis, A.; Galasso, A.; Villani, P.

    2009-06-01

    Pulsed laser deposition performed by a laser with a pulse duration of 250 fs has been used to deposit films from a Cr 3C 2 target. Due to the different processes involved in the laser ablation when it is performed by an ultra-short pulse source instead of a conventional short pulse one, it has been possible to obtain in vacuum films containing only one type of carbide, Cr 3C 2, as shown by X-ray photoelectron spectroscopy. On the other hand, Cr 3C 2 is not the only component of the films, since a large amount of amorphous carbon is also present. The films, deposited at room temperature, are amorphous and seem to be formed by the coalescence of a large number of particles with nanometric size. The film composition can be explained in terms of thermal evaporation from particles ejected from the target.

  20. Quasi-matched propagation of ultra-short, intense laser pulses in plasma channels

    SciTech Connect

    Benedetti, C.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.

    2012-05-15

    The propagation of an ultrashort and relativistically intense laser pulse in a preformed plasma channel is investigated. The nonlinear paraxial wave equation describing the laser propagation in the plasma is solved both analytically and numerically. For any arbitrary temporal laser pulse profile with a given power (less then the critical power for self-focusing) and any prescribed transverse density profile in the channel, we determine the laser intensity distribution along the pulse ensuring quasi-matched propagation, neglecting non-paraxial effects. For the case of a Gaussian laser with an initially uniform spot throughout the pulse, we determine the optimal channel depth that minimizes laser evolution (e.g., minimizes spot size oscillations). The analytical and semi-analytical results obtained for both cases in the weakly relativistic regime are presented and validated through comparison with numerical simulations.

  1. Thermoplastic deformation of silicon surfaces induced by ultrashort pulsed lasers in submelting conditions

    SciTech Connect

    Tsibidis, G. D.; Stratakis, E.; Aifantis, K. E.

    2012-03-01

    A hybrid theoretical model is presented to describe thermoplastic deformation effects on silicon surfaces induced by single and multiple ultrashort pulsed laser irradiation in submelting conditions. An approximation of the Boltzmann transport equation is adopted to describe the laser irradiation process. The evolution of the induced deformation field is described initially by adopting the differential equations of dynamic thermoelasticity while the onset of plastic yielding is described by the von Mises stress. Details of the resulting picometre sized crater, produced by irradiation with a single pulse, are discussed as a function of the imposed conditions and thresholds for the onset of plasticity are computed. Irradiation with multiple pulses leads to ripple formation of nanometre size that originates from the interference of the incident and a surface scattered wave. It is suggested that ultrafast laser induced surface modification in semiconductors is feasible in submelting conditions, and it may act as a precursor of the incubation effects observed at multiple pulse irradiation of materials surfaces.

  2. Formation of ultrashort pulses from quasimonochromatic XUV radiation via infrared-field-controlled forward scattering

    NASA Astrophysics Data System (ADS)

    Akhmedzhanov, T. R.; Antonov, V. A.; Kocharovskaya, Olga

    2016-08-01

    We suggest a highly efficient method of ultrashort pulse formation from resonant XUV radiation due to sub-laser-cycle modulation of the excited state of non-hydrogen-like atoms by a nonionizing IR laser field. This modulation results in formation of the Raman-Stokes and anti-Stokes sidebands in coherently forward-scattered radiation, which, in turn, leads to formation of short pulses, when the phases of the sidebands are matched. This method is a generalization of a recently suggested technique [V. A. Antonov et al., Phys. Rev. A 88, 053849 (2013), 10.1103/PhysRevA.88.053849] for a non-hydrogen-like medium. The possibility to form 2-fs XUV pulses in the gas of helium atoms and 990-as XUV pulses in the plasma of Li+ ions with efficiencies over 80% is shown.

  3. Process optimization in high-average-power ultrashort pulse laser microfabrication: how laser process parameters influence efficiency, throughput and quality

    NASA Astrophysics Data System (ADS)

    Schille, Joerg; Schneider, Lutz; Loeschner, Udo

    2015-09-01

    In this paper, laser processing of technical grade stainless steel and copper using high-average-power ultrashort pulse lasers is studied in order to gain deeper insight into material removal for microfabrication. A high-pulse repetition frequency picosecond and femtosecond laser is used in conjunction with high-performance galvanometer scanners and an in-house developed two-axis polygon scanner system. By varying the processing parameters such as wavelength, pulse length, fluence and repetition rate, cavities of standardized geometry are fabricated and analyzed. From the depths of the cavities produced, the ablation rate and removal efficiency are estimated. In addition, the quality of the cavities is evaluated by means of scanning electron microscope micrographs or rather surface roughness measurements. From the results obtained, the influence of the machining parameters on material removal and machining quality is discussed. In addition, it is shown that both material removal rate and quality increase by using femtosecond compared to picosecond laser pulses. On stainless steel, a maximum throughput of 6.81 mm3/min is achieved with 32 W femtosecond laser powers; if using 187 W picosecond laser powers, the maximum is 15.04 mm3/min, respectively. On copper, the maximum throughputs are 6.1 mm3/min and 21.4 mm3/min, obtained with 32 W femtosecond and 187 W picosecond laser powers. The findings indicate that ultrashort pulses in the mid-fluence regime yield most efficient material removal. In conclusion, from the results of this analysis, a range of optimum processing parameters are derived feasible to enhance machining efficiency, throughput and quality in high-rate micromachining. The work carried out here clearly opens the way to significant industrial applications.

  4. Neutron production by 200 mJ ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Pretzler, G.; Saemann, A.; Pukhov, A.; Rudolph, D.; Schätz, T.; Schramm, U.; Thirolf, P.; Habs, D.; Eidmann, K.; Tsakiris, G. D.; Meyer-Ter-Vehn, J.; Witte, K. J.

    1998-07-01

    We report the observation of neutrons released from d(d,n)3He fusion reactions in the focus of 200 mJ, 160 fs Ti:sapphire laser pulses on a deuterated polyethylene target. Optimizing the fast electron and ion generation by applying a well-defined prepulse led to an average rate of 140 neutrons per shot. Furthermore, the production of a substantial number of MeV γ rays could be observed. The occurrence of neutrons and γ rays is attributed to the formation and explosion of a relativistic plasma channel in the laser focus, which is confirmed by numerical calculations.

  5. Characterization of fiber ultrashort pulse delivery for nonlinear endomicroscopy.

    PubMed

    Ibrahim, A; Poulon, F; Habert, R; Lefort, C; Kudlinski, A; Haidar, D Abi

    2016-06-13

    In this work, we present a detailed characterization of a small-core double-clad photonic crystal fiber, dedicated and approved for in vivo nonlinear imaging endomicroscopy. A numerical and experimental study has been performed to characterize the excitation and collection efficiencies through a 5 m-long optical fiber, including the pulse duration and spectral shape. This was first done without any distal optics, and then the performances of the system were studied by using two kinds of GRIN lenses at the fiber output. These results are compared to published data using commercial double clad fibers and GRIN lenses. PMID:27410272

  6. Wear-reducing Surface Functionalization of Implant Materials Using Ultrashort Laser Pulses

    NASA Astrophysics Data System (ADS)

    Oldorf, P.; Peters, R.; Reichel, S.; Schulz, A.-P.; Wendlandt, R.

    The aim of the project called "EndoLas" is the development of a reproducible and reliable method for a functionalization of articulating surfaces on hip joint endoprostheses due to a reduction of abrasion and wear by the generation of micro structures using ultrashort laser pulses. On the one hand, the microstructures shall ensure the capture of abraded particles, which cause third-body wear and thereby increase aseptic loosening. On the other hand, the structures shall improve or maintain the tribologically important lubricating film. Thereby, the cavities serve as a reservoir for the body's own synovial fluid. The dry friction, which promotes abrasion and is a part of the mixed friction in the joint, shall therefore be reduced. In experimental setups it was shown, that the abrasive wear can be reduced significantly due to micro-structuring the articulating implant surfaces. To shape the fine and deterministic cavities on the surfaces, an ultra-short pulsed laser, which is integrated in a high-precision, 5-axes micro-machining system, was used. The laser system, based on an Yb:YAG thin-disk regenerative amplifier, has an average output power of 50 W at the fundamental wavelength of 1030 nm, a maximum repetition rate of 400 kHz and a pulse duration of 6 ps. Due to this, a maximum pulse energy of 125 μJ is achievable. Furthermore external second and third harmonic generation enables the usage of wavelengths in the green and violet spectral range.

  7. Characterization of Focused Ultrashort Pulses as a Function of Wavelength

    NASA Astrophysics Data System (ADS)

    Beck, Joshua; McAcy, Collin; Marsh, Skyler; Karnemaat, Ryan; Scarborough, Tim; Uiterwaal, Cornelis

    2013-05-01

    In previous experiments, we have studied the photoionization and photofragmentation of substituted benzenes using intense fields from an 800 nm, femtosecond laser source and an experimental method that eliminates the focal volume effect without the need for data deconvolution [Phys. Rev. Lett. 100, 023002 (2008)]. Using this approach, we have found that in many substituted benzenes REMPI dominates the ionization process at around 800 nm [Phys. Chem. Chem. Phys., 2011, 13, 13783-13790]. We have now started to expand our studies using an optical parametric amplifier (Spectra-Physics TOPAS-C) which is tunable between 475 nm and 2800 nm. For reliable wavelength-dependent experiments, proper characterization of the position of the focus, including focal pulse duration and pulse intensity for the various wavelengths, is of crucial importance. We present preliminary characterization of post-OPA foci imaged at the interaction volume using reflective optics. Initial results will employ a spherical mirror, though the final experiment will require an off-axis parabolic mirror. Diagnosis of the focus will allow us to align this mirror and record its focal intensity distribution in real time, making accurate wavelength-dependent photoionization experiments feasible. This material is based upon work supported by the GAANN research fellowship and the National Science Foundation under Grant Nos. PHY-0855675 and PHY-1005071.

  8. Ultrashort pulse laser machining of metals and alloys

    DOEpatents

    Perry, Michael D.; Stuart, Brent C.

    2003-09-16

    The invention consists of a method for high precision machining (cutting, drilling, sculpting) of metals and alloys. By using pulses of a duration in the range of 10 femtoseconds to 100 picoseconds, extremely precise machining can be achieved with essentially no heat or shock affected zone. Because the pulses are so short, there is negligible thermal conduction beyond the region removed resulting in negligible thermal stress or shock to the material beyond approximately 0.1-1 micron (dependent upon the particular material) from the laser machined surface. Due to the short duration, the high intensity (>10.sup.12 W/cm.sup.2) associated with the interaction converts the material directly from the solid-state into an ionized plasma. Hydrodynamic expansion of the plasma eliminates the need for any ancillary techniques to remove material and produces extremely high quality machined surfaces with negligible redeposition either within the kerf or on the surface. Since there is negligible heating beyond the depth of material removed, the composition of the remaining material is unaffected by the laser machining process. This enables high precision machining of alloys and even pure metals with no change in grain structure.

  9. Nonlinear Compton scattering of ultrashort intense laser pulses

    SciTech Connect

    Seipt, D.; Kaempfer, B.

    2011-02-15

    The scattering of temporally shaped intense laser pulses off electrons is discussed by means of manifestly covariant quantum electrodynamics. We employ a framework based on Volkov states with a time-dependent laser envelope in light-cone coordinates within the Furry picture. An expression for the cross section is constructed unambiguously in respect of the pulse length. A broad distribution of scattered photons with a rich pattern of subpeaks like that obtained in Thomson scattering is found. These broad peaks may overlap at sufficiently high laser intensity, rendering inappropriate the notion of individual harmonics. The limit of monochromatic plane waves as well as the classical limit of Thomson scattering are discussed. As a main result, a scaling law is presented connecting the Thomson limit with the general result for arbitrary kinematics. In the overlapping regions of the spectral density, the classical and quantum calculations give different results, even in the Thomson limit. Thus, a phase-space region is identified where the differential photon distribution is strongly modified by quantum effects.

  10. Apparatus and method for optical pulse measurement

    SciTech Connect

    Trebino, R.P.; Tsang, T.; Fittinghoff, D.N.; Sweetser, J.N.; Krumbuegel, M.A.

    1999-12-28

    Practical third-order frequency-resolved optical grating (FROG) techniques for characterization of ultrashort optical pulses are disclosed. The techniques are particularly suited to the measurement of single and/or weak optical pulses having pulse durations in the picosecond and subpicosecond regime. The relative quantum inefficiency of third-order nonlinear optical effects is compensated for through (i) use of phase-matched transient grating beam geometry to maximize interaction length, and (ii) use of interface-enhanced third-harmonic generation.

  11. Apparatus and method for optical pulse measurement

    DOEpatents

    Trebino, Rick P.; Tsang, Thomas; Fittinghoff, David N.; Sweetser, John N.; Krumbuegel, Marco A.

    1999-12-28

    Practical third-order frequency-resolved optical grating (FROG) techniques for characterization of ultrashort optical pulses are disclosed. The techniques are particularly suited to the measurement of single and/or weak optical pulses having pulse durations in the picosecond and subpicosecond regime. The relative quantum inefficiency of third-order nonlinear optical effects is compensated for through i) use of phase-matched transient grating beam geometry to maximize interaction length, and ii) use of interface-enhanced third-harmonic generation.

  12. Simulation, part path correction, and automated process parameter selection for ultrashort pulsed laser micromachining of sapphire

    NASA Astrophysics Data System (ADS)

    Blood, Daniel A.

    This dissertation describes an ultrashort pulsed laser material removal simulator with X-Y stage acceleration profile consideration and part path compensation. Ultrashort pulsed lasers offer the advantage of single step processing of various materials with high repeatability. Over the past 30 years the laser repetition rate and power output have increased, and although this increases the material removal rate, it also introduces new challenges. The acceleration rates of the X-Y stages on a laser micromachining setup are finite, but this has been neglected. In the past the acceleration rate has been negligible due to low repetition rates; however, for high repetition rates the acceleration and deceleration regions introduce local variations in the material removal. A novel method is presented that accounts for the stage dynamics to produce a more robust simulated cut. In addition to the simulator, a technique for modifying the part path to reduce non-uniformity in the material removal is discussed. The laser operator has access to a variety of process parameters that ultimately affect the cost and quality of the machined component. Choosing the correct combination of these parameters requires knowledge of the machining process, and the wrong combination can result in a feature that is unsatisfactory and/or overly expensive. The modification of these parameters, and a correction of the part path allows for a more uniform depth of cut and higher feature quality. This dissertation contains three main contributions. The first contribution is to quantify the relationship between ultrashort pulsed laser machining parameters and the ablation depth of sapphire. The second is to produce a pulsed laser micromachining simulator that includes not only the laser-material interaction, but also the nuances of controlling the position of the laser beam on the workpiece. The final contribution is to produce a part path correction program with an automated process parameter routine

  13. Interaction of ultra-short laser pulses with CIGS and CZTSe thin films

    NASA Astrophysics Data System (ADS)

    Gečys, P.; Markauskas, E.; Dudutis, J.; Račiukaitis, G.

    2014-01-01

    The thin-film solar cell technologies based on complex quaternary chalcopyrite and kesterite materials are becoming more attractive due to their potential for low production costs and optimal spectral performance. As in all thin-film technologies, high efficiency of small cells might be maintained with the transition to larger areas when small segments are interconnected in series to reduce photocurrent and related ohmic losses in thin films. Interconnect formation is based on the three scribing steps, and the use of a laser is here crucial for performance of the device. We present our simulation and experimental results on the ablation process investigations in complex CuIn1- x Ga x Se2 (CIGS) and Cu2ZnSn(S,Se)4 (CZTSe) cell's films using ultra-short pulsed infrared (~1 μm) lasers which can be applied to the damage-free front-side scribing processes. Two types of processes were investigated—direct laser ablation of ZnO:Al/CIGS films with a variable pulse duration of a femtosecond laser and the laser-induced material removal with a picosecond laser in the ZnO:Al/CZTSe structure. It has been found that the pulse energy and the number of laser pulses have a significantly stronger effect on the ablation quality in ZnO:Al/CIGS thin films rather than the laser pulse duration. For the thin-film scribing applications, it is very important to carefully select the processing parameters and use of ultra-short femtosecond pulses does not have a significant advantage compared to picosecond laser pulses. Investigations with the ZnO:Al/CZTSe thin films showed that process of the absorber layer removal was triggered by a micro-explosive effect induced by high pressure of sublimated material due to a rapid temperature increase at the molybdenum-CZTSe interface.

  14. Investigations of the damage mechanisms during ultrashort pulse laser ablation of dental tissue

    NASA Astrophysics Data System (ADS)

    Domke, Matthias; Wick, Sebastian; Laible, Maike; Rapp, Stephan; Kuznetsova, Julia; Homann, Christian; Huber, Heinz P.; Sroka, Ronald

    2015-07-01

    Several investigations of dental tissue ablation with ultrashort pulsed lasers suggest that these lasers enable precise and selective material removal and reduce the formation of micro cracks and thermal effects, when compared to ns-pulses. In this study, two damage mechanisms are presented occurring during ablation of dentin using a laser emitting pulses of a duration of 380 fs at a wavelength of 1040 nm. First, it was found that nano cracks appear around the craters after single fs-pulse ablation. These cracks are directed to the crater and cross the dentinal tubules. Transient investigation of the single fs-pulse ablation process by pump-probe microscopy suggest that the driving mechanism could be a pressure wave that is released after stress confinement. Second, squared ablation holes were created by moving the laser focus at scan speeds between 0.5 mm/s and 2.0 m/s and fluences up to 14 J/cm2. It was found that deep cracks appear at the edges of the squared holes, if the scan speed is about 0.5 m/s. The fluence has only a minor impact on the crack formation. The crack propagation was investigated in the depth using x-ray micro tomography and optical coherence tomography. It was found that these cracks appear in the depth down to the dental pulp. These findings suggest that fast scanning of the laser beam is the key for damage free processing using ultrashort pulse lasers. Then, ablation rates of about 2.5 - 3.5 mm3/min/W can be achieved in dentine with pulse durations of 380 fs.

  15. Design and fabrication of hollow-core photonic crystal fibers for high-power ultrashort pulse transportation and pulse compression.

    PubMed

    Wang, Y Y; Peng, Xiang; Alharbi, M; Dutin, C Fourcade; Bradley, T D; Gérôme, F; Mielke, Michael; Booth, Timothy; Benabid, F

    2012-08-01

    We report on the recent design and fabrication of kagome-type hollow-core photonic crystal fibers for the purpose of high-power ultrashort pulse transportation. The fabricated seven-cell three-ring hypocycloid-shaped large core fiber exhibits an up-to-date lowest attenuation (among all kagome fibers) of 40 dB/km over a broadband transmission centered at 1500 nm. We show that the large core size, low attenuation, broadband transmission, single-mode guidance, and low dispersion make it an ideal host for high-power laser beam transportation. By filling the fiber with helium gas, a 74 μJ, 850 fs, and 40 kHz repetition rate ultrashort pulse at 1550 nm has been faithfully delivered at the fiber output with little propagation pulse distortion. Compression of a 105 μJ laser pulse from 850 fs down to 300 fs has been achieved by operating the fiber in ambient air. PMID:22859102

  16. Improving mask registration and wafer overlay control using an ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Avizemer, Dan; Dmitriev, Vladimir; Hibbs, Michael

    2016-04-01

    Requirements for control of mask registration errors and wafer overlay errors become more demanding as the integrated circuit (IC) feature size specifications become tighter and tighter. Registration control, also known as RegC, is a well-known laser-based process in the IC industry that has proven to be robust, repeatable, and efficient in adjusting mask registration and wafer overlay. Using an ultrashort pulsed laser, microscopic deformation elements, strain centers, which are also known as pixels, are generated deep inside the fused silica mask substrate causing strain. The induced strain moves the mask pattern in predicted calculated directions to reduce the measured image placement error (IPE). RegC corrections can be applied in two different ways: as a periphery-mask correction, which places the strain centers in the mask frame area outside the exposure field, or as a full-mask correction, that places the strain centers across the entire mask, including the exposure field. Relative pattern displacements up to 1 nm can be achieved between sites located at a distance of 1 mm, reducing the magnitude of the residual IPE by an average of 20% (10% to 25% range) for a periphery correction or 40% (20% to 50% range) for a full-mask correction. The input data for the RegC process are typically taken from mask registration information, which is measured by registration metrology tools or measured from wafer overlay (the latter is not within the scope of this paper). This paper reviews the RegC process flow for improving mask registration in mask shops.

  17. Ionization of the hydrogen atom by intense ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Borbély, S.; Tőkési, K.; Nagy, L.

    2008-03-01

    The ionization of atomic hydrogen in intense laser fields is studied theoretically by both quantum-mechanical and classical approaches. In the quantum-mechanical treatment we apply a momentum-space strong-field approximation (MSSFA) and the Coulomb potential is taken into account as a perturbation. The classical calculations are performed within the framework of the classical trajectory Monte Carlo method. The energy and angular distributions of the ionization probabilities of the photoelectrons are presented for different laser pulses. While for the case of low electron energies larger discrepancies can be observed between the theories in the double-differential ionization probabilities, at high electron energies the agreement is excellent. This indicates that the generation of low-energy electrons is of quantum type and it is strongly influenced by the Coulomb potential, while the production of high-energy electrons is of classical type and it is less influenced by the Coulomb interaction. Our MSSFA results are in good agreement with the most reliable calculations based on a numerical solution of the time-dependent Schrödinger equation for high momentum transfers.

  18. Hydrodynamical modeling of laser drilling with short and ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Ruf, Andreas; Breitling, Detlef; Berger, Peter; Dausinger, Friedrich; Huegel, Helmut

    2003-11-01

    This contribution examines the basic concepts and results of two laser ablation models based on commercially available hydrodynamical codes. In both cases the different material phases are described continuously by a single numerical algorithm. The first approach uses a finite-element model for the simultaneous description of solid and melt. It is thereby particularly suited for the description of melt formation and ejection. The results indicate a slow acceleration of the melt during the laser pulse up to velocities of some 10m/s followed by a rather steady-going ejection which is finally cut off by the resolidification. Although it was possible to examine this expulsion process, the model showed considerable numerical stability problems for higher intensities and the ultrasonic vapor expansion cannot be included. To overcome these shortages another model is proposed which is based on an equation of state for the target material in combination with a special pressure-based solver. Besides the continuous description of the material states, it also includes a continuous treatment of the beam propagation and energy coupling by solving Maxwell's equations. Although the work on this model is still going on, some of its basic prospects and limitations can already be discussed.

  19. Ultra-short laser pulses in dentistry: a solution toward painless dental treatment?

    NASA Astrophysics Data System (ADS)

    Wieger, V.; Yousif, A.; Strassl, M.; Wintner, E.

    2006-06-01

    Within the last years, modern ultra-short pulse lasers have successfully proven their potential for application in medical tissue treatment in many respects. In dentistry, overheating of the pulp and induction of micro cracks are usually among the most problematic issues which can be solved in this way. An additional benefit can be seen in the possibility of plasma emission spectroscopy as a means of feedback. Up till now it was shown by many authors that the application of picosecond or femtosecond pulses allows to perform ablation with very low damaging potential also fitting to the special physiological requirements. Beside the short interaction time with the irradiated biological matter, lateral scanning of ultra-short pulses following optimized algorithms turned out to be crucial for ablating cavities with the required quality and size, a finding which we also believe to be valid for dental restoration materials. Additionally, out of practical reasons, scanning is necessary to treat larger volumes than just the focal spots typically having dimensions on the order of more than 1 mm 3, thereby allowing to realize an "optical drill".

  20. Formation and evolution of ultrashort pulse-induced nanogratings in Borosilicate glass

    NASA Astrophysics Data System (ADS)

    Zimmermann, F.; Plech, Anton; Richter, S.; Tünnermann, Andreas; Nolte, S.

    2014-05-01

    The versatility of ultrashort laser pulses as a tool for laser materials processing has augmented particular interest in the past decade. Especially birefringent modifications, so-called nanogratings, have found to exhibit tremendous potential for manifold photonic functionalities. These self-assembling structures, orienting always perpendicular to the laser polarization, have been up to now extensively studied in bulk fused silica. Commonly it is assumed that the formation of nanogratings is actually limited to anomalous glasses like silica or slightly doped silica. However, we recently found that even in glasses like borosilicate or BK7 nanogratings can be observed within certain parameter regimes. Here we present an extensive study of the fundamental constituents of nanogratings in bulk borosilicate glass using small angle X-ray scattering (SAXS) in combination with focused ion beam milling (FIB) and scanning electron microscopy (SEM). The irradiation produces void-like sheets (10-20 nm wide) as well as elongated cracks of up to 400 nm. In contrast to nanogratings in fused silica, borosilicate shows a significant smaller optical retardance. The cumulative action of several hundreds of laser pulses lead to the formation of individual grating planes with a period of about 60 nm (at an inscribing laser wavelength of 800 nm) while the well-known λ/2n (n-refractive index) period is prevented. This has never been observed for ultrashort pulse induced nanogratings so far.

  1. Micro drilling using deformable mirror for beam shaping of ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Smarra, Marco; Strube, Anja; Dickmann, Klaus

    2016-03-01

    Using ultra-short laser pulses for micro structuring or drilling applications reduces the thermal influence to the surrounding material. The best achievable beam profile equals a Gaussian beam. Drilling with this beam profile results in cylindrical holes. To vary the shape of the holes, the beam can either be scanned or - for single pulse and percussion drilling - manipulated by masks or lenses. A high flexible method for beam shaping can be realized by using a deformable mirror. This mirror contains a piezo-electric ceramic, which can be deformed by an electric potential. By separating the ceramic into independent controllable segments, the shape of the surface can be varied individually. Due to the closed surface of the mirror, there is no loss of intensity due to diffraction. The mirror deformation is controlled by Zernike polynomials and results e.g. in a lens behavior. In this study a deformable mirror was used to generate e.g. slits in thin steel foils by percussion drilling using ultra-short laser pulses. The influence of the cylindrical deformation to the laser beam and the resulting geometry of the generated holes was studied. It was demonstrated that due to the high update rate up to 150 Hz the mirror surface can be varied in each scan cycle, which results in a high flexible drilling process.

  2. Variational analysis of self-focusing of intense ultrashort pulses in gases

    SciTech Connect

    Arevalo, E.; Becker, A.

    2005-08-01

    By using perturbation theory we derive an expression for the electrical field of a Gaussian laser beam propagating in a gas medium. This expression is used as a trial solution in a variational method to get quasianalytical solutions for the width, intensity, and self-focusing distance. The approximation gives a better agreement with results of numerical simulations for a broad range of values of the input power than previous analytical results available in the literature. The results apply in the case of ultrashort pulses too.

  3. A proposal for the generation of ultra-short x-ray pulses

    SciTech Connect

    Zholents, A.A.; Zolotorev, M.S.

    1994-08-01

    In this paper it is shown that optical stochastic cooling in a 150 MeV electron storage ring will allow production of a beam with longitudinal emittance 4.5 {times} 10{sup {minus}6} MeV{center_dot}m. Such a small emittance accompanied with a bunch compression technique based upon the transformation in the longitudinal phase space will allow achieving a bunch length 30 {mu}m. This bunch could then be used for the generation of ultra-short x-ray pulses by the Compton scattering of laser photons.

  4. Photonic approach to the selective inactivation of viruses with a near-infrared ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Tsen, K. T.; Tsen, Shaw-Wei D.; Fu, Q.; Lindsay, S. M.; Kibler, K.; Jacobs, B.; Wu, T. C.; Li, Zhe; Yan, Hao; Cope, Stephanie; Vaiana, Sara; Kiang, Juliann G.

    2010-02-01

    We report a photonic approach for selective inactivation of viruses with a near-infrared ultrashort pulsed (USP) laser. We demonstrate that this method can selectively inactivate viral particles ranging from nonpathogenic viruses such as M13 bacteriophage, tobacco mosaic virus (TMV) to pathogenic viruses like human papillomavirus (HPV) and human immunodeficiency virus (HIV). At the same time sensitive materials like human Jurkat T cells, human red blood cells, and mouse dendritic cells remain unharmed. Our photonic approach could be used for the disinfection of viral pathogens in blood products and for the treatment of blood-borne viral diseases in the clinic.

  5. Ultrashort pulse lasers for precise processing: overview on a current German research initiative

    NASA Astrophysics Data System (ADS)

    Nolte, S.

    2014-03-01

    Ultrashort laser pulses provide a powerful means of processing a wide variety of materials with highest precision and minimal damage. In order to exploit the full potential of this technology, the German Federal Ministry of Education and Research has launched an initiative with 20 Million EUR funding about two years ago. Within 9 joint research projects, different aspects from novel concepts for robust and powerful laser sources to reliable components with high damage thresholds and dynamic beam shaping and steering are investigated. Applications include eye surgery as well as the processing of semiconductors, carbon fiber reinforced plastics and metals. The paper provides an overview on the different projects and highlights first results.

  6. Harmonic generation during ultrashort-pulse ultraintense /p-polarized laser interaction with solid target

    NASA Astrophysics Data System (ADS)

    Wu, Shuai; Zhan, Ru-Juan; Chen, Ji

    2001-07-01

    In this Letter, we developed the “relativistic surface currents” model to investigate the harmonic generation under the conditions of p-polarized obliquely incident ultrashort-pulse ultraintense laser. As a result of this Letter, up to 70 harmonics are generated with conversion efficiencies exceeding 10 -6, which is very close to the result from Norreys' experiment and Gibbon's PIC simulations. For highly relativistic regime and nonrelativistic regime of laser power, the harmonic conversion efficiencies as a function of laser strength parameter q are discussed.

  7. Propagation of Super-intense and Ultra-short Laser Pulses in Plasmas

    NASA Astrophysics Data System (ADS)

    Giulietti, Danilo

    The propagation of super-intense and ultra-short laser pulses in plasmas is a main concern in several applications of the laser-plasma interactions, from Inertial Confinement Fusion (ICF) to High Energy Physics (HEP). During the propagation in the plasma the light beam deeply changes its parameters due the onset of non-linear effects, among them the relativistic regime of the electron quivering motion. These extreme conditions are suitable for the electron acceleration in high field gradient, opening the way for the realization of compact secondary sources of X-gamma rays.

  8. Microcavity design for low threshold polariton condensation with ultrashort optical pulse excitation

    SciTech Connect

    Poellmann, C.; Leierseder, U.; Huber, R.; Galopin, E.; Lemaître, A.; Amo, A.; Bloch, J.; Ménard, J.-M.

    2015-05-28

    We present a microcavity structure with a shifted photonic stop-band to enable efficient non-resonant injection of a polariton condensate with spectrally broad femtosecond pulses. The concept is demonstrated theoretically and confirmed experimentally for a planar GaAs/AlGaAs multilayer heterostructure pumped with ultrashort near-infrared pulses while photoluminescence is collected to monitor the optically injected polariton density. As the excitation wavelength is scanned, a regime of polariton condensation can be reached in our structure at a consistently lower fluence threshold than in a state-of-the-art conventional microcavity. Our microcavity design improves the polariton injection efficiency by a factor of 4, as compared to a conventional microcavity design, when broad excitation pulses are centered at a wavelength of λ = 740 nm. Most remarkably, this improvement factor reaches 270 when the excitation wavelength is centered at 750 nm.

  9. Transient phenomena in a thin film of a three-level atom model with ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Gaivan, S. L.; Khadzhi, P. I.

    1999-03-01

    A theoretical investigation is reported of the coherent nonlinear response of excitons and biexcitons in a thin semiconductor film subjected to resonant laser radiation. It is shown that saturation of an exciton transition results in an abrupt qualitative change in the nature of film transition from the regime of total reflection of the incident pulse at low pump amplitudes to oscillatory reflection at high amplitudes. A new area theorem is derived for ultrashort pulses: it establishes a correspondence between the areas of the incident, transmitted and reflected pulses. Anomalous transmission and reflection is predicted for large values of the nonlinear parameter. The equations of the state, describing bistable behavior of the amplitudes of the fields of the transmitted and reflected radiation, are derived for quasi-cw operation.

  10. Rotations of molecular photoelectron angular distributions with intense ultrashort circularly polarized attosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Chelkowski, Szczepan; Bandrauk, André D.

    2013-04-01

    Molecular photoelectron angular distributions (MPADs) by intense (I0 ⩾ 1014 W/cm2) circularly polarized ultrashort, few cycle (attosecond) ultraviolet laser pulses are presented from numerical solutions of time dependent Schrödinger equations. For the aligned molecular ion H_2^+, the MPADs exhibit rotations with respect to the polarization and molecular symmetry axes which are determined by the symmetry of the initial electronics states. It is also found that the rotation angle of MPADs is insensitive to the pulse intensity. We attribute these effects to the asymmetry between the parallel and perpendicular (to the molecular axis) polarization photoionization. Influence of the molecular alignment and ionizing pulse ellipticity on the rotation of MPADs is also shown to allow control of the nonsymmetric ionization.

  11. Mechanism for membrane electroporation irreversibility under high-intensity, ultrashort electrical pulse conditions

    NASA Astrophysics Data System (ADS)

    Joshi, R. P.; Schoenbach, K. H.

    2002-11-01

    An improved electroporation model is used to address membrane irreversibility under ultrashort electric pulse conditions. It is shown that membranes can survive a strong electric pulse and recover provided the pore distribution has a relatively large spread. If, however, the population consists predominantly of larger radii pores, then irreversibility can result. Physically, such a distribution could arise if pores at adjacent sites coalesce. The requirement of close proximity among the pore sites is more easily satisfied in smaller organelles than in outer cell membranes. Model predictions are in keeping with recent observations of cell damage to intracellular organelles (e.g., mitochondria), without irreversible shock at the outer membranes, by a nanosecond, high-intensity electric pulse. This mechanism also explains the greater damage from multiple electric shocks.

  12. Nonlinear relativistic interaction of an ultrashort laser pulse with a cold plasma

    SciTech Connect

    Rax, J.M.; Fisch, N.J.

    1992-01-01

    We investigate the nonlinear, relativistic dynamics that result when intense (10{sup 18}W/cm{sup 2} and above) and ultrashort (one plasma period or shorter) laser pulse travels through a cold underdense plasma. Using a Lagrangian analysis of the plasma response, it can be demonstrated that the nonlinear wake, the collective dissipation, the nonlinear Compton losses, and the harmonic generation, are all determined by a finite set of integrated scalar quantities. This result holds for one-dimensional, short pulses of arbitrary amplitude, shape, and polarization, so that these very short intense laser pulses in a plasma can be viewed essentially as a quasiparticle characterized by a small set of global parameters.

  13. Ultrashort pulse control of space-dependent excitations in a three-level system

    NASA Astrophysics Data System (ADS)

    Loiko, Yu.; Serrat, C.; Vilaseca, R.; Ahufinger, V.; Mompart, J.; Corbalán, R.

    2007-02-01

    Coherent control of regions with spatial excitation of populations and coherence between two lower states in three-level Λ -type quantum systems mediated by the self-induced transparency (SIT) phenomenon is theoretically investigated with one- and two-color ultrashort pulses and with pulse sequences beyond the slowly varying envelope (SVEA) and rotating wave (RWA) approximations. The effects of different parameters characterizing the pulses and the medium on the location as well as the width of such excited regions have been studied numerically by means of the finite-difference time-domain (FDTD) method. It has been determined that with a scheme of two-pulse excitation one can effectively control the position at which the region is written and its width. In particular, the position of the excited region can be controlled by the area of the pulses. We find that the maximum value of the population transferred to the lower excited state depends on the detuning of the pulses with respect to the one-photon resonances, and that both position and width of the region also depend on the temporal duration of the pulses. We show how after the excited region is written, its position can be shifted by additional pulses. On the basis of numerical results, scaling laws are formulated for the reported phenomena. With such control, the width of the region excited inside the medium can be reduced to the order of the wavelength of the light.

  14. Electron beam-based sources of ultrashort x-ray pulses.

    SciTech Connect

    Zholents, A.; Accelerator Systems Division

    2010-09-30

    A review of various methods for generation of ultrashort x-ray pulses using relativistic electron beam from conventional accelerators is presented. Both spontaneous and coherent emission of electrons is considered. The importance of the time-resolved studies of matter at picosecond (ps), femtosecond (fs), and atttosecond (as) time scales using x-rays has been widely recognized including by award of a Nobel Prize in 1999 [Zewa]. Extensive reviews of scientific drivers can be found in [BES1, BES2, BES3, Lawr, Whit]. Several laser-based techniques have been used to generate ultrashort x-ray pulses including laser-driven plasmas [Murn, Alte, Risc, Rose, Zamp], high-order harmonic generation [Schn, Rund, Wang, Arpi], and laser-driven anode sources [Ande]. In addition, ultrafast streak-camera detectors have been applied at synchrotron sources to achieve temporal resolution on the picosecond time scale [Wulf, Lind1]. In this paper, we focus on a different group of techniques that are based on the use of the relativistic electron beam produced in conventional accelerators. In the first part we review several techniques that utilize spontaneous emission of electrons and show how solitary sub-ps x-ray pulses can be obtained at existing storage ring based synchrotron light sources and linacs. In the second part we consider coherent emission of electrons in the free-electron lasers (FELs) and review several techniques for a generation of solitary sub-fs x-ray pulses. Remarkably, the x-ray pulses that can be obtained with the FELs are not only significantly shorter than the ones considered in Part 1, but also carry more photons per pulse by many orders of magnitude.

  15. Effect of gas heating on the generation of an ultrashort avalanche electron beam in the pulse-periodic regime

    NASA Astrophysics Data System (ADS)

    Baksht, E. Kh.; Burachenko, A. G.; Lomaev, M. I.; Sorokin, D. A.; Tarasenko, V. F.

    2015-07-01

    The generation of an ultrashort avalanche electron beam (UAEB) in nitrogen in the pulse-periodic regime is investigated. The gas temperature in the discharge gap of the atmospheric-pressure nitrogen is measured from the intensity distribution of unresolved rotational transitions ( C 3Π u , v' = 0) → ( B 3Π g , v″ = 0) in the nitrogen molecule for an excitation pulse repetition rate of 2 kHz. It is shown that an increase in the UAEB current amplitude in the pulse-periodic regime is due to gas heating by a series of previous pulses, which leads to an increase in the reduced electric field strength as a result of a decrease in the gas density in the zone of the discharge formation. It is found that in the pulse-periodic regime and the formation of the diffuse discharge, the number of electrons in the beam increases by several times for a nitrogen pressure of 9 × 103 Pa. The dependences of the number of electrons in the UAEB on the time of operation of the generator are considered.

  16. Self-Guiding of Ultrashort Relativistically Intense Laser Pulses to the Limit of Nonlinear Pump Depletion

    SciTech Connect

    Ralph, J. E.; Marsh, K. A.; Pak, A. E.; Lu, W.; Clayton, C. E.; Fang, F.; Joshi, C.; Tsung, F. S.; Mori, W. B.

    2009-01-22

    A study of self-guiding of ultra short, relativistically intense laser pulses is presented. Here, the laser pulse length is on the order of the nonlinear plasma wavelength and the normalized vector potential is greater than one. Self-guiding of ultrashort laser pulses over tens of Rayliegh lengths is possible when driving a highly nonlinear wake. In this case, self-guiding is limited by nonlinear pump depletion. Erosion of the pulse due to diffraction at the head of the laser pulse is minimized for spot sizes close to the blow-out radius. This is due to the slowing of the group velocity of the photons at the head of the laser pulse. Using an approximately 10 TW Ti:Sapphire laser with a pulse length of approximately 50 fs, experimental results are presented showing self-guiding over lengths exceeding 30 Rayliegh lengths in various length Helium gas jets. Fully explicit 3D PIC simulations supporting the experimental results are also presented.

  17. Nanofractal structure consisting of nanoparticles produced by ultrashort laser pulses

    SciTech Connect

    Nishikawa, Kumiko; Takano, Kei; Miyahara, Hidekazu; Kawamura, Tohru; Okino, Akitoshi; Hotta, Eiki; Nayuki, Takuya; Oishi, Yuji; Fujii, Takashi; Wang, Xiaofang; Nemoto, Koshichi

    2006-12-11

    By irradiating subpicosecond laser onto an iron plate, a nanofibrous structure consisting of iron nanoparticles with diameters less than 12 nm was produced. The nanofibrous structure was found to be three-dimensional fractal, and its fractal dimension measured from field-emission scanning electron microscopy images conserved the same fractal dimension of 1.73 in the wide-scale range from 30 nm to 60 {mu}m, and the smallest fractal structure was less than 10 nm. The growth of this fractal is related to the cluster-cluster aggregation model, and it suggests that the fractal structure grew by the attachment of clusters consisting of nanoparticles.

  18. REVIEWS OF TOPICAL PROBLEMS: Let there be white light: supercontinuum generation by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Zheltikov, Aleksei M.

    2006-06-01

    Three centuries after Newton's experiments on the decomposition of white light into its spectral components and the synthesis of white light from various colors, nonlinear-optical transformations of ultrashort laser pulses have made it possible to produce an artificial white light with unique spectral properties, controlled time duration, and a high spectral brightness. Owing to its broad and continuous spectrum, such radiation is called supercontinuum. The laser generation of white light is an interesting physical phenomenon and the relevant technology is gaining in practical implications — it offers novel solutions for optical communications and control of ultrashort laser pulses, helps to achieve an unprecedented precision in optical metrology, serves to probe the atmosphere of the Earth, and suggests new strategies for the creation of compact multiplex light sources for nonlinear spectroscopy, microscopy, and laser biomedicine. Here, we provide a review of physical mechanisms behind the laser generation of white light, examine its applications, and discuss the methods of generation of broadband radiation with controlled spectral, temporal, and phase parameters.

  19. Heat generation caused by ablation of dental hard tissues with an ultrashort pulse laser (USPL) system.

    PubMed

    Braun, Andreas; Krillke, Raphael Franz; Frentzen, Matthias; Bourauel, Christoph; Stark, Helmut; Schelle, Florian

    2015-02-01

    Heat generation during the removal of dental hard tissues may lead to a temperature increase and cause painful sensations or damage dental tissues. The aim of this study was to assess heat generation in dental hard tissues following laser ablation using an ultrashort pulse laser (USPL) system. A total of 85 specimens of dental hard tissues were used, comprising 45 specimens of human dentine evaluating a thickness of 1, 2, and 3 mm (15 samples each) and 40 specimens of human enamel with a thickness of 1 and 2 mm (20 samples each). Ablation was performed with an Nd:YVO4 laser at 1,064 nm, a pulse duration of 9 ps, and a repetition rate of 500 kHz with an average output power of 6 W. Specimens were irradiated for 0.8 s. Employing a scanner system, rectangular cavities of 1-mm edge length were generated. A temperature sensor was placed at the back of the specimens, recording the temperature during the ablation process. All measurements were made employing a heat-conductive paste without any additional cooling or spray. Heat generation during laser ablation depended on the dental hard tissue (enamel or dentine) and the thickness of the respective tissue (p < 0.05). Highest temperature increase could be observed in the 1-mm thickness group for enamel. Evaluating the 1-mm group for dentine, a significantly lower temperature increase could be measured (p < 0.05) with lowest values in the 3-mm group (p < 0.05). A time delay for temperature increase during the ablation process depending on the material thickness was observed for both hard tissues (p < 0.05). Employing the USPL system to remove dental hard tissues, heat generation has to be considered. Especially during laser ablation next to pulpal tissues, painful sensations and potential thermal injury of pulp tissue might occur. PMID:23666547

  20. Amplification of ultra-short laser pulses via resonant backward Raman amplification in plasma

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Andreev, A.

    2016-08-01

    In this paper, we have examined the possibility of using resonant backward Raman amplification (BRA) as an efficient mechanism in amplifying the low intensity ultra-short ( ≤ fs ) pulses using plasma as intermediate amplifying medium; such pulses are anticipated to get produced in the form of the secondary sources at ALPS (Attosecond Light Pulse Source) center of ELI (Extreme Light Infrastructure). In preliminary assessment of the scheme, the analytical expressions for the pump/seed laser pulses and plasma characteristic features are obtained which concisely describe the parameter regime of resonant BRA applicability in achieving significant amplification. The consistency of the scheme in the context of ELI-ALPS sources has been validated through particle in cell (PIC) simulations. The peak intensity of the amplified seed pulse predicted via simulation results is found in reasonable agreement with the analytical estimates. Utilizing these analytical expressions as a basis in perspective of ELI-ALPS parameter access, a specific example displaying the key plasma and laser parameters for amplifying weak seed pulse has been configured; the limitations and conceivable remedies in resonant BRA implementation have also been highlighted.

  1. 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.

  2. 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.

  3. Phase engineered wavelength conversion of ultra-short optical pulses in TI:PPLN waveguides

    NASA Astrophysics Data System (ADS)

    Babazadeh, Amin; Nouroozi, Rahman; Sohler, Wolfgang

    2016-02-01

    A phase engineered all-optical wavelength converter for ultra-short pulses (down to 140 fs) in a Ti-diffused, periodically poled lithium niobate (Ti:PPLN) waveguide is proposed. The phase engineering, due to the phase conjugation between signal and idler (converted signal) pulses which takes place in the cascaded second harmonic generation and difference frequency generation (cSHG/DFG) based wavelength conversion, already leads to shorter idler pulses. The proposed device consists of an unpoled (passive) waveguide section beside of the PPLN waveguide section in order to compensate pulse broadening and phase distortion of the idler pulses induced by the wavelength conversion (in the PPLN section). For example numerical analysis shows that a 140 fs input signal pulse is only broadened by 1.6% in a device with a combination of 20 mm and 6 mm long periodically poled and unpoled waveguide sections. Thus, cSHG/DFG based wavelength converters of a bandwidth of several Tbits/s can be designed.

  4. Self similar solution of superradiant amplification of ultrashort laser pulses in plasma

    SciTech Connect

    Moghadasin, H.; Niknam, A. R. Shokri, B.

    2015-05-15

    Based on the self-similar method, superradiant amplification of ultrashort laser pulses by the counterpropagating pump in a plasma is investigated. Here, we present a governing system of partial differential equations for the signal pulse and the motion of the electrons. These equations are transformed to ordinary differential equations by the self-similar method and numerically solved. It is found that the increase of the signal intensity is proportional to the square of the propagation distance and the signal frequency has a red shift. Also, depending on the pulse width, the signal breaks up into a train of short pulses or its duration decreases with the inverse square root of the distance. Moreover, we identified two distinct categories of the electrons by the phase space analysis. In the beginning, one of them is trapped in the ponderomotive potential well and oscillates while the other is untrapped. Over time, electrons of the second kind also join to the trapped electrons. In the potential well, the electrons are bunched to form an electron density grating which reflects the pump pulse into the signal pulse. It is shown that the backscattered intensity is enhanced with the increase of the electron bunching parameter which leads to the enhanced efficiency of superradiant amplification.

  5. Shock wave acceleration of protons in inhomogeneous plasma interacting with ultrashort intense laser pulses

    SciTech Connect

    Lecz, Zs.; Andreev, A.

    2015-04-15

    The acceleration of protons, triggered by solitary waves in expanded solid targets is investigated using particle-in-cell simulations. The near-critical density plasma is irradiated by ultrashort high power laser pulses, which generate the solitary wave. The transformation of this soliton into a shock wave during propagation in plasma with exponentially decreasing density profile is described analytically, which allows to obtain a scaling law for the proton energy. The high quality proton bunch with small energy spread is produced by reflection from the shock-front. According to the 2D simulations, the mechanism is stable only if the laser pulse duration is shorter than the characteristic development time of the parasitic Weibel instability.

  6. On the surface topography of ultrashort laser pulse treated steel surfaces

    NASA Astrophysics Data System (ADS)

    Vincenc Obona, J.; Ocelík, V.; Skolski, J. Z. P.; Mitko, V. S.; Römer, G. R. B. E.; Huis in't Veld, A. J.; De Hosson, J. Th. M.

    2011-12-01

    This paper concentrates on observations of the surface topography by scanning electron microscopy (SEM) on alloyed and stainless steels samples treated by ultrashort laser pulses with duration of 210 fs and 6.7 ps. Globular-like and jet-like objects were found depending on the various levels of the fluence applied. It is shown that these features appear due to solid-liquid and liquid-gas transitions within surface layer irradiated by intense laser light. The observations are confronted to the theory of short-pulsed laser light-matter interactions, including interference, excitation of electrons, electron-phonon coupling as well as subsequent ablation. It is shown that the orientation of small ripples does not always depend on the direction of the polarization of laser light.

  7. Selective inactivation of human immunodeficiency virus with an ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Tsen, K. T.; Tsen, Shaw-Wei D.; Hung, Chien-Fu; Wu, T.-C.; Kibler, Karen; Jacobs, Bert; Kiang, Juliann G.

    2009-02-01

    Recently, femtosecond laser technology has been shown to be effective in the inactivation of non-pathogenic viruses. In this paper, we demonstrate for the first time that infectious numbers of pathogenic viruses such as Human Immunodeficiency Virus (HIV) can be reduced by irradiation with subpicosecond near infrared laser pulses at a moderate laser power density. By comparing the threshold laser power density for the inactivation of HIV with those of human red blood cells and mouse dendritic cells, we conclude that it is plausible to use the ultrashort pulsed laser to selectively inactivate blood-borne pathogens such as HIV while leaving the sensitive materials like human red blood cells unharmed. This finding has important implications in the development of a new laser technology for disinfection of viral pathogens in blood products and in the clinic.

  8. Step-ladder Rabi oscillations in molecules exposed to intense ultrashort vuv pulses

    SciTech Connect

    Palacios, A.; Martin, F.; Bachau, H.

    2006-09-15

    We theoretically investigate the production of Rabi-type oscillations in two-photon resonant ionization of H{sub 2} by intense ultrashort vuv pulses. We show that, with such pulses, oscillations proceed through a step-ladder mechanism that successively involves higher and higher vibrational levels of the lower and upper electronic states. The consequences of this mechanism are (i) the relatively large proportion of H{sub 2} molecules in excited electronic states not accessible by direct photon absorption, (ii) the splitting in the energy distribution of ionized electrons, and (iii) the unusually broad (non-Franck-Condon) vibrational distribution of both H{sub 2} and H{sub 2}{sup +}.

  9. Thermal ablation of thin gold films irradiated by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Li, Ling; Zhao, Shiqiang

    2016-04-01

    The vaporization process of gold film irradiated by ultrashort-pulsed laser is investigated using the parabolic two-step model and the dual-hyperbolic two-step model. The liquid-vapor interfacial velocity in the vaporization process is obtained by considering the interface energy balance equation and gas kinetics law. Comparisons between the temperature, velocity and location of the interface based on two different models are presented, the results show a great difference between them. In addition, the variation of ablation depth with pulse widths and fluence are also compared. The effects of laser parameters and film thickness on vaporization process are investigated. The relationship between the maximum temperature, velocity of liquid-vapor interface and laser fluence are also studied.

  10. Shock ion acceleration by an ultrashort circularly polarized laser pulse via relativistic transparency in an exploded target.

    PubMed

    Kim, Young-Kuk; Cho, Myung-Hoon; Song, Hyung Seon; Kang, Teyoun; Park, Hyung Ju; Jung, Moon Youn; Hur, Min Sup

    2015-10-01

    We investigated ion acceleration by an electrostatic shock in an exploded target irradiated by an ultrashort, circularly polarized laser pulse by means of one- and three-dimensional particle-in-cell simulations. We discovered that the laser field penetrating via relativistic transparency (RT) rapidly heated the upstream electron plasma to enable the formation of a high-speed electrostatic shock. Owing to the RT-based rapid heating and the fast compression of the initial density spike by a circularly polarized pulse, a new regime of the shock ion acceleration driven by an ultrashort (20-40 fs), moderately intense (1-1.4 PW) laser pulse is envisaged. This regime enables more efficient shock ion acceleration under a limited total pulse energy than a linearly polarized pulse with crystal laser systems of λ∼1μm. PMID:26565351

  11. On the study of pulse evolution in ultra-short pulse mode-locked fiber lasers by numerical simulations.

    PubMed

    Schreiber, Thomas; Ortaç, Bülend; Limpert, Jens; Tünnermann, Andreas

    2007-06-25

    In this contribution we highlight several aspects concerning the numerical simulation of ultra-short pulse mode-locked fiber lasers by a non-distributed model. We show that for fixed system parameters multiple attractors are accessible by different initial conditions especially in the transient region between different mode-locking regimes. The reduction of multiple attractors stabilizing from different quantum noise fields to a single solution by gain ramping is demonstrated. Based on this analysis and model, different regimes of mode-locking obtained by varying the intra-cavity dispersion and saturation energy of the gain fiber are revised and it is shown that a regime producing linearly chirped parabolic pulses known from self-similar evolution is embedded in the wave-breaking free mode-locking regime. PMID:19547154

  12. Characterization of near-infrared low energy ultra-short laser pulses for portable applications of laser induced breakdown spectroscopy.

    PubMed

    Schill, Alexander W; Heaps, David A; Stratis-Cullum, Dimitra N; Arnold, Bradley R; Pellegrino, Paul M

    2007-10-17

    We report on the delivery of low energy ultra-short (<1 ps) laser pulses for laser induced breakdown spectroscopy (LIBS). Ultra-short pulses have the advantage of high peak irradiance even at very low pulse energies. This opens the possibility to use compact, rare-earth doped fiber lasers in a portable platform for point detection applications using LIBS for elemental analysis. The use of low energy ultra-short pulses minimizes the generation of a broad continuum background in the emission spectrum, which permits the use of non-gated detection schemes using very simple and compact spectrometers. The pulse energies used to produce high-quality LIBS spectra in this investigation are some of the lowest reported and we investigate the threshold pulse requirements for a number of near IR pulse wavelengths (785-1500 nm) and observe that the pulse wavelength has no effects on the threshold for observation of plasma emission or the quality of the emission spectra obtained. PMID:19550677

  13. Sudden perturbation approximations for interaction of atoms with intense ultrashort electromagnetic pulses

    NASA Astrophysics Data System (ADS)

    Lugovskoy, Andrey; Bray, Igor

    2015-12-01

    The response of an atom to the action of a pulse shorter than the Kepler period of the optically-active electron is often treated analytically using the sudden-perturbation approximation (SPA). It relies on the truncation of the evolution operator expansion in a series over the dimensionless parameter ɛ sys τ L, where ɛ sys is the system-dependent characteristic energy and τ L is the pulse duration. We examine the SPA with the use of a basis-based solution of the time-dependent Schrödinger equation (TDSE) for the case of a hydrogen atom interacting with two different types of ultrashort pulses, a half-cycle pulse and a few-cycle pulse. The length-gauge form of the electron-field interaction potential is used. The SPA transition probabilities are shown to deviate slightly but systematically from the correct values for the positive-energy states in the region where the sudden-perturbation condition is violated. It is shown that the SPA expectation value of the electron displacement as a function of time differ qualitatively from what follows from the ab initio TDSE solution. Nevertheless, the SPA is shown to be a good approximation for the description of the expectation value of the electron momentum.

  14. 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.

  15. High-throughput machining using high average power ultrashort pulse lasers and ultrafast polygon scanner

    NASA Astrophysics Data System (ADS)

    Schille, Joerg; Schneider, Lutz; Streek, André; Kloetzer, Sascha; Loeschner, Udo

    2016-03-01

    In this paper, high-throughput ultrashort pulse laser machining is investigated on various industrial grade metals (Aluminium, Copper, Stainless steel) and Al2O3 ceramic at unprecedented processing speeds. This is achieved by using a high pulse repetition frequency picosecond laser with maximum average output power of 270 W in conjunction with a unique, in-house developed two-axis polygon scanner. Initially, different concepts of polygon scanners are engineered and tested to find out the optimal architecture for ultrafast and precision laser beam scanning. Remarkable 1,000 m/s scan speed is achieved on the substrate, and thanks to the resulting low pulse overlap, thermal accumulation and plasma absorption effects are avoided at up to 20 MHz pulse repetition frequencies. In order to identify optimum processing conditions for efficient high-average power laser machining, the depths of cavities produced under varied parameter settings are analyzed and, from the results obtained, the characteristic removal values are specified. The maximum removal rate is achieved as high as 27.8 mm3/min for Aluminium, 21.4 mm3/min for Copper, 15.3 mm3/min for Stainless steel and 129.1 mm3/min for Al2O3 when full available laser power is irradiated at optimum pulse repetition frequency.

  16. Dispersive and dissipative medium response to an ultrashort pulse: A Green's function approach

    NASA Astrophysics Data System (ADS)

    Wilhelmsson, Hans; Trombert, Jean-Hughes; Eloy, Jean-François

    1995-07-01

    The propagation of an ultrashort pulse in a dispersive and dissipative medium may conveniently be described by using a Green's function analysis. The advantage would be that all details of the initial pulse, however short, could be probed by an "infinitely" sharp δ-pulse and subsequently deciphered in a modified form, after the influence of the medium, at a later time and at a new observation point. The Green's function for a dispersive and dissipative, plasma or dielectric (molecular) medium, is constructed for an infinitely extended three-dimensional case by using symbolic algebra for time-differential operators. The solution consists of two parts: a displaced δ-function part and a Bessel-function part, describing a wake field which for dominating dispersion is of oscillatory nature. For a certain ratio between the dispersive and dissipative parameters (plasma frequency and damping) a critical limit is found where the wake oscillations disappear completely. In the particular limits of vanishing dispersion or vanishing dissipation one recovers from the generalized solution the well-known results for a pure conductor (metal) and a pure dispersive medium (cold collisionless plasma) described by the Klein-Gordon equation. The response of the medium to an initially localized ulrashort electromagnetic pulse, of an arbitrary shape, can be expressed by an integral in time and space, of the product of the Green's function and the initial pulse.

  17. Unexpected Behavior on Nonlinear Tunneling of Chirped Ultrashort Soliton Pulse in Non-Kerr Media with Raman Effect

    NASA Astrophysics Data System (ADS)

    Rajan, M. S. Mani

    2016-08-01

    In this manuscript, the ultrashort soliton pulse propagation through nonlinear tunneling in cubic quintic media is investigated. The effect of chirping on propagation characteristics of the soliton pulse is analytically investigated using similarity transformation. In particular, we investigate the propagation dynamics of ultrashort soliton pulse through dispersion barrier for both chirp and chirp-free soliton. By investigating the obtained soliton solution, we found that chirping has strong influence on soliton dynamics such as pulse compression with amplification. These two important dynamics of chirped soliton in cubic quintic media open new possibilities to improve the solitonic communication system. Moreover, we surprisingly observe that a dispersion well is formed for the chirped case whereas a barrier is formed for the chirp-free case, which has certain applications in the construction of logic gate devices to achieve ultrafast switching.

  18. Ionization-induced dynamics of ultrashort laser pulses focused in a dense gas

    NASA Astrophysics Data System (ADS)

    Efimenko, E. S.; Kim, A. V.; Quiroga-Teixeiro, M.

    2009-10-01

    In the present paper we address several aspects of ionization-induced laser-gas interaction. First, we consider the ionization dynamics of an ultrashort laser pulse in the presence of additional electromagnetic perturbations, and show theoretically via dispersion relation analysis and numerically via 2D FDTD simulation that ionizationinduced scattering can occur even in the case of limited spatial and temporal scales and significantly affects pulse dynamics. Second, for the case of tight focusing of laser beam we show on the basis of numerical simulation that for 2D TE- and TM-polarized pulses there is a critical angle which delimits two qualitatively different regimes. For angles exceeding the critical one, the formed plasma distribution may become microstructured, otherwise the plasma structures are smooth. It is also shown than the critical angle and plasma-field dynamics depend significantly on pulse spectrum. Finally, we consider the impact of the electron collisions and Kerr nonlinearity and determine the boundaries within which the role of these effects is crucial.

  19. Progress on developing a PW ultrashort laser facility with ns, ps, and fs outputting pulses

    NASA Astrophysics Data System (ADS)

    Zhu, Qihua; Huang, Xiaojun; Wang, Xiao; Zeng, Xiaoming; Xie, Xudong; Wang, Fang; Wang, Fengrui; Lin, Donghui; Wang, Xiaodong; Zhou, Kainan; Jiang, Dongbin; Deng, Wu; Zuo, Yanlei; Zhang, Ying; Deng, Ying; Wei, Xiaofeng; Zhang, Xiaomin; Fan, Dianyuan

    2008-03-01

    A petawatt laser facility with three beams for fast ignition research and strong-field physics applications has been designed and is being constructed. The first beam (referred as SILEX-I) is a Ti:sapphire femto-second laser which pulse width is 30 fs, and till now, output power has reached to 330 TW. The other two beams are Nd 3+:glass lasers which output energy are larger than 1kJ and pulse width are about 1ps and 1ns respectively. By using the technology of OPA pumped by 800nm femtosecond laser and seeded by super-continuum spectrum white light, the three beams are synchronized with each other without jitter time. By using the seeds from OPA pumped by femtosecond laser, and by using the pre-amplification stage of OPCPA, the signal to noise ratio of the Nd 3+:glass petawatt laser will reach to 10 8. Active methods are taken to control the gain narrowing effect of the Nd 3+:glass amplifiers, giving the option to compress the chirped pulse to ultrashort pulse with width less than 400fs. Tiled multilayer dielectric coating gratings are used for the compressor of the PW beam, which has been successfully demonstrated on a 100J picosecond Nd 3+:glass laser system.

  20. Study of channel formation and relativistic ultra-short laser pulse propagation in helium plasma

    NASA Astrophysics Data System (ADS)

    Yu, Changhai; Tian, Ye; Li, Wentao; Zhang, Zhijun; Qi, Rong; Wang, Wentao; Wang, Cheng; Liu, Jiansheng

    2016-05-01

    In this study, plasma channel formation in pure He plasma (ionization electron density 0.01-0.1n c ) interacting with ultra-short relativistic laser pulses (50 fs, >1019 W cm-2) was observed and analyzed. By appropriately selecting the laser pulse and gas backing pressure of the gas jet, a clear density channel longer than 300 μm and wider than 25 μm was achieved in less than 1.5 ps following the passage of the laser pulse, with a radial electron density gradient of ~1023 cm-4 at the channel walls. Numerical simulations for studying the affects of the plasma density, kinetic motion of electrons and ions, and nonlinear laser propagation on the plasma channel formation were carried out, which reproduced the experimental features. These density channels were mainly driven by the radial expulsion of plasma ions, with strong continuous laser self-focusing acting to improve the channeling efficiency. These channels can guide the propagation of ultra-intense laser pulses and supply several advanced applications in high-energy physics, including fast-ignition inertial confinement fusion, plasma-based particle accelerations, and sources of radiation.

  1. Factorization of numbers with the temporal Talbot effect: optical implementation by a sequence of shaped ultrashort pulses.

    PubMed

    Bigourd, Damien; Chatel, Béatrice; Schleich, Wolfgang P; Girard, Bertrand

    2008-01-25

    We report on the successful operation of an analogue computer designed to factor numbers. Our device relies solely on the interference of classical light and brings together the field of ultrashort laser pulses with number theory. Indeed, the frequency component of the electric field corresponding to a sequence of appropriately shaped femtosecond pulses is determined by a Gauss sum which allows us to find the factors of a number. PMID:18232947

  2. Space-selective growth of frequency-conversion crystals in glasses with ultrashort infrared laser pulses.

    PubMed

    Miura, K; Qiu, J; Mitsuyu, T; Hirao, K

    2000-03-15

    We report on space-selective growth of a second-harmonic-generation beta-BaB(2)O(4) (BBO) crystal inside a BaO-Al(2)O(3)-B(2)O(3) glass sample at the focal point of an 800-nm femtosecond laser beam. A spherical heated region was formed during the focused laser irradiation through observation with an optical microscope. We moved the heated region by changing the position of the focal point of the laser beam relative to the glass sample. We grew BBO crystal continuously in the glass sample by adjusting the moving speed of the heated zone. Our results demonstrate that functional crystals can be formed three dimensionally in glasses by use of a nonresonant ultrashort pulsed laser. PMID:18059895

  3. D-shaped fiber grating refractive index sensor induced by an ultrashort pulse laser.

    PubMed

    Liao, Changrui; Wang, Qiao; Xu, Lei; Liu, Shen; He, Jun; Zhao, Jing; Li, Zhengyong; Wang, Yiping

    2016-03-01

    The fabrication of fiber Bragg gratings was here demonstrated using ultrashort pulse laser point-by-point inscription. This is a very convenient means of creating fiber Bragg gratings with different grating periods and works by changing the translation speed of the fiber. The laser energy was first optimized in order to improve the spectral properties of the fiber gratings. Then, fiber Bragg gratings were formed into D-shaped fibers for use as refractive index sensors. A nonlinear relationship was observed between the Bragg wavelength and liquid refractive index, and a sensitivity of ∼30  nm/RIU was observed at 1.450. This shows that D-shaped fiber Bragg gratings might be used to develop promising biochemical sensors. PMID:26974608

  4. Spectral phase encoding of ultra-short optical pulse in time domain for OCDMA application.

    PubMed

    Wang, Xu; Wada, Naoya

    2007-06-11

    We propose a novel reconfigurable time domain spectral phase encoding (SPE) scheme for coherent optical code-division-multiple-access application. In the proposed scheme, the ultra-short optical pulse is stretched by dispersive device and the SPE is done in time domain using high speed phase modulator. The time domain SPE scheme is robust to wavelength drift of the light source and is very flexible and compatible with the fiber optical system. Proof-of-principle experiments of encoding with 16-chip, 20 GHz/chip binary-phase-shift-keying codes and 1.25 Gbps data transmission have been successfully demonstrated together with an arrayed-wave-guide decoder. PMID:19547055

  5. Propagation of an ultrashort, intense laser pulse in a relativistic plasma

    SciTech Connect

    Ritchie, B.; Decker, C.D.

    1997-12-31

    A Maxwell-relativistic fluid model is developed for the propagation of an ultrashort, intense laser pulse through an underdense plasma. The separability of plasma and optical frequencies ({omega}{sub p} and {omega} respectively) for small {omega}{sub p}/{omega} is not assumed; thus the validity of multiple-scales theory (MST) can be tested. The theory is valid when {omega}{sub p}/{omega} is of order unity or for cases in which {omega}{sub p}/{omega} {much_lt} 1 but strongly relativistic motion causes higher-order plasma harmonics to be generated which overlap the region of the first-order laser harmonic, such that MST would not expected to be valid although its principal validity criterion {omega}{sub p}/{omega} {much_lt} 1 holds.

  6. Ultrashort microwave pulsed thermoacoustic imaging for tumor localization over whole breast

    NASA Astrophysics Data System (ADS)

    Ji, Zhong; Fu, Yong; Lou, Cunguang

    2014-09-01

    Microwave-induced thermoacoustic imaging (TAI) has attracted considerable interest as a promising imaging modality. Previous studies show that TAI has great potential for use in breast tumor detection with high contrast and high spatial resolution, nevertheless it requires high energy density and possesses small field of view (FOV). In this paper, a ultrashort microwave pulse (USMP) TAI system was employed for quality imaging with much less energy density required , and simultaneously, large enough FOV was obtained to cover the whole breast. The experimental results clearly demonstrate that the new USMP TAI system can be used for three-dimensional (3-D) localization of deep breast tumors with low microwave radiation dose over the whole breast.

  7. Dynamical alignment of H2^+ in an intense ultrashort laser pulse

    NASA Astrophysics Data System (ADS)

    Anis, Fatima; Cabrera-Trujillo, R.; Esry, B. D.

    2006-05-01

    We will present a study of ionization and dissociation of H2^+ in an intense ultrashort laser pulse. Our results include all degrees of freedom - classical for the nuclei and quantum mechanical for the electron. Similar previous calculations^1,2 have obtained the electronic wave function using a basis expansion. We, however, are solving the time-dependent Schr"odinger equation on a three dimensional grid in the lab frame. One of our goal is to study dynamical alignment of H2^+ and its fragments. We consider a distribution of initial nuclear positions and momenta so that our results are suitable for direct comparison with experiment. ^1M. Ullmann, T. Kunert, F. Grossmann, R. Schmidt, Phys. Rev. A 67, 013413 (2003). ^2E. Deumens, A. Diz, R. Longo, and Y. "Ohrn, Rev. Mod. Phys. 66, 917 (1994)

  8. Electronic and Structural Response of InSb to Ultra-short and Ultra-intense Laser Pulses

    NASA Astrophysics Data System (ADS)

    Burzo, Andrea; Allen, Roland

    2002-03-01

    The present work is motivated in part by the increasing interest in a better understanding of the optical properties of InSb, the main material used to manufacture infrared detectors. In addition, there have been recent experimental studies of the behavior of InSb following application of ultra-short and ultra-intense laser pulses. Motivated directly by these experiments, we have performed simulations of the electron-ion dynamics of InSb subjected to femtosecond-scale laser pulses. These simulations employ a tight-binding approximation, and the time-dependent Schroedinger equation is solved with an adapted Cayley algorithm which conserves probability. The atomic forces are obtained from a generalized Hellmann-Feynman theorem, which may be also interpreted as a generalized Ehrenfest theorem. We find that above a certain threshold intensity the lattice loses its tetrahedral structure and becomes disrupted. In addition, the band gap collapses and the material becomes metallic. Comparison of our simulations with experiments involving measurements of the imaginary part of the dielectric function shows good agreement in all important aspects. Further investigation of microscopic quantities, such as the atomic pair correlation function, the occupancies of excited states, and the displacement of atoms from their initial positions, strengthens our conclusion that the semiconductor exhibits a nonthermal phase transition as the intensity of the laser pulse is increased.

  9. Ultrashort pulsed laser tools for testing of semiconductor elements hardness to single event effects, caused by cosmic heavy charged particles

    NASA Astrophysics Data System (ADS)

    Gordienko, Alexandra V.; Mavritskii, Oleg B.; Egorov, Andrey N.; Pechenkin, Alexander A.; Savchenkov, Dmitriy V.

    2015-03-01

    The installations for laser testing of microelectronic elements (first of all - integrated circuits) of devices for space applications for hardness to local radiation effects from heavy charged particles are presented. The possibility of a focused pulsed laser radiation application to the study of local radiation effects, caused by single heavy charged particles, is explained. The fundamentals of an approach to the construction of test sets, based on the picosecond and femtosecond lasers and systems for focusing their radiation, are considered. The main technical requirements for the basic modules of sets for laser testing (laser wavelength and pulse duration and repetition rate, spatial beam parameters and minimal spot size, speed of object movement and so on) are substantiated. All worked out sets have a full-featured software for the operational management of all modules of the laser test facility, including the positioning of the object, to provide feedback from the measurement results of the reaction of the object on the laser excitation. The parameters of developed laser hardware and software systems and their foreign counterparts are compared. Further improvement directions for laser testing tools are briefly outlined. The discussion is also presented of described hardware technical and operational characteristics, allowing to use it for a variety of scientific research studies, requiring selective (with submicron spatial resolution) object excitation by ultrashort laser pulses and recording responses to this effect with the exact timing of the moment of excitation, as well as to perform a variety of high precision technological operations.

  10. Investigation on hot electron generation and propagation in interaction of ultrashort laser pulses with solids

    NASA Astrophysics Data System (ADS)

    Zhang, Jie

    2002-04-01

    Hot electron generation and propagation have been investigated in the interaction of ultrashort laser pulses with solid targets. The hot election generation and absorption mechanisms of ultrashort laser pulses have been studied at intensities of 5¡Á1016 7¡Á1017 Wcm-2 [1,2]. The competition between vacuum heating and resonance absorption has been found to be the main reason for a double-temperature distribution of hot electrons [3,4]. The effects of charge-separation-potential have been found to play a main role in the interaction process [5]. The effects of laser polarization on the hot electron emission have also been studied [6]. Outgoing hot electrons collimated in the polarization direction has been observed for the s-polarized laser irradiation, whereas for the p-polarized irradiation, very directional emission of outgoing hot electrons has been found close to the normal direction of the target. Dependence of the jet emission of hot electrons on the plasma scale-length has been obtained. The angular distribution has been found to be dependent on the energy of hot electrons. Particle-in-Cell (PIC) simulations have confirmed most of the observations [1,3,7]. The propagation process of hot electrons through solids have also been investigated [8]. References [1] Q.L. Dong, J. Zhang and H. Teng, Phys. Rev. E64, 026411 (2001). [2] L.M Chen, J.Zhang, et al., Phys. Plasmas 8, 2925 (2001). [3] Q.L. Dong, J. Zhang, Phys. Plasmas 8,1025 (2001). [4] H. Lin, et al., Phys. Plasmas 8,1707 (2001). [5] L.M. Chen, J. Zhang, et al., Phys. Rev. E63,036403 (2001). [6] L. M. Chen, J. Zhang, et al., Phys. Rev. Lett. 87, 225001 (2001). [7] Z.M. Sheng, et al., Phys. Rev. Lett. 85, 5340 (2000). [8] Y.T. Li, J. Zhang, et al., Phys. Rev. E64, 046407 (2001).

  11. Phonon-assisted nonlinear optical processes in ultrashort-pulse pumped optical parametric amplifiers

    NASA Astrophysics Data System (ADS)

    Isaienko, Oleksandr; Robel, István

    2016-03-01

    Optically active phonon modes in ferroelectrics such as potassium titanyl phosphate (KTP) and potassium titanyl arsenate (KTA) in the ~7–20 THz range play an important role in applications of these materials in Raman lasing and terahertz wave generation. Previous studies with picosecond pulse excitation demonstrated that the interaction of pump pulses with phonons can lead to efficient stimulated Raman scattering (SRS) accompanying optical parametric oscillation or amplification processes (OPO/OPA), and to efficient polariton-phonon scattering. In this work, we investigate the behavior of infrared OPAs employing KTP or KTA crystals when pumped with ~800-nm ultrashort pulses of duration comparable to the oscillation period of the optical phonons. We demonstrate that under conditions of coherent impulsive Raman excitation of the phonons, when the effective χ(2) nonlinearity cannot be considered instantaneous, the parametrically amplified waves (most notably, signal) undergo significant spectral modulations leading to an overall redshift of the OPA output. The pump intensity dependence of the redshifted OPA output, the temporal evolution of the parametric gain, as well as the pump spectral modulations suggest the presence of coupling between the nonlinear optical polarizations PNL of the impulsively excited phonons and those of parametrically amplified waves.

  12. Phonon-assisted nonlinear optical processes in ultrashort-pulse pumped optical parametric amplifiers

    PubMed Central

    Isaienko, Oleksandr; Robel, István

    2016-01-01

    Optically active phonon modes in ferroelectrics such as potassium titanyl phosphate (KTP) and potassium titanyl arsenate (KTA) in the ~7–20 THz range play an important role in applications of these materials in Raman lasing and terahertz wave generation. Previous studies with picosecond pulse excitation demonstrated that the interaction of pump pulses with phonons can lead to efficient stimulated Raman scattering (SRS) accompanying optical parametric oscillation or amplification processes (OPO/OPA), and to efficient polariton-phonon scattering. In this work, we investigate the behavior of infrared OPAs employing KTP or KTA crystals when pumped with ~800-nm ultrashort pulses of duration comparable to the oscillation period of the optical phonons. We demonstrate that under conditions of coherent impulsive Raman excitation of the phonons, when the effective χ(2) nonlinearity cannot be considered instantaneous, the parametrically amplified waves (most notably, signal) undergo significant spectral modulations leading to an overall redshift of the OPA output. The pump intensity dependence of the redshifted OPA output, the temporal evolution of the parametric gain, as well as the pump spectral modulations suggest the presence of coupling between the nonlinear optical polarizations PNL of the impulsively excited phonons and those of parametrically amplified waves. PMID:26975881

  13. Generation of UV light by intense ultrashort laser pulses in air

    NASA Astrophysics Data System (ADS)

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

    2004-11-01

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

  14. Phonon-assisted nonlinear optical processes in ultrashort-pulse pumped optical parametric amplifiers

    DOE PAGESBeta

    Isaienko, Oleksandr; Robel, Istvan

    2016-03-15

    Optically active phonon modes in ferroelectrics such as potassium titanyl phosphate (KTP) and potassium titanyl arsenate (KTA) in the ~7–20 THz range play an important role in applications of these materials in Raman lasing and terahertz wave generation. Previous studies with picosecond pulse excitation demonstrated that the interaction of pump pulses with phonons can lead to efficient stimulated Raman scattering (SRS) accompanying optical parametric oscillation or amplification processes (OPO/OPA), and to efficient polariton-phonon scattering. In this work, we investigate the behavior of infrared OPAs employing KTP or KTA crystals when pumped with ~800-nm ultrashort pulses of duration comparable to themore » oscillation period of the optical phonons. We demonstrate that under conditions of coherent impulsive Raman excitation of the phonons, when the effective χ(2) nonlinearity cannot be considered instantaneous, the parametrically amplified waves (most notably, signal) undergo significant spectral modulations leading to an overall redshift of the OPA output. Furthermore, the pump intensity dependence of the redshifted OPA output, the temporal evolution of the parametric gain, as well as the pump spectral modulations suggest the presence of coupling between the nonlinear optical polarizations PNL of the impulsively excited phonons and those of parametrically amplified waves.« less

  15. Targeted disruption of deep-lying neocortical microvessels in rat using ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Nishimura, Nozomi; Schaffer, Christopher B.; Friedman, Beth; Tsai, Philbert S.; Lyden, Patrick D.; Kleinfeld, David

    2004-06-01

    The study of neurovascular diseases such as vascular dementia and stroke require novel models of targeted vascular disruption in the brain. We describe a model of microvascular disruption in rat neocortex that uses ultrashort laser pulses to induce localized injury to specific targeted microvessels and uses two-photon microscopy to monitor and guide the photodisruption process. In our method, a train of high-intensity, 100-fs laser pulses is tightly focused into the lumen of a blood vessel within the upper 500 μm of cortex. Photodisruption induced by these laser pulses creates injury to a single vessel located at the focus of the laser, leaving the surrounding tissue intact. This photodisruption results in three modalities of localized vascular injury. At low power, blood plasma extravasation can be induced. The vessel itself remains intact, while serum is extravasated into the intercellular space. Localized ischemia caused by an intravascular clot results when the photodisruption leads to a brief disturbance of the vascular walls that initiates an endogenous clotting cascade. The formation of a localized thrombus stops the blood flow at the location of the photodisruption. A hemorrhage, defined as a large extravasation of blood including plasma and red blood cells, results when higher laser power is used. The targeted vessel does not remain intact.

  16. Two-photon double ionization of atomic beryllium with ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Yip, F. L.; Palacios, A.; Martín, F.; Rescigno, T. N.; McCurdy, C. W.

    2015-11-01

    We investigate the two-photon double ionization of beryllium atom induced by ultrashort pulses. We use a time-dependent formalism to evaluate the ionization amplitudes and generalized cross sections for the ejection of the 2 s2 valence shell electrons in the presence of a fully occupied 1 s2 frozen core shell. The relative contributions of the two-photon direct and sequential process are systematically explored by varying both pulse duration and central frequency. The energy and angular differential ionization yields reveal the signatures of both mechanisms, as well as the role of electron correlation in both the single and double ionization continua. In contrast with previous results on the helium atom, the presence of an electronic core strongly affects the final state leading to back-to-back electron emission even in the a priori less correlated two-photon sequential mechanism. In particular, a dominant pathway via excitation ionization through the Be+(2 p ) determines the profiles and pulse-duration dependencies of the energy and angle differential yields.

  17. Phonon-assisted nonlinear optical processes in ultrashort-pulse pumped optical parametric amplifiers.

    PubMed

    Isaienko, Oleksandr; Robel, István

    2016-01-01

    Optically active phonon modes in ferroelectrics such as potassium titanyl phosphate (KTP) and potassium titanyl arsenate (KTA) in the ~7-20 THz range play an important role in applications of these materials in Raman lasing and terahertz wave generation. Previous studies with picosecond pulse excitation demonstrated that the interaction of pump pulses with phonons can lead to efficient stimulated Raman scattering (SRS) accompanying optical parametric oscillation or amplification processes (OPO/OPA), and to efficient polariton-phonon scattering. In this work, we investigate the behavior of infrared OPAs employing KTP or KTA crystals when pumped with ~800-nm ultrashort pulses of duration comparable to the oscillation period of the optical phonons. We demonstrate that under conditions of coherent impulsive Raman excitation of the phonons, when the effective χ((2)) nonlinearity cannot be considered instantaneous, the parametrically amplified waves (most notably, signal) undergo significant spectral modulations leading to an overall redshift of the OPA output. The pump intensity dependence of the redshifted OPA output, the temporal evolution of the parametric gain, as well as the pump spectral modulations suggest the presence of coupling between the nonlinear optical polarizations P(NL) of the impulsively excited phonons and those of parametrically amplified waves. PMID:26975881

  18. Stimulated Raman scattering in hydrogen by ultrashort laser pulse in the keV regime

    NASA Astrophysics Data System (ADS)

    Bachau, H.; Dondera, M.

    2016-04-01

    This letter addresses the problem of stimulated Raman excitation of a hydrogen atom submitted to an ultrashort and intense laser pulse in the keV regime. The pulse central frequency ω of 55 a.u. (about 1.5 keV) is in the weakly relativistic regime, ω ≤ c/a0 (c is the speed of light in vacuum and a 0 the Bohr radius) and the pulse duration is τ ≈ 18.85 a.u. (about 456 attoseconds). We solve the corresponding time-dependent Schrödinger equation (TDSE) using a spectral approach, retardation (or nondipole) effects are included up to O(1/c) , breaking the conservation of the magnetic quantum number m and forcing the resolution of the TDSE in a three-dimensional space. Due to the laser bandwidth, which is of the order of the ionization potential of hydrogen, stimulated Raman scattering populates nlm excited states (n and l are the principal and azimuthal quantum numbers, respectively). The populations of these excited states are calculated and analyzed in terms of l and m quantum numbers, this showing the contributions of the retardation effects and their relative importance.

  19. Influence of EL2 deep level on photoconduction of semi-insulating GaAs under ultrashort pulse photoinjection

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Xie, Guangyong

    2016-02-01

    To investigate the influence of EL2 deep level on photoconduction of in semi-insulating GaAs (SI-GaAs), a 3 mm-electrode-gap lateral SI-GaAs photoconductive chip was manufactured and tested by using ultrashort pulse laser with 1064 nm wavelength, 10 ns pulsewidth, 3.0 mm light spot diameter and single pulse energy mean of 3.0 mJ. Based on the experimental results and the theory of trapping effect, the photon absorption process of EL2 defects in SI-GaAs is analyzed. For the influence of EL2 deep level, the lifetime of the electron gets shorter and the persistent photoconductivity (PPC) is significant. With increasing of voltage, the decay time constant of photoconduction is reduced and the decay index gets bigger for the ultrashort pulse photoinjection.

  20. Material processing with ultra-short pulse lasers working in 2μm wavelength range

    NASA Astrophysics Data System (ADS)

    Voisiat, B.; Gaponov, D.; Gečys, P.; Lavoute, L.; Silva, M.; Hideur, A.; Ducros, N.; Račiukaitis, G.

    2015-03-01

    New wavelengths of laser radiation are of interest for material processing. Results of application of the all-fiber ultrashort pulsed laser emitting in 2 µm range, manufactured by Novae, are presented. Average output power was 4.35 W in a single-spatial-mode beam centered at the 1950 nm wavelength. Pulses duration was 40 ps, and laser operated at 4.2 MHz pulse repetition rate. This performance corresponded to 25 kW of pulse peak power and almost 1 µJ in pulse energy. Material processing was performed using three different focusing lenses (100, 30 and 18 mm) and mechanical stages for the workpiece translation. 2 µm laser radiation is strongly absorbed by some polymers. Swelling of PMMA surface was observed for scanning speed above 5 mm/s using the average power of 3.45 W focused with the 30 mm lens. When scanning speed was reduced below 4 mm/s, ablation of PMMA took place. The swelling of PMMA is a consequence of its melting due to absorbed laser power. Therefore, experiments on butt welding of PMMA and overlapping welding of PMMA with other polymers were performed. Stable joint was achieved for the butt welding of two PMMA blocks with thickness of 5 mm. The laser was used to cut a Kapton film on a paper carrier with the same set-up as previous. The cut width depended on the cutting speed and focusing optics. A perfect cut with a width of 11 µm was achieved at the translation speed of 60 mm/s.

  1. Non-Fourier two-temperature heat conduction model used to analyze ultrashort-pulse laser processing of nanoscale metal film.

    PubMed

    Ho, Ching-Yen; Wen, Mao-Yu; Chen, Bor-Chyuan; Tsai, Yu-Hsiang

    2014-07-01

    This paper utilizes non-Fourier two-temperature heat conduction model to investigate the temperature field in nanometer-sized thin films irradiated by an ultrashort-pulse laser. Ultrashort-pulse laser processing for nanometer-sized devices is usually applied in MEMS and nanotechnology. For ultrashort-pulse laser interaction with metals, the two-temperature model was proposed to describe the heat transport in metals due to a substantial nonequilibrium between the electron and lattice temperature. For heat conduction in nanoscale devices, Fourier law is inadequate for describing the heat conduction in nanoscale due to the boundary scattering and the finite relaxation time of heat carriers. Therefore, in this work, the Non-Fourier two-temperature heat conduction model used to analyze ultrashort-pulse laser processing of nanoscale metal film. The result obtained from non-Fourier heat conduction equations is compared with the available experimental data. The parametric effects are also discussed. PMID:24758069

  2. Ion heating dynamics in solid buried layer targets irradiated by ultra-short intense laser pulses

    SciTech Connect

    Huang, L. G.; Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden; University of Chinese Academy of Sciences, 100049 Beijing ; Bussmann, M.; Kluge, T.; Lei, A. L.; Yu, W.; Cowan, T. E.; Technische Universität Dresden, 01062 Dresden

    2013-09-15

    We investigate bulk ion heating in solid buried layer targets irradiated by ultra-short laser pulses of relativistic intensities using particle-in-cell simulations. Our study focuses on a CD{sub 2}-Al-CD{sub 2} sandwich target geometry. We find enhanced deuteron ion heating in a layer compressed by the expanding aluminium layer. A pressure gradient created at the Al-CD{sub 2} interface pushes this layer of deuteron ions towards the outer regions of the target. During its passage through the target, deuteron ions are constantly injected into this layer. Our simulations suggest that the directed collective outward motion of the layer is converted into thermal motion inside the layer, leading to deuteron temperatures higher than those found in the rest of the target. This enhanced heating can already be observed at laser pulse durations as low as 100 fs. Thus, detailed experimental surveys at repetition rates of several ten laser shots per minute are in reach at current high-power laser systems, which would allow for probing and optimizing the heating dynamics.

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

    PubMed

    Miyamoto, Isamu; Cvecek, Kristian; Schmidt, Michael

    2013-06-17

    The spatial distribution of the laser energy absorbed by nonlinear absorption process in bulk glass w(z) is determined and thermal cycles due to the successive ultrashort laser pulse (USLP) is simulated using w(z) based on the transient thermal conduction model. The thermal stress produced in internal melting of bulk glass by USLP is qualitatively analyzed based on a simple thermal stress model, and crack-free conditions are studied in glass having large coefficient of thermal expansion. In heating process, cracks are prevented when the laser pulse impinges into glass with temperatures higher than the softening temperature of glass. In cooling process, shrinkage stress is suppressed to prevent cracks, because the embedded molten pool produced by nonlinear absorption process behaves like an elastic body under the compressive stress field unlike the case of CW-laser welding where the molten pool having a free surface produced by linear absorption process is plastically deformed under the compressive stress field. PMID:23787618

  4. Transmembrane voltage analyses in spheroidal cells in response to an intense ultrashort electrical pulse

    NASA Astrophysics Data System (ADS)

    Hu, Q.; Joshi, R. P.

    2009-01-01

    Self-consistent evaluations of both the transmembrane potential (TMP) and possible electroporation density across membrane of spheroidal cells in response to ultrashort, high-intensity pulses are reported and discussed. Most treatments in the literature have been based on spherical cells, and this represents a step towards more realistic analyses. The present study couples the Laplace equation with Smoluchowski theory of pore formation, to yield dynamic membrane conductivities that influence the TMP. It is shown that the TMP induced by pulsed external voltages can be substantial higher in oblate spheroids as compared to spherical or prolate spheroidal cells. Flattening of the surface area in oblate spheroids leads to both higher electric fields seen by the membrane, and allows a great fraction of the surface area to be porated. This suggests that biomedical applications such as drug delivery and electrochemotherapy could work best for flatter-shaped cells, and secondary field-enabled orienting would be beneficial. Results for arbitrary field orientations and different cell sizes have also been presented.

  5. Manipulating mammalian cell by phase transformed titanium surface fabricated through ultra-short pulsed laser synthesis.

    PubMed

    Chinnakkannu Vijayakumar, Sivaprasad; Venkatakrishnan, Krishnan; Tan, Bo

    2016-01-15

    Developing cell sensitive indicators on interacting substrates that allows specific cell manipulation by a combination of physical, chemical or mechanical cues is a challenge for current biomaterials. Hence, various fabrication approaches have been created on a variety of substrates to mimic or create cell specific cues. However, to achieve cell specific cues a multistep process or a post-chemical treatment is often necessitated. So, a simple approach without any chemical or biological treatment would go a long way in developing bio-functionalized substrates to effectively modulate cell adhesion and interaction. The present investigation is aimed to study the manipulative activity induced by phase transformed titanium surface. An ultra-short laser is used to fabricate the phase transformed titanium surface where a polymorphic titanium oxide phases with titanium monoxide (TiO), tri-titanium oxide (Ti3O) and titanium dioxide (TiO2) have been synthesized on commercially pure titanium. Control over oxide phase transformed area was demonstrated via a combination of laser scanning time (laser pulse interaction time) and laser pulse widths (laser pulse to pulse separation time). The interaction of phase transformed titanium surface with NIH3T3 fibroblasts and MC3T3-E1 osteoblast cells developed a new bio-functionalized platforms on titanium based biomaterials to modulate cell migration and adhesion. The synthesized phase transformed titanium surface on the whole appeared to induce directional cues for cell migration with unique preferential cell adhesion unseen by other fabrication approaches. The precise bio-functionalization controllability exhibited during fabrication offers perceptible edge for developing a variety of smart bio-medical devices, implants and cardiovascular stents where the need in supressing specific cell adhesion and proliferation is of great demand. PMID:26546983

  6. Generation of low-frequency nonlinear currents in plasma by an ultrashort pulse of high-frequency radiation

    SciTech Connect

    Grishkov, V. E.; Uryupin, S. A.

    2015-07-15

    A kinetic theory of low-frequency currents induced in plasma by an ultrashort high-frequency radiation pulse is developed. General expressions for the currents flowing along the propagation direction of the pulse and along the gradient of the field energy density are analyzed both analytically and numerically for pulse durations longer or shorter than or comparable with the electron collision time in plasma. It is demonstrated that the nonlinear current flowing along the gradient of the field energy density can be described correctly only when the modification of the isotropic part of the electron distribution function is taken into account.

  7. Propagation of the Ultra-Short Laser Pulses Through the Helical 1D Photonic Crystal Structure with Twist Defect

    NASA Astrophysics Data System (ADS)

    Antonov, Dmitrii V.; Iegorov, Roman

    2016-02-01

    The presence of the photonic band-gap is a featured property of the cholesteric liquid crystals (CLC). It can be practically realized for almost any reasonable wavelengths with very high degree of tunability. We have investigated theoretically the influence of the twist defect of the CLC helical structure onto the bandwidth-limited ultra-short laser pulse propagating inside the photonic band-gap. The changes of both pulse duration and peak power with defect angle were observed together with pulse acceleration and retardation for a case of normal incidence of the light.

  8. Application of the Monte Carlo method for modeling passage of ultrashort laser pulses through an inhomogeneous medium with moving scatterers

    NASA Astrophysics Data System (ADS)

    Starukhin, P. Yu.; Klinaev, Yu. V.

    2011-05-01

    We present the results of numerical modeling of passage of ultrashort laser pulses through an inhomogeneous layered medium with moving scatterers, based on solution of the nonsteady-state radiation transport equation by the Monte Carlo method. We consider the effects of Doppler broadening of the backscattered radiation spectrum in biological tissues. We have analyzed the dynamics of propagation of a short laser pulse within a multilayer model of human skin. We have studied the possibilities for tomography of different layers of biological tissue based on analysis of the spectrum of the scattered radiation pulse.

  9. 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. PMID:22565342

  10. Ultrashort optical pulse generation from a chromium(4)- doped yttrium aluminium garnet tunable solid-state laser

    NASA Astrophysics Data System (ADS)

    Chang, Yongmao

    2000-11-01

    In this thesis, experimental results of ultrashort pulse generation from Cr4+-doped yttrium aluminium garnet (YAG) laser system are presented. The Cr4+:YAG crystal is a vibronically broadened solid state laser gain medium, which lases at room temperature from 1.34 to 1.58 μm and can be pumped by a Nd:YAG laser at 1.06 μm. Ultrashort pulses from this coherent light source are potentially important in technology applications such as ultrafast fiber-optic communications and time-resolved spectroscopy of narrow- bandgap, semiconductors. It is a practical alternative to more conventional cryogenic colour center lasers at this wavelength such as NaCl:OH- or complex optical parametric oscillators synchronously pumped by a Ti:sapphire laser. The cw power performance of a Cr4+:YAG laser was characterized and several unique properties were identified. A broad tuning range of 210 nm, i.e., from 1345 to 1557 nm, was demonstrated by means of one set of mirrors with useful cw output power of as high as 730 mW at 1.46 μm (with a Nd:YAG pump power of 6.5 W). The lasing action was found to be strongly influenced by the temperature of the crystal and the combined effects of thermal lensing and saturable absorption of the pump beam. The excited-state absorption (ESA) at the pump and lasing wavelengths were investigated both experimentally and theoretically. ESA at the lasing wavelength occurs for the transition from the state 3B2(3T2) to 3E(3T1(F)), while the pump ESA comes from the transition from 3A2(3T2 ) to 3E(3T1(P)). The emission ESA cross sections for the free-running modes were estimated from the laser efficiency data by taking into account the pump and cavity parameters. Ultrashort pulse generation with a Cr4+:YAG laser was investigated using passive mode-locking with a semiconductor quantum well saturable absorber. Self-starting of the laser system was demonstrated using a strained GaInAs/InAlAs saturable Bragg reflector (SBR) with a single prism for dispersion

  11. Threshold radiant exposure for cell death in the endothelium of porcine cornea exposed to ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Hussain, S. A.; Kowalczuk, L.; Crotti, C.; Alahyane, F.; Plamann, K.

    2013-06-01

    We have determined the threshold radiant exposure for cell death in the endothelium of porcine cornea exposed to ultrashort laser pulses in the context of keratoplasty and the preparation of endothelial grafts. In this study, by progressively increasing the radiant threshold towards the higher values we have observed a decrease of living corneal endothelial cells. Further study will address the effect of dose and possible mechanism behind cell death.

  12. MEASURED PROPERTIES OF THE DUVFEL HIGH BRIGHTNESS, ULTRASHORT ELECTRON BEAM.

    SciTech Connect

    GRAVES, W.S.; CARR, G.L.; DIMAURO, L.F.; DOYURAN, A.; HEESE, R.; JOHNSON, E.D.; KRINSKY, S.; NEUMAN, C.; RAKOWSKY, G.; ROSE, J.; ROTHMAN, J.; RUDATI, J.; SHAFTAN, T.; SHEEHY, B.; SKARITKA, J.; YU, L.H.; DOWELL, D.H.; EMMA, P.

    2001-06-18

    The DUVFEL electron linac is designed to produce sub-picosecond, high brightness electron bunches to drive an ultraviolet FEL. The accelerator consists of a 1.6 cell S-band photoinjector, variable pulse length Ti:Sapp laser, 4 SLAC-type S-band accelerating sections, and 4-dipole chicane bunch compressor. In preparation for FEL operation, the compressed electron beam has been fully characterized. Measurement of the beam parameters and simulation of the beam are presented.

  13. Generation of ultrashort pulses of electrons, X-rays and optical pulses by relativistically strong light

    SciTech Connect

    Umstadter, D.; Banerjee, S.; Chen, S.; Sepke, S.; Maksimchuk, A.; Valenzuela, A.; Rousse, A.; Shah, R.; Phuoc, K. Ta

    2006-04-07

    We report recent results of experiments in which relativistic optical effects play an important role, at peak laser intensities above 1019 W/cm2. These effects are leading to novel radiation sources, all with femtosecond pulse durations: (1) the generation of optical photons by means of pulse compression via relativistic cross-phase modulation, (2) ponderomotive deflection of laser accelerated electron beams, and (3) the generation of well-collimated keV-energy x-ray beams by means of either Thomson scattering or betatron oscillations in ion channels.

  14. Two-photon double ionization of atomic beryllium by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Yip, Frank L.; Palacios, Alicia; Martin, Fernando; Rescigno, Thomas N.; McCurdy, C. William

    2014-05-01

    A time-dependent formalism for evaluating ionization amplitudes and generalized cross sections for two-electron atoms previously used to study the correlated electron dynamics of helium under ultrashort laser pulses is adapted to study similar processes involving the 2s2 valence shell of atomic beryllium in the presence of a fully-occupied 1s2 core shell. The similar symmetry of the overall process in two-photon double ionization permits a direct comparison between Be and He atoms, revealing details about the nature of electron correlation within these two atoms whose impact is manifest in the continuum electron dynamics. In particular, consequences of the different shell structures of the initial states for He and Be are prominent when considering sequential double ionization processes. Work supported by the US Dept. of Energy, Office of Basic Energy Sciences, Chemical Sciences Contract DE-AC02-05CH11231, by the MICINN Projects No. FIS2010-15127 and ERC Advanced Grant 290853.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  16. Exploring polygon scanner head capabilities for ultra-short pulse laser texturing

    NASA Astrophysics Data System (ADS)

    Mincuzzi, G.; Fleureau, M.; Faucon, M.; Kling, R.

    2016-03-01

    The combination of both, fast beam scanning systems and high repetition rate, high average power lasers, represents an interesting technological solution for surface texturing by Ultra-Short Pulses Laser to gain a foothold into industrial environment for commercial purposes. Nevertheless unwanted thermal effects are expected when the average power exceeds some tens of W. An interesting strategy for a reliable heat management would consists of texturing surfaces with a low fluence values (slightly higher than the ablation threshold) and utilising a polygon scanning head which is able to deflect the laser beam with unprecedented speed. Here we show that over stainless steel, it is possible to obtain different surface textures (in particular ripples, micro grooves and spikes) by utilising a 2 MHz femtosecond laser jointly with a fast and accurate polygonal scanner head at relatively low fluence (0.11 J·cm-2). The evolution of the Laser induced surface structures morphology is shown when varying the scan speed between 25 m·s-1 and 90 m·s-1. Two different wavelengths have been utilised for the process λ= 1030 nm and λ = 515 nm and the difference of the results obtained have been highlighted. Moreover, a full structures morphology characterization by SEM has been carried out for all the textured surfaces. Finally, by increasing the number of successive surface scans is possible to tailor the surface reflectivity. As a result an average reflectivity value of < 5% over the visible range has been extracted from a blackened stainless steel surface.

  17. Experimental study on the development of a micro-drilling cycle using ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Romoli, L.; Vallini, R.

    2016-03-01

    Microholes for the production of high precision devices were obtained by ultrashort pulsed laser machining of martensitic stainless steels. A micro-drilling cycle based on the sequence of a drilling through phase, an enlargement and finishing phase is proposed in order to solve the trade-off between process time and quality of the ablated surfaces without making use of complex design of experiments. The three phases were studied taking into account the evolution of the microhole shape as a function of the main process parameters (number of passes per phase, incidence angle and radius of the beam trajectory respect to the hole's axis). Experiments testified that the drilling strategy was able to produce cylindrical holes with diameter of 180±2 μm on a 350 μm thick plate in total absence of burrs and debris within a drilling time of 3.75 s. Repeatability tests showed a process capability of nearly 99%. SEM inspection of the inner surface of the microholes showed the presence of elongated and periodic ripples whose size and inclination can be controlled adjusting the incidence angle of the beam over the tapered surface before the ultimate finishing phase.

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

    PubMed

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

    2015-05-01

    There is an urgent need for rapid methods to develop vaccines in response to emerging viral pathogens. Whole inactivated virus (WIV) vaccines represent an ideal strategy for this purpose; however, a universal method for producing safe and immunogenic inactivated vaccines is lacking. Conventional pathogen inactivation methods such as formalin, heat, ultraviolet light, and gamma rays cause structural alterations in vaccines that lead to reduced neutralizing antibody specificity, and in some cases, disastrous T helper type 2-mediated immune pathology. We have evaluated the potential of a visible ultrashort pulsed (USP) laser method to generate safe and immunogenic WIV vaccines without adjuvants. Specifically, we demonstrate that vaccination of mice with laser-inactivated H1N1 influenza virus at about a 10-fold lower dose than that required using conventional formalin-inactivated influenza vaccines results in protection against lethal H1N1 challenge in mice. The virus, inactivated by the USP laser irradiation, has been shown to retain its surface protein structure through hemagglutination assay. Unlike conventional inactivation methods, laser treatment did not generate carbonyl groups in protein, thereby reducing the risk of adverse vaccine-elicited T helper type 2 responses. Therefore, USP laser treatment is an attractive potential strategy to generate WIV vaccines with greater potency and safety than vaccines produced by current inactivation techniques. PMID:25423046

  19. Optical reprogramming of human somatic cells using ultrashort Bessel-shaped near-infrared femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    We report a virus-free optical approach to human cell reprogramming into induced pluripotent stem cells with low-power nanoporation using ultrashort Bessel-shaped laser pulses. Picojoule near-infrared sub-20 fs laser pulses at a high 85 MHz repetition frequency are employed to generate transient nanopores in the membrane of dermal fibroblasts for the introduction of four transcription factors to induce the reprogramming process. In contrast to conventional approaches which utilize retro- or lentiviruses to deliver genes or transcription factors into the host genome, the laser method is virus-free; hence, the risk of virus-induced cancer generation limiting clinical application is avoided.

  20. Two-dimensional angular energy spectrum of electrons accelerated by the ultra-short relativistic laser pulse

    SciTech Connect

    Borovskiy, A. V.; Galkin, A. L.; Kalashnikov, M. P.

    2015-04-15

    The new method of calculating energy spectra of accelerated electrons, based on the parameterization by their initial coordinates, is proposed. The energy spectra of electrons accelerated by Gaussian ultra-short relativistic laser pulse at a selected angle to the axis of the optical system focusing the laser pulse in a low density gas are theoretically calculated. The two-peak structure of the electron energy spectrum is obtained. Discussed are the reasons for its appearance as well as an applicability of other models of the laser field.

  1. Theoretical analysis of hard x-ray generation by nonperturbative interaction of ultrashort light pulses with a metal

    PubMed Central

    Weisshaupt, Jannick; Juvé, Vincent; Holtz, Marcel; Woerner, Michael; Elsaesser, Thomas

    2015-01-01

    The interaction of intense femtosecond pulses with metals allows for generating ultrashort hard x-rays. In contrast to plasma theories, tunneling from the target into vacuum is introduced as electron generation step, followed by vacuum acceleration in the laser field and re-entrance into the target to generate characteristic x-rays and Bremsstrahlung. For negligible space charge in vacuum, the Kα flux is proportional to the incident intensity and the wavelength squared, suggesting a strong enhancement of the x-ray flux by mid-infrared driving pulses. This prediction is in quantitative agreement with experiments on femtosecond Cu Kα generation. PMID:26798790

  2. Optical reprogramming of human somatic cells using ultrashort Bessel-shaped near-infrared femtosecond laser pulses.

    PubMed

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

    2015-11-01

    We report a virus-free optical approach to human cell reprogramming into induced pluripotent stem cells with low-power nanoporation using ultrashort Bessel-shaped laser pulses. Picojoule near-infrared sub-20 fs laser pulses at a high 85 MHz repetition frequency are employed to generate transient nanopores in the membrane of dermal fibroblasts for the introduction of four transcription factors to induce the reprogramming process. In contrast to conventional approaches which utilize retro- or lentiviruses to deliver genes or transcription factors into the host genome, the laser method is virus-free; hence, the risk of virus-induced cancer generation limiting clinical application is avoided. PMID:26618522

  3. Transmission of 1064 nm laser radiation during ablation with an ultra-short pulse laser (USPL) system

    NASA Astrophysics Data System (ADS)

    Schelle, Florian; Meister, Jörg; Oehme, Bernd; Frentzen, Matthias

    2012-01-01

    During ablation of oral hard tissue with an USPL system a small amount of the incident laser power does not contribute to the ablation process and is being transmitted. Partial transmission of ultra-short laser pulses could potentially affect the dental pulp. The aim of this study was to assess the transmission during ablation and to deduce possible risks for the patient. The study was performed with an Nd:YVO4 laser, emitting pulses with a duration of 8 ps at a wavelength of 1064 nm. A repetition rate of 500 kHz and an average power of 9 W were chosen to achieve high ablation efficiency. A scanner system created square cavities with an edge length of 1 mm. Transmission during ablation of mammoth ivory and dentin slices with a thickness of 2 mm and 5 mm was measured with a power meter, placed directly beyond the samples. Effects on subjacent blood were observed by ablating specimens placed in contact to pork blood. In a separate measurement the temperature increase during ablation was monitored using an infrared camera. The influence of transmission was assessed by tuning down the laser to the corresponding power and then directly irradiating the blood. Transmission during ablation of 2 mm specimens was about 7.7% (ivory) and 9.6% (dentin) of the incident laser power. Ablation of specimens directly in contact to blood caused coagulation at longer irradiation times (t~18s). Direct irradiation of blood with the transmitted power provoked bubbling and smoke formation. Temperature measurements identified heat generation as the main reason for the observed coagulation.

  4. Measured Properties of the DUVFEL High Brightness, Ultrashort Electron Beam

    SciTech Connect

    Emma, Paul J

    2002-08-20

    The DUVFEL electron linac is designed to produce sub-picosecond, high brightness electron bunches to drive an ultraviolet FEL. The accelerator consists of a 1.6 cell S-band photoinjector, variable pulse length Ti:Sapp laser, 4 SLAC-type S-band accelerating sections, and 4-dipole chicane bunch compressor. In preparation for FEL operation, the compressed electron beam has been fully characterized. Measurement of the beam parameters and simulation of the beam are presented. The properties of the laser and photoinjector are summarized in Table 1. In typical running, 10 mJ of IR light is produced by the Spectraphyics Tsunami Ti:Sapphire oscillator and TSA50 amplifier, which is frequency tripled to produce 450 uJ of UV light. After spatial filtering and aperturing of the gaussian mode to produce a nearly uniform laser spot, about 200-300 uJ is delivered to the cathode. This produces 300 pC of charge at the accelerating phase of 30 degrees. The RF cavity is a Gun IV [1] with copper cathode that has been modified for better performance [2]. In principle, the laser pulse length may be adjusted from 100 fs to 10 ps, however there are practical limitations on the range of adjustment due to dispersion characteristics and efficiency of the BBO crystals. The thickness of the harmonic crystals is optimized for pulse lengths from 1-5 ps. Within this range of pulse lengths there is evidence [3] of variations in the time profile of the UV light that are sensitive to the phase-matching angle of the crystal.

  5. Pulse-width-dependent surface ablation of copper and silver by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Zayarny, Dmitry A.; Ionin, Andrey A.; Kudryashov, Sergey I.; Makarov, Sergey V.; Kuchmizhak, Alexander A.; Vitrik, Oleg B.; Kulchin, Yury N.

    2016-07-01

    The single-shot spallation thresholds for copper and silver surfaces demonstrate a considerable IR-laser (1030 nm) pulse-width dependent increase over a range of 0.2–12 ps for the former material and a very weak increase for the latter one, while the corresponding thresholds for visible (515 nm) laser pulses remain almost constant. The IR-laser increase of the ablation thresholds is related to two-photon interband (d–s) absorption in copper, contrasting with the linear absorption of visible laser pulses in this material. In silver, common weakly sublinear dependences on the laser pulsewidth were observed, ruling out possible multi-photon—either three(four)-photon in IR, or two-photon in the visible range—interband transitions in this material. Moreover, electron-lattice thermalization times of 1–2 ps were evaluated for these materials in the spallative ablation regime, contrasting strongly with the previously theoretically predicted multi-picosecond thermalization times.

  6. Controlling magnetism by ultrashort laser pulses: from fundamentals to nanoscale engineering

    NASA Astrophysics Data System (ADS)

    Bossini, D.; Rasing, Th.

    2016-06-01

    From the discovery of sub-picosecond demagnetization over a decade ago [1] to the recent demonstration of magnetization reversal by a single 40 femtosecond laser pulse [2], the manipulation of spins by ultra-short laser pulses has become a fundamentally challenging topic with a potentially high impact for future spintronics, data storage and manipulation and quantum computation [3]. It was realized that the femtosecond laser induced all-optical switching (AOS) as observed in ferrimagnets exploits the laser induced strongly non-equilibrium dynamics and the antiferromagnetic exchange interaction between their sublattices [4-6]. This opens the way to engineer new magnetic materials for AOS [7,8], though for real applications nanoscale control of inhomogeneities appears to be relevant [9]. Besides the intruiging technological implications of these observations, they broadened remarkably the frontiers of our fundamental knowledge of magnetic phenomena. The laser driven out-of-equilibrium states cannot be described in term of the well-established thermodynamical approach, which is based on the concepts of equilibrium and adiabatic transformations. Theoretical efforts, although in their infancy, have already demonstrated [5,6] that light-induced spin dynamics on the (sub)-picosecond time scale results in phenomena utterly forbidden in a thermodynamical framework. Another challenge is how to bring the optical manipulation of magnetic media to the required nanoscale. This is clearly a key element for the perspectives in terms of magnetic recording. In addition, it would allow to explore a novel regime of spin dynamics, since the investigation of magnets on the femtosecond time-scale and the nanometer length-scale simultaneously is unexplored. One experimental approach which may be successful makes use of wave-shaping techniques [10]. Recent results with engineered hybrid magnetic materials and nanofocusing via a plasmonic antenna showed the practical potential of AOS: the

  7. Behavior Of A Simple Metal Under Ultrashort Pulse High Intensity Laser Illumination

    NASA Astrophysics Data System (ADS)

    Milchberg, H. M.; Freeman, R. R.; Davey, S. C.

    1988-07-01

    We have observed the self-reflection of intense, sub-picosecond 308 nm light pulse incident on a planar AI target and have inferred the electrical conductivity of solid density AI. The pulse lengths were sufficiently short that no significant expansion of the target occurred during the measurement.

  8. All-polarization-maintaining Er-doped ultrashort-pulse fiber laser using carbon nanotube saturable absorber.

    PubMed

    Nishizawa, N; Seno, Y; Sumimura, K; Sakakibara, Y; Itoga, E; Kataura, H; Itoh, K

    2008-06-23

    We present an all-polarization-maintaining Er-doped ultrashort-pulse fiber laser using a single-wall carbon nanotube polyimide nanocomposite saturable absorber. The maximum average power for single-pulse operation is 4.8 mW, and the repetition frequency is 41.3 MHz. Self-start and stable mode-locking operation is achieved. The RF amplitude noise is also examined and it is confirmed that the noise figure is as low as that of a solid-state laser. Using a polarization-maintaining anomalous dispersive fiber, a 314 fs output pulse is compressed to 107 fs via higher-order soliton compression. The peak power of the compressed pulse is up to 1.1 kW. PMID:18575508

  9. Optical and electrical properties of SnO2 thin films after ultra-short pulsed laser annealing

    NASA Astrophysics Data System (ADS)

    Scorticati, D.; Illiberi, A.; Römer, G. R. B. E.; Bor, T.; Ogieglo, W.; Klein Gunnewiek, M.; Lenkferink, A.; Otto, C.; Skolski, J. Z. P.; Grob, F.; de Lange, D. F.; Huis in't Veld, A. J.

    2013-09-01

    Ultra-short pulsed laser sources, with pulse durations in the ps and fs regime, are commonly exploited for cold ablation. However, operating ultra-short pulsed laser sources at fluence levels well below the ablation threshold allows for fast and selective thermal processing. The latter is especially advantageous for the processing of thin films. A precise control of the heat affected zone, as small as tens of nanometers, depending on the material and laser conditions, can be achieved. It enables the treatment of the upper section of thin films with negligible effects on the bulk of the film and no thermal damage of sensitive substrates below. By applying picosecond laser pulses, the optical and electrical properties of 900 nm thick SnO2 films, grown by an industrial CVD process on borofloat®-glass, were modified. The treated films showed a higher transmittance of light in the visible and near infra-red range, as well as a slightly increased electrical sheet resistance. Changes in optical properties are attributed to thermal annealing, as well as to the occurrence of Laser- Induced Periodic Surface Structures (LIPSSs) superimposed on the surface of the SnO2 film. The small increase of electrical resistance is attributed to the generation of laser induced defects introduced during the fast heating-quenching cycle of the film. These results can be used to further improve the performance of SnO2-based electrodes for solar cells and/or electronic devices.

  10. Impact of atmospheric molecular absorption on the temporal and spatial evolution of ultra-short optical pulses.

    PubMed

    Gebhardt, Martin; Gaida, Christian; Stutzki, Fabian; Hädrich, Steffen; Jauregui, Cesar; Limpert, Jens; Tünnermann, Andreas

    2015-06-01

    We present a rigorous study on the impact of atmospheric molecular absorption on the linear propagation of ultrashort pulses in the mid-infrared wavelength region. An ultrafast thulium-based fiber laser was employed to experimentally investigate ultrashort-pulse propagation through the atmosphere in a spectral region containing several strong molecular absorption lines. The atmospheric absorption profile causes a significant degradation of the pulse quality in the time domain as well as a distortion of the transverse beam profile in the spatial domain. Numerical simulations carried out in the small signal limit accurately reproduce the experimental observations in the time domain and reveal that the relative loss in peak power after propagation can be more than twice as high as the relative amount of absorbed average power. Although their nature is purely linear (i.e. the intensities considered are sufficiently low) the discussed effects represent significant challenges to performance-scaling of mid-infrared ultrafast lasers operating in spectral regions with molecular absorption bands. Guidelines for an efficient mitigation of the pulse quality degradation and the beam profile distortion are discussed. PMID:26072749

  11. Study of the plasma expansion produced on ultra-thin foil targets with a high intensity and ultrashort laser pulse

    NASA Astrophysics Data System (ADS)

    Gnedyuk, Semen; Fourmaux, Sylvain; Buffechoux, Sebastien; Albertazzi, Bruno; Martin, Francois; Kieffer, Jean Claude

    2011-10-01

    INRS-EMT, Université du Québec, 1650 Lionel Boulet, Varennes J3X 1S2, Québec, Canada LULI, UMR 7605, CNRS - CEA - Université Paris 6 - Ecole Polytechnique, Palaiseau, France Abstract: A high intensity ultrashort laser pulse, with an intensity of the order of 1019 W/cm2, focused onto a thin foil target generates a plasma and highly energetic ion (including proton) beams from its front and rear sides which propagate along the target normal. Another interest of laser plasma interaction with ultra-thin foil is the possibility to deposit energy in the entire laser absorption depth before any expansion thus enabling target isochoric heating. With a target thickness of 30 or 15 nm the laser pulse should interact in volume and enable to reach very high temperature while the target is still at solid density. The resulting cooling of the target will then be ultra-fast and potential X-ray emission should be ultrashort. The 100 TW class laser system at the Advanced Laser Light Source facility enables laser plasma interaction study with femtosecond laser pulses, ultra thin foil targets and high contrast laser pulse intensity ratio. We used a shadowgraph diagnostic with a femtosecond laser probe to characterize the plasma expansion.

  12. Applications of parametric processes to high-quality multicolour ultrashort pulses, pulse cleaning and CEP stable sub-3fs pulse

    NASA Astrophysics Data System (ADS)

    Kobayashi, Takayoshi; Liu, Jun; Okamura, Kotaro

    2012-04-01

    Our recent experimental results of three methods related to and useful for the generation of attosecond pulses are summarized. The pulses obtained by all of them have high qualities in terms of phase, temporal, spectral and spatial properties which are based on the physical principles associated with the parametric processes. First, carrier-envelope phase (CEP) stable sub-5 fs and sub-3 fs pulses by non-collinear optical parametric amplification (NOPA) in the near-infrared and visible spectral range will be described. The mechanism of the passive CEP stabilization is described. Passively stabilized idler and its second harmonic (SH) pulses from NOPAs are compressed to sub-5fs and sub-3fs, respectively. Compression of the idler output from a NOPA and its SH is attained with a specially designed characterization method during the compression. Second, generation of multicolour pulses by the cascaded four-wave mixing process in bulk media is discussed. As short as 15-fs multicoloured femtosecond pulses are obtained with two ˜40 fs pulses incident to a fused-silica glass plate by this method. These broadband multicolour sidebands are expected to provide single-cycle or sub-fs pulses after the Fourier synthesis. Third, a new technique based on self-diffraction in the Kerr medium is used to clean and shorten the femtosecond laser pulse. The cleaned pulse with high temporal contrast is expected to be used as a seed for a background-free petawatt laser system and then used as the laser source for high-energy attosecond pulse generation in a solid target. The mechanisms of CEP stabilization, pulse spectral smoothening and pulse contrast enhancement are comparatively discussed.

  13. Single-shot implementation of dispersion-scan for the characterization of ultrashort laser pulses.

    PubMed

    Fabris, D; Holgado, W; Silva, F; Witting, T; Tisch, J W G; Crespo, H

    2015-12-14

    We demonstrate a single-shot ultrafast diagnostic, based on the dispersion-scan (d-scan) technique. In this implementation, rather than translating wedges to vary the dispersion as in scanning d-scan, the pulse to be measured experiences a spatially varying amount of dispersion in a prism. The resulting beam is then imaged into a second-harmonic generation crystal and an imaging spectrometer is used to measure the two-dimensional trace, which is analyzed using the d-scan retrieval algorithm. We compare the single-shot implementation with the scanning d-scan for the measurement of sub-3.5-fs pulses from a hollow core fiber pulse compressor. We show that the retrieval algorithm used to extract amplitude and phase of the pulse provides comparable results, proving the validity of the new single-shot implementation in the near single-cycle regime. PMID:26699069

  14. Generation of a periodic sequence of powerful ultrashort pulses in a traveling wave tube with bleachable absorber in the feedback loop

    NASA Astrophysics Data System (ADS)

    Ginzburg, N. S.; Denisov, G. G.; Vilkov, M. N.; Zotova, I. V.; Sergeev, A. S.

    2015-09-01

    It is shown that a periodic series of ultrashort pulses can be formed in electron microwave generators with a bleachable absorber in the feedback loop. The peak power of such radiation is considerably higher than radiation power in stationary modes. The pulsed generation method is analogous to the method of passive synchronization of waves, which is widely used in laser physics.

  15. Studies of inactivation mechanism of non-enveloped icosahedral virus by a visible ultrashort pulsed laser

    PubMed Central

    2014-01-01

    Background Low-power ultrashort pulsed (USP) lasers operating at wavelengths of 425 nm and near infrared region have been shown to effectively inactivate viruses such as human immunodeficiency virus (HIV), M13 bacteriophage, and murine cytomegalovirus (MCMV). It was shown previously that non-enveloped, helical viruses such as M13 bacteriophage, were inactivated by a USP laser through an impulsive stimulated Raman scattering (ISRS) process. Recently, enveloped virus like MCMV has been shown to be inactivated by a USP laser via protein aggregation induced by an ISRS process. However, the inactivation mechanism for a clinically important class of viruses – non-enveloped, icosahedral viruses remains unknown. Results and discussions We have ruled out the following four possible inactivation mechanisms for non-enveloped, icosahedral viruses, namely, (1) inactivation due to ultraviolet C (UVC) photons produced by non-linear optical process of the intense, fundamental laser beam at 425 nm; (2) inactivation caused by thermal heating generated by the direct laser absorption/heating of the virion; (3) inactivation resulting from a one-photon absorption process via chromophores such as porphyrin molecules, or indicator dyes, potentially producing reactive oxygen or other species; (4) inactivation by the USP lasers in which the extremely intense laser pulse produces shock wave-like vibrations upon impact with the viral particle. We present data which support that the inactivation mechanism for non-enveloped, icosahedral viruses is the impulsive stimulated Raman scattering process. Real-time PCR experiments show that, within the amplicon size of 273 bp tested, there is no damage on the genome of MNV-1 caused by the USP laser irradiation. Conclusion We conclude that our model non-enveloped virus, MNV-1, is inactivated by the ISRS process. These studies provide fundamental knowledge on photon-virus interactions on femtosecond time scales. From the analysis of the transmission

  16. Tracking propagation of ultrashort intense laser pulses in gases via probing of ionization.

    PubMed

    Gizzi, L A; Betti, S; Galimberti, M; Giulietti, A; Giulietti, D; Labate, L; Levato, T; Tomassini, P; Monot, P; Ceccotti, T; De Oliveira, P; Martin, Ph

    2009-05-01

    We use optical interferometry to study the propagation of femtosecond laser pulses in gases. We show the measurements of propagation in a nitrogen gas jet and we compare the results with propagation in He under the same irradiation conditions. We find that in the case of nitrogen, the detailed temporal structure of the laser pulse can be tracked and visualized by measuring the phase and the resulting electron-density map. A dramatically different behavior occurs in He gas jets, where no details of the temporal structure of the laser pulse are visible. These observations are explained in terms of the ionization dynamics of nitrogen compared to helium. These circumstances make N2 gas sensitive to variations in the electric field and, therefore, allow the laser-pulse temporal and spatial structures to be visualized in detail. PMID:19518574

  17. Tracking propagation of ultrashort intense laser pulses in gases via probing of ionization

    SciTech Connect

    Gizzi, L. A.; Betti, S.; Giulietti, A.; Giulietti, D.; Labate, L.; Levato, T.; Tomassini, P.; Galimberti, M.; Monot, P.; Ceccotti, T.; De Oliveira, P.; Martin, Ph.

    2009-05-15

    We use optical interferometry to study the propagation of femtosecond laser pulses in gases. We show the measurements of propagation in a nitrogen gas jet and we compare the results with propagation in He under the same irradiation conditions. We find that in the case of nitrogen, the detailed temporal structure of the laser pulse can be tracked and visualized by measuring the phase and the resulting electron-density map. A dramatically different behavior occurs in He gas jets, where no details of the temporal structure of the laser pulse are visible. These observations are explained in terms of the ionization dynamics of nitrogen compared to helium. These circumstances make N{sub 2} gas sensitive to variations in the electric field and, therefore, allow the laser-pulse temporal and spatial structures to be visualized in detail.

  18. Fast magnetic-field annihilation in the relativistic collisionless regime driven by two ultrashort high-intensity laser pulses.

    PubMed

    Gu, Y J; Klimo, O; Kumar, D; Liu, Y; Singh, S K; Esirkepov, T Zh; Bulanov, S V; Weber, S; Korn, G

    2016-01-01

    The magnetic quadrupole structure formation during the interaction of two ultrashort high power laser pulses with a collisionless plasma is demonstrated with 2.5-dimensional particle-in-cell simulations. The subsequent expansion of the quadrupole is accompanied by magnetic-field annihilation in the ultrarelativistic regime, when the magnetic field cannot be sustained by the plasma current. This results in a dominant contribution of the displacement current exciting a strong large scale electric field. This field leads to the conversion of magnetic energy into kinetic energy of accelerated electrons inside the thin current sheet. PMID:26871179

  19. Surface modification of organic polymer by dual action of extreme ultraviolet/visible-near infrared ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Mocek, T.; Polan, J.; Homer, P.; Jakubczak, K.; Rus, B.; Kim, I. J.; Kim, C. M.; Lee, G. H.; Nam, C. H.; Hájková, V.; Chalupský, J.; Juha, L.

    2009-01-01

    We present the experimental evidence of structural surface modifications of poly(methyl methacrylate) (PMMA) caused by simultaneous action of extreme ultraviolet (XUV) (˜21 nm) and visible-near infrared (visible-NIR) (820/410 nm) ultrashort pulses. Although the fluence of each individual beam was far below the surface modification threshold, very efficient and specific material expansion was observed after irradiation of PMMA by more than ˜20 shots of mixed XUV/visible-NIR radiation. As the XUV photons generate free charge carriers, absorption of the optical radiation dramatically increases, which heats up the material and further enhances the XUV induced damage to the polymer chain.

  20. Surface modification of organic polymer by dual action of extreme ultraviolet/visible-near infrared ultrashort pulses

    SciTech Connect

    Mocek, T.; Polan, J.; Homer, P.; Jakubczak, K.; Rus, B.; Kim, I. J.; Kim, C. M.; Lee, G. H.; Nam, C. H.; Hajkova, V.; Chalupsky, J.; Juha, L.

    2009-01-15

    We present the experimental evidence of structural surface modifications of poly(methyl methacrylate) (PMMA) caused by simultaneous action of extreme ultraviolet (XUV) ({approx}21 nm) and visible-near infrared (visible-NIR) (820/410 nm) ultrashort pulses. Although the fluence of each individual beam was far below the surface modification threshold, very efficient and specific material expansion was observed after irradiation of PMMA by more than {approx}20 shots of mixed XUV/visible-NIR radiation. As the XUV photons generate free charge carriers, absorption of the optical radiation dramatically increases, which heats up the material and further enhances the XUV induced damage to the polymer chain.

  1. Effects of higher-order Kerr nonlinearity and plasma diffraction on multiple filamentation of ultrashort laser pulses in air

    SciTech Connect

    Huang, T. W.; Zhou, C. T.; Zhang, H.; He, X. T.

    2013-07-15

    The effect of higher-order Kerr nonlinearity on channel formation by, and filamentation of, ultrashort laser pulses propagating in air is considered. Filament patterns originating from multiphoton ionization of the air molecules with and without the higher-order Kerr and molecular-rotation effects are investigated. It is found that diverging multiple filaments are formed if only the plasma-induced defocusing effect is included. In the presence of the higher-order Kerr effects, the light channel can exist for a long distance. The effect of noise on the filament patterns is also discussed.

  2. Effects of higher-order Kerr nonlinearity and plasma diffraction on multiple filamentation of ultrashort laser pulses in air

    NASA Astrophysics Data System (ADS)

    Huang, T. W.; Zhou, C. T.; Zhang, H.; He, X. T.

    2013-07-01

    The effect of higher-order Kerr nonlinearity on channel formation by, and filamentation of, ultrashort laser pulses propagating in air is considered. Filament patterns originating from multiphoton ionization of the air molecules with and without the higher-order Kerr and molecular-rotation effects are investigated. It is found that diverging multiple filaments are formed if only the plasma-induced defocusing effect is included. In the presence of the higher-order Kerr effects, the light channel can exist for a long distance. The effect of noise on the filament patterns is also discussed.

  3. The simulation of hard X-ray generation at ultra-short laser pulse interaction with high-Z targets

    SciTech Connect

    Lykov, V. A.; Chernyakov, V. E.; Chikulaev, A. A.; Kandiev, Ya. Z.; Nikolaev, V. G.

    1997-04-15

    The simulations of fast electrons interaction with matter were performed by using of ERA code. The yield and angular distribution of bremsstrahlung and fluorescence K-{alpha} X-ray radiation calculated by PRIZMA code for experiments on interaction of ultra-short laser pulses with high-Z targets at intensities of 10{sup 15}-10{sup 18} W/cm{sup 2} are presented. Spherical targets with conical hollows and conical targets of high-Z matter are proposed for experiments with picosecond lasers to increase the brightness of hard X-ray source.

  4. Interband photorefractive effect in beta-BBO crystal due to multiphoton excitation by intense ultrashort optical pulses.

    PubMed

    Xu, Shixiang; Cai, Hua; Zeng, Heping

    2007-08-20

    This paper presents the first experimental observation of interband photo- refractive (PR) effects in beta-BBO crystal due to multiphoton excitation with intense ultrashort pulses. In order to fully characterize the PR effects, a sensitive intracavity scheme is developed to magnify the dynamics of nonlinear lenses induced by the PR effects. The reproducible PR phenomena depend strongly on the power, wavelength, and spatial intensity profile of the intense laser pulses and the electro-optic coefficient of the optical materials. Its response time is from tens of seconds to several minutes. The results may be very helpful for us to find a solution to overcome the deleterious influence of multiphoton induced photo-charges on nonlinear optical frequency conversions, e.g. optical parametric chirped pulse amplification. PMID:19547410

  5. All solid-state spectral broadening: an average and peak power scalable method for compression of ultrashort pulses.

    PubMed

    Seidel, Marcus; Arisholm, Gunnar; Brons, Jonathan; Pervak, Vladimir; Pronin, Oleg

    2016-05-01

    Spectral broadening in bulk material is a simple, robust and low-cost method to extend the bandwidth of a laser source. Consequently, it enables ultrashort pulse compression. Experiments with a 38 MHz repetition rate, 50 W average power Kerr-lens mode-locked thin-disk oscillator were performed. The initially 1.2 μJ, 250 fs pulses are compressed to 43 fs by means of self-phase modulation in a single 15 mm thick quartz crystal and subsequent chirped-mirror compression. The losses due to spatial nonlinear effects are only about 40 %. A second broadening stage reduced the Fourier transform limit to 15 fs. It is shown that the intensity noise of the oscillator is preserved independent of the broadening factor. Simulations manifest the peak power scalability of the concept and show that it is applicable to a wide range of input pulse durations and energies. PMID:27137557

  6. Ultrashort pulse laser drilling of metals using a high-repetition rate high average power fiber CPA system

    NASA Astrophysics Data System (ADS)

    Ancona, A.; Jauregui, C.; Döring, S.; Röser, F.; Limpert, J.; Nolte, S.; Tünnermann, A.

    2009-02-01

    We present an experimental study of the drilling of metal targets with ultrashort laser pulses with pulse durations from 800 fs to 19 ps at repetition rates up to 1 MHz, average powers up to 70 Watts, using an Ytterbium-doped fiber CPA system. Particle shielding and heat accumulation have been found to influence the drilling efficiency at high repetition rates. Particle shielding causes an increase in the number of pulses for breakthrough. It occurs at a few hundred kHz, depending on the pulse energy and duration. The heat accumulation effect is noticed at higher repetition rates. Although it overbalances the particle shielding thus making the drilling process faster, heat accumulation is responsible for the formation of a large amount of molten material that limits the hole quality. The variations of the pulse duration reveal that heat accumulation starts at higher repetition rates for shorter pulse lengths. This is in agreement with the observed higher ablation efficiency with shorter pulse duration. Thus, the shorter pulses might be advantageous if highest precision and processing speed is required.

  7. Optimal control of high-order harmonics for the generation of an isolated ultrashort attosecond pulse with two-color midinfrared laser fields

    NASA Astrophysics Data System (ADS)

    Chou, Yi; Li, Peng-Cheng; Ho, Tak-San; Chu, Shih-I.

    2015-06-01

    We present an efficient high-order-harmonic optimal control scheme for the generation of the ultrabroad supercontinuum spectrum and an isolated ultrashort attosecond pulse in gases with a two-color mid-IR laser field. The optimal control scheme is implemented using a derivative-free unconstrained optimization algorithm called NEWUOA (NEW Unconstrained Optimization Algorithm). For illustration, the high-order-harmonic generation (HHG) of a hydrogen atom is considered for optimization. It is shown that optimally shaped laser waveforms can greatly enhance and extend the HHG plateau and efficiently generate an isolated ultrashort attosecond pulse. Moreover, by performing accurate semiclassical simulations and a detailed wavelet time-frequency analysis, we found that the optimized supercontinuum harmonics corresponding to long-trajectory electrons are responsible for an isolated ultrashort 21-as pulse.

  8. Non-filamentated ultra-intense and ultra-short pulse fronts in three-dimensional Raman seed amplification

    SciTech Connect

    Lehmann, G.; Spatschek, K. H.

    2014-05-15

    Ultra-intense and ultra-short laser pulses may be generated up to the exawatt-zetawatt regime due to parametric processes in plasmas. The minimization of unwanted plasma processes leads to operational limits which are discussed here with respect to filamentation. Transverse filamentation, which originally was derived for plane waves, is being investigated for seed pulse propagation in the so called π-pulse limit. A three-dimensional (3D) three-wave-interaction model is the basis of the present investigation. To demonstrate the applicability of the three-wave-interaction model, the 1D pulse forms are compared with those obtained from 1D particle in cell and Vlasov simulations. Although wave-breaking may occur, the kinetic simulations show that the leading pumped pulse develops a form similar to that obtained from the three-wave-interaction model. In the main part, 2D and 3D filamentation processes of (localized) pulses are investigated with the three-wave-interaction model. It is shown that the leading pulse front can stay filamentation-free, whereas the rear parts show transverse modulations.

  9. Experimental and Theoretical Investigation of Periodic Nanostructuring of Au with Ultrashort UV Laser Pulses near the Damage Threshold

    NASA Astrophysics Data System (ADS)

    Ivanov, D. S.; Lipp, V. P.; Blumenstein, A.; Kleinwort, F.; Veiko, V. P.; Yakovlev, E.; Roddatis, V.; Garcia, M. E.; Rethfeld, B.; Ihlemann, J.; Simon, P.

    2015-12-01

    The mechanism of surface restructuring by ultrashort laser pulses involves a number of fast, nonequilibrium, and interrelated processes while the solid is in a transient state. As a result, the analysis of the experimental data cannot address all of the mechanisms of nanostructuring. In this paper, we present a direct comparison of a simulation and the experimental results of surface nanomodifications induced by a single laser pulse. The experimental results are obtained by using a mask-projection setup with a laser wavelength of 248 nm and a pulse length of 1.6 ps. Two-beam interference of this short wavelength allows for producing a large-area intensity grating of 40 μ m in diameter on a gold surface with a sinusoidal shape and a period of 500 nm. The formed structures are analyzed at the surface and in a cross section by a scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. Then a hybrid atomistic-continuum model capable of capturing the essential mechanisms responsible for the nanostructuring process is used to model the interaction of the laser pulse with a thick gold target. The good agreement between the modeling results and the experimental data justifies the proposed approach as a powerful tool revealing the physics behind the nanostructuring process at a gold surface and providing a microscopic insight into the dynamics of the structuring processes of metals in general. The presented model, therefore, is an important step towards a computational tool for predicting a materials response to an ultrashort laser pulse on the atomic scale. This detailed understanding of the dynamics of the process will pave the way towards predesigned topologies for functionalized surfaces on nanoscales and microscales.

  10. Time-resolved resonant photoionization of He using a time-dependent Feshbach method with ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Granados-Castro, C. M.; Sanz-Vicario, J. L.

    2013-03-01

    We study the photoionization and autoionization of the helium atom subject to ultrashort laser pulses by using a Feshbach formalism in the time domain. We solve the time-dependent Schrödinger equation in terms of a configuration interaction (CI) spectral method, in which the total wavefunction is expanded with configurations defined within bound-like ( {Q}) and scattering-like ( {P}) halfspaces. The method allows one to provide accurate descriptions of both the atomic structure (energy positions and widths) and the photodynamics. We illustrate our approach by (i) calculating the time-resolved one-photon ionization below the He+ (n = 2) ionization threshold, from 11Se and 21Po initial states, then reaching the lowest autoionizing states of 1Se, 1Po and 1De final symmetries, (ii) studying the temporal formation of the Fano profile of 1Po resonances and (iii) showing its performance in obtaining the perturbative long-time limit of one- and two-photon ionization cross sections using ultrashort laser pulses following a recently developed procedure in Palacios et al (2008 Phys. Rev. A 77 032716).

  11. Features of the interaction of ultrashort laser pulses with a thin semiconductor film caused by the generation of excitons and biexcitons

    SciTech Connect

    Khadzhi, P I; Corovai, A V

    2002-08-31

    Nonstationary transmission (reflection) of two time-separated ultrashort laser pulses by thin semiconductor films is studied. Photons of one of these pulses generate biexcitons in the films due to two-photon absorption from the crystal ground state, while photons of the other pulse induce an optical exciton - biexciton conversion. Several basically new effects in nonstationary light transmission (reflection) are found and interpreted. (nonlinear optical phenomena)

  12. Compression of ultra-short light pulses using the graded refractive index one-dimensional photonic crystals

    NASA Astrophysics Data System (ADS)

    Shiri, R.; Bananej, A.; Safari, E.

    2016-09-01

    The one-dimensional photonic crystals (1D PCs) containing a graded refractive index layer have been theoretically utilized to compress the positively chirped ultra-short pulses of light. Two types of simple and graded index multi-layer structures consisting alternating layers of TiO2 and SiO2 with the same total thicknesses and periodicity have been investigated and compared. For the graded structure, three different refractive index distributions including linear, exponential and parabolic profiles have been considered. The results revealed that replacing one of the homogeneous layers of the unit cells in simple photonic crystal with a graded material having parabolic refractive index profile efficiently improves compression behavior of the structure. The compress factors of as much as 47% and 78% depending on the pulse's initial chirp rate obtained with parabolic profile of such the structures.

  13. Dynamic control of laser driven proton beams by exploiting self-generated, ultrashort electromagnetic pulses

    NASA Astrophysics Data System (ADS)

    Kar, S.; Ahmed, H.; Nersisyan, G.; Brauckmann, S.; Hanton, F.; Giesecke, A. L.; Naughton, K.; Willi, O.; Lewis, C. L. S.; Borghesi, M.

    2016-05-01

    As part of the ultrafast charge dynamics initiated by high intensity laser irradiations of solid targets, high amplitude EM pulses propagate away from the interaction point and are transported along any stalks and wires attached to the target. The propagation of these high amplitude pulses along a thin wire connected to a laser irradiated target was diagnosed via the proton radiography technique, measuring a pulse duration of ˜20 ps and a pulse velocity close to the speed of light. The strong electric field associated with the EM pulse can be exploited for controlling dynamically the proton beams produced from a laser-driven source. Chromatic divergence control of broadband laser driven protons (upto 75% reduction in divergence of >5 MeV protons) was obtained by winding the supporting wire around the proton beam axis to create a helical coil structure. In addition to providing focussing and energy selection, the technique has the potential to post-accelerate the transiting protons by the longitudinal component of the curved electric field lines produced by the helical coil lens.

  14. Circularly polarized attosecond pulses from molecular high-order harmonic generation by ultrashort intense bichromatic circularly and linearly polarized laser pulses

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Bandrauk, André D.

    2012-04-01

    We describe the generation of high-order elliptically and circularly polarized harmonic spectra in an aligned H+2 molecule ion by a combination of two-colour ultrashort intense laser fields from numerical solutions of the corresponding time-dependent Schrödinger equation (TDSE). In intense bichromatic circularly and linearly or circularly polarized laser pulses with intensity I0 and angular frequencies ω0 and 2ω0, it is found that maximum molecular high-order harmonic generation (MHOHG) energies are functions of the molecular internuclear distance. Based on a classical model of laser-induced electron collisions with neighbouring ions, the optimal values of the pulse relative carrier envelope phase phi, the molecular internuclear distance R and the angle thetav of molecular alignment to the laser polarization axis are obtained for efficiently producing MHOHG spectra with the maximum harmonic energy Ip + 13.5Up, where Ip is the ionization potential of the molecule and Up = I0/4meω20 is the ponderomotive energy of the continuum electron at intensity I0 and frequency ω0 of the laser pulse. The results have been confirmed from corresponding TDSE nonperturbative numerical simulations. The polarization property of the generated harmonics is also presented. The mechanism of MHOHG is further characterized with a Gabor time frequency analysis. It is confirmed that a single collision trajectory of the continuum electron with neighbouring ions dominates in the MHOHG processes. The high efficiency of the proposed MHOHG scheme provides a possible source for production of elliptically and/or circularly polarized attosecond extreme ultraviolet pulses. Circularly polarized attosecond pulses can also be generated by using intense ultrashort circularly polarized laser pulses in combination with static electric fields of comparable intensity for H+2 at equilibrium. A time frequency analysis also confirms the role of single recollisions as the dominant mechanism of the generation

  15. Pulse measurement apparatus and method

    DOEpatents

    Marciante, John R.; Donaldson, William R.; Roides, Richard G.

    2011-10-25

    An embodiment of the invention is directed to a pulse measuring system that measures a characteristic of an input pulse under test, particularly the pulse shape of a single-shot, nano-second duration, high shape-contrast optical or electrical pulse. An exemplary system includes a multi-stage, passive pulse replicator, wherein each successive stage introduces a fixed time delay to the input pulse under test, a repetitively-gated electronic sampling apparatus that acquires the pulse train including an entire waveform of each replica pulse, a processor that temporally aligns the replicated pulses, and an averager that temporally averages the replicated pulses to generate the pulse shape of the pulse under test. An embodiment of the invention is directed to a method for measuring an optical or an electrical pulse shape. The method includes the steps of passively replicating the pulse under test with a known time delay, temporally stacking the pulses, and temporally averaging the stacked pulses. An embodiment of the invention is directed to a method for increasing the dynamic range of a pulse measurement by a repetitively-gated electronic sampling device having a rated dynamic range capability, beyond the rated dynamic range of the sampling device; e.g., enhancing the dynamic range of an oscilloscope. The embodied technique can improve the SNR from about 300:1 to 1000:1. A dynamic range enhancement of four to seven bits may be achieved.

  16. SHG spectroscopy of gallium nitride thin films on sapphire with ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Angerer, William Edward

    We present results of ultrafast second-harmonic generation spectroscopy of GaN/Alsb2Osb3 samples. We develop a formalism to calculate the nonlinear response of thin nonlinear films excited by an ultrashort laser source (Ti:Alsb2Osb3), and we use this formalism to extract chisbsp{zxx}{(2)}(omega=2omegasb{o}) and chisbsp{xzx}{(2)}(omega=2omegasb{o}) from our SHG measurements over a two photon energy range of 2.6-3.4 eV. By comparing spectra from several samples, we find a weak sub-band gap enhancement of chisbsp{zxx}{(2)}(omega=2omegasb{o}) at a two photon energy of 2.80 eV that is not present in chisbsp{xzx}{(2)}(omega=2omegasb{o}). This enhancement is independent of the carrier concentration, intentional doping, and presence of the "yellow luminescence band" defects. This feature may result from a three photon process involving a midgap defect state. We analyze three photon processes that include a defect state with group theory and demonstrate that several processes contribute to chisbsp{zxx}{(2)}(omega=2omegasb{o}) but not to chisbsp{xzx}{(2)}(omega=2omegasb{o}). In addition, we determined sample orientational miscuts by rotational SHG, and we found that these miscuts do not generate strain induced interface states. We determined a Sellmeier dispersion relationship for the index of refraction of GaN by a novel light transmission method, and we report on photoluminescence of our GaN/Alsb2Osb3 samples. In a second project we have designed and built a nonlinear optical microscope. We have used the new tool to perform preliminary investigations of the nonlinear optical properties of carbon nanoropes. We suggest that nonlinear optical microscopy is a potentially useful technique for analyzing carbon nanotube symmetry, as well as in studies of other heterogeneities. Finally, we place an upper limit on the dominant second order hyperpolarizability, alphasbsp{zzz}{(2)}, of carbon nanotubes based on our nonlinear optical microscopy measurements.

  17. Comparison of different processes for separation of glass and crystals using ultrashort pulsed lasers

    NASA Astrophysics Data System (ADS)

    Kumkar, M.; Bauer, L.; Russ, S.; Wendel, M.; Kleiner, J.; Grossmann, D.; Bergner, K.; Nolte, S.

    2014-03-01

    We investigate cutting of transparent materials using ultra short laser pulses with pulse durations in the sub to a few ps regime. All compared methods base on nonlinear absorption including ablation cutting and cleaving or selective etching supported by laser induced modification inside the bulk material. For most of the experiments samples of hardened glass (Corning Gorilla®) with thickness up to 700 μm were used, ablation cutting of sapphire is presented additionally. Absorption and modification inside the volume is analyzed in detail, aiming for tailored modifications. Besides optical microscopy a pump probe setup was used. We show results of time resolved absorption measurements of 6 ps pulses focused into the volume. We observe shielding due to the interaction region and accumulation effects influencing the modifications. First results on inscribing and cutting by using beam shaping indicate the importance of tailoring the shape and arrangement of the pulses temporally and spatially. The results presented for the different cutting methods supports an assessment of the individual potential and a selection of the applicable method based on the requirements.

  18. Generation and measurement of velocity bunched ultrashort bunch of pC charge

    NASA Astrophysics Data System (ADS)

    Lu, X. H.; Tang, C. X.; Li, R. K.; To, H.; Andonian, G.; Musumeci, P.

    2015-03-01

    In this paper, we discuss the velocity compression in a short rf linac of an electron bunch from a rf photoinjector operated in the blowout regime. Particle tracking simulations shows that with a beam charge of 2 pC an ultrashort bunch duration of 16 fs can be obtained at a tight longitudinal focus downstream of the linac. A simplified coherent transition radiation (CTR) spectrum method is developed to enable the measurement of ultrashort (sub-50 fs) bunches at low bunch energy (5 MeV) and low bunch charges (<10 pC ). In this method, the ratio of the radiation energy selected by two narrow bandwidth filters is used to estimate the bunch length. The contribution to the coherent form factor of the large transverse size of the bunch suppresses the radiation signal significantly and is included in the analysis. The experiment was performed at the UCLA Pegasus photoinjector laboratory. The measurement results show bunches of sub-40 fs with 2 pC of charge well consistent with the simulation using actual experimental conditions. These results open the way to the generation of ultrashort bunches with time-duration below 10 fs once some of the limitations of the setup (rf phase jitter, amplitude instability and low field in the gun limited by breakdown) are corrected.

  19. Identification of Ions Generated by Ultrashort Laser Pulses using Thomson Spectrometer

    NASA Astrophysics Data System (ADS)

    Oishi, Yuji; Nayuki, Takuya; Fujii, Takashi; Nemoto, Koshichi; Kayoiji, Tsutomu; Horioka, Kazuhiko; Okano, Yasuaki; Hironaka, Yoichiro; Nakamura, Kazutaka G.; Kondo, Ken-ichi

    2002-10-01

    Fast ions generated by irradiation of laser pulses of width 55 fs, intensity 8.6 × 1018 W/cm2 on 5 μ m thickness copper film were measured by use of a Thomson mass spectrometer. From the spectgram, ions ejected from the target surface which was opposite side of the laser irradiation were determined to be protons. Copper ions were not observed. From the enegy measurements using Mylar filter method, the maximum proton energy was estimated more than 650 keV.

  20. Frequency doubling and tripling of ultrashort laser pulses in biological tissues

    SciTech Connect

    Da Silva, L. B.; Eichler, J.; Joslin, E. J.; Kim, B.-M.

    1998-07-24

    Structural proteins such as collagen and elastin are known to generate second harmonic at high laser intensities. Second and third harmonic generations (SHG, THG) of 0.4 ps Ti-Sapphire laser radiation at 800 nm were observed in various biological tissues. Dependence of SHG on laser pulse energy and pulse width was investigated. Reflected second harmonic yield was measured for animal tissue in vitro and human skin in vivo. The yield varies about a factor of 20 for various areas of the skin while the scattered laser radiation (diffuse reflectance) varies only by a factor of 2. In some cases the THG efficiency was comparable to the SHG. Possible applications of higher harmonic radiation for diagnostics and microscopy are discussed.

  1. Formation of ultrashort pulses via quantum interference between Stark-split atomic transitions in a hydrogenlike medium

    NASA Astrophysics Data System (ADS)

    Antonov, V. A.; Radeonychev, Y. V.; Kocharovskaya, Olga

    2013-11-01

    We derive the analytical solution uncovering the origin of the ultrashort pulse formation from the resonant radiation in a hydrogenlike medium [Y. V. Radeonychev, V. A. Polovinkin, and O. Kocharovskaya, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.183902 105, 183902 (2010)], which is a quantum interference of the atomic transitions from the ground to the first excited energy level split by an intense far-off-resonant laser field due to the instantaneous Stark effect into the periodically oscillating sublevels and interference of the resonantly scattered radiation with the incident one. The analytical solution shows that the pulses are almost bandwidth limited and can be produced in a wide range of parameters in excellent agreement with the more general numerical simulation. The experimental schemes to form few-femtosecond pulses from 122-nm radiation in atomic hydrogen as well as few-hundred-attosecond pulses from 13.74-nm radiation in a Li2+ medium are discussed.

  2. Ionization-induced blueshift of high-peak-power guided-wave ultrashort laser pulses in hollow-core photonic-crystal fibers

    SciTech Connect

    Fedotov, A. B.; Serebryannikov, E. E.; Zheltikov, A. M.

    2007-11-15

    Ionization-induced change in the refractive index of a gas is shown to give rise to a substantial spectral blueshift of megawatt light pulses transmitted through a gas-filled hollow photonic-crystal fiber (PCF). This effect suggests the ways of controlling not only the rate, but also the sign of the soliton frequency shift for high-peak-power ultrashort light pulses guided in hollow PCFs filled with Raman-active ionizing gases.

  3. Generation of a Periodic Series of High-Power Ultra-Short Pulses in a Gyro-TWT with a Bleachable Cyclotron Absorber in the Feedback Circuit

    NASA Astrophysics Data System (ADS)

    Vilkov, M. N.; Ginzburg, N. S.; Denisov, G. G.; Zotova, I. V.; Sergeev, A. S.

    2016-01-01

    We demonstrate the possibility of forming a periodic series of ultra-short pulses, which has a peak power exceeding significantly the radiation power in stationary regimes, in a gyroresonance traveling-wave tube (gyro-TWT) with a bleachable cyclotron absorber in the feedback circuit. The mechanism of pulsed generation is similar to the method of passive mode locking, which is used widely in laser physics.

  4. Interaction of ultrashort x-ray pulses with B{sub 4}C, SiC, and Si

    SciTech Connect

    Bergh, M.; Timneanu, N.; Hau-Riege, S. P.; Scott, H. A.

    2008-02-15

    The interaction of 32.5 and 6 nm ultrashort x-ray pulses with the solid materials B{sub 4}C, SiC, and Si is simulated with a nonlocal thermodynamic equilibrium radiation transfer code. We study the ionization dynamics as a function of depth in the material and modifications of the opacity during irradiation, and estimate the crater depth. Furthermore, we compare the estimated crater depth with experimental data, for fluences up to 2.2 J/cm{sup 2}. Our results show that, at 32.5 nm irradiation, the opacity changes by less than a factor of 2 for B{sub 4}C and Si and by a factor of 3 for SiC, for fluences up to 200 J/cm{sup 2}. At a laser wavelength of 6 nm, the model predicts a dramatic decrease in opacity due to the weak inverse bremsstrahlung, increasing the crater depth for high fluences.

  5. The new methods of treatment for age-related macular degeneration using the ultra-short pulsed laser

    NASA Astrophysics Data System (ADS)

    Iwamoto, Yumiko; Awazu, Kunio; Suzuki, Sachiko; Ohshima, Tetsuro; Sawa, Miki; Sakaguchi, Hirokazu; Tano, Yasuo; Ohji, Masahito

    2007-02-01

    The non-invasive methods of treatments have been studying for the improvement of quality of life (QOL) of patients undergoing treatment. A photodynamic therapy (PDT) is one of the non-invasive treatments. PDT is the methods of treatment using combination of a laser and a photosensitizer. PDT has few risks for patients. Furthermore, PDT enables function preservation of a disease part. PDT has been used for early cancer till now, but in late years it is applied for age-related macular degeneration (AMD). AMD is one of the causes of vision loss in older people. However, PDT for AMD does not produce the best improvement in visual acuity. The skin photosensivity by an absorption characteristic of a photosensitizer is avoided. We examined new PDT using combination of an ultra-short pulsed laser and indocyanine green (ICG).

  6. Asynchronous electro-optic sampling of all-electronically generated ultrashort voltage pulses

    NASA Astrophysics Data System (ADS)

    Füser, Heiko; Bieler, Mark; Ahmed, Sajjad; Verbeyst, Frans

    2015-02-01

    We measure the output of an electrical pulse generator with a repetition rate of 76 MHz employing a laser-based asynchronous sampling technique with an effective sampling frequency of 250 GHz. A best estimate of the resulting 13 ns long waveform is obtained from multiple waveform measurements, which are taken without any trigger event and subsequently aligned in time. This asynchronous sampling scheme can even be adopted in situations where small phase drifts between the electrical pulse generator and the laser occur, making synchronized sampling very difficult. In addition to accurate measurements, the proposed asynchronous measurement scheme allows for the construction of covariance matrices with full rank since a large number of time traces is acquired. Such matrices might reveal correlations which do not appear in low-rank matrices. We believe that the asynchronous sampling technique advocated in this paper will prove to be a valuable characterization tool covering an ultra-broadband frequency range from below 100 MHz to above 100 GHz.

  7. Measurement of T1 of the Ultrashort T2* Components in White Matter of the Brain at 3T

    PubMed Central

    Du, Jiang; Sheth, Vipul; He, Qun; Carl, Michael; Chen, Jun; Corey-Bloom, Jody; Bydder, Graeme M.

    2014-01-01

    Recent research demonstrates that white matter of the brain contains not only long T2 components, but a minority of ultrashort T2* components. Adiabatic inversion recovery prepared dual echo ultrashort echo time (IR-dUTE) sequences can be used to selectively image the ultrashort T2* components in white matter of the brain using a clinical whole body scanner. The T2*s of the ultrashort T2* components can be quantified using mono-exponential decay fitting of the IR-dUTE signal at a series of different TEs. However, accurate T1 measurement of the ultrashort T2* components is technically challenging. Efficient suppression of the signal from the majority of long T2 components is essential for robust T1 measurement. In this paper we describe a novel approach to this problem based on the use of IR-dUTE data acquisitions with different TR and TI combinations to selectively detect the signal recovery of the ultrashort T2* components. Exponential recovery curve fitting provides efficient T1 estimation, with minimized contamination from the majority of long T2 components. A rubber phantom and a piece of bovine cortical bone were used for validation of this approach. Six healthy volunteers were studied. An averaged T2* of 0.32±0.09 ms, and a short mean T1 of 226±46 ms were demonstrated for the healthy volunteers at 3T. PMID:25093859

  8. Two-photon double ionization of the helium atom by ultrashort pulses

    SciTech Connect

    Palacios, Alicia; Horner, Daniel A; Rescigno, Thomas N; McCurdy, C William

    2010-05-14

    Two-photon double ionization of the helium atom was the subject of early experiments at FLASH and will be the subject of future benchmark measurements of the associated electron angular and energy distributions. As the photon energy of a single femtosecond pulse is raised from the threshold for two-photon double ionization at 39.5 eV to beyond the sequential ionization threshold at 54.4 eV, the electron ejection dynamics change from the highly correlated motion associated with nonsequential absorption to the much less correlated sequential ionization process. The signatures of both processes have been predicted in accurate \\textit{ab initio} calculations of the joint angular and energy distributions of the electrons, and those predictions contain some surprises. The dominant terms that contribute to sequential ionization make their presence apparent several eV below that threshold. In two-color pump probe experiments with short pulses whose central frequencies require that the sequential ionization process necessarily dominates, a two-electron interference pattern emerges that depends on the pulse delay and the spin state of the atom.

  9. Exploiting shot noise correlations in the photodetection of ultrashort optical pulse trains

    NASA Astrophysics Data System (ADS)

    Quinlan, F.; Fortier, T. M.; Jiang, H.; Hati, A.; Nelson, C.; Fu, Y.; Campbell, J. C.; Diddams, S. A.

    2013-04-01

    Photocurrent shot noise represents the fundamental quantum limit for amplitude, phase and timing measurements of optical signals. It is generally assumed that non-classical states of light must be employed to alter the standard, time-invariant shot noise detection limit. However, in the detection of periodic signals, correlations in the shot noise spectrum can impact the quantum limit of detection. Here, we show how these correlations can be exploited to improve shot noise-limited optical pulse timing measurements by several orders of magnitude. This has allowed us to realize a photodetected pulse train timing noise floor at an unprecedented 25 zs Hz-1/2 (corresponding phase noise of -179 dBc Hz-1 on a 10 GHz carrier), ~5 dB below the level predicted by the accepted time-invariant shot noise behaviour. This new understanding of the shot noise of time-varying signals can be used to greatly improve photonic systems, affecting a wide range of communication, navigation and precision measurement applications.

  10. Ultrashort pulse lasers applied to propulsion/control in space- and atmospheric-flight

    NASA Astrophysics Data System (ADS)

    Kremeyer, Kevin

    2008-05-01

    An impulse measurement device and analysis package was conceived, designed, constructed, tested, and demonstrated to be capable of: measuring nanoNewton-seconds to milliNewton-seconds of impulse due to laser-ablation; being transported as carry-on baggage; set-up and tear-down times of less than an hour; target exchange times of less than two minutes (targets can be ablated at multiple positions for thousands of shots); measurements in air and in vacuum; error of just a few percent; repeatability over a wide range of potential systematic error sources; and time between measurements, including ring-down and analysis, of less than 30 seconds. The instrument consists of a cantilever (i.e. leaf spring), whose time-dependent displacement/oscillation is measured and analyzed to determine the impulse imparted by a laser pulse to a target. These shapes are readily/commercially available, and any target material can be used, provided it can be fashioned in the form of a cantilever, or as a coating/film/tape, suitable for mounting on a cantilever of known geometry. The instrument was calibrated both statically and dynamically, and measurements were performed on brass, steel, and Aluminum, using laser pulses of ~7ns, ~500ps, and ~500fs. The results agree well with those published in the literature, with surface effects, atmosphere, and pre-/post-pulses demonstrating interesting effects and indicating areas for further study. In addition to exploring space-propulsion applications, measurements were performed to explore the strong beneficial effects of depositing lines of energy ahead of supersonic and hypersonic vehicles. This deposition creates a low-density channel, through which a vehicle can travel with dramatically reduced drag. Temperature and pressure are both also reduced on the front surfaces of the vehicle, while density and pressure are increased at the vehicle base. When applied off-center, this technique can be used to control the vehicle, employing the entire

  11. Ultrashort Dephasing Time Measurements in Nile Blue Polymer Films

    NASA Astrophysics Data System (ADS)

    Schwendiman, Julie J.; Grossman, Carl

    1998-03-01

    Ultrafast optical dephasing measurements were performed on thin films of the oxazine dye Nile Blue in poly-[vinyl alcohol] (PVOH). The experimental technique used two beam, time delayed degenerate four wave mixing (DFWM) with incoherent light.(T. Kobayashi, A. Terasaki, T. Hattori and K. Kurokawa, Appl. Phys. B 47, 107 (1988).) Under the conditions that the sample was at relatively high temperatures (between 200=B0K and room temperature) and the measurements were made on the blue side of the Nile Blue inhomogeneous distribution, small time delay oscillations in the were observed. A time delay period was measured at 1.96 +/- .07 fs, which corresponds to the central period of the incoherent light source (centered at 575 nm with a period of 1.92 fs). A comparison between the measured oscillation depth and a numerical simulation of the DFWM scattered intensity yields an estimate of a phase relaxation time between 2 and 3 femtoseconds. This technique offers a new method of measuring femtosecond dephasing times with applications to samples of broad homogeneous linewidths, at high temperatures or in highly interacting environments. The depth of the oscillation decreased with lower temperature and completely disappeared below T=3D100=B0K. The temperature dependence of this effect is currently under investigation.

  12. On the role of terahertz field acceleration and beaming of surface plasmon generated ultrashort electron pulses

    SciTech Connect

    Greig, S. R. Elezzabi, A. Y.

    2014-07-28

    A mechanism for control of the energy and pitch angle of surface plasmon accelerated electron pulses is proposed. Electrons generated via multi-photon absorption in a silver film on a glass prism are ponderomotively accelerated in the surface plasmon field excited by a 30 fs, 800 nm optical pulse. Through introduction of a single-cycle terahertz (THz) pulse, the energy spectrum and trajectory of the generated electron pulse can be controlled via the THz field strength. Generated electron pulses achieve peak kinetic energies up to 1.56 keV, while utilizing an incident optical field strength five times less than comparable plasmon accelerated electron pulses. These results demonstrate that THz pulses can be utilized to achieve tunable, high energy, trajectory controlled electron pulses necessary for various applications that require ultrafast electron pulse manipulation.

  13. The Maria-Goeppert-Mayer Award Lecture: The Science of Ultrashort Pulse Generation, in the Visible and X-Ray Regions of the Spectrum

    NASA Astrophysics Data System (ADS)

    Murnane, Margaret M.

    1997-04-01

    Ultrashort x-ray pulses give researchers a new window through which to view the natural world, with the ability to spatially and temporally resolve processes basic to material and chemical systems. In the 1990's, there has been a revolution in the technology of laser sources, resulting in the ability to simply and reliably produce light pulses as short as 3 optical cycles in duration, both in the visible and the x-ray region of the spectrum. Also, powerful new techniques to obtain accurate pictures of the exact shape of these ultrashort light pulses have been developed, which are revolutionizing the way we think about and use light. Finally, using harmonic techniques to up-convert visible light into the x-ray region, we can generate coherent and tunable light below 5 nm, with unprecedented short duration (3-10 fs).

  14. Time-resolved microscopy reveals the driving mechanism of particle formation during ultrashort pulse laser ablation of dentin-like ivory

    NASA Astrophysics Data System (ADS)

    Domke, Matthias; Gavrilova, Anna; Rapp, Stephan; Frentzen, Matthias; Meister, Joerg; Huber, Heinz P.

    2015-07-01

    In dental health care, the application of ultrashort laser pulses enables dental tissue ablation free from thermal side effects, such as melting and cracking. However, these laser types create undesired micro- and nanoparticles, which might cause a health risk for the patient or surgeon. The aim of this study was to investigate the driving mechanisms of micro- and nanoparticle formation during ultrashort pulse laser ablation of dental tissue. Time-resolved microscopy was chosen to observe the ablation dynamics of mammoth ivory after irradiation with 660 fs laser pulses. The results suggest that nanoparticles might arise in the excited region. The thermal expansion of the excited material induces high pressure in the surrounding bulk tissue, generating a pressure wave. The rarefaction wave behind this pressure wave causes spallation, leading to ejection of microparticles.

  15. Time-resolved microscopy reveals the driving mechanism of particle formation during ultrashort pulse laser ablation of dentin-like ivory.

    PubMed

    Domke, Matthias; Gavrilova, Anna; Rapp, Stephan; Frentzen, Matthias; Meister, Joerg; Huber, Heinz P

    2015-07-01

    In dental health care, the application of ultrashort laser pulses enables dental tissue ablation free from thermal side effects, such as melting and cracking. However, these laser types create undesired micro- and nanoparticles, which might cause a health risk for the patient or surgeon. The aim of this study was to investigate the driving mechanisms of micro- and nanoparticle formation during ultrashort pulse laser ablation of dental tissue. Time-resolved microscopy was chosen to observe the ablation dynamics of mammoth ivory after irradiation with 660 fs laser pulses. The results suggest that nanoparticles might arise in the excited region. The thermal expansion of the excited material induces high pressure in the surrounding bulk tissue, generating a pressure wave. The rarefaction wave behind this pressure wave causes spallation, leading to ejection of microparticles. PMID:26172613

  16. Ultrashort-Pulse Lasers Treating the Crystalline Lens: Will They Cause Vision-Threatening Cataract? (An American Ophthalmological Society Thesis)

    PubMed Central

    Krueger, Ronald R.; Uy, Harvey; McDonald, Jared; Edwards, Keith

    2012-01-01

    Purpose: To demonstrate that ultrashort-pulse laser treatment in the crystalline lens does not form a focal, progressive, or vision-threatening cataract. Methods: An Nd:vanadate picosecond laser (10 ps) with prototype delivery system was used. Primates: 11 rhesus monkey eyes were prospectively treated at the University of Wisconsin (energy 25–45 μJ/pulse and 2.0–11.3M pulses per lens). Analysis of lens clarity and fundus imaging was assessed postoperatively for up to 4½ years (5 eyes). Humans: 80 presbyopic patients were prospectively treated in one eye at the Asian Eye Institute in the Philippines (energy 10 μJ/pulse and 0.45–1.45M pulses per lens). Analysis of lens clarity, best-corrected visual acuity, and subjective symptoms was performed at 1 month, prior to elective lens extraction. Results: Bubbles were immediately seen, with resolution within the first 24 to 48 hours. Afterwards, the laser pattern could be seen with faint, noncoalescing, pinpoint micro-opacities in both primate and human eyes. In primates, long-term follow-up at 4½ years showed no focal or progressive cataract, except in 2 eyes with preexisting cataract. In humans, <25% of patients with central sparing (0.75 and 1.0 mm radius) lost 2 or more lines of best spectacle-corrected visual acuity at 1 month, and >70% reported acceptable or better distance vision and no or mild symptoms. Meanwhile, >70% without sparing (0 and 0.5 mm radius) lost 2 or more lines, and most reported poor or severe vision and symptoms. Conclusions: Focal, progressive, and vision-threatening cataracts can be avoided by lowering the laser energy, avoiding prior cataract, and sparing the center of the lens. PMID:23818739

  17. Amplification of ultrashort pulses with Nd:glass amplifiers pumped by alexandrite free running laser

    SciTech Connect

    Mourou, G.A.; Squier, J.; Coe, J.S.; Harter, D.J.

    1993-08-10

    A method is described of producing an ultra-high peak power pulse, the method comprising the steps of: receiving a short optical pulse having a predetermined duration from an optical oscillator; stretching in time the short optical pulse by a factor of approximately between 100 and 10,000 to produce a timestretched optical pulse to be amplified; amplifying the time-stretched optical pulse in a solid state amplifying media, said step of amplifying additionally including the step of combining the time-stretched optical pulse with an optical energy generated by a laser used to pump the solid-state amplifying media; and compressing in time the amplified time-stretched optical pulse, whereby the amplitude of the resulting amplified time-stretched compressed optical pulse is increased.

  18. Numerical simulations of ultrasimple ultrashortlaser-pulse measurement.

    PubMed

    Liu, Xuan; Trebino, Rick; Smith, Arlee V

    2007-04-16

    We numerically simulate the performance of the ultrasimple frequency-resolved-optical-gating (FROG) technique, GRENOUILLE, for measuring ultrashort laser pulses. While simple in practice, GRENOUILLE has many theoretical subtleties because it involves the second-harmonic generation of relatively tightly focused and broadband pulses. In addition, these processes occur in a thick crystal, in which the phase-matching bandwidth is deliberately made narrow compared to the pulse bandwidth. In these simulations, we include all sum-frequency-generation processes, both collinear and noncollinear. We also include dispersion using the Sellmeier equation for the crystal BBO. Working in the frequency domain, we compute the GRENOUILLE trace for practical-and impractical- examples and show that accurate measurements are easily obtained for properly designed devices. PMID:19532705

  19. An ultrashort pulse ultra-violet radiation undulator source driven by a laser plasma wakefield accelerator

    SciTech Connect

    Anania, M. P.; Brunetti, E.; Wiggins, S. M.; Grant, D. W.; Welsh, G. H.; Issac, R. C.; Cipiccia, S.; Shanks, R. P.; Manahan, G. G.; Aniculaesei, C.; Jaroszynski, D. A.; Geer, S. B. van der; Loos, M. J. de; Poole, M. W.; Shepherd, B. J. A.; Clarke, J. A.; Gillespie, W. A.; MacLeod, A. M.

    2014-06-30

    Narrow band undulator radiation tuneable over the wavelength range of 150–260 nm has been produced by short electron bunches from a 2 mm long laser plasma wakefield accelerator based on a 20 TW femtosecond laser system. The number of photons measured is up to 9 × 10{sup 6} per shot for a 100 period undulator, with a mean peak brilliance of 1 × 10{sup 18} photons/s/mrad{sup 2}/mm{sup 2}/0.1% bandwidth. Simulations estimate that the driving electron bunch r.m.s. duration is as short as 3 fs when the electron beam has energy of 120–130 MeV with the radiation pulse duration in the range of 50–100 fs.

  20. Oxygen-assisted multipass cutting of carbon fiber reinforced plastics with ultra-short laser pulses

    SciTech Connect

    Kononenko, T. V.; Komlenok, M. S.; Konov, V. I.; Freitag, C.; Onuseit, V.; Weber, R.; Graf, T.

    2014-03-14

    Deep multipass cutting of bidirectional and unidirectional carbon fiber reinforced plastics (CFRP) with picosecond laser pulses was investigated in different static atmospheres as well as with the assistance of an oxygen or nitrogen gas flow. The ablation rate was determined as a function of the kerf depth and the resulting heat affected zone was measured. An assisting oxygen gas flow is found to significantly increase the cutting productivity, but only in deep kerfs where the diminished evaporative ablation due to the reduced laser fluence reaching the bottom of the kerf does not dominate the contribution of reactive etching anymore. Oxygen-supported cutting was shown to also solve the problem that occurs when cutting the CFRP parallel to the fiber orientation where a strong deformation and widening of the kerf, which temporarily slows down the process speed, is revealed to be typical for processing in standard air atmospheres.

  1. Internal-conversion process in superintense ultrashort x-ray pulses

    SciTech Connect

    Kis, Daniel; Kalman, Peter; Keszthelyi, Tamas; Szivos, Janos

    2010-01-15

    The electron-nucleus interaction in a super-intense few-cycle x-ray pulse is investigated. The super-intense few-cycle x-ray pulse-induced internal conversion (IC) process is discussed in detail. The x-ray laser-pulse induced IC coefficient is calculated, and in particular, it is derived in the case of a pulse of Gaussian shape and for a bound-free electron transition. The IC coefficient of the IC process induced by a super-intense few-cycle soft-x-ray laser pulse in the case of the {sup 99m}Tc isomer is determined numerically. The results obtained for the IC coefficient show significant carrier angular frequency, carrier-envelope phase, and pulse-length dependencies. The infinite pulse-length limit and experimental aspects are also discussed.

  2. Optical control of filamentation-induced damage to DNA by intense, ultrashort, near-infrared laser pulses

    NASA Astrophysics Data System (ADS)

    Dharmadhikari, J. A.; Dharmadhikari, A. K.; Kasuba, K. C.; Bharambe, H.; D’Souza, J. S.; Rathod, K. D.; Mathur, D.

    2016-06-01

    We report on damage to DNA in an aqueous medium induced by ultrashort pulses of intense laser light of 800 nm wavelength. Focusing of such pulses, using lenses of various focal lengths, induces plasma formation within the aqueous medium. Such plasma can have a spatial extent that is far in excess of the Rayleigh range. In the case of water, the resulting ionization and dissociation gives rise to in situ generation of low-energy electrons and OH-radicals. Interactions of these with plasmid DNA produce nicks in the DNA backbone: single strand breaks (SSBs) are induced as are, at higher laser intensities, double strand breaks (DSBs). Under physiological conditions, the latter are not readily amenable to repair. Systematic quantification of SSBs and DSBs at different values of incident laser energy and under different external focusing conditions reveals that damage occurs in two distinct regimes. Numerical aperture is the experimental handle that delineates the two regimes, permitting simple optical control over the extent of DNA damage.

  3. Optical control of filamentation-induced damage to DNA by intense, ultrashort, near-infrared laser pulses.

    PubMed

    Dharmadhikari, J A; Dharmadhikari, A K; Kasuba, K C; Bharambe, H; D'Souza, J S; Rathod, K D; Mathur, D

    2016-01-01

    We report on damage to DNA in an aqueous medium induced by ultrashort pulses of intense laser light of 800 nm wavelength. Focusing of such pulses, using lenses of various focal lengths, induces plasma formation within the aqueous medium. Such plasma can have a spatial extent that is far in excess of the Rayleigh range. In the case of water, the resulting ionization and dissociation gives rise to in situ generation of low-energy electrons and OH-radicals. Interactions of these with plasmid DNA produce nicks in the DNA backbone: single strand breaks (SSBs) are induced as are, at higher laser intensities, double strand breaks (DSBs). Under physiological conditions, the latter are not readily amenable to repair. Systematic quantification of SSBs and DSBs at different values of incident laser energy and under different external focusing conditions reveals that damage occurs in two distinct regimes. Numerical aperture is the experimental handle that delineates the two regimes, permitting simple optical control over the extent of DNA damage. PMID:27279565

  4. Optical control of filamentation-induced damage to DNA by intense, ultrashort, near-infrared laser pulses

    PubMed Central

    Dharmadhikari, J. A.; Dharmadhikari, A. K.; Kasuba, K. C.; Bharambe, H.; D’Souza, J. S.; Rathod, K. D.; Mathur, D.

    2016-01-01

    We report on damage to DNA in an aqueous medium induced by ultrashort pulses of intense laser light of 800 nm wavelength. Focusing of such pulses, using lenses of various focal lengths, induces plasma formation within the aqueous medium. Such plasma can have a spatial extent that is far in excess of the Rayleigh range. In the case of water, the resulting ionization and dissociation gives rise to in situ generation of low-energy electrons and OH-radicals. Interactions of these with plasmid DNA produce nicks in the DNA backbone: single strand breaks (SSBs) are induced as are, at higher laser intensities, double strand breaks (DSBs). Under physiological conditions, the latter are not readily amenable to repair. Systematic quantification of SSBs and DSBs at different values of incident laser energy and under different external focusing conditions reveals that damage occurs in two distinct regimes. Numerical aperture is the experimental handle that delineates the two regimes, permitting simple optical control over the extent of DNA damage. PMID:27279565

  5. Combined lineage mapping and gene expression profiling of embryonic brain patterning using ultrashort pulse microscopy and image registration

    NASA Astrophysics Data System (ADS)

    Gibbs, Holly C.; Dodson, Colin R.; Bai, Yuqiang; Lekven, Arne C.; Yeh, Alvin T.

    2014-12-01

    During embryogenesis, presumptive brain compartments are patterned by dynamic networks of gene expression. The spatiotemporal dynamics of these networks, however, have not been characterized with sufficient resolution for us to understand the regulatory logic resulting in morphogenetic cellular behaviors that give the brain its shape. We have developed a new, integrated approach using ultrashort pulse microscopy [a high-resolution, two-photon fluorescence (2PF)-optical coherence microscopy (OCM) platform using 10-fs pulses] and image registration to study brain patterning and morphogenesis in zebrafish embryos. As a demonstration, we used time-lapse 2PF to capture midbrain-hindbrain boundary morphogenesis and a wnt1 lineage map from embryos during brain segmentation. We then performed in situ hybridization to deposit NBT/BCIP, where wnt1 remained actively expressed, and reimaged the embryos with combined 2PF-OCM. When we merged these datasets using morphological landmark registration, we found that the mechanism of boundary formation differs along the dorsoventral axis. Dorsally, boundary sharpening is dominated by changes in gene expression, while ventrally, sharpening may be accomplished by lineage sorting. We conclude that the integrated visualization of lineage reporter and gene expression domains simultaneously with brain morphology will be useful for understanding how changes in gene expression give rise to proper brain compartmentalization and structure.

  6. Ultrashort-Pulse Child-Langmuir Law in the Quantum and Relativistic Regimes

    SciTech Connect

    Ang, L. K.; Zhang, P.

    2007-04-20

    This Letter presents a consistent quantum and relativistic model of short-pulse Child-Langmuir (CL) law, of which the pulse length {tau} is less than the electron transit time in a gap of spacing D and voltage V. The classical value of the short-pulse CL law is enhanced by a large factor due to quantum effects when the pulse length and the size of the beam are, respectively, in femtosecond duration and nanometer scale. At high voltage larger than the electron rest mass, relativistic effects will suppress the enhancement of short-pulse CL law, which is confirmed by particle-in-cell simulation. When the pulse length is much shorter than the gap transit time, the current density is proportional to V, and to the inverse power of D and {tau}.

  7. Spectral characteristics of ultra-short laser pulses in plasma amplifiers

    SciTech Connect

    Riconda, C.; Weber, S.; Lancia, L.; Marquès, J.-R.; Fuchs, J.; Mourou, G. A.

    2013-08-15

    Amplification of laser pulses based on the backscattering process in plasmas can be performed using either the response of an electron plasma wave or an ion-acoustic wave. However, if the pulse durations become very short and the natural spread in frequency a substantial amount of the frequency itself, the Raman and Brillouin processes start to mix. Kinetic simulations show the transition from a pure amplification regime, in this case strong-coupling Brillouin, to a regime where a considerable downshift of the frequency of the amplified pulse takes place. It is conjectured that in the case of very short pulses, multi-modes are excited which contribute to the amplification process.

  8. Direct amplification of ultrashort pulses in μ-pulling-down Yb:YAG single crystal fibers.

    PubMed

    Zaouter, Yoann; Martial, Igor; Aubry, Nicolas; Didierjean, Julien; Hönninger, Clemens; Mottay, Eric; Druon, Frederic; Georges, Patrick; Balembois, François

    2011-03-01

    We demonstrated that Yb:YAG single crystal fibers have a strong potential for the amplification of femtosecond pulses. Seeded by 230 fs pulses with an average power of 400 mW at 30 MHz delivered by a passively mode-locked Yb:KYW oscillator, the system produced 330 fs pulses with an average power of 12 W. This is the shortest pulse duration ever produced by an Yb:YAG amplifier. The gain in the single crystal fiber reached a value as high as 30 in a simple double-pass configuration. PMID:21368970

  9. Ultrashort light pulses generated from modulation instability: background removal and soliton content

    NASA Astrophysics Data System (ADS)

    Mahnke, Christoph; Mitschke, Fedor

    2014-07-01

    Modulation instability can be used to convert a continuous light wave into a train of pulses on a constant background. It is a longstanding discussion whether these pulses can be converted into solitons. We clarify the situation by using a more general mathematical context, invoking the Akhmediev breather, Peregrine soliton and Kuznetsov-Ma soliton solutions of the wave equation, and suggest the use of a Mach-Zehnder interferometer to remove the background. Expressions for the pulse widths and peak powers thus obtained are presented, and their soliton content is determined. It turns out that more than 95 % of each pulse's energy can be converted to a soliton.

  10. Numerical simulations of ultrashort laser pulse multifilamentation in fused silica: plasma channels statistics

    NASA Astrophysics Data System (ADS)

    Geints, Yu E.; Zemlyanov, A. A.

    2016-01-01

    The regime of multiple filamentation of gigawatt-power femtosecond laser pulses in fused silica bars is theoretically investigated. Numerical simulations are used to analyze the fine spatial structure of the plasma region formed due to photoionization of silica and accompanying pulse filamentation. The dependence of the number, spatial position, and length of different generations of plasma channels on the energy and focusing conditions of the optical pulse is studied. The role of pulse sequential refocusing in the formation of the plasma region is discussed.

  11. Compression of An Ultrashort Laser Pulse via Self-Phase Modulation in An Argon Channel

    SciTech Connect

    Kudo, Masashi; Higashiguchi, Takeshi; Yugami, Noboru

    2009-01-22

    Compression and splitting of the optical laser pulse due to multiple filamentation in an argon gas-filled channel was observed. A 130-140-fs linearly polarized pulse was successfully compressed to less than 60-80 fs with the output energy of a few 10 mJ.

  12. Steady-state propagation of ultrashort optical pulses in semiconductor excitonic medium

    NASA Astrophysics Data System (ADS)

    Talanina, Irina B.

    1996-06-01

    The form-invariant coherent pulse propagation in semiconductors excited at the 1 s -exciton resonance is studied analytically with the reduced semiconductor Maxwell-Bloch equations. The sech-shaped pulse solution for the electric field is presented. The effects of Coulomb interactions between excitons and spatial dispersion are discussed. Applications to CdS and CdSe crystals are made.

  13. Kinetic study of terahertz generation based on the interaction of two-color ultra-short laser pulses with molecular hydrogen gas

    NASA Astrophysics Data System (ADS)

    Soltani Gishini, M. S.; Ganjovi, A.; Saeed, M.

    2016-06-01

    In this work, using a two dimensional particle in cell-Monte Carlo collision simulation scheme, interaction of two-color ultra-short laser pulses with the molecular hydrogen gas (H2) is examined. The operational laser parameters, i.e., its pulse shape, duration, and waist, are changed and, their effects on the density and kinetic energy of generated electrons, THz electric field, intensity, and spectrum are studied. It is seen that the best pulse shape generating the THz signal radiation with the highest intensity is a trapezoidal pulse, and the intensity of generated THz radiation is increased at the higher pulse durations and waists. For all the operational laser parameters, the maximum value of emitted THz signal frequency always remains lower than 5 THz. The intensity of applied laser pulses is taken about 1014 w/cm2, and it is observed that while a small portion of the gaseous media gets ionized, the radiated THz signal is significant.

  14. Limitations of the strong field approximation in ionization of the hydrogen atom by ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Arbó, D. G.; Tőkési, K.; Miraglia, J. E.

    2009-03-01

    We present a theoretical study of the ionization of hydrogen atoms as a result of the interaction with an ultrashort external electric field. Doubly-differential momentum distributions and angular momentum distributions of ejected electrons calculated in the framework of the Coulomb-Volkov and strong field approximations, as well as classical calculations are compared with the exact solution of the time dependent Schr ödinger equation. We show that in the impulsive limit, the Coulomb-Volkov distorted wave theory reproduces the exact solution. The validity of the strong field approximation is probed both classically and quantum mechanically. We found that classical mechanics describes the proper quantum momentum distributions of the ejected electrons right after a sudden momentum transfer, however pronounced the differences at latter stages that arise during the subsequent electron-nucleus interaction. Although the classical calculations reproduce the quantum momentum distributions, it fails to describe properly the angular momentum distributions, even in the limit of strong fields. The origin of this failure can be attributed to the difference between quantum and classical initial spatial distributions.

  15. Energetic electrons and protons generated from the interaction of ultrashort laser pulses with microdroplet plasmas

    SciTech Connect

    Zheng Jun; Sheng Zhengmng; Peng Xiaoy; Zhang Jie

    2005-11-15

    Generation of fast electrons and protons from ultrashort laser interactions with microdroplet plasmas has been simulated by two-dimensional particle-in-cell simulations. At weakly relativistic laser intensities, two jets of hot electrons are found to emit symmetrically in the backward direction when there is preplasma formed around the droplet surface. These electron jets are associated with resonance absorption around the target surface with a spherical geometry. At relativistic laser intensities, electron bunches generated by the laser ponderomotive force separated by a laser period are superimposed to the resonant hot-electron jets. Relevant with the hot-electron emission, energetic protons can be separated into two groups: one with higher energies mainly emits in certain angles within the laser polarization plane and another with lower energies emits nearly isotropically in all directions. The protons in the first group are accelerated by the electrostatic fields induced by the hot-electron jets due to the resonance absorption, while those in the second group are generated by the ambipolar expansion of the microdroplet plasma.

  16. Highlighting the DNA damage response with ultrashort laser pulses in the near infrared and kinetic modeling

    PubMed Central

    Ferrando-May, Elisa; Tomas, Martin; Blumhardt, Philipp; Stöckl, Martin; Fuchs, Matthias; Leitenstorfer, Alfred

    2013-01-01

    Our understanding of the mechanisms governing the response to DNA damage in higher eucaryotes crucially depends on our ability to dissect the temporal and spatial organization of the cellular machinery responsible for maintaining genomic integrity. To achieve this goal, we need experimental tools to inflict DNA lesions with high spatial precision at pre-defined locations, and to visualize the ensuing reactions with adequate temporal resolution. Near-infrared femtosecond laser pulses focused through high-aperture objective lenses of advanced scanning microscopes offer the advantage of inducing DNA damage in a 3D-confined volume of subnuclear dimensions. This high spatial resolution results from the highly non-linear nature of the excitation process. Here we review recent progress based on the increasing availability of widely tunable and user-friendly technology of ultrafast lasers in the near infrared. We present a critical evaluation of this approach for DNA microdamage as compared to the currently prevalent use of UV or VIS laser irradiation, the latter in combination with photosensitizers. Current and future applications in the field of DNA repair and DNA-damage dependent chromatin dynamics are outlined. Finally, we discuss the requirement for proper simulation and quantitative modeling. We focus in particular on approaches to measure the effect of DNA damage on the mobility of nuclear proteins and consider the pros and cons of frequently used analysis models for FRAP and photoactivation and their applicability to non-linear photoperturbation experiments. PMID:23882280

  17. Ultrashort pulse laser interactions with cortical bone tissue for applications in orthopaedic surgery

    NASA Astrophysics Data System (ADS)

    Ashforth, Simon A.; Simpson, M. C.; Bodley, Owen; Oosterbeek, Reece

    2015-03-01

    Using a femtosecond pulsed laser system (pulse width = 100fs, repetition rate = 1kHz, λ = 800nm), ablation threshold studies of freshly culled bovine and ovine cortical bone samples were identified using the diameter regression technique. Using the D2 technique, the ablation threshold was found to lie within a range of 0.83 - 0.96 Jcm-2 and 0.89 - 0.95 Jcm-2 for ovine and bovine cortical bone respectively indicating that laser ablation of bone is irrespective of target species. The relationship between cortical bone tissue removal and the number of applied pulses was explored. By altering the laser spot translation rate, we varied the number of pulses at each point along scribed linear cuts. Optical Coherence Tomography (OCT) and PDMS casting indicates that cut depth is linearly dependent on the number of pulses applied to the tissue, irrespective of donor species. For single pulse ablation of ovine and bovine cortical bone, we determined that the ablation rates were 0.41 - 0.75 μm per pulse and 0.28 - 0.90 μm per pulse when pulses of fluences in the range 0.52 - 2.63 Jcm-2 were applied to ovine and bovine cortical bone tissue, respectively. Structural analysis of the ablation features using environmental scanning electron microscopy and optical microscopy were utilized to assess the ablation features and identify signs of damage to surrounding tissue. We observed no structural indications of thermal shockwave cracking, molten debris deposition or charring of the tissue whilst leaving hydroxyapatite crystal structure intact.

  18. On the Theory of High-Power Ultrashort Pulse Propagation in Raman-Active Media

    NASA Technical Reports Server (NTRS)

    Belenov, E. M.; Isakov, V. A.; Kanavin, A. P.; Smetanin, I. V.

    1996-01-01

    The propagation of an intense femtosecond pulse in a Raman-active medium is analyzed. An analytic solution which describes in explicit form the evolution of the light pulse is derived. The field of an intense light wave undergoes a substantial transformation as the wave propagates through the medium. The nature of this transformation can change over time scales comparable to the period of the optical oscillations. As a result, the pulse of sufficiently high energy divides into stretched and compressed domains where the field decreases and increases respectively.

  19. Photoionization of monocrystalline CVD diamond irradiated with ultrashort intense laser pulse

    NASA Astrophysics Data System (ADS)

    Lagomarsino, Stefano; Sciortino, Silvio; Obreshkov, Boyan; Apostolova, Tzveta; Corsi, Chiara; Bellini, Marco; Berdermann, Eleni; Schmidt, Christian J.

    2016-02-01

    Direct laser writing of conductive paths in synthetic diamond is of interest for implementation in radiation detection and clinical dosimetry. Unraveling the microscopic processes involved in laser irradiation of diamond below and close to the graphitization threshold under the same conditions as the experimental procedure used to produce three-dimensional devices is necessary to tune the laser parameters to optimal results. To this purpose a transient currents technique has been used to measure laser-induced current signals in monocrystalline diamond detectors in a wide range of laser intensities and at different bias voltages. The current transients vs time and the overall charge collected have been compared with theoretical simulations of the carrier dynamics along the duration and after the conclusion of the 30 fs laser pulse. The generated charge has been derived from the collected charge by evaluation of the lifetime of the carriers. The plasma volume has also been evaluated by measuring the modified region. The theoretical simulation has been implemented in the framework of the empirical pseudopotential method extended to include time-dependent couplings of valence electrons to the radiation field. The simulation, in the low-intensity regime, I ˜1 TW /cm2 , predicts substantial deviation from the traditional multiphoton ionization, due to nonperturbative effects involving electrons from degenerate valence bands. For strong field with intensity of about 50 TW /cm2, nonadiabatic effects of electron-hole pair excitation become prominent with high carrier densities eventually causing the optical breakdown of diamond. The comparison of theoretical prediction with experimental data of laser-generated charge vs laser energy density yields a good quantitative agreement over six orders of magnitude. At the highest intensities the change of slope in the trend is explained taking into account the dependence of the optical parameters and the carrier mobility on plasma

  20. Mode-Locked Ultrashort Pulse Generation from On-Chip Normal Dispersion Microresonators

    NASA Astrophysics Data System (ADS)

    Huang, S.-W.; Zhou, H.; Yang, J.; McMillan, J. F.; Matsko, A.; Yu, M.; Kwong, D.-L.; Maleki, L.; Wong, C. W.

    2015-02-01

    We describe generation of stable mode-locked pulse trains from on-chip normal dispersion microresonators. The excitation of hyperparametric oscillation is facilitated by the local dispersion disruptions induced by mode interactions. The system is then driven from hyperparametric oscillation to the mode-locked state with over 200 nm spectral width by controlled pump power and detuning. With the continuous-wave-driven nonlinearity, the pulses sit on a pedestal, akin to a cavity soliton. We identify the importance of pump detuning and wavelength-dependent quality factors in stabilizing and shaping the pulse structure, to achieve a single pulse inside the cavity. We examine the mode-locking dynamics by numerically solving the master equation and provide analytic solutions under appropriate approximations.

  1. Generation of ultra-short THz pulses in new optical nonlinear materials based on organic polymers

    NASA Astrophysics Data System (ADS)

    Mikerin, S. L.; Plekhanov, A. I.; Simanchuk, A. V.; Yakimanskii, A. V.

    2016-07-01

    Using the method of optical rectification of femtosecond laser pulses, we report the generation of short (a few field cycles) terahertz pulses in the samples of films based on polyimides with covalently bound chromophore molecules of DR type. The spectral width of the produced pulses is limited by the pump pulse duration. The quadratic nonlinear optical properties are imparted to the films in the process of their fabrication by orienting the chromophore molecules in the external electric field of the applied electrodes having an original configuration. The samples are compared with the ZnTe crystal. Using the methods of coherent spectroscopy, their transmission and refractive index dispersion spectra are investigated in the frequency range 0.5 – 2.6 THz. The studied polymer composition is promising for the application in coherent spectrometers both for increasing the working spectral range without dips and for improving the spatial resolution in the near-field terahertz spectroscopy.

  2. Parametric amplification and compression to ultrashort pulse duration of resonant linear waves

    NASA Astrophysics Data System (ADS)

    Aguergaray, C.; Andersen, T. V.; Schimpf, D. N.; Schmidt, O.; Rothhardt, J.; Schreiber, T.; Limpert, J.; Cormier, E.; Tünnermann, A.

    2007-04-01

    We report on an optical parametric amplification system which is pumped and seeded by fiber generated laser radiation. Due to its low broadening threshold, high spatial beam quality and high stability, the fiber based broad bandwidth signal generation is a promising alternative to white light generation in bulky glass or sapphire plates. We demonstrate a novel and successful signal engineering implemented in a setup for parametric amplification and subsequent recompression of resonant linear waves resulting from soliton fission in a highly nonlinear photonic crystal fiber. The applied pump source is a high repetition rate ytterbium-doped fiber chirped pulse amplification system. The presented approach results in the generation of ~50 fs pulses at MHz repetition rate. The potential of generating even shorter pulse duration and higher pulse energies will be discussed.

  3. Controlling the formation of excited neutral D* fragments of D2 using intense ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Feizollah, Peyman; Berry, Ben; Severt, T.; Jochim, Bethany; Zohrabi, M.; Kanaka Raju, P.; Rajput, Jyoti; Carnes, K. D.; Esry, B. D.; Ben-Itzhak, I.

    2016-05-01

    Excited neutral D* fragments (n >> 1) are produced by the interaction of strong-field laser pulses with D2 molecules. In this work, we focus on the formation of low kinetic energy release (KER) D* fragments, which are relatively unstudied, using NIR (800-nm) and UV (400-nm) laser pulses. The KER spectrum is found to be very sensitive to the laser parameters, including laser chirp. By changing the chirp of the UV laser pulses, two separate low-KER peaks are generated instead of a single peak. Moreover, the ratio between these peaks can be controlled with the chirp. Similarly, by chirping the NIR pulses, the low-KER peak is attenuated and shifted to lower energy. This work was supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. Department of Energy. BJ was also supported in part by DOE-SCGF (DE-AC05-06OR23100).

  4. 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

  5. Accelerating protons to therapeutic energies with ultraintense, ultraclean, and ultrashort laser pulses

    SciTech Connect

    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

    2008-05-15

    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 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 {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.

  6. Harmonizing HeLa cell cytoskeleton behavior by multi-Ti oxide phased nanostructure synthesized through ultrashort pulsed laser

    PubMed Central

    Chinnakkannu Vijayakumar, Chandramouli; Venkatakrishnan, Krishnan; Tan, Bo

    2015-01-01

    Knowledge about cancer cell behavior on heterogeneous nanostructures is relevant for developing a distinct biomaterial that can actuate cancer cells. In this manuscript, we have demonstrated a harmonized approach of forming multi Ti-oxide phases in a nanostructure (MTOP nanostructure) for its unique cancer cell controlling behavior.Conventionally, single phases of TiO2 are used for targeted therapy and as drug carrier systems.In this research, we have shown a biomaterial that can control HeLa cells diligently using a combination of TiO, Ti3O and TiO2 phases when compared to fibroblast (NIH3T3) cells.MTOP-nanostructures are generated by varying the ionization energy in the vapor plume of the ultrashort pulse laser; this interaction with the material allows accurate tuning and composition of phases within the nanostructure. In addition, the lattice spacing of MTOP-nanostructures was analyzed as shown by HR-TEM investigations. An FESEM investigation of MTOP-nanostructures revealed a greater reduction of HeLa cells relative to fibroblast cells. Altered cell adhesion was followed by modulation of HeLa cell architecture with a significant reduction of actin stress fibers.The intricate combination of MTOP-nanostructures renders a biomaterial that can precisely alter HeLa cell but not fibroblast cell behavior, filling a void in the research for a biomaterial to modulate cancer cell behavior. PMID:26469886

  7. Harmonizing HeLa cell cytoskeleton behavior by multi-Ti oxide phased nanostructure synthesized through ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Chinnakkannu Vijayakumar, Chandramouli; Venkatakrishnan, Krishnan; Tan, Bo

    2015-10-01

    Knowledge about cancer cell behavior on heterogeneous nanostructures is relevant for developing a distinct biomaterial that can actuate cancer cells. In this manuscript, we have demonstrated a harmonized approach of forming multi Ti-oxide phases in a nanostructure (MTOP nanostructure) for its unique cancer cell controlling behavior.Conventionally, single phases of TiO2 are used for targeted therapy and as drug carrier systems.In this research, we have shown a biomaterial that can control HeLa cells diligently using a combination of TiO, Ti3O and TiO2 phases when compared to fibroblast (NIH3T3) cells.MTOP-nanostructures are generated by varying the ionization energy in the vapor plume of the ultrashort pulse laser; this interaction with the material allows accurate tuning and composition of phases within the nanostructure. In addition, the lattice spacing of MTOP-nanostructures was analyzed as shown by HR-TEM investigations. An FESEM investigation of MTOP-nanostructures revealed a greater reduction of HeLa cells relative to fibroblast cells. Altered cell adhesion was followed by modulation of HeLa cell architecture with a significant reduction of actin stress fibers.The intricate combination of MTOP-nanostructures renders a biomaterial that can precisely alter HeLa cell but not fibroblast cell behavior, filling a void in the research for a biomaterial to modulate cancer cell behavior.

  8. Modeling of ultrashort pulsed laser irradiation in the cornea based on parabolic and hyperbolic heat equations using electrical analogy

    NASA Astrophysics Data System (ADS)

    Gheitaghy, A. M.; Takabi, B.; Alizadeh, M.

    2014-03-01

    Hyperbolic and parabolic heat equations are formulated to study a nonperfused homogeneous transparent cornea irradiated by high power and ultrashort pulsed laser in the Laser Thermo Keratoplasty (LTK) surgery. Energy absorption inside the cornea is modeled using the Beer-Lambert law that is incorporated as an exponentially decaying heat source. The hyperbolic and parabolic bioheat models of the tissue were solved by exploiting the mathematical analogy between thermal and electrical systems, by using robust circuit simulation program called Hspice to get the solutions of simultaneous RLC and RC transmission line networks. This method can be used to rapidly calculate the temperature in laser-irradiated tissue at time and space domain. It is found that internal energy gained from the irradiated field results in a rapid rise of temperature in the cornea surface during the early heating period, while the hyperbolic wave model predicts a higher temperature rise than the classical heat diffusion model. In addition, this paper investigates and examines the effect of some critical parameters such as relaxation time, convection coefficient, radiation, tear evaporation and variable thermal conductivity of cornea. Accordingly, it is found that a better accordance between hyperbolic and parabolic models will be achieved by time.

  9. Electronic response of graphene to an ultrashort intense terahertz radiation pulse

    NASA Astrophysics Data System (ADS)

    Ishikawa, Kenichi L.

    2013-05-01

    We have recently reported a study (Ishikawa 2010 Phys. Rev. B 82 201402) on a nonlinear optical response of graphene to a normally incident terahertz radiation pulse within the massless Dirac fermion (MDF) picture, where we have derived physically transparent graphene Bloch equations (GBE). Here we extend it to the tight-binding (TB) model and oblique incidence. The derived equations indicate that interband transitions are governed by the temporal variation of the spinor phase along the electron path in the momentum space and predominantly take place when the electron passes near the Dirac point. At normal incidence, the equations for electron dynamics within the TB model can be cast into the same form of GBE as for the MDF model. At oblique incidence, the equations automatically incorporate photon drag and satisfy the continuity equation for electron density. Single-electron dynamics strongly depend on the model and pulse parameters, but the rapid variations are averaged out after momentum-space integration. Direct current remaining after the pulse is generated in graphene irradiated by an intense monocycle terahertz pulse, even if it is linearly polarized and normally incident. The generated current depends on the carrier-envelope phase, pulse intensity and Fermi energy in a complex manner.

  10. PM2D code simulation of electronic dynamics and electro-magnetic fields generation by ultra-short laser pulses interaction with matter

    SciTech Connect

    Litvinenko, I. A.; Lykov, V. A.

    1997-04-15

    The results of numerical simulation of fast electrons motion and generated electro-magnetic fields at the picosecond pulse laser interaction with flat target are presented. The calculations were performed with PM2D code, where relativistic equation of electron motion joint with Maxwell equations is solved by particle method in cells. The efficiency of fast electrons energy conversion to the transverse electromagnetic wave of picosecond duration can reach the value 10{sup -4} for the intensity of ultrashort laser pulse at the target 10{sup 16}-10{sup 17} W/cm{sup 2}.

  11. Control of Electron Excitation and Localization in the Dissociation of H{sub 2}{sup +} and Its Isotopes Using Two Sequential Ultrashort Laser Pulses

    SciTech Connect

    He Feng; Ruiz, Camilo; Becker, Andreas

    2007-08-24

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

  12. Plasma-induced spectral broadening of high-energy ultrashort laser pulses in a helium-filled multiple-pass cell

    SciTech Connect

    Nurhuda, Muhammad; Suda, Akira; Midorikawa, Katsumi

    2006-09-15

    We investigated the possibility of plasma-induced spectral broadening of high-energy ultrashort laser pulses in a helium-filled multipass cell (MPC) through a series of full numerical simulations of the extended nonlinear Schroedinger equation. It was found that the gas pressure must be set low so that the propagation dynamics can be controlled only by plasma defocusing. Simulations using 100 mJ, 40 fs laser pulses in the MPC, which is 6 m long and has a mirror of 3.1 m radius at each end, showed that if the gas pressure is set within the range of 40-130 Pa, then the relevant spectral broadening can be obtained after five passes, yielding compressed pulses of a 4.7-6.4 fs width. The ratio of the energy of the compressed pulse to the output pulse is found to be within 58-88%.

  13. Enhanced water window x-ray emission from in situ formed carbon clusters irradiated by intense ultra-short laser pulses

    SciTech Connect

    Chakravarty, U.; Rao, B. S.; Arora, V.; Upadhyay, A.; Singhal, H.; Naik, P. A.; Chakera, J. A.; Mukherjee, C.; Gupta, P. D.

    2013-07-29

    Enhanced water window x-ray emission (23–44 Å) from carbon clusters, formed in situ using a pre-pulse, irradiated by intense (I > 10{sup 17} W/cm{sup 2}) ultra-short laser pulse, is demonstrated. An order of magnitude x-ray enhancement over planar graphite target is observed in carbon clusters, formed by a sub-ns pre-pulse, interacting with intense main pulse after a delay. The effect of the delay and the duration of the main pulse is studied for optimizing the x-ray emission in the water window region. This x-ray source has added advantages of being an efficient, high repetition rate, and low debris x-ray source.

  14. Generation of "gigantic" ultra-short microwave pulses based on passive mode-locking effect in electron oscillators with saturable absorber in the feedback loop

    NASA Astrophysics Data System (ADS)

    Ginzburg, N. S.; Denisov, G. G.; Vilkov, M. N.; Zotova, I. V.; Sergeev, A. S.

    2016-05-01

    A periodic train of powerful ultrashort microwave pulses can be generated in electron oscillators with a non-linear saturable absorber installed in the feedback loop. This method of pulse formation resembles the passive mode-locking widely used in laser physics. Nevertheless, there is a specific feature in the mechanism of pulse amplification when consecutive energy extraction from different fractions of a stationary electron beam takes place due to pulse slippage over the beam caused by the difference between the wave group velocity and the electron axial velocity. As a result, the peak power of generated "gigantic" pulses can exceed not only the level of steady-state generation but also, in the optimal case, the power of the driving electron beam.

  15. Plasma Parameter of a Capillary Discharge-Produced Plasma Channel to Guide an Ultrashort Laser Pulse

    SciTech Connect

    Higashiguchi, Takeshi; Terauchi, Hiromitsu; Bai, Jin-xiang; Yugami, Noboru

    2009-01-22

    We have observed the optical guiding of a 100-fs laser pulse with the laser intensity in the range of 10{sup 16} W/cm{sup 2} using a 1.5-cm long capillary discharge-produced plasma channel for compact electron acceleration applications. The optical pulse propagation using the plasma channel is achieved with the electron densities of 10{sup 17}-10{sup 18} cm{sup -3} and the electron temperatures of 0.5-4 eV at a discharge time delay of around 150 ns and a discharge current of 500 A with a pulse duration of 100-150 ns. An energy spectrum of the accelerated electrons from a laser-plasma acceleration scheme showed a peak at 1.3 MeV with a maximum energy tail of 1.6 MeV.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  17. Amplification of ultrashort electromagnetic pulses propagating along quasi-continuous electron beams

    NASA Astrophysics Data System (ADS)

    Baryshev, V. R.; Ginzburg, N. S.; Zotova, I. V.; Sergeev, A. S.; Rozental, R. M.; Yalandin, M. I.

    2009-01-01

    Specific features of amplification of short electromagnetic pulses propagating along steady-state nonequilibrium electron flows with a group velocity differing from the translational velocity of particles are analyzed. It is shown that an amplitude level substantially higher than the saturation level in amplification of quasi-continuous signals can be attained by permanent injection of electrons without initial modulation to one of the pulse fronts. The effective duration of the pulse being amplified is reduced simultaneously. The Cherenkov and undulator interaction mechanisms are considered. Analysis is carried out using a simple 1D model based on the averaged description of the electron-wave interaction, as well as direct numerical simulation based on the KARAT code taking into account the parameters of planned experiments on observation of this effect.

  18. 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

  19. Electron Acceleration and the Propagation of Ultrashort High-Intensity Laser Pulses in Plasmas

    SciTech Connect

    Wang, Xiaofang; Krishnan, Mohan; Saleh, Ned; Wang, Haiwen; Umstadter, Donald

    2000-06-05

    Reported are interactions of high-intensity laser pulses ({lambda}=810 nm and I{<=}3x10{sup 18} W /cm{sup 2} ) with plasmas in a new parameter regime, in which the pulse duration ({tau}=29 fs ) corresponds to 0.6-2.6 plasma periods. Relativistic filamentation is observed to cause laser-beam breakup and scattering of the beam out of the vacuum propagation angle. A beam of megaelectronvolt electrons with divergence angle as small as 1 degree sign is generated in the forward direction, which is correlated to the growth of the relativistic filamentation. Raman scattering, however, is found to be much less than previous long-pulse results. (c) 2000 The American Physical Society.

  20. Laser-induced damage in photopolymers thin films with ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Žukauskas, Albertas; BatavičiÅ«tÄ--, GintarÄ--; Å čiuka, Mindaugas; Melninkaitis, Andrius; Malinauskas, Mangirdas

    2014-05-01

    We characterize laser-induced damage threshold (LIDT) in transparent photopolymers by a sub-ps laser pulses of 515 nm wavelength representing case of high light intensities. Five different photopolymers (SZ2080, OrmoComp, SU-8, PDMS and PMMA) widely used in the laser lithography are investigated. The relationship of the damage threshold and optical band-gap energy of the polymers indicating possible damage mechanism is considered. Incubation model validating damage threshold dependence on the number of laser pulses is studied as well. The obtained characteristic values of LIDT reveal potential of photopolymers and their possible applications in high power laser systems.

  1. Production of Ultrashort FEL XUV Pulses via a Reverse UndulatorTaper

    SciTech Connect

    Fawley, William M.

    2007-10-22

    We adapt the "reverse taper" scheme presented by Saldin etal. (Phys. Rev. ST Accel. Beams, 9, 050702 [2006]) for attosecond pulseproduction to the XUV/soft-xray regime. We find that that GW-level pulsesof a few femtosecond duration or shorter can be produced using electronbeams of quite moderate parameters and undulators of 20-m length orshorter. The output pulse is significantly shifted in wavelength relativeto the main background which permits a further increase in contrast ratiovia simple monochromatization. Moreover, the output pulse has a naturalwavelength chirp that allows further temporal compression, if wanted.Both positive and negative chirps can be produced depending uponthe signof the undulator taper.

  2. Generation of isolated ultra-short attosecond pulses by coherent control of the population of excited states

    NASA Astrophysics Data System (ADS)

    Jooya, Hossein Z.; Li, Peng-Cheng; Liao, Sheng-Lun; Chu, Shih-I.

    2016-01-01

    We present an ab-initio theoretical investigation of the enhancement of ultra-broad super-continuum harmonic spectra by coherently controlling the electron quantum paths of the helium atom and He+ ion. The time-dependent Schrödinger equation is solved by means of the time-dependent generalized pseudo-spectral method, allowing non-uniform and optimal spatial grid discretization and accurate and efficient propagation of the wave function in space and time. The population of the first two low-lying excited states of He+ is selectively controlled by adding low intensity, high frequency laser pulses to a two color mid-infrared laser field. Although the intensity of the added field is weak, its high frequency makes the subsequent ionization probability from excited states become much larger than for the case of many photons (mid-IR filed), even though the intensity is smaller. We found that the intensity of the attosecond pulse generated by superposing a range of synchronized high harmonics is significantly enhanced by 20 orders of magnitude. Similar calculations have been performed for the neutral He atoms. We found that an intense and ultra-short isolated 18 as can be generated directly. To understand the underlying mechanism of such dramatic enhancement and the role of electron quantum paths, we perform wavelet time-frequency transform of high harmonic spectra. The results show that we can selectively control the domination of the two distinct long and short electron trajectories by controlling the population of different excited states.

  3. Mechanisms of amplification of ultrashort electromagnetic pulses in gyrotron traveling wave tube with helically corrugated waveguide

    NASA Astrophysics Data System (ADS)

    Ginzburg, N. S.; Zotova, I. V.; Sergeev, A. S.; Zaslavsky, V. Yu.; Zheleznov, I. V.; Samsonov, S. V.; Mishakin, S. V.

    2015-11-01

    A time-domain self consistent theory of a gyrotron traveling wave tube with a helically corrugated operating waveguide has been developed. Based on this model, the process of short pulse amplification was studied in regimes of grazing and intersection of the dispersion curves of the electromagnetic wave and the electron beam. In the first case, the possibility of amplification without pulse form distortion was demonstrated for the pulse spectrum width of the order of the gain bandwidth. In the second case, when the electrons' axial velocity was smaller than the wave's group velocity, it was shown that the slippage of the incident signal with respect to the electron beam provides feeding of the signal by "fresh" electrons without initial modulation. As a result, the amplitude of the output pulse can exceed the amplitude of its saturated value for the case of the grazing regime, and, for optimal parameters, the peak output power can be even larger than the kinetic power of the electron beam.

  4. Mechanisms of amplification of ultrashort electromagnetic pulses in gyrotron traveling wave tube with helically corrugated waveguide

    SciTech Connect

    Ginzburg, N. S. Zaslavsky, V. Yu.; Zotova, I. V.; Sergeev, A. S.; Zheleznov, I. V.; Samsonov, S. V.; Mishakin, S. V.

    2015-11-15

    A time-domain self consistent theory of a gyrotron traveling wave tube with a helically corrugated operating waveguide has been developed. Based on this model, the process of short pulse amplification was studied in regimes of grazing and intersection of the dispersion curves of the electromagnetic wave and the electron beam. In the first case, the possibility of amplification without pulse form distortion was demonstrated for the pulse spectrum width of the order of the gain bandwidth. In the second case, when the electrons' axial velocity was smaller than the wave's group velocity, it was shown that the slippage of the incident signal with respect to the electron beam provides feeding of the signal by “fresh” electrons without initial modulation. As a result, the amplitude of the output pulse can exceed the amplitude of its saturated value for the case of the grazing regime, and, for optimal parameters, the peak output power can be even larger than the kinetic power of the electron beam.

  5. Rate equations for nitrogen molecules in ultrashort and intense x-ray pulses

    NASA Astrophysics Data System (ADS)

    Liu, Ji-Cai; Berrah, Nora; Cederbaum, Lorenz S.; Cryan, James P.; Glownia, James M.; Schafer, Kenneth J.; Buth, Christian

    2016-04-01

    We study theoretically the quantum dynamics of nitrogen molecules (N2) exposed to intense and ultrafast x-rays at a wavelength of 1.1 {{nm}} (1100 {{eV}} photon energy) from the Linac Coherent Light Source (LCLS) free electron laser. Molecular rate equations are derived to describe the intertwined photoionization, decay, and dissociation processes occurring for N2. This model complements our earlier phenomenological approaches, the single-atom, symmetric-sharing, and fragmentation-matrix models of 2012 (J. Chem. Phys. 136 214310). Our rate-equations are used to obtain the effective pulse energy at the sample and the time scale for the dissociation of the metastable dication {{{N}}}22+. This leads to a very good agreement between the theoretically and experimentally determined ion yields and, consequently, the average charge states. The effective pulse energy is found to decrease with shortening pulse duration. This variation together with a change in the molecular fragmentation pattern and frustrated absorption—an effect that reduces absorption of x-rays due to (double) core hole formation—are the causes for the drop of the average charge state with shortening LCLS pulse duration discovered previously.

  6. Rate equations for nitrogen molecules in ultrashort and intense x-ray pulses

    DOE PAGESBeta

    Liu, Ji -Cai; Berrah, Nora; Cederbaum, Lorenz S.; Cryan, James P.; Glownia, James M.; Schafer, Kenneth J.; Buth, Christian

    2016-03-16

    Here, we study theoretically the quantum dynamics of nitrogen molecules (N2) exposed to intense and ultrafast x-rays at a wavelength ofmore » $$1.1\\;{\\rm{nm}}$$ ($$1100\\;{\\rm{eV}}$$ photon energy) from the Linac Coherent Light Source (LCLS) free electron laser. Molecular rate equations are derived to describe the intertwined photoionization, decay, and dissociation processes occurring for N2. This model complements our earlier phenomenological approaches, the single-atom, symmetric-sharing, and fragmentation-matrix models of 2012 (J. Chem. Phys. 136 214310). Our rate-equations are used to obtain the effective pulse energy at the sample and the time scale for the dissociation of the metastable dication $${{\\rm{N}}}_{2}^{2+}$$. This leads to a very good agreement between the theoretically and experimentally determined ion yields and, consequently, the average charge states. The effective pulse energy is found to decrease with shortening pulse duration. This variation together with a change in the molecular fragmentation pattern and frustrated absorption—an effect that reduces absorption of x-rays due to (double) core hole formation—are the causes for the drop of the average charge state with shortening LCLS pulse duration discovered previously.« less

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

    NASA Astrophysics Data System (ADS)

    Koptev, M. Yu; Anashkina, E. A.; Bobkov, K. K.; Likhachev, M. E.; Levchenko, A. E.; Aleshkina, S. S.; Semjonov, S. L.; Denisov, A. N.; Bubnov, M. M.; Lipatov, D. S.; Laptev, A. Yu; Gur'yanov, A. N.; Andrianov, A. V.; Muravyev, S. V.; Kim, A. V.

    2015-05-01

    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 range 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.

  8. Measuring spatiotemporal intensity-and-phase complexity of multimode fiber output pulses

    NASA Astrophysics Data System (ADS)

    Guang, Zhe; Rhodes, Michelle; Trebino, Rick

    2016-03-01

    We demonstrate ultrashort pulse spatiotemporal field measurement for multimode optical fibers, using a singleframe characterization technique, called Spatially and Temporally Resolved Intensity and Phase Evaluation Device: Full Information from a Single Hologram (STRIPED FISH). We measure STRIPED FISH traces and retrieve the pulse field E(x,y,t) or equivalently E(x,y,ω), to generate movies revealing the field structure induced by propagating modes, due to their differences in field spatial distribution, modal propagation velocity and modal dispersion inside the fiber. We launch femtosecond pulses near 800nm from Ti: Sapphire laser to investigate linearly polarized modes LP01, LP11, LP02 and LP21 in multimode fibers.

  9. Self-channeling of ultrashort laser pulses in materials with anomalous dispersion

    NASA Astrophysics Data System (ADS)

    Bergé, L.; Skupin, S.

    2005-06-01

    The nonlinear dynamics of femtosecond optical pulses propagating in solid media with anomalous group-velocity dispersion (GVD) is investigated. A map fixing the boundaries of collapse or noncollapse regimes for high-power beams versus the relative strength of GVD is first established. Next, from a nonlinear Schrödinger model accounting for higher-order dispersion, self-steepening, and plasma generation, the possibility of producing extended collapse events that promote a long self-guiding is confirmed, in agreement with recent experiments [K.D. Moll and A.L. Gaeta, Opt. Lett. 29, 995 (2004)]. Three-dimensional collapsing pulses are shown to propagate by emitting quasiperiodically bursts of temporally compressed light bullets, with durations close to the single cycle limit.

  10. Design and construction of a PW ultrashort laser facility with ns, ps, and fs outputting pulses

    NASA Astrophysics Data System (ADS)

    Zhu, Qihua; Huang, Xiaojun; Wang, Xiao; Zeng, Xiaoming; Xie, Xudong; Wang, Fang; Wang, Fengrui; Lin, Donghui; Jiang, Dongbin; Wang, Xiaodong; Zhou, Kainan; Zuo, Yanlei; Zhang, Ying; Deng, Ying; Wei, Xiaofeng; Fan, Dianyuan

    2007-06-01

    A petawatt laser facility with three beams for fast ignition research and strong-field physics applications has been designed and is being constructed. The first beam (referred as SILEX-I) is a Ti:sapphire femto-second laser which pulse width is 30 fs, and till now, output power has reached to 330 TW. The other two beams are Nd 3+:glass lasers which output energy are larger than 1kJ and pulse width are about 1ps and 1ns respectively. By using the technology of OPA pumped by 800nm femtosecond laser and seeded by super-continuum white light (SWL), the three beams are synchronized with each other without jitter time. Tiled multilayer dielectric coating gratings are used for the compressor of the PW beam.

  11. Optical third-harmonic surface microscopy using ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Stoker, David; Downer, Michael C.; Becker, Michael F.; Keto, John W.

    2005-12-01

    The time dependence of third-harmonic generation in an optical material is modelled for an ultrafast pulse from a Ti : Sapphire laser. For normally dispersive materials, the group velocity mismatch of the fundamental and harmonic fields is significant. In the absence of phase matching, pulse breakup is observed. Thirdharmonic generation is governed by a bulk susceptibility, but is sensitive to material interfaces. It is shown that the sensitivity to interfaces is enhanced by group velocity walk-off, and that interface resolution is better than previously reported. It is possible to use the surface sensitivity to develop an interferometric microscopy tool for investigating thin films. The experimental technique is demonstrated on a thin AlN coating grown on a Al2O3 substrate.

  12. Technical advantages of disk laser technology in short and ultrashort pulse processes

    NASA Astrophysics Data System (ADS)

    Graham, P.; Stollhof, J.; Weiler, S.; Massa, S.; Faisst, B.; Denney, P.; Gounaris, E.

    2011-03-01

    This paper demonstrates that disk-laser technology introduces advantages that increase efficiency and allows for high productivity in micro-processing in both the nanosecond (ns) and picosecond (ps) regimes. Some technical advantages of disk technology include not requiring good pump beam quality or special wavelengths for pumping of the disk, high optical efficiencies, no thermal lensing effects and a possible scaling of output power without an increase of pump beam quality. With cavity-dumping, the pulse duration of the disk laser can be specified between 30 and hundreds of nanoseconds, but is independent of frequency, thus maintaining process stability. TRUMPF uses this technology in the 750 watts average power laser TruMicro 7050. High intensity, along with fluency, is important for high ablation rates in thinfilm removal. Thus, these ns lasers show high removal rates, above 60 cm2/s, in thin-film solar cell production. In addition, recent results in paint-stripping of aerospace material prove the green credentials and high processing rates inherent with this technology as it can potentially replace toxic chemical processes. The ps disk technology meanwhile is used in, for example, scribing of solar cells, wafer dicing and drilling injector nozzles, as the pulse duration is short enough to minimize heat input in the laser-matter interaction. In the TruMicro Series 5000, the multi-pass regenerative amplifier stage combines high optical-optical efficiencies together with excellent output beam quality for pulse durations of only 6 ps and high pulse energies of up to 0.25 mJ.

  13. Method and apparatus for improving the quality and efficiency of ultrashort-pulse laser machining

    DOEpatents

    Stuart, Brent C.; Nguyen, Hoang T.; Perry, Michael D.

    2001-01-01

    A method and apparatus for improving the quality and efficiency of machining of materials with laser pulse durations shorter than 100 picoseconds by orienting and maintaining the polarization of the laser light such that the electric field vector is perpendicular relative to the edges of the material being processed. Its use is any machining operation requiring remote delivery and/or high precision with minimal collateral dames.

  14. Two-photon lithography and nanoprocessing with picojoule extreme ultrashort 12 femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    König, Karsten; Uchugonova, Aisada; Schug, Michael; Zhang, Huijing; Saremi, Sumarie; Feili, Dara; Seidel, Helmut

    2010-02-01

    A compact ultra-broadband femtosecond laser scanning microscope with 12 femtoseconds pulse width at the focal plane of a high NA objective has been employed in material nanoprocessing. The laser works at 85 MHz with an M-shaped emission spectrum with maxima at 770 nm and 827 nm. Different motorized setups based on the introduction of chirped mirrors, flint glass wedges, and glass blocks have been realized to vary the in situ pulse length from 12 femtoseconds up to 3 picoseconds. Nanoprocessing was performed in silica, photoresists, glass, polymers, and biological structures. Mean powers as low as 2 mW were sufficient to realize plasma-mediated cutting effects in human chromosomes with sub-80 nm cut width. Using a mean power of 7-9 mW, transient nanoholes were "drilled" in the cellular membrane for targeted transfection of stem cells and the introduction of μRNA probes. Region of interest (ROI) scanning have been used for optical cleaning of human adult stem cell populations and blood cell suspensions. 3D two-photon nanolithography based on the ultrabroad band laser pulses was realized with the photoresist SU-8. Multiphoton sub-20fs microscopes may become novel non-invasive 3D tools for highly precise nanoprocessing of inorganic and organic targets.

  15. Pulse front adaptive optics in multiphoton microscopy

    NASA Astrophysics Data System (ADS)

    Sun, B.; Salter, P. S.; Booth, M. J.

    2016-03-01

    The accurate focusing of ultrashort laser pulses is extremely important in multiphoton microscopy. Using adaptive optics to manipulate the incident ultrafast beam in either the spectral or spatial domain can introduce significant benefits when imaging. Here we introduce pulse front adaptive optics: manipulating an ultrashort pulse in both the spatial and temporal domains. A deformable mirror and a spatial light modulator are operated in concert to modify contours of constant intensity in space and time within an ultrashort pulse. Through adaptive control of the pulse front, we demonstrate an enhancement in the measured fluorescence from a two photon microscope.

  16. Amplification of ultra-short light pulses by ion collective modes in plasmas. The use of damage-less optics for high laser intensities

    NASA Astrophysics Data System (ADS)

    Frank, A.; Fuchs, J.; Lancia, L.; Lehmann, G.; Marquès, J.-R.; Mourou, G.; Riconda, C.; Spatschek, K. H.; Toncian, T.; Vassura, L.; Weber, S.

    2014-05-01

    The use of plasmas provides a way to overcome the damage threshold of classical solid-state based optical materials which is the main limitation encountered in producing extreme power laser pulses. In particular one can use plasmas to directly amplify ultra-short laser pulses to very high intensities. Multi-dimensional kinetic simulations and first proof-of-principle experiments show the feasibility of using plasma instabilities involving ion waves, such as stimulated Brillouin backscattering, in a controlled way to transfer energy from a long pump pulse to a short seed pulse and thereby increase the intensity of the latter. Plasma parametric amplification, and the use of plasma mirrors for focusing, is part of the newly developping domain of plasma optics, which eventually will pave the way to Exawatt lasers.

  17. Visualizing electron delocalization, electron-proton correlations, and the Einstein-Podolsky-Rosen paradox during the photodissociation of a diatomic molecule using two ultrashort laser pulses

    SciTech Connect

    Chelkowski, Szczepan; Bandrauk, Andre D.

    2010-06-15

    We investigate theoretically the dissociative ionization of an H{sub 2}{sup +} molecule using two ultrashort laser (pump-probe) pulses. The pump pulse prepares a dissociating nuclear wave packet on an ungerade surface of H{sub 2}{sup +}. Next, an ultraviolet [or extreme ultraviolet (XUV)] probe pulse ionizes this dissociating state at large (R=20-100 bohr) internuclear distance. We calculate the momenta distributions of protons and photoelectrons which show a (two-slit-like) interference structure. A general, simple interference formula is obtained which depends on the electron and protons momenta, as well as, on the pump-probe delay and also on the durations and polarizations of the laser pulses. This pump-probe scheme reveals a striking quantum delocalization of the electron over two protons which intuitively should be localized on just one of the protons separated by the distance R much larger than the atomic Bohr orbit.

  18. Room temperature optical anisotropy of a LaMnO3 thin-film induced by ultra-short pulse laser

    SciTech Connect

    Munkhbaatar, Purevdorj; Marton, Zsolt; Tsermaa, Bataarchuluun; Choi, Woo Seok; Seo, Sung Seok A.; Kim, Jin Seung; Nakagawa, Naoyuki; Hwang, H. Y.; Lee, Ho Nyung; Myung-Whun, Kim

    2015-03-04

    Ultra-short laser pulse induced optical anisotropy of LaMnO3 thin films grown on SrTiO3 substrates were observed by irradiation with a femto-second laser pulse with the fluence of less than 0.1 mJ/cm2 at room temperature. The transmittance and reflectance showed different intensities for different polarization states of the probe pulse after pump pulse irradiation. The theoretical optical transmittance and re ectance that assumed an orbital ordering of the 3d eg electrons in Mn3+ ions resulted in an anisotropic time dependent changes similar to those obtained from the experimental results, suggesting that the photo-induced optical anisotropy of LaMnO3 is a result of photo-induced symmetry breaking of the orbital ordering for an optically excited state.

  19. Room temperature optical anisotropy of a LaMnO3 thin-film induced by ultra-short pulse laser

    DOE PAGESBeta

    Munkhbaatar, Purevdorj; Marton, Zsolt; Tsermaa, Bataarchuluun; Choi, Woo Seok; Seo, Sung Seok A.; Kim, Jin Seung; Nakagawa, Naoyuki; Hwang, H. Y.; Lee, Ho Nyung; Myung-Whun, Kim

    2015-03-04

    Ultra-short laser pulse induced optical anisotropy of LaMnO3 thin films grown on SrTiO3 substrates were observed by irradiation with a femto-second laser pulse with the fluence of less than 0.1 mJ/cm2 at room temperature. The transmittance and reflectance showed different intensities for different polarization states of the probe pulse after pump pulse irradiation. The theoretical optical transmittance and re ectance that assumed an orbital ordering of the 3d eg electrons in Mn3+ ions resulted in an anisotropic time dependent changes similar to those obtained from the experimental results, suggesting that the photo-induced optical anisotropy of LaMnO3 is a result ofmore » photo-induced symmetry breaking of the orbital ordering for an optically excited state.« less

  20. Comparison of experimental and simulated Kα yield for 400nm ultrashort pulse laser irradiation

    NASA Astrophysics Data System (ADS)

    Khattak, F. Y.; Percie Du Sert, O. A. M. B.; Riley, D.; Foster, P. S.; Divall, E. J.; Hooker, C. J.; Langley, A. J.; Smith, J.; Gibbon, P.

    2006-08-01

    Ti Kα emission yields from foils irradiated with ˜45fs , p -polarized pulses of a frequency-doubled Ti:sapphire laser are presented. A simple model invoking vacuum heating to predict absorption and hot electron temperature was coupled with the cross section for K -shell ionization of Ti and the Bethe-Bloch stopping power equation for electrons. The peak predicted Kα emission was in generally good agreement with experiment. This contrasts strongly with previous work at the fundamental frequency. Similar predictions using particle-in-cell (PIC) code simulation to estimate the number and temperature of hot electrons also gave good agreement for yield.

  1. Comparison of experimental and simulated Kalpha yield for 400 nm ultrashort pulse laser irradiation.

    PubMed

    Khattak, F Y; Percie du Sert, O A M B; Riley, D; Foster, P S; Divall, E J; Hooker, C J; Langley, A J; Smith, J; Gibbon, P

    2006-08-01

    Ti Kalpha emission yields from foils irradiated with approximately 45 fs, p-polarized pulses of a frequency-doubled Ti:sapphire laser are presented. A simple model invoking vacuum heating to predict absorption and hot electron temperature was coupled with the cross section for K -shell ionization of Ti and the Bethe-Bloch stopping power equation for electrons. The peak predicted Kalpha emission was in generally good agreement with experiment. This contrasts strongly with previous work at the fundamental frequency. Similar predictions using particle-in-cell (PIC) code simulation to estimate the number and temperature of hot electrons also gave good agreement for yield. PMID:17025569

  2. Almost sudden perturbation of a quantum system with ultrashort electric pulses

    SciTech Connect

    Lugovskoy, Andrey; Bray, Igor

    2008-02-15

    We present an alternative approach to analyze atomic behavior when an external field perturbation is not sudden for a number of states of the field-free system. It is shown that the probability amplitudes for the system to be in these states can be accurately estimated from the closed set of their integral equations. Numerical examples for an electron in a one-dimensional Coulomb potential interacting with (i) laser and (ii) half-cycle pulses are provided. Comparison with exact calculations indicates the strength of the approach.

  3. Comparison of experimental and simulated K{alpha} yield for 400 nm ultrashort pulse laser irradiation

    SciTech Connect

    Khattak, F. Y.; Percie du Sert, O. A. M. B.; Riley, D.; Foster, P. S.; Divall, E. J.; Hooker, C. J.; Langley, A. J.; Smith, J.; Gibbon, P.

    2006-08-15

    Ti K{alpha} emission yields from foils irradiated with {approx}45 fs, p-polarized pulses of a frequency-doubled Ti:sapphire laser are presented. A simple model invoking vacuum heating to predict absorption and hot electron temperature was coupled with the cross section for K-shell ionization of Ti and the Bethe-Bloch stopping power equation for electrons. The peak predicted K{alpha} emission was in generally good agreement with experiment. This contrasts strongly with previous work at the fundamental frequency. Similar predictions using particle-in-cell (PIC) code simulation to estimate the number and temperature of hot electrons also gave good agreement for yield.

  4. Generation of a beam of fast electrons by tightly focusing a radially polarized ultrashort laser pulse

    SciTech Connect

    Payeur, S.; Fourmaux, S.; Schmidt, B. E.; MacLean, J. P.; Tchervenkov, C.; Legare, F.; Kieffer, J. C.; Piche, M.

    2012-07-23

    The generation of an electron beam through longitudinal field acceleration from a tightly focused radially polarized (TM{sub 01}) laser mode is reported. The longitudinal field is generated by focusing a TM{sub 01} few-cycle laser pulse (1.8 {mu}m, 550 {mu}J, 15 fs) with a high numerical aperture parabola. The created longitudinal field in the focal region is intense enough to ionize atoms and accelerate electrons to 23 keV of energy from a low density oxygen gas. The characteristics of the electron beam are presented.

  5. Spectral broadening induced by intense ultra-short pulse in 4H–SiC crystals

    NASA Astrophysics Data System (ADS)

    Chun-hua, Xu; Teng-fei, Yan; Gang, Wang; Wen-jun, Wang; Jing-kui, Liang; Xiao-long, Chen

    2016-06-01

    We report the observation of spectral broadening induced by 200 femtosecond laser pulses with the repetition rate of 1 kHz at the wavelength of 532 nm in semi-insulating 4H–SiC single crystals. It is demonstrated that the full width at half maximum of output spectrum increases linearly with the light propagation length and the peak power density, reaching a maximum 870 cm‑1 on a crystal of 19 mm long under an incident laser with a peak power density of 60.1 GW/cm2. Such spectral broadening can be well explained by the self-phase modulation model which correlates time-dependent phase change of pulses to intensity-dependent refractive index. The nonlinear refractive index n 2 is estimated to be 1.88×10‑15 cm2/W. The intensity-dependent refractive index is probably due to both the nonlinear optical polarizability of the bound electrons and the increase of free electrons induced by the two-photon absorption process. Super continuum spectra could arise as crystals are long enough to induce the self-focusing effect. The results show that SiC crystals may find applications in spectral broadening of high power lasers. Project supported by the National High Technology Research and Development Program of China (Grant No. 2014AA041402) and the National Natural Science Foundation of China (Grant Nos. 51272276 and 51322211).

  6. Single attosecond burst generation during ionization of excited atoms by intense ultrashort laser pulses

    SciTech Connect

    Emelin, M. Yu.; Ryabikin, M. Yu. Sergeev, A. M.

    2008-02-15

    We develop an analytical approach to describing the generation of a single attosecond burst during barrier-suppression ionization of a hydrogen atom by an intense laser pulse. We derive analytical expressions that describe the evolution of the electron wave packet in the time interval between the detachment from the atom and the collision with the parent ion for an arbitrary initial atomic state by assuming the atom to be fully ionized in one laser-field half-period. For various s-states, we derive expressions for the profile of the attosecond burst generated when the electron packet collides with the ion and analyze the dependence of its generation efficiency on the principal quantum number n of the initial atomic state. The results obtained are compared with the results of three-dimensional numerical calculations. We show that the attosecond pulse generation efficiency can be several orders of magnitude higher than that in the case of ionization from the ground state when pre-excited atomic states are used.

  7. Single attosecond burst generation during ionization of excited atoms by intense ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Emelin, M. Yu.; Ryabikin, M. Yu.; Sergeev, A. M.

    2008-02-01

    We develop an analytical approach to describing the generation of a single attosecond burst during barrier-suppression ionization of a hydrogen atom by an intense laser pulse. We derive analytical expressions that describe the evolution of the electron wave packet in the time interval between the detachment from the atom and the collision with the parent ion for an arbitrary initial atomic state by assuming the atom to be fully ionized in one laser-field half-period. For various s-states, we derive expressions for the profile of the attosecond burst generated when the electron packet collides with the ion and analyze the dependence of its generation efficiency on the principal quantum number n of the initial atomic state. The results obtained are compared with the results of three-dimensional numerical calculations. We show that the attosecond pulse generation efficiency can be several orders of magnitude higher than that in the case of ionization from the ground state when pre-excited atomic states are used.

  8. Control and ultra-short pulse generation in stimulated Raman backscattering

    NASA Astrophysics Data System (ADS)

    Škorić, Miloš M.; Nikolić, Ljubomir; Hadžievski, Ljupčo; Batani, Dimitri; Ishiguro, Seiji; Mima, Kunioki

    2016-03-01

    A stimulated Raman scattering (SRS) is a great concern for laser fusion, causing an energy and symmetry loss and target preheating. In particular, for dominating backward- SRS (BRS), a complexity of nonlinear saturation was revealed. Recently, to develop lasers at multi-exawatts and beyond, relevant to high-energy physics, a proposed Raman amplification based on BRS met a restrictive operation window. Here, we stress BRS generics that due to a nonlinear frequency shift (relativistic/trapping effect), it nonlinearly saturates with intermittent pulsations. A “break up” of Manley-Rowe invariants explains a non-steady saturation. Further, a coherent pulsation BRS regime is proposed for femto-sec pulse generation in a thin exploding foil plasma, with parameter scalings investigated by analytics and particle simulations.

  9. A review of non-linear terahertz spectroscopy with ultrashort tabletop-laser pulses

    NASA Astrophysics Data System (ADS)

    Hwang, Harold Y.; Fleischer, Sharly; Brandt, Nathaniel C.; Perkins, Bradford G., Jr.; Liu, Mengkun; Fan, Kebin; Sternbach, Aaron; Zhang, Xin; Averitt, Richard D.; Nelson, Keith A.

    2015-10-01

    Over the past decade, breakthroughs in the generation and control of ultrafast high-field terahertz (THz) radiation have led to new spectroscopic methodologies for the study of light-matter interactions in the strong-field limit. In this review, we will outline recent experimental demonstrations of non-linear THz material responses in materials ranging from molecular gases, to liquids, to varieties of solids - including semiconductors, nanocarbon, and correlated electron materials. New insights into how strong THz fields interact with matter will be discussed in which a THz field can act as either a non-resonant electric field or a broad bandwidth pulse driving specific resonances within it. As an emerging field, non-linear THz spectroscopy shows promise for elucidating dynamic problems associated with next generation electronics and optoelectronics, as well as for demonstrating control over collective material degrees of freedom.

  10. Depth profiling and imaging capabilities of an ultrashort pulse laser ablation time of flight mass spectrometer

    PubMed Central

    Cui, Yang; Moore, Jerry F.; Milasinovic, Slobodan; Liu, Yaoming; Gordon, Robert J.; Hanley, Luke

    2012-01-01

    An ultrafast laser ablation time-of-flight mass spectrometer (AToF-MS) and associated data acquisition software that permits imaging at micron-scale resolution and sub-micron-scale depth profiling are described. The ion funnel-based source of this instrument can be operated at pressures ranging from 10−8 to ∼0.3 mbar. Mass spectra may be collected and stored at a rate of 1 kHz by the data acquisition system, allowing the instrument to be coupled with standard commercial Ti:sapphire lasers. The capabilities of the AToF-MS instrument are demonstrated on metal foils and semiconductor wafers using a Ti:sapphire laser emitting 800 nm, ∼75 fs pulses at 1 kHz. Results show that elemental quantification and depth profiling are feasible with this instrument. PMID:23020378

  11. Optical breakdown of multilayer thin-films induced by ultrashort pulses at MHz repetition rates.

    PubMed

    Angelov, Ivan B; von Pechmann, Maximilian; Trubetskov, Michael K; Krausz, Ferenc; Pervak, Vladimir

    2013-12-16

    Multilayer coatings composed of TiO(2), Ta(2)O(5), HfO(2), or Al(2)O(3) as high-index materials and SiO(2) as low-index material were investigated for laser-induced damage using 1 ps, 5 µJ pulses generated by a mode-locked Yb:YAG thin-disk oscillator operating at a wavelength of 1030 nm and repetition rate of 11.5 MHz. Previously reported linear band gap dependence of damage threshold at kHz repetition rates was confirmed also for the MHz regime. Additionally, we studied the effect of electric field distribution inside of the layer stack. We did not observe any significant influence of thermal effects on the laser-induced damage threshold in this regime. PMID:24514719

  12. Spectral broadening in lithium niobate in a self-diffraction geometry using ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Dharmadhikari, Jayashree A.; Dota, Krithika; Mathur, Deepak; Dharmadhikari, Aditya K.

    2016-05-01

    We report on broadband light generation in the impulsive regime in an un-doped lithium niobate (LiNbO3) crystal by two femtosecond laser pulses (36 fs) from a Ti-sapphire laser amplifier. We systematically investigate the role of incident intensity on spectral broadening. At relatively low incident intensity (0.7 TW cm-2), spectral broadening in the transmitted beam occurs due to the combined effect of self-phase modulation and cross-phase modulation. At higher incident intensity (10.2 TW cm-2), we observe generation of as many as 21 anti-Stokes orders due to coherent anti-Stokes Raman scattering in self-diffraction geometry. Moreover, we observe order-dependent spectral broadening of anti-Stokes lines that may be attributed to the competition with other nonlinear optical effects like cross-phase modulation.

  13. Void-nanograting transition by ultrashort laser pulse irradiation in silica glass.

    PubMed

    Dai, Ye; Patel, Aabid; Song, Juan; Beresna, Martynas; Kazansky, Peter G

    2016-08-22

    The structural evolution from void modification to self-assembled nanogratings in fused silica is observed for moderate (NA > 0.4) focusing conditions. Void formation, appears before the geometrical focus after the initial few pulses and after subsequent irradiation, nanogratings gradually occur at the top of the induced structures. Nonlinear Schrödinger equation based simulations are conducted to simulate the laser fluence, intensity and electron density in the regions of modification. Comparing the experiment with simulations, the voids form due to cavitation in the regions where electron density exceeds 1020 cm-3 but is below critical. In this scenario, the energy absorption is insufficient to reach the critical electron density that was once assumed to occur in the regime of void formation and nanogratings, shedding light on the potential formation mechanism of nanogratings. PMID:27557213

  14. Intense-Field Ionization of Monoaromatic Hydrocarbons using Radiation Pulses of Ultrashort Duration: Monohalobenzenes and Azabenzenes

    NASA Astrophysics Data System (ADS)

    Scarborough, T.; Strohaber, J.; Foote, D.; McAcy, C.; Uiterwaal, C. J.

    2014-04-01

    Using 50-fs, 800-nm pulses, we study the intense-field ionization and fragmentation of the monohalobenzenes C6H5-X (X=F, Cl, Br, I) and of the heterocyclics azabenzene C5H5N (pyridine) and the three diazabenzenes C4H4N2 (pyridazine, pyrimidine, and pyrazine). Avoiding focal intensity averaging we find indications of resonance-enhanced MPI. In the monohalobenzenes the propensity for fragmentation increases for increasing Z: fluorobenzene yields predominantly C6H5Fn+, while iodobenzene yields atomic ions with charges up to I8+. We ascribe this to the heavy-atom effect: the large charge of the heavy halogens' nuclei induces ultrafast intersystem crossing to dissociative triplet states.

  15. Simulations of intracellular calcium release dynamics in response to a high-intensity, ultrashort electric pulse

    NASA Astrophysics Data System (ADS)

    Joshi, R. P.; Nguyen, A.; Sridhara, V.; Hu, Q.; Nuccitelli, R.; Beebe, S. J.; Kolb, J.; Schoenbach, K. H.

    2007-04-01

    Numerical simulations for electrically induced, intracellular calcium release from the endoplasmic reticulum are reported. A two-step model is used for self-consistency. Distributed electrical circuit representation coupled with the Smoluchowski equation yields the ER membrane nanoporation for calcium outflow based on a numerical simulation. This is combined with the continuum Li-Rinzel model and drift diffusion for calcium dynamics. Our results are shown to be in agreement with reported calcium release data. A modest increase (rough doubling) of the cellular calcium is predicted in the absence of extra-cellular calcium. In particular, the applied field of 15kV/cm with 60ns pulse duration makes for a strong comparison. No oscillations are predicted and the net recovery period of about 5min are both in agreement with published experimental results. A quantitative explanation for the lack of such oscillatory behavior, based on the density dependent calcium fluxes, is also provided.

  16. Peculiarities of filamentation of sharply focused ultrashort laser pulses in air

    SciTech Connect

    Geints, Yu. E.; Zemlyanov, A. A.; Ionin, A. A.; Kudryashov, S. I.; Seleznev, L. V. Sinitsyn, D. V.; Sunchugasheva, E. S.

    2010-11-15

    Peculiarities of the self-focusing and filamentation of high-power femtosecond laser pulses in air have been experimentally and theoretically studied under conditions of broad variation of the beam focusing parameter. The influence of the numerical aperture (NA) of the initial radiation focusing on the main characteristics of laser-induced plasma columns (characteristic transverse size, length, and concentration of free electrons) is considered. It is established that, for a rigid (NA > 0.05) initial laser beam focusing, the transverse size of the plasma channel ceases to decrease at a level of R{sub pl} {approx} 2-4 {mu}m as a result of strong refraction of radiation on the plasma formed at the focal waist, which prevents further contraction of the laser beam due to its focusing and self-focusing.

  17. Single-Active-Electron Approximation for Describing Molecules in Ultrashort Laser Pulses

    NASA Astrophysics Data System (ADS)

    Saenz, Alejandro; Awasthi, Manohar; Vanne, Yulian; Castro, Alberto; Decleva, Piero

    2008-05-01

    A numerical approach that allows for the solution of the time-dependent Schr"odinger equation (TDSE) describing molecules exposed to intense short laser pulses was developed. The molecular response to the strong field is described within the single-active electron approximation (SAE). The method is applied to molecular hydrogen and the validity of the SAE is investigated by comparing the ionization and electronic excitation yields to full two-electron solutions of the TDSE. The present results are also used to investigate the validity of approximate SAE methods like the molecular Ammosov-Delone-Krainov and the strong-field approximation. Finally, results for larger molecules like O2, N2, and C2H2 (acetylene) are presented.

  18. Magnetic resonance imaging of myelin using ultrashort Echo time (UTE) pulse sequences: Phantom, specimen, volunteer and multiple sclerosis patient studies.

    PubMed

    Sheth, Vipul; Shao, Hongda; Chen, Jun; Vandenberg, Scott; Corey-Bloom, Jody; Bydder, Graeme M; Du, Jiang

    2016-08-01

    Clinical magnetic resonance imaging of multiple sclerosis (MS) has focused on indirect imaging of myelin in white matter by detecting signal from protons in the water associated with myelin. Here we show that protons in myelin can be directly imaged using ultrashort echo time (UTE) free induction decay (FID) and imaging sequences on a clinical 3T MR scanner. An adiabatic inversion recovery UTE (IR-UTE) sequence was used to detect signal from myelin and simultaneously suppress signal from water protons. Validation studies were performed on myelin lipid and myelin basic protein (MBP) phantoms in the forms of lyophilized powders as well as suspensions in D2O and H2O. IR-UTE sequences were then used to image MS brain specimens, healthy volunteers, and patients. The T2* of myelin was measured using a UTE FID sequence, as well as UTE and IR-UTE sequences at different TEs. T2* values of ~110-330μs were measured with UTE FID, as well as with UTE and IR-UTE sequences for myelin powders, myelin-D2O and myelin-H2O phantoms, consistent with selective imaging of myelin protons with IR-UTE sequences. Our studies showed myelin selective imaging of white matter in the brains in vitro and in vivo. Complete or partial signal loss was observed in specimens in areas of the brain with histopathologic evidence of myelin loss, and in the brain of patients with MS. PMID:27155128

  19. Particle characteristics of different materials after ultra-short pulsed laser (USPL) irradiation

    NASA Astrophysics Data System (ADS)

    Meister, Joerg; Schelle, Florian; Kowalczyk, Philip; Frentzen, Matthias

    2012-01-01

    The exposition of nanoparticles caused by laser application in dental health care is an open discussion. Based on the fact that nanoparticles can penetrate through the mucosa, the knowledge about particle characteristics after irradiation with an USPL is of high importance. Therefore, the aim of this study was to investigate the particle characteristics, especially the size of the ablated debris after USPL irradiation. The irradiation was carried out with an USP Nd:YVO4 laser with a center wavelength of 1064 nm. Based on the pulse duration of 8 ps and a pulse repetition rate of 500 kHz the laser emits an average power of 9 W. The materials investigated were dental tissues and dental restorative materials (composite and amalgam), ceramic and different metals (gold and aluminium). The samples were irradiated with a power density in the order of 300 GW/cm2 at distances of 5, 10, 15, and 20 mm. The debris was collected on an object plate. SEM pictures were used for analysis of the ablation debris. Depending on the irradiated material, we observed different kinds of structures: vitreous, flocculent, and pellet-like. The mean particle sizes were 10 x 10 up to 30 x 30 μm2. In addition, a cluster of ablated matter (nanometer range) distributed over the whole irradiated area was found. With increasing distances the cluster structure reduced from multi-layer to mono-layer clusters. Particle sizes in the micrometer and nanometer range were found after irradiation with an USPL. The nanoparticles create a cluster structure which is influenced by increasing distances.

  20. Near-field localization by two dimensional metallic nano-post arrays with ultrashort light pulses

    NASA Astrophysics Data System (ADS)

    Lee, Hongki; Kim, Chulhong; Kim, Donghyun

    2016-03-01

    Locally amplified near-fields can be induced with nanostructures within a sub-diffraction-limited volume, which is useful for biomedical imaging and sensing applications. Employment of field localization in the biomedical applications where the pulsed light is used necessitates the spatial and temporal characteristics of fields near nanostructures. We considered the gold nano-post arrays of three different shapes to localize the near-fields which are circular, rhombic, and triangular. They were modeled to be located on an ITO film and a quartz substrate with periods changing from 300 to 900 nm by 200 nm. Their size changes from 50 to 250 nm which corresponds to the radius for the case of circular nanoposts and the distance between the center and the vertices for equilateral rhombic and triangular nanoposts. Numerical calculation of near-fields at the top of nanoposts was performed with finite difference time domain method when the Gaussian pulses at center wavelengths of 532, 633, and 850 nm were normally incident. Near-fields localization occurred mainly at vertices of the nanoposts, which makes the triangular nanoposts of primary interest with an observation of the strongest field intensity within a diffraction limited field-of-view. The observed fields on the triangular vertices were enhanced by 7.85, 51.54, and 7268 when the center wavelengths were 532, 633, and 850 nm respectively. Their temporal peaks were delayed by 2.05, 4.03, and 14.49 fs, which indicates the correlation between field enhancement and time delay associated with electron damping process. It was shown that with rhombic and triangular nanoposts fields can be localized below 10 nm on vertices and their signal-to-noise ratio increased with a larger period.