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Showing papers on "Femtosecond pulse shaping published in 2000"


Journal ArticleDOI
TL;DR: In this article, the field of femtosecond pulse shaping is reviewed, and applications of pulse shaping to optical communications, biomedical optical imaging, high power laser amplifiers, quantum control, and laser-electron beam interactions are reviewed.
Abstract: We review the field of femtosecond pulse shaping, in which Fourier synthesis methods are used to generate nearly arbitrarily shaped ultrafast optical wave forms according to user specification. An emphasis is placed on programmable pulse shaping methods based on the use of spatial light modulators. After outlining the fundamental principles of pulse shaping, we then present a detailed discussion of pulse shaping using several different types of spatial light modulators. Finally, new research directions in pulse shaping, and applications of pulse shaping to optical communications, biomedical optical imaging, high power laser amplifiers, quantum control, and laser-electron beam interactions are reviewed.

2,051 citations


Journal ArticleDOI
24 Mar 2000-Science
TL;DR: Femtosecond synchrotron pulses were generated directly from an electron storage ring and offer the possibility of applying x-ray techniques on an ultrafast time scale to investigate structural dynamics in condensed matter.
Abstract: Femtosecond synchrotron pulses were generated directly from an electron storage ring. An ultrashort laser pulse was used to modulate the energy of electrons within a 100-femtosecond slice of the stored 30-picosecond electron bunch. The energy-modulated electrons were spatially separated from the long bunch and used to generate ∼300-femtosecond synchrotron pulses at a bend-magnet beamline, with a spectral range from infrared to x-ray wavelengths. The same technique can be used to generate ∼100-femtosecond x-ray pulses of substantially higher flux and brightness with an undulator. Such synchrotron-based femtosecond x-ray sources offer the possibility of applying x-ray techniques on an ultrafast time scale to investigate structural dynamics in condensed matter.

571 citations


Journal ArticleDOI
TL;DR: It is demonstrated experimentally that an arbitrary phase and amplitude profile can be applied to an ultrashort pulse by use of an acousto-optic programmable dispersive filter (AOPDF) that has a large group-delay range and a 30% diffraction efficiency over 150 THz.
Abstract: We demonstrate experimentally that an arbitrary phase and amplitude profile can be applied to an ultrashort pulse by use of an acousto-optic programmable dispersive filter (AOPDF). Our filter has a large group-delay range that extends over 3 ps and a 30% diffraction efficiency over 150 THz. Experiments were conducted on a kilohertz chirped-pulse amplification laser chain capable of generating 30-fs pulses without additional pulse shaping. Compensating for gain narrowing and residual phase errors with an AOPDF in place of the stretcher results in 17-fs transform-limited pulses. Arbitrary shaping of these 17-fs pulses is also demonstrated in both the temporal and the spectral domains.

529 citations


Journal ArticleDOI
TL;DR: This work investigates theoretically the self-focusing dynamics of an ultrashort laser pulse both near and above the threshold at which the pulse effectively undergoes catastrophic collapse, and finds that an "optical shock" wave forms inside the medium that gives rise to a broad blueshifted pedestal in the transmitted pulse spectrum.
Abstract: We investigate theoretically the self-focusing dynamics of an ultrashort laser pulse both near and above the threshold at which the pulse effectively undergoes catastrophic collapse. We find that, as a result of space-time focusing and self-steepening, an "optical shock" wave forms inside the medium that gives rise to a broad blueshifted pedestal in the transmitted pulse spectrum. Our results are in good agreement with the primary features observed in experiments and thus provide a theoretical understanding for the underlying process that gives rise to "white-light" generation.

485 citations


Journal ArticleDOI
TL;DR: In this article, an intense mid-infrared light source that provides femtosecond pulses on a microjoule energy level, broadly tunable in the 3-20-µm wavelength range with pulse durations as short as 50 fs at 5 µm.
Abstract: We report on an intense mid-infrared light source that provides femtosecond pulses on a microjoule energy level, broadly tunable in the 3–20-µm wavelength range with pulse durations as short as 50 fs at 5 µm. The pulses are generated by phase-matched difference-frequency mixing in GaSe of near-infrared signal and idler pulses of a parametric device based on a 1-kHz Ti:sapphire amplifier system. Pulse durations are characterized with different techniques including autocorrelation measurements in AgGaS2, two-photon absorption in InSb, and cross-correlation measurements with near-infrared pulses in a thin GaSe crystal. A subsequent zero-dispersion stretcher of high transmission allows for optimum pulse compression, a more detailed amplitude and phase characterization and, ultimately, amplitude shaping of the mid-infrared pulses.

318 citations


Patent
19 Dec 2000
TL;DR: In this article, an energy-efficient method and system for processing target material such as microstructures in a microscopic region without causing undesirable changes in electrical and/or physical characteristics of material surrounding the target material is provided.
Abstract: An energy-efficient method and system for processing target material such as microstructures in a microscopic region without causing undesirable changes in electrical and/or physical characteristics of material surrounding the target material is provided. The system includes a controller for generating a processing control signal and a signal generator for generating a modulated drive waveform based on the processing control signal. The waveform has a sub-nanosecond rise time. The system also includes a gain-switched, pulsed semiconductor seed laser for generating a laser pulse train at a repetition rate. The drive waveform pumps the laser so that each pulse of the pulse train has a predetermined shape. Further, the system includes a laser amplifier for optically amplifying the pulse train to obtain an amplified pulse train without significantly changing the predetermined shape of the pulses. The amplified pulses have little distortion and have substantially the same relative temporal power distribution as the original pulse train from the laser. Each of the amplified pulses has a substantially square temporal power density distribution, a sharp rise time, a pulse duration and a fall time. The system further includes a beam delivery and focusing subsystem for delivering and focusing at least a portion of the amplified pulse train onto the target material. The rise time (less than about 1 ns) is fast enough to efficiently couple laser energy to the target material, the pulse duration (typically 2-10 ns) is sufficient to process the target material, and the fall time (a few ns) is rapid enough to prevent the undesirable changes to the material surrounding the target material.

234 citations


Journal ArticleDOI
TL;DR: The self-similar scaling of the propagating pulse in the amplifier is found to be determined by the functional form of the gain profile, and the solution in the high-power limit that corresponds to a linearly chirped parabolic pulse is found.
Abstract: Self-similarity techniques are used to study pulse propagation in a normal-dispersion optical fiber amplifier with an arbitrary longitudinal gain profile. Analysis of the nonlinear Schrodinger equation that describes such an amplifier leads to an exact solution in the high-power limit that corresponds to a linearly chirped parabolic pulse. The self-similar scaling of the propagating pulse in the amplifier is found to be determined by the functional form of the gain profile, and the solution is confirmed by numerical simulations. The implications for achieving chirp-free pulses after compression of the amplifier output are discussed.

221 citations


Journal ArticleDOI
TL;DR: In this article, femtosecond table-top laser system was used to convert low-energy photons into antiparticles, namely positrons, and the average intensity of this source of positrons was estimated to be equivalent to 2×108
Abstract: Utilizing a femtosecond table-top laser system, we have succeeded in converting via electron acceleration in a plasma channel, low-energy photons into antiparticles, namely positrons. The average intensity of this source of positrons is estimated to be equivalent to 2×108 Bq and it exhibits a very favorable scaling for higher laser intensities. The advent of positron production utilizing femtosecond laser pulses may be the forerunner to a table-top positron source appropriate for applications in material science, and fundamental physics research like positronium spectroscopy.

193 citations


Journal ArticleDOI
TL;DR: In this paper, the authors developed ultrashort pulse generation by the electrooptic modulation method, where continuous-wave laser light of any wavelength can be converted to trains of ultra-short optical pulses with a variable and high repetition frequency by means of an electro-optic phase modulator, and an optical group-delay-dispersion circuit or an optical synthesizer for the compression of the chirped light.
Abstract: We have developed ultrashort pulse generation by the electrooptic modulation method, where continuous-wave laser light of any wavelength can be converted to trains of ultrashort optical pulses with a variable and high repetition frequency by means of an electrooptic phase modulator for the generation of deeply chirped light, and an optical group-delay-dispersion circuit or an optical synthesizer for the compression of the chirped light. Adopting the technologies of domain inversion and guided-wave optics to this electrooptic modulation method, it will be possible to realize integrated ultrashort optical pulse generators.

174 citations


Journal ArticleDOI
TL;DR: Some spectral narrowing during amplification was shown to be compatible with the time-varying profile of the pump beam and consistent with the measured recompressed pulse durations before and after amplification, respectively.
Abstract: Optical parametric chirped pulse amplifiers offer exciting prospects for generating new extremes in power, intensity, and pulse duration. An experiment is described that was used to investigate the operation of this scheme up to energies approaching a joule, as a step toward its implementation at the petawatt level. The results demonstrate an energy gain of 1010 with an energy extraction efficiency of 20% and close to diffraction-limited performance. Some spectral narrowing during amplification was shown to be compatible with the time-varying profile of the pump beam and consistent with the measured recompressed pulse durations of 260 and 300 fs before and after amplification, respectively.

165 citations


Journal ArticleDOI
TL;DR: It is demonstrated, for what is believed to be the first time, that the problem of pedestals in laser amplifiers can be addressed by spectral-domain correction.
Abstract: We demonstrate the use of a deformable-mirror pulse shaper, combined with an evolutionary optimization algorithm, to correct high-order residual phase aberrations in a 1-mJ, 1-kHz, 15-fs laser amplifier. Frequency-resolved optical gating measurements reveal that the output pulse duration of 15.2 fs is within our measurement error of the theoretical transform limit. This technique significantly reduces the pulse duration and the temporal prepulse energy of the pulse while increasing the peak intensity by 26%. It is demonstrated, for what is believed to be the first time, that the problem of pedestals in laser amplifiers can be addressed by spectral-domain correction.

Journal ArticleDOI
TL;DR: An analytical expression relating the group delay at the output of the AOPDF to the input acoustic signal is obtained with coupled-wave theory in the case of collinear and quasi-collinear bulk acousto-optic interactions.
Abstract: Acousto-optic programmable dispersive filters (AOPDF) can compensate in real time for large amounts of group-delay dispersion. This feature can be used in chirped-pulse amplification femtosecond laser chains to compensate adaptively for dispersion. An analytical expression relating the group delay at the output of the AOPDF to the input acoustic signal is obtained with coupled-wave theory in the case of collinear and quasi-collinear bulk acousto-optic interactions and also in the case of planar waveguides and optical fibers. With this relation, the acoustic signal that will induce an arbitrary group-delay variation with frequency can be easily obtained. Numerical simulations are shown to support the principle of arbitrary group-delay control with an AOPDF.

Journal ArticleDOI
TL;DR: Possibilities to produce sub-diffraction limited structures in thin metal films and bulk dielectric materials using femtosecond laser pulses are investigated and results on the fabrication of sub-micrometer structures in 100-200 nm chrome-coated surfaces by direct ablative writing are reported.
Abstract: Possibilities to produce sub-diffraction limited structures in thin metal films and bulk dielectric materials using femtosecond laser pulses are investigated. The physics of ultrashort pulse laser ablation of solids is outlined. Results on the fabrication of sub-micrometer structures in 100–200 nm chrome-coated surfaces by direct ablative writing are reported. Polarization maintaining optical waveguides produced by femtosecond laser pulses inside crystalline quartz are demonstrated.

Journal ArticleDOI
TL;DR: Good agreement was found between the experimental results and numerical pulse-propagation studies, and the phase of the spectrally compressed pulse was found to be constant over the spectral and temporal envelopes, which is indicative of a transform-limited pulse.
Abstract: We demonstrate near-transform-limited pulse generation through spectral compression arising from nonlinear propagation of negatively chirped pulses in optical fiber. The output pulse intensity and phase were quantified by use of second-harmonic generation frequency-resolved optical gating. Spectral compression from 8.4 to 2.4 nm was obtained. Furthermore, the phase of the spectrally compressed pulse was found to be constant over the spectral and temporal envelopes, which is indicative of a transform-limited pulse. Good agreement was found between the experimental results and numerical pulse-propagation studies.

Journal ArticleDOI
TL;DR: A sinc-sampled fiber Bragg grating is used to achieve multiplication of the repetition rate of a pulse stream from 10 to 40 GHz with spectral characteristics that ensure that the resultant pulses-solitons of 3.4-ps width-have the same individual pulse characteristics as those of the input.
Abstract: A sinc-sampled fiber Bragg grating is used to achieve multiplication of the repetition rate of a pulse stream from 10 to 40 GHz. The spectral characteristics of the grating ensure that the resultant pulses—solitons of 3.4-ps width—have the same individual pulse characteristics as those of the input.

Journal ArticleDOI
TL;DR: In this article, the potential of three-dimensional cutting effects within the corneal stroma for refractive surgery applications was evaluated in vitro on freshly enucleated porcine eyeglobes.
Abstract: Focusing femtosecond (fs) laser pulses into transparent media, such as corneal tissue, leads to optical breakdown, generation of a micro-plasma and, thus, a cutting effect inside the tissue - provided the intensity at the focus exceeds a threshold which depends on the pulse duration. For fs pulses, the corresponding threshold pulse energy is reduced by some orders of magnitude compared with ns or ps pulses. At a low pulse energy, thermal and mechanical damage to surrounding tissue is minimized, enabling a highly precise cutting effect inside the tissue while leaving anterior layers unaltered. In the following, investigations concerning aspects of the interaction of ultrashort laser pulses with aqueous media are presented: in particular, detection of pressure transients and bubble formation. For the first time - to our knowledge - the content of the resulting gas bubbles was analysed by gas chromatography, giving evidence of molecular hydrogen. Secondly, the potential of three-dimensional cutting effects within the corneal stroma for refractive surgery applications was evaluated in vitro on freshly enucleated porcine eyeglobes. Laser pulses with a duration of 200-300 fs and energies of 1.5-600 µJ were provided by a mode-locked Ti:sapphire laser with subsequent chirped pulse amplification.

Journal ArticleDOI
TL;DR: In this article, the femtosecond X-ray pulses were generated from a synchrotron storage ring by using an ultrashort optical pulse to create femto-cond time structure on the stored electron bunch.
Abstract: The generation of femtosecond X-ray pulses will have important scientific applications by enabling the direct measurement of atomic motion and structural dynamics in condensed matter on the fundamental time scale of a vibrational period. Interaction of femtosecond laser pulses with relativistic electron beams is an effective approach to generating femtosecond pulses of X-rays. In this paper we present recent results from proof-of-principle experiments in which 300 fs pulses are generated from a synchrotron storage ring by using an ultrashort optical pulse to create femtosecond time structure on the stored electron bunch. A previously demonstrated approach for generating femtosecond X-rays via Thomson scattering between terawatt laser pulses and relativistic electrons is reviewed and compared with storage-ring based schemes.

Journal ArticleDOI
TL;DR: The propagation properties of beams of ultrashort terahertz (THz) pulses emitted from large-aperture (LA) antennas are investigated and the temporal profile of the THz pulse contains information about the temporal and spatial field distribution on the emitter surface, which is intrinsically connected to the carrier dynamics of the antenna substrate.
Abstract: We present a detailed investigation of the propagation properties of beams of ultrashort terahertz (THz) pulses emitted from large-aperture (LA) antennas. The large area of the emitter is demonstrated to have substantial influence on the temporal pulse profile in both the near field and the far field. We perform a numerical analysis based on scalar and vectorial broadband diffraction theory and are able to distinguish between near-field and far-field contributions to the total THz signal. We find that the THz beam from a LA antenna propagates like a Gaussian beam and that the temporal profile of the THz pulse, measured in the near field, contains information about the temporal and spatial field distribution on the emitter surface, which is intrinsically connected to the carrier dynamics of the antenna substrate. As a result of pulse reshaping, focusing of the THz beam leads to a reduced relative pulse momentum, with implications in THz field-ionization experiments.

Journal ArticleDOI
TL;DR: Amplification of ultrashort laser pulses in microcapillary plasmas by a counterpropagating pumping beam is experimentally demonstrated, indicating that a nonlinear pump depletion regime must have been accessed for this amplification.
Abstract: We experimentally demonstrated amplification of ultrashort laser pulses (200 fs pulses) in microcapillary plasmas by a counterpropagating pumping beam Energy amplification as large as a factor of 5 was observed Importantly, a nonlinear pump depletion regime must have been accessed, since the parameters support not only the amplification of the pulse, but an absolutely growing instability if the pump is not depleted Further indication of accessing the nonlinear depletion is indicated by the relative insensitivity to the initial pulse energy

Journal ArticleDOI
TL;DR: A model of isodiffracting single-cycle and few-cycle ultrashort electromagnetic pulses based on exact solutions of the time-dependent paraxial wave equation with space-time coupling effects included is presented.
Abstract: We present a model of isodiffracting single-cycle and few-cycle ultrashort electromagnetic pulses. The model is based on exact solutions of the time-dependent paraxial wave equation with space-time coupling effects included. The spatiotemporal structure of these pulses is characterized by a scaling parameter which relates off-axis pulse shapes to the axial temporal waveforms. Depending on the spectrum a pulse may transform itself from a single-cycle pulse to a multicycle pulse along the radial coordinate. This model is also used to describe recirculating pulses in a curved mirror cavity resonator. The Gouy phase shift contributes an absolute phase that results in a pulse-to-pulse temporal instability.

Journal ArticleDOI
TL;DR: Am amplitude and phase shaping of femtosecond mid-infrared pulses in a range centered about 14 mum are experimentally demonstrated, in good agreement with a model that describes phase-matched optical rectification.
Abstract: We experimentally demonstrate amplitude and phase shaping of femtosecond mid-infrared pulses in a range centered about 14 µm. Single pulses with a tailored optical phase and phase-locked double pulses are generated by phase-matched difference-frequency mixing in a GaSe crystal of near-infrared pulses shaped with a liquid-crystal modulator. The electric field transients are directly measured by free-space electro-optic sampling, yielding pulse durations of 200–300 fs. Our data are in good agreement with a model that describes phase-matched optical rectification.

Journal ArticleDOI
TL;DR: In this article, a frequency-domain phase shaper is combined with different pulse characterization methods and appropriate optimization algorithms to compensate for any phase deviation, in particular, bandwidth-limited, amplified laser pulses are achieved by maximizing the second-harmonic generation of the shaped laser pulses with the aid of an evolutionary algorithm.
Abstract: We describe the experimental implementation of feedback-optimized femtosecond laser pulse shaping. A frequency-domain phase shaper is combined with different pulse characterization methods and appropriate optimization algorithms to compensate for any phase deviation. In particular, bandwidth-limited, amplified laser pulses are achieved by maximizing the second-harmonic generation (SHG) of the shaped laser pulses with the aid of an evolutionary algorithm. Real-time measurement of the absolute phases is achieved with spectral interferometry where the reference pulse is characterized by FROG, the so-called TADPOLE method. Using the complete electric field as feedback, arbitrary laser pulse shapes can be optimally generated in two different ways. First, a local convergence algorithm can be used to apply reliable and accurate spectral chirps. Second, an evolutionary algorithm can be employed to reach specific temporal profiles.

Journal ArticleDOI
TL;DR: In this article, an alternative method for measuring ultrashort extreme-ultraviolet pulses that can be synchronized with an intense infrared pulse is presented, which has a potential accuracy of close to 1 fs and is susceptible to single-shot operation.
Abstract: We present an alternative method for measuring ultrashort extreme-ultraviolet pulses that can be synchronized with an intense infrared pulse. The method, based on photoionization of a target atom by the extreme-ultraviolet pulse in the presence of the infrared pulse, has a potential accuracy of close to 1 fs and is susceptible to single-shot operation. It is demonstrated on harmonic 15 of a titanium:sapphire laser. The minimum pulse duration that can be measured is limited only by the frequency of the radiation used for the ponderomotive shift of the ionization potential (3 fs in the case of the titanium:sapphire fundamental).

Journal ArticleDOI
TL;DR: It is shown that angle-dithering a second-harmonic-generation crystal that is otherwise too narrowband (that is, too thick) can yield sufficient phase-matching bandwidth and an accurate pulse measurement and is applied to frequency-resolved optical gating (FROG) and shows that accurate pulse measurements can be made using a comparatively very thick and hence narrowband crystal.
Abstract: We show that the usual phase-matching-bandwidth constraint in ultrashort-laser-pulse measurement techniques is overly restrictive. Specifically, the phase-matching bandwidth need not exceed the pulse bandwidth on every pulse. Instead, only the phase-matching bandwidth integrated over the measurement period need exceed the pulse bandwidth. We show that angle-dithering a second-harmonic-generation crystal that is otherwise too narrowband (that is, too thick) can yield sufficient phase-matching bandwidth and an accurate pulse measurement. We apply this technique to frequency-resolved optical gating (FROG) and show that accurate pulse measurements can be made using a comparatively very thick and hence narrowband crystal. An additional advantage of using a thick crystal is increased signal strength.

Journal ArticleDOI
TL;DR: The generation of intense ultrabroadband optical pulses whose spectrum ranges from 300 to 1000 nm (700-THz bandwidth) with a well-behaved spectral phase and 23-muJ pulse energy by a novel, simple setup utilizing induced phase modulation (IPM) in an argon-filled single-mode hollow waveguide.
Abstract: We experimentally demonstrate the generation of intense ultrabroadband optical pulses whose spectrum ranges from 300 to 1000 nm (700-THz bandwidth) with a well-behaved spectral phase and 23‐µJ pulse energy by a novel, simple setup utilizing induced phase modulation (IPM) in an argon-filled single-mode hollow waveguide. Fundamental as well as second-harmonic pulses produced by one common femtosecond pulse from a Ti:sapphire laser-amplifier system are copropagated in the hollow waveguide. The effect of the delay time between the two input pulses on the IPM spectral broadening is clarified and confirmed to agree with the theoretical result. It is found that the compressed pulse duration from this pulse is 1.51 fs if its phase is completely compensated for.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the highest process efficiency and hole quality can be achieved by using pulse durations in the sub-picosecond time scale and that nonlinear distortions due to high intensities can be successfully minimized by applying diffractive optical elements for beam forming.
Abstract: The pulse duration requirements for melting-free and burr-free drilling of metals have been observed in detail. It will be shown that the highest process efficiency and hole quality can be achieved by using pulse durations in the subpicosecond time scale. Furthermore, it will be demonstrated that nonlinear distortions due to high intensities can be successfully minimized by applying diffractive optical elements for beam forming. The influence of the polarization of the laser radiation on the process quality will be discussed. Experimental results will show that the rotation of linear polarized radiation during percussion drilling significantly improves the quality of the hole geometry.

Journal ArticleDOI
TL;DR: In this paper, a TF5 prism-pair-formed pulse shaper for programmable pulse chirp compensation was proposed, which has an inner diameter of 140 /spl mu/m and a length of 60 cm.
Abstract: We describe a TF5 prism-pair-formed pulse shaper for programmable pulse chirp compensation. The advantages of this kind of pulse shaper are: (1) very broad bandwidth of transmission; (2) smaller losses; and (3) no requirement for a large-size spatial light modulator (SLM) if the input spectrum is very broad. In our experiment, an ultrabroad spectral (500-1000 nm) pulse is produced by launching 1-kHz, 30-fs, 400-/spl mu/J pulses at 780 nm into an argon filled glass capillary fiber at the gas pressure of 2.0 bar. The fiber has an inner diameter of 140 /spl mu/m and a length of 60 cm. The chirped pulse is first precompressed by a pair of BK7 prisms with a separation length of 65 cm and then directed into the prism-pair-formed pulse-shaping apparatus with a 128-pixel SLM, which provides quadratic and cubic phase compensation. When the quadratic and cubic phases are -330 fs/sup 2/ and +2000 fs/sup 3/, respectively, at the wavelength of 760 nm, an ultrashort optical pulse of 6 fs (FWHM) is generated. This is, to the best of our knowledge, the shortest optical pulse ever compressed using the SLM pulse-shaping technique.

Proceedings ArticleDOI
M. Bergt1, Tobias Brixner1, B. Kiefer1, M. Strehle1, G. Gerber1 
09 Jul 2000
TL;DR: In this article, a femtosecond laser pulse is modified in a pulse shaper and the optimal electric field is optimized iteratively with a feedback-controlled evolutionary algorithm in order to reach specific optimization goals in coherent control experiments.
Abstract: A femtosecond laser pulse is modified in a pulse shaper. The optimal electric field is optimized iteratively with a feedback-controlled evolutionary algorithm in order to reach specific optimization goals in coherent control experiments.

Patent
09 May 2000
TL;DR: In this paper, a medical laser system is disclosed for generating a pulsed output beam of variable pulse duration and wavelength, where the on time of the laser is the pulse duration which is generated by a Q-switch operated in a repetitive mode as a train of micropulses.
Abstract: A medical laser system is disclosed for generating a pulsed output beam of variable pulse duration and wavelength. The on time of the laser is the pulse duration which is generated by a Q-switch operated in a repetitive mode as a train of micropulses. According to one embodiment, a repetitively Q-switched frequency-doubled solid state laser produces an input beam which is subsequently used to excite a dye laser. An excitation source of the solid state laser is modulated to control the pulse duration of the input beam. The dye laser receives the input beam and responsively generates an output beam of adjustable wavelength having a pulse duration corresponding to the pulse duration of the input beam. The wavelength of the output beam is controlled by adjusting a tuning element of the dye laser. The dye laser is coupleable to a delivery system for directing the output laser beam to a biological tissue target. By carefully controlling the pulse duration and wavelength of the beam delivered to the target tissue, a user of the laser system may avoid or minimize damage to tissue adjacent to the target tissue.

Journal ArticleDOI
TL;DR: It is shown that the compression effect is reasonably described by the linear dispersion properties of the photonic crystal itself and the quadratic dispersion approximation cannot be efficiently used for the description of interaction of the femtosecond laser pulses with the thin Photonic crystal.
Abstract: We demonstrate experimentally the effect of compression of femtosecond laser pulses in thin (a few micrometers) one-dimensional photonic crystal. We show that the compression effect is reasonably described by the linear dispersion properties of the photonic crystal itself and the quadratic dispersion approximation cannot be efficiently used for the description of interaction of the femtosecond laser pulses with the thin photonic crystal. For given parameters of the femtosecond pulse it leads to the existence of the optimal dimension of the photonic crystal from the point of view of the compression efficiency. Due to the wide spectral width of the femtosecond laser pulses the high-order dispersion effects play an important role in pulse propagation in photonic crystals and as a result the pulse compression occurs for both positive and negative signs of chirp of the incoming femtosecond pulses.