scispace - formally typeset
Search or ask a question

Showing papers on "Femtosecond pulse shaping published in 2001"


Journal ArticleDOI
08 Nov 2001-Nature
TL;DR: Here, a technique that does not require phase stabilization is used to demonstrate experimentally the influence of the absolute phase of a short laser pulse on the emission of photoelectrons.
Abstract: Currently, the shortest laser pulses1 that can be generated in the visible spectrum consist of fewer than two optical cycles (measured at the full-width at half-maximum of the pulse's envelope). The time variation of the electric field in such a pulse depends on the phase of the carrier frequency with respect to the envelope—the absolute phase. Because intense laser–matter interactions generally depend on the electric field of the pulse, the absolute phase is important for a number of nonlinear processes2,3,4,5,6,7,8. But clear evidence of absolute-phase effects has yet to be detected experimentally, largely because of the difficulty of stabilizing the absolute phase in powerful laser pulses. Here we use a technique that does not require phase stabilization to demonstrate experimentally the influence of the absolute phase of a short laser pulse on the emission of photoelectrons. Atoms are ionized by a short laser pulse, and the photoelectrons are recorded with two opposing detectors in a plane perpendicular to the laser beam. We detect an anticorrelation in the shot-to-shot analysis of the electron yield.

570 citations


Journal ArticleDOI
01 Nov 2001-Nature
TL;DR: Adaptive femtosecond pulse shaping can reveal complex laser fields to achieve chemically selective molecular excitation and the results prove that phase coherences of the solute molecule persist for more than 100 fs in the solvent environment.
Abstract: Coherent light sources can be used to manipulate the outcome of light–matter interactions by exploiting interference phenomena in the time and frequency domain. A powerful tool in this emerging field of ‘quantum control’1,2,3,4,5,6 is the adaptive shaping of femtosecond laser pulses7,8,9,10, resulting, for instance, in selective molecular excitation. The basis of this method is that the quantum system under investigation itself guides an automated search, via iteration loops, for coherent light fields best suited for achieving a control task designed by the experimenter11. The method is therefore ideal for the control of complex experiments7,12,13,14,15,16,17,18,19,20. To date, all demonstrations of this technique on molecular systems have focused on controlling the outcome of photo-induced reactions in identical molecules, and little attention has been paid to selectively controlling mixtures of different molecules. Here we report simultaneous but selective multi-photon excitation of two distinct electronically and structurally complex dye molecules in solution. Despite the failure of single parameter variations (wavelength, intensity, or linear chirp control), adaptive femtosecond pulse shaping can reveal complex laser fields to achieve chemically selective molecular excitation. Furthermore, our results prove that phase coherences of the solute molecule persist for more than 100 fs in the solvent environment.

404 citations


Journal ArticleDOI
TL;DR: Computer-controlled femtosecond polarization pulse shaping where intensity, momentary frequency, and light polarization are varied as functions of time is reported.
Abstract: We report computer-controlled femtosecond polarization pulse shaping where intensity, momentary frequency, and light polarization are varied as functions of time. For the first time to our knowledge, a pulse shaper is used to modulate the degree of ellipticity as well as the orientation of the elliptical principal axes within a single laser pulse by use of a 256-pixel two-layer liquid-crystal display inside a zero-dispersion compressor. Interferometric stability of the setup is not required. Complete pulse characterization is achieved by dual-channel spectral interferometry. This technology has a large range of applications, especially in the field of quantum control.

326 citations


Journal ArticleDOI
17 Aug 2001-Science
TL;DR: A coherently synthesized optical pulse is generated from two independent mode-locked femtosecond lasers, providing a route to extend the coherent bandwidth available for ultrafast science and represents a new and flexible approach to the synthesis of coherent light.
Abstract: We generated a coherently synthesized optical pulse from two independent mode-locked femtosecond lasers, providing a route to extend the coherent bandwidth available for ultrafast science. The two separate lasers (one centered at 760 nanometers wavelength, the other at 810 nanometers) are tightly synchronized and phase-locked. Coherence between the two lasers is demonstrated via spectral interferometry and second-order field cross-correlation. Measurements reveal a coherently synthesized pulse that has a temporally narrower second-order autocorrelation width and that exhibits a larger amplitude than the individual laser outputs. This work represents a new and flexible approach to the synthesis of coherent light.

252 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present results of measurements of fluorescence spectra due to the interaction of a Ti:sapphire laser pulse with N2 molecules at different gas pressures and pulse energies.
Abstract: We present results of measurements of fluorescence spectra due to the interaction of a Ti:sapphire laser pulse with N2 molecules at different gas pressures and pulse energies. The analysis of the data together with the results of numerical simulations, using a propagation model, reveal signatures of the phenomena of intensity clamping and of re-focusing of the laser pulse at high gas pressure. The laser pulse energy for intensity clamping as a function of the gas pressure is determined.

233 citations


Journal ArticleDOI
TL;DR: In this paper, the authors review the impact of dispersion on the optics of ultrashort pulses, as well as the measurement and management of the dispersive properties of linear optical elements of which the source is constructed.
Abstract: In this article, we review the phenomenon of dispersion, paying particular attention to its impact in the optics of ultrashort pulses, as well as its measurement and management. At present, lasers generating coherent bandwidths of several hundred nanometers have been demonstrated and correspondingly short pulses of 10 fs or so are quite usual. The limits to the breadth of optical spectra and brevity of pulse durations that may be achieved are often set by the dispersive properties of the linear optical elements of which the source is constructed. Progress in ultrafast optics to date has therefore relied extensively on the development of ways to characterize and manipulate dispersion. The means by which this can be accomplished are significantly different for laser oscillators and laser amplifiers, as well as for nonlinear interactions that are used to extend the range of frequencies at which short optical pulses are available, but in all cases it is this phenomenon that determines the output of current optical sources.

221 citations


Journal ArticleDOI
TL;DR: In this article, an evolutionary algorithm for femtosecond pulse shaping has been proposed, which can automatically steer the interaction between system and electric field and allows control even without any knowledge of the Hamiltonian.
Abstract: Coherent control of a physical or chemical process can be achieved by using phase and amplitude modulated femtosecond laser pulses. A self-learning loop, which connects a femtosecond pulse shaper, an optimization algorithm, and an experimental feedback signal, can automatically steer the interaction between system and electric field and allows control even without any knowledge of the Hamiltonian. The dependability of such a loop is essential to the significance of the optimization results, assigning the optimization algorithm an important role within these learning loops. In this paper, an evolutionary strategy is presented in detail that has successfully been applied to femtosecond pulse shaping in optimal control experiments. A general introduction to evolutionary algorithms is given and the specific adaptation for femtosecond pulse shaping is described. The stability and effectiveness of the algorithm is investigated both in experiments and simulations with an emphasis on the influence of steering parameters of the algorithm, number of configurations in search space, and noise. The algorithm optimizes a set of variables parametrizing the electric field. This particular mapping greatly facilitates the dissection of the optimization goal which is demonstrated by three possible parametrizations and associated applications: polynomial phase functions and adaptive femtosecond pulse compression, periodic phase functions and control of nonlinear photon transitions, multiple pulse structures and control of molecular dynamics.

200 citations


Journal Article
TL;DR: In this paper, a femtosecond laser pulses and nonlinear-optical cross correlation is demonstrated for the investigation of the microstructure of biological systems, using pulses of 65-fsec duration generated by a colliding-pulse mode-locked ring dye laser, a spatial resolution of less than 15 μm with a detection sensitivity to remitted signals as small as 10 -7 of the incident pulse energy.
Abstract: Optical ranging using femtosecond laser pulses and nonlinear-optical cross correlation is demonstrated for the investigation of the microstructure of biological systems. By using pulses of 65-fsec duration generated by a colliding-pulse mode-locked ring dye laser, a spatial resolution of less than 15 μm is achieved with a detection sensitivity to remitted signals as small as 10 -7 of the incident pulse energy. This technique is applied to measure the cornea in rabbit eyes in vivo as well as to investigate the epidermal structure of human skin in vitro.

196 citations


Journal ArticleDOI
11 May 2001
TL;DR: What is believed to be the first demonstration of a continuously tunable soliton source in the wavelength range 1.06-1.33 /spl mu/m, a wavelength range that is difficult to access using conventional solid state laser technology is reported.
Abstract: Summary form only given. Wavelength tunable femtosecond optical pulse sources have applications in areas as diverse as ultrafast spectroscopy, materials processing, optoelectronics, nonlinear optics and optical chemistry. In the past, such sources have been available only in limited wavelength ranges and were realized using solid state lasers with complex, high precision cavities. More recently, the soliton self frequency shift (SSFS) in silica fibers has been exploited to obtain tunable femtosecond pulses; tuning from 1.55-2.2 /spl mu/m was previously reported in conventional silica fiber, and tuning from 1.3-1.6 /spl mu/m has been demonstrated using tapered microstructured fiber. Here we report what we believe is the first demonstration of a continuously tunable soliton source in the wavelength range 1.06-1.33 /spl mu/m, a wavelength range that is difficult to access using conventional solid state laser technology. The system is based on diode pumped Yb/sup 3+/ doped silica fiber components, and operates at mW average input power levels in a 4.7 m length of fiber.

148 citations


Journal ArticleDOI
TL;DR: In this article, the triggering and guiding of leader discharges using a plasma channel created by a sub-joule ultrashort laser pulse have been studied in a megavolt large-scale electrode configuration.
Abstract: The triggering and guiding of leader discharges using a plasma channel created by a sub-joule ultrashort laser pulse have been studied in a megavolt large-scale electrode configuration (3–7 m rod-plane air gap). By focusing the laser close to the positive rod electrode it has been possible, with a 400 mJ pulse, to trigger and guide leaders over distances of 3 m, to lower the leader inception voltage by 50%, and to increase the leader velocity by a factor of 10. The dynamics of the breakdown discharges with and without the laser pulse have been analyzed by means of a streak camera and of electric field and current probes. Numerical simulations have successfully reproduced many of the experimental results obtained with and without the presence of the laser plasma channel.

129 citations


Journal ArticleDOI
TL;DR: In this paper, the authors construct several examples of distinct asymmetric-symmetric pulse pairs with identical or essentially identical intensity autocorrelations and power spectra and infer that pulse retrieval methods based on these two data sets alone produce ambiguous solutions.
Abstract: We construct several examples of distinct asymmetric-symmetric pulse pairs with identical or essentially identical intensity autocorrelations and power spectra. From these examples, we infer that pulse retrieval methods based on these two data sets alone produce ambiguous solutions. Furthermore, we used the constructed pulse pairs as test cases to assess the degree of difference in the corresponding interferometric autocorrelations. In several cases, we found that the differences in the interferometric autocorrelations are sufficiently small that they might be quite challenging to distinguish in a practical experimental context.

Journal ArticleDOI
TL;DR: Initial experiments agree well with calculations and demonstrate the benefits of this nanojoule-energy, 100-fs pulses through a few meters of standard optical fiber, and it is expected it to find use in the many applications that would benefit from fiber delivery of femtosecond pulses.
Abstract: We propose a way to deliver nanojoule-energy, 100-fs pulses at 800 nm through a few meters of standard optical fiber. Pulses from a mode-locked laser are compressed temporally, and then spectrally, to produce the desired pulses at the end of the fiber. Initial experiments agree well with calculations and demonstrate the benefits of this technique: For an energy of ∼0.5 nJ, the delivered pulses are ∼5 times shorter than those delivered by other techniques. The issues that must be addressed to scale the technique up to delivered pulse energies of 5 nJ are identified, and the apparatus employs only readily available components. Thus we expect it to find use in the many applications that would benefit from fiber delivery of femtosecond pulses.

Journal ArticleDOI
TL;DR: In this article, the authors used the diameter reduced type of polarization maintaining fibers to generate a 340-fs soliton pulse at a wavelength of around 2 /spl mu/m using a frequency-resolved optical gating method.
Abstract: Characteristics of widely wavelength tunable ultrashort pulse generation using several types of polarization maintaining fibers have been experimentally analyzed. Using the diameter reduced type of polarization maintaining fibers, the wavelength tunable soliton pulse is generated from 1.56 to 2.03 /spl mu/m. It is confirmed that the almost transform-limited 340-fs soliton pulse is generated at a wavelength of around 2 /spl mu/m using a frequency-resolved optical gating method. When low-birefringence fibers are used, it is observed that the orthogonally polarized small pulse spectrum is trapped by the soliton pulse and is also shifted toward the longer wavelength side in the process of soliton self-frequency shift. The wavelength of the orthogonally polarized pulse spectrum is 40-50 nm longer than that of the soliton pulse, and the birefringence of the fiber is compensated by the chromatic dispersion. Finally, a polarization maintaining highly nonlinear dispersion-shifted fiber is used as the sample fiber. When the fiber input power is low, the wavelength-tunable soliton and anti-Stokes pulses are generated. As the fiber input power is increased, the pulse spectra are gradually overlapped and the 1.1-2.1 /spl mu/m widely broadened supercontinuum spectra are generated by only 520 pJ pulse energy.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the performance of the direct space-to-time (DST) pulse shaping apparatus both theoretically and experimentally, and showed how the operation of the DST pulse shaper may be understood in terms of the femtosecond response of a generalized spectrometer.
Abstract: The direct space-to-time (DST) pulse shaping apparatus is investigated both theoretically and experimentally. The discussion shows how the operation of the DST pulse shaper may be understood in terms of the femtosecond response of a generalized spectrometer. A complete discussion of the advantages and tradeoffs of utilizing this pulse-shaping configuration is given, including the direct scaling between the masking function and the output temporal intensity profile, system efficiency, spectral resolution, and temporal window, compensation/cancellation of chirp, and generation of multiple output waveforms.

Journal ArticleDOI
TL;DR: In this article, a liquid crystal display with 640 stripes was successfully implemented and investigated for femtosecond pulse shaping, which greatly enlarges the manifold of accessible pulse modulations, making the device an ideal tool for coherent control experiments and optical information processing.
Abstract: A novel liquid crystal display (LCD) with 640 stripes was successfully implemented and investigated for femtosecond pulse shaping. As compared to previously used devices, the large active area allows for operation in high-power laser systems. The increased number of pixels greatly enlarges the manifold of accessible pulse modulations, making the device an ideal tool for coherent control experiments and optical information processing.

Journal ArticleDOI
TL;DR: An ultrashort-pulse characterization technique that reveals lateral pulse-shape variations by spatially resolved amplitude and phase measurements by use of spectral phase interferometry for direct electric-field reconstruction (SPIDER).
Abstract: Ultrabroadband pulses exhibit a frequency-dependent mode size owing to the wavelength dependence of free-space diffraction. Additionally, rather complex lateral dependence of the temporal pulse shape has been reported for Kerr-lens mode-locked lasers and broadband amplifier chains and in frequency-domain pulse shapers, for example. We demonstrate an ultrashort-pulse characterization technique that reveals lateral pulse-shape variations by spatially resolved amplitude and phase measurements by use of spectral phase interferometry for direct electric-field reconstruction (SPIDER). Unlike with autocorrelation techniques, with SPIDER we can obtain spatially resolved pulse characterization even after the nonlinear process. Thus, with this method the spectral phase of the pulse can be resolved very rapidly along one lateral beam axis in a single measurement.

Journal ArticleDOI
TL;DR: A new variant of spectral interferometry is introduced, using spectrally dispersed ultrafast laser pulses and quadrature detection to measure optical thickness variations related to surface structure, which has potential applications in device manufacture, optical communications, and error compensation in pulse shaping.
Abstract: We introduce a new variant of spectral interferometry, using spectrally dispersed ultrafast laser pulses and quadrature detection to measure optical thickness variations related to surface structure. We can resolve surface features with depths of 3 mm to 25 nm, using a lateral resolution of ∼100 μm. Quadrature detection gives a larger dynamic range and solves the sign ambiguity problem. This method has potential applications in device manufacture, optical communications, and error compensation in pulse shaping.

Journal ArticleDOI
TL;DR: In this paper, a chaotic laser pulse train for high-precision ranging is presented. The pulse train is produced by inducing coherence collapse in an AlGaAs semiconductor laser.
Abstract: We demonstrate the use of a chaotic laser pulse train for high-precision ranging. The pulse train is produced by inducing coherence collapse in an AlGaAs semiconductor laser. Measurements of optical spectra, intensity autocorrelation functions, and ladar ranging are presented.

Journal ArticleDOI
TL;DR: Backward emission of the supercontinuum from a light filament induced by high-intensity femtosecond laser pulses propagating in air has been observed to be enhanced compared with linear Rayleigh-Mie scattering, interpreted as a nonlinear scattering process onto longitudinal refractive-index changes induced by the laser pulse itself.
Abstract: Backward emission of the supercontinuum from a light filament induced by high-intensity femtosecond laser pulses propagating in air has been observed to be enhanced compared with linear Rayleigh–Mie scattering. This enhancement is interpreted as a nonlinear scattering process onto longitudinal refractive-index changes induced by the laser pulse itself. The spectral dependence of the supercontinuum angular distribution is also investigated.

Journal ArticleDOI
TL;DR: The design of an autocorrelator is shown that can be used to eliminate the pulse-front tilt and simultaneously adjust the pulse duration in real time by adjustment of the pulse compressor of a chirped-pulse amplified laser system.
Abstract: We present a method of adjusting the pulse duration and eliminating the pulse-front tilt of an ultrashort pulse in real time by use of a specially configured single-shot autocorrelator. Pulse-front tilt, or a temporal delay across the pulse front, is a common ultrashort-pulse phenomenon when dispersive elements are being used. We show the design of an autocorrelator that can be used to eliminate the pulse-front tilt and simultaneously adjust the pulse duration in real time by adjustment of the pulse compressor of a chirped-pulse amplified laser system.

Journal ArticleDOI
TL;DR: In this article, the first femtosecond pulse train generation from an arrayed-waveguide grating is presented, where terahertz-rate bursts are produced with the rate determined by the arrayed waveguide delay spacing.
Abstract: We present what we believe to be the first demonstration of femtosecond pulse train generation from an arrayed-waveguide grating. Terahertz-rate bursts of femtosecond pulses are produced with the rate determined by the arrayed-waveguide delay spacing.

Journal ArticleDOI
TL;DR: A revised femtosecond breakdown model for dielectric solids and liquids is presented that is able to model breakdown accurately in the focal region for pulse durations of less than 10 ps and can be of use in estimating the time- and position-resolved electron density in the interaction volume.
Abstract: Laser ablation is widely used in micromachining, manufacturing, thin-film formation, and bioengineering applications. During laser ablation the removal of material and quality of the features depend strongly on the optical breakdown region induced by the laser irradiance. The recent advent of amplified ultrafast lasers with pulse durations of less than 1 ps has generated considerable interest because of the ability of the lasers to process virtually all materials with high precision and minimal thermal damage. With ultrashort pulse widths, however, traditional breakdown models no longer accurately capture the laser–material interaction that leads to breakdown. A femtosecond breakdown model for dielectric solids and liquids is presented that characterizes the pulse behavior and predicts the time- and position-dependent breakdown region. The model includes the pulse propagation and small spatial extent of ultrashort laser pulses. Model results are presented and compared with classical breakdown models for 1-ns, 1-ps, and 150-fs pulses. The results show that the revised model is able to model breakdown accurately in the focal region for pulse durations of less than 10 ps. The model can also be of use in estimating the time- and position-resolved electron density in the interaction volume, the breakdown threshold of the material, shielding effects, and temperature distributions during ultrafast processing.

Journal ArticleDOI
TL;DR: Differences in ablation crater morphology are observed for craters generated with pulse durations in the 130 fs-1 ps and the 5 ps-10 ps range, indicating that a transition occurs between 1 and 5 ps.
Abstract: Ablation characteristics of ultrashort laser pulses were in- vestigated for pulse durations in the range of 130 fs-10 ps. Tissue samples used in the study were dental hard tissue (dentin) and water. We observed differences in ablation crater morphology for craters generated with pulse durations in the 130 fs-1 ps and the 5 ps-10 ps range. For the water experiment, the surface ablation and subsequent propagation of stress waves were monitored using Mach-Zehnder in- terferometry. For 130 fs-1 ps, energy is deposited on the surface while for longer pulses the beam penetrates into the sample. Both studies indicate that a transition occurs between 1 and 5 ps. © 2001 Society of

Journal ArticleDOI
TL;DR: For the first time, it is shown that the pulse shape can be strongly influenced by the laser wavelength and suggests thus a new potentiality of picosecond ultrasonics.
Abstract: We have studied the effect of wavelength change on picosecond acoustic pulses generated using a femtosecond laser. For the first time, we show that the pulse shape can be strongly influenced by the laser wavelength. The results are in excellent agreement with a calculation based on a thermoelastic model which connects them to significant changes in the piezo-optical constants. There are similarities between the present study and stress modulation spectroscopy, which allows us to ascribe the observations to interband transitions and suggests thus a new potentiality of picosecond ultrasonics.

Journal ArticleDOI
TL;DR: A new technique for femtosecond-pulse generation that employs ultrafast modulation of a laser field phase by impulsively excited molecular rotational or vibrational motion with subsequent temporal compression is demonstrated.
Abstract: We demonstrate a new technique for femtosecond-pulse generation that employs ultrafast modulation of a laser field phase by impulsively excited molecular rotational or vibrational motion with subsequent temporal compression. An ultrashort pump pulse at 800 nm performs impulsive excitation of a molecular gas in a hollow waveguide, and a weak delayed probe pulse at 400 nm is scattered on the temporal oscillations of its dielectric index. The resultant sinusoidal phase modulation of the probe pulse permits probe pulse temporal compression by use of both positively and negatively dispersive elements. The potential of this new method is demonstrated by the generation of a periodic train of 5.8-fs pulses at 400 nm with positive group-delay dispersion compensation.

Journal ArticleDOI
TL;DR: In this paper, the formation of ring patterns of a focused femtosecond near IR laser pulse propagating in air before the geometrical focal point was observed, due to the combined effects of self-focusing and defocusing created by the generated plasma via multiphoton/tunnel ionization of air.

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate the generation of 5.0-fs optical pulses (2.5 µJ, 1-kHz repetition rate), using only a spatial light modulator for phase compensation.
Abstract: We experimentally demonstrate the generation of 5.0-fs optical pulses (2.5 µJ, 1-kHz repetition rate), using only a spatial light modulator for phase compensation. Pulse compression of the broadband pulse (500–1000 nm) from an argon-filled capillary fiber is achieved with a liquid-crystal spatial light modulator without any prechirp compensation. The output pulse width is found to be 4.1 fs by a fringe-resolved autocorrelator fitted with a transform-limited pulse and to be 5.0 fs by second-harmonic generation frequency-resolved optical gating with marginal correction. It is to our knowledge the shortest pulse ever generated by use of only a spatial light modulator for phase compensation.

Journal ArticleDOI
TL;DR: In this article, a theory of ultrashort-pulse difference-frequency generation (DFG) with quasi-phase-matching gratings in the undepleted-pump, unamplified-signal approximation is presented.
Abstract: We present a theory of ultrashort-pulse difference-frequency generation (DFG) with quasi-phase-matching (QPM) gratings in the undepleted-pump, unamplified-signal approximation. In the special case of a cw (or quasi-cw) pump, the spectrum of the generated idler is related to the spectrum of the signal through a transfer-function relation that is valid for arbitrary dispersion in the medium. The engineerability of this QPM-DFG transfer function establishes the basis for arbitrary pulse shaping. Experimentally we demonstrate QPM-DFG devices operating in a frequency-degenerate type II configuration and producing pulse-shaped output at 1550 nm from 220-fs pulses at 1550 nm.

Journal ArticleDOI
TL;DR: Adaptive pulse shaping can overcome limitations to the propagation of femtosecond pulses of detectable energy in single-mode optical fibers by synthesizing pulses that are self-correcting for higher-order nonlinear effects when they are launched in the fiber.
Abstract: Nonlinear effects present fundamental obstacles to the propagation of femtosecond pulses of detectable energy in single-mode optical fibers, inducing severe distortion even after a very short (a few meters) propagation distance. We show here that adaptive pulse shaping can overcome these limitations by synthesizing pulses that are self-correcting for higher-order nonlinear effects when they are launched in the fiber. This approach would not only affect optical communications but also yield benefits in various disciplines requiring optimized fiber-based femtosecond pulse delivery, for example, nonlinear imaging techniques such as multiphoton microscopy, material processing, and medical diagnostics.

Journal ArticleDOI
TL;DR: This compression method allows phase compensation of both material and gain dispersion, which produces an optimized wavelength-tunable pulse shape for ultrahigh-resolution time-domain spectroscopy.
Abstract: We have compressed the output from a β-barium borate noncollinear optical parametric amplifier to ∼7‐fs pulse durations, using a micromachined deformable mirror with an efficient search algorithm. This compression method allows phase compensation of both material and gain dispersion, which produces an optimized wavelength-tunable pulse shape for ultrahigh-resolution time-domain spectroscopy.