scispace - formally typeset
Search or ask a question

Showing papers on "Femtosecond pulse shaping published in 2004"


Journal ArticleDOI
TL;DR: Self-similar propagation of ultrashort, parabolic pulses in a laser resonator is observed theoretically and experimentally, constituting a new type of pulse shaping in mode-locked lasers.
Abstract: Self-similar propagation of ultrashort, parabolic pulses in a laser resonator is observed theoretically and experimentally. This constitutes a new type of pulse shaping in mode-locked lasers: in contrast to the well-known static (solitonlike) and breathing (dispersion-managed soliton) pulse evolutions, asymptotic solutions to the nonlinear wave equation that governs pulse propagation in most of the laser cavity are observed. Stable self-similar pulses exist with energies much greater than can be tolerated in solitonlike pulse shaping, and this has implications for practical lasers.

841 citations


Journal ArticleDOI
TL;DR: A noninterferometric single beam method to characterize and compensate the spectral phase of ultrashort femtosecond pulses accurately and is ideally suited for the generation of tailored spectral phase functions required for coherent control experiments.
Abstract: We introduce a noninterferometric single beam method to characterize and compensate the spectral phase of ultrashort femtosecond pulses accurately. The method uses a pulse shaper that scans calibrated phase functions to determine the unknown spectral phase of a pulse. The pulse shaper can then be used to synthesize arbitrary phase femtosecond pulses or it can introduce a compensating spectral phase to obtain transform-limited pulses. This method is ideally suited for the generation of tailored spectral phase functions required for coherent control experiments.

425 citations


Journal ArticleDOI
TL;DR: Ultrashort, high-power laser pulses propagating vertically in the atmosphere have been observed over more than 20 km using an imaging 2-m astronomical telescope, bearing evidence for whole-beam parallelization about the nonlinear focus.
Abstract: Ultrashort, high-power laser pulses propagating vertically in the atmosphere have been observed over more than 20 km using an imaging 2-m astronomical telescope. This direct observation in several wavelength bands shows indications for filament formation at distances as far as 2 km in the atmosphere. Moreover, the beam divergence at 5 km altitude is smaller than expected, bearing evidence for whole-beam parallelization about the nonlinear focus. We discuss implications for white-light Lidar applications.

277 citations


Journal ArticleDOI
TL;DR: In this article, a velocity matching technique utilizing tilted pulse fronts is analyzed in comparison with quasi-phase matching in periodically poled LiNbO3 crystals, which provides a ten times higher pulse energy conversion efficiency.
Abstract: Optical rectification of ultrashort near-IR laser pulses with tilted pulse fronts and pulse energies of a few μJ in Mg-doped stoichiometric LiNbO3 cooled to low temperature is a powerful technique for efficient generation of THz pulses. The pulse energy critically depends on the Mg doping (necessary for preventing photorefractive damage) and can be easily increased by a factor of three if the MgO content is reduced. Pulse energies up to 400 pJ at repetition rates of 200 kHz and 3.4% quantum conversion efficiency are achieved at 77 K. At 10 K, changing the tilt angle of the pump pulse front results in continuous tuning of the frequency across the 1.0–4.4 THz range. The temporal pulse shapes measured by electro-optic sampling are in good agreement with the signal calculated by a simple theory. This model predicts tunability on a considerably broader range and narrower spectra even at room temperature if GaSe is used instead of LiNbO3. The advantages of the velocity matching technique utilizing tilted pulse fronts are analyzed in comparison with quasi-phase-matching in periodically poled LiNbO3 crystals. The first method provides a ten times higher pulse energy conversion efficiency.

238 citations


Journal ArticleDOI
TL;DR: A new method for generating a parabolic pulse by use of a dispersion-decreasing fiber with normal group-velocity dispersion with highly linear chirp allows for efficient and high-quality pulse compression.
Abstract: We propose a new method for generating a parabolic pulse by use of a dispersion-decreasing fiber with normal group-velocity dispersion. When a hyperbolic dispersion-decreasing structure is employed, the pulse evolves into a linearly chirped pulse with an exact parabolic intensity profile without radiating dispersive waves. The highly linear chirp in the parabolic pulse allows for efficient and high-quality pulse compression.

227 citations


Journal ArticleDOI
TL;DR: Waveguides manufactured with the 520-nm radiation from a frequency-doubled, diode-pumped, cavity-dumped Yb:glass laser operating at a 166-KHz repetition rate, with a 300-fs pulse duration are demonstrated.
Abstract: Laser action is demonstrated in a 20-mm-long waveguide fabricated on an Er:Yb-doped phosphate glass by femtosecond laser pulses. An output power of 1.7 mW with approximately 300 mW of pump power coupled into the waveguide is obtained at 1533.5 nm. Waveguides are manufactured with the 520-nm radiation from a frequency-doubled, diode-pumped, cavity-dumped Yb:glass laser operating at a 166-KHz repetition rate, with a 300-fs pulse duration.

184 citations


Journal ArticleDOI
TL;DR: This work reports what is believed to be the first demonstration of a high-power passively mode-locked diode-pumped femtosecond laser based on an Yb3+:CaF2 single crystal, directly pumped by a 15-W fiber-coupled laser diode.
Abstract: We report what is believed to be the first demonstration of a high-power passively mode-locked diode-pumped femtosecond laser based on an Yb3+:CaF2 single crystal, directly pumped by a 15-W fiber-coupled laser diode With a 5-at % Yb3+-doped sample and prisms for dispersion compensation we obtained pulses as short as 150 fs, with 880 mW of average power and up to 14-W average output power, with a pulse duration of 220 fs, centered at 1049 nm The laser wavelength could be tuned from 1040 to 1053 nm in the femtosecond regime Using chirped mirrors for dispersion compensation, the oscillator provided up to 174 W of average power, with a pulse duration of 230 fs, corresponding to a pulse energy of 20 nJ and a peak power of 85 kW

172 citations


Journal ArticleDOI
TL;DR: It is proved that the combination of spatial and temporal chirp also produces pulse-front tilt in ultrashort laser pulses, and this is verified experimentally using a GRENOUILLE.
Abstract: Pulse-front tilt in an ultrashort laser pulse is generally considered to be a direct consequence of, and equivalent to, angular dispersion. We show, however, that, while this is true for certain types of pulse fields, simultaneous temporal chirp and spatial chirp also yield pulse-front tilt, even in the absence of angular dispersion. We verify this effect experimentally using GRENOUILLE.

150 citations


Journal ArticleDOI
TL;DR: Delivery of femtosecond solitons at 800nm wavelength over five meters of hollow-core photonic bandgap fiber is described and numerical modeling shows that the nonlinear phase shift is determined by both the non linearity of air and by the overlap of the guided mode with the glass.
Abstract: We describe delivery of femtosecond solitons at 800nm wavelength over five meters of hollow-core photonic bandgap fiber. The output pulses had a length of less than 300fs and an output pulse energy of around 65nJ, and were almost bandwidth limited. Numerical modeling shows that the nonlinear phase shift is determined by both the nonlinearity of air and by the overlap of the guided mode with the glass.

147 citations


Journal ArticleDOI
TL;DR: In this paper, a container-integrated mobile femtosecond terawatt laser system with integrated detection unit (Teramobile) was used for remote laser-induced breakdown spectroscopy (R-LIBS) on copper and aluminium samples with targets located at 25 m away from the container.
Abstract: Using a container-integrated mobile femtosecond terawatt laser system with integrated detection unit (Teramobile), we have demonstrated remote laser-induced breakdown spectroscopy (R-LIBS) on copper and aluminium samples with targets located at 25 m away from the container. The ability of our laser system to generate pulses in the femtosecond, picosecond and nanosecond regimes allowed us to perform direct comparisons between these three pulse durations. The dependence of the fluorescence signal on laser pulse energy showed a nonlinear behavior with a threshold, which is consistent with the previous observations for laser ablation. Such nonlinear behavior leads to a dependence of the LIBS signal on the temporal-spectral shape of the laser pulse. We showed especially that the transform-limited pulse does not optimize the fluorescence. A properly applied chirp allows an increase of the LIBS signal. Understanding and optimization of the chirp effect would improve the detection limit of the LIBS using a femtosecond laser (Femto-LIBS) and lead to a larger detection distance. Furthermore the use of pulse shaping should enhance the detection specificity for the cases of spectral overlapping between several elements to be identified.

130 citations


Journal ArticleDOI
TL;DR: A novel spectral-shearing interferometry setup for characterizing the temporal amplitude and phase of ultrashort optical pulses over an extremely wide wavelength region and the zero-additional-phase scheme does not alter the unknown pulses and yields the pulse shape at the interaction point of a spectroscopic experiment.
Abstract: We demonstrate a novel spectral-shearing interferometry setup for characterizing the temporal amplitude and phase of ultrashort optical pulses over an extremely wide wavelength region. By the mixing of two strongly chirped auxiliary pulses with the pulse to be characterized, two spectrally sheared replicas are generated, and their spectral interference is evaluated. We fully characterize 10-fs pulses in the visible region by sum-frequency mixing and 19-fs pulses in the ultraviolet region by difference-frequency mixing. The scheme is self-referencing and highly sensitive. The zero-additional-phase scheme does not alter the unknown pulses and yields the pulse shape at the interaction point of a spectroscopic experiment.

Journal ArticleDOI
TL;DR: A new approach to laser control using binary phase shaping to solve the problem of spectrally narrowing multiphoton excitation using shaped laser pulses as required for selectivity in two-photon microscopy is demonstrated.
Abstract: We demonstrate a new approach to laser control using binary phase shaping. We apply this method to the problem of spectrally narrowing multiphoton excitation using shaped laser pulses as required for selectivity in two-photon microscopy. The symmetry of the problem is analyzed from first principles and a rational solution is proposed. Successful experimental implementation and simulations are presented using 10 fs ultrashort pulses. The proposed solution is a factor of 6 better than the sinusoidal phase used previously by our group. An evolutionary learning algorithm was used to efficiently improve the solution by a further factor of 2.5 because of the greatly reduced search space afforded by binary phase shaping.

Journal ArticleDOI
Kyung Taec Kim1, Chul Min Kim1, Moon-Gu Baik, G. Umesh1, Chang Hee Nam1 
TL;DR: In this paper, a method for obtaining a single sub-50-attosecond pulse using harmonic radiation is proposed, where the chirped structure of the harmonic radiation imposes a limit on the minimum achievable pulse duration, but its positive chirp can be compensated by the negative group delay dispersion of an appropriately selected x-ray filter material, used also for the spectral selection.
Abstract: A method for obtaining a single sub-50-attosecond pulse using harmonic radiation is proposed. For the generation of broad harmonic radiation during a single half-optical cycle, atoms are driven by a femtosecond laser pulse with intensity above the saturation intensity for optical field ionization and hence experience a large nonadiabatic increase of the laser electric field between optical cycles. Although the chirped structure of the harmonic radiation imposes a limit on the minimum achievable pulse duration, we demonstrate that its positive chirp can be compensated by the negative group delay dispersion of an appropriately selected x-ray filter material, used also for the spectral selection, resulting in a single attosecond pulse with a duration less than 50 as.

Journal ArticleDOI
TL;DR: Coupling femtosecond light pulses from an all-fiber Er:laser system into a dispersion-shifted and highly non-linear fiber generates output spectra exhibiting two broadband and mutually coherent maxima.
Abstract: Coupling femtosecond light pulses from an all-fiber Er:laser system into a dispersion-shifted and highly non-linear fiber, we generate output spectra exhibiting two broadband and mutually coherent maxima. Depending on the chirp of the input pulse, the spectral separation is easily tunable over a wide range up to values exceeding 100 THz. In this way, the source provides access to an ultrabroadband wavelength interval from 1130 to 1950 nm. Because of soliton effects, the long-wave component exhibits a transform-limited pulse width of 40 fs directly after the nonlinear element. The high-frequency part propagating in the dispersive regime is recompressed to pulse durations as short as 24 fs with an optimized prism sequence.

Journal ArticleDOI
TL;DR: In this article, an imaging spectrograph is used to measure the angular dispersion of a laser beam by an accuracy of 0.2 /spl mu/rad/nm using this technique.
Abstract: A misaligned stretcher or compressor in a chirped pulse amplification laser introduces residual angular dispersion into the beam, resulting in temporal distortion of the pulse. We demonstrate that an imaging spectrograph is capable for measuring the angular dispersion of a laser beam by an accuracy of 0.2 /spl mu/rad/nm. Using this technique, the analytical expressions of residual angular dispersion of misaligned prism and grating compressors are experimentally proved. Temporal degradations of short pulses due to angular dispersion are studied by measuring the temporal stretch of 16-fs pulses, while the issues of contrast deterioration are also discussed. It is proved that the simultaneous measurement of angular dispersion and pulse duration offers the most precise alignment procedure of prismatic and grating compressors.

Book
14 Sep 2004
TL;DR: In this paper, solid-state materials for few-cycled Pulse Generation and Amplification were used for both single and multiple femtosecond XUV-Pulses.
Abstract: Part I: Few-Cycle Pulse Generation: Theory and Experiments.- Solid-State Materials for Few-Cycle Pulse Generation and Amplification.- Few-Cycle Pulses Directly from the Laser.- Few-Cycle Pulses by External Compression.- Parametric Amplification and Phase Control of Few-Cycle Light Pulses.- Part II: Characterization of Ultrashort Laser Pulses: Measuring Ultrashort Pulses in the Single-Cycle Regime.- Characterization of Ultrashort Pulses in the Few-Cycle Regime Using Spectral Phase Interferometry for Direct Electric Field Reconstruction.- Part III: Applications: Optical Frequency-Comb Generation and High-Resolution Laser Spectroscopy.- Carrier-Envelope Phase Stabilization of Single and Multiple Femtosecond Lasers.- Sub-Femtosecond XUV-Pulses: Attosecond Metrology and Spectroscopy.- Resonant Non-Perturbative Extreme Nonlinear Optics with Two-Cycle Pulses.- Dynamics of the Photoexcited Hydrated Electron.- Subject Index.

Journal ArticleDOI
TL;DR: A second-generation pulse-burst laser system for high-speed flow diagnostics with addition of a phase-conjugate mirror allows for more-efficient amplification and harmonic generation, with efficiencies exceeding 50% for second- Harmonic and 40% for third-harmonic generation.
Abstract: A second-generation pulse-burst laser system for high-speed flow diagnostics is described in detail. The laser can produce a burst of high-energy pulses (of the order of hundreds of millijoules per pulse) with individual pulse durations of less than 10 ns and pulse separations as short as 1 micros. A key improvement is the addition of a phase-conjugate mirror, which effectively isolates the high-intensity, short-duration pulses from the low-intensity, long-duration background illumination. It allows for more-efficient amplification and harmonic generation, with efficiencies exceeding 50% for second-harmonic and 40% for third-harmonic generation. Characteristics of the laser system, including gain narrowing, pulse-burst energy distribution, pulse narrowing, and overall pulse-burst energy, are described. In addition, the applicability of the laser for spectroscopic-based flow diagnostics is demonstrated through the presentation of megahertz-rate planar Doppler velocimetry results.

Journal ArticleDOI
TL;DR: Direct experimental comparison with beta-BaB2O4 confirms the superior performance BiB3O6 for second-harmonic generation of femtosecond pulse generation, and tunable range of 375-435 nm in the blue is demonstrated.
Abstract: Efficient generation of tunable femtosecond pulses in the blue is reported in the nonlinear crystal BiB3O6. By use of fundamental pulses from a mode-locked Ti:sapphire laser at 76 MHz, single-pass second-harmonic average powers of as much as 830 mW have been generated at 50% conversion efficiency, and a tunable range of 375–435 nm in the blue is demonstrated. Temporal measurements using cross correlation of the fundamental and second-harmonic pulses in a 100‐µm-thick β‐BaB2O4 crystal result in blue pulse durations of 220 fs for 130-fs fundamental pulses. Direct experimental comparison with β‐BaB2O4 confirms the superior performance BiB3O6 for second-harmonic generation of femtosecond pulses.

Journal ArticleDOI
TL;DR: The fundamental limits to the compressibility of broadband supercontinuum spectra generated in photonic crystal fiber are examined using numerical simulations based on a stochastic extended nonlinear Schrödinger equation.
Abstract: The fundamental limits to the compressibility of broadband supercontinuum spectra generated in photonic crystal fiber are examined using numerical simulations based on a stochastic extended nonlinear Schrodinger equation. An ensemble average over multiple simulations performed with random quantum noise on the input pulse and spontaneous Raman noise during propagation allows a quantitative study of the effects of pulse to pulse fluctuations on the ability to obtain few-cycle pulses after compensation of the supercontinuum spectral phase. We study the dependence of the supercontinuum compressibility on the input pulse duration, the photonic crystal fiber length, and the spectral resolution of the pulse compressor employed.

Journal ArticleDOI
TL;DR: In this paper, the femtosecond pulse shaper in phase and amplitude was realized using two liquid crystal devices with 640 pixels, leading to a wide temporal window around 25'ps at 800'nm.
Abstract: We present the first realization of a femtosecond pulse shaper in phase and amplitude using two liquid crystal devices with 640 pixels, leading to a wide temporal window around 25 ps at 800 nm. Several examples illustrate the high resolution of such device. The use of a folded zero dispersion line is also successfully demonstrated.

Journal ArticleDOI
TL;DR: A holographic probing technique that allows for measurement of free-electron distribution with fine spatial detail and the capability of the holographic technique of capturing the time evolution of the plasma-generation process is demonstrated.
Abstract: We report on a holographic probing technique that allows for measurement of free-electron distribution with fine spatial detail. Plasma is generated by focusing a femtosecond pulse in air. We also demonstrate the capability of the holographic technique of capturing the time evolution of the plasma-generation process.

Journal ArticleDOI
TL;DR: In this article, a 3D time and frequency-domain code for analyzing the spatial, temporal, and spectral properties of a chirped x-ray beam produced by relativistic Thomson scattering is presented.
Abstract: The generation of high intensity, ultrashort x-ray pulses enables exciting new experimental capabilities, such as femtosecond pump-probe experiments used to temporally resolve material structural dynamics on atomic time scales. Thomson backscattering of a high intensity laser pulse with a bright relativistic electron bunch is a promising method for producing such high-brightness x-ray pulses in the 10--100 keV range within a compact facility. While a variety of methods for producing subpicosecond x-ray bursts by Thomson scattering exist, including compression of the electron bunch to subpicosecond bunch lengths and/or colliding a subpicosecond laser pulse in a side-on geometry to minimize the interaction time, a promising alternative approach to achieving this goal while maintaining ultrahigh brightness is the production of a time-correlated (or chirped) x-ray pulse in conjunction with pulse slicing or compression. We present the results of a complete analysis of this process using a recently developed 3D time and frequency-domain code for analyzing the spatial, temporal, and spectral properties an x-ray beam produced by relativistic Thomson scattering. Based on the relativistic differential cross section, this code has the capability to calculate time and space dependent spectra of the x-ray photons produced from linear Thomson scattering for both bandwidth-limited and chirped incident laser pulses. Spectral broadening of the scattered x-ray pulse resulting from the incident laser bandwidth, laser focus, and the transverse and longitudinal phase space of the electron beam were examined. Simulations of chirped x-ray pulse production using both a chirped electron beam and a chirped laser pulse are presented. Required electron beam and laser parameters are summarized by investigating the effects of beam emittance, energy spread, and laser bandwidth on the scattered x-ray spectrum. It is shown that sufficient temporal correlation in the scattered x-ray spectrum to produce sub-100 fs temporal slice resolution can be produced from state-of-the-art, high-brightness electron beams without the need to perform longitudinal compression on the electron bunch.

Journal ArticleDOI
TL;DR: A carrier-envelope phase (CEP) stabilized chirped-pulse amplification (CPA) system employing a grating-based pulse stretcher and compressor and a regenerative amplifier is demonstrated for the first time.
Abstract: We have demonstrated a carrier-envelope phase (CEP) stabilized chirped-pulse amplification (CPA) system employing a grating-based pulse stretcher and compressor and a regenerative amplifier for the first time. In addition to stabilizing the carrier-envelope offset phase of a laser oscillator, a new pulse selection method referenced to the carrier-envelope offset beat signal was introduced. The pulse-selection method is more robust against the carrier-envelope offset phase fluctuations than a simple pulse-clock dividing method. We observed a stable fringe in a self-referencing spectrum interferometry of the amplified pulse, which implies that the CEP of amplified pulse is stabilized. We also measured the effect of the beam angle change on the CEP of amplified pulses. The result demonstrates that the CEP stabilized CPA is scalable to higher-pulse energies.

Patent
18 Aug 2004
TL;DR: In this article, the authors proposed a specially tailored temporal power profile of a laser pulse for IC link severing, which allows the use of a wider laser pulse energy range and shorter laser wavelengths, such as green and UV, to sever the links without appreciable damage to the substrate and passivation structure material located on either side of and underlying the links.
Abstract: A laser pulse with a specially tailored temporal power profile, instead of a conventional temporal shape or substantially square shape, severs an IC link. The specially tailored laser pulse preferably has either an overshoot at the beginning of the laser pulse or a spike peak within the duration of the laser pulse. The timing of the spike peak is preferably set ahead of the time when the link is mostly removed. A specially tailored laser pulse power profile allows the use of a wider laser pulse energy range and shorter laser wavelengths, such as the green and UV, to sever the links without appreciable damage to the substrate and passivation structure material located on either side of and underlying the links.

Journal ArticleDOI
TL;DR: Coherent terahertz emission from the vacuum-plasma interface induced through laser wake-field excitation has been investigated by particle-in-cell simulations and shows clear trends in emission frequency and emission amplitude.
Abstract: Coherent terahertz (THz) emission from the vacuum-plasma interface induced through laser wake-field excitation has been investigated by particle-in-cell simulations. The emission frequency appears around tau(-1)(L), where tau(L) is the laser pulse duration, even though the plasma density is distributed inhomogeneously near the interface. The emission amplitude, which is zero on the propagation axis of the incident pulse, increases transversely until reaching the maximum amplitude at the beam edge of the incident pulse and then decays transversely. The emission power scales like P approximately 10(8) x a(4)(0) W, where a(0) is the normalized field amplitude of the laser pulse. For an incident pulse of a few tens of femtoseconds at the forced intensity of 3 x 10(17) W/cm(2), it can generate THz radiation with a power of a few MW and with an energy of several microJ/pulse.

Journal ArticleDOI
TL;DR: Series of time-resolved still images of the explosion dynamics of micrometer-sized water droplets after femtosecond laser-pulse irradiation were obtained and the influence of different pulse durations produced by chirping the laser pulses was observed.
Abstract: Series of time-resolved still images of the explosion dynamics of micrometer-sized water droplets after femtosecond laser-pulse irradiation were obtained for different laser-pulse intensities. Amplified pulses centered around a wavelength of 805 nm with 1-mJ energy and 60-fs duration were focused onto the droplet to initiate the dynamics. Several effects, such as forward and backward plumes, jets, water films, and shock waves, were investigated. Additionally, the influence of different pulse durations produced by chirping the laser pulses was observed.

Journal ArticleDOI
TL;DR: In this paper, the first direct space-to-time pulse shaper using a virtually imaged phased array as the spectral disperser was presented, and it was used to demonstrate the generation of 10-50-GHz arbitrary microwave waveforms with time apertures as large as 1.0 ns and peakto-peak amplitudes as high as 400 mV.
Abstract: We present the first direct space-to-time pulse shaper using a virtually imaged phased array as the spectral disperser. We use this pulse shaper to demonstrate generation of 10-50-GHz arbitrary microwave waveforms with time apertures as large as 1.0 ns and peak-to-peak amplitudes as high as 400 mV.

Proceedings Article
16 May 2004
TL;DR: In this paper, a passively mode-locked erbium-doped fiber laser was operated in noise-like mode and generated the pulse train with a bandwidth much wider than the gain bandwidth.
Abstract: We operate a passively mode-locked erbium-doped fiber laser in noise-like mode and generate the pulse train with a bandwidth much wider than the gain bandwidth. Super-continuum generation from the noise-like pulse is also demonstrated successfully.

Journal ArticleDOI
TL;DR: Noncollinear, degenerate four-wave mixing experiments that employ a new device based on two-dimensional femtosecond pulse shaping that delays and modulates all incident fields are reported.
Abstract: We report noncollinear, degenerate four-wave mixing experiments that employ a new device based on two-dimensional femtosecond pulse shaping that delays and modulates all incident fields. Heterodyne detection is easily implemented due to the full phase stability of the device.

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate femtosecond operation of an integrated-optic direct space-to-time pulse shaper for which there is a direct mapping (no Fourier transform) between the spatial position of the masking function and the temporal position in the output waveform.
Abstract: We demonstrate femtosecond operation of an integrated-optic direct space-to-time pulse shaper for which there is a direct mapping (no Fourier transform) between the spatial position of the masking function and the temporal position in the output waveform. The apparatus is used to generate trains of more than 30 pulses as an ultrafast optical data packet over approximately an 80-ps temporal window.