Showing papers on "Ultrashort pulse published in 1993"
TL;DR: The frequency-resolved optical gating (FROG) technique as discussed by the authors was proposed to measure the spectrum of the signal pulse as a function of the delay between two input pulses and the resulting trace of intensity versus frequency and delay is related to the pulse's spectrogram a visually intuitive transform containing time and frequency information.
Abstract: The frequency-resolved optical gating (FROG) technique for characterizing and displaying arbitrary femtosecond pulses is presented. The method is simple, general, broadband, and does not require a reference pulse. Using virtually any instantaneous nonlinear-optical effect, FROG involves measuring the spectrum of the signal pulse as a function of the delay between two input pulses. The resulting trace of intensity versus frequency and delay is related to the pulse's spectrogram a visually intuitive transform containing time and frequency information. It is proven using phase retrieval concepts that the FROG trace yields the full intensity I(t) and phase phi (t) of an arbitrary ultrashort pulse with no physically significant ambiguities. FROG appears to have temporal resolution limited only by the response of the nonlinear medium. The method is demonstrated by using self-diffraction through the electronic Kerr effect in BK-7 glass and 620-nm, linearly chirped, approximately 200-fs pulses of a few microjoules. >
846 citations
TL;DR: In this article, an iterative Fourier transform (IFT) algorithm was proposed for inverting the frequency-resolved optical gating (FROG) trace to obtain the pulse intensity and phase.
Abstract: We recently introduced a new technique, frequency-resolved optical gating (FROG), for directly determining the full intensity I(t) and phase φ(t) of a single femtosecond pulse. By using almost any instantaneous nonlinear-optical interaction of two replicas of the ultrashort pulse to be measured, FROG involves measuring the spectrum of the signal pulse as a function of the delay between the replicas. The resulting trace of intensity versus frequency and delay yields an intuitive display of the pulse that is similar to the pulse spectrogram, except that the gate is a function of the pulse to be measured. The problem of inverting the FROG trace to obtain the pulse intensity and phase can also be considered a complex two-dimensional phase-retrieval problem. As a result, the FROG trace yields, in principle, an essentially unique pulse intensity and phase. We show that this is also the case in practice. We present an iterative-Fourier-transform algorithm for inverting the FROG trace. The algorithm is unusual in its use of a novel constraint: the mathematical form of the signal field. Without the use of a support constraint, the algorithm performs quite well in practice, even for pulses with serious phase distortions and for experimental data with noise, although it occasionally stagnates when pulses with large intensity fluctuations are used.
688 citations
TL;DR: In this article, the frequency-resolved optical gating (FOSG) technique was introduced for measuring the intensity and phase of an arbitrary ultrashort pulse using an instantaneous nonlinear-optical interaction of two variably delayed replicas.
Abstract: We introduce a new technique, frequency-resolved optical gating, for measuring the intensity I(t) and the phase ϕ(t) of an individual arbitrary ultrashort pulse. Using an instantaneous nonlinear-optical interaction of two variably delayed replicas of the pulse, frequency-resolved optical gating involves measuring the spectrum of the signal pulse versus relative delay. The resulting trace, a spectrogram, yields an intuitive full-information display of the pulse. Inversion of this trace to obtain the pulse intensity and phase is equivalent to the well-known two-dimensional phase-retrieval problem and thus yields essentially unambiguous results for I(t) and ϕ(t).
484 citations
TL;DR: The pulse energy of the far-infrared radiation is found to be a quadratic function of bias field and a nonmonotonic function of laser intensity.
Abstract: We have generated sub-single-cycle pulses of electromagnetic radiation with pulse energies as high as 0.8 μJ and pulse lengths < 500 fs. The 10-dB width of the spectrum is 1.5 THz. The transmitter is a GaAs wafer illuminated at normal incidence by 120-fs, 770-nm pulses from a Ti:sapphire chirped-pulse amplifier system while a pulsed electric field is applied across the surface. The pulse energy of the far-infrared radiation is found to be a quadratic function of bias field and a nonmonotonic function of laser intensity.
316 citations
TL;DR: In this paper, Gruebele et al. presented a formalism for extracting highly resolved spectral information and the potential of bound isolated systems from coherent ultrafast laser experiments, using I2 as a model system.
Abstract: Recently, we presented a formalism for extracting highly resolved spectral information and the potential of bound isolated systems from coherent ultrafast laser experiments, using I2 as a model system [Gruebele et al., Chem. Phys. Lett. 166, 459 (1990)]. The key to this approach is the formation of coherent wave packets on the potential energy curve (or surface) of interest, and the measurement of their scalar and vector properties. Here we give a full account of the method by analyzing the coherences of the wave packet in the temporal transients of molecules excited by ultrashort laser pulses, either at room temperature, or in a molecular beam. From this, some general considerations for properly treating temporal data can be derived. We also present a direct inversion to the potential and quantum and classical calculations for comparison with the experiments.
208 citations
TL;DR: The advent of lasers powerful enough to generate a measurable effect, and which can be pulsed on femtosecond time scales, has made the optical Kerr effect into a practical technology for investigating the molecular structure and interactions of condensed systems.
Abstract: In the optical Kerr effect, the electric field of light incident on a transparent sample induces an anisotropic refractive index, which is measured by its effect on the passage of a second light beam. The advent of lasers powerful enough to generate a measurable effect, and which can be pulsed on femtosecond time scales, has made the optical Kerr effect into a practical technology for investigating the molecular structure and interactions of condensed systems such as pure liquids, liquid solutions, and plastic crystals.
199 citations
TL;DR: The system allows one to eliminate spatial inhomogeneities and cubic and quartic phase errors that make existing designs unsuitable for use with pulses much shorter than 100 fs, and is experimentally demonstrate >10,000 times expansion and recompression of ∼25-fs optical pulses.
Abstract: Design of an expansion and recompression system for amplification of sub-20-fs optical pulses to multiterawatt peak powers is presented. The system allows one to eliminate spatial inhomogeneities and cubic and quartic phase errors that make existing designs unsuitable for use with pulses much shorter than 100 fs. We experimentally demonstrate >10,000 times expansion and recompression of ∼25-fs optical pulses.
190 citations
TL;DR: A broadly tunable femtosecond optical parametric oscillator (OPO) based on KTiOPO(4) that is externally pumped by a self-mode-locked Ti:sapphire laser is described.
Abstract: A broadly tunable femtosecond optical parametric oscillator (OPO) based on KTiOPO4 is externally pumped by a self-mode-locked Ti:sapphire laser. The laser is capable of continuous tuning from 1.2 micrometers to 1.37 micrometers in the signal branch and 1.8 to 2.15 micrometers in the idler branch, when using one set of OPO optics. Other optics expand the tuning range of the OPO from 1.0 micrometers to 2.75 micrometers, for example, by using three sets of mirrors and two different crystals. Without prisms in the OPO cavity, 215 mW of chirped pulses is generated in the signal branch, while 235 mW is generated in the idler branch. The total conversion efficiency, as measured by pump depletion, is 50%. With prisms in the cavity, nearly transform-limited pulses of 135 femtoseconds are generated, which can be shortened to 75 fs by increasing the output coupling.
173 citations
Proceedings Article•
02 May 1993TL;DR: In this article, the authors reported the first direct sub-picosecond (150 fsec) time-resolved measurement of the energy relaxation of optically excited electrons in Si.
Abstract: While ultrafast optical techniques have been applied extensively to the study of hot electron dynamics in GaAs, there have been very few such studies of Si because conventional optical pumpprobe schemes are difficult to interpret for indirect gap materials. This is unfortunate since understanding hot electron dynamics in Si is key to predicting the behavior of state-of-the-art Si devices. Here we report the first direct subpicosecond (150 fsec) time-resolved measurement of the energy relaxation of optically excited electrons in Si. This is accomplished in a laser pump-probe format by analyzing the photoelectron spectrum generated by an ultrashort uv probe pulse. By this method, we obtain directly the time-evolution of the photo-excited electron distribution function (bulk and interface) in Si with 150 fsec resolution. These measurements would not be possible by either reflectivity/transmission or luminescence schemes.
152 citations
TL;DR: An all-optical signal regenerator capable of ultrafast operation is demonstrated and it is shown that the regenerated data have less intensity variation and less temporal jitter than the incoming data.
Abstract: We demonstrate experimentally an all-optical signal regenerator capable of ultrafast operation. An input data stream first forces mode locking of a cw fiber laser that generates a continuous stream of optical pulses at the line rate. This recovered clock is then modulated by the data stream in a nonlinear fiber loop mirror. We show that the regenerated data have less intensity variation and less temporal jitter than the incoming data.
145 citations
TL;DR: The oscillator presented has the potential for producing sub-10-fs pulses in the 800-nm wavelength region, and the position of the dispersive resonance is used to determine the ratio of the net second- and third-order intracavity dispersions.
Abstract: We report the operating characteristics of a self-mode-locked Ti:sapphire solitary laser at reduced group-delay dispersion. The generation of ≈12.3 fs near-sech2 optical pulses at 775 nm is reported, together with experimental evidence for the dominant role of third-order dispersion (TOD) as a limiting factor to further pulse shortening in the oscillator. At reduced second-order dispersion excessive residual TOD is shown to lead to dispersive wave generation, and the position of the dispersive resonance is used to determine the ratio of the net second- and third-order intracavity dispersions. Since the magnitude of TOD rapidly decreases with increasing wavelength in prism-pair dispersion-compensated resonators, the oscillator presented has the potential for producing sub-10-fs pulses in the 800-nm wavelength region.
TL;DR: The transmission of 100-fs ultrafast laser pulses through biological tissues was measured by using femtosecond and picosecond time-resolved detection techniques and the broadening of transmitted pulses was found to increase as the thickness of the biological tissue increases.
Abstract: The transmission of 100-fs ultrafast laser pulses through biological tissues was measured by using femtosecond and picosecond time-resolved detection techniques. The broadening of transmitted pulses was found to increase as the thickness of the biological tissue increases. The absence of a distinct ballistic pulse transmitted through a relatively thin tissue is in sharp contrast with the pulse transmission through a random medium of discrete scatterers. Because of the continuous variation of the dielectric constant in tissue, the photons undergo scattering through the tissue, travel in various small zigzag least optical paths, and form a broadened early-arriving portion of the transmitted pulse. Even in the absence of a well-defined ballistic pulse, we can image an opaque object hidden inside a tissue as thick as 6.5 mm with submillimeter resolution by selecting the early-arriving portion of the transmitted pulse.
TL;DR: In this article, the response of the tunneling gap of a scanning tunneling microscope to excitation by a sub-picosecond electrical pulse was measured, and the potential of this powerful technique for studying ultrafast dynamical phenomena on surfaces with atomic resolution and mesoscopic electronic device physics was discussed.
Abstract: We have measured the response of the tunneling gap of a scanning tunneling microscope to excitation by a subpicosecond electrical pulse. Combining ultrashort laser pulses techniques with scanning tunneling microscopy (STM), we have obtained simultaneous 2‐ps time resolution and 50‐A spatial resolution. This is a 9 orders of magnitude improvement in the time resolution currently attainable with STM. The potential of this powerful technique for studying ultrafast dynamical phenomena on surfaces with atomic resolution and mesoscopic electronic device physics is discussed.
TL;DR: It is shown that the solitons decay as a result of dispersive radiation, the nature of which is analyzed and the combined effects of fourth-order dispersion and intrapulse Raman scattering are discussed.
Abstract: The effects of fourth-order dispersion on optical-fiber-guided ultrashort solitons are examined. It is shown that the solitons decay as a result of dispersive radiation, the nature of which is analyzed. An exact pulse solution is presented, and its properties are evaluated. Finally, the combined effects of fourth-order dispersion and intrapulse Raman scattering are discussed.
TL;DR: A new technique for determining the complex electric field of an ultrashort light pulse is analyzed and experimentally demonstrated based on the measurement of the spectrally resolved intensity autocorrelation and an iterative procedure of data deconvolution.
Abstract: A new technique for determining the complex electric field of an ultrashort light pulse is analyzed and experimentally demonstrated. It is based on the measurement of the spectrally resolved intensity autocorrelation and an iterative procedure of data deconvolution. This method is shown to be convenient and reliable.
TL;DR: In this article, two-dimensional simulation results are presented for the case of an intense ultrashort laser pulse propagating through an initially neutral high-pressure gas, where the combined effects of diffraction and ionization lead to self-defocusing of the pulse, which reduces the peak intensity from its vacuum value and restricts the maximum achievable plasma density.
TL;DR: In this paper, the spectral gain narrowing was identified as one of the main issues, and a solution was proposed to solve it. But it was only applied to a Ti:sapphire/Nd:silicate glass power chain.
Abstract: Femtosecond pulses in the 50–60-TW power range have been generated at 1064 nm by using the chirped-pulse-amplification technique applied to a Ti:sapphire/Nd:silicate glass (90-mm output aperture) power chain. We have identified the spectral gain narrowing to be one of the main issues, and we show how to solve it.
TL;DR: A new method is described—chronocyclic tomography—for determining the amplitude and phase structure of a short optical pulse, based on measurements of the energy spectrum of the pulse after it has passed through a time–frequency-domain imaging system.
Abstract: We describe a new method—chronocyclic tomography—for determining the amplitude and phase structure of a short optical pulse. The technique is based on measurements of the energy spectrum of the pulse after it has passed through a time–frequency-domain imaging system. Tomographic inversion of these measured spectra yields the time–frequency Wigner distribution of the pulse, which uniquely determines the amplitude and phase structure.
TL;DR: In this article, the authors describe the generation of femtosecond waveforms by using frequency-domain phase-only filters designed by numerical optimization techniques and demonstrate the ability to generate high-quality terahertz-repetition-rate sequences of femto-cond pulses by means of low-loss phase only filtering.
Abstract: We describe generation of shaped femtosecond waveforms by using frequency-domain phase-only filters designed by numerical optimization techniques. The task of filter design for pulse shaping in the time domain is directly analogous to the design of phase-only filters for beam shaping and array generation in the spatial domain. We experimentally tested phase filters that were designed to produce ultrafast square and triangle pulses and femtosecond pulse sequences. Our results demonstrate the ability to generate high-quality terahertz-repetition-rate sequences of femtosecond pulses by means of low-loss phase-only filtering. On the other hand, experiments that tested generation of individual shaped pulses, such as square pulses, were less successful than previous experiments that used simultaneous phase and amplitude filtering. Our results indicate the importance of building increased robustness against variations in the input pulse shape into the phase-only filter design.
TL;DR: In this article, a simple technique for generating a transform-limited optical short pulse with variable repetition rates by using a sinusoidally driven InGaAsP electroabsorption modulator without any optical resonators is presented.
Abstract: The authors propose and demonstrate a simple technique for generating a transform-limited optical short pulse with variable repetition rates by using a sinusoidally driven InGaAsP electroabsorption modulator without any optical resonators. Using the pulse compression effect due to nonlinear attenuation characteristics of the modulator, a transform-limited optical pulse can be generated just with sinusoidal modulation. Theoretical calculations and experimental results show that the pulse shape is very close to the sech/sup 2/ shape, and the pulse width can be easily varied by varying the bias and modulation voltages. Transform-limited optical pulse generation with a minimum pulse width of 11 ps was achieved up to 20-GHz repetition rate. The time-bandwidth product was as small as 0.32. >
TL;DR: In this article, the authors demonstrate a new ultrafast pump-probe technique using terahertz pulses to investigate carrier transport and screening in semiconductors, where the external bias field is screened on a time scale comparable to the duration of the THz pulse, giving rise to changes in the shape and bandwidth of radiated pulses.
Abstract: We demonstrate a new ultrafast pump‐probe technique using terahertz pulses to investigate carrier transport and screening in semiconductors. As an example we have studied the temporal evolution of the local electric field in a dipole antenna, used for generation of ultrafast terahertz pulses. Ultrafast screening effects are shown to be important for both carrier transport and the emission of THz radiation. At high carrier densities the external bias field is screened on a time scale comparable to the duration of the THz pulse, giving rise to changes in the shape and bandwidth of the radiated pulses.
TL;DR: In this article, a 1.5μm tensile-strained quantum-well optical amplifier has been studied by highly nondegenerate four-wave mixing at detuning frequencies up to 1.7 THz, and frequency response data indicate the presence of two ultrafast physical processes with characteristic relaxation lifetimes of 650 fs and <100 fs.
Abstract: Ultrafast dynamics in a 1.5‐μm tensile‐strained quantum‐well optical amplifier has been studied by highly nondegenerate four‐wave mixing at detuning frequencies up to 1.7 THz. Frequency response data indicate the presence of two ultrafast physical processes with characteristic relaxation lifetimes of 650 fs and <100 fs. The longer time constant is believed to be associated with the dynamic carrier heating effect. This is in agreement with previous time‐domain pump‐probe measurements using ultrashort optical pulses.
TL;DR: A detailed analysis of an efficient multipass Ti:sapphire amplifiers for femtosecond chirped-pulse amplification and its advantages in terms of its high quantum yield, flexibility, optical quality, and potential for tunability is presented.
Abstract: We have developed efficient multipass Ti:sapphire amplifiers for femtosecond chirped-pulse amplification. With only two of these devices we get an amplification factor of 108, which corresponds to a peak power of ~0.5 TW after compression. We present a detailed analysis of such a system and its advantages in terms of its high quantum yield (0.3), flexibility, optical quality, and potential for tunability.
TL;DR: Laser-diode-driven all-optical switching is demonstrated with an As2S3-based glass fiber only 2 m long and assistance from an erbium-doped fiber amplifier to control ultrafast pulse trains with low timing jitter.
Abstract: Laser-diode-driven all-optical switching is demonstrated with an As2S3-based glass fiber only 2 m long and assistance from an erbium-doped fiber amplifier. The laser-diode operation makes it easy to control ultrafast pulse trains with low timing jitter. Ultrafast switching at as much as 80-GHz repetition rates is successfully demonstrated. The nonlinear refractive index of the fiber is estimated to be 9.3 × 10−15 (cm2/W) at a 1.55-μm wavelength.
TL;DR: The simplicity, high energy, short pulse widths, and variable repetition rate of the mode-locked Ti:A1(2)O(3) laser system make it an attractive tunable source for ultrafast measurements.
Abstract: We report the generation of pulses with energies as high as 100 nJ and durations as short as 50 fs directly from a mode-locked Ti:A1(2)O(3) laser, using the technique of cavity dumping. The simplicity, high energy, short pulse widths, and variable repetition rate of this system make it an attractive tunable source for ultrafast measurements.
TL;DR: Focusing of ultrashort light pulses with single lenses is analyzed by taking into account the unavoidable interplay between chromatic and spherical aberration simultaneously for the first time to the authors' knowledge.
Abstract: Focusing of ultrashort light pulses with single lenses is analyzed by taking into account the unavoidable interplay between chromatic and spherical aberration simultaneously for the first time to our knowledge. The spatial intensity distribution is mainly affected by spherical aberration, whereas the temporal distribution is determined by both aberrations. The impact on second-harmonic generation for femtosecond pulse measurements is discussed. For example, the presence of spherical aberration allows one to record the correct autocorrelation of a 10-fs pulse even if chromatic aberration alone would cause a half-width of the autocorrelation function of 40 fs.
TL;DR: In this article, a two-color stimulated Raman effect was used to generate a shorter optical pulse at terawatt levels based on a simple optical system, which is essential in studies on ultrafast phenomena and nonlinear spectroscopy.
TL;DR: A femtosecond upconversion apparatus was used to measure the fluorescence decay in the PSI core antenna of a PSI-only mutant of Chlamydomonas reinhardtii.
TL;DR: Passive mode locking initiated with a moving mirror is demonstrated in a neodymium fiber laser for what is to the authors' knowledge the first time.
Abstract: Passive mode locking initiated with a moving mirror is demonstrated in a neodymium fiber laser for what is to our knowledge the first time Near-bandwidth-limited pulses with a width of 42 fs and energies as high as 1 nJ are generated