Showing papers on "Pulse compression published in 2001"
TL;DR: The nonlinear pulse propagation in photonic crystal fibers without slowly varying envelope approximation is studied using an improved variant of first-order wave equation and good agreement with experimental observations is found.
Abstract: The nonlinear pulse propagation in photonic crystal fibers without slowly varying envelope approximation is studied using an improved variant of first-order wave equation. Supercontinuum generation is shown to be caused by a novel mechanism of spectral broadening through fission of higher-order solitons into redshifted fundamental solitons and blueshifted nonsolitonic radiation. Good agreement with experimental observations is found, and subcycle pulse compression is studied.
751 citations
TL;DR: Spectral interference between a white-light continuum generated in a hollow-fiber and its second harmonic is demonstrated and shot-by-shot changes of the carrier-envelope phase are estimated.
Abstract: We demonstrated single-shot measurements of spectral interference between a white-light continuum generated in a hollow-fiber and its second harmonic. The interference has information on the carrier-envelope phase of an input pulse to the fiber and the time delay of the blue wing of the continuum. By analyzing the observed spectral interference, we estimated shot-by-shot changes of the carrier-envelope phase. This method is useful for determining the carrier-envelope phase changes of a low-repetition-rate, high-intensity laser.
240 citations
TL;DR: Capacitance transducers were used to generate wide bandwidth swept-frequency signals in air, which were then used to measure and image solid samples in through transmission, demonstrating that such signal processing techniques lead to an improvement in the signal to noise ratio and timing accuracy for air-coupled testing.
206 citations
TL;DR: Double-chirped mirrors with custom-tailored dispersion characteristics over a bandwidth of 170 THz in the visible are reported on, characterized for the what is believed to be first time by use of the spectral phase interferometry for direct electric field reconstruction technique.
Abstract: We report on double-chirped mirrors with custom-tailored dispersion characteristics over a bandwidth of 170 THz in the visible. The mirrors are used in a prismless compressor for a noncollinear optical parametric amplifier in the visible. The compressed pulses, characterized for the what is believed to be first time by use of the spectral phase interferometry for direct electric field reconstruction technique, display a nearly flat phase from 510 to 710 nm and have a duration of 5.7 fs.
114 citations
01 May 2001
TL;DR: A novel binary phase coding scheme for radar pulse compression, derived from the logistic-map equation in the chaotic theory, which makes it feasible to achieve superior performance in detection range and improve the Doppler tolerance.
Abstract: This paper presents a novel binary phase coding scheme for radar pulse compression, which is derived from the logistic-map equation in the chaotic theory. The proposed logistic-map-based binary phase code (LMBPC) makes it feasible to achieve superior performance in detection range. The logistic-map equation in the chaotic theory is range resolution and Doppler tolerance simultaneously. The properties of LMBPC, including autocorrelation function, ambiguity diagram, performance under various noisy backgrounds, and the maximum Doppler tolerance, have been analyzed and compared to those of the conventional schemes, such as linear FM. The properties of LMBPC are very similar to those of the random binary codes. However, the generation of LMBPC is much simpler, and the available LMBPC is virtually infinite and not limited by the length of code. A parallel correlator structure for the pulse compression filter has also been introduced, which serves to improve the Doppler tolerance.
65 citations
TL;DR: In this article, the use of broad-band chirp signals for spread-spectrum communications in indoor and industrial environments is reported, where the well-known pulse compression technique associated with chirPulse compression technique is exploited to achieve a highly robust communication system.
Abstract: We report on the use of broad-band chirp signals for spread-spectrum communications in indoor and industrial environments. The well-known pulse compression technique associated with chirp signals is exploited to achieve a highly robust communication system. For the generation and compression of the chirp signals, surface acoustic wave delay lines fabricated from an LiTaO/sub 3/-X112rotY substrate are used. Center frequency, bandwidth, chirp duration, and chirp rate are 348.8 MHz, 80 MHz, 500 ns, and /spl plusmn/40 MHz//spl mu/s, respectively. Different modulation schemes for chirp signals are introduced, the effects of nonlinearities, frequency drift, and temperature drift are addressed, and simulations and measurement results from a hardware demonstrator are presented for the use of /spl pi//4-differential quadrature phase-shift keying (DQPSK) modulation. A data rate of up to 40 Mb/s has been achieved experimentally and shows that the proposed system is highly robust against multipath effects.
63 citations
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.
63 citations
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.
57 citations
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.
55 citations
TL;DR: A self-starting stretched-pulse mode-locked erbium-doped fiber laser that uses fast and slow semiconductor saturable absorbers that obtained reliable operation at a fundamental repetition rate with 250 pJ of pulse energy without multiple-p pulse breakup.
Abstract: A self-starting stretched-pulse mode-locked erbium-doped fiber laser that uses fast and slow semiconductor saturable absorbers is described. By using two absorbers, we obtained reliable operation at a fundamental repetition rate with 250 pJ of pulse energy without multiple-pulse breakup. External chirp compensation was used to compress the highly chirped pulses to durations of 135 fs.
54 citations
TL;DR: A 10-GHz train of nearly transform-limited 54-fs soliton pulses was generated by adiabatic compression of the output of a mode-locked fiber laser with a polarization-maintaining dispersion-flattened dispersion -decreasing fiber.
Abstract: A 10-GHz train of nearly transform-limited 54-fs soliton pulses was generated by adiabatic compression of the output of a mode-locked fiber laser with a polarization-maintaining dispersion-flattened dispersion-decreasing fiber. The peak-to-pedestal ratio exceeded 23 dB. At high input powers, the pulse width was reduced to as short as 43 fs, although the wings of the pulse were degraded and the jitter increased. The compression properties are different for the two polarization axes, owing to their different dispersion characteristics. The output polarization exhibits no drift.
TL;DR: These are the shortest pulses ever generated in the blue spectral region by frequency doubling of 8.6-fs Ti:sapphire laser pulses generated in a nonlinearly chirped quasi-phase-matching grating fabricated in a lithium tantalate substrate.
Abstract: We demonstrate the generation of sub-6-fs pulses centered at 405 nm by frequency doubling of 86-fs Ti:sapphire laser pulses The frequency doubling is carried out in a nonlinearly chirped quasi-phase-matching grating fabricated in a lithium tantalate substrate This device simultaneously provides frequency conversion and pulse compression of the positively prechirped fundamental pulses The second-harmonic pulses are characterized in a cross-correlation setup, and their pulse shapes are retrieved by two iterative phase-reconstruction algorithms The generated second-harmonic spectrum spans a bandwidth of 220 THz To our knowledge, these are the shortest pulses ever generated in the blue spectral region
TL;DR: In this paper, a pilot-scale pulsed corona discharge process was applied to the treatment of industrial flue gas from an iron-ore sintering plant, where a two-stage magnetic pulse compression modulator whose average power is 40kW was used to produce repetitive high voltage pulse.
TL;DR: In this paper, a noncollinear sum-frequency generation in β-barium borate crystals is investigated for pulse compression through non-collined sumfrequency generation with dispersion to all orders.
Abstract: Pulse compression through noncollinear sum-frequency generation in β-barium borate crystals is investigated. With dispersion to all orders taken into account, numerical calculations, carried out in the frequency domain, were performed for input pulse durations ranging from 10 to 50 fs. Fundamental pulses of a 10-fs duration at 800 nm were compressed down to 2.5 fs while a 2.5-fs second-harmonic signal was generated.
TL;DR: In this paper, a synchronously pumped optical parametric oscillator (OPO) employing periodically poled lithium niobate (PPLN) efficiently generates diffraction-limited short pulses that are tunable in the 1.45-1.56-µm spectral range, with their duration adjustable from ≈1 ps-15 ps and output power as high as 630 mW.
Abstract: A synchronously pumped optical parametric oscillator (OPO) employing periodically poled lithium niobate (PPLN) efficiently generates diffraction-limited short pulses that are tunable in the 1.45–1.56-µm spectral range, with their duration adjustable from ≈1 ps–15 ps and output power as high as 630 mW. The pump laser that produces these unique OPO characteristics is a 200-MHz, 2.5-W average power, diode-pumped Nd:YVO4 laser emitting at 1064 nm and passively mode locked by a nonlinear mirror (NLM) technique. One can select the output pulse width from the vanadate laser to be either 16 or 6 ps simply by choosing the appropriate NLM configuration. Significantly enhanced performance of the mode-locked Nd:YVO4 laser was obtained with a critically phase-matched type I LiB3O5 crystal. A comparison of this crystal with type II KTiOPO4 is reported.
TL;DR: In this article, a femtosecond optical parametric oscillator with linearly chirped gratings was used for simultaneous frequency doubling and pulse compression of chirping pulses.
Abstract: We present detailed experimental results of simultaneous frequency doubling and pulse compression of chirped pulses from a femtosecond optical parametric oscillator using a second-harmonic crystal of aperiodically poled lithium niobate comprising eight different linearly chirped gratings. Our results are compared with a numerical model that incorporates the complex amplitude of the input pulse determined with frequency-resolved optical gating. We use the results of this model to analyze and discuss several aspects of the pulse-generation process.
Patent•
15 Jun 2001
TL;DR: In this article, a first spread spectrum signal is converted to the ultrasound signal at one or more transducers, and the ultrasound signals are transmitted to the object, followed by a second step, pulse compression is performed on a reflected signal of the signal reflected from the object to form a pulse compressed signal.
Abstract: An ultrasound imaging method forms an image of an object using signals reflected from the object after transmitting an ultrasound pulse to the object. In the method, at a first step, a predetermined first spread spectrum signal is converted to the ultrasound signal at one or more transducers and the ultrasound signal is transmitted to the object. At a second step, pulse compression is performed on a reflected signal of the ultrasound signal reflected from the object to form a pulse compressed signal. And the pulse compressed signal is processed to produce a receive-focused signal and the image of the object from the receive-focused signal is generated.
TL;DR: In this paper, a pulse compression method is proposed to simulate the propagation of a pulse in an inhomogeneous plasma, which allows very fast computations compared to the usual time-dependent code.
17 Mar 2001
TL;DR: Parabolic pulses are generated from ultrashort pulse amplification in a high gain normal dispersion fiber amplifier as mentioned in this paper, which can be conveniently generated in a fiber laser configuration and is robust against interactions and collisions.
Abstract: Parabolic pulses are generated from ultrashort pulse amplification in a high gain normal dispersion fiber amplifier. The pulses are robust against interactions and collisions and can be conveniently generated in a fiber laser configuration.
Patent•
02 Aug 2001
TL;DR: In this article, the power control or regulation is performed by varying the pulse repetition frequency and/or the pulse duration of the transmitter pulses, which is well suited for operating a motor vehicle range warning system.
Abstract: A radar system is operated by controlling and thereby limiting the mean power of the transmitted signal in response to the mean power of the received signal thereby limiting the power to a predetermined power range. Preferably the power control or regulation is performed by varying the pulse repetition frequency and/or the pulse duration of the transmitter pulses. This method is well suited for operating a motor vehicle range warning system.
TL;DR: In this paper, an imaging system that applies FM-chirp pulse compression technology for use in intraductal ultrasonography, or intravascular ultrasonograph, was developed.
Abstract: We have developed an imaging system that applies FM-chirp pulse compression technology for use in intraductal ultrasonography, or intravascular ultrasonography. The pulse compression technique attempts to raise resolving power by using average power effectively under peak power restriction. This paper describes a method that use pulse compression technology in intravascular ultrasonography. In this paper, the following are reported: 1) A method to use the FM-chirp pulse compression technique in an imaging system is proposed. 2) A transmission line suited for intravascular ultrasonography is constructed using the L(0, 1) mode of the Pochhmmer-Chree wave propagating in a fused quartz rod coated with carbon. 3) A receiving signal from a target is compressed to give a shot pulse.
TL;DR: In this paper, the authors demonstrate stimulated Brillouin scattering compression of diode-pumped Nd:YAG laser pulses with a 3ns duration into 350-ps pulses at a pulse-repetition rate of 100 Hz for what is believed to be the first time.
Abstract: We demonstrate stimulated Brillouin scattering compression of diode-pumped Nd:YAG laser pulses with a 3-ns duration into 350-ps pulses at a pulse-repetition rate of 100 Hz for what is believed to be the first time. The output pulse energy was 6.5 mJ, with a beam-quality factor M(2) of 1.15, and after final amplification the energy reached 36 mJ, with M(2) of 2.5.
TL;DR: A novel ultrawide self-phase modulation-induced spectral-broadening regime with spectra covering almost 3 octaves is predicted for a pressure at which the group-velocity dispersion parameter is small and anomalous.
Abstract: We present a theoretical study of temporal and spectral characteristics and pulse compression in hollow waveguides, using a global approach to dispersion without application of the slowly varying envelope approximation. A novel ultrawide self-phase modulation–induced spectral-broadening regime with spectra covering almost 3 octaves is predicted for a pressure at which the group-velocity dispersion parameter is small and anomalous. Compression to subcycle pulses by an appropriate broadband modulator and pulse shortening without chirp control by a spectral filter are studied.
25 Jan 2001
TL;DR: In this paper, the effect of perfect crystal dynamical diffraction of ultrashort x-ray pulses when the pulse lengths become comparable to the extinction length scales has been investigated.
Abstract: X-ray free-electron lasers (XFELs) designed to operate at approximately 1A wavelengths are currently being proposed by several laboratories as the basis for the next (4th) generation of synchrotron radiation sources The unique radiation properties of these proposed sources, which include 200 fs pulse duration and peak beam brilliance in excess of 1033 photon (2 1%-bw mrad2 mm2), offer the possibility of ultrafast time-resolved experiments, perhaps down to 10- fs resolution levels using pulse compression or slicing techniques Motivated by such potential applications, this paper addresses the relevant instrumentation issue of perfect crystal dynamical diffraction of ultrashort x-ray pulses when the pulse lengths become comparable to the extinction length scales The basic calculations reported here show the transient time-dependent diffraction from perfect crystals excited by plane-wave delta-function electromagentic impulses Time responses have been calculated for 8 keV photon energy, for reflected and transmitted beams in both Bragg and Laue cases Interesting diffraction effects arise, and their implications for XFEL optics are discussed© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only
TL;DR: In this article, a repetitive pulsed power generator was constructed with the semiconductor opening switch realizing the pulse compression by an inductive energy storage system, where saturable inductors and transformers were used to transfer the electrical energy from the primary storage capacitor to the load compressing the pulse.
Abstract: The repetitive pulsed power generator was constructed with the semiconductor opening switch realizing the pulse compression by an inductive energy storage system. For the preliminary pulse compression, the magnetic pulse compression system was employed. The saturable inductors and transformers were used to transfer the electrical energy from the primary storage capacitor to the load compressing the pulse. For the final output of the generator, the semiconductor opening switch (SOS) was used. The SOS assembly used in the system consists of 80 diodes that were designed to conduct high reverse current and have short reverse recovery time. By tuning the current fed to the SOS, the amplitude and pulse width of the generated voltage at the 300 Ω resistive load were 150 kV and 60 ns, respectively. Although the present generator system operates repetitively, the system has no triggered gas-discharge or semiconductor closing switch. Also, all the devices used in the system are in solid sate. The system provides stable operation and long lifetime.
TL;DR: In this paper, nonlinear pulse compression and pulse broadening with a coherent array of submicron silica spheres embedded with silicon and germanium nanoparticles (nano within a nano).
Abstract: Nonlinear pulse compression and pulse broadening have been analyzed and demonstrated with a coherent array of submicron silica spheres embedded with silicon and germanium nanoparticles (nano within a nano).
TL;DR: It is shown that phase-locked pulses as short as 3 fs can be generated by coherent scattering in impulsively excited Raman media without the necessity of external phase control.
Abstract: It is shown that phase-locked pulses as short as 3 fs can be generated by coherent scattering in impulsively excited Raman media without the necessity of external phase control. The underlying mechanism, temporal characteristics, spectra, phase relations, physical limitations owing to competition processes, and precompensation of dispersion by the hollow waveguide window are studied analytically and numerically without the use of the slowly varying envelope approximation and with a global approach to dispersion. Additionally, the large frequency shifts in both the Stokes and anti-Stokes directions of as much as half the carrier frequency raise the possibility of generating widely tunable ultrashort pulses.
TL;DR: In this paper, a new theoretical model, without the first-order approximation of grating diffraction, has been developed for studying the propagation of a pulsed beam through a grating pair.
Abstract: A new theoretical model, without the first-order approximation of grating diffraction, has been developed for studying the propagation of a pulsed beam through a grating pair. By using our model, the astigmatic aberration of the grating pair has been analyzed in detail. It was shown that the grating pair may be a good optical element for astigmatic compensation of monochromatic optical beams. But for grating pulse compression, the astigmatic aberration affects the pulse fronts and the effects of finite beam size (FBS). These effects on the compression of ultra-broadband pulses have been studied. It was found that, due to these effects, the space-time shapes of the compressed pulse are severely distorted. The magnitude of this distortion depends not only on the astigmatic aberration, but also on the spectral bandwidth and spatial divergence of the pulse. When the input pulsed beam is collimated, the waveform distortion due to the effects of FBS can be eliminated, but the pulse front distortion remains. In addition, the spatial and temporal properties of the compressed pulse for a single-pass compressor have been studied. An analytical expression without the well-collimated condition was obtained to describe the effect of lateral frequency shift. Also, the effect of third-order dispersion on a single-pass compressor is discussed.
09 Jul 2001
TL;DR: In this paper, two alternative methods are discussed based on phase-coding and orthogonal waveforms, where the received pulses are correlated with the phase code sequence, and by varying the delay of the phase codes, the subintervals in range are scanned and reflector responses outside the focused range interval become highly suppressed.
Abstract: In Doppler radar for surveillance and remote sensing, the ambiguities in range/Doppler are usually solved by varying the pulse repetition frequency. In this paper, two alternative methods are discussed based on phase-coding and orthogonal waveforms. The first one distributes a phase code over a pulse sequence with only one phase step per pulse. The received pulses are correlated with the phase code sequence, and by varying the delay of the phase code, the subintervals in range are scanned and reflector responses outside the focused range interval become highly suppressed. The alternative method that was studied applies a set of near-orthogonal phase codes, which modulate the pulses transmitted. In the receiver, the different subintervals in range are scanned, or detected in parallel, by correlating the signal from the scene by the delayed code sequence of the pulse transmitted. Because orthogonal codes are used, a strong suppression is achieved for signals originating outside the focused subinterval in range.
01 May 2001
TL;DR: Results indicate Gold-coded waveforms offer significant improvement in radar clutter suppression, resolution, and unambiguous range properties.
Abstract: This paper presents analytic, simulation, and measured results of using Gold sequences for radar pulse compression coding. Gold-coded waveform performance is characterized using the ambiguity function diagram, synonymous with matched filtering performance. Results indicate Gold-coded waveforms offer significant improvement in radar clutter suppression, resolution, and unambiguous range properties.