Showing papers on "Femtosecond pulse shaping published in 1996"
02 Jun 1996
TL;DR: In this article, a novel laser pulse compression technique for Ti:sapphire chirped pulse laser amplifiers, based on spectral broadening in a hollow cylindrical quartz fiber filled with noble gases at high pressure, was presented.
Abstract: Summary form only given. In this work, we present a novel laser pulse compression technique for Ti:sapphire chirped pulse laser amplifiers, based on spectral broadening in a hollow cylindrical quartz fiber filled with noble gases at high pressure, which is suitable for high-energy pulses. Pulse recompression is then achieved using two conventional quartz prism pairs.
957 citations
Journal Article•
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TL;DR: Pulse wave analysis has been an important part of the medical examination from ancient times as discussed by the authors, and it has been used to detect asymptomatic hypertension and to chart the natural history of essential hypertension and distinguish between this condition and chronic nephritis.
Abstract: PULSE WAVE ANALYSIS IN HISTORICAL TIMES: Interpretation of the arterial pulse has been an important part of the medical examination from ancient times. Graphic methods for clinical pulse wave recording were introduced by Marey in Paris and by Mahomed in London last century. Mahomed showed how such recordings could be used to detect asymptomatic hypertension, and used them to chart the natural history of essential hypertension and to distinguish between this condition and chronic nephritis. Interest in arterial pulse analysis, as applied by Mahomed, lapsed with the introduction of the cuff sphygmomanometer 100 years ago. MODERN PULSE WAVE ANALYSIS: Analysis of the arterial pulse is now regaining favour as limitations of the cuff sphygmomanometer are better recognized (including the ability only to measure extremes of the pulse in the brachial artery). In addition, high-fidelity tonometers have been introduced for very accurate, non-invasive measurement of arterial pulse contour, and there is now a better understanding of arterial hemodynamics, and appreciation of disease and aging effects in humans. It is now possible to record the pulse wave accurately in the radial or carotid artery, to synthesize the ascending aortic pulse waveform, to identify systolic and diastolic periods and to generate indices of ventricular-vascular interaction previously only possible with invasive arterial catheterization. Pressure pulse wave analysis now permits more accurate diagnosis and more logical therapy than was ever possible in the past.
392 citations
Book•
24 May 1996
TL;DR: In this article, the authors present a reconstruction of the Spectral Phase of a femtosecond light-matter system, including the phase shifts upon transmission-reflection, and four Photon Coherent Interaction.
Abstract: Fundamentals. Femtosecond Optics. Light-Matter Interaction. Coherent Phenomena. Ultrashort Sources. Femtosecond Pulse Amplification. Pulse Shaping. Diagnostic Techniques. Measurement Techniques. Examples of Ultrafast Processes in Matter. Extreme Wavelengths. Phase Shifts Upon Transmission-Reflection. F's Dye Laser Configuration. Four Photon Coherent Interaction. Dyes and Solvents. Reconstruction of the Spectral Phase.
377 citations
TL;DR: It is shown that frequency-resolved optical gating combined with spectral interferometry yields an extremely sensitive and general method for temporal characterization of nearly arbitrarily weak ultrashort pulses even when the reference pulses is not transform limited.
Abstract: We show that frequency-resolved optical gating combined with spectral interferometry yields an extremely sensitive and general method for temporal characterization of nearly arbitrarily weak ultrashort pulses even when the reference pulses is not transform limited. We experimentally demonstrate measurement of the full time-dependent intensity and phase of a train of pulses with an average energy of 42 zeptojoules (42 × 10−21 J), or less than one photon per pulse.
254 citations
TL;DR: Transform-limited, 18-fs pulses of 4.4-TW peak power are produced in a Ti:sapphire-based chirped-pulsed amplification system at a repetition rate of 50 Hz to control gain narrowing and higher-order phase distortions over a bandwidth of ~100 nm.
Abstract: Transform-limited, 18-fs pulses of 44-TW peak power are produced in a Ti:sapphire-based chirped-pulsed amplification system at a repetition rate of 50 Hz Regenerative pulse shaping is used to control gain narrowing during amplification, and an optimized, quintic-phase-limited dispersion compensation scheme is used to control higher-order phase distortions over a bandwidth of ~100 nm Seed pulses are temporally stretched >100, 000 times before amplification
178 citations
TL;DR: This novel regenerative amplifier has been used to amplify pulses to the 5-mJ level with a bandwidth sufficient to support ~ 10-fs pulses, nearly three times wider than the traditional gain-narrowing limit.
Abstract: Regenerative pulse shaping is used to alleviate gain narrowing during ultrashort-pulse amplification. Amplification bandwidths of ~100 nm, or nearly three times wider than the traditional gain-narrowing limit, are produced with a modified Ti:sapphire regenerative amplifier. This novel regenerative amplifier has been used to amplify pulses to the 5-mJ level with a bandwidth sufficient to support ~10-fs pulses.
176 citations
TL;DR: Nonlinear pulse evolution is studied for a fiber with normal dispersion (ND) and gain, and numerical simulations show that under certain conditions the pulse evolves into a parabolic shape, which has been shown to reduce optical wave breaking.
Abstract: Nonlinear pulse evolution is studied for a fiber with normal dispersion (ND) and gain. Numerical simulations show that under certain conditions the pulse evolves into a parabolic shape, which has been shown to reduce optical wave breaking. Much as with the square pulse that forms in passive fibers with ND, the interplay of ND and self-phase modulation creates a highly linear chirp, which can be efficiently compressed. Application to an amplifying fiber/grating (prism) pair pulse compressor is considered, with an experimental demonstration of compression from 350 to 77 fs at a gain of 18 dB in an erbium-doped fiber amplifier.
157 citations
TL;DR: This technique permits the determination of the temporal shape of the THz pulse in the picosecond time domain and offers the exciting prospect of up-converting the spatial THzbeam profile into the optical wavelength range in real time, with potential application in diagnostics.
Abstract: Freely propagating THz pulses are recorded in a thin lithium tantalate crystal by monitoring the phase retardation of a femtosecond probe pulse. This technique permits the determination of the temporal shape of the THz pulse in the picosecond time domain and offers the exciting prospect of up-converting the spatial THz beam profile into the optical wavelength range in real time, with potential application in diagnostics.
150 citations
TL;DR: In this paper, the characteristics of the radiation are studied and the radiation mechanism is ascribed to the ultrafast supercurrent modulation by the laser pulses, which induce the nonequilibrium superconductivity.
Abstract: Ultrashort electromagnetic waves (600 fs width) from superconducting YBCO thin films have been observed by irradiating current‐biased samples with femtosecond optical laser pulses (80 fs width). The Fourier component of the pulse extends up to ∼2 THz. The characteristics of the radiation are studied and the radiation mechanism is ascribed to the ultrafast supercurrent modulation by the laser pulses, which induce the nonequilibrium superconductivity.
139 citations
TL;DR: In this paper, a single phase shaped femtosecond laser pulse was used to control molecular multiphoton ionization by a single-phase femto-cond (FSH) laser pulse.
124 citations
TL;DR: In this article, it was shown that a necessary and sufficient condition for the characterization of an ultrashort pulse shape is that the apparatus consist of at least one time nonstationary and one time stationary element.
Abstract: Some general conditions concerning the properties of apparatuses that can measure completely the amplitude and the phase of a pulse’s electric field by using a slow detector are formulated. In particular, it is shown that a necessary and sufficient condition for the characterization of an ultrashort pulse shape is that the apparatus consist of at least one time nonstationary and one time stationary element. We show that there are only four possible noninterferometric schemes that meet this criterion. We discuss separately these four minimal methods and the associated algorithms for reconstructing the pulse shape from the measured data.
TL;DR: In this paper, the principles of free-space terahertz waveform synthesis were described by using a programmable optical pulse shaper to drive a photoconducting dipole antenna.
Abstract: We describe the principles of free-space terahertz waveform synthesis by using a programmable optical pulse shaper to drive a photoconducting dipole antenna We illustrate this technique using several experimental examples, including manipulation of the amplitude and the phase of ultrafast terahertz waveforms as well as generation of ultrafast bit sequences at terahertz frequencies We present a theory which accurately predicts the shapes of the terahertz waveforms produced in our experiments In addition to the controllability of terahertz radiation, we have shown that optical pulse shaping can be used to avoid saturation of the terahertz field at high-peak power and increase generation efficiencies for terahertz radiations at selected, narrow-band frequencies
TL;DR: In this paper, the supercurrent transient is created by the excitation of the supercarriers into quasiparticles with a femtosecond laser pulse, and freely propagated electromagnetic pulses are measured and characterized.
Abstract: We have observed ultrashort electromagnetic pulse radiation from YBa2Cu3O7-δ thin-film dipole antennas. The supercurrent transient is created by the excitation of the supercarriers into quasiparticles with a femtosecond laser pulse, and freely propagated electromagnetic pulses are measured and characterized. A pulse with 0.5 ps full width at half-maximum was obtained, containing frequency components up to 2.0 THz. A femtosecond time-resolved characterization of the spectra revealed that they strongly depend on the excitation conditions, and the quasiparticle recombination time becomes longer with increase in the excitation intensity. It is also observed that the radiation power increases in proportion to the square of both the bias current and the laser power in the region of weak excitation, which is consistent with the classical theory based on a two-fluid model. In the region of strong excitation, deviation from the classical theory was observed.
TL;DR: It is observed that the harmonic spectrum of argon taken with laser pulses contains harmonics up to 20 orders higher than for 100 fs laser pulses with the intensity, and it is shown that this increase in harmonics is because the atom survives to intensities.
Abstract: High-harmonic generation using ultrashort laser pulses with pulse durations 25 to 200 fs is s theoretically and experimentally. We observe that the harmonic spectrum of argon taken with laser pulses contains harmonics up to 20 orders higher than for 100 fs laser pulses with the intensity. We show that this increase in harmonics is because the atom survives to highe intensities, due in part to the nonadiabatic response of the atomic dipole to the fast rise time pulse. [S0031-9007(96)01018-6]
TL;DR: The use of optical pulse shaping is reported to convert single femtosecond pulses into lower-intensity pulse sequences for excitation of photoconductive dipole antennas, which results in the generation of bursts of tunable narrow-band free-space terahertz radiation.
Abstract: We report the use of optical pulse shaping to convert single femtosecond pulses into lower-intensity pulse sequences for excitation of photoconductive dipole antennas, which results in the generation of bursts of tunable narrow-band free-space terahertz radiation. Our experiments demonstrate that the use of such pulse sequences can significantly enhance the spectral amplitude of the narrow-band terahertz radiation by avoiding the saturation effects that occur with single-pulse excitation. Our technique also provides the capability for terahertz wave-form shaping.
TL;DR: In this article, a pulse-rate-tunable, highly extinctive, ultra-high-speed electrooptic pulse pattern generator was developed, which is based on sinusoidal phase modulation and linear chirp compensation.
Abstract: A pulse-rate-tunable, highly extinctive, ultra-highspeed electrooptic pulse pattern generator has been developed. The optical short pulse generation is based on sinusoidal electrooptic phase modulation and linear chirp compensation using a dispersive medium. Filtering the nonlinear chirp components generated by sinusoidal phase modulation drastically improves the pulse extinction, and makes nearly background-free picosecond pulsation over a wide pulse-rate range even when the group delay dispersion value is fixed.
TL;DR: In this article, the principle of operation and performance of several soliton pulse sources and also a complete soliton transmitter based on lithium niobate modulators are described, and the performance of this compact transmitter in a 2.5-Gb/s system experiment is comparable to other more common soliton transmitters.
Abstract: We describe the principle of operation and performance of several soliton pulse sources and also a complete soliton transmitter based on lithium niobate modulators. Subsystems based on lithium niobate modulators are attractive because the modulators are now commercially available, qualified for system use, can operate up to very high speeds, and can operate over a wide wavelength range. The pulse sources we describe are based on two techniques. The first is the chirped pulse compression technique in which one or two sinusoidally driven modulators generate frequency chirped pulses that are subsequently compressed to the desired width using dispersion in a fiber. In the second technique, sinusoidally driven modulators are cascaded serially to form pulses. Using these techniques we produced nearly transform-limited pulses at repetition rates up to 15 GHz with a FWHM pulsewidths from 10-33% of the pulse period. A complete soliton transmitter using a single modulator to simultaneously generate optical pulses and encode data is also discussed. The performance of this compact transmitter in a 2.5-Gb/s soliton system experiment is comparable to other more common soliton transmitters.
NEC1
TL;DR: In this paper, an ultra-high-frequency optical pulse train from a monolithic mode-locked laser diode was stabilized by a novel method, and the output was harmonically synchronized and highly stabilized.
Abstract: An ultrahigh-frequency optical pulse train from a monolithic mode-locked laser diode was stabilized by a novel method. When a stabilized optical pulse train was injected into a passively mode-locked laser diode whose repetition frequency was an integer multiple of the injected one, the output optical pulse train was harmonically synchronized and highly stabilized. This kind of operation was observed up to 40 GHz with 1 GHz optical pulse injection.
TL;DR: It is found that space-time focusing of the pulse within the laser crystal imposes a limitation on the pulse duration as a function of the crystal length, so good compensation of the net group-velocity dispersion of the cavity is not sufficient for successful sub-10-fs operation of the laser.
Abstract: We present results of a three-dimensional model of a Kerr-lens mode-locked titanium-doped sapphire laser in the sub-10-fs regime of operation. We find that space–time focusing of the pulse within the laser crystal imposes a limitation on the pulse duration as a function of the crystal length. Thus good compensation of the net group-velocity dispersion of the cavity is not sufficient for successful sub-10-fs operation of the laser. The dependence of the pulse duration on the intracavity dispersion is also presented, which demonstrates that pulses as short as 6 fs can be generated directly from the laser.
Patent•
18 Nov 1996
TL;DR: In this paper, a variable pulse width lasing device for selectively reducing the amount of laser energy provided during a surgical procedure, is described, which includes a central processing unit (24), a laser resonator (16), pulse width detector (66), and a pulse modulator (14).
Abstract: A variable pulse width lasing device (10) for selectively reducing the amount of laser energy provided during a surgical procedure, is described. The device includes a central processing unit (24), a laser resonator (16), pulse width detector (66), and a pulse modulator (14). The central processing unit (24) provides a switch activation command to the modulator (14). The modulator also receives a laser pulse produced by the laser resonator (16) which has an initial pulse width, and a wavelength which is compatible for transmission through an optical fiber. The modulator varies the width of the laser pulse for providing an output pulse (78) at a selected pulse width and energy level.
TL;DR: Simultaneous temporal and spatial shaping of ultrashort optical pulses is demonstrated, using a two-dimensional mask pattern to filter spatially separated frequency components along one coordinate and impart a shaped spatial profile along the perpendicular coordinate, yielding a spatially and temporally coherent output waveform.
Abstract: Simultaneous temporal and spatial shaping of ultrashort optical pulses is demonstrated. A two-dimensional mask pattern is used to filter spatially separated frequency components along one coordinate and to impart a shaped spatial (or wave-vector) profile along the perpendicular coordinate, yielding a spatially and temporally coherent output waveform. As an example, a single input pulse is transformed into 11 spatially separated output beams, each with an independently specified temporal profile.
TL;DR: In this article, the femtosecond pulses were generated from a continuous-wave (CW) narrow linewidth laser by using the chirping compression method with a highly efficient electrooptic phase modulator.
Abstract: Ultrashort optical pulses in the femtosecond range were generated from a continuous-wave (CW) narrow linewidth laser by using the chirping compression method with a highly efficient electrooptic phase modulator. Before the femtosecond pulse generation, a high modulation index electrooptic modulator specially designed was fabricated by employing the quasi-velocity-matching. In the pulse generation experiment, the electrooptic modulator and a grating pair as a negative group delay dispersion element were used for a 514.5-nm CW Ar laser. As a result, the sideband spectrum of 2.0 THz full-width half-maximum (FWHM) was produced and 560-fs optical pulses with 16.25-GHz repetition rate was successfully obtained. For this electrooptic pulse compression method is applicable to the negative group delay dispersion element as well as the positive group delay dispersion.
TL;DR: In this article, the entire power spectrum of a continuously operating actively mode-locked laser in the presence of noise is analyzed and the effect of amplitude, pulse-shape, and timing-jitter fluctuations that are characterized by stationary processes is studied.
Abstract: We analyze the entire power spectrum of pulse trains generated by a continuously operating actively mode-locked laser in the presence of noise. We consider the effect of amplitude, pulse-shape, and timing-jitter fluctuations that are characterized by stationary processes. Effects of correlations between different parameters of these fluctuations are studied also. The nonstationary timing-jitter fluctuations of passively mode-locked lasers and their influence on the power spectrum is discussed as well.
TL;DR: The operation of a cavity-dumped self-mode-locked chromium-doped forsterite laser with pulse energies exceeding 30 nJ and pulse durations as short as 54 fs (FWHM) at 1260 nm is reported.
Abstract: We report the operation of a cavity-dumped self-mode-locked chromium-doped forsterite laser with pulse energies exceeding 30 nJ and pulse durations as short as 54 fs (FWHM) at 1260 nm. By frequency doubling in a β-barium borate crystal, pulse energies as high as 3 nJ and pulse durations as short as 49 fs (FWHM) at 630 nm were generated. The high stability and ultrashort pulse widths with a variable repetition rate in both the infrared (1260 nm) and the red (630 nm) make this system an attractive light source for ultrafast spectroscopy.
TL;DR: Fourier spectral analysis of temporal interference resulting from beats between a reference optical frequency and a number of spectral components of a femtosecond optical pulse yields the spectral phase directly without the need for iterative calculations.
Abstract: Fourier spectral analysis of temporal interference resulting from beats between a reference optical frequency and a number of spectral components of a femtosecond optical pulse yields the spectral phase directly without the need for iterative calculations. A periodic multiple-slit mask placed in the Fourier plane of a femtosecond pulse shaper selects an ensemble of frequency components for measurement by cross correlation. An additional, out-of-period slit selects the reference frequency so that none of the desired beat tones overlaps redundant tones. We measure positive and negative cubic phase distortion introduced when the pulse shaper lens is tilted and the phase discontinuity of a 0–π pulse (odd pulse) with a 13-slit mask. Finally, we demonstrate measurement of the spectral phase associated with true time delays with 17 slits.
TL;DR: By spectrally slicing a high power 10 GHz femtosecond source, the authors in this paper have successfully generated 10 GHz pulse trains at 16 wavelengths separated by 1 nm, and the average powers directly at the output of the spectral slicing filter range from 0.5 to 2.2 mW per channel.
Abstract: By spectrally slicing a high power 10 GHz femtosecond source, the authors have successfully generated 10 GHz pulse trains at 16 wavelengths separated by 1 nm. The typical pulse has a duration of 14 ps, a spectral width of 0.2 nm, and a time-bandwidth product of 0.35. The average powers directly at the output of the spectral slicing filter range from 0.5 to 2.2 mW per channel.
TL;DR: The saturation characteristics of pulse amplification in an ytterbium-doped fiber are studied and it is found that the fiber is capable of amplifying the bandwidth of 100-fs pulses at 1 microm.
Abstract: The saturation characteristics of pulse amplification in an ytterbium-doped fiber are studied. The highest pulse energy obtained is 12 μJ at a repetition rate of 1 kHz. Even with gain narrowing, the fiber is capable of amplifying the bandwidth of 100-fs pulses at 1 μm.
TL;DR: In this paper, the spectral, temporal and spatial characteristics of plasma-induced spectral blue shifting in atmospheric-density rare gases were investigated by a two-color pump-probe technique.
Abstract: The spectral, temporal, and spatial characteristics of plasma-induced spectral blue shifting in atmospheric-density rare gases were investigated by a two-color pump–probe technique. When the degree of ionization is less than 1, experiments and theoretical results show that field ionization occurs over a time approximately equal to half the pump-pulse width and that ionization-induced defocusing causes spectral blue shifting to be spatially dependent. The pulse width of a 147-nm pulse generated by four-wave mixing of a femtosecond KrF laser pulse in xenon was determined to be 400 fs by a cross-correlation technique based on plasma defocusing.
TL;DR: In this article, the authors demonstrate the use of a femtosecond pulse-shaping apparatus for electronically programmable phase filtering of amplified spontaneous emission from an erbium-doped fiber amplifier.
Abstract: We demonstrate the use of a femtosecond pulse-shaping apparatus for electronically programmable phase filtering of amplified spontaneous emission from an erbium-doped fiber amplifier. Pulse shaping applied to a broadband incoherent light (noise) input results in reshaped noise, with a specially tailored electric field correlation function. Our experiments clearly reveal that phase filtering can strongly affect the coherence properties of broadband, phase-incoherent light.
TL;DR: This work proposes a method for direct conversion of an ultrashort pulse into a monochromatic beam whose wave front either repeats or is related to the phase structure of the pulse or its spectrum by sum-frequency generation of the spectrally resolved pulses.
Abstract: We propose a method for direct conversion of an ultrashort pulse into a monochromatic beam whose wave front either repeats or is related to the phase structure of the pulse or its spectrum. This can be done by sum-frequency generation of the spectrally resolved pulses. Experimentally, we projected two spectra of the same chirped pulse onto the nonlinear crystal so that the dispersions were opposite. After sum-frequency generation, a converging or diverging monochromatic beam was formed that was the analog of the pulse spectrum. We could determine the chirp value by the measurement of the wave-front radius.