Showing papers by "Gerard Mourou published in 1985"

Kilohertz synchronous amplification of 85-femtosecond optical pulses

Abstract: High-repetition-rate laser pulse amplifiers are desirable for investigations of weak signals because of the ability to use ultrasensitive lock-in detection. We have developed a new oscillator and amplifier capable of providing 10 MW of power at repetition rates in excess of 1 kHz. By focusing this pulse we have obtained the white-light continuum with as little as 250 nJ of energy.

Electro-electron optical oscilloscope system for time-resolving picosecond electrical waveforms

Abstract: A system for time-resolving ultra-short electrical waveforms of up to a few hundred gigahertz bandwidth is presented. The system utilizes a fast electro-optic modulator capable of subpicosecond responsivity. A CW (continuous wave) laser is used to probe the change in birefringence resulting in the modulator due to an induced electric field. the rapid change in the transmitted optical signal due to an equally rapid changing electric field (picosecond pulse) is then detected and temporally dispersed using a picosecond resolution streak camera. The modulator operates in a region close to minimum transmission where the average optical power is below the damage threshold for the photocathode of the streak camera and where small electrical signals can significantly modulate the transmitted beam. The system can be used in either sampling mode where the modulation and subsequent detection are repeated and the data accumulated at repetition rates as high as 100 MHz or in single shot mode.

Generation of 85-fsec pulses by synchronous pumping of a colliding-pulse mode-locked dye laser

Abstract: By synchronously pumping a linear-cavity dye laser that has as one end mirror an antiresonant ring containing a thin saturable absorber jet, we have developed a colliding-pulse mode-locked laser, which is capable of being synchronously amplified. Pulse widths of 85 fsec have been obtained. The dye laser is pumped by the frequency-doubled output of a cw mode-locked Nd:YAG laser. This makes synchronous amplification with short pulses possible and provides the additional advantages of increased reliability, ruggedness, and amplitude stability.

Two-dimensional E-field mapping with subpicosecond temporal resolution

Abstract: A new contactless reflection-mode electro-optic sampling technique is described which is capable of characterising the electrical response of microstructures in two dimensions with micrometre spatial resolution, a temporal response of a fraction of a picosecond and millivolt sensitivity. A GaAs-based sampling technique which would have minimum interference with the test circuit is also proposed.

VIA-2 Characterization of TEGFET's and MESFET's using the electrooptic sampling technique

Abstract: Recent advances in GaAs technology have resulted in several new classes of devices, all of which have very high speed response [1,2]. These devices have been shown, indirectly, to have response times of tens of picoseconds [1]. Indirect measurements are necessary because available sampling oscilloscopes have a limiting response of 25 picoseconds and jitter of a few picoseconds. Hence, most ultrafast devices are characterized in a ring oscillator configuration of several devices and individual device response is averaged. In the frequency domain most RF measurements are connector limited to the range of 18 GHz.

An application of picosecond electro-optic sampling to superconducting electronics

Abstract: A picosecond electro-optic sampling technique has been used to measure the switching threshold of a single tunnel junction in a coplanar transmission line geometry. The optical system used, a colliding-pulse mode-locked laser, generated two 120 fs FWHM at 100 MHz. One pulse was used, via a photoconductive switch, to generate an electrical signal of adjustable height and width. The second pulse was used to detect the electrical transient by probing the change in the birefringence of a lithium tantalate crystal induced by the electrical signal. This optical sampling scheme had intrinsic temporal and voltage resolutions of < 500 fs and < 1 mV. In actual experiments, the connection-limited time resolution was 55 ps or 16 ps, depending on whether the detector was placed in room or cryogenic environment. The measured response of the tunnel junction was found to be consistent with the RSJ model.

Transmission Line Designs With a Measured Step Response of 3 ps Per Centimeter

Abstract: In order to effectively exploit the extreme speed and sensitivity potential of both the electro-optic and superconducting technologies, proper generation, coupling, and propagation of signals with bandwidths in excess of 100 Gigahertz is required. In this report we present results of an experimental investigation, supported by theoretical predictions, on a transmission structure which satisfies the ultra wide bandwidth requirements. The experiments, which incorporated a new variation of an electro optical sampling technique [1], investigated the generation of picosecond electrical pulses, an impedance matching tapered coupling configuration, and the propagation of the pulses down the transmission line. The technique allows the measurement of the waveforms at any point along the transmission line while minimizing dispersional effects associated with the sampling. This resulted in an accurate determination of pulse degradation, i.e., step response, per unit length of transmission line. The investigation supports the conclusion that transmission lines and connectors capable of supporting bandwidths in excess of 100 Gigahertz, while allowing relatively dispersionless propagation over distances exceeding a centimeter, are realizable.

Generation Of White Light At 1 Khz

Abstract: We have developed a new dye laser and c.w.-pumped regenerative amplifier system capable of generating white light continuum at a repetition rate higher than 1 KHz.

Transient relaxation of the normal state resistance of tin microstrips in the presence of current bias

Abstract: The transient relaxation of the normal state resistance in tin microstrips has been measured. The microstrips were current-biased below their dc critical current and excited into the normal state with electro optically produced current pulses, with durations as short as 600 psec, by temporarily exceeding the critical current. The effective relaxation time was measured by directly observing the voltage across the microstrip during the normal-superconducting transient. A region was observed in which the relaxation time decreased with increasing current pulse height. The relaxation time was found to be independent of temperature over the range 0.95⩾T/T c ⩾0.77.

Generation of microjoule 65-fsec pulses at high-repetition rate

Abstract: Many significant advances have been made recently in the generation and amplifiction of ultrashort optical pulses. Control of the oscillator dispersion and phase modulation has proven useful in improving the pulse width and pulse stability of ultrashort pulse dye lasers.1 The additional bandwidth provided by self-phase modulation (SPM) in optical fibers has enabled the generation of ultrashort pulses by pulse compression.2 Finally, new amplifier systems have been developed which allow the amplification of femtosecond pulses to the microjoule level at kilohertz repetition rates.3,4 In this paper we report the generation of 65-fsec microjoule pulses at a high repetition rate using an actively mode-locked Nd:YAF-based system.