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Showing papers by "Gerard Mourou published in 1981"


Journal ArticleDOI
TL;DR: In this article, a subpicosecond laser has been used to trigger a GaAs photoconductive switch driving a dipole antenna, and the microwave transient produced was measured with a correlation technique to have a FWHM of less than 3 psec.
Abstract: A subpicosecond laser has been used to trigger a GaAs photoconductive switch driving a dipole antenna. The microwave transient produced was measured with a correlation technique to have a FWHM of less than 3 psec. This technique was also used in a contactless measurement of the 250‐psec lifetime of a GaAs sample.

167 citations


Journal ArticleDOI
TL;DR: In this paper, a laser-activated photoconductive switch was used to generate X-band microwave pulses and these pulses were used to observe the microwave reflection from optically excited germanium.
Abstract: Picosecond duration X‐band microwave pulses have been generated using a laser‐activated photoconductive switch. These pulses have been used to observe the microwave reflection from optically excited germanium. The reflection measurements indicate that the microwave pulse has a full width at half‐maximum of 50 ps and is synchronized with picosecond precision to the laser pulse. A high‐resolution radar experiment is also reported.

90 citations


Journal ArticleDOI
TL;DR: In this article, a 24-beam phosphate-glass laser system has been built and tested, which has demonstrated focusable power in excess of 12 terawatts (TW) in 50 ps (FWHM) and over 1.75 kJ in 300 ps in 300 FWHM.
Abstract: A 24-beam phosphate-glass laser system has been built and tested. Major design features include Nd:phosphate glass, rod amplifiers up to 90 mm diameter, propagation of circularly polarized light, extensive image relaying and spatial filtering, utilization of large-aperture Pockels cells (PC's) hard-aperture (HA) input and polarizing beamsplitters for beam balance. The system has demonstrated focusable power in excess of 12 terawatts (TW) in 50 ps (FWHM) and over 1.75 kJ in 300 ps (FWHM). The pulse is near-diffraction limited with a peak-to-background energy contrast of 108. Shot rates have exceeded 2/h. A detailed description of the system design and performance is presented.

53 citations


Journal ArticleDOI
TL;DR: Using a DC-biased room-temperature photoconductive switching element, a streak camera is operated at sweep rates up to 7 ps/mm with complete absence of short and long-term drift characteristic of all other sweep drivers as discussed by the authors.

42 citations


Journal ArticleDOI
TL;DR: In this article, stable, tunable, sub-picosecond pulses were obtained by synchronously pumping a Rhodamine 6G dye laser with a frequency-doubled CW modelocked neodymium YAG laser.

41 citations


Journal ArticleDOI
TL;DR: In this paper, the temporal shape of laser pulses generated from an active passive mode-locked Nd3+: YAG oscillator was measured over ten orders of magnitude by measuring the third order correlation function of the laser pulse.

36 citations


Patent
27 Aug 1981
TL;DR: In this article, the photoelectrons are absorbed in the semiconductor material to create throughout the gap a degenerate layer and the gap geometry and the image formed by the optical signal on a photocathode, which provides the photo-electronic signal, are such that space charge effects do not distort the photoelectric signal and a temporal replica of the optical signals illuminates the entire gap.
Abstract: Picosecond switching of electric current in response to optical signals is obtained by conversion of the optical signal, such as an optical pulse, into a photoelectron burst (a photoelectronic signal) which is a faithful temporal replica of the optical signal. Electron optics increase the energy of the electrons of the photoelectronic signal which is imaged so as to illuminate essentially the entire gap formed between electrodes on a body of semiconductor material. The photoelectrons are absorbed in the semiconductor material to create throughout the gap a degenerate layer. The gap geometry and the image formed by the optical signal on a photocathode, which provides the photoelectronic signal, are such that space charge effects do not distort the photoelectronic signal and a temporal replica of the optical signal illuminates the entire gap. The gap geometry affords broad bandwidth operation. Due to the gain in the system, the high photoelectron energy obtainable after electron acceleration permits the use of large band gap semiconductor materials which have high dielectric strength and are not prone to thermal breakdown effects. By deflecting the photoelectrons across a plurality of side-by-side gaps on the semiconductor, extremely high speed demultiplexing of extremely high frequency optical signals (in picosecond samples) can be obtained.

14 citations


Patent
23 Mar 1981
TL;DR: In this paper, a simple and highly accurate sweep drive circuit for streak cameras generates a ramp voltage for the deflection plates of an image converter tube of a streak camera, which is used in a manner which eliminates the need for a pulsed multi-kilovolt bias voltage and the use of cryogenics.
Abstract: An inexpensive, simple and highly accurate sweep drive circuit for streak cameras generates a ramp voltage for the deflection plates of an image converter tube of a streak camera. A solid state switch is used in a manner which eliminates the need for a pulsed multi-kilovolt bias voltage and the use of cryogenics. High voltage direct current in the multi-kilovolt range is applied to a charged circuit which may include a high voltage capacitor or use the capacitance presented by the deflection plates of the tube. The switch is laser activated and becomes photo-conducting. The charge in the capacitor passes through a charging resistor which controls the sweep rate to the deflection plates. After the activating laser pulse, the switch returns rapidly to a nonconducting state, during the recombination time of the switch material. The photo-electron beam is swept linearly over a substantial portion of the recombination time from off the image forming phosphor screen to off screen on the other side thereof. A resistor connected to the deflection plates provides a time constant long compared to the transient event lifetime, which may be the fluorescence decay time of the system under study, and the beam remains off the phosphor screen for a very large time compared to the fluorescence decay time. In a second configuration when the deflection plates are used as the charged source, the laser-activated switch is connected between a deflection plate and a point of reference potential (ground) through the charging resistor.

14 citations


Journal ArticleDOI
TL;DR: In this article, a Q-switched active-passive Nd : YAG laser and a c.w. argon ion laser were simultaneously mode-locked using a common R.F. oscillator.

11 citations


Patent
21 Dec 1981
TL;DR: In this article, a synchronously pumped dye laser using a mixture of laser dye and a fast recovery saturable absorber was used to obtain subpicosecond pulses less than 70 femtoseconds in duration.
Abstract: Subpicosecond pulses less than 70 femtoseconds in duration are obtained with a synchronously pumped dye laser using a mixture of laser dye and a fast recovery saturable absorber which passes in a jet between folding mirrors in a laser cavity. The ratio of absorber to dye in the mixture is selected to compensate for dispersion effects in the laser medium which tend to limit the spectrum of the laser pulses and increase their duration.

7 citations


Journal ArticleDOI
TL;DR: In this article, an autocorrelator was used to measure the pulse width of an Ar+ laser with 3-5mW output power and 50 mW of pump power.
Abstract: onto an -5-pm diam spot on the crystal using a 1OX microscope objective, which also served to collimate the CdS fluorescence. A polarizing beam splitter separated the vertically polarized pump light from the horizontally polarized CdS emission. Thresholds as low as 25 mW have been observed using an unmode-locked pump beam. An 8% transmitting output coupler yielded 8.8 mW out for 90-MW input power. With a prism inserted into the cavity, the laser could be tuned from 495 to 501 nm, while maintaining the 0.1-nm linewidth. In addition, when the temperature of the sample was raised from 95 to 140 K, the laser wavelength could be increased to 504 nm. Lasing could be accomplished using any of the 488-, 476-, 473-, or 458-nm lines of the Ar+ laser as a pump. For synchronous pumping the Ar+ laser was actively mode-locked to produce 100-psec pulses on the 476-nm line, and the cavity was lengthened to 1.8 m. The pulse width was measured in an autocorrelator using a lithium formate crystal. Typical spots gave stable 10-12-psec (assuming a singlesided exponential shape) pulses with 3-5-mW output power and 50 mW of pump power. Up to 26 mW of output power could be maintained for a short while. The cavity length can be changed by 500 p m without adversely affecting the pulse shape. This is in sharp contrast to synchronously pumped dye lasers, where changes of only microns can drastically alter the pulse shape. This indicates that passive pulse-shaping may be taking place. The output spectrum is much broader than that encountered in cw operation, and often lasing in more than one mode of the crystal Fabry-Perot occurs. Antireflection coating of the cvstal face to eliminate these modes would increase the cavity bandwidth and possibly result in shorter pulses. We hope this technique can be extended to other semiconductors such as AlGaAs and thus make available a picosecond pulse source easily tunable throughout the visible and near IR. (13 min)