The absorption saturation relaxation time in light- and heavy-ion-irradiated GaAs saturable absorbers has been measured as a function of the temperature in the range from 7 to 300 K. For both types of samples, the relaxation time is shorter than 4 ps at 7 K. A regular increase of this time with temperature is observed for light-ion-irradiated samples, a value of 9.5 ps being reached at room temperature. In contrast, an almost temperature-independent relaxation time is found for heavy-ion-irradiated samples. The results are interpreted on the basis of a simplified relaxation model accounting for capture and emission from defect levels. We suggest that light-ion irradiation creates shallow centers whereas heavy-ion irradiation creates deep centers.

We develop a method for finding the number and shapes of the independently squeezed or amplified modes of a spatially-broadband, travelling-wave, frequency- and polarization-degenerate optical parametric amplifier in the general case of an elliptical Gaussian pump. The obtained results show that for tightly focused pump only one mode is squeezed, and this mode has a Gaussian TEM(00) shape. For larger pump spot sizes that support multiple modes, the shapes of the most-amplified modes are close to Hermite- or Laguerre-Gaussian profiles. These results can be used to generate matched local oscillators for detecting high amounts of squeezing and to design parametric image amplifiers that introduce minimal distortion.

Effect of Be doping on the absorption of InGaAs/AlGaAs strained quantum-well infrared photodetectors grown by molecular-beam epitaxy Appl. Phys. Lett. 74, 1570 (1999); 10.1063/1.123619Carrier lifetime and exciton saturation in a strain-balanced InGaAs/InAsP multiple quantum well

An external linear optical system (with no feedback to the laser) converts the laser's multimode emission into a multilongitudinal but spatially single-mode (diffraction-limited) spot. Recent progress in laser diode mode analysis demonstrating the high stability of the mode pattern of broad-area laser diodes and the development of the low-loss highspectral-resolution phase modulator are the key enablers of such a technique. These advancements led to the demonstration of 60% conversion efficiency of multimode 980 nm diode-laser emissions into a single-mode fiber. INTRODUCTIONBroad-area (BA) laser diodes are the most efficient coherent light sources and are widely used today. The extraordinary efficiency, modulation easiness, and compactness are the three principal drives stimulating the development of light sources based on laser diodes. Despite the fact that kilowatts of multimode power can be easily extracted from laser diode arrays, the reliable single-mode single-element power from the laser diode is always limited by a value approximately equal to 1W due, essentially, to the planar nature of p-n junction injection mechanism. The potential substitution of YAG and fiber lasers [1,2] by a compact direct single-mode laser diode source would bring significant advancements in a number of applications requiring laser beam modulation and unusual wavelengths such as high-range high-resolution high-speed LIDAR/LADAR's [3] , broad-band satellite communication systems, laser HDTV projection systems, cutting/dicing/marking material processing, and many more.The problem is not new. During several decades, numerous experiments were conducted to force a large-emission-area laser diode to laze in a single-spatial-mode regime. Multiple solutions have been proposed. [4][5][6][7][8] Mechanical cavity instabilities, non-linear effects of all kinds, inherently low mode-gain profile overlap, and fabrication difficulties were the major reasons why until today all these experimental demonstrations were not converted into commercial products.This article is attempting to review an unusual approach for the extraction of spatially coherent light from a BA semiconductor laser. The laser is allowed to run in his natural high-efficiency, spatially-multi-mode regime. An external linear optical system (with no feedback to the laser) converts the laser's multimode emission into a multi-longitudinal, but spatially-single-mode (diffraction-limited) spot. The key enablers of such a technique are the recent progress in laser diode mode analysis clearly demonstrating the rock-solid stability of the mode pattern of BA laser diodes and the development of the low-loss spectrally-resolved phase modulator. Accordingly, the article summarizes the basis of mode structure BA laser diode cavities, shows the spatially-and angularly-resolved spectra for BA lasers of several types at high power, briefly summarizes the mode harnessing experiments, and, finally, proposes the potential future development scope for the lateral-mode harnessing approach. SPATIO-SPE...