M. Y. A. Raja

Resonant periodic gain surface-emitting semiconductor lasers

A surface-emitting semiconductor laser structure with a vertical cavity, extremely short gain medium length, and enhanced gain at a specific design wavelength is described. The active region consists of a series of quantum wells spaced at one half the wavelength of a particular optical transition in the quantum wells. This special periodicity allows the antinodes of the standing-wave optical field to coincide with the gain elements, enhancing the frequency selectivity, increasing the gain in the vertical direction by a factor of two compared to a uniform medium or a nonresonant multiple quantum well, and substantially reducing amplified spontaneous emission. Optically pumped lasing was achieved in a GaAs/AlGaAs structure grown by molecular-beam epitaxy, with what is believed to be the shortest gain medium (310 nm) ever reported. >

Surface‐emitting, multiple quantum well GaAs/AlGaAs laser with wavelength‐resonant periodic gain medium

A novel surface‐emitting semiconductor laser with a vertical resonator, extremely short gain length, and enhanced gain at a specific design wavelength has been demonstrated. The gain medium consists of a series of GaAs quantum wells separated by AlGaAs spacers whose thicknesses are chosen to be one‐half the wavelength of a particular transition in the quantum wells. This structure forces the antinodes of the standing‐wave optical field to coincide with the gain elements, enhancing the gain and frequency selectivity in the vertical direction and substantially reducing amplified spontaneous emission. We have achieved optically pumped lasing with a threshold of 6 MW/cm2 at room temperature in a molecular beam epitaxially grown structure of thickness 4.3 μm, of which only 320 nm provided gain.

Vertical cavity surface-emitting semiconductor laser with CW injection laser pumping

Room-temperature CW operation of a GaAs/AlGaAs vertical cavity surface-emitting laser with a resonant periodic gain medium, using a GaAs/AlGaAs diode laser array as a pump source, is discussed. Pumping thresholds as low as 11 mW at 730 nm, output powers as high as 10 mW at 856 nm, and external quantum efficiencies as high as 70% are obtained, with considerably improved temporal and spatial coherence properties compared to the pump laser. This is the first reported operation of such a laser with an efficient, compact pump source, demonstrating its suitability for efficient integration. >

Laser‐induced degradation of GaAs photoluminescence

We report experimental studies of laser‐induced degradation of surface photoluminescence efficiency in n‐GaAs, p‐GaAs, semi‐insulating Cr‐doped, and undoped liquid‐encapsulated Czochralski‐grown GaAs for excitation intensities ranging from ∼0.1 to ∼20 kW/cm2. The data suggest a contribution from optically induced defects in the bulk material. The time dependence of photoluminescence efficiency was fitted to a simple power‐law expression. A previously unreported fast decay of photoluminescence, occurring in 1–2 s immediately following the cleaving of a fresh surface, was observed in p‐ and n‐type samples.

High-sensitivity surface-photoacoustic spectroscopy

The sensitivity of surface-acoustic-wave detection is extended by several orders of magnitude to a surface-specific absorbance of alphal ~ 10(-9) for a power density of 1 GW/cm(2) using a narrow-bandwidth interdigitated surface-acousticwave detector and an optical irradiation pattern to provide a matched acoustic signal. Major advantages include narrow-bandwidth detection and a large irradiated area that permits more optical energy on the sample. A rapid, nondestructive, reproducible liquid-bonding technique, which permits the extension of these measurements to a wide variety of samples, is demonstrated. Results for AlN and ZrO(2) films (alphal ~ 10(-4)) and fused-silica substrates (alphal ~ 10(-6)-10(-7)) are reported.

Optical Cavity Design For Wavelength-Resonant Surface-Emitting Semiconductor Lasers

Recently, we have demonstrated a novel surface-emitting semiconductor laser with a wavelength-resonant periodic gain medium, which has performed significantly better than conventional double-heterostructure and multiple-quantum-well vertical-cavity devices. The gain medium consists of a series of half-wave-spaced quantum wells which provides enhanced longitudinal gain at a selected wavelength in the vertical direction, reducing transverse amplified spontaneous emission, lowering the threshold and raising the quantum efficiency. However, because the antinodes of the standing-wave optical field must coincide with the quantum wells, considerable attention must be devoted to designing the vertical cavity. Here we examine various cavity configurations in which the wavelength-resonant periodic gain medium has been incorporated. Multilayer epitaxial reflectors are particularly attractive for fabricating monolithic vertical-cavity surface-emitting lasers.

Wavelength-resonant, Surface-emitting Semiconductor Laser: A Novel Quantum Optical Structure

Wavelength-Resonant, Surface-Emitting Semiconductor Laser: A Novel Quantum Optical Structure M.Y.A. Raja, S.R.J. Brueck, M. Osinski, C.F. Schaus, J.G. Mclnerney, University of New Mexico, Albuquerque, NM and T.M. Brennan, B.E. Hammons, Sandia National Laboratories, Albuquerque, NM. We designed, fabricated and demonstrated lasing action in a novel vertical surface-emitting laser structure. The MBE-grown structure is a seriesof 10-nm thick GaAs quantum wells separated by 120-nm thick AlGaAs barriers for a spatially periodic gain medium resonant with the lasing wavelength. Lasing has been achieved by optical pumping with a gain length of only 320 nm.