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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Instabilities in self-pulsing semiconductor diode lasers in a long external ring cavity are reported. The frequency of the self-pulsations increases in discrete steps with the injection current and the light-current characteristic displays kinks at these steps. The observed frequencies are multiples of the external cavity resonance and the laser output is unstable when biased at currents corresponding to these kinks. Similar observations have been made in various cavities and other laser diodes. [ABSTRACT FROM AUTHOR]

Responds to comments made by Daniel Guidotti and Harold J. Hovel on the article 'Laser-induced degradation of GaAs photoluminescence,' published in the periodical 'Applied Physics Letters.' Experimental observations on high- and low-resistivity GaAs; Surface recombination-enhanced defect reaction model.