The difference in the refractive index at around λ=0.37 µm between GaN and Al0.1Ga0.9N is found to be about 0.19. With use of AlGaN/GaN double heterostructures, the threshold power for surface-stimulated emission by optical pumping at room temperature has been markedly decreased to about one-twentieth that of a bulk GaN layer. The mechanism of the stimulated emission in this system is discussed.

We have proposed a novel short-cavity laser with deep-grating distributed Bragg reflectors (DBRs). We monolithically fabricated a 0.98 µm InGaAs/AlGaAs device and 1.55 µm GaInAsP/InP device using electron beam lithography and a reactive ion beam etching technique. The lasing operation of both devices was achieved at room temperature. From a comparison of the threshold current from the experimental result with that from the theoretical result, the reflectivity of formed DBRs was estimated to be less than 30%. The theory also predicts that the ideal DBR exhibits a high reflectivity over 97% even with 3 periods of grating. It achieves lasing operation with a threshold current less than 100 µA using a cavity shorter than 10 µm. This high performance is realized by reducing the surface roughness and damage to etched sidewalls and improving the reflectivity of the DBR.

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