Abstract

Various schemes of periodic quantum wells with integrated epitaxial high reflectors have recently created great excitement and hope for realizing very low threshold surface-emitting laser arrays¹ and efficient high-power optically pumped surface-emitting laser structures with resonant periodic gain (RPG).² Here we report investigations of photoluminescence (PL) properties of In_0.2Ga_0.8As/Al_0.2Ga_0.8As periodic quantum wells on GaAs substrate, i.e., RPG without integrated mirrors. The angular distribution of the PL shows strong directionality of the spontaneous emission along with normal to the surface. The investigated samples include 20-, 40-, 60-period RPG and single quantum well on GaAs substrates with and without back-surface polished and/or antireflection coating. The enhancement in the directionality of PL with the number of quantum well periods is pronounced compared with the single quantum well case. There is also a marked reduction in the amplified spontaneous emission in the transverse direction. A proper phase relationship between a previously emitted photon and that being emitted may enhance or inhibit the emission process in a given direction.

© 1991 Optical Society of America