Abstract

Photorefractive two-beam coupling in semi-insulating GaAs (nominally undoped) is investigated as a function of temperature ranging from 77 to ~330 K. The experiment consists of two beams (pump and probe) from a cw Nd:YAG laser at 1.06 μm intersecting in a GaAs crystal and monitoring gain in the probe and loss in the pump. The intensity of each beam was ~1 W/cm². Our results show that the coupling efficiency increases with increase in temperature and decreases with decrease in temperature. In fact, near liquid nitrogen temperature, the direction of energy coupling switches; to our knowledge, this phenomenon has not been experimentally observed. This implies that there is electron–hole competition¹ in our sample. At ~330 K, the coupling efficiency increases to about twice the room-temperature efficiency; the magnitude of the change cannot be explained adequately with a single-level model. Our results extend the recent report² where dark conduction plays a major role in a single-level single-carrier model. We also study the temperature effects on optical absorption, dark conductivity, and grating formation and erasure times. Optical absorption decreases at both lower and higher temperatures.

© 1987 Optical Society of America