Optical Orientation in Semiconductors

Abstract

I am going to be talking about optical orientation in semi-conductors which is an extension of magneto-optics into a field that more properly might be called opto-magnetics. In this field, in contrast to magneto-optics, one would apply an optical field to a material, and observe changes in the magnetic properties. There are several areas where one can expect significant results: (1) optical orientation - the presence of the optical field results in selective orientation of orbital angular moments and spins which constitutes a magnetization; (2) optical modification of the exchange interaction - in many magnetic semiconductors, the exchange interaction is thought to be indirect, i. e., occurs via the free carriers. An optical field that significantly changes the carrier concentration should modify the exchange interaction, and (3) optically induced change in the angular momentum state of the magnetic ions - generally it is assumed in magnetic theory that angular momentum is quenched in a solid, but experimentally we know that it isn’t quite true for transition-metal ions and definitely not true for rare-earth ions.