Abstract

The band-transport model is used to study the effects of a pulsed Gaussian laser beam on photorefractive materials. Attention is paid to the relaxation of the polarization of the materials. When the relaxation time of the polarization is much shorter than the pulse length, the results differ little from those obtained when the relaxation is omitted. The induced electrical field in the illuminated area reaches its steady-state value much faster than in the dark area because there are many more photocarriers in the illuminated area. Although electron density and ionized-donor density decrease rapidly because of recombination when the light is turned off, the total charge density, which determines the induced field, keeps growing as a result of a nonzero electrical current. After the initial growth, the field remains unchanged for a long time, i.e., there is long-term storage of the induced field. When the relaxation time is longer than the pulse length, then the longer the relaxation time, the faster the induced field grows when the light is on, but the slower it reaches steady state when the light is off. This occurs because the polarization slowly follows the change in the field.

© 1990 Optical Society of America