Abstract

We study the consequences of the intrinsic optical bistability (IOB) due to the local-field effects [1] for the dynamics of two-beam (forward or backward) coupling in strongly absorbing media (dense atomic/molecular gases, semiconductors, polymers, etc.). Within a two-level model we demonstrate creation of the polarization grating that is phase- shifted relative to the incident field. The phase shift is due to the nonlinearity arising from the local-field effects. Precisely the same feature of the phase-shifted polarization response is characteristic for the photorefractive media. We interpret, therefore, this effect as the local-field-induced photorefractivity. It is noteworthy that it can occur in any two-level medium and, most interestingly, it is a very fast phenomenon with response time not limited by charge rearrangement in standard photorefractive materials. The appropriate phase shift between incident field and polarization grating results in unidirectional energy/momentum exchange between the coupled beams and possible amplification of one of them.

© 1996 IEEE