Optical bistability via thermal effects in a glass filter (A)

M. Lambsdorff, C. D�rnfeld, Claus F. Klingshirn

J.A. Hermann

F. Pereira, José R. Salcedo, Michael Scott Belsley

Wherret et al.1 have derived a general condition for the existence of intrinsic optical bistability, stipulating that the absorption length of the sample, αL, must be less than 0.18. Nonetheless several research groups have observed optical bistability in samples with absorption lengths significantly above this limit.2 It has been suggested2 that the observed bistability is the result of an initial self-focusing of the incident beam brought about by thermal refractive index change which then induces a bistable effect in the final portion of the sample. If the focal length of the laser induced thermal lens is comparable with the sample thickness, then the reduction of the laser beam size could then induce bistability at a lower threshold in the final portion of the sample. We have carried a systematic test of this hypothesis, using a modified version of the Z-scan technique, on a commercially available semiconductor-doped glass filter.

Doreen A. Weinberger, Hyatt M. Gibbs, C. F. Li +1 more

F. Pereira, José R. Salcedo, Michael Scott Belsley

We present a simple experiment which demonstrates the main features of intrinsic optical bistability obtained through thermally induced shifts in the band edge of semiconductor particles embedded in a glass matrix. This readily demonstrates how nonlinear optical effects can be used to transmit information, providing an instructive introduction to the main concepts of optical computing. Several possible extensions of the experiment suitable for advanced independent research projects are discussed.

F. Pereira, Michael Scott Belsley, José R. Salcedo

We used a modified form of the Z-scan technique to study the various factors influencing bistability in a semiconductor doped glass filter. A strong self-focusing effect was observed and an estimate of the corresponding n2 coefficient is obtained. A systematic modeling of absorptive bistability in a semiconductor doped glass, including both longitudinal and transverse heat diffusion as well as the effects of self-focusing, is presented and compared with experimental observations.