Abstract

Koch et al.¹ have solved for the laser light intensity and the excitation density as a function of time and space (in the beam direction) in a semiconductor doped glass that exhibits increasing absorption² optical bistability under pulsed operation. A kink in the excitation density that propagates as a discontinuity in the beam direction and manifests itself as a sawtooth variation in the output intensity is predicted. Gibbs et al.³ reported the first experimental observation of kinks in a sharp cut color filter. Kinks that are an emphatic illustration of the local nature of increasing absorption optical bistability are presented. Furthermore, kinks demonstrate an intrinsic dissimilarity between increasing absorption optical bistability and bistability dependent upon external feedback, where a longitudinal discontinuity cannot occur. If the input is an increasing ramp, then the front part of the sample reaches the condition, carrier density, and temperature, for switching down before the remainder, whose light intensity is reduced by absorption in the front. The discontinuity in the excitation density develops as a consequence of competition between transverse thermal conduction and heating of the sample by increasing absorption in the shielded back part of the sample. The number of discontinuities is limited by the pulse rise time, sample length, and conduction time, which scale as the square of the beam radius.

© 1985 Optical Society of America