On kink dynamics in media with increasing absorption optical bistability

Abstract

The motion of the boundary between dark and light domains in a crystal with increasing absorption-optical bistability (the so-called kink) is considered. In the low diffusion limit the kink moves undergoing effective viscous friction which essentially affects the output intensity. The crystal boundary influence on the kink is substantial if the diffusion is sufficiently high. No jumping kink motion resulting in a sawtooth structure of the output intensity can take place in a pure crystal unless a compound material consisting of isolated semiconductor crystals is used,

Kinks in Resonatorless Optical Bistability. Stability Limits and Formation Dynamics

“…If the condition (16) is met, the kink will move continuously according to the results of [9]. In the opposite limit t, 4 z, the kink will not be able to keep up with the changing intensity and will move by leaps [6] (that is what was called "the diffusionless limit" in [2], where, however, the wrong value z/af had been used instead of zc).…”

“…The condition (19) implies that, e.g., in optically thin crystals (d < 1, ) a* < 1 (Fig. 2) and the ratio /,/la should indeed be very small for the stable kinks to exist [l, 71, while in thick crystals a* 2 1 and stable kinks are likely to be present even at large lD/l,, although it is not very clear what the term "kink" means in this latter case [9]. The exactly solvable step function model enabled us to investigate the behaviour of kinks in a bounded crystal and to pin-point mechanisms which determine their stability.…”

“…Normally they are assumed to be present only in relatively thick samples, but there are no quantitative estimates of how thick a sample should be. There is also some controversy concerning the dynamics of kink motion: in some cases they apparently move by leaps [6], while in other cases they are expected to move continuously with changing intensity [9], and again it is unclear where is the borderline between these two regimes.…”