An analysis is made of spot patterns generated in a liquid crystal spatial light modulator with optical feedback from the point of view of controlling generation of spots. The conditions for forming solitary spots were analyzed using a theoretical model which fits the experimental device well. Phenomena observed in experiments such as spontaneous birth, motion, and merging of spots is reproduced in numerical simulation with the model. It is shown how parameters characterizing nonlinearity, diffraction, and diffusion can be designed for stable spots and stable spot motion.

We report the first evidence that the I -X transfer mechanism plays a significant role in carrier transport in type-I semiconductor superlattices under an electric field. An anomalously delayed photocurrent was observed in a GaAs/AJAs type-I superlattice under ultrashort optical pulse excitation.This phenomenon can be explained by a switch of the electron transport path from I -I to I -X-I -X, caused by an electric-field induced change of the subband alignment of the second 1 state (I'2) in the well and the Xl state in the adjacent barrier.

The lasing of the whispering gallery modes of the microdisc are investigated theoretically by solving the Maxwell equation with the nonlinear effect of the light field on the polarization due to the lasing medium as well as the circular boundary condition. The light of the lasing modes are trapped inside the microdisc even in the case that the angle of incidence of the light to the disc boundary is smaller than the critical angle.

An optical circuit for beam pointing using self-organized roll patterns is proposed and demonstrated. The circuit contains two mutually coupled spatial light modulators (SLMs). It is shown that abrupt beam switching can be realized by changing a bias voltage applied to the liquid crystal layer of one of the SLM. The pattern forming and beam switching mechanism is explained using a theoretical model which includes the effects of diffraction, feedback displacement, and nonlinearity of the SLM.

Development of future parallel communication systems demands technologies for generation, storage and manipulation of complicated optical beam patterns. Use of self-organizing spatial phenomena in self-modulating optical devices may be an effective approach. Experimental studies of bistable spatial memories using spatial light modulators [1,2] have shown spatial coupling is significant for the stability and resolution of light dots, and also can give rise to complex spatial patterns, including localized structures.