| 摘要 |
PURPOSE:To obtain an optically bistable function without using any additional element by causing saturation in the absorption of excitons by the self- convergence effect of a light beam in a semiconductor quantum well when the intensity of the light beam is increased. CONSTITUTION:When incident light is low in intensity, the saturation in the absorption of excitons is small enough to ignore variation in refractive index and the light beam 31 is propagated in a multiple semiconductor quantum well layer 22 through an optical path 33 when the incident light intensity is small nearly without deforming. As the intensity of the light beam 31 is increased, on the other hand, the saturation in the absorption of excitons increases, specially, at the center part of a beam with large intensity and the refractive index also increases, so convex lens effect is initiated. Then the light beam 31 to which intensity is larger than certain light intensity is further converged in the multiple semiconductor quantum well lever 22 like a case wherein the incident light has high intensity, and propagated in a certain part as if it were in a grated refractive index type wave guide substantially like an optical path 34 when the incident light intensity is large. Consequently, the optically bistable function is obtained with the simple element constitution.
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