PURPOSE: To enable formation of a monolithic optical integrated circuit by using bismuth silicon oxide or bismuth germanium oxide having electrooptic effect and photoconductive effect to prepare an optical bistable device.
CONSTITUTION: A directional coupler is obtained by forming on a substrate 9 made of bismuth silicon oxide or bismuth germanium oxide a light guide 10 consisting of a light guide layer rendered higher in refractive index the substrate 9 by addition of Ga, Ca, or the like and freed from photoconductive effect 9. When incident light 5 enters the guide 10, light proportional to the output light 6 is guided through a light guide 13 to a photodetctor 17 to drop resistance between electrodes 16, 17 and voltage is impressed between 11, 12 to increase light output 6 from the optical directional coupler, and the light output is abruptly turned on. When light output is decreased, the light output is abruptly turned off. As a result, the action of an optical bistable device is carried out.
KUHARA MIKI
TATSUMI MASAMI
