PURPOSE: To avoid the bad influence based on the optical rotatory power of optical modulating elements to form a high-sensitivity (multistage) longitudinal optical modulating device, by combining optical modulating elements and reflective plates and allowing the light to pass elements back and forth once or more.
CONSTITUTION: In a longitudinal optical modulating device formed with optical modulating elements (consisting of the single crystal of Bi12SiO20, Bi12GeO20, etc.) having the optical rotatory power, the light from a light source 1 is allowed to pass through optical modulating element groups 4-1W4-5 (provided with transparent electrodes 5 and a modulation signal source 6) and is reflected by a reflective plate 8 and is allowed to pass through said element groups again backward and is detected by a photodetector 7 (a polarizer 2 and a 1/4 wavelength plate 3 are provided). By this constitution, though the light is transmitted through element groups whose number is twice as large as the number of used element groups, the light after reflection is rotated in the direction opposite to that in the going path, and practically, all modulating elements modulate the light effectively.
TAKIMOTO HIDEYUKI
KOUNO ICHIROU
