| 摘要 |
PROBLEM TO BE SOLVED: To make an optical isolator of high performance, cabbage of being miniaturized and reduced in cost, by providing the double refraction crystal of a polarized light separating element to incline in a direction in which the angle formed by its optical axis and an incident light beam smaller to suppress the degradation of a signal due to multiple reflected lights and to exert a larger isolation characteristic. SOLUTION: In the change of a separation distance at the time when the optical isolator is inclined for the purpose of eliminating multiple reflected lights, the separation distance is increased or decreased depending on the positive angle or the negative angle of an incident angle, in short, the separation distance is changed by the inclination angle of the optical isolator. When the isolator has the same performance both in the positive inclination angle and the negative angle in order to suppress the multiple reflected lights, it is desirable to incline the element to a direction in which the enhancing of the isolation characteristic can be expected together with the suppressing of the reflected lights. The direction is a direction in which the angle formed by the optical axisθof the double refraction crystal and the incident light beamθ' becomes small. Moreover, it is desirable that this inclination angle is large as much as possible for the pupose of eliminating the multiple reflected lights, but when the effective diameter of the polarization-dependent loss element of a forward direction beam is considered, the angle of the range of 3 deg.∼5 deg. is suitable.
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