| 摘要 |
PURPOSE:To realize an optical element module with less polarization dependency loss fluctuation in which the polarization dependency loss fluctuation for the optical element module as a whole is equal to the value obtained by reducing the polarization dependency transmissivity fluctuation from the polarization dependency diffraction efficiency fluctuation. CONSTITUTION:This optical modulator is provided with a function modulating a beam propagating from an incident beam 27 to a primary diffracted light beam 28 by a modulation element 25. Then, a glass plate 11 is arranged at a prescribed angle in the advancing direction of the incident beam 27. Since anisotropy is provided in an acoustooptical medium 21 in a refractive index (n), the diffraction efficiency etap when the incident beam 27 is a horizontal polarization becomes lower than the diffraction efficiency etas when the incident beam 27 is a vertical polarization, and the polarization dependency diffraction efficiency fluctuation DELTAeta occurs. On the other hand, the glass plate 11 is provided with the polarization dependency transmissivity fluctuation DELTAT with a trend opposite to the polarization dependency diffraction efficiency fluctuation DELTAetaof the acoustooptical medium 21. |
