| 摘要 |
PURPOSE:To prevent loss of unpolarized light owing to polarized light by making use of the wavelength dependency of a polarized light separating element and phase difference plates having optical anisotropy. CONSTITUTION:Phase difference plates 16, 17 made of a crystal having the optical anisotropy of the thickness adjusted in such a manner as to act as a 1/4-wavelength plate for light of lambda1 wavelength, and as a 1/2-wavelength plate for the lambda2 wavelength differing from lambda1, a polarized light separating element 15, and reflection mirrors 18, 19 are disposed as shown in the figure. Then, the linearly polarized light parallel to the plane of the figure is transmitted through said separating element 15 and the linearly polarized light perpendicular to the plane of the figure is reflected. Both rays return to the separating element by going through the phase difference plates and the reflection mirros. At this time, the lambda1 light is equivalent to the one having passes through the 1/2-wavelength plate and therefore its polarization state is turned 90 deg., and enters an optical fiber 12, whilist the lambda2 light equivalent to the one having passd through the 1-wavelength plate returns to an optical fiber 11. |
