| 摘要 |
PURPOSE:To decrease coupling losses and to facilitate the connection to an optical fiber and to attain a cost reduction without limiting a laser beam source by multiplexing the signal light past one of a pair of optical waveguides and the local light past the other on a crystal substrate. CONSTITUTION:Ti films patterned by a photolithography method and an electron beam vapor deposition method are thermally diffused into the crystal substrate 1 of LiNbO3 to form a pair of the optical waveguides 2, 3. An SiO2 film is formed by using an electron beam vapor deposition method on the substrate 1 and further plural Ti-Au electrodes 9 are selectively formed thereon, by which mode converters 4, 6 and phase shifters 5 are formed, which constitute a polarization control element 7. The local light inputted to the optical waveguide 2 is converted to coincide with the polarization state of signal light by the polarization control element 7 and is then made incident on the coupler 10, by which the local light is multiplexed with the signal light inputted to the optical waveguide 3. After the local light and the signal light are multiplexed, the light is converted to a detection signal which is an electric signal in two photodiodes. The control of the polarization state is executed by controlling the driving voltage of the polarization control element 7 in such a manner that the intensity of the detection signal is maximized. |
