| 摘要 |
PURPOSE:To provide the selectivity of a TE wave and a TM wave by transmitting linearly only the TE wave from an active layer to a clad layer at a bent part in a lambda/4 DFB laser, propagating the TM wave toward a bent active layer, and absorbing the TM wave without providing an electrode on the bent active layer. CONSTITUTION:The reflectivity R of a TE wave(Transverse-Electric Wave) is gradually decreased as an incident angle theta is increased, and becomes '0' at a Brewster angle thetaB, is abruptly increased therethrough, and fully reflected at a critical angle thetaC. On the other hand, the reflectivity R of a TM wave(Transverse-Magnetic Wave) is simply gradually increased as the incident angle theta, is abruptly increased through the angle thetaB, and fully reflected at the angle thetaC. Thus, the reflectivity of the TE wave becomes '0' when it is incident at the Brewster angle in the boundary between an active layer 5A and a clad layer 6 to be transmitted. On the other hand, the TM wave is bent toward the bent layer 5A, and since no electrode is provided in this region, no light emission occurs, and the TM wave is absorbed into the active layer. Thus, the TM wave is absorbed in the lambda/4 DFB(distributed feedback type) laser, and can be oscillated only with the TE wave. |
