| 摘要 |
PURPOSE: To make possible the simultaneous excitation of polarized components consisting of a TE mode and TM mode in different directions by coupling both polarized components as forward waves and backward waves. CONSTITUTION: This optical coupler consists of an optically transparent substrate 1, an optical waveguide 2 formed by laminating thin films and a grating layer 3. The propagation constant of the TE mode propagating in this optical waveguide 2 is defined as KTE, likewise, the propagation constant of the TM mode as KTM and the propagation constant of the incident light on the optical coupler in the air as K0 . The equations K0 -sin(θ)+K=KTE, K0 .sin(θ)+K=KTM are satisfied if the incident angle θ on the optical coupler and the grating constant K of the grating 3 are defined sp as to satisfy K0 .sin(θ)=(KTE-KTM)/2, K=(KTE+KTM)/2. As a result, the TE component of the incident light is coupled to the guided wave progressing in the +X direction, i.e., the forward wave and the TM component is coupled to the guided light progressing in the -X direction, i.e., the backward wave. |
