| 摘要 |
PURPOSE:To enable efficient mode sepn. by forming two waveguides of different materials with a tapered coupling part changed in thickness to a tapered shape as a boundary and setting the propagation constants and incident angles of these waveguides so as to satisfy prescribed conditions. CONSTITUTION:The two two-dimensional waveguides A, B bisected by the tapered coupling part C the thickness of which changes to a tapered shape in the thickness direction (z-axis direction) are formed of the different materials. The respective propagation constants betaiA, betaiB, betajA, betajB in the waveguides A, B are so set as to satisfy the conditions betaiA>betaiB, betajA<betajB at the time of propagation in the same direction of at least two modes i, j (where i, j are integers) and the incident angle alphaA is so set as to satisfy the conditions alphaA>sin<-1>(betaiB/betaiA). While the light wave of the mode i is, therefore, totally reflected in the tapered coupling part C, the mode j is refracted in the waveguide B. The plural modes propagating in the plane type light guide are thereby efficiently separated. |
