REDUCTION OF POLARIZATION DEPENDENCY IN PLANE OPTICAL WAVEGUIDE

PROBLEM TO BE SOLVED: To provide a method for reducing polarization dependency in a plane optical waveguide by using a material of which the refractive index matches with the thermal expansion coefficient (CTE) between a waveguide core and a cladding layer. SOLUTION: In a coupling type mode devices such as a directional coupler and a mode conversion horn, their operations are dependent on common propagation of light in a fundamental mode and a higher order mode, and since the light is not so strongly confined in the waveguide core in those modes, polarization selectivity relates to birefringence in a cladding. The polarization sensitivity can be reduced by reducing mismatching of CTE between the core and cladding, or eliminating birefringence from the core/cladding interface, or both. To realize this, silicon dioxide or a similar material of which the refractive index (I) matches with CTE is made to adhere between the core and cladding of a characteristic part of a waveguide where salient transmission arises. COPYRIGHT: (C)2005,JPO&NCIPI