MODE SHAPE CONVERTER, ITS PRODUCTION AND INTEGRATED OPTICAL ELEMENT USING THIS MODE SHAPE CONVERTER

摘要

PROBLEM TO BE SOLVED: To obtain a mode shape converter provided with double waveguides having an expanded tapered ring structure by using a core consisting of a single medium and allowing a lower rib optical waveguide to exist only in the portions of a coupling region and a conversion region. SOLUTION: The mode shape converter includes a substrate 300, a lower clad 302, the lower rib optical waveguide 304, the core 306, the upper rib optical waveguide 308 and an upper clad 310. The coupling region 312 is a region coupled to an optical fiber and is so designed that the mode of the coupling region has the same size and shape as those of the mode of the optical fiber. This region consists of the double rib optical waveguide structure having the core composed of a single medium and is provided with the upper rib optical waveguide 308 which is the single rib optical waveguide and the lower rib optical waveguide 304 arranged thereunder. The upper rib optical waveguide 308 is connected to the function execution part of the optical element and the lower rib optical waveguide 304 is adjusted in its width and depth in such a manner that the basic mode of the double rib optical waveguide agrees well with the circular mode of the optical fiber.