Abstract: The subject to be attained by the disclosed technique is to provide an optical unit less expensive than conventional like optical units and having a wavelength multiplexer and optical waveguides. For achieving the above subject there is provided a wavelength multiplexer wherein a light combining/branching section is constituted by a multi-mode interference type optical waveguide, and an incident-side optical waveguide and a reflection-side optical waveguide are spaced a predetermined distance from each other at their connections to the multi-mode interference type optical waveguide. An optical filter is installed in the multi-mode interference type optical waveguide and a multi-mode interference is set so that a peak in a light intensity distribution is formed in the vicinity of an inlet of each of an exit-side optical waveguide and the reflection-side optical waveguide.

Abstract: The subject to be attained by the disclosed technique is to provide an optical unit less expensive than conventional like optical units and having a wavelength multiplexer and optical waveguides.

Abstract: The subject to be attained by the disclosed technique is to provide an optical unit less expensive than conventional like optical units and having a wavelength multiplexer and optical waveguides. For achieving the above subject there is provided a wavelength multiplexer wherein a light combining/branching section is constituted by a multi-mode interference type optical waveguide, and an incident-side optical waveguide and a reflection-side optical waveguide are spaced a predetermined distance from each other at their connections to the multi-mode interference type optical waveguide. An optical filter is installed in the multi-mode interference type optical waveguide and a multi-mode interference is set so that a peak in a light intensity distribution is formed in the vicinity of an inlet of each of an exit-side optical waveguide and the reflection-side optical waveguide.

Abstract: A method is supported for aligning the height of a polymer waveguide to the height of a core layer of a semiconductor element in an optical module composed so as to mount the semiconductor element on its polymer waveguide substrate. In order to achieve the method, at first a waveguide is formed on the silicon substrate coated with an oxide film using a polymer whose refractive index is larger than that of the oxide film. The waveguide consists of a lower cladding layer, a core layer, and an upper cladding layer. The lower cladding layer is formed to be thinner than the conventional one and the height of the core layer is set to 5 to 10 &mgr;m. In this way, it is possible to fabricate an optical module in less process steps and at a lower cost than the conventional one.

Abstract: The subject to be attained by the disclosed technique is to provide an optical unit less expensive than conventional like optical units and having a wavelength multiplexer and optical waveguides.