Abstract: An optical branching unit according to the invention, has on a substrate, a light input part which inputs light, an optical branch which branches the light input to the light input part at a predetermined ratio, a light output part which guides the light branched by the optical branch to a predetermined position, and a dummy pattern which is provided on a substrate independently of an area provided with the light input part, optical branch and light output part, made of the same material as the light input part, optical branch and light output part, and defined to have an area, so that an occupation rate, or a ratio of the dummy pattern to the area of a substrate except the light input part, optical branch and light output part, is 70% or higher.

Abstract: An optical waveguide circuit component according to the present invention is characterized by that a clad layer composed of quartz is provided on the surfaces of a substrate and core formed by quartz doped selectively on a quartz plate structure, and a lid or a cover member is fixed onto the clad layer by heat pressing. With this structure, it is possible to reduce the magnitude of a polarization-dependent loss (PDL) generated when the lid and clad layer are combined.

Abstract: A group III nitride semiconductor film involving few lattice defects and having a large thickness, and a process for making the film are disclosed. Dry-etching is conducted while a quartz substrate and a group III nitride semiconductor are placed on the top of a lower electrode. Nano-pillars (50) are formed on the top of the group III nitride semiconductor (101). Another group III nitride semiconductor film (51) is deposited on the nano-pillars (50).