Polarization separator, and an optical device

Polarization separator according to the embodiment of the present invention, the demultiplexer (11), a multiplexer (14), a first arm waveguide (12 at least part of which is formed by a rib waveguide ) and is provided with a second arm waveguide formed at least in part by a channel waveguide (13), the. In one of the linearly polarized light components perpendicular to each other, the refractive index of the first arm waveguide (12) and the second arm waveguide for input light (13) are the same, and the refractive index change with respect to a change in waveguide width There are formed first and second arm waveguides in waveguide width as the same. The other linearly polarized light component, a phase difference between said second input light propagating through the first input light and the second arm waveguide for propagating the first arm waveguide (12) (13) It is causing.