Polarization beam splitter and optical device

A polarization beam splitter comprising:

• a demultiplexer that demultiplexes input light into first input light and second input light;
• a multiplexer that multiplexes the first input light and the second input light, the first input light and the second input light being obtained by demultiplexing the input light by the demultiplexer;
• a first arm waveguide that guides the first input light to the multiplexer, at least a part of the first arm waveguide being formed of a rib waveguide;
• and
• a second arm waveguide that guides the second input light to the multiplexer, at least a part of the second arm waveguide being formed of a channel waveguide, wherein
• the first and second arm waveguides are formed with a waveguide width at which, in one of linear polarization components orthogonal to each other, a refractive index of the first arm waveguide with respect to the input light is the same as a refractive index of the second arm waveguide with respect to the input light and a refractive index change of the first arm waveguide with respect to a change in the waveguide width is the same as a refractive index change of the second arm waveguide with respect to a change in the waveguide width, and
• in the other one of the orthogonal polarization components, a phase difference is generated between the first input light propagating through the first arm waveguide and the second input light propagating through the second arm waveguide.