Integrated SU-8 Prisms and Microgratings for Polarization-Selective Fiber-to-Silicon Waveguide Coupling

A polarization-selective fiber-to-silicon waveguide coupler made by an SU-8 prism as well as a micrograting is demonstrated. The size of the SU-8 prism well matches the core dimension of a single-mode fiber to increase the coupling efficiency, and the micrograting provides the selectivity of polarization mode coupling. Only the TE wave is able to be coupled to the silicon waveguide. The measured coupling loss of the SU-8 prism and the micrograting is 4.5 dB. The polarization extinction ratio is 20 dB. The fiber misalignment tolerances are 2 and 3 μ m for the x- (lateral) and y- (vertical) directions, respectively, according to a transmission window of 3-dB drop.