Vertical Coupling Between Waveguides and Optical Fibers Utilizing Polarization Gratings

Abstract

We present how a conventional Si waveguide grating coupler can be integrated with a polymerizable liquid crystal polarization grating to provide vertical coupling between optical fibers and planar waveguides. The implementation involves the deposition of a liquid crystal polymer film onto the surface of the planarized photonic chip. To achieve optimal performance, both the period and thickness of the thin film grating are optimized through a two-dimensional finite element simulation. The simulation results indicate that the output beam can be entirely redirected towards the vertical direction. We demonstrate a fabricated device and experimental validation of the proposed device in a laboratory setting. Through the verification, we affirm the feasibility of the proposed concept.