Novel Grating Design for Out-of-Plane Coupling With Nonuniform Duty Cycle

We propose a waveguide grating coupler with nonuniform duty cycle for the out-of-plane coupling of light from a planar waveguide to an optical fiber, and evaluate the optical performances based on Bloch-wave analysis. The mode profile and focusing performance of the diffracted output beam are investigated in terms of the duty cycle to improve optical coupling efficiency.