Ultracompact and fabrication-tolerant integrated polarization splitter

Design and fabrication of a 2×2 two-mode interference (TMI) coupler based on-chip polarization splitter is presented. By changing the angle between the access waveguides, one can tune the effective TMI length for the mode with less optical confinement (transverse magnetic, TM) to coincide with the target TMI length for a desired transmission of the mode with higher optical confinement (transverse electric, TE). The fabricated 0.94 μm long 2×2 TMI splits the input power into TM (bar) and TE (cross) outputs with splitting ratio over 15 dB over 50 nm bandwidth. Fabrication tolerance analysis shows that the device is tolerant to fabrication errors as large as 60 nm.