Image quality improved 1X8 multi-mode interference coupler

摘要

A novel design of multimode interference coupler with deeply etched air trenches at the boundary of the multimode section is proposed for photonic integrated circuitry on low-index-contrast materials. The device length decreases from 820μm to 750μm for a 1X8 polymer multimode interference coupler. Due to the enhanced optical confinement, the optimized coupler with air trenches experimentally achieved 0.28/0.23dB reduced insertion loss, 2.16/2.34dB improved contrast ratio for TE and TM polarization, compared with conventional multimode interference coupler. The device entirely covers the wavelength range of both C-band and L-band, which is sufficient for broad band communication.