Experimental research on an integrated thermooptic switch based on multimode interference couplers

Abstract

The experimental results of a 2?2 integrated thermooptic Mach-Zehnder interferometer (MZI) switch based on multimode interference (MMI) couplers are reported. The insertion loss (IL) is 3.40 dB, the polarization dependent loss is 0.47 dB, the extinction ratio (ER) at bar state and cross state is 32.01 dB and 16.42 dB respectively, the response time is less than 3 ms, and the power consumption is 658 mW. Regarding the asymmetry of extinction ratio at bar state and cross state, theoretical analysis is first presented. The coupling ratio of the two MMI couplers deviates from 50 : 50 but the deviation is nearly the same, which is decided by good uniformity of semiconductor planar lightwave circuit (PLC) process. This property affects the extinction ratio at bar state and cross state in different mechanisms. Adding a metal electrode on the waveguide affects its effective index and analysis based on experimental results is given. The increment of waveguide effective index is in the order of 2?10^-4.