Polarization independent 4 channel demultiplexer using multi-mode interferometers in InP/InGaAsP

We have designed and fabricated polarization independent 4 channel demultiplexer with a deep ridge structure using 1/spl times/4 and 4/spl times/4 multimode interferometers (MMIs) in InP-InGaAsP. The crosstalk was well below -15 dB for all output channels.