A compact and low‐loss 1 × 2 wavelength MUX/DEMUX based on a multimode‐interference coupler using quasi state

In this paper, we propose a compact multimode‐interference‐based wavelength MUX/DEMUX. By using the quasi‐output state, the device length can be greatly reduced. The device performances are numerically investigated by using the finite‐difference beam‐propagation method (FD‐BPM). Simulation results show that the device performances, in terms of coupling loss and extinction ratio, are enhanced.