An ultracompact 4/spl times/4 photonic switch based on tapered multimode interference

In this paper, we propose a novel 4/spl times/4 photonic switch based on exponential tapered multimode interference (ETMMI). Based on the exponential structure, the smaller device dimensions compared with conventional MMI can be achieved. Moreover, the power switching between multiple output ports are controlled by changing the refractive indices of the index-modulated regions where such self-images occurred. Simulation is completed by the finite-difference beam propagation method (FD-BPM), and it results less insertion loss <0.59dB and low crosstalk level of <-24.3dB.