Design of compact 1×4 fully non-blocking silicon-photonic mode selective switch

We propose a novel 1×4 non-blocking four-mode selection switch on a silicon-on-insulator (SOI) substrate. It comprises one Y-Junction coupler, six Phase Shifters (PS), and three Multimode Interferences (MMI). While the Y-Junction is designed to divide modes at the input of the device, the MMIs direct signals from its inputs to suitable outputs by adjusting the value of the Phase Shifters. The outstanding feature is that the proposed switch allows the four input modes ( \(\hbox {TE}_0\) ${\text{TE}}_0$ − \(\hbox {TE}_1\) ${\text{TE}}_1$ − \(\hbox {TE}_2\) ${\text{TE}}_2$ − \(\hbox {TE}_3\) ${\text{TE}}_3$ ) to be guided simultaneously or sequentially to the desired output without any discontinuation. Through BPM-3D beam propagation with the EIM effective index method, it is shown that the device is capable of smoothly switching concurrently or, in turn, the four modes mentioned above from any input to any output with insertion loss (IL) being smaller than 0.1 dB at the central wavelength 1.55 \(\mu\) $\mu$ m, and crosstalk (CT) being from −48 dB to −19 dB for the entire C band.