Polarization-insensitive thermo-optic Mach–Zehnder switches on silicon

Polarization-insensitive photonic switches are crucial for the case with random polarization states encountered in optical systems. In this paper, we propose and demonstrate a polarization-insensitive 2 × 2 thermo-optic Mach-Zehnder switch (PIMZS) on a 340-nm silicon-on-insulator (SOI) platform by incorporating low-loss polarization-insensitive multimode interference (PIMMI) couplers whose core width is varied optimally. The fabricated 2 × 2 PIMZS exhibits a low excess loss of 0.15-0.79 dB and a high extinction ratio of >24 dB for both polarizations, and low polarization-dependent loss (PDL) of <0.47 dB is achieved across the C-band.