Low-polarization- sensitive and wideband 1×2 carrier-injection-type silicon photonics switch with mode conversion and...

We demonstrate a polarization-independent silicon photonics optical switch based on mode conversion and interference of multimode interferometers (MMIs). The proposed architecture consists of a mode converter for TE and TM separation and TM to TE conversion, a cascaded MMIs for forming inner and outer Mach-Zehnder Interferometer, phase shifters using thermal heater and pn-junction, and a 4×2 asymmetric MMI for combining TE and TM (converted to TE). This architecture converts the input TM mode into a first-order TE mode and splits it into two fundamental TE modes. It employs asymmetric MMI structures to route both TE and TM inputs to the same output ports via inner and outer interferometers, respectively. This approach significantly reduces device complexity while maintaining polarization-independent operation. The device design is presented together with an analysis of the wavelength dependence of insertion loss and polarization-dependent loss (PDL). A practical calibration method is developed to compensate for the phase difference of TE and TM modes using a limited number of electrical control parameters. Experimental results show stable continuous wave switching with low crosstalk, PDL below 3.4 dB over the C band, and robust operation against wavelength and temperature variations. Bit-error-rate measurements at 25 Gb/s with OOK modulation format confirm a power penalty below 1 dB for all tested polarization states and output ports. The wavelength dependence observed for mixed TE/TM input states is analyzed based on group-delay imbalance between interfering optical paths, showing good agreement between calculated and measured free spectral ranges. These results indicate that the proposed polarization-independent optical switch is a promising building block for low-latency, high-throughput optical interconnects in future data-center and computing systems.