| Summary: | An optical switch based on silicon-on-insulator (SOI) technology is proposed that works in the C-band and switches by amorphous (Am) to crystalline (Cr) and Cr-to-Am phase transitions. The optical switch integrates the functions of polarization beam splitting and mode conversion, and consists of two asymmetric directional couplers (ADCs). The TM<sub>0</sub> mode is converted to the TM<sub>1</sub> mode through an asymmetric coupler to achieve the polarization splitting of the TM<sub>0</sub> mode and TE<sub>0</sub> mode. The output of the TE<sub>0</sub> mode is then controlled by Ge<sub>2</sub>Sb<sub>2</sub>Se<sub>4</sub>Te<sub>1</sub> (GSST). When the TE<sub>0</sub> mode is input and the wavelength is 1550 nm, the insertion loss (IL) is lower than 0.62 dB and the crosstalk (<i>CT</i>) is lower than −9.88 dB for a directional coupler loaded with GSST that realizes the optical switch function in both amorphous and crystalline GSST. The extinction ratio (ER) of the two waveguides of the directional coupler is lower than −11.40 dB, simultaneously. When the TM<sub>0</sub> mode is input and the wavelength is 1550 nm, the IL is lower than 0.62 dB for a directional coupler loaded without GSST.
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