On-chip multifunctional polarizer based on phase change material

Polarizers are used to eliminate the undesired polarization state and maintain the other one. The phase change material Ge₂Sb₂Se₄Te₁ (GSST) has been widely studied for providing reconfigurable function in optical systems. In this paper, based on a silicon waveguide embedded with a GSST, which is able to absorb light by taking advantage of the relatively large imaginary part of its refractive index in the crystalline state, a multifunctional polarizer with transverse electric (TE) and transverse magnetic (TM) passages has been designed. The interconversion between the two types of polarizers relies only on the state switching of GSST. The size of the device is 7.5µm∗4.3µm, and the simulation results showed that the extinction ratio of the TE-pass polarizer is 45.37 dB and the insertion loss is 1.10 dB at the wavelength of 1550 nm, while the extinction ratio (ER) of the TM-pass polarizer is 20.09 dB and the insertion loss (IL) is 1.35 dB. For the TE-pass polarizer, a bandwidth broader than 200 nm is achieved with ER>20dB and IL<2.0dB over the wavelength region from 1450 to 1650 nm  and for the TM-pass polarizer, ER>15dB and IL<1.5dB in the wavelength region from 1525 to 1600 nm, with a bandwidth of approximately 75 nm.