2-μm Ultra-broadband polarization beam splitter with tunable transmissions based on silicon-Ge2Sb2Se4Te1 hybrid subwavelength gratings

Recently, integrated optical devices working at 2-mu m wavelengths have attracted considerable attention. Among such devices, a polarization beam splitter is an essential building block for constructing the on-chip circuit. Here, we have proposed an ultra-broadband polarization beam splitter with tunable transmissions working at 2-mu m waveband. Coupled-mode based directional coupler is utilized for the device design. Subwavelength grating structures provide efficient dispersion control, which endows broad optical bandwidths. In addition, a rear-bent coupler is cascaded at the output of the device to furtherly suppress the crosstalk. The silicon-Ge2Sb2Se4Te1 hybrid materials provide tunable transmissions. When the Ge2Sb2Se4Te1 is in the amorphous state, with high extinction ratios more than 20 dB, the bandwidths exceed 200 nm (1900 similar to 2100 nm) and 130 nm (1925 similar to 2055 nm) for TE0 and TM0, respectively. Furthermore, the insertion losses are less than 0.24 dB (1900 similar to 2100 nm) and 0.56 dB (1925 similar to 2055 nm) for TE0 and TM0, respectively. When being in the crystalline state, the device works as an absorber that fully attenuates the input energy. In different intermediate amorphous-crystalline hybrid states, it is also possible to achieve tunable transmissions.

Automated summary

This article proposes an ultra-broadband polarization beam splitter working at 2-μm wavelengths. It utilizes a coupled-mode based directional coupler and subwavelength grating structures for efficient dispersion control. The device can achieve tunable transmissions in different material states.