Numerical investigation on Ge2Sb2Te5-assisted reconfigurable asymmetric directional coupler-based switches

Abstract

The performance analysis on phase change material germanium-antimony-tellurium-Ge2Sb2Te5 (GST)-assisted silicon waveguide-based non-volatile 1 × 2 and 2 × 2 switches are proposed. The designed structure contains a hybrid silicon waveguide and a regular silicon waveguide. By perfectly choosing the design considerations of the proposed switches, the power of transverse electric mode is coupled and shifted to cross port as an output at the amorphous state of GST (aGST), and for the crystalline state of GST (cGST), the input mode passes through the bar port as an output. The performances of the switches are evaluated by numerical calculations with the help of mode analysis of 2D finite-element method (FEM), and it is further verified by 3D finite-difference time-domain method (FDTD). For the 1 × 2 and 2 × 2 proposed switches, the obtained insertion loss (IL) of both phases of GST is <1 dB. For 1 × 2 switch design, the calculated cross-talk (CT) and extinction ratio (ER) are −31.32 and 31.31 dB, respectively at aGST state and for the cGST state, the values of CT and ER are −20.77 and 20.73 dB at 1550-nm operating wavelength. Similarly, for 2 × 2 switch design, the observed CT and ER are −32.7 and 32.69 dB, correspondingly at aGST state and for the cGST state; they are −11.98 and 11.71 dB, respectively. An additional optimization is realized via variations in the wavelength, GST width, and the coupling gap with the help of FEM analysis. Hence, broadband (80 nm) and ultracompact (∼20 μm) switches are proposed with low IL, high ER, and low CT, which can be suitable for reconfigurable optical interconnects, optical field-programmable gate array applications, microwave photonics, and quantum computing.