Reconfigurable Mode (De) Multiplexer Using Ge2Sb2Se4Te1 Based Triple-Silicon-Waveguide

A reconfigurable mode (de) multiplexer [(De) MUX] is proposed based on a triple-silicon-waveguide directional coupler, consisting of a central waveguide with a Ge2Sb2Se4Te1 (GSST) upper layer and two outer silicon waveguides. The output mode states can be switched by the self-holding phase transition between the amorphous and crystalline states of the GSST layer, and a low loss of the proposed device can be achieved benefiting from the low propagation losses of the GSST at both states. The proposed reconfigurable mode (De) MUX is optimized by using the full-vectorial finite-element method and the thee-dimensional full-vectorial finite-difference time-domain method. The numerical results reveal that the proposed reconfigurable mode (De) MUX is with a compact length of 17.65 mu m, insertion losses of 0.16 and 0.96 dB, and mode crosstalk of -15.91 and -26.97 dB at ON and OFF states, respectively. The proposed reconfigurable mode (De) MUX can operate over the S + C + L band with high performance. The fabrication tolerances are also studied in detail.