Reconfigurable Mode (De) Multiplexer via 3-D Triple-Waveguide Directional Coupler With Optical Phase Change Material

Abstract

A three-dimensional reconfigurable mode (de) multiplexer (3DRM-(De)MUX) is proposed based on a triple-waveguide directional coupler with optical phase change material, which consists of an input waveguide on the upper layer, a bus waveguide on the lower layer, and an intermediate waveguide on the upper layer with a Ge2Sb2Se4Te1 (GSST) cap layer. The self-holding “ off ” and “ on ” states of the proposed 3DRM-(De)MUX can be switched by triggering the amorphous and crystalline states of GSST, respectively. The proposed 3DRM-(De)MUX is optimized by using the full-vectorial finite element method and 3-D full-vectorial finite difference time domain method. The simulated results show that the proposed 3DRM-(De)MUX for switching between the quasi-TE0 and quasi-TE1 modes is with a compact coupling length of only 12.0 μm, a broad bandwidth of 100 nm, the mode extinction ratios of 18.25 dB and 14.0 dB, and the insertion losses (ILs) of –0.38 and –1.14 dB for the “ off ” and “ on ” states, respectively. A more compact 3DRM-(De)MUX can also be achieved for the quasi-TM1 mode with the coupling length of 8.28 μm, IL of –0.12 dB (–1.98 dB), and mode crosstalk of –16.37 dB (–13.23 dB) for the “ off ” (“ on ”) state, respectively. The proposed 3DRM-(De)MUX can be applied in 3-D on-chip mode division multiplexing networks for flexible mode routing and switching.