Design of Multi-Wavelength Demultiplexing Coupler Based on DBS Algorithm

The optical coupler can couple the light from the fiber into the waveguide, and the wavelength demultiplexer can split light into different wavelengths. Both devices play a significant role in optical chips, and combing them together can further reduce the chip footprint and improve the operating efficiency. In this work, based on the direct-binary-search (DBS) inverse design algorithm, we design two metamaterial couplers that can realize multiwavelength demultiplexing. The two devices are based on silicon on insulator (SOI) and cover an ultra-compact footprint of 3.6 mu m x 3.6 mu m. The first device can couple and split 1310 nm and 1550 nm light into two separate waveguides with coupling efficiencies of 0.26 and 0.27, respectively. The second device can couple and split 1310 nm, 1490 nm, and 1550 nm light into three separate waveguides with coupling efficiencies of 0.25, 0.2, and 0.23, respectively. This effect is caused by the large number of guide-mode resonances in the device. The two couplers, especially the three-wavelength demultiplexing coupler, can be used as splitters for monolithically silicon-integrated transceivers at the commonly used wavelengths of 1310 nm, 1490 nm, and 1550 nm in the optical fiber communication, which potentially meets the low-cost and ultra-compact requirements for future passive optical networks.