Integrated Hybrid Mode‐Wavelength Demultiplexers Based on Cascaded Digital Metamaterials

Abstract

High‐dimensional multiplexing technology is of importance in the on‐chip photonic interconnections and challenging to design within ultracompact footprint. Herein, high‐dimensional demultiplexers are proposed and demonstrated to enable wavelength‐division and mode‐division simultaneously. The functional regions of digital metamaterials are obtained by inverse design individually and are cascaded to work as high‐dimensional demultiplexers. The gradient‐based inverse design is carried out with an efficient method combining finite‐element method, density method, and method of moving asymptotes. The performances are simulated by 3D finite difference time domain with silicon‐on‐insulator configuration. The proposed demultiplexer with four‐channel has ultracompact footprint of 4.1 × 3.65 μm2. Its average transmission efficiency is 38.7% and contrast ratios are higher than 13.0 dB. Besides, the proposed demultiplexer with six‐channel has a footprint of 4.55 × 5.55 μm2. Its average transmission efficiency is 24.3% and contrast ratios are higher than 11.8 dB.