A Compact, 4-Channel CWDM Demultiplexer Optimized Using Energy Constrained Inverse Design

A four-channel coarse wavelength division multiplexing (CWDM) (de)multiplexer with 50 nm channel spacing and $10\mu\mathrm{m}\times 10\mu\mathrm{m}$ footprint is designed with an energy constrained inverse design method, providing low loss, crosstalk. Specifically, the optimized design has a $< 0.8$ IL, $<-14\text{dB}$ crosstalk. The optimization takes approximately 40 hours with a multi-GPU Maxwell equation solver. The optimized design validates the benefits of the proposed topological inverse design with energy constraint for more complex devices.