An Inverse-Design Wavelength Demultiplexer for On-Chip Photoluminescence Sorting in TMDC Heterostructures

Emerging two-dimensional transition metal dichalcogenides (TMDCs) offer a promising platform for on-chip integrated photonics because of their unique optical and electronic properties. Their naturally passivated surfaces make them highly tolerant to lattice mismatch, enabling seamless heterogeneous integration by stacking different van der Waals materials, a crucial step in the development of advanced photonic devices. In this work, we present an inverse-design wavelength demultiplexing waveguide capable of separating three distinct wavelengths. We further showcase its application in sorting and routing of distinct photoluminescence from the heterojunction formed by WS₂ and WSe₂ monolayers. The integrated nanophotonic chip splits and directs excitonic emission into individual waveguides at both room and cryogenic temperatures. Our demonstration opens new perspectives for integrating light sources in van der Waals materials with functional integrated photonics, offering a versatile platform for both fundamental research and practical applications.