Broadband and high-resolution snapshot spectroscopy with high-index transition metal dichalcogenides.

Computational spectroscopy is a powerful tool across numerous disciplines, yet its development remains constrained by limited bandwidth and low light throughput of spectral encoders, which are inherent to optical materials and design frameworks. Here we overcome these challenges using transition metal dichalcogenides (TMDCs), leveraging their high refractive index (n > 4) and broadband transparency to achieve optical manipulation. This enables broadband spectral encoders that modulate light from the visible to short-wave infrared while maintaining light throughput above 65%. These characteristics originate from the high-index-contrast interface with optical feedback, which extends optical path length and augments the photon density of states, accelerating multi-beam phase accumulation within TMDCs. By integrating encoders with InGaAs photodetectors, we construct a snapshot spectrometer with remarkable performance, featuring a wavelength accuracy of 0.02 nm, a spectral resolution of 1 nm, and a detection limit below 1 nW. We further demonstrate the application of this spectrometer in material identification, highlighting its versatility for real-world deployment.