Broadband on-chip spectral sensing via directly integrated narrowband plasmonic filters for computational...

Spectroscopy underpins a wide range of applications, including biomedical diagnostics, precision agriculture, remote sensing, and industrial process control. Recent advances in silicon and microwave photonic integration have facilitated the miniaturization of spectroscopic systems, enabling portable, real-time analysis. However, the realization of a chip-scale platform that simultaneously achieves broadband coverage, high resolution, and scalable low-cost fabrication - particularly in the near-infrared (NIR) regime - remains a significant challenge. Here, we present a compact and cost-effective NIR spectroscopic sensing chip that monolithically integrates a plasmonic bandpass filter array with InGaAs photodetectors. The device is fabricated via single-step lithography and features a nanohole array with geometrically tunable narrowband transmission spanning 900-1,700 nm, exhibiting a full width at half maximum (FWHM) of 5.0 nm and a peak Q-factor of ∼284. The plasmonic filters are directly integrated with the detectors through a SiN _x spacer layer, eliminating post-fabrication alignment and enhancing scalability. A 16-channel super-pixel layout, combined with computational spectral reconstruction, enables ∼1 nm resolution near 1,550 nm and supports high-fidelity spectral imaging. This work demonstrates a scalable, detector-compatible approach to on-chip NIR spectroscopy, offering a promising route toward deployable, compact spectral sensing platforms.