# Advances in Photonic Gas Sensors Operating in the VIS–NIR Spectrum: Structures, Materials, and Performance

## TL;DR

This paper reviews advances in photonic gas sensors using VIS–NIR spectrum technologies, covering materials, structures, and performance improvements.

## Contribution

The paper provides a comprehensive overview of PIC-based gas sensors, comparing materials and device topologies with performance benchmarks.

## Key findings

- Photonic Integrated Circuits (PICs) offer high sensitivity and selectivity for gas sensing.
- Materials like silicon, silicon nitride, polymers, and 2D materials are compared for PIC gas sensors.
- Artificial intelligence is highlighted as a promising technology for autonomous gas sensing devices.

## Abstract

The growing need for real-time, accurate monitoring of hazardous gases in environmental, industrial, and healthcare settings has highlighted the limitations of traditional sensing methods. Photonic Integrated Circuits (PICs) have become a revolutionary platform due to their high sensitivity, accurate selectivity, compact size and cost-effectiveness. We present in this work a comprehensive overview of the best-reported PIC-based gas sensors. We discuss the basic concepts behind resonance-based and absorption-based sensing. A detailed overview of the various material platforms, from well-known silicon and silicon nitride to new polymers, chalcogenide glasses, and 2D materials, is presented. A comparison of key device topologies, such as waveguides, microring resonators, Mach–Zehnder interferometers, and metasurfaces, is conducted, with performance benchmarks indicating the limit of detection (LoD). The main limitations of PIC sensors are discussed in this review. We also discuss promising technologies, especially the game-changing potential of artificial intelligence to create fully autonomous devices.