# Hyper-spectral Imaging with Up-Converted Mid-Infrared Single-Photons

## TL;DR

This paper introduces a novel quantum-enabled hyperspectral imaging system that uses up-converted mid-infrared single photons, enabling high-contrast, label-free imaging at ultralow photon flux with room-temperature detectors.

## Contribution

It combines cavity-enhanced SPDC with nonlinear up-conversion to achieve MIR spectral imaging using visible silicon detectors at room temperature, a significant advancement over traditional MIR imaging methods.

## Key findings

- Demonstrated chemically specific imaging in the 2.9-3.6 μm range.
- Achieved high-contrast, label-free imaging at ultralow photon flux.
- Supported biological and polymer samples with high efficiency.

## Abstract

Hyperspectral imaging in the mid-infrared (MIR) spectral range provides unique molecular specificity by probing fundamental vibrational modes of molecular bonds, making it highly valuable for biomedical and biochemical applications. However, conventional MIR imaging techniques often rely on high-intensity illumination that can induce photodamage in sensitive biological tissues. Single-photon MIR imaging offers a label-free, non-invasive alternative, yet its adoption is hindered by the lack of efficient, room-temperature MIR single-photon detectors. We present a single-photon hyperspectral imaging platform that combines cavity-enhanced spontaneous parametric down-conversion (SPDC) with nonlinear frequency up-conversion. This approach enables MIR spectral imaging using cost-effective, visible-wavelength silicon single-photon avalanche diodes (Si-SPADs), supporting room-temperature, low-noise, and high-efficiency operation. Time-correlated photon pairs generated via SPDC suppress classical intensity noise, enabling near shot-noise-limited hyperspectral imaging. We demonstrate chemically specific single-photon imaging across the \SIrange{2.9}{3.6}{\micro\meter} range on biological (egg yolk, yeast) and polymeric (polystyrene, polyethylene) samples. The system delivers high-contrast, label-free imaging at ultralow photon flux, overcoming key limitations of current MIR technologies. This platform paves the way toward scalable, quantum-enabled MIR imaging for applications in molecular diagnostics, environmental sensing, and biomedical research.