Mid-infrared temporal ghost imaging via two-photon structured encoding

TL;DR

This paper introduces a novel broadband mid-infrared temporal ghost imaging system using non-degenerate two-photon absorption, enabling ultrafast, sensitive, and broadband MIR temporal detection without complex alignment.

Contribution

It demonstrates a practical MIR TGI system that overcomes phase-matching and spectral coverage limitations through a simple, alignment-free approach using near-infrared pump modulation.

Findings

Reconstructed temporal waveforms exceed detector bandwidth by over 40 times.

Achieved detection sensitivity of 0.05 pJ/pulse.

Supported broadband operation from 2.5 to 3.8 micrometers.

Abstract

Temporal ghost imaging (TGI) enables ultrafast signal reconstruction beyond electronic bandwidth limits. Extending this concept to the mid-infrared (MIR) regime through nonlinear frequency conversion offers new opportunities for high-fidelity temporal detection, but remains constrained by stringent phase-matching condition, limited spectral coverage, and intricate optical alignment. Here, we propose and demonstrate a broadband MIR TGI system based on non-degenerate two-photon absorption. A temporally encoded near-infrared pump transfers structured modulation onto a MIR signal directly at a silicon detector, which facilitates concurrent modulation and detection without external nonlinear crystals. The reconstructed temporal waveforms exceed the detector bandwidth by more than fortyfold, achieve a detection sensitivity of 0.05 pJ/pulse, allow compressed sensing with 80\% fewer measurements, and support broadband operation across 2.5-3.8 $\mu$m. This compact, alignment-free, and room-temperature system establishes a practical route for fast and sensitive MIR time-domain analysis, holding great promise for applications in time-resolved molecular spectroscopy, high-precision infrared ranging, and high-speed free-space communication.