Long-wave infrared detection based on difference-frequency generation up-conversion

The long-wave infrared (LWIR) band holds critical value in applications such as industrial monitoring, biomedical imaging, and spectral analysis. However, frequency conversion for wavelengths above 5 μm, which covers the core LWIR spectral range, remains challenging due to the limited effective nonlinear coefficients of most optical crystals and severe absorption losses in the mid-infrared to LWIR region, restricting the efficiency of upconversion processes. Meanwhile, mainstream commercial mercury cadmium telluride (HgCdTe) detectors typically require cryogenic operation to achieve high signal-to-noise ratios (SNRs), coupled with high fabrication costs, which severely hinders their widespread deployment under room-temperature conditions. This paper presents a room-temperature LWIR detection device based on frequency upconversion technology, which enables high-sensitivity detection across a broad spectral range (7.5-9 μm) without the need for cooling. Experimental results demonstrate that the system achieves a minimum detectable energy at the fJ level under nanosecond-pulse operation, along with excellent wavelength stability and high responsivity. Compared with typical commercial HgCdTe detectors, the proposed device exhibits a sensitivity improvement of up to approximately 2.4 orders of magnitude at room temperature, significantly enhancing detection accuracy and signal-to-noise ratio for LWIR signals under room temperature conditions. This work provides an effective technical pathway toward the development of room-temperature, low-cost, and high-performance LWIR detection systems, showing promising potential for applications in real-time monitoring, portable sensing, and spectroscopic analysis.