Noise-tolerance detection of high-frequency dynamic targets with mid-infrared thermal radiation via intra-cavity enhanced upconversion

Broadband and highly sensitive mid-infrared (MIR) light detection and imaging play a crucial role in environmental monitoring, gas detection, biomedical applications, and national defense security. However, the detection of high-frequency, long-distance dynamic targets with MIR thermal emission is still limited by the long response time of commercial detectors and intense environmental noise. Here, we demonstrate a noise-tolerance intra-cavity enhanced broadband MIR upconversion system by counting the upconverted lights through a high-sensitivity single photon detector. The intra-cavity enhanced pump power of 1064 nm reaches about 200 W, resulting in a high upconversion efficiency with the MIR spectra ranging from 3 µm to 5 µm. By performing discrete Fourier transformations of the arrival time of each upconverted photon, the frequency-domain imaging manifests a strong noise-tolerance feature, even under the ratio of the noise-to-signal of up to 100. The excellent performance of our system has also been evidenced by measuring the rotation frequency of a turbojet engine in outdoor conditions. Our proposal offers promising applications to recognize long-distance dynamic targets, such as airplanes and unmanned aerial vehicles, in real-world scenarios with the highly desired suppression of intense background noise and stray light.