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Applied Physics Letters

Ultrasensitive mid-infrared up-conversion imaging at few-photon level

Qian Zhou, Kun Huang, Haifeng Pan, E Wu, Heping Zeng

Published Jun 17, 2013• 43 citations
Publisher

Abstract

We demonstrated few-photon-level mid-infrared imaging at 3.39 μm by efficient frequency up-conversion. The quantum frequency up-conversion efficiency of mid-infrared photons was high to 32.9%, while mid-infrared images were up-converted with the quantum efficiency of 12.5%. The mid-infrared imaging sensitivity was improved by counting the frequency up-conversion photons temporally confined within the time-window of the pump pulse. The frequency up-conversion system induced a background noise of 1.1 × 103 counts per second.

DOI
10.1063/1.4811826

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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Nov 29, 2012•0 citations
We demonstrated few-photon-level mid-infrared imaging at 3.39 μm by efficient frequency up-conversion. The quantum frequency up-conversion efficiency of mid-infrared photons was high to 32.9%, while mid-infrared images were up-converted with the quantum efficiency of 12.5%. The mid-infrared imaging sensitivity was improved by counting the frequency up-conversion photons temporally confined within the time-window of the pump pulse. The frequency up-conversion system induced a background noise of 1.1 × 103 counts per second.
We demonstrate an efficient mid-infrared single-photon detection system with ultra-low background counts based on the frequency upconversion detection technique. The signal photons of 3.39 μm came from a He–Ne laser and the pump beam was provided by a mode-locked ytterbium-doped fiber laser. Taking into account the pulsed pumping and continuous-wave signaling scheme, the peak conversion efficiency of 64% was achieved at an average pump power of 28.3 mW. The corresponding detection efficiency was inferred to be 6.1% with ultra-low background counts of 400 s −1 .
Mid-infrared (MIR) detection remains challenging due to limited detector sensitivity and strong background noise. Frequency up-conversion enables MIR detection with visible-range detectors but suffers from limited robustness and additional noise generated in the nonlinear process. We demonstrate a quantum-enhanced MIR frequency up-conversion detection system that generates strongly non-degenerate, time-correlated photon pairs via spontaneous parametric down-conversion and detects MIR photons under severe loss and noise. With a 62 dB transmission loss and background noise 28 times higher than the detected signal, the quantum signal-to-noise ratio substantially surpasses that of classical photon counting. The system achieves stable signal retrieval under unpredictable noise fluctuations, highlighting its robustness in dynamically varying environments. These results establish a basis for practical sensing and imaging applications of quantum-enhanced MIR detection.
Single-photon frequency upconversion is an effective method of infrared single-photon detection and imaging by converting the long-wavelength photons to shorter wavelengths to match the detector’s spectral response. We realized few-photon level 2D infrared imaging with a coincidence frequency upconversion system in a bulk periodically poled lithium niobate crystal. Moreover, the infrared photons carrying orbital angular momentum were converted to the visible regime with high efficiency, while the orbital angular momentum of the photons was well conserved during the frequency upconversion process. The single-photon frequency upconversion method was also used for mid-infrared imaging at 3.39 µm with high efficiency and low noise.
We experimentally demonstrate a pulsed mid-infrared photon source at 3.16 μm with a bandwidth of 3.7 nm by coincidence frequency downconversion with a conversion efficiency of 65%. The mid-infrared photons were generated by frequency downconversion in the saturation regime where the signal photons at 1.04 μm were synchronously pumped by intense laser pulses at 1.55 μm. In principle, the mid-infrared photon source could not only inherit the complete quantum characteristics of the input photon state, but could also be coherently manipulated in the spectral and temporal domains by engineering the classical pump field.