Abstract: Sensitive detection of mid-infrared photons and precise modulation of optical fields have always been challenging. Using the frequency upconversion imaging technique with multi-dimensional optical field modulation, the researchers have advanced the helical phase contrast technique to the mid-infrared band for the first time, and are the first to realise single-photon mid-infrared edge imaging. The technique can simultaneously achieve high-efficiency wavelength conversion and high-fidelity phase preparation, circumventing the shortcomings of traditional mid-infrared detection and modulation devices, and obtaining highly sensitive mid-infrared edge-enhanced imaging through a silicon-based camera.
Keywords: edge-enhanced, infrared imaging, frequency upconversion, single-photon detection
Edge-enhanced detection can effectively achieve target detection by identifying the contours of objects, which has important applications in the fields of machine vision and intelligent identification, and spiral phase contrast technology provides an effective way to achieve edge-enhanced imaging. With the urgent application needs in infrared molecular spectroscopy, military infrared monitoring, label-free bio-imaging, and remote sensing of environmental gases, it is particularly important to extend the working wavelength of edge-enhanced imaging to the mid-infrared band.
Based on the mid-infrared nonlinear frequency upconversion imaging system, Professor Zeng Heping, researcher Huang Kun and their collaborators at the State Key Laboratory of Precision Spectroscopy Science and Technology of East China Normal University have achieved the first ultra-sensitive mid-infrared edge-enhanced imaging, which organically combines the spiral phase contrast technology and frequency upconversion imaging technology to coherently convert the infrared optical field to the visible wavelength band, and significantly improve the conversion efficiency with the time-frequency-domain-controlled synchronous pulse pumping technology. technology, which significantly improves the conversion efficiency and reduces the background noise. In the experiments, the team realised two-dimensional imaging in the mid-infrared at the single-photon level at a very low illumination of 0.5 photons/pulse by using a highly sensitive silicon-based electron-multiplying CCD (EMCCD) camera. Further, by introducing a pump light field carrying the vortex phase in the nonlinear mixing process, the helical phase can be loaded onto the spectral components of the mid-infrared Fourier space with high fidelity, thus realising ultra-sensitive mid-infrared edge-enhanced imaging.
This achievement provides a feasible way for ultra-sensitive mid-infrared imaging under room temperature conditions, and is expected to solve the technical problem of precision phase modulation in broadband infrared optical fields, which has important potential value in the fields of semiconductor defect detection, infrared astronomical observation, micro-optical image recognition, and deep tissue imaging. The paper is published online in Laser & Photonics Reviews.
Source : https://mp.weixin.qq.com/s/y2hnrjL--kM2G9TsASSV3Q
