CAS Key Laboratory of Quantum Information, USTC, led by academician GUO Guangcan, has achieved new progress in up-conversion image detection. Prof. SHI Baosen, Associate Prof. ZHOU Zhiyuan and their collaborators firstly realize up-conversion phase-contrast image based on sum frequency generation in a quasi-phase matching nonlinear crystal. They also demonstrate the field of view enhancement in the up-conversion process by changing the phase matching condition. The main results have been published on Physical Review Applied [Phys. Rev. Appl., 11, 044013(2019)]. The present image technique will be very promising in biological imaging, pattern recognition and infrared remote sensing.

   Image detectors operating in the infrared range generally suffer from the disadvantages of poor sensitivity, low efficiency, and high cost. An effective method for solving the problem of infrared image detection is to convert the infrared image information into the visible light band by the means of frequency up-conversion, and then to use a visible light band image detector with excellent performance and at a lower price. Phase contrast enhanced imaging is an important image processing technique. Combining the spiral phase contrast edge enhancement technology with the nonlinear sum frequency process to achieve the up-conversion edge enhancement of infrared image information is of great significance for image processing and detection. Prof. SHI Baosen and Asso. Prof. ZHOU Zhiyuan have devoted themselves into frequency conversion of structured light beam for many years. They have studied the propagation, evolution and conservation of optical vortex beam in second harmonics generation and sum frequency generation [Opt. Express 22, 20198(2014); JOSAB 32, 407(2015); Sci Rep. 4, 5650(2014)], and even they have developed the technique to realize the frequency conversion of single photon with structure [Light: Sci.& Appl. 5, e16019(2016); Phys. Rev. Lett. 117, 103601(2016)]. Recently, by applying vortex pump beam in image up-conversion and using a quasi-phase matching PPKTP crystal acting as a nonlinear medium and a spiral phase filter, they realize the up-conversion phase contrast image of an infrared illuminate intensity image. At the same time, a field of view enhancement factor of 2.1 is realized by changing the phase matching condition. The theoretical simulations based on coupling equations are in fully agreement with the experimental results .

  PhD candidate Liu Shikai is the first author of this paper. Prof. SHI Baosen and Asso. Prof. ZHOU Zhiyuan are the corresponding authors. This work is supported by the National Natural Science Foundation of China (NSFC); the National Key Research and Development Program of China; the Anhui Initiative In Quantum Information Technologies; the China Postdoctoral Science Foundation. (Sources: CAS Key Laboratory of Quantum Information, USTC; Innovative Center for Quantum Information and Quantum Physics, CAS; and the Ministry of Science and Technology)

  Sources：LEDinside