Fig. 1. Simple diagram for spectrum transducing detection

Fig. 2. Noise distributions under short wavelength and long wavelength pumping. (a) Under short wavelength pumping; (b) Under long wavelength pumping

Fig. 3. Detection field of view for image detection with spectrum transducing

Fig. 4. Optical configurations that can be used to realize spectrum transducing detection. (a) Bulk PPLN crystal; (b) Bulk PPLN crystal in cavity; (c) PPLN ridge waveguide (image is taken from: https://www.opt-ron.com/product/hcp_ppln-chips); (d) PPLN nano-film structure (image is taken from: https://www.researching.cn/articles/OJ69ad0db15f1eb037)

Fig. 5. Large frequency acceptance bandwidth in spectrum transducing detection based on different methods. (a) Chirped quasi-phase matching crystal; (b) A group of multi-crystals with different cutting angles

Fig. 6. The principle for realizing large field of view in spectrum transducing image based on chirped poling crystals (image is taken from reference [36])

Fig. 7. Building up quantum frequency interface between atomic system and telecommunication channel based on spectrum transducing (image is taken from reference [43])

Fig. 8. Phase contrast imaging is realized in spectrum transducing imaging by pumping with vortex light (image is taken from reference [45])