Fig. 1. Concept diagram of a high-quality quantum light source based on lithium niobate crystals

Fig. 2. Tuning curves and spatial distributions under temperatures of 30 ℃, 60 ℃, and 90 ℃. (a)‒(c) Tuning curves corresponding to single pump wavelength (vertical line represents a degenerate signal wavelength at 3194 nm, and the horizontal line represents a 0° angle); (d)‒(f) spatial distributions corresponding to single pump wavelength and single signal wavelength (adding a narrow band filter with a central wavelength of 3194 nm); (g)‒(i) distributions of signal light along the x-direction at y=0

Fig. 3. Schmidt number S corresponding to different crystal temperatures T (red dots represent the calculated data points). (a) Range from 30 ℃ to 90 ℃; (b) range from 59 ℃ to 60 ℃ (inset: spatial distribution along x-axis at 59.5 ℃)

Fig. 4. Simulation results for a single pump wavelength and multiple signal wavelengths model. (a)-(c) Spatial distributions of the signal light at 30 ℃, 60 ℃, and 90 ℃, where a broadband filter with a central wavelength of 3194 nm and a bandwidth of 100 nm is added; (d)-(f) distributions of signal light along x-direction at y=0

Fig. 5. Simulation results for multiple pump wavelength and multiple signal wavelength model. (a)‒(c) Spatial distributions of the signal light at 30 ℃, 60 ℃, and 90 ℃, where a broadband filter with a central wavelength of 3194 nm and a bandwidth of 100 nm is added; (d)‒(f) distributions of signal light along x-direction at y=0

Fig. 6. Simulation results for multiple pump wavelength and multiple idler wavelength model. (a)‒(c) Spatial distributions of idler light at 30 ℃, 60 ℃, and 90 ℃, where a broadband filter with a central wavelength of 3194 nm and a bandwidth of 100 nm is added; (d)‒(f) distributions of idler light along x-direction at y=0

Fig. 7. Frequency-domain and spatial-domain distributions under a temperature of 24.5 ℃. (a) Joint spectral distribution of two photons; (b) spatial distribution of the down-converted light