Effect of micro-range transmission on the imaging sharpness of near-infrared upconversion thin-film silicon-based detectors

Near-infrared photons are converted to visible photons by nonlinear crystal upconversion materials and detected directly by silicon-based detectors, which is an attractive method for near-infrared detection. In this study, the influence of the film thickness of the upconversion material on the imaging sharpness based on the Van Cittert–Zernike theorem is analyzed. The relationship between imaging sharpness of silicon-based detectors and different thicknesses of near-infrared upconversion films is obtained by experimental measurements. The results show that the crystal luminescence area As of the microstructure unit of the upconversion material and the wavelength λ¯ of the converted visible light center remain unchanged with the change of thickness. The crosstalk distance a of the imaging sharpness is proportional to the thickness z of the upconversion material film, which is consistent with the theoretical results.