Spontaneous parameter down-conversion is exploited as a tool for absolute quantum efficiency calibration of photon detectors working in the photon-counting regime. This paper innovatively proposes a quantum efficiency correction model by analyzing the effects of after-pulse, double channel bandwidth matching and other factors on double channel coincidence counting. This experimental system shows the minimum deviation of quantum efficiency is 0.17% and detector quantum efficiency calibration accuracy better than 1.23%. The development of this new radiation calibration technology will play an important role in the future space radiation reference source and high-precision satellite radiation calibration, quantum communication and low-light level fields, environmental monitoring and climate research programs.
The “quantum” system of optical radiation metrology based on spontaneous parametric down-conversion (SPDC) correlated photon sources and coincidence measurement technology has important applications in the field of extremely weak optical radiation detection. To acquire widely tunable entangled photon sources, 532 nm continuous laser was used to pump periodically poled LiNbO3 (PPLN) crystal. And 676 nm~2500 nm correlated photons were got by switching the crystal period and tuning the temperature. Firstly, the parameters such as polarization period, length and temperature control precision of PPLN crystal were made a theoretical study. Thus, the polarization period of PPLN crystals, the bandwidth distribution curve of the signal light in different wavelength, and temperature control precision curve of the different wavelength of signal light are further calculated. The results show that, the 676 nm~2500 nm correlated photon can be got by using 9 PPLN crystals in the temperature range of 50°C~200°C. The bandwidth of the signal light has negative correlation with the crystal length; The temperature control precision of PPLN crystals was from 3.96°C to 7.64°C, and the temperature control precision requires more higher with the increase of signal light wavelength. The research results will lay a foundation for the design of high-throughput wide-spectrum tunable entangled photon sources.
Based on spontaneous parametric downconversion process, we propose a novel self-calibration radiometer scheme which can self-calibrate the degradation of its own response and ultimately monitor the fluctuation of a target radiation. Monitor results were independent of its degradation and not linked to the primary standard detector scale. The principle and feasibility of the proposed scheme were verified by observing bromine–tungsten lamp. A relative standard deviation of 0.39 % was obtained for stable bromine–tungsten lamp. Results show that the proposed scheme is advanced of its principle. The proposed scheme could make a significant breakthrough in the self-calibration issue on the space platform.
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