The Theory Analysis And Experiment Research For Spectra Radiation Character Based On Spontaneous Parametric Down-conversion

To increase the repeatability and accuracy of the benchmarks and decrease the accumulated error caused by the transfer chain of standard equipment, over the past few decades, the trend of metrology has stretched to physical effect rather than standard equipment. In the field of radiation, the focus lies in the correlated photon which is generated by spontaneous parametric down-conversion (SPDC) to establish the absolute benchmark. In recent 30 years, the worldwide researches have proved that this new technology was of advantages and feasibility. Compared with the traditional calibration approaches which were based on radiometric source and detectors, this novel calibration method by means of SPDC is repeatable and dependent from detector or transfer chain. Therefore, as a leading branch in the international metrology science, this new means makes it possible to achieve a radiation calibration process with a higher accuracy and without transfer chain.In this paper, firstly, the SPDC technology was investigated and discussed. The technical barriers were illustrated and then the essentiality of this new technology was proposed. Then, to expand the calibration spectrum based on SPDC, we built the theoretical model of spectrum and photon count rate distribution of SPDC correlated photon through the generation mechanism and phase matching theory. By means of this model, the nonlinear crystal was designed which could be used to generate the correlated photon in successive spectrum. At last, an experiment system was established to measure the spectrum, photon count rate and time-correlation of the output correlated photon in broad band.B-BaB2O4 (BBO) crystal was bumped by 355nm semiconductorlaser to generate type-I SPDC, which was then applied in the experiment for radiation characteristics of correlated photon within 450nm-1000nm. In the research, the spectrum distribution of correlated photon detected by single-photon detector, as well as the photon count rate measurement experiment of which the signal noise ratio (SNR) was 417:1. The results proved that the spectrum shared the successive and wide wavelength characters. The experiment results were highly consistent with the theoretical ones. In the mean time, we deployed experimental equipment to measure the time-correlation characteristics, during which "three coincidence-peaks" was observed and the minimum correlation time was 0.32ns. Thus it could be concluded that spectrum was time-correlation.High precise, broad band and charge-coupled device calibration technology is already the development direction of correlated photon calibration technique. In this paper, the different sources of uncertainty were analyzed and the evaluation of each was introduced. With regard to the future research, a type-Ⅱ SPDC effect was proposed to increase the generation efficiency of correlated photon, which may be helpful to improve the SNR of radiation source based on correlated photon.