Design And Test Of Visible To Near-infrared Self-calibration Radiation Calibration Optical Source

Compared with the traditional calibration methods,the radiometric calibration light source based on spontaneous parametric down-conversion(SPDC)has its own absolute and accurate reproduction in any time and space,and the observation results are independent of the decay of remote sensor,which can avoid the accumulation of transfer error and realize absolute calibration.Therefore,in accordance with the requirement that the solar absolute irradiance spectroradiometer can achieve system-level responsiveness calibration of the solar observation channel,the research and design work of the core module of the solar absolute spectral irradiance spectrometer in the calibration mode,namely the relevant photonic radiation calibration light source,is carried out in this paper.Firstly,the composition and function of the solar absolute irradiance spectroradiometer are introduced.Secondly,based on the working band of the solar absolute irradiance spectroradiometer and the design requirements of the optical path,the technical indexes to be satisfied by the correlated photonic radiation calibration light source are clearly put forward.In addition,the match angle,spectral distribution of the self-radiating calibration source,divergence angle and correlated photons number rate of I type BBO crystal pumped by the laser at 266 nm wavelength are mainly calculated,these calculations provide a theoretical basis for the development of correlated photonic emission calibration light sources in visible to near-infrared bands,including complete equipment and functional testing.In order to meet the integration requirements of the radiant calibration light source module,the reasonable layout and structural design of each component are carried out.The fixed support structure of the component is adjustable and easy to assemble and debug.The finite element method is used to compare and analyze the resistance of structures using different materials to the thermal coupling condition.The results show that temperature will affect the surface precision of optical elements,and changing materials can improve the resistance of structures to the thermal coupling condition,it provides reference and optimization direction for structure material selection and working temperature control in the next field test.According to the overall structure layout and installation method,the reference axis path is established by using the internal focusing telescope.The lens,diaphragm,laser and crystal components are finely adjusted according to the unified reference axis,and the installation results are given.According to SPDC principle,correlated photons are generated in pairs.After completing the complete set and adjustment of the correlated photons calibration light source,correlated photons rings at the band range of 360 nm-725 nm are photographed and observed by CMOS camera,indicating the existence of relevant photons at the band range of 420 nm-1018.7 nm,which meets the spectral band requirements of the correlated photons calibration light source.The divergence Angle of correlated photons captured by CMOS camera is calculated,and the results show that the divergence Angle of 380 nm-610 nm band is less than ±7.5°,which meets the technical indexes of correlated photons emission calibration light source.The photomultiplier tube is used to measure the correlated photons number of the whole ring at the band of 415 nm-725 nm,and the correlated photons number rate is calculated.The experimental and theoretical values are fitted linearly,and the results show that the correlation coefficient of the curve trend of the two is 98.87%,which is highly correlated.The analysis results verify the installation effect and function realization of the correlated photonic radiation calibration light source,providing guidance for the subsequent complete system construction of the solar absolute irradiance spectroradiometer.