Research On Absolute Radiance Measurement Based On Correlation Photons Calibration

Nonlinear optical crystal was pumped by the laser to generative a spontaneous parametric down-conversion effect,producing pairs of correlation photons in terms of temporal,wavelength and direction.The absolute quantum efficiency calibration based on the correlation photons was a novel method with a high-precision absolute radiation calibration at the single photon level.In this method,the absolute quantum efficiency of single photon detector was measured by the correlation photons,leading a special advantage without considering external radiation standard.Such method has an important potential application in the fields of optical radiation measurement,space remote sensing and quantum information.This thesis summarizes the technical advantages of the correlation photons calibration and introduces the related work.The absolute radiance measurement scheme based on the correlation photons calibration is proposed.The design scheme of key modules such as photon generation,pumping light cut-off and compliance detection is demonstrated,and an absolute radiance measurement device is constructed.The measuring device has two working modes,the self-calibration mode obtains the detection efficiency of the device based on the correlation photon calibration while the observation mode measures the photon counting rate by the target light source and obtains the absolute radiance of the target light source,according to the absolute radiance measurement equation.In order to improve the calibration accuracy,this thesis investigates the performance of the correlation photon light source,single photon detector and coincidence measurement.We build a spectral distribution test device for the correlation photons and measure the emission angle and photon rate distribution of the correlation photons from 460 nm to 1000 nm.The temporal correlation of correlation photons from 580 nm to 910 um is confirmed by the monochromator spectrometer and coincidence measurement,providing an experimental verification for the wide spectral calibration.The technical parameters that affect the accuracy of measurement,such as single photon detector deadtime,afterpulse and dark count,are performed.The relationship between the parameters(e.g.deadtime and afterpulse)and the accuracy of correlation photons calibration are also analyzed.In order to test the correction factors of time digital conversion and time amplitude conversion,the measurement of channel detection efficiency at the photon counting rate from 105 s-1 to 106 s-1 are compared.The relative standard deviation of the detection efficiency measurement at the 106 s-1 count rate reduces from 1.39%to 0.13%by considering two methods,improving the reliability of the correlation photon calibration.This thesis carries out the measurement experiment of absolute radiance based on the laser import integral ball forming a uniform monochrome light source.Firstly,the absolute radiance measurement equation is derived and the parameters of the channel detection efficiency,photon counting rate and stereo angle in the absolute radiance measurement equation are measured.Later,the spectral bandwidth,linear and polarization characteristics are evaluated in both of self-calibration mode and observation mode.The uncertainty of absolute radiance measurement for the target light source is 1.8%.By inserting optical attenuators and changing photon detectors to simulate the degradation of the system,the results show that the relative standard deviation of the absolute radiance measurements during the two modes is 0.38%once the photoelectric decay of the measuring device reaches 70%,proving that the correlation photons calibration can correct the system's own decay.A comparative experiment between the reference standard radiometer traceable to cryogenic radiometer and the device based on the correlation photons calibration was carried out to measure the absolute radiance value of the target light source.The relative deviation of the absolute radiance measurement results under the two calibration systems is less than 0.7%,while the normalized deviation En is less than 1.The absolute radiance measurement based on the correlation photon calibration can achieve the same uncertainty as the current highest measurement standard,which provides direct experimental research support for the further development and application of this new calibration technology.