Wavelength calibration of a solar spectral irradiance radiometer and validation by correlation photon coincidence counting

Accurate wavelength calibration is the key to achieving accuracy observation of solar spectral irradiance. A wavelength calibration of solar spectral irradiance radiometer based on correlation photon radiation reference is proposed. The wavelengths of two channels of the solar spectral irradiance radiometer are calibrated by a Hg-Ar lamp and lasers. A collimating and focusing optics are designed to ensure that light can illuminate the slit vertically and without polarization. The optics can also keep the consistency of observing and self-calibration modes. The calibration equations of two channels are established. The wavelength deviations of two channels are-0.11 -0.07 nm and-0.085 -0.017 nm respectively. To validate the calibrated wavelength, channel 1 is selected as the inspection channel according to the spectral line number of the calibration lamp and the variation of the photon count rate. The motor position close to the calibration wavelength 763.511 nm is selected in channel 2, and the coincidence measurement is carried out to check the accuracy of wavelength calibration in channel 1. The deviation of wavelength around 408 nm is 1.139 nm. The experimental results show that the correlated photons self-calibration system can realize the calibration and validation of the system wavelength. The method can increase the number of calibration wavelengths and is suitable for both channels.