A flat spectral photon flux source for single photon detector quantum efficiency calibration

A flat spectral photon flux source is proposed to facilitate the single photon detector quantum efficiency calibration in an extended wavelength range (400-800nm). The absolute quantum efficiency at certain wavelengths (e.g. 633nm and 807nm) of the photon counter under test can be measured via correlated photons method and used to evaluate the photon statistics of the flat spectral photon flux source. A correction factor derived from the photon statistics can then be applied throughout the wavelength range for improved detector quantum efficiency measurement.