Influence of optical parameters of a crystal on the precision of brightness determination by a quantum photometer

An analysis is made of the effects of reflection and absorption of radiation in an optical parametric converter used to measure the absolute spectral density of the energy brightness with a quantum photometer. A universal method is proposed for calculating a correction factor which eliminates systematic errors that can appear when the brightness is measured by parametric conversion in a crystal where the signal, measured, or pump waves experience absorption and reflection. Expressions for the correction factor are obtained for converters of different geometry. These expressions give the factor in terms of the absorption and reflection coefficients of the faces of a crystal for all the waves participating in the parametric interaction process.