Accounting for the imperfection of the spectrophotometric complex optical elements when measuring transmission spectra of gyrotropic uniaxial crystals. I. Samples are cut perpendicular to the optical axis

A theoretical and experimental study of the effect of imperfections of the polarizer, analyzer and photomultiplier tube (PMT) on the measurement results of spectral transmission dependences of catangasite crystals Ca3TaGa3Si2O14 cut perpendicular to the optical axis has been carried out. There is a difference between the spectra obtained with p- and s-polarizations of incident light and the jumps on the curves at λ = 1050 nm. This is due to the imperfection of the PMT and the optical activity of the crystal. The estimation of the parameters of the PMT from experimental data depending on the wavelength is carried out. The influence of the imperfection of the PMT and polarizers on the results of calculating the rotation of the plane of polarization of light ρ is studied. It is shown that transmission spectra measured at angles between the polarizer and the analyzer ±45° are necessary for accurate calculation of the value of ρ. The measurement errors obtained depend on the change of optical elements in a particular device.