Characterization of the holographic photopolymer Bayfol HX in the IR region

The possibility of creating holographic optical elements operating in the near infrared spectral range based on the Bayfol HX holographic photopolymer has been considered. The dynamic range of the refractive index of the photopolymer and the amplitude-phase nature of the holograms in the infrared range have been studied. The influence of recording parameters (power density of recording radiation, recording time) on the distribution of the dynamic range of the refractive index between grating harmonics has been studied. The analysis of the amplitude-phase nature of holograms was carried out by measuring the transmission spectra of the studied photopolymer after the photopolymerization reaction. The dynamic range of the refractive index of a photopolymer evaluated in the spectral range from 405 nm to 2099 nm. For this purpose, the angular selectivity contours of holograms with periods from 414 nm to 2100 nm, optimized for different parts of the specified spectral range, were measured and analyzed. The influence of recording parameters on the distribution of the dynamic range of the refractive index between the grating harmonics was analyzed by calculating the amplitudes of the first and second harmonics of the refractive index modulation from the experimentally measured angular selectivity contours of holograms recorded with different recording time at a constant irradiation dose. It was shown that the dynamic range of the refractive index of the photopolymer in the near infrared spectral range, as compared with the long-wavelength part of the visible region of the spectrum, differs by a value that does not exceed the measurement accuracy. A pronounced violation of the reciprocity was demonstrated with scaling of the interference pattern or with changing of the power density of the recording radiation. The optimal recording conditions for holograms calculated for the infrared spectral range for the studied photopolymer were found. The possibility of using of the studied holographic material in telecommunication optics has been demonstrated.