Pectral and diffraction properties of holographic photopolymer materials with photoinitiating systems based on a charge transfer complex and a coinitiator-dye

Photoinitiating systems (PIS) have been developed based on a light-sensitive charge transfer complex (CTC), butyltris(4-anisyl)borate diethyl-9-oxo-10-(4-heptyloxyphenyl)-9H-thioxanthenonium, and a coinitiator dye, Methylene Blue (MB) with butyltris(4-anisyl)borate tetrabutylammonium. Spectral properties and sensitivity of photopolymer materials based on individual and combined PIS (CTC, MB, CTC-MB) in the holographic recording mode have been studied. It has been shown that PIS-MB and PIS-CTC have sensitivity in a wide spectral range (400–700 nm). Using laser radiation with wavelengths $\lambda_1$ = 457 nm, $\lambda_2$ = 532 nm and $\lambda_3$ = 639 nm, monochrome and color reflection holograms with high diffraction efficiency (50–90%) were formed. Prevention of oxygen inhibition of radical polymerization in 30 $\mu$m thick layers of photopolymer materials was experimentally confirmed using butyltris(4-anisyl)borate tetrabutylammonium as a donor component in CTC and as a co-initiator in MB. Modulation of the refractive index during hologram recording, both with and without a protective film preventing oxygen access, was $\Delta n\approx$ 0.008.