EFFECT OF POST-EXPOSURE HEAT TREATMENT ON CHANGES IN THE CHARACTERISTICS OF REFLECTION PHOTOPOLYMER HOLOGRAMS
D. I. Derevianko1,2, E. F. Pen2,3, S. I. Aliev1, V. V. Shelkovnikov1,3
1N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, of Siberian Branch, of Russian Academy of Sciences (SB RAS), Novosibirsk, Russia
2Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences of the SB RAS, Novosibirsk, Russia
3Novosibirsk State Technical University, Novosibirsk, Russia
Keywords: holography, photopolymer materials, reflection holograms, effective thickness of holograms, refractive index modulation
Abstract
The effect of post-exposure heat treatment on the change in the spectral and diffraction characteristics of photopolymer reflection holograms with different initial thicknesses of 8-10 μm and 20-25 μm is studied in two different cases of post-processing: immediately after completion of their recording, and after photopolymer hardening (tanning) by means of UV exposure. It is revealed that long-term heat treatment at 50 °C of unhardened holograms with a thickness of 10 μm leads to an increase in the modulation scale of the refractive index from 0.014 to 0.022. A significant shift of the spectral response to the short-wave region and expansion of its contour are established for untanned holograms, which may be due to photopolymer shrinkage and distortion of the spatial structure of the holographic grating. After the tanning procedure, heat treatment does not induce any significant changes in the spectral and diffraction characteristics of holograms, regardless of their thickness. Heating/cooling of 25-μm thick holograms, mainly at 50-5°C, leads to a bathochromic/hypsochromic stage of the spectral response of the hologram, controlled in real time, while there are no such spectral shifts for a hologram with a thickness of 8 μm, which creates prerequisites for the formation of athermolyzed holographic optical elements insensitive to temperature changes.
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