Analyses on physical mechanism of holographic recording in phenanthrenequinone-doped poly(methyl methacrylate) hybrid materials

Abstract

The photoproducts in phenanthrenequinone (PQ)-dissolved methyl methacrylate (MMA) liquid samples and PQ-doped poly(methyl methacrylate) (PQ/PMMA) solid photopolymer samples have been analyzed by various chemical measurements. A mechanism for holographic recording in our PQ/PMMA photopolymer is proposed. By UV-VIS transmission and photoluminescence spectral measurements, we find that under light exposure the molecular structure of PQ is transformed to be less conjugated. The measured results of mass spectra, Fourier transform infrared spectra, NMR spectra, and gel permeation chromatograph analyses provide some evidence for recognizing the molecular structure of the photoproducts in our PQ/PMMA photopolymers. The results show that under light exposure the PQ and MMA form new molecules, mainly an adduct of one PQ molecule with one MMA molecule. In addition, PQ also reacts as a photoinitiator to form PMMA oligomers in our samples. The structure change of the PQ molecule induces a strong change of the refractive index in the material. It provides a mechanism to record a phase hologram in our PQ/PMMA photopolymer. Holographic recordings in the samples are demonstrated, and the dynamic range of the sample is investigated.

Two-wavelength holographic recording in thick phenanthrenequinone-doped poly(methyl methacrylate) photopolymer

“…A clear sinc-squared Bragg selectivity curve has been obtained. Although the diffraction efficiency is not optimized yet or as high as that of a hologram recorded by single green wavelength, [7][8][9] these results indicate our PQ/PMMA material to be attractive for volume holographic applications with capabilities of two-wavelength recording.…”

“…6 Recently, thick phenanthrenequinone-doped poly(methyl methacrylate) (PQ/PMMA) photopolymer materials have attracted intense research interest because this material possesses not only high optical quality but also negligible light-induced shrinkage. [7][8][9] In this paper, we experimentally demonstrate the possibility of performing two-wavelength holographic recording in 2 mm thick PQ/PMMA. It may be able to open a new window for photopolymer on different applications of optical information, such as data storage, communication, and holographic imaging.…”

“…The UV-VIS spectrum of the prepared sample (as shown in Ref. 7) indicates two characteristic absorption peaks of the PQ molecules in the spectral range shorter than 450 nm. The sample is almost transparent as the wavelength is longer than 540 nm.…”

“…7 We dissolved 0.7 wt% of photosensitive dye, PQ and 1 wt% of thermal initiator, azobisisobutyronitrile molecules into the liquid monomer, MMA. The solution was stirred at 30°C for 24 h, until it became viscid.…”

Two-wavelength holographic recording in photopolymer using four-energy-level system: experiments and modeling

“…In such PQ/PMMA, the main mechanism for holographic recording is the refractive index change induced by photochemical attachment between one PQ radical and one residual MMA under light illumination. 24 The diffusions of PQ and MMA molecules in polymer matrix can be ignored.…”