Phenanthrenequinone-doped Poly Research Articles

Sensitivity-Enhancing Modified Holographic Photopolymer of PQ/PMMA

Phenanthrenequinone-doped poly(methyl methacrylate) (PQ/PMMA) photopolymers are potential holographic storage media owing to their high-density storage capacities, low costs, high stability, and negligible shrinkage in volume holographic permanent memory. However, because of the limitations of the substrate, conventional Plexiglas materials do not exhibit a good performance in terms of photosensitivity and molding. In this study, the crosslinked structure of PMMA was modified by introducing a dendrimer monomer, pentaerythritol tetraacrylate (PETA), which increases the photosensitivity of the material 2 times (from ~0.58 cm/J to ~1.18 cm/J), and the diffraction efficiency is increased 1.6 times (from ~50% to ~80%). In addition, the modified material has a superior ability to mold compared to conventional materials. Moreover, the holographic performance enhancement was evaluated in conjunction with a quantum chemical analysis. The doping of PETA resulted in an overall decrease in the energy required for the reaction system of the material, and the activation energy decreased by ~0.5 KJ/mol in the photoreaction stage.

Faithful reconstruction in orthogonal elliptical polarization holography read by different polarized waves.

A potential technology applied in optical storage, the polarization holography has attracted much attention. In polarization holography, not only the amplitude and phase but also the polarization state is applied to record the information. What is meant by faithful reconstruction is that the reconstructed wave is identical to the signal wave. In the previously reported experiments about faithful reconstruction in orthogonal polarization holography, all the reading waves are identical to the reference waves of recording stage. It may result in a misunderstanding that the reading wave being identical to the reference wave of recording stage is the prerequisite for faithful reconstruction. We designed the experiments to observe the faithful reconstruction read by different polarized waves, where two orthogonal elliptically polarized waves are applied in the recording stage and phenanthrenequinone-doped poly methyl methacrylate (PQ/PMMA) is used as the recording material. By controlling the exposure time of recording material, the faithful reconstruction may be observed when the reading wave is the linearly polarized wave and the elliptically polarized wave, where neither reading wave is the same as the reference wave. The result may be of help for us to understand the reconstructed characteristics of orthogonal polarization holography.

Prerequisite for faithful reconstruction of orthogonal elliptical polarization holography

Faithful reconstruction, which is a key phenomenon in optical data storage, is significant in polarization holography and has attracted much attention. It is defined as the reconstructed wave being identical to the signal wave. We design an experiment to observe the faithful reconstruction of elliptical polarization holography in which the two orthogonal elliptical polarization waves are applied in the recording stage. In the experiment, phenanthrenequinone-doped poly methyl methacrylate is used as the recording material, and the angle between the signal and reference waves is ∼56 deg. We control the exposure time of recording material to observe the faithful reconstruction of orthogonal elliptical polarization holography. How to obtain the faithful reconstruction is interesting work; therefore, we propose a prerequisite for faithful reconstruction. Although the prerequisite is derived from orthogonal elliptical polarization holography, it could also be applied in orthogonal linear and circular polarization holography. The result may be helpful for understanding the faithful reconstruction of orthogonal polarization holography.

Volume holographic recording in Al nanoparticles dispersed phenanthrenequinone-doped poly(methyl methacrylate) photopolymer

High-performance material plays a crucial role in holographic data storage, which is a noteworthy technology with potential applications in the field of high capacity data storage. We report on a new kind of holographic storage material based on aluminum nanoparticles (Al NPs) dispersed phenanthrenequinone-doped poly(methyl methacrylate) (PQ/PMMA) photopolymer. Al NPs are efficiently synthesized in a monomer solvent using laser ablation in liquids without chemical precursors. It is shown that an increase in diffraction efficiency and recording sensitivity is achieved in both traditional holography and polarization holography by doping with Al NPs. After 4 h of ablation, the new material exhibited an improvement in the diffraction efficiency for both traditional holography and polarization holography from 2.85% to 57.15% and from 0.6% to 4.07%, respectively. We also investigated the image recording and reconstruction performance for both traditional and polarization holography and the results indicate that the proposed material has noticeable potential as a holographic storage material. Additionally, it also possesses excellent potential for holographic position multiplexing recording. We conclude that laser ablation in a liquid is a promising option for processing low-cost nano-doped holographic storage material.

Highly concentrated phenanthrenequinone-doped poly(MMA-co-ACMO) for volume holography

Novel composite materials are synthesized by incorporating N-acryloylmorpholine (ACMO) in highly concentrated phenanthrenequinone (PQ) doped poly(methyl methacrylate) (PMMA). The photosensitizer concentration of PQ was increased from 0.7 wt. % to 1.8 wt. %. The doping of ACMO component results in a higher diffraction efficiency and photosensitivity than a typical PQ/PMMA system. The enhanced performance of the material may stem from the ACMO molecules, which might open a new route for improving the holographic performance of the PQ/PMMA photopolymer.

Enhanced diffraction efficiency of mixed volume gratings with nanorod dopants in polymeric nanocomposite

We propose a method to improve the holographic performance of a volume holographic material by the particle-shape dependence of doped nanoparticles. Previously reported methods are based on changing the doping concentration of dopants and the diameter of nanoparticles or modifying the surface of nanoparticles. When transverse surface plasmon resonance of optimized gold nanorods shifts near the recording wavelength, experiments confirmed that enhancement of diffraction efficiency by efficient dopants of gold nanorods is better than that of gold nanospheres. The enhancement effects under optimal mixing conditions occur with a crucial factor of maximum absorption intensity at the recording wavelength using the particle-shape dependence of doping nanorods. The gold nanorods with an average diameter of 10 ± 2.1 nm and an average length of 34 ± 5 nm are doped in Phenanthrenequinone-doped poly(methyl methacrylate) photopolymers. The diffraction efficiency of volume holographic grating in the photopolymer doped with nanorods is 18.5% higher than that in the photopolymer doped with nanospheres and 29.6% higher than that in the pure photopolymer.

Characteristics of volume polarization holography with linear polarization light

Volume polarization holographic recording in phenanthrenequinone-doped poly(methyl methacrylate) (PQ-PMMA) photopolymer with linear polarized light is obtained. The characteristics of the volume polarization hologram are experimentally investigated. It is found that beyond the paraxial approximation the polarization states of the holographic reconstruction light are generally different from the signal light. Based on vector wave theoretical analyses and material properties, the special exposure condition for correctly holographic reconstruction is obtained and experimentally demonstrated.

The optical polarization properties of phenanthrenequinone-doped Poly(methyl methacrylate) photopolymer materials for volume holographic storage

We present an experimental study on the optical polarization properties of the phenanthrenequinone-doped poly(methyl methacrylate) photopolymer materials. We discuss the diffraction efficiency with different weight ratios of phenanthrenequinone that was dissolved in the materials. In addition, we observe the diffraction efficiency difference between polarization holography and traditional holography.

Hybrid polarization-angle multiplexing for volume holography in gold nanoparticle-doped photopolymer.

We report on volume holographic hybrid polarization-angle multiplexing in a gold nanoparticle-doped photopolymer. When doping the gold nanoparticles, the linear photoinduced birefringence of the phenanthrenequinone-doped poly (methyl methacrylate) (PQ/PMMA) photopolymer could be increased by nearly 38%. The data pages could be recorded with the orthogonal circular polarization multiplexing, and the reconstructed images have a symbol-error rate of 3.81% and 4.46% for left circular polarization and right circular polarization state, respectively. Two biological image sets multiplexed both with the angle interval of 0.1° and with orthogonal circular polarization are reconstructed separately and simultaneously.

Volume polarization holographic recording in thick photopolymer for optical memory.

Based on a vector wave theory of volume holograms, dependence of holographic reconstruction on the polarization states of the writing and reading beams is discussed. It is found that under paraxial approximation the circular polarization holograms provide a better distinction of the reading beams. Characteristics of recording polarization holograms in thick phenanthrenequinone-doped poly(methyl methacrylate) (PQ/PMMA) photopolymer are experimentally investigated. It is found that the circular polarization holographic recording possesses better dynamic range and material sensitivity, and a uniform spatial frequency response over a wide range. The performance is comparable to that of the intensity holographic recording in PQ/PMMA. Based on theoretical analyses and the material properties, a polarization multiplexing holographic memory using circularly polarization recording configuration for increasing storage capacity has been designed and experimentally demonstrated.

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

We investigate a two-wavelength method for recording a persistent hologram in a doped photopolymer. The recording method is based on two separated optical excitations of the four-energy-level system of the doped element, one at λ=325 nm as the sensitizing wavelength and the other at λ=647 nm as the writing wavelength, allowing for an experimental demonstration of nondestructive readout in phenanthrenequinone-doped poly(methyl methacrylate). Further, a four-energy-level rate equations model is proposed for describing the dynamics of hologram recording. The model successfully explains our experimental finding and further provides a general method to investigate such a two-wavelength holographic recording in photopolymer.

Influence of fabrication conditions on characteristics of phenanthrenequinone-doped poly(methyl methacrylate) photopolymer for holographic memory

In this paper, we experimentally investigate the influence of the fabrication conditions on holographic characteristics in phenanthrenequinone-doped poly(methyl methacrylate) (PQ:PMMA) bulk photopolymer. In our investigation, the PQ:PMMA bulk samples are fabricated by use of a two-step thermo-polymerization method. We firstly propose to monitor relative viscosity of the monomer solution during the sample preparation to obtain a reliable criterion for material fabrication. We then compare experimentally characteristics of 2-mm thick samples fabricated with different conditions for holographic memory. The results show that the conditions in the first step play a important rule for fabricating bulk PQ:PMMA samples with good optical uniformity. In addition, the conditions in the second step play the rule for controlling the concentration of residual monomer and determine holographic characteristics. These results can provide a useful rule for fabricating bulk PQ:PMMA photopolymers for further applications on volume holographic data storage.

Study of PQ/PMMA photopolymer Part 2: experimental results

In Part 1 of this paper an extended 1D nonlocal photo-polymerization driven diffusion (NPDD) model was developed, giving the temporal and spatial variations of each chemical component concentration within a phenanthrenequinone-doped poly(methyl methacrylate) (PQ/PMMA) material layer. Simulations to study the predicted normalized transmission, the nonlocal effect, and the diffusion of ground and excited states of PQ are presented. In this paper, the validity of the proposed model is examined by applying it to fit experimental data for PQ/PMMA layers containing three different initial PQ concentrations; i.e., 1, 2, and 3 mol. %. The effect of different exposure intensities is also examined. Material parameter values are estimated by numerically fitting experimental normalized transmission curves and refractive index modulation growth curves using the proposed theoretical model.

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

Two-wavelength holographic recording in thick phenanthrenequinone-doped poly(methyl methacrylate) photopolymer is demonstrated. By using 325 nm laser as a gating illumination during the holographic recording with 647 nm laser, a volume hologram with diffraction efficiency of ∼ 4% can be recorded in a 2 mm thick sample. In addition, the Bragg selectivity curve with clear sinc nulls is demonstrated. These results support further applications as recording media for volume holographic device with extended spectral response and selective recording property.

Volume polarization holographic recording in thick phenanthrenequinone-doped poly(methyl methacrylate) photopolymer

Volume polarization holographic recording in phenanthrenequinone-doped poly (methyl methacrylate) photopolymer is obtained. Photoinduced birefringence in a 2 mm thick sample is measured by a phase-modulated ellipsometry. The birefringence induced in this material by linearly polarized beam at 514 nm reaches 1.2×10(-5). In addition, ability for recording volume polarization grating using two different polarization configurations is demonstrated and compared. The experimental results show that the diffraction efficiency of the hologram reaches to ∼40% by using two orthogonal circularly polarized beams.

Improvement of holographic thermal stability in phenanthrenequinone-doped poly(methyl methacrylate-co-methacrylic acid) photopolymer

Experimental studies of holographic thermal stability in phenanthrenequinone (PQ)-doped poly(methyl methacrylate-co-methacrylic acid) [P(MMA-co-MAA)] photopolymers are presented. A possibility to improve the thermal stability of holograms is demonstrated by doping methacrylic acid (MAA) into the poly(methyl methacrylate) (PMMA) polymer matrix. MAA as a copolymerization monomer can form a more stable polymer matrix with methyl methacrylate (MMA) monomer and increase average molecular weight of photoproducts, which finally depress the diffusion of photoproduct. The optimized MAA concentration copolymerized into P(MMA-co-MAA) polymer matrix can bring nearly a month's lifetime of gratings, which is obviously an improvement over the usual PQ-PMMA material under thermal treatment.

Study on the mechanism of dark enhancement in phenanthrenequinone-doped poly(methyl methacrylate) photopolymer for holographic recording

The dark enhancements with various exposure energies are studied in thick PQ/PMMA photopolymer. Considered the weak molecules diffusion of PQ component and the grating detuning, a new mechanism of dark reaction is proposed to explain the dark enhancement. Moreover, the influences of dark reaction on Bragg angular selectivity and grating recording are analyzed. The results are beneficial to the practical holography application.

Phenanthrenequinone-doped copolymers for holographic data storage

Two new types of phenanthrenequinone-doped poly(methyl-methacrylate) (PQ/PMMA) are proposed and fabricated for volume holographic recording. In these materials, the matrix of PQ/PMMA is replaced by the copolymers, which are composed of either poly(trimethylolpropane triacrylate-co-methyl methacrylate) or poly(2-phenoxyethyl acrylate-co-methyl methacrylate), respectively. With the chemical analyses of the response of these materials with respect to light exposure, the physical mechanism of the holographic recording in those copolymer samples is investigated. In addition, the holographic characteristics, including the dynamic range and sensitivity, have been measured. The experimental results demonstrate that the modification of the monomer components can enhance holographic characteristics of PQ/PMMA.

Two-dimensional higher-diffraction-order optical beam splitter based on phenanthrenequinone-doped poly(methyl methacrylate) photopolymer

A two-dimensional optical beam splitter has been realized that uses the higher diffraction orders of a refractive-index grating. Gratings were recorded experimentally with light from a semiconductor laser incident at a small angle on phenanthrenequinone-doped poly(methyl methacrylate) photopolymer. The incident signal beam, which was made up of three different wavelengths (632.8, 532.0, and 488.0 nm), was split by the grating into multiple output beams with nearly equal size and separation. Results are given for when the sample grating was placed behind, in front of, and in the focal plane of a Fourier lens. The properties of higher-order-diffraction images have been discussed. The discussion shows that a two-dimensional higher-diffraction-order optical beam splitter provides a practical method for splitting a signal beam.

Cascaded holographic polymer reflection grating filters for optical-code-division multiple-access applications

We evaluate the use of edge-illuminated holographic Bragg filters formed in phenanthrenequinone-doped poly(methyl methacrylate) for optical-code-division multiple-access (OCDMA) coding and decoding applications. Experimental cascaded Bragg filters are formed to select two different wavelengths with a fixed distance between the gratings and are directly coupled to a fiber-measurement system. The configuration and tolerances of the cascaded gratings are shown to be practical for time-wavelength OCDMA applications.