Thickness variation of self-processing acrylamide-based photopolymer and reflection holography (original) (raw)
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Holographic recording in acrylamide photopolymers: thickness limitations
Applied Optics, 2009
Holographic recording in thick photopolymer layers is important for application in holographic data storage, volume holographic filters and correlators. Here, the characteristics of acrylamidebased photopolymer layers having thickness from 250 µm to 1-mm were studied. For each layer thickness samples with three different values of absorbance were studied. By measuring both the first order diffraction efficiency growth of holographically recorded gratings and studying the diffraction patterns obtained, the influence of scattering on the diffraction efficiency of thick volume holographic gratings was analyzed. It was observed that above a particular thickness and absorbance, the first order diffraction efficiency significantly decreased because of increased holographic scattering. From the first order diffraction efficiency dependence on the samples absorbance and thickness it is possible to choose photopolymer layer properties that are suitable for a particular holographic application. This study was carried out in order to determine the highest layer thickness that could be used in phase code multiplexed holographic data storage system utilizing thick photopolymer layers as a recording medium.
Development of a Panchromatic Acrylamide Based Photopolymer for Multicolour Reflection Holography
Applied Optics, 2010
The development of a panchromatic acrylamide based photopolymer (ABP) for holographic recording application is presented. The scattering of the recording medium was characterised by measuring the Bidirectional Scattering Distribution Function (BSDF). The dynamic range in reflection mode of recording was evaluated by measuring the diffraction efficiencies of the holographic gratings recorded individually at 633nm, 532nm, and 473nm wavelengths at spatial
Development of a panchromatic acrylamide-based photopolymer for multicolor reflection holography
Applied Optics, 2010
The development of a panchromatic acrylamide based photopolymer (ABP) for holographic recording application is presented. The scattering of the recording medium was characterised by measuring the Bidirectional Scattering Distribution Function (BSDF). The dynamic range in reflection mode of recording was evaluated by measuring the diffraction efficiencies of the holographic gratings recorded individually at 633nm, 532nm, and 473nm wavelengths at spatial frequencies of 4200 l/mm, 5000 l/mm and 5700 l/mm respectively. Spectral characterisation of the reflection gratings recorded using a combined single RGB beam was carried out and the reconstructed wavelengths were monitored and compared with the recording wavelengths. The recorded and the reconstructed wavelengths were plotted as points on the CIE chromaticity diagram in order to reveal the shifts due to material shrinkage in the corresponding RGB wavelengths. Finally reflection holograms of an object were successfully recorded at all the three primary wavelengths. The results represent a strong confirmation that this acrylamide based photopolymer can be used as a panchromatic recording material and can be employed in future commercial holographic applications.
Effect of film thickness on the performance of photopolymers as holographic recording materials
Applied …, 2000
An important issue in developing applications for photopolymers in holography is the effect of film thickness on recording properties. Now it is possible to create these samples with a much wider range of thickness ͑d ϭ 20 -1400 m͒ than was previously available. We exploit these recent advances in photopolymer processing to systematically evaluate how the dynamic range of a photopolymer depends on its thickness. The results illustrate that sample performance increases linearly with thickness as predicted by standard models of volume holography. However, above a critical thickness sample performance degrades, and the angular response of recorded plane-wave holograms shows evidence of grating curvature. These distortions are likely the result of photopolymer shrinkage, which in thicker samples occurs in a nonuniform fashion. This problem limits the performance of these photopolymers and is likely to be an issue for any photopolymer that undergoes comparable polymerization shrinkage.
Multiplexing holograms in an acrylamide photopolymer
Proceedings of Spie the International Society For Optical Engineering, 2006
A peristrophic multiplexing method is used to store various diffraction gratings at the same spot in the material. This material is formed of acrylamide photopolymers which are considered interesting materials for recording holographic memories. They have high diffraction efficiency (ratio between diffracted and incident beams), high energetic sensitivity and optical quality, and developing processes are not necessary. In this work, the photopolymer is composed of acrylamide (AA) as the polymerizable monomer, triethanolamine (TEA) as radical generator, N,N'methylene-bis-acrylamide (BMA) as crosslinker, yellowish eosin (YE) as sensitizer and a binder of polyvinyl alcohol (PVA). The layers of material obtained are approximately 1 mm thick. Using holographic recording schedules, the exposure energy each hologram should receive in order to achieve uniform diffraction efficiency is optimized. The purpose of these recording schedules is to enable full advantage to be taken of the whole dynamic range of the material and to share it between the individual holograms. The Scheduled Exposure Method (SEM) and the Incremental Exposure Method (IEM) are the two multiplexing schedules used to determine the recording times. Having determined these times, the results obtained with both methods are compared to ascertain which method enables the greatest number of holograms to be recorded with the highest, most uniform diffraction efficiencies.
Study of the shrinkage caused by holographic grating formation in acrylamide based photopolymer film
Optics Express, 2011
We study the shrinkage in acrylamide based photopolymer by measuring the Bragg detuning of transmission diffraction gratings recorded at different slant angles and at different intensities for a range of spatial frequencies. Transmission diffraction gratings of spatial frequencies 500, 1000, 1500 and 2000 lines/mm were recorded in an acrylamide based photopolymer film having 60 ± 5 μm thickness. The grating thickness and the final slant angles were obtained from the angular Bragg selectivity curve and hence the shrinkage caused by holographic recording was calculated. The shrinkage of the material was evaluated for three different recording intensities 1, 5 and 10 mW/cm 2 over a range of slant angles, while the total exposure energy was kept constant at 80 mJ/cm 2 . From the experimental results it can be seen that the shrinkage of the material is lower for recording with higher intensities and at lower spatial frequencies.
Comparison of diffuse-object holograms and holographic gratings stored on acrylamide photopolymers
Optik - International Journal for Light and Electron Optics, 2002
In this study the diffraction efficiency of diffuseobject holograms is compared with that of holographic gratings for a constant beam ratio and different intensities in order to analyzed the storage and reconstruction process with the same wavelength. When we work with the same wavelength in the register and reconstruction process, the refraction index modulation decreases. The material used is a photopolymer based on acrylamides, consisting of acrylamide as monomer, yellowish eosin as sensitizer and triethanolamine as radical generator, all on a matrix of polyvinyl alcohol.
Applied Optics, 2014
A holographic device is under development that aims to improve light collection in solar cells. The aim is to explore the potential of using photopolymer Holographic Optical Elements (HOE) to collect light from a moving source, such as the sun, and re-direct it for concentration by a holographic lens.. A working range of 45 degrees is targeted for such a device to be useful in solar applications without tracking. A photopolymer HOE is capable of efficiently re-directing light, but the angular selectivity of a single grating is usually of the order of one degree at the thicknesses required for high efficiency. The challenge here is to increase the angular and wavelength range of the gratings so that a reasonable number may be multiplexed and/or combined to provide a device that can concentrate light incident from a large range of angles. In this paper low spatial frequency holographic recording is explored in order to increase the angular and wavelength range of an individual grating. Ultimately, a combination of gratings will be used so that a broad range of angles of incidence are accepted. A design is proposed for the combination of such elements into a holographic solar collector. The first step in achieving this is optimization of recording at low spatial frequency. This requires a photopolymer material with unique properties, such as a fast monomer diffusion rate. This paper reports results on the efficiency of holograms recorded in an acrylamide based photopolymer at low spatial frequencies (100, 200 and 300 l/mm). The diffraction efficiency and angular selectivity of recorded holograms have been studied for various photopolymer layer thicknesses and different intensities of the recording beams. A diffraction efficiency of over 80% was achieved at a spatial frequency of 200 l/mm. The optimum intensity of recording at this spatial frequency was found to be 1 mW/cm 2 . Individual gratings and focusing elements with high efficiency and FWHM angles of 3 o are experimentally demonstrated.