Recording of multiple holograms in photopolymer films (original) (raw)

Exposure schedule for multiplexing holograms in photopolymer films

Optical Engineering

An iterative method is introduced for determining the exposure schedule for multiplexing holograms in saturable recording materials, such as photopolymers. This method is designed to share all or part of the available dynamic range of the recording material among the holograms to be multiplexed. Using exposure schedules derived from this method, the authors find that the diffraction efficiency of DuPont's HRF-150 38-and 100-m photopolymer scale is (2.2/M) 2 and (6.5/M) 2 respectively, where M is the number of holograms recorded. Finally, 1000 holograms were multiplexed at a single location in the 100-m thick photopolymer using an exposure schedule derived with this method.

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.

Improved maximum uniformity and capacity of multiple holograms recorded in absorbent photopolymers

Optics Express, 2007

In order to use photopolymers in the recording of holographic memories, high physical thickness is required. This generates many problems associated with the attenuation of light in the recording due to Beer's law. One of the more significant disadvantages is the fact that there are differences between the physical thickness of the material and the optical thickness of the holograms recorded. The optical thickness characterizes the angular selectivity of the holograms and determines the separation between two consecutive holograms in angular peristrophic multiplexing. In this work we propose a new method to record many holograms multiplexed with similar diffraction efficiency values taking into account the different effective optical thickness of each hologram.

Experimental study of multiplexed holographic gratings recorded in a photopolymerizable silica glass

Applied Physics B-lasers and Optics, 2006

Recently the capability of photopolymerizable sol–gel materials to angular multiplex holographic gratings has been demonstrated [1, 2]. In this study, holographic transmission gratings were recorded using angular multiplexing in a silica glass doped photopolymer holographic recording material. The time interval between exposures and the angular selectivity were analyzed, in particular their effects on the dynamic range. By using the optimal parameters gratings of similar response were achieved with values of M/#=4.8, as well as good values of diffraction efficiency with high photosensitivity.

Analysis of multiplexed holograms stored in a thick PVA/AA photopolymer

Optics Communications, 2008

Multiplexing many holograms in photopolymers over 500 lm thick poses many problems associated with Beer's law. In fact, the commercial holographic films (Aprilis and Inphase for example) are around 300 lm thick. For this range of thickness of absorbent photopolymeric materials, the gratings are recorded using all the thickness of the layer. Since the optical thicknesses of the multiplexed gratings are similar, it is easy to obtain an optimized time schedule to maximize the capacity of the material. For large thicknesses, the different effective optical thickness of each hologram requires an accurate prediction of each effective optical thickness in order to determine the minimum separation necessary between two consecutive multiplexed holograms. In this study, we have checked the experimental utility of the schedule model presented in a previous study to predict the multiplexing process of many gratings in a PVA/acrylamide photopolymer.

Recording multiple holographic gratings in silver-doped photopolymer using peristrophic multiplexing

Pramana, 2010

Plane-wave transmission gratings were stored in the same location of silverdoped photopolymer film using peristrophic multiplexing techniques. Constant and variable exposure scheduling methods were adopted for storing gratings in the film using He-Ne laser (632.8 nm). The role of recording geometry on the dynamic range of the material was studied by comparing the results obtained from both techniques. Peristrophic multiplexing with rotation of the film in a plane normal to the bisector of the incident beams resulted in better homogenization of diffraction efficiencies and larger M /# value.

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.

Reflection holograms stored in an environment-friendly photopolymer

Holography: Advances and Modern Trends VI, 2019

The recording of volume holographic reflection gratings in eco-friendly photopolymers represents a challenge at present since they can be used in many important applications such as holographic optical elements and biosensors. In this sense, the aim of this work has been fabricated reflection gratings in the symmetrical experimental in "Biophotopol" and to study the dependence of diffraction efficiency on physical thickness, recording intensity and exposure energy. An increase in diffraction efficiency was observed when the photopolymer films were cured with a LED lamp to improve the stability of the reflection holograms. The maximums diffraction efficiencies around 30 % were obtained for reflection gratings with a spatial frequency of 4888 lines/mm. The index modulation and optical thickness were obtained by fitting procedure through Kogelnik's coupled wave theory. Experimental and theoretical results have been interpreted to modify the photopolymer formulation and exposure conditions in order to increase the diffraction efficiencies.

Hologram multiplexing in a highly photosensitive photopolymerizable material in a sol-gel matrix

Applied Physics B-lasers and Optics, 2005

In this paper, we present a photopolymerizable material in a sol-gel matrix suitable for recording a large number of multiplexed diffraction gratings with low total exposure energy. The matrix of this material is an inorganic porous silica glass, a material that does not shrink when radical photopolymerization is initiated. The photosensitive component is based on acrylamide, N,N′-methylenebisacrylamide, triethanolamine and yellow eosine as a photoinitiator. In the reported study, 50 holograms were angularly multiplexed with diffraction efficiencies between 0.1 and 1.9% resulting in a dynamic range of M/# = 3.9. The total exposure was 4.5 mJ/cm2 and the energy used in recording each hologram was 95 μJ/cm2. This indicates a very high sensitivity for this material in the range of 3.3 to 15.5 cm/mJ. Due to this good holographic performance, the material is suitable for holographic data storage applications.