Search Results (5)

The similarity between object and image of negative asymmetrical holographic lenses (HLs) stored in a low-toxicity photopolymer has been evaluated theoretically and experimentally. Asymmetrical experimental setups with negative focal lengths have been used to obtain HLs. For this purpose, the resolution of the HLs was calculated using the convolution theorem. A USAF 1951 test was used as an object and the impulse responses of the HLs, which in this case was the amplitude spread function (ASF), were obtained with two different methods: using a CCD sensor and a Hartmann Shack (HS) wavefront sensor. For a negative asymmetrically recorded HL a maximum resolution of 11.31 lp/mm was obtained. It was evaluated at 473 nm wavelength. A theoretical study of object-image similarity had carried out using the MSE (mean squared error) metric to evaluate the experimental results obtained quantitatively. Full article

Holographic photopolymers are subject to extensive studies in recent years because they are low-cost, easy-to-handle, self-processing materials, which have a number of advantages over more traditional holographic materials. The development of low-toxicity photopolymers that are environmentally friendly is highly desirable. The availability of low-toxicity photopolymers will permit the mass production of commercial holograms without harm to the environment. This paper reviews recent developments in low-toxicity water-soluble holographic photopolymers. A novel composition for a water-soluble, low-toxicity photopolymer is described. This new holographic photopolymer has 90% diffraction efficiency in the transmission mode of recording and 50% diffraction efficiency in the reflection mode of recording. This photopolymer has all the necessary holographic characteristics to make it very attractive for commercialisation. The optimised chemical composition of the holographic photopolymer for the production of pressure sensors is addressed. A novel and unique feature of this new material is its high sensitivity to pressure, which can be controlled by changing its composition. Several promising environmentally friendly optical materials are being developed for future holographic applications. The presented review of low-toxicity, water-soluble, holographic photopolymers is the first of its kind. Thus, the importance of the review is twofold—it helps contribute to the development of low-toxicity holographic photopolymers, and it provides insight and new ideas for the development of water-soluble photopolymers for other applications. Full article

Aberrations and the image quality of holographic lenses were evaluated by a Hartmann–Shack (HS) wavefront sensor. Two lenses, one recorded with a symmetrical configuration and the other with an asymmetrical one, were stored in a photopolymer called Biophotopol. Each was reconstructed with two different wavelengths, 473 nm and 633 nm. Different metrics were applied to determine and quantify the aberration of the lenses (Zernike coefficients, Seidel coefficients, Marechal tolerances, root-mean-square (RMS), peak to valley, critical fraction of the pupil), and the quality of the image they provided (Strehl ratio, entropy, cutoff frequency, modulation transfer function (MTF), and area under the MTF). Good agreement between the metrics related to optical quality was obtained. The negative asymmetric holographic lenses had less aberration than the positive symmetric ones. Full article

The storage of volume holographic reflection gratings in low-toxicity photopolymers represents a challenge at present since they can be used in many important applications such as biosensors and holographic optical elements. In this context, an acrylate-based photopolymer developed in our research group was employed to study the recording of unslanted holographic reflection gratings at high spatial frequencies. The optimal preparation conditions of the photopolymer layers were determinated. The diffraction efficiencies are measured in both recording and curing stage and a comparative study of these values was realized. In addition, a theoretical study using Kogelnik’s coupled wave theory was carried out with the aim of understanding the diffraction efficiency behaviour of both processes. In this work, a maximum diffraction efficiency of 14.1% was reached after a curing process in 150 µm layers at a recording wavelength of 488 nm. This value represents a good result compared to that reported in the literature and opens the way to reflection mode holography research using low-toxicity material. Full article

Photopolymers have proved to be useful for different holographic applications such as holographic data storage or holographic optical elements. However, most photopolymers have certain undesirable features, such as the toxicity of some of their components or their low environmental compatibility. For this reason, the Holography and Optical Processing Group at the University of Alicante developed a new dry photopolymer with low toxicity and high thickness called biophotopol, which is very adequate for holographic data storage applications. In this paper we describe our recent studies on biophotopol and the main characteristics of this material. Full article