G. Aswathy

Bio: G. Aswathy is an academic researcher from Cochin University of Science and Technology. The author has contributed to research in topics: Diffraction efficiency & 3D optical data storage. The author has an hindex of 3, co-authored 4 publications receiving 21 citations.

Multiplexing recording in nickel-ion-doped photopolymer material for holographic data storage applications.

Abstract: In the present study, a series of holographic gratings were recorded in a single location of nickel-ion-doped photopolymer film using different methods of multiplexing. The uniformity of their diffraction efficiency was shown to improve by using an exposure time scheduling method for holographic recording. Thirty-five gratings were recorded in the 130 μm thick photopolymer material with M#=6.18 and an average diffraction efficiency of 3.24% using peristrophic multiplexing. In the next step, a combination of peristrophic and angular multiplexing was used for storing 50 gratings in the material with a dynamic range of 7 and a mean diffraction efficiency of 2.15%.

Stretching the sensitivity and stability of an acrylamide based photopolymer material with mixture of dyes

Abstract: The limited absorption range of photopolymers in the visible region was always a matter of concern due to their wide-spread application in the field of holography. The present work has investigated the possibility of extending the limited absorption range towards the entire visible range by simple modifications in the photopolymer composition so that panchromaticity can be invoked in the material. Here modification was done on already developed photopolymer material by adding another photosensitizer. Studies showed that holographic performance was improved to a great extent. It was possible to record gratings with blue, green and red wavelengths in 130 µm thick films with more than 80% diffraction efficiency (DE) creating a refractive index modulation of ∼1.7 × 10−3 at exposure energy of 50 mJ/cm2. This material will be a good candidate for data storage and color holographic applications. One of the remarkable findings was that the storage and shelf life of the material could be extended compared to other photopolymer materials. This material could be used to write gratings with 70% DE even after 12 months of storage. Thus, addition of a second photosensitizer not only extended the absorption range, but also the shelf life of the photopolymer.

Improving the polarization-holography performance of PQ/PMMA photopolymer by doping with THMFA.

Abstract: Increasing photosensitizer concentration has been considered as an effective approach to improve the performance of holographic material. In this paper, we report on new method for increasing the saturated dissolvability of photosensitizer PQ within polymeric media by introducing copolymerization monomer into the PQ/PMMA. The photosensitizer concentration of PQ was increased from 0.7wt% to 1.3wt%, compared with the typical PQ/PMMA sample. Besides, we investigated performance of polarization holographic recordings in typical PQ/PMMA and copolymerization monomer-containing PQ/PMMA with the orthogonally polarized signal and reference waves. And the doping of THFMA component resulted in a significant improvement of diffraction intensity and photosensitivity. In addition, high-quality holographic image reconstruction was realized in our home-made material.

Application of Photopolymer Materials in Holographic Technologies.

Abstract: The possibility of the application of acrylate compositions and Bayfol HX photopolymers in holographic technologies is considered. The holographic characteristics of materials, their advantages, and limitations in relation to the tasks of obtaining holographic elements based on periodic structures are given. The conditions for obtaining controlled two and multichannel diffraction beam splitters are determined with advantages in terms of the simplicity of the fabrication process. The diffraction and selective properties of volume and hybrid periodic structures by radiation incidence in a wide range of angles in three-dimensional space are investigated, and new properties are identified that are of interest for the development of elements of holographic solar concentrators with advantages in the material used and the range of incidence angles. A new application of polymer materials in a new method of holographic 3D printing for polymer objects with arbitrary shape fabrication based on the projection of a holographic image of the object into the volume of photopolymerizable material is proposed, the advantage of which, relative to additive 3D printing technologies, is the elimination of the sequential synthesis of a three-dimensional object. The factors determining the requirements for the material, fabrication conditions, and properties of three-dimensional objects are identified and investigated.

Holographic Characteristics of Photopolymers Containing Different Mixtures of Nematic Liquid Crystals.

Abstract: A holographic polymer dispersed liquid crystal (HPDLC) is used to record holographic diffraction gratings. Several mixtures of nematic liquid crystals (LC) are used as components of the HPDLC to evaluate their influence in static and dynamic basic properties. The diffraction efficiency obtained in the reconstruction of the holograms is evaluated to compare the influence of the different LC. Additionally, the samples are exposed to a variable electric field and the diffracted light intensity as a function of the applied voltage is measured to evaluate the influence of the LC. The results obtained show significant differences depending on the LC incorporated to the photopolymer.