Gurusamy Manivannan

Cr(VI)- and Fe(III)-doped polymer systems as real-time holographic recording materials

Volume transmission holograms have been recorded in dichromated poly(vinyl alcohol) (DCPVA), dichromated poly(acrylic acid) (DCPAA), and ferric chloride poly(vinyl alcohol) (FePVA) films using a 488-nm light (from an argon-ion laser), and the hologram development has been monitored in real time using a 647-nm line of the krypton laser. The influence of different chemical parameters (e.g., pH and electron donor) on the holographic efficiency has been determined, and an efficiency value as high as 70% was achieved in all three recording media. Further, the possible primary photoprocesses responsible for the hologram formation are tentatively identified and discussed

New azo-dye-doped polymer systems as dynamic holographic recording media

Polymer materials show their impact on optical storage technology for developing high information density and fast access-type memories with a high read-out efficiency. New azo-dye-doped polymer materials have been developed and used for recording dynamic holograms. Dynamic holograms with reasonably high diffraction efficiency have been recorded at 468 nm, and the efficiency of the Write, Read and Erase (WRE) cycle in these azo-dye-doped polymer materials was determined. Significant observations in these materials are: (i) there is no need to change the polarization of the writing beam to erase the recorded holograms, (ii) the whole WRE cycle is very fast (3–6 s) and (iii) recording of more than 250 WRE cycles without any fatigue of the recording materials is possible.

Real-time dynamic polarization holographic recording on auto-erasable azo-dye doped PMMA storage media

Abstract Dynamic real-time holographic recording under linear cross-polarized writing beams at 488 nm was performed on two different new azo-dye doped PMMA matrices of 10±1 μ m thick. For comparison, the holographic recording has also been performed under unpolarized light ( λ = 488 nm). Maximum diffraction efficiency of 0.15%, 0.20% and 5%, corresponding respectively to the x -, i -polarized and unpolarized writing beams, has been achieved. Numerous complete Write/Read/Erase (WRE) cycles have also been performed without any apparent fatigue in the recording performance of the materials. In polarization holography, a slight memory effect could be observed in both these recording materials if the time interval between two successive exposure is relatively short (2–5 s), on attempting to place a maximum number of WRE cycles in a specific time period (7–8 complete WRE cycles in 50 s).

Holographic and spectroscopic characterization of spiropyran doped poly(methyl methacrylate) films

Abstract Photo-induced reversible color change between thermally stable and metastable states of spiropyran molecules can modulate the absorption and refractive index of spiropyran doped polymer films. Thus erasable holograms can be recorded in either stable or metastable states of the spiropyran doped polymer films. Commercially avaibable spiropyran was doped in poly(methyl methacrylate) and thick and thin polymer films were prepared by the gravity settling method. It was found that write and erase cycles can be performed repeatedly. High efficiency erasable holographic recording at either 350 nm or 647 nm was performed in the spiropyran doped poly(methyl methacrylate) films, and a maximum diffraction efficiency about 6% was achieved.

Metal-ion-doped polymer systems for real-time holographic recording

Metal ions such as Ferric [(Fe(III)] and Dichromate [Cr(IV)] have been used in conjunction with Polyvinyl alcohol for recording holograms in real time. Experiments have been performed to optimize the various parameters influencing the holographic performance of these materials. High real-time diffraction efficiency of 80% and 60% have been obtained in Ferric chloride Polyvinyl alcohol (FePVA) and Dichromated Polyvinyl alcohol (DCPVA), respectively.

Spiropyran-doped poly(vinyl carbazole): a new photopolymer recording medium for erasable holography

The photosensitive organic system of poly(vinyl carbazole) doped with spiropyran is studied for real-time reversible holography. The photoinduced reversible color change between thermally stable and metastable states of spiropyran molecules can modulate the absorption and the refractive index of the spiropyran-doped polymer film. Erasable holograms can be recorded in either stable or metastable states of such films of thickness 10 and 50 μm prepared by a gravity settling method. The grating constant achieved was δ= 0.58 μm, using the 350-nm UV line of a krypton-ion laser. It has been found that write-read-erase cycles can be performed repeatedly. High-efficiency erasable holographic recording at 350 nm has been performed in these films, and a diffraction efficiency greater than 10% has been achieved.

Ferric chloride doped polyvinyl alcohol for volume hologram recording: a characterization study

Polymer-based materials exhibit excellent properties such as ease of handling, high environmental stability, etc., and thus are promising candidates for alternate optical recording materials for holography and nonlinear optics. Polyvinyl alcohol doped with ferric chloride (FePVA) has been employed as a recording material for volume transmission holograms. A detailed characterization study of this media for volume transmission holograms has been made with the various material parameters taken into consideration. The angular selectivity of the recorded holograms and the frequency response of the media were studied in detail and the results are presented. Changes in the refractive index as a function of exposure energy were also evaluated using a prism-film coupler method. Although volume holograms recorded in FePVA films exhibited a high peak diftraction efficiency of ≈80%, the energy sensitivity of this recording medium is low. To improve the energy sensitivity, t -butyl hydroperoxide has been introduced into the film and the results of this study are presented.

Dye-doped polyvinyl alcohol recording materials for holography and nonlinear optics

Photo-induced cross-linking polymers offer excellent properties, such as ease of handling, low cost, and real-time recording, for the application of holography and nonlinear optics. A vinyl polymer, namely, polyvinyl alcohol (PVA), has been chosen as a host matrix and is employed for holographic recording and nonlinear optics. Significant results of our experimental investigations on recording media fabricated by doping PVA with azo dyes and rhodamine 6G for real-time holographic recording and nonlinear optics are reported. The evaluation of third-order nonlinearities of azo dye/PVA systems and the characteristics of chrysoidine/PVA as a nonlinear waveguide are presented. Also, degenerate four-wave mixing experiments using a novel geometry have been carried out in rhodamine 6G/PVA films.

Photobleaching of xanthene dyes in a poly(vinyl alcohol) matrix

Photobleaching of three different xanthene dyes namely, Erythrosin B (ERB), Eosin Y (EOY) and Rose Bengal (ROB) in Poly(Vinyl Alcohol) (PVA) matrix has been studied. Quantum yield values of photobleaching using an argon-ion laser (514.5 nm) were determined in presence of an electron donor (TriEthAnolamine, TEA) and/or Cr(VI). Evaluated quantum yield values suggest that erythrosin B undergoes faster photobleaching than eosin Y or rose bengal in presence of TEA. Presence of Cr(VI) in addition to TEA drastically decreases the quantum yield. Possible reaction pathways of photobleaching are discussed.

Holographic characterization of azo-dye doped poly (methyl methacrylate) films

Abstract Many holographic techniques have been developed for non-destructive studies and characterization of materials. In this paper, discussion will be made about the employed holographic technique to characterize the poly(methyl methacrylate) (PMMA) matrices doped with azo-dyes. In this manner we were able to study the effect of the thickness of the samples, the effect of concentration of the azo-dyes and of PMMA and the effect of aging (storage time) on the holographic efficiency (diffraction efficiency) of these materials. Auto-erasable holographic gratings have been successfully recorded on azo-dye doped PMMA films and the dynamic diffraction efficiency was monitored with light different from that used for the recording.