Real-time Holographic Gratings Research Articles

Real-time holographic gratings modulate with voltage by different thickness film

The holographic gratings on photopolymer films are studied by three different thicknesses for samples A, B, and C. The photopolymer emulsion is prepared with potassium dichromate and nickel (II) chloride hexahydrate in polyvinyl alcohol matrix. The evolution of diffraction efficiency is evaluated during holographic recording with and without voltage as a function of energy exposure by changing the thickness. The curves of diffraction efficiency reach a peak when the films are continuously exposed to energy for a period of time. Sample B obtains the highest diffraction efficiency

Environmental conditions influence for real-time hologram formation on dichromated polyvinyl alcohol NiCl2·6H2O doped films

The real-time holographic gratings recording are studied by the presence of a metallic salt. The experimental process refers to analysis of diffraction efficiency by the influence of humidity in the coating solution on holograms formation in presence of electrical potential. The diffraction efficiency is measured as a function of the exposure energy until reach the saturation. The influence of the hologram parameters to get the diffraction efficiency is studied at room conditions.

Real-time holographic gratings recorded by He–Ne laser in polymer films containing spirooxazine compounds pre-irradiated by UV light

Abstract Real-time holographic gratings were optically recorded with a pair of interferential He–Ne laser beams (632.8 nm) in poly(methylmethacrylate) (PMMA) film containing 6′-piperidino-1,3,3-trimethylspiro[indolino-2,3′-[3H]naphtha-[2,1-b][1,4]oxazine] (SO-1) pre-irradiated by ultraviolet light. The transformation from SO-1 to photomerocyanine (PMC) was studied in detail. PMC was observed in two forms. The holographic characteristics of the recorded gratings were dependent on the polarization direction of the recording beams. Reversible holograms were recorded in the medium by modulating UV light.

Local gratings due to angular hole burning in a photorefractive polymer

We investigate the processes involved in writing real-time holographic gratings in a photorefractive polymer (PRP) that incorporates an azo-dye. In such systems there may be gratings due to mechanisms associated with trans–cis isomerization (angular hole burning (AHB) and/or angular redistribution), which appear in addition to those arising from the photorefractive (PR) effect. The work presented here helps to understand the interactions which may occur between these different gratings.

Real‐time holographic grating by means of photoresponsive polymer liquid crystals with a flexible siloxane spacer in the side chain

The formation of real-time holographic gratings was investigated in an azobenzene polymer liquid crystal (PLC) possessing a siloxane spacer in the side chain. Irradiation of thin films of the PLCs created a phase grating which is ascribed to periodic induction of the nematic-to-isotropic (N–I) phase transition due to photochemical trans–cis isomerization of the azobenzene moiety (photochemical phase transition). It was found that the N–I phase transition temperature of the PLC with the siloxane spacer was lower than that of the PLC without the siloxane spacer owing to flexibility of the siloxane units. This property resulted in a decrease in the irradiation temperature, leading to effective induction of the photochemical N–I phase transition by suppression of thermal cis–trans back-isomerization of the azobenzene moiety. Thus formation of the grating in the PLC having the siloxane spacer could be achieved by low intensity of the interference light compared to that in conventional PLCs including only alkyl spacers. Moreover, a grating with narrower fringe spacing could be created by depression of propagation of perturbation due to trans–cis photoisomerization of the azobenzene moiety in the LC phase.

Optical Recording Characteristics Of SeGe Thin Films At A = 488 nm

Optical recording characteristics of thin films of Set 100-xGex (where x is the weight percentage) are studied using an Ar+ laser at A = 488 nm. The variation of optical transmittance due to the laser illumination and the corresponding crystallization of the thin films are examined to provide an understanding of the variation of the microstructure in the thin films during the optical recording process. The laser-induced crystallization is associated with the growth of hexagonal selenium along one or several orientations. The diffraction efficiencies of real-time holographic gratings are measured during the writing process.