Model for the photoinduced formation of diffraction gratings in liquid-crystalline composite materials

Veltri, Alessandro; Caputo, Roberto; Umeton, Cesare; Sukhov, A. V.

doi:10.1063/1.1738182

Cited by 58 publications

(32 citation statements)

References 7 publications

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“…Photopolymerization is a chain reaction involving three steps [5,[12][13][14][15][16]: initiation, propagation, and termination. Initiation consists of two chemical reaction processes: the production of free radicals under illumination and the binding of a free radical with a monomer (M) to form a monomer radical.…”

Section: Theorymentioning

confidence: 99%

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Determination of threshold exposure and intensity for recording holograms in thick green-sensitive acrylamide-based photopolymer

Mahmud

Naydenova²,

Babeva³

et al. 2010

Appl. Opt.

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Mahmud, M. et al. (2010) Determination of threshold exposure and intensity for recording holograms in thick green-sensitive acrylamide-based photopolymer. Appl. Opt. vol.49, For optical data storage applications, it is essential to determine the lowest intensity (also known as threshold intensity) below or at which no data page or grating can be recorded in the photosensitive material, as this in turn determines the data capacity of the material. Here, experiments were carried out to determine the threshold intensity below which the formation of a simple hologram-a holographic diffraction grating in a green-sensitized acrylamide-based photopolymer-is not possible. Two main parameters of the recording layers-dye concentration and thickness-were varied to study the influence of the density of the generated free radicals on the holographic properties of these layers. It was observed that a minimum concentration per unit volume of free radicals is required for efficient cross-linking of the created polymer chains and for recording a hologram. The threshold intensity below which no hologram can be recorded in the Erythrosin B sensitized layers with absorbance less than 0.16 was 50 μW=cm 2 . The real-time diffraction efficiency was analyzed in the early stage of recording. It was determined that the minimum intensity required to obtain diffraction efficiency of 1% was 90 μW=cm 2 , and the minimum required exposure was 8 mJ=cm 2 . It was also determined that there is an optimum dye concentration of 1:5 × 10 −7 mol=L for effective recording above which no increase in the sensitivity of the layers is observed.

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Section: Theorymentioning

confidence: 99%

“…Termination occurs when the radical attached to the end of the growing polymer chain bonds with another radical. The photopolymerization process can be summarized as follows [5,[12][13][14][15][16]:…”

Section: Theorymentioning

confidence: 99%

Determination of threshold exposure and intensity for recording holograms in thick green-sensitive acrylamide-based photopolymer

Mahmud

Naydenova²,

Babeva³

et al. 2010

Appl. Opt.

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“…The dielectric permittivity modulations obtained for such a POLICRYPS grating is calculated accurately by a chemical-diffusion model [18]. In this model the concentration profile depends on two parameters G and B.…”

Section: Policryps Gratingsmentioning

confidence: 99%

Characterization of the diffraction efficiency of polymer-liquid-crystal-polymer-slices gratings at all incidence angles

Xu¹,

Sio²,

Caputo³

et al. 2008

Opt. Express

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Abstract:Recently, a novel holographic diffraction grating made of polymer slices alternated to homogeneous films of nematic liquid crystal (POLICRYPS) was realized. We study the optical performance of the POLICRYPS gratings by both numerical simulations and experiments. Characterization of the grating at normal and conical reading mount are performed. The diffraction efficiency depends strongly on the angles of incidence. Besides, the characterization of the diffraction efficiency at Bragg angle incidence is studied. A uniform high diffraction efficiency is achieved when the incident wave satisfies the Bragg condition.

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“…The combination of the passive properties of PCFs and the active optical properties of LCs resulted in a new kind of versatile devices, the photonic liquid crystal fibers (PLCF). PLCFs have been developed and manufactured for many applications including optical communications, signal treatment, interferometers and sensors [4][5][6][7][8][9].…”

mentioning

confidence: 99%

“…The sample is shone at about 10mW/cm 2 for about 15 min. Droplet formation is avoided by photocuring while keeping LC in isotropic phase and by applying a reduced light intensity, since diffusion plays an important role as theoretical models predict [9]. After the curing period the sample is slowly cooled down to room temperature.…”

mentioning

confidence: 99%

Recording Policryps structures in photonic crystal fibers

et al. 2017

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Model for the photoinduced formation of diffraction gratings in liquid-crystalline composite materials

Cited by 58 publications

References 7 publications

Determination of threshold exposure and intensity for recording holograms in thick green-sensitive acrylamide-based photopolymer

Determination of threshold exposure and intensity for recording holograms in thick green-sensitive acrylamide-based photopolymer

Characterization of the diffraction efficiency of polymer-liquid-crystal-polymer-slices gratings at all incidence angles

Recording Policryps structures in photonic crystal fibers

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