Laser-induced holographic light scattering in a liquid-crystalline azobenzene-containing polymer

Bogdanov, Alexey V.; Bobrovsky, Alexey; Ryabchun, Alexander; Vorobiev, Andrey Kh.

doi:10.1103/physreve.85.011704

Cited by 5 publications

(5 citation statements)

References 44 publications

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“…The earliest report of a Bragg PG was an experimental study [4] employing a azo-polymer with low birefringence Δn (∼ 0.01), achieving ≥ 90% diffraction efficiency, with Λ = 2 μm, λ = 633 nm, d = 100 μm, θ B = 9.3 • , and Q ≈ 64. However, smaller periods would require much thicker films, e.g., d = 1 mm for Λ = λ at the same Q, which is unfeasible due to the manifestation of haze and absorption [22,23]. Subsequent prior art [24,25] used numerical simulation and theoretical analysis to predict more generally that PG diffraction efficiency as high as 100% is possible in the Bragg regime for circularly polarized input and oblique incidence.…”

Section: Introductionmentioning

confidence: 99%

Nanoscale liquid crystal polymer Bragg polarization gratings

Xiang

Kim²,

Komanduri³

et al. 2017

Opt. Express

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We experimentally demonstrate nearly ideal liquid crystal (LC) polymer Bragg polarization gratings (PGs) operating at a visible wavelength of 450 nm and with a sub-wavelength period of 335 nm. Bragg PGs employ the geometric (Pancharatnam-Berry) phase, and have many properties fundamentally different than their isotropic analog. However, until now Bragg PGs with nanoscale periods (e.g., < 800 nm) have not been realized. Using photo-alignment polymers and high-birefringence LC materials, we employ multiple thin sublayers to overcome the critical thickness threshold, and use chiral dopants to induce a helical twist that effectively generates a slanted grating. These LC polymer Bragg PGs manifest 85-99% first-order efficiency, 19-29° field-of-view, Q ≈ 17, 200 nm spectral bandwidth, 84° deflection angle in air (in one case), and efficient waveguide-coupling (in another case). Compared to surface-relief and volume-holographic gratings, they show high efficiency with larger angular/spectral bandwidths and potentially simpler fabrication. These nanoscale Bragg PGs manifest a 6π rad/μm phase gradient, the largest reported for a geometric-phase hologram while maintaining a first-order efficiency near 100%.

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Section: Introductionmentioning

confidence: 99%

Nanoscale liquid crystal polymer Bragg polarization gratings

Xiang

Kim²,

Komanduri³

et al. 2017

Opt. Express

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“…Azobenzene-containing polymers have attracted numerous studies of both fundamental significance and practical potential owing to photoresponsiveness of the azobenzene chromophore. 1 Very recent advances span from ferroelectric networks with a photoswitchable second-order nonlinear optical response, 2 to laser-induced holographic light scattering polymers, 3 to hybrid supramolecular materials for processing carbon nanotubes. 4 Specifically, liquid-crystalline azobenzene polymers combine in one macromolecular structure the peculiar characteristics of the molecular mesogenic group with those typical of a polymer architecture.…”

Section: Introductionmentioning

confidence: 99%

A Rheological Investigation of Entanglement in Side-Chain Liquid-Crystalline Azobenzene Polymethacrylates

et al. 2013

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The shear rheological behavior was investigated in a series of high molar mass liquid-crystalline polymers (PMA4 homopolymer and copolymer samples) carrying an azobenzene mesogenic chromophore group in the side chains. The focus was on studying the entanglement effects and testing selected reptation models to ascertain their ability to reproduce the complex shear modulus of the copolymers. We found that ordinary dynamic models worked for the nematic PMA4 copolymers, nicely reproducing the rheological response of the materials. We were able to obtain microscopic information on the materials, such as Rouse time and entanglement molar mass, in a consistent way, as well as to get insight on the macroscopic effects of tube dilatation induced by the nematic order on the master curves of the entangled polymers. Model improvements, accounting for the different nature of the co-units, were also proposed in this work that singled out the friction coefficients of the co-units MMA and MA4. The monomeric friction coefficient ζ0MA4 was found to be constant throughout the series, (5±2)×10–9 kg s–1. Likewise, ζ0MMA had the same value throughout the series, very similar to literature data for PMMA homopolymers, (2.0±0.6)×10−8 kg s−1. Finally, in the framework of the packing length model, constant packing lengths of 3.5 Å and 13 Å throughout the series were found for MMA and MA4 co-units, respectively. Also, it resulted that the viscoelastic behavior of any PMA4 random copolymer could be predicted, provided that the response of the extreme homopolymers of the series has been characterized

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“…The resulted composite films were used for holographic recording of diffraction gratings. The polymer PAAzo has been established as a material allowing high photoinducible birefringence (or dichroism) [45,46] and was used as an active optical media for lasing. [33,47] As shown in Figure 1, the illumination of the composite film with linearly polarized light leads only to a uniaxial orientation www.advopticalmat.de of the side-chain fragments of the embedded LC polymer while the cholesteric helical structure remains unchanged since it is imprinted in the covalently crosslinked polymer network.…”

Section: Introductionmentioning

confidence: 99%

Full‐Polymer Cholesteric Composites for Transmission and Reflection Holographic Gratings

Ryabchun

Sakhno

Stumpe

et al. 2017

Advanced Optical Materials

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A new type of self‐organized materials based on cholesteric networks filled with photoactive side‐chain copolymer is being developed. Supramolecular helical structure of cholesteric polymer network resulting in the selective reflection is used as a photonic scaffold. Photochromic azobenzene‐containing nematic copolymer is embedded in cholesteric scaffold and utilized as a photoactive media for optical pattering. 1D and 2D transmission diffraction gratings are successfully recorded in composite films by holographic technique. For the first time the possibility to create selective reflection gratings in cholesteric material mimicking the natural optical properties of cholesteric mesophase is demonstrated. That enables the coexistence of two selective gratings, where one has an intrinsic cholesteric periodic helical structure and the other is a holographic grating generated in photochromic polymer. The full‐polymer composites provide high light‐induced optical anisotropy due to effective photo‐orientation of side‐chain fragments of the azobenzene‐containing liquid crystalline polymer, and prevent the degradation of the helical superstructure maintaining all optical properties of cholesteric mesophase. The proposed class of optical materials could be easily applied to a broad range of polymeric materials with specific functionality. The versatility of the adjustment and material preprogramming combined with high optical performance makes these materials a highly promising candidate for modern optical and photonic applications.

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Laser-induced holographic light scattering in a liquid-crystalline azobenzene-containing polymer

Cited by 5 publications

References 44 publications

Nanoscale liquid crystal polymer Bragg polarization gratings

Nanoscale liquid crystal polymer Bragg polarization gratings

A Rheological Investigation of Entanglement in Side-Chain Liquid-Crystalline Azobenzene Polymethacrylates

Full‐Polymer Cholesteric Composites for Transmission and Reflection Holographic Gratings

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