Light-induced second-harmonic generation in azo-dye polymers.
TL;DR: The permanent all-optical poling of an azo-aromatic acrylic copolymer is experimentally demonstrated by seeding preparation in a backward phase-conjugation geometry by monitoring the characteristic kinetics of monitored by second-harmonic generation.
Abstract: The permanent all-optical poling of an azo-aromatic acrylic copolymer is experimentally demonstrated by seeding preparation in a backward phase-conjugation geometry. The microscopic mechanism involves an orientational hole burning followed by orientational redistribution caused by trans-to-cis isomerization of the azo-dye chromophores. The characteristic kinetics of growth and decay of the noncentrosymmetry grating is monitored by second-harmonic generation.
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TL;DR: A brief survey of NLO polymeric materials based on azobenzene units and of high thermal and temporal stability can be found in this paper, where a wide range of additional applications of azobenene chromophore is summarized, including photorefractivity, all-optical poling, holographic surface relief gratings, photo-assisted poling and optical data storage based on photochromism.
533 citations
TL;DR: In this paper, the authors show that the choice of ligand can further increase the optical nonlinearity of ruthenium complexes to values in excess of 10-27e.s.u.
Abstract: OPTICALLY nonlinear organic materials show considerable potential for applications in optical signal processing and telecommunications1,2. Most materials are based on the p-nitro-aniline template, in which the optical nonlinearities are intimately associated with quasi-one-dimensional charge transfer. But there are problems associated with this conventional approach, arising from the strongly dipolar nature of the molecules2. It has recently been recognized3–5 that two- and three-dimensional stereochemistry offers new possibilities for the design and synthesis of optically nonlinear molecules, in which charge transfer is multidirectional rather than dipolar in character; octupolar nonlinearities have now been demonstrated in several molecular systems5–7. Tri-substituted ruthenium complexes6 appear particularly attractive because intense, multidirectional metal-to-ligand charge transfer leads to a significant enhancement of the optical nonlinearity, as quantified by the quadratic hyperpolarizability, β. Here we show that the choice of ligand can further increase β to values in excess of 10-27e.s.u., comparable to the best dipolar optically nonlinear molecules.
302 citations
TL;DR: In this article, a simple diffusion model was proposed to account for the essential dynamic features of surface-relief grating formation, accounting for intensity and polarization dependences, and it opened new perspectives associated with optically controlled anisotropic diffusion.
Abstract: Large-amplitude negative holographic surface-relief gratings are optically induced by resonant visible exposure in azobenzene dye-containing polymers. We propose a simple diffusion model accounting for the essential dynamic features of surface-relief grating formation. It accounts for intensity and polarization dependences. Understanding of the process appears to be essential for holographic grating applications. It opens new perspectives associated with optically controlled anisotropic diffusion.
280 citations
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TL;DR: In this article, a new mechanism for liquid-crystal alignment that uses polarized laser light was proposed. But it was not shown to be effective for large-area displays, optical memories, binary optics, adaptive optics and molecular micro-assembly.
Abstract: THE control of molecular alignment in liquid-crystal phases at macroscopic scales has been investigated extensively because of its importance in optical or optoelectronic applications, such as liquid-crystal displays1. It is well established that liquid crystals can be aligned by an applied electric field, a magnetic field, a shear-flow field, mechanical grooving of the substrate surface or stretching of liquid-crystal polymer thin films2,3. Here we report a new mechanism for liquid-crystal alignment that uses polarized laser light. We find that nematic liquid crystals in an illuminated region become oriented perpendicular to the direction of the electric-field polarization of the laser and remain aligned in the absence of the laser radiation. The liquid crystals can be reoriented again by subsequent illumination. This technique might have applications for large-area displays, optical memories, binary optics, adaptive optics and molecular micro-assembly.
1,044 citations
TL;DR: This experiment supports a mechanism for photoinducing an alternating second-order nonlinearity in the fiber by generating second-harmonic light from a single-mode fiber after a few minutes of seeding with 532-nm harmonic light along with 1.064-microm pump light.
Abstract: We generated second-harmonic light from a single-mode fiber after a few minutes of seeding with 532-nm harmonic light along with 1.064-μm pump light. This experiment supports a mechanism for photoinducing an alternating second-order nonlinearity in the fiber.
408 citations
TL;DR: In this paper, optically induced reorientation of the azoaromatic molecules will have wide applications in image recording and in electro-optical devices, and the resulting polarization information is easily detected and exhibits long-term stability.
Abstract: Dichroism and birefringence are shown to be optically induced and erased in high‐glass‐transition azoaromatic polymers. The resulting polarization information is easily detected and exhibits long‐term stability. This optically induced reorientation of the azoaromatic molecules will have wide applications in image recording and in electro‐optical devices.
306 citations
TL;DR: In this paper, it was shown that in the presence of a DC electric field, the redistribution is not centrosymmetric and produces a poling of the film, and the evolution of the second-order nonlinear susceptibility, χ(2), was monitored by measuring the electro-optic effect by attenuated total reflection and by second-harmonic generation.
Abstract: The reversible cis-trans photoisomerization of disperse red 1 (DR1) in PMMA thin films has been demonstrated to be strongly polarization sensitive [1]. In this communication two mechanisms are identified: the angular hole burning and the angular redistribution of molecules. It is shown that, in the presence of a DC electric field, the redistribution is not centrosymmetric and produces a poling of the film. The evolution of the second-order nonlinear susceptibility, χ(2), is monitored by measuring the electro-optic effect by attenuated total reflection and by second-harmonic generation.
277 citations