Mechanisms of giant optical nonlinearity in light-absorbing liquid crystals: a brief primer

Marrucci, Lorenzo

doi:10.1080/13583140260230264

Cited by 36 publications

(23 citation statements)

References 37 publications

(45 reference statements)

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“…The threshold intensity is determined by three balancing factors that interact with an optical field of polarized light: molecular polarizability, bulk elasticity and surface anchoring. Considering previous reports, 16,30,31 it is assumed that the threshold intensity for photoinduced molecular reorientation can be reduced by weakening the surface anchoring. This assumption was confirmed by direct evaluation of optical nonlinearity in self-diffraction ring measurements.…”

Section: Evaluation Of Optical Nonlinearity Of Pslcsmentioning

confidence: 99%

“…This assumption was confirmed by direct evaluation of optical nonlinearity in self-diffraction ring measurements. 15,16,39 The following experiments were carried out on PSLC cells treated with silane coupler concentrations above 0.003 wt% because these concentrations yielded a uniform homeotropic orientation. Effect of surface treatment on molecular reorientation K Usui et al…”

Section: Evaluation Of Optical Nonlinearity Of Pslcsmentioning

confidence: 99%

“…These torques reach a balance that determines a specific light intensity that allows reorientation of the molecular director, which means that the reorientation behavior has a well-defined threshold light intensity. 16 This NLO effect on molecular reorientation has attracted attention owing to high NLO efficiency. [17][18][19][20][21][22] When the initial homeotropic (out-of-plane) orientation is changed to homogeneous orientation with light, a large change in the refractive index is induced, which leads to a large NLO effect.…”

Section: Introductionmentioning

confidence: 99%

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Effect of surface treatment on molecular reorientation of polymer-stabilized liquid crystals doped with oligothiophene

Usui

Katayama

Wang

et al. 2016

Polym J

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Irradiation of dye-doped liquid crystals (LCs) with linearly polarized light leads to molecular reorientation, which manifests functional properties for various nonlinear optical (NLO) applications. Material designs with lower light intensity thresholds for molecular reorientation have been explored, and nematic LCs have been one of the most attractive choices because of the high NLO properties. Here we present a different approach to reduce light intensity for reorientation by modifying a substrate surface that controls initial molecular orientation in polymer-stabilized nematic LCs doped with oligothiophene. The surface of the glass substrate was treated with various concentrations of a silane coupler. Water contact angle measurement and analysis of samples using polarized optical microscopy revealed that surface anchoring in the initial state decreased as the silane coupler concentration decreased. The threshold intensity was successfully reduced by 30% simply by optimizing the silane coupler concentration. This finding clearly indicates that weak surface anchoring is key to the reduction of light intensity for molecular reorientation. INTRODUCTIONLiquid crystal (LC) materials have had a great impact on our modern information society. 1-3 Various LC materials and devices including LC displays, 3 smart windows, 4 reconfigurable optical elements 5 and tunable optical metamaterials 6 have been realized. 2 In these applications, light modulation is the most important factor and is achieved by orientational changes of LC molecules using an external field.Molecular reorientation of conventional LCs has been performed by an electric field. However, molecular reorientation triggered by an optical field has attracted attention because it enables the development of all-optical devices. 7,8 Such photoinduced molecular reorientation includes photochemical and photophysical processes. Photochemical processes control LC orientation through a photochemical reaction, for example, photoisomerization, photocrosslinking or photodegradation. [8][9][10][11][12][13][14] In contrast, a photophysical process exploits the nonlinear optical (NLO) effects of an LC. 7,15 When a homeotropic LC is vertically irradiated with linearly polarized light, the interaction between the optical field and the LC molecules generates a torque to rotate the molecular director along the polarization direction, leading to homogeneous (in-plane) orientation. On the other hand, rotation of the molecular director is disturbed both by the interaction between LCs and the glass substrate surface, a process which is also called surface anchoring, and by bulk elasticity. These torques reach a balance that determines a specific light intensity that allows

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Section: Evaluation Of Optical Nonlinearity Of Pslcsmentioning

confidence: 99%

Section: Evaluation Of Optical Nonlinearity Of Pslcsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of surface treatment on molecular reorientation of polymer-stabilized liquid crystals doped with oligothiophene

Usui

Katayama

Wang

et al. 2016

Polym J

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“…The anisotropic nature of the liquid crystals (LCs) enhances the optical nonlinearity of these materials by up to nine orders of magnitude comparing to that of isotropic fluids, 1 making these materials suitable for building electro-optical devices. LC channel waveguides capable of all-optical intensity modulation of near infrared light 2 and all-optical switches made of microstructured fibers filled with LCs 3 and dye doped nematic LCs 4 have already been demonstrated.…”

Section: Introductionmentioning

confidence: 99%

Thermal optical non-linearity of nematic mesophase enhanced by gold nanoparticles – an experimental and numerical investigation

Kurochkin

Murugesan

Bennett

et al. 2016

Phys. Chem. Chem. Phys.

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In this work the mechanisms leading to the enhancement of optical nonlinearity of nematic liquid crystalline material through localized heating by doping the liquid crystals (LCs) with gold nanoparticles (GNPs) is investigated. We present some experimental and theoretical results on the effect of voltage and nanoparticle concentration on the nonlinear response of the GNP-LC suspensions. The optical nonlinearity of these systems is characterized by diffraction measurements and the second order nonlinear refractive index, n 2 is used to compare systems with different configurations and operating conditions. A theoretical model based on heat diffusion that takes into account the intensity and finite size of the incident beam, the nanoparticle concentration dependent absorbance of the GNP doped LC systems and the presence of bounding substrates is developed and validated. We use the model to discuss possibilities of enhancing further the optical nonlinearity.

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“…Beside the already huge role that LC's play in the display industry, in the last decade or so there has been a push to take advantage of the large optical Kerr nonlinearity of LC's in a wide variety of device-applications in the optoelectronics industry [4,5,6].…”

Section: Introductionmentioning

confidence: 99%

Dynamical Study of Guest-Host Orientational Interaction in LiquidCrystalline Materials

Truong

2005

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Guest-host interaction has long been a subject of interest in many disciplines.Emphasis is often on how a small amount of guest substance could significantly affect the properties of a host material. This thesis describe our work in studying a guest-host effect where dye-doping of liquid crystalline materials greatly enhances the optical Kerr nonlinearity of the material. The dye molecules, upon excitation and via intermolecular interaction, provides an extra torque to reorient the host molecules, leading to the enhanced optical Kerr nonlinearity.We carried out a comprehensive study on the dynamics of the photoexcited dyedoped liquid crystalline medium. Using various experimental techniques, we separately characterized the dynamical responses of the relevant molecular species present in the 2 medium following photo-excitation, and thus were able to follow the transient process in which photo-excitation of the dye molecules exert through guest-host interaction a net torque on the host LC material, leading to the observed enhanced molecular reorientation.We also observed for the first time the enhanced reorientation in a pure liquid crystal system, where the guest population is created through photoexcitation of the host molecules them-

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Mechanisms of giant optical nonlinearity in light-absorbing liquid crystals: a brief primer

Cited by 36 publications

References 37 publications

Effect of surface treatment on molecular reorientation of polymer-stabilized liquid crystals doped with oligothiophene

Effect of surface treatment on molecular reorientation of polymer-stabilized liquid crystals doped with oligothiophene

Thermal optical non-linearity of nematic mesophase enhanced by gold nanoparticles – an experimental and numerical investigation

Dynamical Study of Guest-Host Orientational Interaction in LiquidCrystalline Materials

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