Spontaneous polarization-vector-reorientation photorefractive effect in ferroelectric liquid crystals

Sasaki, Takeo; Kino, Yuji; Shibata, Minoru; Mizusaki, Naoko; Katsuragi, Atsushi; Ishikawa, Yuichi; Yoshimi, Takeshi

doi:10.1063/1.1379595

Cited by 27 publications

(24 citation statements)

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“…In our experimental conditions we measure C = 125 cm ±1 for an applied potential of only 50 V, i.e., at an applied field of E = 5.4 V lm ±1 . This value is higher than that previously reported [17,18] for doped photorefractive SmC* phases, although it is obtained at higher applied fields. It was not possible to obtain a complete field dependence of C, since for lower fields the signal was low, probably because of inefficient charge generation, and dielectric breakdown prevented the application of higher fields.…”

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confidence: 71%

Undoped Photorefractive Ferroelectric Liquid Crystal

et al. 2003

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Light-sensitive media constitute a class of materials that are extensively studied because of their technological relevance for a variety of applications. In particular, the non-local reversible refractive index control by light, which is possible in substances exhibiting photorefractive properties, is of wide interest for real-time holography.[1] Photorefractivity is observed in photoconductors when a spacially non-uniform light exposure generates charge carriers which redistribute over macroscopic distances. This causes an electric field, which affects the refractive index of the material. Driven by the aim of obtaining low-cost and easily processable media, many efforts have been devoted to the understanding of the photorefractive properties of organic amorphous glasses [2±4] and polymers, [5±9] followed more recently by the interest in photorefractive liquid crystals. [10] Mesophases are attractive for photorefractivity because of their high spontaneous birefringence and the wide variety of field-induced refractive index control mechanisms.[11] The first liquid crystals studied for their photorefractive properties were bulk [12±14] and dispersed [15,16] nematic materials, but in the last years a number of investigations have showed that smectic phases can be photorefractive as well. [17±19] In particular, studies were carried out on chiral smectic A and C phases, where the mechanisms of field-induced fast molecular reorientation are connected with an induced or permanent polarization, respectively. [20] In all the reported investigations, the liquid-crystalline phase is not intrinsically photoconducting, so that the space±charge field set up is achieved either by dissolving a light sensitizer (and often a charge-transport agent as well) within its bulk, or by placing the mesophase within (like in dispersed systems), or between layers of, a photoconducting material. In this work the first example of a smectic mesophase that exhibits photorefractive behavior without any doping will be presented. It will also be shown that the observed photorefractive performance is larger than that previously reported for doped systems. Our approach is based on two recent results: the observation of photorefractivity in amorphous glasses formed by cyclopalladated complexes [21] and the synthesis of a new complex, with a closely related molecular structure, which exhibits a chiral smectic C phase. [22] The mesomorphic behavior of this complex, with a structure shown in Figure 1a and called for simplicity AzPdL, was investigated by optical microscopy, differential scanning calorimetry (DSC) and low-angle X-ray diffraction measurements. The observed transition temperatures between the isotropic (I), cholesteric (N*), chiral smectic C (SmC*) and crystalline (Cr) phases are included in Figure 1a.

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confidence: 71%

Undoped Photorefractive Ferroelectric Liquid Crystal

et al. 2003

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“…5. The behavior of the spontaneous polarization with variation in the temperature is the same as those reported for other FLCs [20][21][22][23] i.e. the magnitude of the spontaneous polarization is continuously decreasing and it vanishes at the SmC*-SmA phase transition point or near this phase transition point.…”

Section: Resultssupporting

confidence: 61%

Reduction of optical response time for fluorescent dye doped ferroelectric liquid crystal

Misra

Tripathi

Manohar

2012

Journal of Molecular Liquids

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“…[36][37][38][39][40][41][42] FLCs are classified as chiral smectic C (SmC Ã ) liquid crystals that form a layered structure. [58][59][60] In the SmC Ã phase, the long axis of each FLC molecule tilts from the layer normal.…”

Section: Photorefractive Effect Of Ferroelectric Lcsmentioning

confidence: 99%

“…[36][37][38][39][40][41] A commercially available FLC, SCE8, was used. The concentrations of CDH and TNF were 2 and 0.1 wt % respectively.…”

Section: Two-beam Coupling Experiments Using Flcsmentioning

confidence: 99%

“…2 Several reviews on the development of photorefractive materials have been published. [3][4][5][6][7] The photorefractive effect has been reported in several organic materials since 1990, such as glassy polymers, [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] low-molecular-weight nematic liquid crystals, [24][25][26][27][28] liquid crystalline polymers, [29][30][31][32][33][34][35] ferroelectric liquid crystals, [36][37][38][39][40][41][42] polymer/liquid crystal composites [43][44][45][46][47][48][49][50]…”

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Photorefractive Effect of Liquid Crystalline Materials

Sasaki

2005

Polym J

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ABSTRACT:This paper reviews our recent work on the photorefractive effect in liquid crystalline materials. The photorefractive effect is defined as the optical modulation of the refractive index of a medium as a result of various processes. The interference of two laser beams in a photorefractive material establishes a refractive index grating. This phenomenon enables the creation of different types of photonic applications. Recently, the development of organic photorefractive materials has been attracting great interest. Liquid crystalline materials are a strong candidate for practical photorefractive materials and application. In this paper, the photorefractivity of liquid crystalline polymers and ferroelectric liquid crystals is described. [DOI 10.1295 The photorefractive effect is a phenomenon wherein a change in the refractive index of a material is induced by the absorption of light. The change in refractive index through the photorefractive effect occurs only within the interference fringes of incident laser beams. When laser beams interfere in a photorefractive material, charge separation occurs between the light and the dark positions of the interference fringes. A space-charge field, an internal electric field, develops at the areas between the light and the dark positions. The refractive index of the corresponding areas is changed through an electro-optic effect. Thus, a refractive index grating is formed at the interference fringes.Dynamic volume-holograms are easily formed through the photorefractive effect, and this has direct applicability in photonics, including optical image processing, parallel optical logic, fringe recognition, and phase conjugation. The photorefractive effect was first observed in the inorganic crystal lithium niobate in 1967.1 It was also subsequently observed in an organic material in 1990.2 Several reviews on the development of photorefractive materials have been published. [3][4][5][6][7] The photorefractive effect has been reported in several organic materials since 1990, such as glassy polymers, [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] low-molecular-weight nematic liquid crystals, 24-28 liquid crystalline polymers, [29][30][31][32][33][34][35] ferroelectric liquid crystals, 36-42 polymer/liquid crystal composites 43-55 and amorphous compounds, 56,57 and extremely high photorefractivity values have been achieved in organic polymeric materials. The high photorefractivity in polymeric materials arises from changes in the orientations of the chromophores induced by the internal electric field, termed orientational enhancement. 4,15,17 The photorefractive efficiency of organic materials is several times that of inorganic photorefractive crystals. In addition, organic polymers can easily be processed into films and fibers. This is a significant advantage for applications in photonics.

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Spontaneous polarization-vector-reorientation photorefractive effect in ferroelectric liquid crystals

Cited by 27 publications

References 20 publications

Undoped Photorefractive Ferroelectric Liquid Crystal

Undoped Photorefractive Ferroelectric Liquid Crystal

Reduction of optical response time for fluorescent dye doped ferroelectric liquid crystal

Photorefractive Effect of Liquid Crystalline Materials

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