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Journal ArticleDOI

Nonresonant third order susceptibility measurements in a nematic liquid crystal‐PCH‐5

15 Aug 1992-Journal of Applied Physics (American Institute of Physics)-Vol. 72, Iss: 4, pp 1495-1497
Abstract: We report for the first time the determination of the real part of the third order nonlinear susceptibility χ(3)(−ω;ω,0,0) above the nematic to isotropic phase transition temperature of a nematic liquid crystal 4 (trans‐4’‐4’‐n‐pentylcyclohexy)‐benzonirtile (PCH‐5) from electro‐optic Kerr effect experiments. The value of χ(3) observed at 632.8 nm is found to be 6.2079×10−19 m2 V−2 close to the phase transition temperature at 55.1 °C.
Topics: Liquid crystal (59%), Transition temperature (51%), Kerr effect (51%)
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Journal ArticleDOI
Hari Singh Nalwa1
01 May 1993-Advanced Materials
Abstract: The current status of organic low-molecular weight and polymeric materials for third-order nonlinear optics is reviewed. The importance of organic materials lies in their promise of large nonlinear optical figure of merit, high optical damage thresholds, ultrafast optical responses, architectural flexibility, and ease of fabrication. Organic materials exhibiting interesting third-order nonlinear optical properties are discussed to illustrate the importance of structure–property correlations. Results on emerging organic materials that include liquids, dyes, fullerenes, charge-transfer complexes, π-conjugated polymers, dye-grafted polymers, organometallic compounds, composites, and liquid crystals are presented. Organic nonlinear optical materials seem promising for a wide range of applications and their potential for integrated optics should be further explored.

395 citations

Journal ArticleDOI
Abstract: A new tolane-base liquid crystal, 4'-heptyl-3-fluoro-4-isothiocyanatotolane (7TOLF), and a biphenyl-base nematogen, 4'-heptyl-3-fluoro-4-isothiocyanatobiphenyl (7BF), have been investigated for the first time to determine their electro-optical behaviour and third order non-linearity using the static Kerr effect method. Both the nematic compounds have a fluorine atom attached to the phenyl-NCS moiety. They possess the same polar head group (-NCS) and alkyl tail (-C7H15). So the effect of the tolane group of nematogen on the electro-optical behaviour was investigated and compared. The temperature dependence of the electric Kerr constant in the isotropic phase and the pre-transitional behaviour has been investigated for these high birefringence compounds in the isotropic phase. Both the compounds have a positive and large Kerr constant which increases with decrease in temperature. The Landau–de Gennes model was obeyed for these compounds. For 7TOLF, the observed value of susceptibility, χ3 is about 228 times higher than that of CS2. The experimental Kerr effect data were also compared with those of the well-studied nematic liquid crystals.

21 citations

Journal ArticleDOI
15 Oct 1999-Synthetic Metals
Abstract: The electrical and photoelectrical properties of aryl viologen (ArV), chemically known as 1,1′-diphenyl-4,4′-bipyridinium dichloride, in the form of thin film, sandwiched between ITO and In electrode were studied The current–voltage (J–V) characteristics in dark show the rectification effect due to the formation of Schottky barrier at In–ArV interface The diode quality factor of the device, greater than unity, indicates the recombination of electron-hole in depletion region Ohmic conduction in low voltage range and space charge limited conduction (SCLC) controlled by an exponential distribution of traps above the valence band edge, for higher voltage region have been observed Various electrical parameters were calculated from the analysis of J–V and capacitance–voltage (C–V) characteristics at different temperatures and discussed in details At higher frequencies, the device exhibit voltage independent capacitance, which is explained in terms of the extremely slow kinetics of space charge and low mobility of charge carriers The photoaction spectra of the device and absorption spectra of the ArV thin film reveal that the fraction of light, which is absorbed near or within the diffusion length of exciton, is responsible for producing the free charge carriers The photovoltaic parameters were calculated from the J–V characteristics under illumination through ITO and discussed in detail

17 citations

Journal ArticleDOI
Abstract: We have observed a large nonresonant third-order nonlinear susceptibility, X(3) (-ω; ω, 0, 0) in the isotropic phase of a nematic liquid crystal 4′-n-hexyl-4-cyanobiphenyl (K18). The highest value of X(3) obtained at 632.8 nm is 1.16274×10-18 m2V-2 corresponding to a temperature 29.3°C. The observed second-order pretransitional temperature T* from our measurements is 1.2°C below the first-order nematic to isotropic transition temperature. The dependence of the Kerr constant on (T-T*)-1 is found to be in good agreement with the predictions of the Landau-de Gennes model.

4 citations

Journal ArticleDOI
Abstract: In this paper, we report for the first time the determination of the real part of the third-order nonlinear susceptibility, x (3)(−ω, ω, 0, 0), measurements in the isotropic phase of a nematic liquid crystal 4′-n-pentyl-4-cyanobiphenyl (K15) from electro-optic Kerr effect experiments. The value of x (3) obtained at 632·8 nm is found to be 1·08 × 10−18 m2 V−2 corresponding to a temperature 35·5°C and is the highest so far reported to the best of our knowledge.

2 citations

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Journal ArticleDOI
D. A. Kleinman1
15 Jun 1962-Physical Review
Abstract: The physical mechanisms which can produce second-order dielectric polarization are discussed on the basis of a simple extension of the theory of dispersion in ionic crystals. Four distinct mechanisms are described, three of which are related to the anharmonicity, second-order moment, and Raman scattering of the lattice. These mechanisms are strongly frequency dependent, since they involve ionic motions with resonant frequencies lower than the light frequency. The other mechanism is related to electronic processes of higher frequency than the light, and, therefore, is essentially flat in the range of the frequencies of optical masers. Since this range lies an order of magnitude higher than the ionic resonances, the fourth mechanism may be the dominant one. On the other hand, a consideration of the linear electro-optic effect shows that the lattice is strongly involved in this effect, and, therefore, may be very much less linear than the electrons. It is shown that the question of the mechanism involved in the second harmonic generation of light from strong laser beams may be settled by experiments which test the symmetry of the effect. The electronic mechanism is subject to further symmetry requirements beyond those for piezoelectric coefficients. In many cases, this would greatly reduce the number of independent constants describing the effect. In particular, for quartz and KDP there would be a single constant.

1,829 citations

Journal ArticleDOI
Abstract: Surface alignment of liquid crystals, T. Uchida and H. Sek interaction of electric field with liquid crystals, M.G. Clark dichroic LCDs, B. Bahadur optical computing, N. Clark and C. Johnson other types of LCDs, S. Kobayashi and A. Mochizuki thermochromic liquid crystals, I. Sage liquid crystal polymers, H. Finkelmann et al.

758 citations

Journal ArticleDOI
01 Jun 1981-Optics Letters
Abstract: Degenerate four-wave mixing experiments have been performed using a liquid suspension of 0.234-μm-diameter latex spheres as the nonlinear medium. The measured effective optical Kerr coefficient, n2, is 3.6 × 10−3 (MW/cm2)−1. This is ~105× the value for CS2. Measured grating reflectivity, formation, and decay times are in reasonable agreement with a simple model assuming Rayleigh scattering and Brownian diffusion.

193 citations

Journal ArticleDOI
Abstract: A detailed survey is given of the present-day knowledge of optical compensators. The compensators discussed are those of Babinet, Soleil, Rayleigh, De Forest Palmer, Brace, Szivessy, Senarmont, and Richartz. Each instrument is described, the theory developed, the method of use for the measurement of small phase differences given, and reference made to the sensitivity and accuracy.

156 citations

Journal ArticleDOI
01 Jun 1982-Optics Letters
TL;DR: The independence of the critical power for self-trapping on the beam diameter in the unsaturated regime was confirmed for the first time to the authors' knowledge and values of the nonlinear coefficient were determined.
Abstract: Artificial Kerr media made from liquid suspensions of submicrometer particles were used as a new type of nonlinear medium for observing cw self-focusing and self-trapping of laser beams. Self-trapping of TEM00-mode beams and higher-order TEM01- and TEM01*-mode beams were investigated. Saturation-free operation down to filament diameters of ~2 μm was observed. The independence of the critical power for self-trapping on the beam diameter in the unsaturated regime was confirmed for the first time to our knowledge. Values of the nonlinear coefficient were determined for a range of particle diameters from 0.038 to 0.234 μm.

153 citations

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