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The electro-optical properties of methyl silicone oils with viscosities ranging from 10 to 10,000 cSt have been studied extensively to verify their suitability as immersion liquids. Immersion liquids are often used in nonlinear optics to protect hygroscopic crystals from moisture, reduce multiple reflections, and protect against electrical breakdown. However, the lack of experimental data makes it difficult to select an optimal liquid that does not exhibit a significant electro-optical Kerr effect in the fringing electric field around the electrodes on the crystal. Electro-optical measurements were performed using an improved dynamic polarimetric method, which compensates for the measurement errors caused by inaccurate positioning of the electro-optical modulator's operating point on its transmission characteristics. The values of the Kerr coefficient ranged from -8.83 × 10-16 to -6.79 × 10-16 m V-2 for all oil samples, at temperatures from 25 to 80 °C and frequencies from 67 to 1017 Hz. These exceptionally low values, together with a low dielectric constant, very good transparency, and high chemical stability, make methyl silicone oils highly suitable as immersion liquids. The Kerr coefficient and other electro-optical coefficients increased with increasing temperature. This unusual result cannot be adequately explained by Buckingham's molecular theory of the Kerr effect.
RESUMO
This paper presents precise measurements of the temperature dependencies of the quadratic electro-optic coefficients g1111-g1122 and ne3g3333-no3g1133 in KH2PO4 crystals. In addition to traditional electro-optic coefficients describing changes in the function of an applied electric field, intrinsic coefficients, defined in terms of induced polarization, are also considered. Both intrinsic coefficients decrease with increases in temperature, but the relative temperature changes are of different orders of magnitude: 10-4 and 10-3 K-1. A Sénarmont-type setup was used for the electro-optic measurements. To achieve the best accuracy, a new approach was developed, in which, instead of using only one specific point on the modulator's transmission characteristic, the operating point is changed during the measurements.
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The application of the improved dynamic polarimetric method for the measurement of the quadratic electro-optic effect in NH4H2PO4 (ADP) crystal with the light beam propagating perpendicularly to its optical axis is presented. This technique can be applied in noncetrosymmetric crystals in the presence of natural birefringence even when the fast and slow rays diverge slightly, causing them to only partially interfere. The method allows for minor errors in cutting and orientation of the crystal samples, resulting in deviations from configurations in which the crystal symmetry vetoes the linear electro-optic effect. The occurring contribution of the linear effect, if it is not too large, not only does not exclude the measurement of the quadratic effect, but increases its accuracy. The method does not require any prior compensation for the natural birefringence. Its sensitivity allows for quadratic electro-optic effect measurements in ferroelectrics in temperatures significantly different from the phase transition temperature or in paraelectric crystals, for which this effect is relatively small.
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An expert program has been developed for users working in industrial laboratories who are not experts in the identification of filamentous fungi. The database of morphological growth features currently contains 12 species from the genera Aspergillus and Penicillium grown under standard conditions. The identification algorithm implemented in the database takes into account the reliability of users, which can vary over a wide range depending on the identification feature. The reliability of users was estimated on the basis of a questionnaire survey conducted among 27 non-experts, as the likelihood of a response consistent with the assessment of experts. The program works through comparative analysis of features of the fungus being identified with the expert-developed database and selection of the most likely species among the species represented by reference strains. The expert program reduces subjective mistakes and may be extended to include further fungal species and genera; it can also be supplemented with chemotaxonomic, genetic and other data.
RESUMO
Uniaxial crystals may become biaxial in an external field. The general and exact law of double refraction on the boundary of an isotropic medium and a biaxial crystal lead to an unwieldy set of involved formulas. Rotations of the principal axes of the optical permittivity tensor in the crystal subjected to the field lead to further difficulties in ray and wave tracing. Therefore, we propose a calculus in which the directions of refracted rays and waves in an unperturbed uniaxial crystal are taken as the first approximation, and then small perturbations of rays and waves due to the applied field are considered. Our approach is based on Huygens's principle and a generalized form of Fresnel's ray equation. As an example, the method is applied to the electro-optic modulation of ray and wave directions in a BaTiO(3) crystal of 4mm symmetry.
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An analytical approach is presented for studying the convergence of the general Jacobi method applied to diagonalizing the second-rank tensors that describe the optical properties of a medium subjected to an external field. This approach utilizes the fact that the components of such tensors are usually given in field-free principal axes as power series in the field strength, neglecting terms beyond a chosen power of the field. It is shown that for a biaxial or uniaxial medium, the finite number of iterations, which guarantees exact reduction of all the initial terms up to the required power in the series expansions of all off-diagonal elements, can always be found. Moreover, a fixed sequence of rotations in the Jacobi algorithm can be predicted. These findings allow one to derive analytical formulas in noniterative form for a given highest order of the effects being considered and also to optimize numerical iterative diagonalization procedures. Formulas for eigenvalues and eigenvectors applicable to biaxial and uniaxial mediums perturbed by the linear and quadratic effects are presented. Illustrations are given of the electro-optic and piezo-optic effects for the point group 3m. Conditions for biaxial and uniaxial perturbation of a uniaxial crystal are discussed.
RESUMO
Following our recent approach in which the Jones matrix calculus was applied to a modulated double-refracted and partially interfering light beam propagating in a homogeneous electro-optic crystal [J. Opt. Soc. Am. A21, 132 (2004)], we generalize the method for any distribution of the light intensity. Special attention is paid to Gaussian, flat-topped Gaussian, and quasi-Gaussian beams for which the intensity of the light emerging from the optical system is found analytically. Application of the method to an optical system with an electro-optic crystal is described.
RESUMO
The Jones matrix calculus is applied to an electro-optic crystal with uniaxial symmetry when the light beam is incident nearly normally on the crystal face. The approach allows one to treat refracted waves and rays that diverge in the crystal and are modulated by an external low-frequency field. The effect of partial interference of overlapping refracted beams is allowed for and calculated for the case of uniform intensity of the beam over its cross section. The method is employed to analyze optical systems containing an imprecisely cut and aligned electro-optic crystal plate.
