Laser interference refractometer for monitoring the absolute index of refraction of air

An interference gas refractometer circuit based on a unimodal laser is proposed. By means of the device it is possible to measure the absolute index of refraction of air over a broad range with error at most 10⁻⁸. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 25–31, April 1998.     

Metamaterials with gradient negative index of refraction

We propose a new metamaterial with a gradient negative index of refraction, which can focus a collimated beam of light coming from a distant object. A slab of the negative refractive index metamaterial has a focal length that can be tuned by changing the gradient of the negative refractive index. A thin metal film pierced with holes of appropriate size or spacing between them can be used as a metamaterial with the gradient negative index of refraction. We use finite-difference time-domain calculations to show the focusing of a plane electromagnetic wave passing through a system of equidistantly spaced holes in a metal slab with decreasing diameters toward the edges of the slab.     

A liquid laser interference refractometer for measuring the concentration of solutions

A liquid interference refractometer is described. The results of an investigation of the instrument and of its practical use to measure the concentration of aqueous solutions of caprolactam are presented.Translated from Izmeritelnaya Tekhnika, No. 12, pp. 58–61, December, 2004.This revised version was published online in April 2005 with a corrected cover date.     

A scheme for the automatic generation of triangular finite elements

This paper describes a method for the automatic triangulation of arbitrary multilateral plane domains. In addition, the method can be used in connection with that suggested by Zienkiewicz and Phillips⁴ for the subdivision of curved-boundary domains. The method can be described as general fully automatic and computer oriented. A Fortran computer program has been prepared by the author. Output can be of interactive, graphical or alphanumerical form. The program has been applied to a number of cases. The resulting triangulations are always satisfactory, even when vigorous changes of mesh sizes are encountered.     

Empirical equation for the index of refraction of seawater

We have determined an empirical equation for the index of refraction of water as a function of temperature, salinity, and wavelength at atmospheric pressure. The experimental data selected by Austin and Halikas ["The index of refraction of seawater," SIO Ref. 76-1 (Scripps Institution of Oceanography, La Jolla, Calif., 1976)] were fitted to power series in the variables. A ten-parameter empirical equation that reproduces the original data to within its experimental errors was obtained.     

A method for the automatic generation of triangular elements on a surface

An algorithm is given to discretize a polygon or curved surface into triangular arrays. The method first involves the manual division of the array into quadrilaterals with specified numbers on rows and columns. The individual points are then filled in automatically and elements are automatically generated. A point of particular importance is that the number of columns or rows may be made to change. A subroutine is given to perform this task.     

Optical analysis of time-averaged multiscale Bessel beams generated by a tunable acoustic gradient index of refraction lens

Current methods for generating Bessel beams are limited to fixed beam sizes or, in the case of conventional adaptive optics, relatively long switching times between beam shapes. We analyze the multiscale Bessel beams created using an alternative rapidly switchable device: a tunable acoustic gradient index (TAG) lens. The shape of the beams and their nondiffracting, self-healing characteristics are studied experimentally and explained theoretically using both geometric and Fourier optics. By adjusting the electrical driving signal, we can tune the ring spacings, the size of the central spot, and the working distance of the lens. The results presented here will enable researchers to employ dynamic Bessel beams generated by TAG lenses.     

Models for the wavelength dependence of the index of refraction of water

Models for the index of refraction of water are reviewed and reduced to wavelength-dependent formulas. A simple three-term nonlinear model derived from Quan and Fry [Appl. Opt. 34, 3477-3480 (1995)], originally developed for the visible region, fits the available data well over an extended range covering the UV to the near-IR (200-1100 nm).     

A multichannel laser system for automatic vibration control

Translated from Izmeritel'naya Tekhnika, No. 8, pp. 35–37, August, 1991.     

A non-linear structural relaxation model for the refractive index of glass during annealing

A two internal thermodynamic ordering parameter non-linear model is used to explain the structural relaxation of glass. These two internal thermodynamic ordering parameters are also used to characterize the frozen-in structural state of glass. For an isobaric isothermal annealing process, the internal state of the glass can be characterized by the two internal ordering parameters such as fictive temperature,T _f, and configurational part of activation energy,H _s. Therefore, these two internal thermodynamic ordering parameters are used in a non-linear structural relaxation model of glass for explaining the volume relaxation and predicting the refractive index of glass during annealing, and they are also extended to characterize the thermal history of the frozen-in structure of the glassy state.     

一种液体折射率的薄膜干涉测量方法

理论分析表明在镀有金属分光膜的玻璃介质和金属介质构成的几何楔形成的斐索干涉条纹中,相长干涉并不位于相邻的两相消干涉的中央,而是存在一明显偏移,这一偏移与引入几何楔中待测液体的折射率相关.基于该原理,提出了一种新的折射率测量的方法,并对该方进行了实验验证.该方法不需要利用标准液对光学几何量进行标定,测量范围广.     

The variation of the index of refraction in a vortex tube

Three models of a vortex tube (isentropic, isothermal, and isochoric) are considered as optical inhomogeneities. Expressions relating the index of refraction to the coordinate are obtained. The possibility of obtaining Schlieren pictures of such flows is discussed.Notation a speed of sound - n index of refraction - p pressure - r radius - T absolute temperature - v linear velocity - angular deflection of the beam - x adiabatic exponent - density - angular velocity - ¯v, ¯p etc. dimensionless parameters - v₀, ₀ values at the core bounboundary - p, etc. stagnation values - n_c index of refraction at center of vortex     

Polarization-based index of refraction and reflection angle estimation for remote sensing applications

A passive-polarization-based imaging system records the polarization state of light reflected by objects that are illuminated with an unpolarized and generally uncontrolled source. Such systems can be useful in many remote sensing applications including target detection, object segmentation, and material classification. We present a method to jointly estimate the complex index of refraction and the reflection angle (reflected zenith angle) of a target from multiple measurements collected by a passive polarimeter. An expression for the degree of polarization is derived from the microfacet polarimetric bidirectional reflectance model for the case of scattering in the plane of incidence. Using this expression, we develop a nonlinear least-squares estimation algorithm for extracting an apparent index of refraction and the reflection angle from a set of polarization measurements collected from multiple source positions. Computer simulation results show that the estimation accuracy generally improves with an increasing number of source position measurements. Laboratory results indicate that the proposed method is effective for recovering the reflection angle and that the estimated index of refraction provides a feature vector that is robust to the reflection angle.