Showing papers on "Step-index profile published in 1973"

Binary SiO2–B2O3 glass system: Refractive index behavior and energy gap considerations

Abstract: A recent investigation of the binary borosilicate glass system has led to the realization of a useful cladding material for pure fused silica core fiber optical waveguides. The feature which makes the borosilicate glass useful is that its index of refraction is sufficiently less than that of pure fused silica to allow light guidance in silica core‐borosilicate clad fibers. The previous work offered no explanation for the observed but unexpected behavior of the borosilicate refractive index. Continued studies of this glass system have now led to a quantative explanation of the refractive index behavior. Two theoretical approaches are discussed. One is based on the Sellmeier dispersion model and the other on a molar refractivity analysis. The main quantities of interest turn out to be density, composition, structure, and ionicity. An important prediction based on this work is that properly quenched borosilicate glass can have a refractive index even lower than previously observed. This prediction was subseq...

Change of refractive index of water as a function of temperature

Abstract: A partially compensated Michelson interferometer with cube-corner reflectors was used to measure the change of refractive index of water as a function of temperature. The change of refractive index was observed almost continuously from 20 to 35 °C; the results indicate 1×10−5 as the upper limit of irregularities of the temperature dependence of the refractive index of water. Some deviation from a smooth curve was observed in the temperature region of 34.5 °C, indicating probable structure in the refractive-index-vs-temperature curve of water.

Refractive index of the cornea as a function of its thickness.

Abstract: This paper analyzes the relationship between corneal thickness and corneal refractive index. A refractive index change of the cornea when it thickens within the clinically observed range does not lead to a significant error in the corneal thickness measurement made by pachometry.

Refractive index behavior of garnets

Abstract: Refractive index dispersion data are reported for the iron garnets Gd2.3Tb0.7Fe5O12, Eu2Er1Ga0.7Fe4.3O12, and Eu2Er1Al0.7Fe4.3O12. Using a Sellmeier oscillator formulation these data are compared with results for several iron‐free garnets, and the relative importance of optical transitions involving Fe, Ga, and Al are briefly discussed. Finally, dispersion curves are presented for the effective refractive index n to be used in the computation of film thickness from optical interference fringe count data.

Impulse response of fibers with ring-shaped parabolic index distribution

Abstract: The index distribution in the cross section of a multimode fiber has an important influence on the modal group velocities and, hence, on the fiber impulse response. In this paper we derive a method for the evaluation of arbitrary circular symmetric index profiles. In particular, we compute the impulse response of a fiber with a ring-shaped parabolic index profile which exhibits useful equalizing properties. The pulse spread is found to be nearly one order of magnitude smaller than that of a fiber with an equal, but abrupt, index decline from core to cladding.

Method and apparatus for measuring the refractive index and diameter of optical fibers

Abstract: A method is disclosed for monitoring and controlling the refractive index profile and the diameter of optical fibers The technique is based upon an analysis of the backscattered radiation produced when an optical beam impinges upon the fiber It can be shown, by a geometrical optical analysis, that the position of a sharp cutoff in the radiation pattern is a function of the refractive index profile while the distance between two successive minima (or maxima) is a function of the fiber diameter For certain simple fiber configurations, this data can be translated directly into a number for the fiber core index and a number for the fiber core diameter For more complicated fiber configurations, such as fibers having graded-index cores, the resulting radiation pattern can be compared to that of a reference fiber, and any unusual deviations noted The method is advantageously used in conjunction with a feedback system for monitoring fibers as they are drawn, and for controlling the drawing machinery so as to maintain the fiber parameters within specified tolerances

Refractive index dispersion in semiconductor-related thin films

Abstract: A technique is described for determining refractive index dispersion throughout the uv-visible spectrum in semiconductor-related transparent thin films. The dispersion constants that have been measured can be used in the design of optical systems and in photolithography. Measurements were made with the LASER-VAMFO interferometer. Calculations and analyses are also described which show the accuracy and repeatability of the technique. Data were taken for 28 different thin-film materials, and representative refractive index dispersion curves are shown for some of them. The dispersion constants for each material evaluated are also presented.

Multilayer anti-reflection film for ultraviolet rays

Abstract: A three-layer anti-reflection film for ultraviolet range comprises a first layer having a refractive index n1 determined so as to provide a great dispersion effect in the peripheral range, a second layer having a refractive index n2, and a third layer having a refractive index n1. The three layers are arranged symmetrically. The first and third layers are provided with an asymmetry so that an intended refractive index n* for the ultraviolet range from 200mμ to 400mμ may be obtained. The film has a predetermined optical thickness.

Fiber for optical communication

Abstract: A fiber for use in an optical communications system has a core of mainly fused quartz glass of high purity having uniform refractive index in section, and an organic material coated around the outer periphery of said core and having a lower refractive index than that of said core. By choosing the half amplitude width of the incident light beam with respect to the core diameter, the increase in transmission loss due to the excitation of higher order modes is held to a minimum. The loss due to higher order mode excitation is further reduced by choosing a cladding having a dlelectric loss tangent value of about 1000 times the dielectric loss tangent in the core. Thus, the fiber may be used as an optical transmission line.

Particle-size determination by low-angle light scattering: effect of refractive index.

Abstract: The intensity of scattering I(θ) by transparent and absorbing spheres has been calculated from exact Mie theory for values of radius from 0.1 μm to 100 μm, wavelength 5461 A, and the following values of refractive index m − im′: (1) m = 1.01, 1.05, 1.1 (0.1) 2.0, m′ = 0; (2) m = 2, m′ = 0.002, 0.02, 0.2, and 2. The calculations have been made for a range of scattering angle θ large enough to indicate the first maximum in I(θ)θ2. According to the Sloan method for determining particle radius, the location of this maximum is inversely proportional to radius, independent of refractive index. The exact calculations show that this is accurate for radii above 10 μm, but for smaller particles the value of the refractive index affects the location to some extent.

Optical fiber with asymmetric index profile

Abstract: This application describes a graded-index optical fiber comprising a core having at least one planar surface that extends in a direction parallel to the direction of wave propagation The refractive index of the core material continuously decreases in the transverse direction from a maximum value at a point along the planar surface, to a minimum value at the other surfaces of the core It is an advantage of this type of fiber that two sections can be spliced together by overlapping portions of their planar surfaces rather than by butt joining