Effect of isomorphic atom substitution on the refractive index and oscillator parameters of TlInS2xSe2(1-x) (0.25 ≤ x ≤ 1) layered mixed crystals

The optical properties of isomorphous mixtures produced in the laboratory have been studied by various crystallographers since the time of Senarmont, who found that the optic axial angle of mixtures of the potassium and ammonium-seignette salts was intermediate between those of the simple salts and varied gradually with the composition of the mixtures. Such artificially prepared mixtures offer better material for investigation than do the mixtures occurring as minerals, since their composition is simpler and can be varied at will. The first quantitative results were obtained by Dufet, who measured the mean refractive index (β) of mixtures of the orthorhombic sulphates of magnesium and nickel and enunciated the law: "The differences between the refractive indices of a mixture of two isomorphous salts and those of the component salts are inversely proportional to the numbers of molecules of the two salts in the mixture.” This is equivalent to the statement that in (orthorhombic) mixed crystals the refractive index of a mixture is a linear function of its composition as expressed in molecular percentage. Thus, if N n' n" are the refractive indices of the mixed crystal and of the two components, respectively, and m' m" are the molecular percentages of the two components N = m'n' + m"n" /100.

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TEM characterization of proton-exchanged LiNbO3 optical waveguides

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010014395x ◽

1986 ◽

Vol 44 ◽

pp. 480-481

Author(s):

W. E. Lee

Keyword(s):

Refractive Index ◽

Benzoic Acid ◽

Optical Waveguides ◽

Total Internal Reflection ◽

Index Of Refraction ◽

Optical Measurements ◽

Lithium Ions ◽

Wide Channel ◽

Tem Characterization

An optical waveguide consists of a several-micron wide channel with a slightly different index of refraction than the host substrate; light can be trapped in the channel by total internal reflection.Optical waveguides can be formed from single-crystal LiNbO3 using the proton exhange technique. In this technique, polished specimens are masked with polycrystal1ine chromium in such a way as to leave 3-13 μm wide channels. These are held in benzoic acid at 249°C for 5 minutes allowing protons to exchange for lithium ions within the channels causing an increase in the refractive index of the channel and creating the waveguide. Unfortunately, optical measurements often reveal a loss in waveguiding ability up to several weeks after exchange.

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Light microscopy of ceramics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015037x ◽

1993 ◽

Vol 51 ◽

pp. 908-909

Author(s):

Walter C. McCrone

Keyword(s):

Refractive Index ◽

Light Microscopy ◽

Light Microscope ◽

Polarized Light ◽

Refractive Indices ◽

Complete Coverage ◽

The Subject ◽

Lower Refractive Index

An excellent chapter on this subject by V.D. Fréchette appeared in a book edited by L.L. Hench and R.W. Gould in 1971 (1). That chapter with the references cited there provides a very complete coverage of the subject. I will add a more complete coverage of an important polarized light microscope (PLM) technique developed more recently (2). Dispersion staining is based on refractive index and its variation with wavelength (dispersion of index). A particle of, say almandite, a garnet, has refractive indices of nF = 1.789 nm, nD = 1.780 nm and nC = 1.775 nm. A Cargille refractive index liquid having nD = 1.780 nm will have nF = 1.810 and nC = 1.768 nm. Almandite grains will disappear in that liquid when observed with a beam of 589 nm light (D-line), but it will have a lower refractive index than that liquid with 486 nm light (F-line), and a higher index than that liquid with 656 nm light (C-line).

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