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G. S. Ranganath

Other affiliations: Indian Institute of Science
Bio: G. S. Ranganath is an academic researcher from Raman Research Institute. The author has contributed to research in topics: Liquid crystal & Diffraction. The author has an hindex of 12, co-authored 62 publications receiving 525 citations. Previous affiliations of G. S. Ranganath include Indian Institute of Science.


Papers
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Journal ArticleDOI
TL;DR: In this article, a systematic account of the structures, energies and interactions of defects in the nematic, smectic, cholesteric and discotic phases of liquid crystals is presented.
Abstract: The study of defects in ordered media has become a subject of considerable interest to condensed matter physicists in recent years. This article presents a systematic account of the structures, energies and interactions of defects in the nematic, smectic, cholesteric and discotic phases of liquid crystals. Relevant experimental observations are also described.

182 citations

Journal Article

25 citations

Journal ArticleDOI
01 Dec 1991-Pramana
TL;DR: Geometrical theory of diffraction (GTD) as mentioned in this paper is an alternative model for diffraction that reduces the problem of computing the net effect of waves from a few points on the boundary of the aperture or obstacle, thus simplifying considerably the labour involved in computations.
Abstract: Geometrical theory of diffraction (GTD) is an alternative model of diffraction propounded first by Thomas Young in 1802. GTD has a long history of nearly 150 years over which many eminent people enriched this model which has now become an accepted tool in the calculation of diffraction patterns. In the conventional Helmholtz-Kirchhoff theory the diffracted field is obtained by computing the net effect of the waves emitted by all points within the area of the aperture. But GTD reduces this problem to one of computing the net effect of waves from a few points on the boundary of the aperture or obstacle, thus simplifying considerably the labour involved in computations. Also the theory can easily be modified to include polarization effects. This has been done specifically by Keller (1962) who exploited the Sommerfeld solution of diffraction of electromagnetic waves at a half plane, making the theory more versatile than the Kirchhoff scalar wave theory. Interestingly the geometry of difffracted rays is predictable from a generalized Fermat principle. According to this the total path chosen by light from the source to the point of observation via the diffracting boundary is an extremum. Historically it should be stated that many of the salient features of GTD were established by a school led by Raman which was active from 1919–1945. Later when Keller (1962) revived GTD independently, he and others who followed him rediscovered many of the results of the Raman school. We have stressed wherever necessary the contributions of the Indian School. We have also discussed certain geometries where GTD can be effectively used. We get some new and interesting results, which can be easily understood on GTD, but are difficult to interpret on the conventional theory of diffraction.

21 citations

Journal ArticleDOI
TL;DR: A review of the earlier works on the energetics of liquid crystals can be found in this paper, where the structure and properties of disclinations in nematic and cholesteric liquid crystals are discussed.
Abstract: Continuum mechanics has been used to work out the structure and properties of disclinations in nematic and cholesteric liquid crystals. After a brief review of the earlier works on the energetics o...

20 citations

Journal ArticleDOI
TL;DR: In this phase grating mode, the optical diffraction for light propagation perpendicular to the twist axis in the chiral smectic-C liquid crystal is found in very unusual intensity and polarization features.
Abstract: We report a study on the optical diffraction for light propagation perpendicular to the twist axis in the chiral smectic-C liquid crystal. In this phase grating mode, we find very unusual intensity and polarization features in the diffraction pattern. These observed features can be explained by invoking the theory of anisotropic gratings which takes into account the internal diffractions.

19 citations


Cited by
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Journal ArticleDOI
R. Ulrich1, A. Simon1
TL;DR: In twisted single-mode optical fibers the polarization of light is affected by an elastooptically induced optical activity and by a modification of any linear birefringence present.
Abstract: In twisted single-mode optical fibers the polarization of light is affected by an elastooptically induced optical activity and by a modification of any linear birefringence present. These effects are discussed theoretically and demonstrated experimentally. The activity/twist ratio is α/τ ≃ 0.13 … 0.16 universally in weakly guiding silica fibers. Twisted fibers may be used as polarization rotators. A fiber with a ±68° double twist operates as a fast/slow mode interchanger, suitable for delay equalization.

760 citations

Journal ArticleDOI
TL;DR: In this article, the physics of colloidal dispersions in nematic liquid crystals is reviewed and three possible structures are identified and discussed in detail; the dipole, the Saturn-ring and the surface-ring configuration.

579 citations

Book ChapterDOI
01 Jan 1979

540 citations

Journal ArticleDOI
TL;DR: In this article, a class of coupled map lattices is investigated as a model for the spatiotemporal chaos, and pattern selection through the chaotic motion of domain is observed, where localized defects which separate the two anti-phase domains are found.

525 citations