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Somnath Ghosh

Bio: Somnath Ghosh is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Microstructured optical fiber & Optical fiber. The author has an hindex of 28, co-authored 287 publications receiving 3318 citations. Previous affiliations of Somnath Ghosh include University of Calcutta & Indian Institute of Science.


Papers
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TL;DR: In this paper, a simple two-step approach is used to fabricate controllable biaxial and uniaxially nanowrinkles based on shape memory polymer (prestressed polystyrene) sheets.
Abstract: (Figure Presented) Controllable biaxial and uniaxial nanowrinkles (see figure) are fabricated by a simple two-step approach - metal deposition and subsequent heating - based on shape memory polymer (prestressed polystyrene) sheets. The wavelengths of the wrinkles can be tuned by controlling the thickness of deposited metal. The ready integration of the nanowrinkles into microchannels and their effectiveness in surface enhanced sensing is demonstrated. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.

220 citations

Journal ArticleDOI
TL;DR: In this article, a highly homogeneous ZnO/Ag nanohybrid has been synthesized by a novel route, employing chitosan as mediator by purely electrostatic interaction.
Abstract: A highly homogeneous ZnO/Ag nanohybrid has been synthesized by a novel route, employing chitosan as mediator by purely electrostatic interaction. By employing various techniques such as powder XRD, UV-visible, IR spectroscopy and electron (SEM, TEM) microscopy, the formation of the nanohybrid has been established. The synergistic antibacterial effect of ZnO/Ag nanohybrid on Gram-positive and Gram-negative bacteria is found to be more effective, compared to the individual components (ZnO and Ag). Cytotoxicity experiments are carried out and the results are correlated to the solubility of the nanohybrid. A possible mechanism has been proposed for the antibacterial activity of ZnO/Ag nanohybrid, based on TEM studies on bacteria, carried out by employing the microtome technique and by EPR measurements on the hybrid.

157 citations

Journal ArticleDOI
TL;DR: Highly stable silver nanoparticles in agar-agar (Ag/agar) as inorganic-organic hybrid were obtained as free-standing film by in situ reduction of silver nitrate by ethanol and the mechanical strength of the film determined by nanoindentation technique showed almost retention of the strength even after repeated cycle.

102 citations

Journal ArticleDOI
TL;DR: The general physical conditions required for capturing sliding drops on an inclined plane that is equipped with electrically tunable wetting defects are determined and it is shown that electrically Tunable defects can be used to guide sliding drops along actively switchable tracks—with potential applications in microfluidics.
Abstract: Controlling the motion of drops on solid surfaces is crucial in many natural phenomena and technological processes including the collection and removal of rain drops, cleaning technology and heat exchangers Topographic and chemical heterogeneities on solid surfaces give rise to pinning forces that can capture and steer drops in desired directions Here we determine general physical conditions required for capturing sliding drops on an inclined plane that is equipped with electrically tunable wetting defects By mapping the drop dynamics on the one-dimensional motion of a point mass, we demonstrate that the trapping process is controlled by two dimensionless parameters, the trapping strength measured in units of the driving force and the ratio between a viscous and an inertial time scale Complementary experiments involving superhydrophobic surfaces with wetting defects demonstrate the general applicability of the concept Moreover, we show that electrically tunable defects can be used to guide sliding drops along actively switchable tracks—with potential applications in microfluidics

96 citations

Journal ArticleDOI
TL;DR: In this paper, a generalized version of the AAH model is developed, containing a tunable phase shift between on-site and off-diagonal modulations, which can be induced by varying just this phase, keeping all other model parameters constant.
Abstract: A generalization of the Aubry-Andr\'e-Harper (AAH) model is developed, containing a tunable phase shift between on-site and off-diagonal modulations. A localization transition can be induced by varying just this phase, keeping all other model parameters constant. The complete localization phase diagram is obtained. Unlike the original AAH model, the generalized model can exhibit a transition between topologically trivial band structures and topologically nontrivial band structures containing protected boundary states. These boundary states can be pumped across the system by adiabatic variations in the phase shift parameter. The model can also be used to demonstrate the phenomenon of adiabatic pumping breakdown due to localization.

96 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
04 Jan 2019-Science
TL;DR: The topic of exceptional points in photonics is reviewed and some of the possible exotic behavior that might be expected from engineering such systems are explored, as well as new angle of utilizing gain and loss as new degrees of freedom, in stark contrast with the traditional approach of avoiding these elements.
Abstract: BACKGROUND Singularities are critical points for which the behavior of a mathematical model governing a physical system is of a fundamentally different nature compared to the neighboring points. Exceptional points are spectral singularities in the parameter space of a system in which two or more eigenvalues, and their corresponding eigenvectors, simultaneously coalesce. Such degeneracies are peculiar features of nonconservative systems that exchange energy with their surrounding environment. In the past two decades, there has been a growing interest in investigating such nonconservative systems, particularly in connection with the quantum mechanics notions of parity-time symmetry, after the realization that some non-Hermitian Hamiltonians exhibit entirely real spectra. Lately, non-Hermitian systems have raised considerable attention in photonics, given that optical gain and loss can be integrated as nonconservative ingredients to create artificial materials and structures with altogether new optical properties. ADVANCES As we introduce gain and loss in a nanophotonic system, the emergence of exceptional point singularities dramatically alters the overall response, leading to a range of exotic functionalities associated with abrupt phase transitions in the eigenvalue spectrum. Even though such a peculiar effect has been known theoretically for several years, its controllable realization has not been made possible until recently and with advances in exploiting gain and loss in guided-wave photonic systems. As shown in a range of recent theoretical and experimental works, this property creates opportunities for ultrasensitive measurements and for manipulating the modal content of multimode lasers. In addition, adiabatic parametric evolution around exceptional points provides interesting schemes for topological energy transfer and designing mode and polarization converters in photonics. Lately, non-Hermitian degeneracies have also been exploited for the design of laser systems, new nonlinear optics phenomena, and exotic scattering features in open systems. OUTLOOK Thus far, non-Hermitian systems have been largely disregarded owing to the dominance of the Hermitian theories in most areas of physics. Recent advances in the theory of non-Hermitian systems in connection with exceptional point singularities has revolutionized our understanding of such complex systems. In the context of optics and photonics, in particular, this topic is highly important because of the ubiquity of nonconservative elements of gain and loss. In this regard, the theoretical developments in the field of non-Hermitian physics have allowed us to revisit some of the well-established platforms with a new angle of utilizing gain and loss as new degrees of freedom, in stark contrast with the traditional approach of avoiding these elements. On the experimental front, progress in fabrication technologies has allowed for harnessing gain and loss in chip-scale photonic systems. These theoretical and experimental developments have put forward new schemes for controlling the functionality of micro- and nanophotonic devices. This is mainly based on the anomalous parameter dependence in the response of non-Hermitian systems when operating around exceptional point singularities. Such effects can have important ramifications in controlling light in new nanophotonic device designs, which are fundamentally based on engineering the interplay of coupling and dissipation and amplification mechanisms in multimode systems. Potential applications of such designs reside in coupled-cavity laser sources with better coherence properties, coupled nonlinear resonators with engineered dispersion, compact polarization and spatial mode converters, and highly efficient reconfigurable diffraction surfaces. In addition, the notion of the exceptional point provides opportunities to take advantage of the inevitable dissipation in environments such as plasmonic and semiconductor materials, which play a key role in optoelectronics. Finally, emerging platforms such as optomechanical cavities provide opportunities to investigate exceptional points and their associated phenomena in multiphysics systems.

1,276 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive review of shape-memory polymers (SMPs) and their derivatives, such as composites and compound structures, as well as their current applications are presented.

1,034 citations

Journal ArticleDOI
19 Apr 2013-Polymer
TL;DR: An up-to-date review on shape memory polymer composites with potential applications in biomedical devices, aerospace, textiles, civil engineering, bionics engineering, energy, electronic engineering, and household products is presented.

981 citations