Influence of the coherence of spectral domain interference of Fano resonance on the degree of polarization of light

We show an intriguing connection between the coherence of spectral domain interference of two electromagnetic modes in Fano resonance and the resulting degree of polarization of light. A theoretical treatment is developed by combining a general electromagnetic model of partially coherent interference of a spectrally narrow and a broad continuum mode leading to Fano resonance and the cross-spectral density matrix of the interfering polarized fields of light. The model suggests a characteristic variation of the degree of polarization across the region of spectral dip and the peak of Fano resonance as an exclusive signature of the connection between the degree of polarization and the coherence of the interfering modes. The predictions of the model is experimentally verified in the partially polarized Fano resonance spectra from metal Chalcogenides systems, which emerged due to the interference of a narrow excitonic mode with the background continuum of scattered light in the reflectance spectra from the system. The demonstrated connection between polarization and coherence in the spectral domain Fano-type interference of electromagnetic modes is fundamentally important in the context of a broad variety of non-trivial wave phenomena that originate from fine interference effects, which may also have useful practical implications

Inhomogeneous polarization evolution resolves a fundamental issue in non-Hermitian transverse optical beam shifts

Depending on the system parameters, the transverse optical beam shift in reflection can be non-Hermitian with real eigenvalues and non-orthogonal eigenstates. We reveal that such an unusual resemblance with typical PT (parity-time)-symmetric systems originates from the beam's momentum domain polarization evolution. Specifically, for partial reflection, the momentum domain inhomogeneous polarization evolution of the beam is at the heart of all the peculiarities in the corresponding eigenspectrum of the transverse shift operator. These findings put forward the notion of novel non-Hermitian spin-orbit photonics and enable common polarization optical elements to act as PT-symmetric non-Hermitian systems

Whole-genome characterization of human group C rotaviruses: identification of two lineages in the VP3 gene

Group C rotavirus (GCRV) is distributed worldwide as an enteric pathogen in humans and animals. However, to date, whole-genome sequences are available only for a human strain (Bristol) and a porcine strain (Cowden). To investigate the genetic diversity of human GCRVs, nearly full-length sequences of all 11 RNA segments were determined for human GCRVs detected recently in India (v508), Bangladesh (BS347), China (Wu82 and YNR001) and Japan (OH567 and BK0830) and analysed phylogenetically with sequence data for GCRVs published previously. All the RNA segments of human GCRV strains except for the VP3 gene showed high levels of conservation (>93 % nucleotide sequence identity, >92 % amino acid sequence identity), belonging to a single genetic cluster distinct from those of animal GCRVs. In contrast, the VP3 genes of human GCRVs could be discriminated into two clusters, designated M2 and M3, that were distinguished phylogenetically from those of porcine and bovine GCRVs (clusters M1 and M4, respectively). Between M2 and M3, amino acid sequence identity of the VP3 gene was 84.1–84.7 %, whereas high identities were observed within each cluster (92.3–97.6 % for M2, 98.2–99.3 % for M3). Sequence divergence among the four VP3 clusters was observed throughout the amino acid sequence except for conserved motifs, including those possibly related to enzyme functions of VP3. The presence of obvious genetic diversity only in the VP3 gene among human GCRVs suggested that either the M2 or M3 VP3 gene of human GCRVs might have been derived through reassortment from an animal GCRV or from an unidentified human GCRV strain belonging to a novel genogroup

Kinetics and mechanism of the interaction of L- cysteine with diaquaethylenediamineplatinum(II) perchlorate in aqueous solution

863-866The kinetics of the interaction of L-cysteine with [Pt(en)(H20)2]2+ has been studied spectrophotometrically as a function of [Pt(en(H20)2+], [L-cysteinel, pH and temperature. The reaction has been monitored at 230 nm, where the spectral difference is maximum although the λmax, of the L-cysteine saturated product is at 213 nm. The activation parameters have been evaluated from temperature coefficient of the reaction rates. The low value of ΔH# (61.1 kJ mol-1) and large negative value of ΔS# (- 83 J k-1 mol-1) indicate an associative mode of activation for the substitution process. The additional advantage of using aquaamine complexes as an amino acid binder is also discussed

Kinetics and mechanism of anation of hydroxopentaaquarhodium(III) ion by <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0><img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-methionine

342-345The kinetics of anation of [Rh(OH2)5(OH)]2+ by -methionine has been studied spectrophotometrically by monitoring the characteristic absorption peak of the product complex (λmax = 262 nm) as a function of substrate and ligand concentrations in the 50-65°C temperature range and in the pH range 2.5-4.3. The rate law involving the outersphere complex formation has been established at pH 4.3 as . The activation parameters have been calculated and compared with those for water exchange reaction and other substitution reactions. A mechanism· involving the prior formation of an outersphere complex followed by associative interchange (Ia) is suggested where both bond making and bond breaking are equally important in the transition state

Kinetics and mechanism of the interaction of L- cysteine with diaquaethylenediamineplatinum(II) perchlorate in aqueous solution

863-866The kinetics of the interaction of L-cysteine with [Pt(en)(H20)2]2+ has been studied spectrophotometrically as a function of [Pt(en(H20)2+], [L-cysteinel, pH and temperature. The reaction has been monitored at 230 nm, where the spectral difference is maximum although the λmax, of the L-cysteine saturated product is at 213 nm. The activation parameters have been evaluated from temperature coefficient of the reaction rates. The low value of ΔH# (61.1 kJ mol-1) and large negative value of ΔS# (- 83 J k-1 mol-1) indicate an associative mode of activation for the substitution process. The additional advantage of using aquaamine complexes as an amino acid binder is also discussed

Supercontinuum Generation in Microstructured Silica Optical Fibers : The Formation of Artificial White Light

The inherent feature of nonlinear optics is the modification of the optical properties of the medium due to the interaction of the propagating high intensity light with the medium ultimately leading to the generation of new frequencies. An ultra-short optical pulse experiences spectral broadening when it is passed through a nonlinear medium such as high purity silica fiber and eventually generates artificial white light with unique spectral properties, controlled time duration and high spectral brightness. Owing to its wide and continuous spectra, such phenomenon is generally called supercontinuum (SC) generation. A variety of nonlinear processes governed by the associated pulse duration are involved in such spectral broadening. For femtosecond pump pulses, soliton dynamics plays a pivotal role whereas self-phase modulation (SPM), four wave mixing (FWM) etc are important for wider pump pulses. The generation of white light is an interesting physical phenomenon and it opens up new possibilities in the field of optical communication, optical metrology, nonlinear spectroscopy, microscopy and laser biomedicine. In the present review particular attention is paid to the description of the formation of white light in different operational conditions in highly nonlinear waveguides like photonic crystal fiber (PCF)

Efficient supercontinuum sources based on suspended core microstructured fibers

We fabricate uniform silica microstructured optical fibers (MOFs) having very simple geometry with only three rings of air holes in order to generate efficient supercontinuum (SC). The fabricated MOFs possess suspended core with comparatively larger pitch and are the most active component in a SC source. We use the suspension factor as a design parameter which significantly influences the nonlinear and dispersion properties of the MOFs. It is experimentally shown that our fabricated MOFs generate efficient SC both in femtosecond and picosecond pumping domain. We also numerically model the nonlinear dynamics for SC sources in order to identify the nonlinear processes and illustrate the spectral broadening mechanisms

Determination of modal effective indices and dispersion of microstructured fibers with different configurations: a variational approach

A simple semi-analytical model based on the variational method is developed for determining the effective indices of the fundamental modes and consecutively the dispersion properties of microstructured optical fibers (MOFs) with different lattice geometries without resorting to any numerical tool. We consider an equivalent step-index (ESI) profile of the MOF and the fundamental mode shape is approximated as a simple Gaussian function in the core. Effective index data and dispersion obtained from the proposed variational method offer reasonable agreement with numerically derived data using the Finite Element Method (FEM). The proposed model offers an alternative and swift way for reasonably precise determination of the effective index of the fundamental mode and dispersion properties of MOF designs with different lattice geometries. Finally, as a major application, the dispersion property of a fabricated MOF, derived through the proposed variational method, is directly used in order to model experimental supercontinuum (SC) spectra with satisfactory agreement