S Kasiviswanathan

Gold nanoparticle embedded ZnO thin films have been studied at the fundamental and second harmonic wavelengths of a picosecond laser by Z-scan technique. The films exhibit the effect of saturable absorption and selfdefocusing. Large value third order nonlinear susceptibility (∼10 -8 esu) has been observed at 1064 nm. Fast relaxation time measurements have been performed with the diffraction of the probe beam with laser-induced transient grating technique. Figure of merit values for optical switching applications have been obtained. One of the samples has been tested for passive mode-locking applications in combination with the standard saturable absorber, IR26. © 2013 Optical Society of America.

Multilayered structures of gold nanoparticles (AuNPs) embedded Zno films were prepared by sandwiching Au nanoparticles in between magnetron sputtered Zno films. More than 80% transmittance in visible region was observed for Zno film. For structures consisting of single and double layers of AuNPs, transmittance at ∼600 nm was reduced to ∼25% and ∼6%, respectively. AuNPs embedded sandwiches showed a huge reduction in UV Photoluminescence that was prominent in pure Zno films, and was attributed to the interband absorption in Au. © 2011 World Scientific Publishing Company.

The optical response of a two-phase composite consisting of Au nanoparticles (AuNPs) in a nanocrystalline ZnO thin film matrix has been systematically studied and analyzed by the Bergman-Milton spectral density formalism. The real and imaginary parts of the effective dielectric function exhibited anomalous dispersion and absorption, respectively, at the characteristic localized surface plasmon resonance (LSPR) wavelength. A multilayer structure consisting of two AuNP-ZnO composite films separated by a thin ZnO film displayed a twofold increase in the absorption at LSPR (with negligible change in FWHM), which is attributed to the increase in the number density of the AuNPs resulting from the nanocrystalline nature of the ZnO film. The results have been used to correlate the spectral density function to the morphology of AuNPs in a ZnO matrix. © 2012 Optical Society of America.

The plasmonic behavior of metallic nanoparticles is explicitly dependent on their shape, size and the surrounding dielectric space. This study encompasses the influence of ZnO matrix, morphology of Au nanoparticles (AuNPs) and their organization on the optical behavior of ZnO/AuNPs-ZnO/ZnO/GP structures (GP: glass plate). These structures have been grown by a multiple-step physical process, which includes dc sputtering, thermal evaporation and thermal annealing. Different analytical techniques such as scanning electron microscopy, glancing angle X-ray diffraction, Rutherford backscattering spectrometry and optical absorption have been used to study the structures. In-situ rapid thermal treatment during dc sputtering of ZnO film has been found to induce subtle changes in the morphology of AuNPs, thereby altering the profile of the plasmon band in the absorption spectra. The results have been contrasted with a recent study on the spectral response of dc magnetron sputtered ZnO films embedded with AuNPs. Initial simulation results indicate that AuNPs-ZnO/Au/GP structure reflects/absorbs UV and infrared radiations, and therefore can serve as window coatings.

Bergman effective medium theory has been used to extract effective dielectric function of Au nanoparticles (AuNPs) embedded ZnO composite thin films. The AuNPs-ZnO films have been formed by sandwiching AuNPs in between sputtered ZnO films. Dielectric function of AuNPs-ZnO composite medium has exhibited anomalous dispersion near plasmon resonance frequency. Geometric information of the two-phase composite has been drawn based on the computed Bergman spectral density function. © 2011 American Institute of Physics.

Bergman formulation has been used to extract effective dielectric function of Au nanoparticles (AuNPs) embedded metal oxide (MO) composite thin films. The extracted composite dielectric function helps further understanding ofthe resonance features in optical far-field responses. Detailed analysis on the extracted dielectric functions point towards the possibility of using them for dispersion free optics. © 2013 American Institute of Physics.

Fabry-Pérot (FP) modes of a dielectric cavity with a planar distribution of metal nanoparticles at one end have been studied numerically. An unusual enhancement in the strength of FP modes is observed close to the strong localized surface plasmon resonance of the metal nanoparticles. Experimental evidence for the numerical results has been provided by studying ZnO thin film cavities with Ag (Au) nanoparticles at one end. The enhancement in FP resonances has been interpreted in terms of a redefined cavity having a strongly dispersive adjacent medium. © 2014 AIP Publishing LLC.

Nonlinear optical properties of gold nanoparticles (AuNPs) embedded ZnO thin films have been studied at 400 nm. While the AuNPs thin film shows the effect of saturable absorption, AuNPs embedded ZnO film exhibits the RSA behaviour.