Titanium nitride as light trapping plasmonic material in silicon solar cell

ZnO nanorod arrays co-loaded with Au nanoparticles and reduced graphene oxide: Synthesis, characterization and photocatalytic application

Fabry-Perot (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.

Plasmon resonance mediated enhancement in Fabry-Pérot cavity modes

Here, we demonstrate the gas sensing ability of cavity-coupled metallic nanoparticle systems, comprising gold nanoparticles separated from a gold mirror with a polymer spacer. An increase in relative humidity (RH) causes the spacer to expand, which induces a significant reduction of nanoparticle scattering intensity, as the scattering is highly dependent on the cavity–nanoparticle coupling that closely relates to the nanoparticle–mirror distance. With high structural tolerance, i.e., no requirement for high-precision nanoparticle geometry, this lithography-free system enables a remarkable average sensitivity at 0.12 dB/% RH and 0.25 dB/% RH over a wide RH range (45–75%) and full reversibility with much faster response time than the commercial electrochemical sensors, possessing the characteristics to be used for notable gas sensing.

Efficient Plasmonic Gas Sensing Based on Cavity-Coupled Metallic Nanoparticles

Here we demonstrate the gas sensing ability of cavity-coupled metallic nanoparticle systems, comprising gold nanoparticles separated from a gold mirror with a polymer spacer. An increase in relative humidity (RH) causes the spacer to expand, which induces a significant reduction of nanoparticle scattering intensity, as the scattering is highly dependent on the cavity-nanoparticle coupling that closely relates to the nanoparticle-mirror distance. This lithography-free structure enables a remarkable averaging sensitivity at 0.12 dB/% RH and 0.25 dB/% RH over RH range (45-75%), possessing an estimated resolution better than 0.5% RH with full reversibility and almost zero-hysteresis, exhibiting notable gas sensing potentials.

Plasmonic Gas Sensing based on Cavity-Coupled Metallic Nanoparticles

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 self-defocusing. 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.

Enhanced short wave IR third order nonlinearity of gold nanoparticle embedded ZnO thin films

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.

Spectral response of nanocrystalline ZnO films embedded with Au nanoparticles

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.

Localized Surface Plasmon Resonance in Au Nanoparticles Embedded dc Sputtered ZnO Thin Films.

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.

Anuradha Patra

Papers

Plasmon resonance mediated enhancement in Fabry-Pérot cavity modes

Enhanced short wave IR third order nonlinearity of gold nanoparticle embedded ZnO thin films

Spectral response of nanocrystalline ZnO films embedded with Au nanoparticles

Localized Surface Plasmon Resonance in Au Nanoparticles Embedded dc Sputtered ZnO Thin Films.

Gold nanoparticles embedded zinc oxide films as possible optical filters