Tip-enhanced Stokes and anti-Stokes Raman scattering in defect-enriched carbon films

Anti-Stokes Raman scattering is one of the mechanisms that lie behind an optical refrigeration due to release of photons with greater energy than of incoming photons. To achieve a cooling regime the enhancement of anti-Stokes scattering is necessary, since spontaneous Stokes scattering dominates over anti-Stokes scattering under normal conditions. Here, we investigate the opportunity of enhancement of spontaneous anti-Stokes Raman scattering in defect-enriched carbon film by means of localized plasmon resonances. In our simulations, incoherence of Raman scattering results in excess of anti-Stokes intensity over Stokes one. However, when the field is localized within the phonon coherence volume (coherent regime), the anti-Stokes intensity is lower compared to Stokes one. The provided analysis shows that plasmon-enhanced anti-Stokes Raman scattering can be achieved in highly-defective carbon films. The results are beneficial for Raman-based temperature measurements on the nanoscale.

Large-area flexible nanostripe electrodes featuring plasmon hybridization engineering

Multifunctional flexible Au electrodes based on one-dimensional (1D) arrays of plasmonic gratings are nanofabricated over large areas with an engineered variant of laser interference lithography optimized for low-cost transparent templates. Au nanostripe (NS) arrays achieve sheet resistance in the order of 20 Ohm/square on large areas (∼ cm2) and are characterized by a strong and dichroic plasmonic response which can be easily tuned across the visible (VIS) to near-infrared (NIR) spectral range by tailoring their cross-sectional morphology. Stacking vertically a second nanostripe, separated by a nanometer scale dielectric gap, we form near-field coupled Au/SiO2/Au dimers which feature hybridization of their localized plasmon resonances, strong local field-enhancements and a redshift of the resonance towards the NIR range. The possibility to combine excellent transport properties and optical transparency on the same plasmonic metasurface template is appealing in applications where low-energy photon management is mandatory like e.g., in plasmon enhanced spectroscopies or in photon harvesting for ultrathin photovoltaic devices. The remarkable lateral order of the plasmonic NS gratings provides an additional degree of freedom for tailoring the optical response of the multifunctional electrodes via the excitation of surface lattice resonances, a Fano-like coupling between the broad localised plasmonic resonances and the collective sharp Rayleigh modes.

Влияние адсорбированных атомов металлов на поглощение света поверхностью кварца

The optical properties of submonolayer metal films - silver, gold, indium - obtained by laser ablation on the surface of fused silica are studied. Extinction and absorption spectra of quartz, substrates with deposited films, as well as difference spectra are obtained. The minimum values ​​of the effective thicknesses of metal films at which the nucleation of islands begins and localized plasmon resonances appear. It is shown that the absorption of the "quartz substrate-metal film" complex exceeds the sum of the absorptions by the quartz surface and by the metal atoms. The connection of this phenomenon with the transfer of charge from the metal to defects on the substrate surface is indicated.