Siim Pikker

Goniometric Setup for Plasmonic Measurements and Characterization of Optical Coatings

Fundamentals of light-induced surface plasmon-polariton waves are considered and implemented on the example of goniometric setup assembled by the authors. The setup was used for investigation of angular dependent light transmittance, reflectance, and fluorescence in dielectric layer containing chromophores. It is explained how optical characteristics of multilayered coatings (thicknesses, refractive indices, and surface roughness) can be deduced from the properties of transmitted and reflected light. Original data about attenuated total internal reflection and plasmon-coupled rare earth fluorescence were obtained. Particularly, angular spectral dispersion and control of Sm3+ fluorescent bands were demonstrated.

Gilded nanoparticles for plasmonically enhanced fluorescence in TiO2:Sm3+ sol-gel films

Silica-gold core-shell nanoparticles were used for plasmonic enhancement of rare earth fluorescence in sol-gel-derived TiO2:Sm3+ films. Local enhancement of Sm3+ fluorescence in the vicinity of separate gilded nanoparticles was revealed by a combination of dark field microscopy and fluorescence spectroscopy techniques. An intensity enhancement of Sm3+ fluorescence varies from 2.5 to 10 times depending on the used direct (visible) or indirect (ultraviolet) excitations. Analysis of fluorescence lifetimes suggests that the locally stronger fluorescence occurs because of higher plasmon-coupled direct absorption of exciting light by the Sm3+ ions or due to plasmon-assisted non-radiative energy transfer from the excitons of TiO2 host to the rare earth ions.PACS78; 78.67.-n; 78.67.Bf

Sensitizing of Sm3+ fluorescence by silver dopant in the TiO2 films

Composite material based on a TiO2 matrix doped with Sm3+ ions and co-doped with silver was investigated. Samarium ions together with nano- and micro-aggregates of silver were incorporated into the titanium alkoxide during the sol-gel process. Samarium ions were excited either directly (λexc = 488 nm) or through the TiO2 host (λexc = 355 nm). It was revealed that samarium fluorescence (λexc = 488 nm) in gelled TiO2 films is enhanced by up to 20 times in the vicinity of silver inclusions. Sensitizing and plasmonic mechanisms of enhancement in Sm3+ fluorescence are discussed.

Fluorescence of TiO2:Sm3+ composite stimulated by plasmon waves

Plasmon-coupled fluorescence of rare earth Sm3+ ions doped into the TiO2 film placed on thin gold layer is investigated. It was demonstrated that plasmon waves induced in the gold layer strongly influence rare earth emission. We revealed that each spectral peak of Sm3+ emission can be directionally separated, polarized and enhanced by intensity due to coupling with plasmon waves propagating in the gold film. It is noticeable that we obtained about 10 % of non-linear growth in Sm3+ emission intensity over the pumping strength.