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We have demonstrated experimentally that firing a laser filament in a subsaturated zone of a cloud chamber of inversed temperature profile could induce water condensation. Initially, through ion chromatography performed on samples collected from a receptacle placed under the laser, the presence of HNO 3 was observed. The existence of this HNO 3 , as well as digital camera images of very tiny droplets close to the laser axis viewed at an angle perpendicular to the chamber, suggest that the condensation could be due to the laser. A second experiment measuring the growth of the water droplets using a cooled receptacle confirmed the existence of laser-induced condensation in these conditions.

The field known as plasmonics has seen a tremendous growth in interest from the research community. One of the more popular topics is the surface plasmon waveguide. As an alternative to solid linear nanostructures, a chain of plasmonic nanoparticles can also be used to propagate a traveling wave of surface charges. Experimentally, plasmonic nanoparticles lend themselves well to the fabrication of plasmonic waveguides via the self-assembly of nanoparticles into linear structures with very small inter-particle separation. In the present work, we used wrinkled PDMS stamps to fabricate large (i.e., several microns in length) one-dimensional nanoparticle assemblies. Combining this technique with the use of tunable, metaldielectric, core-shell nanoparticles [1] allows the fabrication of linear assemblies with adjustable inter-particle separation. The observation of isolated nanoparticle assemblies by single particle microscopy/spectroscopy (epifluorescence, dark-field scattering, fluorescence lifetime microscopy) and scanning electron microscopy allows us to gather optical and structural information in order to derive interesting structure-properties correlations -in particular the interaction between propagating dark plasmons with the emission behavior from nearly fluorophores.

Evanescent field excitation is a powerful means to achieve a high surface-to-bulk signal ratio for bioimaging and sensing applications. However, standard evanescent wave techniques such as TIRF and SNOM require complex microscopy setups. Additionally, the precise positioning of the source relative to the analytes of interest is required, as the evanescent wave is critically distance-dependent. In this work, we present a detailed investigation of evanescent field excitation of near-surface waveguides written using femtosecond laser in glass. We studied the waveguide-to-surface distance and refractive index change to attain a high coupling efficiency between evanescent waves and organic fluorophores. First, our study demonstrated a reduction in sensing efficiency for waveguides written at their minimum distance to the surface without ablation as the refractive index contrast of the waveguide increased. While this result was anticipated, it had not been previously demonstrated in the literature. Moreover, we found that fluorescence excitation by waveguides can be enhanced using plasmonic silver nanoparticles. The nanoparticles were also organized in linear assemblies, perpendicular to the waveguide, with a wrinkled PDMS stamp technique, which resulted in an excitation enhancement of over 20 times compared to the setup without nanoparticles.