Search

We operate micron-sized CdSe/CdS core–shell quantum dot (QD) clusters deposited onto gold patches as integrated light sources for the excitation of photonic waveguides. The surface plasmon mode launched by the QD fluorescence at the top interface of the gold patches are efficiently coupled to photonic modes sustained by titanium dioxide ridge waveguides. We show that, despite a large effective index difference, the plasmonic and the photonic modes can couple with a very high efficiency provided the vertical offset between the two kinds of waveguides is carefully controlled. Based on the effective index contrast of the plasmonic and the photonic modes, we engineer in-plane integrated hybrid lenses. The hybrid lenses are obtained by shaping the contact interface between the plasmonic and the photonic waveguides. We demonstrate a 2-fold enhancement of the coupling efficiency for tapers equipped with a hybrid lens. Our results are expected to be useful for the development of low-cost, integrated light sources...

The Raman intensity fluctuations are the initial source of a lack of accuracy or reproducibility of SERS based nanosensors to reliably estimate the molecular concentration in microfluidics. Here, we show that the statistical analysis of the weighting of Raman scattering of the probed molecules compared to the photoluminescence of gold nanoparticles is particularly effective as a concentration indicator in a single molecule regime. We present a novel approach in the Fourier domain that is not limited by a multipoint precalibration or even the knowledge of the enhancement factor of the transducer. The analysis of pink noise in the frequency domain reveals a subdiffusion motion of individual adsorbed molecules in the hot-spot. The cutoff frequency between the white and pink noise is used to determine the in-line molecular concentration over a wide range between 10–11 and 10–6 M.

In this work, we investigate the generation of second- harmonic light by gold nanorods and demonstrate that the collected nonlinear intensity depends upon a phase interplay between di ff erent modes available in the nanostructure. By recording the backward and forward emitted second-harmonic signals from nanorods with various lengths, we fi nd that the maximum nonlinear signal emitted in the forward and backward directions is not obtained for the same nanorod length. We con fi rm the experimental results with the help of full-wave computations done with a surface integral equation method. These observations are explained by the multipolar nature of the second- harmonic emission, which emphasizes the role played by the relative phase between the second-harmonic modes. Our fi ndings are of particular importance for the design of plasmonic nanostructures with controllable nonlinear emission and nonlinear plasmonic sensors as well as for the coherent control of harmonic generations in plasmonic nanostructures