In metal nanoparticles (NP), localized surface plasmon resonances induce enhanced light absorption and scattering. In ohmic metals, however, this charge oscillation induces Joule heating. The study of temperature generated by plasmonic nanostructures is an emerging field with promising applications in photothermal therapeutics or imaging1,2. The optical properties of these NP strongly depend on the morphology of the nanostructure and its dielectric environment, allowing a control of their optical and thermal properties at the nanoscale. Here, we aim at modelling, characterizing and optimizing the thermal properties of metallic nanostructures.
Simple geometries such as ellipsoids and disks have been investigated. For any NP shape, FDTD and FEM models were used to determine the influence of NP morphology on the steady-state temperature inside a nano-object immersed in a homogeneous medium. We will present numerical optimizations of the thermal properties of these structures, showing a maximum in the achievable temperature.
The corresponding gold nanostructures have been fabricated by 20 nm-resolution e-beam lithography. The heat generation in these nanostructures was probed by photothermal digital heterodyne holography3. In the presence of kHz-modulated heating, the refractive index is modified, inducing a modulation of the scattering, detected by interference with a reference wave on a CCD camera. Quantitative temperature measurements obtained on an array of nano-ellipsoids of varying size and aspect ratios are compared to opto-thermal modelling.
 A. Lalisse, et al. Scientific Reports (2016)
 A. Lalisse, et al. J. Phys. Chem. C (2015)
 E. Absil, et al. Optics Express (2010).
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