Knowledge of temperatures at the nanoscale is essential for studying and controlling the heat-induced local thermal responses. The temperature rise of a heated nanoparticle (NP) near the interface of two kinds of media with different thermal conductivities is numerically investigated. We find that the temperature rise becomes size independent if it is scaled by the temperature rise in the case where the particle-interface distance is zero and the distance is scaled by the equivalent radius of the NP. This universal scaling behavior can be understood with the principle of dimensional homogeneity. An empirical equation is retrieved to predict the actual particle temperature at a given position. Our results may benefit precise control of heat at the nanoscale with applications in plasmonic absorbers, immunotargeted photothermal cancer cell killing, etc.
We propose a tunable unidirectional long-range surface plasmon polaritons (LRSPP) launcher based on subwavelength metallic nanoslits in the visible range. The direction of the generated LRSPPs could be tuned simply by varying the incident angles. The extinction ratio reaches up to 28 dB with a wide angular width of 30º. The influences of the launcher geometry on its performance are investigated in this study as well. The broadband property of the launcher is also demonstrated.
Absorption properties of film-coupled log-periodic optical antennas in the near-infrared region are numerically investigated. The maximum absorption for TE and TM polarizations at normal incidence reach to 95% and 93%, respectively, and the optimal absorption of around 90% can be simultaneously obtained for both cases. It is shown that the main absorption peak is independent to light polarizations at normal incidence. Moreover, the log-periodic antenna-assisted absorption represents district polarization selectivity at high-order resonances. For oblique incidence, only the incident light of specific wavelengths within a narrow incidence angle can be almost entirely trapped inside the absorber, indicating special direction and wavelength selectivity of the absorber. All these features would lead to potential applications in photovoltaic technology, sensing, etc.