Probing and controlling photothermal heat generation in plasmonic nanostructures

Abstract

In the emerging field of thermoplasmonics, Joule heating associated with optically resonant plasmonic structures is exploited to generate nanoscale thermal hotspots. The ability to control thermal processes at the nanoscale level has opened the door for several promising applications in medicine, chemical catalysis, and data storage. In the present study, new methods for designing and thermally probing thermoplasmonic structures are reported. A general design rationale, based on Babinet’s principle, is developed for understanding how the complementary version of ideal electromagnetic antennas can yield efficient nanoscale heat sources with maximized current density. Using this methodology, it is shown that diabolo antenna geometries are more suitable for heat generation compared with their more well-known complementary structure, the bow-tie antenna. A new thermal microscopy method based on the temperature dependent photoluminescence lifetime of thin-film thermographic phosphors is also developed to experimentally characterize the thermal response of various antenna designs. Data from finite-difference time-domain simulations and the experimental temperature measurements are used to confirm the validity of the design rationale. The thermal microscopy technique, with its robust sensing method, could overcome some of the drawbacks of current micro/nanoscale temperature measurement schemes.