Localization of photons to nanoscale volumes with the aid of plasmonic nanoantennas opened new horizons in bio(chemical) sensing and nanoscale imaging. However, plasmon resonances are short-lived, and the photon energy quickly dissipates as heat, creating temperature gradients on plasmonic chips.
While being useful for solar vapor generation, cancer treatment and catalysis, localized heating of plasmonic nanoantennas can be an undesirable effect in other applications such as sensing, imaging, spectroscopy and optical signal processing.
Nanoantennas are often smaller than both the phonon mean free path in the material of the substrate on which they are located and the wavelength of thermal emission. They are also comparable in size to the mean free path distance of the air molecules.
As a result, metal nanoantennas do not cool down the same way bulk materials do, and may get overheated and even melt under laser illumination. Ideal nanoantenna designs should offer significant electric field intensity enhancement, high spatial and spectral selectivity, and control over operating temperature.
In new work, researchers from the Mechanical Engineering Department at Massachusetts Institute of Technology (MIT) have proposed design rules to engineer hybrid optical-thermal antennas that offer multiple functionalities in nanoscale light and heat management.