Localized Light-Matter Interactions with Optical Antennas

Abstract

Standard far-field optical elements, such as lenses and mirrors, are only capable of localizing radiation to about half-a-wavelength-the Abbe criterion. Optical antennas facilitate the further localization of radiation into arbitrarily small spatial volumes. Combining the optical antenna with traditional optical microscopy, a technique termed near-field scanning optical microscopy (NSOM), has enabled the study of biological and solid-state samples at high spatial resolution. Since the development of NSOM in the 1980s, the biggest challenge to researchers has been the design and fabrication of optical antennas functioning as optical nearfield probes. We have recently made much progress in the development of widely applicable, and reproducible, optical antennas that provide a high degree of spatial localization. Beyond NSOM, we also explore the electrical excitation, as opposed to photo excitation, of optical antennas with a scanning tunneling microscope (STM). We demonstrate a two-step plasmon-mediated energy conversion from a tunneling current to propagating photons in a smooth gold film as well an extended gold nanowire. We prove that highly localized gap plasmons are first excited in the tunnel gap, which can then couple to propagating plasmons. We elaborate on the role of gap plasmons in explaining the huge variations seen in photon emission yields in the field of STM light emission.

Spontaneous Emission Enhancement in Strain-Induced WSe2 Monolayer-Based Quantum Light Sources on Metallic Surfaces

“…Enhancement of photoluminescence (PL) has also been observed from atomic monolayer materials on metallic layers. − Metallic substrates have the advantage of reflecting almost all of the photons toward the collecting objective, while the transmission or absorption of single photons inside the substrate is the main source of loss of the single photons. In addition, metallic nanoparticles on a metal surface act as native antennas, ,− , which in principle allow to engineer the spontaneous emission rates of surface-near quantum emitters. − ,− …”