Research Interests: Nano-Optics

Resonant light-matter interactions

  • Optical resonances of metallic or dielectric nanostructures interface free-propagating radiations and localized near-fields efficiently. In recent decades, resonant light scattering and absorption have been intensively investigated and employed for various applications, including light emission enhancement, optical sensing, nonlinear optical signal generation, photovoltaics, optomechanics, and metamaterials. Plasmonic resonances of metallic nanostructures manipulate light scattering and absorption extremely beyond the optical diffraction limit. Mie resonances, or termed leaky-mode resonances, allow dielectric optical nanostructures to have compact sizes even less than the wavelength scale. The dielectric nanostructures with low optical losses support both electric and magnetic resonant modes and provide an alternative to their metallic counterparts. In our research group, we aim to understand resonant light-matter (photon-electron, photon-phonon, photon-spin, and so on) interactions based on optical nanostructures, and engineer their properties for future applications.

Precision nano-optical measurement

  • We aim to develop precise and quantitative measurement methods for physical understanding of nano-optical phenomena from the evanescent near-field to the radiating near-field (Fresnel) and the far-field (Fraunhofer) regime. For example, we demonstrated for the first time quantitative measurement of the differential far-field scattering cross-section of a single nanostructure over the full hemisphere. Currently, we are expanding the scope of our research to time- and space-resolved measurements of light absorption, photocurrent generation, optical nonlinearity, and optical angular momentum. Our research will provide a new way for investigating the physical properties and performance of a variety of nano-optical materials, phenomena, and devices in energy- (wavelength) momentum (wave vector) space.

Plasmonic sub-wavelength-scale optoelectronics

  • Surface plasmon polaritons (SPPs) are collective electron oscillations interacting with the electromagnetic field of the light at a metal-dielectric interface. SPPs enable us to exploit the unique optical properties of metallic nanostructures to route and manipulate lights at the sub-wavelength scale beyond the diffraction limit. We are investigating the fundamentals and applications of the light-matter interaction in sub-wavelength plasmonic structures for compact, high-speed and power-efficient light emitters, modulators, and sensors. Passive and active plasmonic devices provide new pathways to generate, guide, modulate and detect light with structures that are similar in size to state-of-the-art electronic devices. Electrically activated plasmonics will become a pervasive technology, naturally interfacing with similar-speed photonic devices and with similar-size electronic components. We also focus on the optical antenna defined as “a device designed to efficiently convert free-propagating optical radiation to localized energy, and vice versa.” To maximize the interactions of light and materials, it is necessary to concentrate external light incidence to dimensions comparable with the electron mean free path that is at least an order of magnitude smaller than the diffraction limit. Optical antennas will likely be used to increase spatial resolution in near-field microscopy and boost the efficiency and quantum yield in various nano-photonic phenomena.