January 26, 2017
Natalia M. Litchinitser
University at Buffalo, The State University of New York
Professor of Electrical Engineering
“Nonlinear and Singular Optics in Photonic Meta-Structures”
4:00 PM, 4327 Stevenson Center
Refreshments served at 3:30 PM in 6333 Stevenson Center
Abstract
The emergence of synthetic photonic media, or metamaterials, has revealed many unique electromagnetic phenomena, including negative index of refraction, which has never been found in nature, magnetism at optical frequencies, backward propagating waves with antiparallel phase and energy velocities and extreme field enhancement effects giving rise to entirely new regimes of nonlinear optical interactions. In a context of nonlinear optics, the emergence of these novel photonic media necessitates a reconsideration of many, if not all, fundamental processes, including second harmonic generation, soliton propagation, four-wave mixing, modulation instability, and optical bistability to name a few.
These recent developments in the field of nanostructured optical materials enable unprecedented control over light propagation and a possibility of “tailoring” the space for light propagation. In particular, the emergence of novel optical materials opens a new paradigm in studies of singular optics (or structured light), which is a fascinating emerging area of modern optics that considers spin and orbital angular momentum (OAM) properties of light and brings a new dimension to optical physics. We will discuss fundamental optical phenomena at the interface of singular and nonlinear optics in novel optical media and show that the unique optical properties of optical nanostructures open unlimited prospects to “tailor” light itself.
We present theoretical and experimental studies of light-matter interactions of vector and singular optical beams in optical nanostructures and microcavities. For example, by exploiting the emerging non-Hermitian photonics design at an exceptional point, we demonstrate a microring laser generating a single-mode OAM vortex lasing with the ability to precisely define the topological charge of the OAM mode. We show that the polarization associated with OAM lasing can be further manipulated on demand, creating a radially polarized vortex emission. Such OAM microlaser could find applications in the next generation of integrated optoelectronic devices for optical communications in both quantum and classical regimes.
Next, we will discuss linear and nonlinear light-matter interactions in so-called, transition metamaterials, a class of artificial graded-index materials with dielectric permittivity and magnetic permeability gradually changing from positive to negative values. Light propagation in such structures is of great interest from both fundamental science and practical viewpoints owing, in particular, to the prediction of the strong field enhancement near the zero refractive index point under oblique incidence of the electromagnetic wave. Such resonant enhancement is likely to enable a variety of applications in microwave, terahertz, and optical spectral ranges, including low-intensity nonlinear optical devices. Until recently, most of the studies of these structures were limited to the linear wave propagation. However, strong and localized field enhancement near the transition point(s) results in enhancement and entirely new regimes of electromagnetic wave mixing with reduced input intensities, thus creating a new paradigm for nonlinear optics. In particular, we show that resonant field enhancement of obliquely incident light in a quadratically nonlinear metamaterial with refractive index gradually changing from positive to negative values enables efficient second harmonic generation at significantly reduced input intensities.