Intrinsic and Extrinsic Nonlinearities in Epsilon-Near-Zero

Optical materials with a refractive index, and permittivity, that tend towards zero provide quite fascinating optical responses. From emission tailoring and perfect absorption to ‘DC-light’ and optical tunneling, epsilon-near-zero (ENZ) and near-zero-index (NZI) materials have provided new and interesting methods of manipulating light in a linear fashion. Perhaps to no surprise, the nonlinear properties of these materials are also quite intriguing, having recently been utilized to realize unity-order refractive index tuning, enhanced harmonic generation, and spatio-temporal control over light flow in sub-micron layers. In this talk, we will summarize the origins of the nonlinearities in homogeneous ENZ and NZI materials, focusing on the intrinsic and extrinsic factors on the response. Through this lens we will highlight avenues where such materials are less suited, where they provide unique advantages, and discuss techniques to push these advantages. We will overview our recent experimental works combining high-Q metastructures with ENZ materials as well as dual-pump tailoring of the index and loss profiles. Through this will aim to illustrate the unique benefits of ENZ materials for numerous nonlinear optical applications.