Optics in Wonderland: Down the rabbit hole of metaresonators

Optical resonators allow the generation and storage of electromagnetic waves. They are widely used in technology and fundamental research, notably for their application in telecommunications, lasers and nonlinear optics, ultra-sensitive measurements in cavity optomechanics and the study of light-matter interactions. To some extent, it is possible to create structured light, i.e., to customize it by controlling its amplitude, phase, frequency, and polarization, directly inside a resonator, but the typical approaches used since the invention of the laser, such as pump shaping and designing different cavity geometries, are macroscopic and rather limited. In my most recent research, I have explored new cavity configurations incorporating metamaterials with structured elements smaller than the wavelength of light, allowing light to be shaped in unprecedented ways. These demonstrations range from embedding a mode converter inside a solid-state resonator to create tunable optical vortex arrays, to the use of mode converters as one or both cavity reflectors in external cavity lasers and silicon-on-insulator waveguides to enable lasing on holograms and create arbitrary near fields, to the monolithic integration into semiconductor lasers to engineer the spectrum of optical frequency combs. In all these cases, internal mode conversion confers intriguing new properties to these metaresonators, which cannot be derived from the properties of the base materials constituting the gain or waveguide medium, nor from the cavity geometry. In this seminar, I will provide an overview of this emerging field combining resonators with customized intracavity optical elements, which is one of the most complex and richest frontiers in optics.

Bio: Marco Piccardo is a Researcher at the Istituto Italiano di Tecnologia in Milan leading a small team within the Vectorial Nano-Imaging research line. He is exploring novel approaches for structured light based on metasurfaces and their integration in active laser resonators. He is also an Associate Researcher at Harvard University, where he did his postdoctoral studies from 2016 to 2020 exploring new electronic and photonic properties of integrated laser frequency combs. He obtained his Ph.D. in Physics in 2016 from Ecole Polytechnique working on the fundamental electronic processes responsible for the efficiency drop of blue light-emitting diodes at high-current operation, such as Anderson localization and Auger recombination. He received his B.Sc. in Physics from Università degli Studi di Torino, and a M.Sc. in Physics from Ecole Normale Superieure and Ecole Polytechnique.