November 16, 2021
High-Q metasurfaces: enhancing light-matter interactions with slow light
Densely interconnected, nonlinear, and reconfigurable optical networks will be critical for future high-performance classical and quantum computing, communications, and sensing technologies. Metasurfaces present a promising platform for the compact manipulation of light, but are generally limited by the low-quality factor (Q-factor) of their resonances and accordingly weak light-matter interactions. Here, I describe the creation of high-Q metasurfaces that not only strongly amplify light in the near-field, but also maintain complete control of the far-field scattered wavefront. I also describe how these metasurfaces can be used to design nanoscale optical isolators and solid-state electro-optical beam-steering.
Our approach relies on subtle structural perturbations that couple free-space light to Guided-Mode-Resonances (GMR) and quasi-Bound in the Continuum (q-BIC) photonic states. Experimentally, we demonstrate Q-factors exceeding 14,000, which enables high fidelity nanophotonic sensing, controllable wavefront shaping, and compact nonlinear optics. I highlight this scheme’s general applicability by designing and fabricating high-Q metasurfaces that act as beam-steerers to different angles, beam splitters, and lenses. Next, we show how high-Q metasurfaces can be integrated with electro-optic materials for low-power metasurface modulation. Here, an array of uniform lithium niobate-on-Si antennas is individually addressed with an electrical bias, leading to a full 2-pi phase variation. We show how near-continuous beam-steering can be achieved by modifying the bias across each antenna, towards fully reconfigurable, solid-state wavefront shaping. Finally, I describe the design of an all-optical nanoscale isolator. We demonstrate a doubly-resonant high-Q metasurface to enhance Stimulated Raman Scattering, which when pumped with circularly polarized light, gives rise to nonlinear spin-selection rules that break Lorentz reciprocity. This process enables nonreciprocal gain for a signal at the Stokes frequency and results in one-way, nonreciprocal Raman amplification in a subwavelength (230nm thick) device layer, en route to a nanoscale self-isolated laser. With these high-Q metasurfaces, new paradigms in reconfigurable wavefront-shaping, multiplexed biosensors, enhanced emission, and quantum transduction are possible.
Our approach relies on subtle structural perturbations that couple free-space light to Guided-Mode-Resonances (GMR) and quasi-Bound in the Continuum (q-BIC) photonic states. Experimentally, we demonstrate Q-factors exceeding 14,000, which enables high fidelity nanophotonic sensing, controllable wavefront shaping, and compact nonlinear optics. I highlight this scheme’s general applicability by designing and fabricating high-Q metasurfaces that act as beam-steerers to different angles, beam splitters, and lenses. Next, we show how high-Q metasurfaces can be integrated with electro-optic materials for low-power metasurface modulation. Here, an array of uniform lithium niobate-on-Si antennas is individually addressed with an electrical bias, leading to a full 2-pi phase variation. We show how near-continuous beam-steering can be achieved by modifying the bias across each antenna, towards fully reconfigurable, solid-state wavefront shaping. Finally, I describe the design of an all-optical nanoscale isolator. We demonstrate a doubly-resonant high-Q metasurface to enhance Stimulated Raman Scattering, which when pumped with circularly polarized light, gives rise to nonlinear spin-selection rules that break Lorentz reciprocity. This process enables nonreciprocal gain for a signal at the Stokes frequency and results in one-way, nonreciprocal Raman amplification in a subwavelength (230nm thick) device layer, en route to a nanoscale self-isolated laser. With these high-Q metasurfaces, new paradigms in reconfigurable wavefront-shaping, multiplexed biosensors, enhanced emission, and quantum transduction are possible.
Jefferson Dixon is a doctoral candidate in Mechanical Engineering at Stanford University, where he studies nanophotonics under Prof. Jennifer Dionne in the Department of Materials Science and Engineering. His focus is on high-Q metasurfaces, especially for nonlinear optics that will transform the way we transmit, detect, and process classical and quantum information. Outside of science and engineering, Jefferson enjoys performing as a violinist with Stanford Symphony Orchestra and exploring music throughout the Bay Area. Prior to Stanford, he received a BS in Mechanical Engineering from Georgia Tech. Jefferson is funded by the generous support of the Eastman Kodak Graduate Fellowship.