Metastructures

By tailoring the morphology, complex dielectric structure, and electronic properties of matter at the nanoscale, we can sculpt the flow of light and thermal radiation at wavelength-scale subwavelength dimensions, a subject both of scientific interest and with broad applications, enabling unprecedented control for communications, sensing and light-energy conversion to electricity and fuels. The A-team is interested and engaged in research exploring fundamental nanoscale optical phenomena in new materials, nanostructures and hybrid states of light and matter such as plasmons, excitons and phonon polaritons. We are also exploring applications of nanophotonics such as active metasurfaces for optical communications and wavefront control, coherent single photon generation for quantum optical applications, hot carrier dynamics and conversion of light to chemical fuels, as well as novel photonic approaches to control thermal radiation.

Active Metasurfaces in Space and Time

Metasurfaces are composed of two-dimensional (2D) arrays of subwavelength resonant scatterers, which locally and abruptly change the characteristic properties of the impinging light, i.e., its amplitude, phase, polarization, spectrum, and momentum. This also results in control of the far-field properties of light, giving rise to anomalous reflection, polarization control, or beam focusing, which result from constructive interference of the waves that are scattered collectively by the entire array.

Active metasurfaces have emerged as a reconfigurable nanophotonic platform for the manipulation of light. Application of an external stimulus to resonant subwavelength scatterers enables dynamic control over the wavefront of reflected or transmitted light. Active metasurfaces can control key characteristic properties of an electromagnetic wave, such as its amplitude, phase, polarization, spectrum, and momentum, in a dynamically reconfigurable manner, for deterministic wavefront shaping. We are researching approaches for high performance active metasurfaces, and exploring pathways for two-dimensional control architectures, for optical imaging, communication, and computation applications based on a universal active metasurface.

2D and Layered Materials

2D van der Waals materials, made by stacking thin sheets of semimetals, semiconductors, or insulators, have attracted wide interest due to their unique properties. Their thin layers interact strongly with light through various material resonances related to their quantum-confined states, spanning from ultraviolet to mid-infrared wavelengths. These resonances can be tuned by external factors such as electric fields and strain. This has led to exploring fundamental optical phenomena and also the potential of creating dynamic metasurfaces from van der Waals materials. Notably, 2D semiconductors like monolayer transition metal dichalcogenides (TMDCs) and black phosphorus offer advanced light-field control and support exciton resonances at room temperature, thanks to their high binding energy and reduced screening. Their strong excitonic resonances enable efficient light manipulation and near-unity reflection at low temperatures. We are exploring excitonic and polaritonic these materials and other layered semiconductors such as NiPS3 that exhibit coupling of excitons to magnetic order.