Session Chair: Boris Lukiyanchuk, Data Storage Institute, Agency for Science, Technology and Research (A*STAR) Session Chair: Arseniy Kuznetsov, Data Storage Institute, Agency for Science, Technology and Research (A*STAR)
1:30pm - 2:00pm Invited
Nanophotonics with Resonant Dielectric Nanostructures: Resonances Matter
Data Storage Institute, Agency for Science, Technology and Research (A*STAR), Singapore
Resonant dielectric nanostructures recently emerged as a new promising direction in nanophotonics. Due to their low-loss resonant behavior, broad range of appropriate materials and strong magnetic response, they open many new avenues for potential applications, which were not available to conventional plasmonics before . In this talk, I will review recent progress of our team in this field, with particular emphasis on new applications resulted from interference effects between electric and magnetic dipole resonances in dielectric nanoantennas. In particular I will show how resonance interference in asymmetric nanoantennas can be used to efficiently control power distribution between different diffraction orders of the nanoantenna array. This allowed us to achieve efficient light bending at angles >80 degrees, which was further used to design and realize experimentally a lens with record-high numerical aperture of >0.99, the value not accessible before not only to flat optics but also to conventional bulk optics. Then I will describe different new non-silicon material platforms for dielectric nanoantennas based on titanium dioxide and III-V semiconductor materials, such as GaAs and GaN. These new materials allowed us to achieve unique functionalities such as multi-layer metasurfaces working simultaneously at all three RGB wavelengths and also light-emitting nanoantennas and metasurfaces, which can be transformed to directional on-chip lasers.
1) A. I. Kuznetsov et al., “Optically resonant dielectric nanostructures”, Science 354, aag2472 (2016).
2:00pm - 2:30pm Invited
Widely Tunable Semiconductor Antennas for Reconfigurable Metasurfaces
University of California, Santa Barbara, United States
The ability to engineer the optical phase at subwavelength dimensions has led to metasurfaces that provide unprecedented control of electromagnetic waves. To reach their ultimate potential, metasurfaces must incorporate reconfigurable functions. The central challenge is achieving large tunability in subwavelength elements. Here, we describe two different approaches for achieving order-unity refractive index shifts: free-carrier refraction1and thermo-optic tuning. We experimentally demonstrate wide tuning of single-particle infrared Mie resonances through doping, and demonstrate simulations of electrically reconfigurable III-V heterojunction metasurfaces based on these effects. We conclude with recent experimental demonstrations of dyamic, ultrawide tuning of Mie resonators based on two distinct thermo-optic effects: 1) modifying the electron mass and carrier density in InSb and 2) exploiting the anomalous temperature-dependent bandgap of PbTe.
2:30pm - 3:00pm Invited
Advanced Topics In Dielectric Metasurfaces: Tunability and Novel Fabrication
Uriel LEVY, Jonathan BAR DAVID, Liron STERN, Noa MAZURSKI
Hebrew University of Jerusalem, Israel
In recent years dielectric and metallic nanoscale metasurfaces are attracting growing attention and are being used for variety of applications. Resulting from the ability to introduce abrupt changes in optical properties at nano-scale dimensions, metasurfaces enable unprecedented control over light's different degrees of freedom, in an essentially two-dimensional configuration. Yet, the dynamic control over metasurface properties still remains one of the ultimate goals of this field. Here, we demonstrate the optical resonant interaction between a dielectric metasurface made of silicon form birefringence nanostructures and alkali atomic vapor, to control and effectively tune the optical transmission pattern initially generated by the nanoscale dielectric metasurface. By doing so, we present a controllable metasurface system, the output of which may be altered by applying magnetic fields, changing input polarization or shifting the optical frequency. Furthermore, we also demonstrate the nonlinear behavior of our system taking advantage of the saturation effect of atomic transition. Finally, we also demonstrate novel fabrication techniques for dielectric metasurfaces, with the capability of post processing and planarization towards multi-layer device. The demonstrated approach paves the way for using metasurfaces in applications where dynamic tunability of the metasurface is in need, e.g. for scanning systems, tunable focusing, real time displays and more.
3:00pm - 3:30pm Invited
Dynamic Control of Heat and Light Flow in Active Metasurfaces
Harry A. ATWATER
California Institute of Technology, United States
Resonant subwavelength optical structures have fueled a worldwide explosion of interest in fundamental nanophotonic processes and devices for imaging, sensing, solar energy conversion and thermal radiation control. However in most cases, the optical properties have been fixed at the time of fabrication. Now, actively-tunable permittivity nanoscale materials are bringing metasurfaces to life as dynamic objects composed of tunable antenna arrays. Electrical tuning of the carrier density in conducting oxides, transition metal nitrides and two-dimensional materials enables the optical dispersion of individual structures to be altered from dielectric to plasmonic, yielding active antenna arrays with gate-tunable phase and amplitude modulation of absorption, radiative emission and scattering. Operation of antenna array-based modulators and detectors as well as beam steering phased arrays will be discussed.