Title: All-Dielectric Metamaterials and Metasurfaces: Lighting the Way Towards Next-Generation Flat Optics

Speaker: Dr. Parikshit Moitra, IMRE A*STAR, Singapore

Abstract: Optical metamaterials are artificially fabricated array of unit cells or “meta-atoms”, which exhibit novel optical properties. Since their inception, metallic unit cells were commonly used in the design of metamaterials, however, due to high absorption loss of metals at optical frequencies and intricate geometries of the unit cells to induce magnetic resonance, the search for alternative design started. Low-loss, high-dielectric resonators offered unique solutions owing to exhibiting electric and magnetic Mie resonances with simple geometries such as spheres, cubes, rods etc. All-dielectric metamaterials proved to be a low-loss high-efficiency alternative to metal-based metamaterials and offered promises to achieving polarization-independent optical properties with large-area scalability with simple and high-throughput lithography techniques. The transition of “metamaterials” to “metasurfaces” by advanced wavefront shaping with spatial control of amplitude, phase, and polarization of light at sub-wavelength scale opened the door to advanced flat optics. Demonstrations of meta-lenses with high numerical apertures, metasurface based wide-angle holograms, beam steering with wide field-of-views, paved the way towards the use of metasurfaces in next-generation optical devices. However, metasurfaces has so far been limited by their designs, and post-fabrication tunability of their optical response was not possible. To overcome this limitation, recently, there is a major drive to make metasurfaces active, reconfigurable or programmable. A promising approach is to employ a tunable medium, which provides a fast, low energy and volatile or non-volatile means to endow metasurfaces with a switching mechanism. Realization of complete ~2π dynamic phase modulation with high reflection or transmission amplitude, has a promise for them to emerge as an optical component for next generation spatial light modulators (SLMs), augmented and virtual reality (AR, VR) devices, adaptive flat optics, light detection and ranging (LiDAR), dynamic holography, tunable structural colour filters and many more.