The road to atomically thin metasurface optics

Mark L Brongersma

doi:10.1515/nanoph-2020-0444

Abstract

AbstractThe development of flat optics has taken the world by storm. The initial mission was to try and replace conventional optical elements by thinner, lightweight equivalents. However, while developing this technology and learning about its strengths and limitations, researchers have identified a myriad of exciting new opportunities. It is therefore a great moment to explore where flat optics can really make a difference and what materials and building blocks are needed to make further progress. Building on its strengths, flat optics is bound to impact computational imaging, active wavefront manipulation, ultrafast spatiotemporal control of light, quantum communications, thermal emission management, novel display technologies, and sensing. In parallel with the development of flat optics, we have witnessed an incredible progress in the large-area synthesis and physical understanding of atomically thin, two-dimensional (2D) quantum materials. Given that these materials bring a wealth of unique physical properties and feature the same dimensionality as planar optical elements, they appear to have exactly what it takes to develop the next generation of high-performance flat optics.

Highlights

The development of flat optics has taken the world by storm
Given that these materials bring a wealth of unique physical properties and feature the same dimensionality as planar optical elements, they appear to have exactly what it takes to develop the generation of high-performance flat optics
Brongersma: The road to atomically thin metasurface optics wavefront manipulation can be attained by engineering the light transmission through nanoscale holes [13, 14] or engineered gap plasmonic waveguides [15] carved into thin metallic films

Summary

A brief historical perspective of passive metasurfaces

We traditionally control and measure the behavior of light using bulky optical components. In 2001 geometric-phase, flat optical elements entered the scene and provided a fundamentally new way to shape wavefronts by varying the orientation as opposed to the size and shape of subwavelength structures [16,17,18,19] They offer complete 0 to 2π phase control by rotating structures, whose geometry and spacing is optimized to achieve high diffraction efficiencies [20]. This spurred new ideas on Kerker resonators with two degenerate resonances [28, 38] and overcoupled gap plasmon resonators on a reflective substrate [39,40,41] capable of producing phase pickups across a full 2π range Another challenge with antennas is that the light scattering properties (amplitude and phase) are strongly wavelength dependent. This makes it hard to cascade them into multicomponent systems while avoiding ghost images and most likely a blend of flat and conventional optics can provide the highest performance

Metasurfaces in optoelectronic devices

Open challenges and opportunities for metasurfaces

The imminent fusion of 2D metasurface optics and 2D vdW metasurfaces

Conclusions and outlook