Metasurfaces are arrays of subwavelength anisotropic light scatters (optical antennas) that can produce abrupt changes in the phase, amplitude, or polarization of light. Within last few years significant progress, design of metasurfaces that refract and focus light, enabling many unique properties and applications such as holograms, optical vortex generation/detection, ultrathin focusing lens, perfect absorber, etc. 

This tutorial will cover the fundamental principles, advanced designs and technological applications of optical metasurfaces, particularly focusing on the topics of (I) Optimization and Machine Learning for Metasurface Design, (II) Metastructures for Advanced Optical Applications, (III) Metasurfaces, then-and-now, and (IV) Tunable Optical Metasurfaces: Progresses and Prospective Applications.

Optimization and Machine Learning for Metasurface Design
Jonathan Albert Fan, Stanford University

Inverse design, in which the design process is performed through iterative optimization, has the potential to push metasurface performance to the physical limits of composite materials engineering.  In this tutorial, Fan will discuss a range of state-of-the-art numerical optimization methods for metasurface design.  He will introduce the objective-first and adjoint variables methods, which are gradient-based optimization concepts that can produce high performance freeform geometries.  He will also provide an overview of machine learning techniques as applied to electromagnetics problems and show how generative neural networks can be harnessed as an effective global optimizer for photonic devices.

Metasurfaces—Then and Now
Patrice Genevet, Université Côte d’Azur, CNRS

A class of planar and wavelength-thick optical components exhibiting exceptional optical properties have emerged in recent years. These artificial interfaces, known as metasurfaces, can manipulate the wavefront of light in almost any desired manner, leveraging on the scattering properties of the subwavelength nanostructures. To further develop this technology towards dynamic tuning, broadband applications and industrial production, new materials and new fabrication methods have been proposed.

In this tutorial, Genevet will discuss basic design and fabrication methods of metasurfaces and summarize various applications for beam steering, polarization control and monolithic integration of metasurfaces in opto-electronic systems. As an alternative of conventional bulky, the development of this technology is expected to create a positive disruption in modern optical technologies, in particular in the fields of imaging, holography, 3D dynamic image rendering, AR/VR and LiDAR systems.

Metastructures for Advanced Optical Applications
Arka Majumdar, University of Washington, Seattle

Dielectric metasurfaces are sub-wavelength diffractive optics, which can shape the phase, amplitude and polarization of the incident optical wavefront with high spatial resolution. While theoretically conceived decades ago, the availability of sophisticated nanofabrication techniques and computational techniques have recently rejuvenated this research field. In this tutorial, Majmudar will present the current state of the design and fabrication techniques of different metasurfaces. Going beyond single metasurface, Majmudar will present results with composite metasurfaces as well as tunable metasurfaces. Finally, Majmudar will show how computational post processing techniques coupled with metasurfaces can help create ultra-low-power and low-latency sensors.