Metasurfaces for Spatio-temporal Light Modulation

For a lay audience, an optical modulator might be the most important invention they have never heard of. Temporal modulation, where the properties of the beam change rapidly in time is fundamental for encoding and conveying information, i.e. the internet. A second modulation style is spatial light modulation, where the spatial distribution of a beam is modified. This form of modulation is less common in consumer products, but will be a fundamental workhorse of future systems, e.g. holographic displays for augmented reality or scanning of optical beams for remote sensing, such as an autonomous vehicle scanning the path ahead.
To date, no device or platform can provide both forms of modulation. Optical modulators are either fast, but limited to a single optical channel (even though this channel might carry multiple signal channels, through clever encoding schemes) or can feature high spatial resolution, but are 'slow', i.e. in the Hz-kHz regime.
In this proposal, we present a new class of optical modulators - the spatio-temporal light modulator, a single platform that can provide both spatial and temporal modulation. To this end, our project will address three key proof-of-principle demonstrations. First, we will demonstrate the fundamental platform, high-efficiency metasurfaces incorporating epsilon-near-zero materials. This is a system consisting of an array of antennas, coupled with a transparent conductive oxide, the epsilon-near-zero material. By dynamically tuning the properties of the transparent conductive oxide, we modify the optical response of the system, providing us with a modulation mechanism. We will show that this platform features very high operating efficiency beyond the current state of the art of tunable metasurfaces. Next, we show that this system can act as a spatial light modulator, by creating a pixel array in our metasurfaces. And last but most definitely not least we will show temporal modulation in our metasurfaces platform, reaching GHz speeds.
Each of these demonstrations alone would be a step-change in technology, yet we aim to unlock all three, through the innovative metasurfaces design presented and the recent advances in the understanding of epsilon-near-zero materials.