Tunable free-space optics via phase change materials

Shaping an optical wavefront with sub-wavelength spatial resolution is important for various applications with far-reaching scientific and technological impacts (e.g., in adaptive optics and imaging through turbid, disordered media) and commercial interest (e.g., LIDAR for autonomous transportation and pixelated holography). The primary enabling technology for such capability is a compact optical phase shifter, which can change the phase of the incident light by a full 360 degree with low energy and high frequency (~MHz). Existing tunable optical technologies cannot provide this functionality; mechanically tunable modulators can reach a speed of only a few kHz, while liquid-crystal based modulators operate at 100's of Hz. The pixel size of the spatial light modulator is also on the order of tens of wavelengths, which increases the energy consumption per pixel. In this talk, I will discuss our effort to tune meta-optics using chalcogenide based non-volatile phase-change materials. Using wide bandgap phase change materials, we reported a transmissive tunable metasurface, and also reported independent tuning of ~14 meta-atoms.