OP: Development of Quantum Well-Based Metasurfaces for Active Wavefront Control

Vanderbilt University, Nashville TN

Investigators

Abstract

Nontechnical Description: Optical metasurfaces are artificially structured thin films in which patterning of the materials is used to engineer the optical properties of the medium. Traditionally, metasurfaces have been formed from materials such as metal and insulators, allowing the creation, for example, of ultra-thin optical filters and lenses. This project focuses on investigating and developing actively tunable optical metasurfaces that can be used for a variety of applications, ranging from fast light modulation to ultra-thin zoom lenses. This is accomplished by replacing metals, with which metasurfaces are typically fabricated, with semiconductor structures whose optical properties can be tuned using voltage. A broad range of training opportunities, encompassing computer modeling, fabrication, and optical characterization of semiconductor metasurfaces are available to the participating graduate and undergraduate students. The principal investigator is also leading lectures and demonstrations at the Nashville Adventure Science Center for K-8 students. These demonstrations serve to introduce a general audience to nanoscale science and engineering, as well as to optics concepts. Technical Description: The recent development of metasurfaces has provided researchers a new means to achieve control over the phase and polarization of light, leading to ultrathin waveplates, lenses, and complex phase arrays. A critical step towards the practical use of these surfaces is achieving active control over their optical properties as this would allow them to be employed for applications such as modulation, active wavefront control, and holographic displays. The research objective of this project is to realize active metasurfaces at infrared frequencies that have on-demand optical properties. This is being achieved by forming all-dielectric metasurfaces directly from III-V semiconductor multi-quantum well heterostructures and then utilizing electrical control of the intersubband transition frequency in the quantum wells to actively tune the resonator elements. All-dielectric metamaterials are ideal for this purpose as they possess bulk optical resonances in which one can utilize modes, such as the magnetic dipole mode, that have strong out-of-plane oriented electric fields. These modes are being investigated to realize amplitude-, polarization-, and phase-modulation, culminating in the development of metasurfaces that serve as spatial light modulators for arbitrary beam forming.