Dissertation Defense

Dynamic Control of Waves with Reconfigurable, Time and Space-Time Modulated Metasurfaces

Zhanni Wu
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3316 EECSMap
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Passcode: 217687

Metasurfaces are two-dimensional arrays of closely-spaced, subwavelength scatterers. These surfaces can achieve complete control over the amplitude, phase and polarization state of electromagnetic waves.  Metasurfaces have enabled unprecedented control over electromagnetic waves, providing new opportunities in areas such as wireless communications, energy harvesting, imaging, and cloaking.  Despite significant research activity in this area, most metasurface designs provide static functionalities.

This thesis focuses on integrating electronic components with tunable properties into metasurfaces, to achieve dynamic control over electromagnetic wavefronts. Such control allows the real-time manipulation of electromagnetic waves, and rich electromagnetic phenomena such as frequency conversion, nonlinear and nonreciprocal responses. First we demonstrate tunable advanced field control with varactor-based metasurface.  The designed metasurface can rotate the polarization of a transmitted wavefront. Next, we analyze wave propagation in temporally modulated media, and develop an analogous temporally modulated metasurface that allows Doppler-like frequency translation. Further, we propose a dual-polarized metasurface that provides spatio-temporal control of its reflection phase. The metasurface is capable of demonstrating beam steering, polarization control and frequency conversion of the reflected wavefront.  In addition, the spatial discretization of the metasurface enables unique capabilities such as subharmonic mixing, where Doppler-like frequency translation is demonstrated at integer multiples of the modulation frequency.

Chair: Professor Anthony Grbic