Exploring Optically Tunable Metasurfaces with a Time-Resolved Terahertz Spectroscopy Technique

Abstract

This thesis will explore the ultrafast modulation and optical tunability of plasmonic filters in the terahertz (THz) spectral region. First, the principles and functional design of THz metasurfaces are explored through plasmonic surface lattice resonance interactions and lumped-element circuit models. We will then describe the methodology of generating and detecting THz radiation through the nonlinear processes of optical rectification and electrooptic sampling, respectively. Next, the implementation of a THz time-domain spectroscopy technique is discussed in the context of pump-probe measurements and time-domain resonance analysis. We then show how THz probed materials can be characterized in terms of a temporal and spectral analysis. We will demonstrate how this time-domain technique can allow us to characterize the interaction of plasmonic resonators with optically active substrates and 2D nanomaterials. A completely tunable THz plasmonic notch resonance is modulated utilizing a static and dynamic method of optical tunability in silicon. Active tunability is also demonstrated in a graphene-based plasmonic resonator through the hot carrier multiplication effect. The significance of this work lies in the application of designing controllable devices for future THz communication technologies.