Dissertations, Theses, and Capstone Projects

Date of Degree

9-2023

Document Type

Dissertation

Degree Name

Ph.D.

Program

Physics

Advisor

Euclides Almeida

Committee Members

Timothy Benseman

Gabriele Grosso

Matthew Sfeir

Vinod Menon

Subject Categories

Nanoscience and Nanotechnology | Optics | Physics

Keywords

Optics, Mid-infrared, Four-Wave Mixing, Experiment

Abstract

Optical Metasurfaces are planar structures that are patterned with subwavelength structures and are very thin compared to the wavelength of light. Despite their thinness, these structured materials can strongly interact with incident light to effect the functionalities of conventional optical components, such as rotation of the polarization state, beam steering, lensing, spectral filtering, and holography, to name a few. Metasurfaces can also facilitate nonlinear optical effects, such as the mixing of beams at different frequencies to generate a beam at a new frequency.

The ability to alter the behavior of a metasurface during operation is highly desired for applications such as computing and sensing, and has been approached in many ways, depending on the spectral range of interest. Graphene holds promise for mid-infrared applications, a region that contains the spectral signatures of many molecules due to their vibrational modes, as well as some atmospheric spectral windows which could prove useful for long-range communications. Graphene’s optical properties are tunable through the application of a voltage and has been demonstrated to have fast electro-optic switching capability (10s of GHz) with the right environment.

In this dissertation, I present work utilizing graphene with patterned gold nanostructures that form a coupled plasmonic system, and which can tune the transmitted light with a modulation of up to 17% at 11.5 m, a region which lies within an atmospheric window. In addition, this system is shown to enable a nonlinear four-wave mixing process that can be electrically turned on and off over a broad range of mid-infrared inputs, with a modulation of the nonlinear output up to 8 times stronger when switched on compared to the “off” state. In principle, the design can be extended to locally shape the wavefront at a subwavelength scale to enable applications such as lensing and holography, both in linear and non-linear operations. This work represents a step towards tunable optical components for the mid-infrared.

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