Nanostructured Silicon Meta-Waveguides and Surfaces for Enhanced Light-Matter Interaction

Author

Saddam GafsiFollow

Date of Award

12-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical and Computer Engineering (Holcomb Dept. of)

Committee Chair/Advisor

Ryckman D. Judson

Committee Member

Goutam Koley

Committee Member

Lin Zhu

Committee Member

Pingshan Wang

Abstract

In this study, we tackle the challenge of light-matter interaction engineering and local field enhancement using various silicon photonic platforms based on three different approaches. (i) The first approach is based on boundary condition engineering where we present and show through simulation and experimental results, a silicon nanodisk “diabolo” configuration able to support significant local field enhancement levels in the range ~102 to 104 in the high index medium through proper structural modifications at the nanoscale. We show that the presented optical behavior is consistent with the anapole modes characterized by the observed near-field enhancement and coinciding with far-field suppression. In addition to supporting an anapole hot spot, we also identify an anti-diabolo effect with a broadband cold spot where the local enhancement is turned off and suppressed for the orthogonal polarization. (ii) Our second approach is inspired by the diabolo configuration and implements a diamond subwavelength grating on a ring resonator structure in order to combine the high-quality factor levels offered by such whispering gallery mode cavities with the local field enhancement capabilities of the proposed grating. A mode converter and a phase matching structure were specifically designed to minimize losses due to mode mismatch and to ensure good coupling to the ring cavity. We show that the design while keeping a relatively high quality factor in the order of 104, enables successive mode reductions where the mode volume is halved due to the mode splitting effect demonstrated experimentally through double resonant peaks which results in the emergence of two standing waves from a traveling wave as a consequence to degeneracy lifting. Additional mode volume reduction was shown to occur for higher order modes with ii higher capture efficiency levels. (iii) Our third approach consists of combining metasurfaces based on periodic arrangements of silicon nanoparticles with a multilayered porous silicon structure for colorimetric sensing. We demonstrate Fano resonances with various shapes supported by the device and experimentally probe the sensitivity of these resonant modes using various liquid and vapor stimuli. The presented results have shown clear color shifts depending on the exposed material index and the illuminating laser source. The techniques we present in this dissertation are useful engineering tools paving the way to further structural engineering ideas enabling lower mode volumes and higher quality factors and thus better spatiotemporal optical behavior that can be particularly attractive for applications in the fields of sensing, telecommunications and novel quantum technologies.

Recommended Citation

Gafsi, Saddam, "Nanostructured Silicon Meta-Waveguides and Surfaces for Enhanced Light-Matter Interaction" (2024). All Dissertations. 3804.
https://open.clemson.edu/all_dissertations/3804

Author ORCID Identifier

0000-0001-7831-9247