Date of Award

1-1-2019

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Nanoscale Science and Engineering

Program

Nanoscale Engineering

Content Description

1 online resource (xxiii, 194 pages) : illustrations (some color)

Dissertation/Thesis Chair

Mengbing Huang

Committee Members

Alain C. Diebold, Hassaram Bakhru, Satyavolu P. Rao, John W. Zeller

Keywords

electro-optic modulators, nonlinear optics, photonics, second harmonic generation, silicon, silver, Second harmonic generation, Nanostructured materials, Nanosilicon, Nanophotonics, Nonlinear optics, Silver

Subject Categories

Materials Science and Engineering | Nanoscience and Nanotechnology | Physics

Abstract

The challenge of current microelectronic architecture in transmission bandwidth and power consumption can be potentially solved by using silicon photonics technologies that are compatible with modern CMOS fabrication. One of the critical active photonic devices for Si photonics is a Si based optical modulator. Most of the reported silicon modulators rely on the free carrier plasma dispersion effect. In those cases, a weak change of the refractive index obtained by carrier accumulation, injection or depletion is utilized in a Mach-Zehnder interferometer or a microring resonator to achieve intensity modulation, rendering them difficult for chip-level implementation due to a large footprint and a high driving voltage. A different approach addressed through this doctoral dissertation explores the area of nonlinear optics (NLO) as an alternative to enable high efficiency modulation. Si has a relatively large third-order nonlinear optical susceptibility, but such third order NLO processes are plagued by high power consumption owing to higher order nonlinearity based two-photon absorption (TPA) and free-carrier absorption (FCA). Second order NLO in Si could greatly reduce power consumption of Si based optical switches/modulators but Si lacks second-order optical nonlinearity due to its centrosymmetric lattice character. There has been some attempts recently on the use of straining layers or electric fields to enhance SHG from silicon, but the actual effect of straining layers is recently in question and the need to apply a strong electric field in second order nonlinear processes proves a disservice to the development of chip-level nonlinear optical devices. Second harmonic generation (SHG) is a powerful tool to study the second order NLO behavior of complex nanoscale surfaces and interfaces.

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