Dissertation/Thesis Abstract

All Optical Switch Using Indium-Tin-Oxide in a Diffracting Grating
by Bhardwaj, Pranjal, M.S., California State University, Long Beach, 2018, 51; 10977882
Abstract (Summary)

A switch is defined as a component of electrical circuit that interrupts and diverts electrical current in a circuit, in order to regulate flow of power through a conductor. There are primarily two types of switches: mechanical and electrical. Mechanical switches require physical or manual contact for operation. Electrical switches function based on semiconductor properties of conducting current when doped with impurities. Transistors are essential and one of the most prevalent semiconductor switches in modern computing. A network composed of millions of transistors that work together to enable our computers to function effectively. Transistors only function at a given maximum speed, which is limited by the drift velocity of charge carriers between the junctions of a transistor. Now that there is a higher need for faster computing than ever before, engineers are about to reach a roadblock where we would not be able to pack more and transistors into the limited space available. There is a need for a different type of switch, one that is not limited by the speed of a charge carrier.

This thesis proposes an all-optical switch, which operates by lasers instead of electrical signals, as an alternative to electrical switches. The primary purpose of an all-optical switch is logical switching similar to an electronic transistor. The all-optical switch proposed only works with lasers without relying on external stimulation for any operational step to achieve switching operation. Coupled-mode equations for high-contrast-gratings (HCGs) were solved in MATLAB to determine the grating dimensions that exhibit fano-resonance. The resulting gratings were modeled using the simulation software Lumerical FDTD in conjunction with non-linear optical medium Indium-tin-oxide (ITO), exploiting ITO’s property to undergo change in refractive index upon irradiation by light at epsilon-near-zero frequencies, to achieve the switching operation in the modeled nanostructure.

It is shown that the proposed nanostructure can attenuate the incoming control signal (probe beam) and shifts its transmission curve by a band gap of ~6nm, on application of the excitation beam (pump beam) to a thin ITO layer incorporated into the structure. A detector calibrated to read the control signal will interpret this change in transmission as a logical zero. In conclusion, it is concluded that the nanostructure can act as an optical switch and perform logical switching in several hundered femtoseconds that puts the operational frequency of the conceptual nanostructure device in terahertz range.

Indexing (document details)
Advisor: Ahmed, Aftab
Commitee: Kwon, Seok-Chul, Mozumdar, Mohammad
School: California State University, Long Beach
Department: Electrical Engineering
School Location: United States -- California
Source: MAI 58/03M(E), Masters Abstracts International
Subjects: Engineering, Electrical engineering
Publication Number: 10977882
ISBN: 9780438791800
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