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All-optical metamaterial modulators : fabrication, simulation and characterization

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Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/12088

All-optical metamaterial modulators : fabrication, simulation and characterization

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Title: All-optical metamaterial modulators : fabrication, simulation and characterization
Author: Ku, Zahyun
Advisor(s): Brueck, Steven R. J.
Committee Member(s): Taylor, Antoinette
Brener, Igal
Sheik-Bahae, Mansoor
Malloy, Kevin
Krishna, Sanjay
Department: University of New Mexico. Dept. of Electrical and Computer Engineering
Subject: Metamaterial
Surface Plasmon Polariton
Nanofabrication
Optical Material
LC Subject(s): Light modulators.
Metamaterials.
Negative refractive index.
Degree Level: Doctoral
Abstract: Artificially structured composite metamaterials consist of sub-wavelength sized structures that exhibit unusual electromagnetic properties not found in nature. Since the first experimental verification in 2000, metamaterials have drawn considerable attention because of their broad range of potential applications. One of the most attractive features of metamaterials is to obtain negative refraction, termed left-handed materials or negative-index metamaterials, over a limited frequency band. Negative-index metamaterials at near infrared wavelength are fabricated with circular, elliptical and rectangular holes penetrating through metal/dielectric/metal films. All three negative-index metamaterial structures exhibit similar figure of merit; however, the transmission is higher for the negative-index metamaterial with rectangular holes as a result of an improved impedance match with the substrate-superstrate (air-glass) combination. In general, the processing procedure to fabricate the fishnet structured negative-index metamaterials is to define the hole-size using a polymetric material, usually by lithographically defining polymer posts, followed by deposition of the constitutive materials and dissolution of the polymer (liftoff processing). This processing (fabrication of posts: multi-layer deposition: liftoff) often gives rise to significant sidewall-angle because materials accumulate on the tops of the posts that define the structure, each successive film deposition has a somewhat larger aperture on the bottom metamaterial film, giving rise to a nonzero sidewall-angle and to optical bianisotropy. Finally, we demonstrate a nanometer-scale, sub-picosecond metamaterial device capable of over terabit/second all-optical communication in the near infrared spectrum. We achieve a 600 fs device response by utilizing a regime of sub-picosecond carrier dynamics in amorphous silicon and ~70% modulation in a path length of only 124 nm by exploiting the strong nonlinearities in metamaterials. We identify a characteristic signature associated with the negative index resonance in the pump-probe signal of a fishnet structure. We achieve much higher switching ratios at the fundamental resonance (~70%) relative to the secondary resonance (~20%) corresponding to the stronger negative index at the fundamental resonance. This device opens the door to other compact, tunable, ultrafast photonic devices and applications.
Graduation Date: December 2010
URI: http://hdl.handle.net/1928/12088


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