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Interest in the fabrication of nano -optical structures has increased dramatically
in recent years , due to advances in lithographic resolution . In particular , metallic
nanostructures are of interest because of their ability to concentrate light to well
below the diffraction limit . Such structures have many potential applications , including nanoscale photonics , quantum information processing and single molecule
detection /imaging . In the case of quantum computing and quantum communication ,
plasmon -based metal nanostructures offer the promise of scalable devices . This is because the small optical mode volumes of such structures give the large atom -photon
coupling needed to interface solid -state quantum bits (qubits ) to photons . The main
focus of this dissertation is on fabrication and testing of surface plasmon -based metal
nanostructures that can be used as optical wires for effciently collecting and directing an isolated atom or molecule's emission . In this work , Ag waveguides having
100nm£50nm and 50nm£50nm cross sections have been fabricated ranging from 5¹m
to 16¹m in length . Different types of coupling structures have also been fabricated to
allow in -coupling and out -coupling of free space light into and out of the nanometric
waveguides . The design of waveguides and couplers have been accomplished using a
commercial finite difference in time domain (FDTD ) software . Different nanofabrication techniques and methods have been investigated leading to robust and reliable
process conditions suitable for very high aspect ratio fabrication of metal structures . Detailed testing and characterization of the plasmon based metal waveguides and couplers have also been carried out . Test results have revealed effective surface plasmon
propagation range . 0 .5dB /¹m and 0 .07dB /¹m transmission losses have been found
for 100nm and 50nm wide waveguides respectively , which correspond to 1 /e propagation lengths of 9¹m and 60¹m . Input coupling effciency was found to be 2 % and
output coupling effciency was found to be 35 % . The fabrication and testing results
presented provide critical demonstrations to establish the feasibility of nanophotonic
integrated circuits , scalable quantum information processing devices , as well as other
devices , such as single molecule detectors and imaging systems . |
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