In this dissertation, I explore new plasmonic structures and devices for manipulating light at the nanoscale: slow-light waveguides and compact couplers. I first introduce a plasmonic waveguide system, based on a plasmonic analogue of electromagnetically induced transparency (EIT), which supports a subwavelength slow-light mode, and exhibits a small group velocity dispersion. The system consists of a periodic array of two metal-dielectric-metal (MDM) stub resonators side-coupled to a MDM waveguide. Decreasing the frequency spacing between the two resonances increases the slowdown factor and decreases the bandwidth of the slow-light band.
I also show that there is a trade-off between the slowdown factor and the propagation length of the slow-light mode. I next consider Mach-Zehnder interferometer (MZI) sensors in which the sensing arm consists of a slow-light waveguide based on a plasmonic analogue of EIT. I show that a MZI sensor using such a waveguide leads to approximately an order of magnitude enhancement in the refractive index sensitivity, and therefore in the minimum detectable refractive index change, compared to a MZI sensor using a conventional MDM waveguide.
I also introduce compact wavelength-scale slit-based structures for coupling free space light into MDM subwavelength plasmonic waveguides. I first show that for a single slit structure the coupling efficiency is limited by a trade-off between the light power coupled into the slit, and the transmission of the slit-MDM waveguide junction. I next consider a two-section slit structure, and show that for such a structure the upper slit section enhances the coupling of the incident light into the lower slit section. The optimized two-section slit structure results in ¡ 2.3 times enhancement of the coupling into the MDM plasmonic waveguide compared to the optimized single-slit structure. I finally consider a symmetric double-slit structure, and show that for such a structure the surface plasmons excited at the metal-air interfaces are partially coupled into the slits. Thus, the coupling of the incident light into the slits is greatly enhanced, and the optimized double-slit structure results in ¡ 3.3 times coupling enhancement compared to the optimized single-slit structure. In all cases the coupler response is broadband.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-11122012-124413 |
| Date | 19 November 2012 |
| Creators | Huang, Yin |
| Contributors | Rose, Kenneth, Dowling, Jonathan, Daniels-Race, Theda, Lee, Hwang, Veronis, Georgios |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-11122012-124413/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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