4. Analysis of SPP nanofocusing by asymmetric metal-coated dielectric probe:
4.7 Conclusions
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Chapter 5
5. Conclusions
For the purpose of developing the probe using surface plasmon polariton (SPP) nanofocusing that is valid for incident linearly polarized (LP) wave, the asymmetric metal-coated dielectric conical probe is investigated numerically by the volume integral equation. It is found that it possible to perform SPP nanofocusing using this probe for incident LP Gaussian beam in addition to incident radially polarized (RP) beam. The basic characteristics of the strongly localized and enhanced optical near-fields on the tip of the probe and optical intensities inside the probe are investigated. For the incident LP beams, it is found that the optimum structure of the partially metal-coated dielectric probe exists. For the case of incident RP beam, partial metal-coating of the probe degrades the characteristic of nanofocusing, i.e., fully metal-coated conventional probe is the optimum shape for incident RP beam.
This dissertation is composed of four chapters. Chapter 1 was an introduction of surface plasmon polariton, how to exciting surface plasmon polaritons into nanometric optical waveguide circuits, motivation for this work as well as an overview of the components of this dissertation.
Chapter 2 presented the theory for calculation of propagation constant and the field distribution of a waveguide problem. We discretize the volume integral equation (VIE) by the method of moments using roof-top functions as basis and testing functions in
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each cubes and finally solve the resultant system of linear equations numerically by the iteration method called generalized minimum residual (GMRES) with Fast Fourier Transformation (FFT).
Chapter 3, by the volume integral equation method, the metal-coated dielectric probes of tilted conical shape were investigated for nanofocusing of surface plasmon polaritons. We consider the cases of incident radially polarized and linearly polarized Gaussian beams and found that the tilted SPP conical probe is valid for both incident LP and RP beams. The optical intensity at the tip of tilted metal-coated dielectric probe strongly depends on not only the degree of asymmetry but also the dissipation of coating metal for both incident RP and LP beams
Chapter 4, for the purpose of developing the probe using surface plasmon polariton nanofocusing that is valid for incident linearly polarized (LP) wave, the partially metal-coated dielectric conical probe is investigated. We considered the cases of incident linearly polarized (LP) and radially polarized (RP) Gaussian beams. The intensity distributions of various structure of the probe are investigated. Although the intensities of enhanced fields on the tip for incident LP beams are smaller than those obtained by the incident RP beams, it is found that the partially metal-coated dielectric probe can create the localized and enhances intensity on the tip that is a103 times larger than that of incident wave for incident LP waves.
Since the degree of the asymmetric shape and the coating metal of the probe affect significantly the maximum enhanced optical intensity at the tip for incident RP and LP beams, the findings of this study demonstrate that tilted conical probes must be carefully designed and fabricated.
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List of publications by the author
Journal publications
1. N. T. Thu, K. Tanaka, M. Tanaka and D. N. Chien, “Superfocusing of surface plasmon plaritons by metal-coated dielectric probe of tilted conical shape,” J. Opt.
Soc. Am. A, vol. 30, No. 6, pp. 1113-1118, 2013
2. N. T. Thu, K. Tanaka, M. Tanaka and D. N. Chien, “Analysis of surface plasmon polariton nanofocusing by asymmetric metal-coated dielectric probe: partial metal-coating,” Optical Communications,2015.06.073
IInternational Conference Publications
1. Ngo Thi Thu, Kazuo Tanaka, Masahiro Tanaka and Dao Ngoc Chien, “The Localized and enhanced optical near-field on the asymmetric metal-coated dielectric probe,” Proceedings of International Symposium on Antennas and Propagation pp.
391-394(2012)
Domestic conference publications
1. 㹌go Thi Thu, Kazuo Tanaka, Masahiro Tanaka and Dao Ngoc Chien, “Localized and enhanced optical near-field on metal-coated dielectric probe of tilted conical shape,” Proceedings of IEICE General Conference, B-1-1, 2013
2. Ngo Thi Thu, Kazuo Tanaka, Masahiro Tanaka and Dao Ngoc Chien, “Nanometric superfocusing of surface plasmon polariton by partially metal- coated dielectric conical probe,” The paper of Technical Meeting on Electromagnetic Theory, IEE