Browsing by Author "Chang, Che-Yuan"

Now showing 1 - 7 of 7

4 Tunability and Optimization of Coupling Efficiency in Tamm Plasmon Modes
(2015-07-01)
Chang, Che-Yuan
;
Chen, Yi-Hsuan
;
Tsai, Yu-Lin
;
Kuo, Hao-Chung
;
Chen, Kuo-Ping
A Tamm plasmon polariton is a plasmonic resonance excited at the boundary between a photonic crystal and a metal. In this paper, a novel approach based on admittance loci is proposed to demonstrate the relation between thin-film structures and the corresponding Tamm plasmon modes. The tunability of the resonance wavelength and optimization of coupling efficiency are demonstrated. In addition, by using different metals to couple Tamm plasmon modes in the visible spectrum, silver has 4.7 times larger Q-factor than gold and 84 times larger than aluminum at 700 nm. The near-field enhancement of silver Tamm plasmon modes could be up to eight times larger than incident EM waves.
Controllable Tamm Plasmon Effect Designed by Admittance Loci
(2014-01-01)
Chang, Che-Yuan
;
Chen, Kuo-Ping
;
影像與生醫光電研究所
;
Institute of Imaging and Biomedical Photonics
Tamm plasmon is a plasmonic resonance happens at the boundary of photonic crystal and metal. In this work, a novel design tool based on admittance loci is proposed to demonstrate the relationship between Tamm plasmon structure and the corresponding resonance effect. The tunability of resonance wavelengths and the optimization of coupling efficiency are presented.
Gate-induced localized states in graphene: Topological nature in their formation
(2018-12-26)
Wang, L. Y.
;
Chang, Che-Yuan
;
Chu, C. S.
;
電子物理學系
;
Department of Electrophysics
In this work, we show that an N-C-chain gate potential along the armchair chain (direction (y) over cap) of a graphene sheet gives rise to topological localized states (LSs): one branch for N-C = 1 and two branches for N-C >= 2. These LSs are shown to form whenever the gate-induced potential V-0 is nonzero. The topological nature behind the formation of these LSs is revealed (for N-C = 1, 2) by showing, for V-0 not equal 0, that the LS-secular equation can be cast into a pseudospin-rotation form on which rotation upon a valley-associated pseudospin is to equate with another valley-associated pseudospin. Both pseudospins are on the same side of the gate potential. That the rotation angle of the pseudospin-rotation operator falls within the range of variation of the relative angle Delta theta(p) between the two pseudospins, as the energy E varies across the entire energy gap for a given k(y), demonstrates the topological nature and the inevitability of the LS branch formation. These topological LS branches exhibit Dirac-point characteristics, with dispersion relations leading out from the Dirac point (at k(y) = 0). For general multiple (N-C > 1) carbon chain gate-potential cases, the number N-LS of LS branches are found to increase with V-0, up to a maximum of N-LS,(max) = N-C. Yet LS branches carrying the Dirac-point characteristics are found to be fixed at two.
High Sensitivity Dark Mode Plasmonic Resonance of Gold Nanoantennas Arrays in Evanescent Waves
(2015)
Chen, Kuo-Ping
;
Chen, Yi-Hsun
;
Kuo, Yu-Lun
;
Yang, Zhen-hong
;
Chang, Che-Yuan
Plasmonic dark modes of gold nanoantennas are observed in evanescent waves. Comparing with the bright mode for normal incidence of nanoantennas, dark mode resonance not only has a higher extinction coefficient but also achieves higher sensitivity to the surrounding environment. The sensitivity of the dark mode of gold nanoantenna is 4.84 times that of the bright mode in terms of the figure of merit.
Hybridization models of gold nanoantennas arrays in polarization dependent evanescent waves
(2015-01-01)
Chen, Kuo-Ping
;
Chen, Yi-Hsun
;
Chang, Che-Yuan
;
Kuo, Yu-Lun
;
Yang, Zhen-hong
The plasmonic coupling of nanoantennas could be explained by the plasmon hybridization model introduced. For symmetric nanoparticles pairs, the coupled mode can be shifted to higher or lower frequencies, depending on the phase of the fields from each nanoparticle. In p-polarization, the in-phase response is called bonding mode and out of phase response is called antibonding mode, which are analogous to the molecular orbital theory. The bonding mode, located at a lower energy level, could be strongly excited by normal incidence, but antibonding mode, located at a higher energy level, could hardly excited by normal incident plane wave and which is not easy to be observed. In literatures, the antibonding mode could only be excited by highly focused laser beams, the radiation from a local emitter, and the evanescent field produced by total internal reflection9. Although the observation is not easy, the antibonding mode has brought a lot of attention because of the slower radiative decay and narrower linewidths. However, there are not many researches discussing the sensor application of the plasmonic antibonding mode of nanoantenans arrays. In this work, gold nanoantennas antibonding mode in TM and TE polarized evanescent field is investigated and the sensitivity to the refractive index change of surrounding medium is compared to bonding mode in normal incidence. Furthermore, in normal incidence, due to the impedance mismatch between the dielectric and substrate, strong reflectance happens at the resonance in bonding mode which could reduce the coupling efficiency. In order to achieve higher energy coupling efficiency, total internal reflection could be used to minimize the impedance mismatch and transfer the input energy into antibonding mode plasmonic resonance.
Observation of the high-sensitivity plasmonic dipolar antibonding mode of gold nanoantennas in evanescent waves
(2014-07-21)
Chen, Yi-Hsun
;
Chen, Kuo-Ping
;
Shih, Min-Hsiung
;
Chang, Che-Yuan
;
照明與能源光電研究所
Plasmonic dipolar antibonding modes of gold nanoantennas are observed in evanescent waves. Comparing with the bonding mode for normal incidence, the use of prism coupling to transfer the energy of incident light to plasmonic resonance in nanoantennas not only has a higher extinction coefficient but also achieves higher sensitivity to the surrounding environment. The sensitivity of the antibonding mode of gold nanoantenna is 4.84 times that of the bonding mode in terms of the figure of merit. (C) 2014 AIP Publishing LLC.
Observation of the high-sensitivity plasmonic dipolar antibonding mode of gold nanoantennas in evanescent waves
(2014-07-21)
Chen, Yi-Hsun
;
Chen, Kuo-Ping
;
Shih, Min-Hsiung
;
Chang, Che-Yuan
;
照明與能源光電研究所
Plasmonic dipolar antibonding modes of gold nanoantennas are observed in evanescent waves. Comparing with the bonding mode for normal incidence, the use of prism coupling to transfer the energy of incident light to plasmonic resonance in nanoantennas not only has a higher extinction coefficient but also achieves higher sensitivity to the surrounding environment. The sensitivity of the antibonding mode of gold nanoantenna is 4.84 times that of the bonding mode in terms of the figure of merit. (C) 2014 AIP Publishing LLC.