Browsing by Author "Wu, Pin Chieh"

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Plasmon Inducing Effects for Enhanced Photoelectrochemical Water Splitting: X-ray Absorption Approach to Electronic Structures
(2012-08-01)
Chen, Hao Ming
;
Chen, Chih Kai
;
Chen, Chih-Jung
;
Cheng, Liang-Chien
;
Wu, Pin Chieh
Artificial photosynthesis using semiconductors has been investigated for more than three decades for the purpose of transferring solar energy into chemical fuels. Numerous studies have revealed that the introduction of plasmonic materials into photochemical reaction can substantially enhance the photo response to the solar splitting of water. Until recently, few systematic studies have provided clear evidence concerning how plasmon excitation and which factor dominates the solar splitting of water in photovoltaic devices. This work demonstrates the effects of plasmons upon an Au nanostructure-ZnO nanorods array as a photoanode. Several strategies have been successfully adopted to reveal the mutually independent contributions of various plasmonic effects under solar irradiation. These have clarified that the coupling of hot electrons that are formed by plasmons and the electromagnetic field can effectively increase the probability of a photochemical reaction in the splitting of water. These findings support a new approach to investigating localized plasmon-induced effects and charge separation in photoelectrochemical processes, and solar water splitting was used herein as platform to explore mechanisms of enhancement of surface plasmon resonance.
Second Harmonic Light Manipulation with Vertical Split Ring Resonators
(2019-02-15)
Tsai, Wei-Yi
;
Chung, Tsung Lin
;
Hsiao, Hui-Hsin
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Chen, Jia-Wern
;
Lin, Ren Jie
The second harmonic generation (SHG) of vertical and planar split-ring resonators (SRRs) that are broken centro-symmetry configurations at the interface of metal surface and air is investigated. Strong interactions, better electromagnetic field confinements, and less leakage into the substrate for vertical SRRs are found. Experimental results show a 2.6-fold enhancement of SHG nonlinearity, which is in good agreement with simulations and calculations. Demonstrations of 3D metastructures and vertical SRRs with strong SHG nonlinearity majorly result from magnetic dipole and electric quadrupole clearly provides potential applications for photonics and sensing.
Twisted Surface Plasmons with Spin-Controlled Gold Surfaces
(2019-04-01)
Tsai, Wei-Yi
;
Sun, Quan
;
Hu, Guangwei
;
Wu, Pin Chieh
;
Lin, Ren Jie
Twisted photon, associated with orbital angular momentum (OAM), is a physical notion that has long captivated the intriguing imagination and wide applications. Owing to the native orthogonality between different topological charges of the vortices, it will be of significant value to generate, access, and discriminate the vortex on integrated chips. Archimedean spirals or multiple split gratings are commonly employed to generate OAMs on plasmonic films. However, the single-crystalline plasmonic surface sets a very stringent condition of probing the on-chip OAM dynamics at sub-femtosecond scale. In previous reports, spins of the incident light and actual topological charge of the on-chip OAM generator are also hybridized due to the intrinsic spin-to-orbital angular momentum conversion, making the direct discrimination of plasmonic vortex impossible. Here, a paradigm of generating twisted surface plasmons is presented in a fully spin-controlled fashion. With the two-photon photoemission electron microscopy, the dynamics of OAM formation is demonstrated at subwavelength spatial resolution and sub-femtosecond temporal resolution simultaneously, revealing its OAM-dependent angular velocity. In addition, this scheme of twisting on-chip plasmons shows that the challenging crystalline requirement of the thin film can be significantly alleviated. The results open up a distinct way to multiplex, record, and read the information with plasmons.