Browsing by Author "Tsai, Din Ping"

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Applications of plasmonic hotspots on laser-treated AgOx thin film
(2012)
Tseng, Ming Lun
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Huang, Yao-Wei
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Hsiao, Min-Kai
;
Huang, Hsin Wei
;
Lin, Yu-Hsuan
The femto-second-laser-treated AgOx thin film is used as the plasmon-active substrate for the applications of surface-enhanced Raman scattering (SERS), molecule sensing, and photocatalyst. The proposed technique is helpful for the solar energy harvest, green energy source, and biosensing with high efficiency and throughput.
Catalytically solid-phase self-organization of nanoporous SnS with optical depolarizability
(2016)
Cheng, Chih-Hsien
;
Chi, Yu-Chieh
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Wu, Chung-Lun
;
Lin, Chun-Jung
;
Tsai, Ling-Hsuan
The catalytic solid-phase synthesis of self-organized nanoporous tin sulfide (SnS) with enhanced absorption, manipulative transmittance and depolarization features is demonstrated. Using an ultralow radio-frequency (RF) sputtering power, the variation of the orientation angle between the anodized aluminum oxide (AAO) membrane and the axis of the sputtered ion beam detunes the catalytically synthesized SnS from nanorod to nanoporous morphology, along the sidewall of the AAO membrane. The ultraslow catalytic sputtering synthesis on the AAO at the RF plasma power of 20 W and the orientation angle of 0 degrees regulates the porosity and integrality of nanoporous SnS, with average pore diameter of 80-150 nm. When transferring from planar to nanoporous structure, the phase composition changes from SnS to SnS2-Sn2S3, and the optical bandgap shrinks from 1.43 to 1.16 eV, due to the preferred crystalline orientation, which also contributes to an ultralow reflectance of <1% at 200-500 nm when both the transmittance and the surface scattering remain at their maxima. The absorption coefficient is enhanced by nearly one order of magnitude with its minimum of >5 x 10(4) cm(-1) at the wavelength between 200 and 700 nm, due to the red-shifting of the absorption spectrum to at least 100 nm. The catalytically self-organized nanoporous SnS causes strong haze and beam divergence of 20 degrees-30 degrees by depolarized nonlinear scattering at the surface, which favors the solar energy conversion with reduced surface reflection and enhanced photon scattering under preserved transmittance.
Classical Analog of Electromagnetically Induced Transparency in the Visible Range With Ultra-Compact Plasmonic Micro-Ring Resonators
(2015-07-01)
Hsu, Yi-Jang
;
Cheng, Bo Han
;
Lai, Yinchieh
;
Tsai, Din Ping
;
光電工程學系
We theoretically show that it should be possible to demonstrate Electromagnetic-Induced-Transparency-like (EIT-like) effects in the visible range by using ultra-compact plasmonic micro-ring resonators with mu m(2) order foot print. By using the finite-difference time-domain (FDTD) numerical method and the coupled mode theory (CMT) collaboratively, the transmission intensity, phase, and group delay spectra of the coupled plasmonic ring resonators are theoretically calculated with the inclusion of metallic loss and dispersion through the Drude model. The interference induced transmission peak can be successfully achieved through suitable design of the plasmonic ring resonator structure.
Control of the Metal-Insulator Transition at Complex Oxide Heterointerfaces through Visible Light
(2016-01-27)
Lin, Jheng-Cyuan
;
Vu Thanh Tra
;
Tsai, Dung-Sheng
;
Lin, Tai-Te
;
Huang, Po-Cheng
The coupling of the localized surface plasmon resonance of Au nanoparticles is utilized to deliver a visible-light stimulus to control conduction at the LaAlO3/SrTiO3 interface. A giant photoresponse and the controllable metal-insulator transition are characterized at this heterointerface. This study paves a new route to optical control of the functionality at the heterointerfaces.
Deep-Ultraviolet Hyperbolic Metacavity Laser
(2018-05-24)
Shen, Kun-Ching
;
Ku, Chen-Ta
;
Hsieh, Chiieh
;
Kuo, Hao-Chung
;
Cheng, Yuh-Jen
Given the high demand for miniaturized optoelectronic circuits, plasmonic devices with the capability of generating coherent radiation at deep subwavelength scales have attracted great interest for diverse applications such as nanoantennas, single photon sources, and nanosensors. However, the design of such lasing devices remains a challenging issue because of the long structure requirements for producing strong radiation feedback. Here, a plasmonic laser made by using a nanoscale hyperbolic metamaterial cube, called hyperbolic metacavity, on a multiple quantum-well (MQW), deep-ultraviolet emitter is presented. The specifically designed metacavity merges plasmon resonant modes within the cube and provides a unique resonant radiation feedback to the MQW. This unique plasmon field allows the dipoles of the MQW with various orientations into radiative emission, achieving enhancement of spontaneous emission rate by a factor of 33 and of quantum efficiency by a factor of 2.5, which is beneficial for coherent laser action. The hyperbolic metacavity laser shows a clear clamping of spontaneous emission above the threshold, which demonstrates a near complete radiation coupling of the MQW with the metacavity. This approach shown here can greatly simplify the requirements of plasmonic nanolaser with a long plasmonic structure, and the metacavity effect can be extended to many other material systems.
Enhanced Radiative Emission of MQW by Resonant Modes of Hyperbolic Metamaterial Resonator
(2019-01-01)
Shen, Kun-Ching
;
Hsu, Lung-Hsing
;
Tsai, Din Ping
;
Kuo, Hao-Chung
;
Lin, Chien-Chung
We report the use of resonant modes of a hyperbolic metamaterial cube made of multiple metal/dielectric layer structure to enhance the radiative emission of multiple quantum wells. The mode analysis and photoluminescence will be discussed. (C) 2019 The Author(s)
High birefringence photonic crystal fiber with a complex unit cell of asymmetric elliptical air hole cladding
(2007-08-01)
Sun, Yuh-Sien
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Chau, Yuan-Fong
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Yeh, Han-Hsuan
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Shen, Lin-Fang
;
Yang, Tzong-Jer
High birefringence induced by elliptical air hole photonic crystal fibers (EHPCFs) is analyzed numerically using the finite-element method. Statistical correlations between the birefringence and the various parameters are obtained. We found that the complex elliptical air hole is better than that of a circular one to obtain high birefringence in photonic crystal fibers. Our suggested structures can considerably enhance the birefringence in EHPCFs and show that the birefringence can be as high as 1.1294 x 10(-2), which is higher than the birefringence obtained from conventional step-index fiber (5 X 10(-4)), circular air holes PCF (3.7 X 10(-3)), and elliptical hollow PCF (2.35 x 10(-3)). (C) 2007 Optical Society of America.
Near-Field Optical Imaging of a Porous Au Film: Influences of Topographic Artifacts and Surface Plasmons
(2013-06-01)
Lin, Yu-Hsuan
;
Haendel, Benjamin
;
Huang, Hung Ji
;
Chen, Hsiang-An
;
Chen, Yung-Fu
In this work, near-field scanning optical microscopy is employed to study a porous Au film and the direct observation of topographic artifacts and surface plasmon influences is revealed. Under tip illumination, topographic artifacts are found to be present in a reflection mode optical image but not in a transmission mode image. A simple algorithm is used for filtering the topographic artifacts and extracting a correct near-field optical image approximately. On the other hand, surface plasmon influences are present in both modes. By using three exciting wavelengths of 488, 647.1, and 520.8 nm, it is confirmed that a suitable wavelength should be chosen for avoiding the surface plasmon interference in a near-field optical investigation of morphological or material dielectric contrast. Finally, plasmonic or nonplasmonic regions on the porous Au film can be identified from the observed optical intensity variation in the optical images obtained at incident polarizations of 0 degrees, 90 degrees, and 45 degrees.
Near-field scanning optical microscopy using a super-resolution cover glass slip
(2012-07-16)
Lin, Yu-Hsuan
;
Tsai, Din Ping
;
電子物理學系
;
Department of Electrophysics
This study presents a novel near-field optics technology. A near-field cover glass slip (NF-CGS) was developed to improve the resolution of optical microscopy beyond the diffraction limit. A multi-layered structure of cover glass/ZnS-SiO2 (130 nm)/AgOx (15 nm)/ ZnS-SiO2 (40 nm) was employed to generate the optical coupling effect for increasing the contrast and enhancing resolution of imaging. This novel innovation is expected to be employed in near-field imaging techniques for samples in different environments because of its simplicity, rapid laser scanning, and minimal costs. Experimental results of 500 nm, 200 nm, and 100 nm standard polystyrene nanospheres on NF-CGS and normal cover glass are demonstrated and imaged by using a laser scanning confocal microscope. (C) 2012 Optical Society of America
Plasmon Inducing Effects for Enhanced Photoelectrochemical Water Splitting: X-ray Absorption Approach to Electronic Structures
(2012-08-01)
Chen, Hao Ming
;
Chen, Chih Kai
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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
;
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.
Stress-Induced 3D Chiral Fractal Metasurface for Enhanced and Stabilized Broadband Near-Field Optical Chirality
(2019-08-01)
Tseng, Ming Lun
;
Lin, Zhan-Hong
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Kuo, Hsin Yu
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Huang, Tzu-Ting
;
Huang, Yi-Teng
Metasurfaces comprising 3D chiral structures have shown great potential in chiroptical applications such as chiral optical components and sensing. So far, the main challenges lie in the nanofabrication and the limited operational bandwidth. Homogeneous and localized broadband near-field optical chirality enhancement has not been achieved. Here, an effective nanofabrication method to create a 3D chiral metasurface with far- and near-field broadband chiroptical properties is demonstrated. A focused ion beam is used to cut and stretch nanowires into 3D Archimedean spirals from stacked films. The 3D Archimedean spiral is a self-similar chiral fractal structure sensitive to the chirality of light. The spiral exhibits far- and near-field broadband chiroptical responses from 2 to 8 mu m. With circularly polarized light (CPL), the spiral shows superior far-field transmission dissymmetry and handedness-dependent near-field localization. With linearly polarized excitation, homogeneous and highly enhanced broadband near-field optical chirality is generated at a stably localized position inside the spiral. The effective yet straightforward fabrication strategy allows easy fabrication of 3D chiral structures with superior broadband far-field chiroptical response as well as strongly enhanced and stably localized broadband near-field optical chirality. The reported method and chiral metasurface may find applications in broadband chiral optics and chiral sensing.
Sub-wavelength GaN-based membrane high contrast grating reflectors
(2012-08-27)
Wu, Tzeng Tsong
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Syu, Yu Cheng
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Wu, Shu Hsien
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Chen, Wei Ting
;
Lu, Tien Chang
The GaN-based membrane high contrast grating (HCG) reflectors have been fabricated and investigated. The structural parameters including grating periods, grating height, filling factors and air-gap height were calculated to realize high reflectivity spectra with broad bandwidth by the rigorous coupled-wave analysis and finite-difference time-domain method. Based on the optimized simulation results, the GaN-based membrane HCGs were fabricated by e-beam lithography and focused-ion beam process. The fabricated GaN-based membrane HCG reflectors revealed high reflectivity at 460 nm band with large stopband width of 60 nm in the TE polarization measured by using the micro-reflectivity spectrometer. The experimental results also showed a good agreement with simulated ones. We believe this study will be helpful for development of the GaN-based novel light emitting devices in the blue or UV region. (C) 2012 Optical Society of America
Subwavelength optical imaging through a silver nanorod
(2007-03-01)
Chau, Yuan-Fong
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Tsai, Din Ping
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Hu, Guang-Wei
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Shen, Lin-Fang
;
Yang, Tzong-Jer
We numerically investigated subwavelength imaging in a silver nanorod of 50-nm height and 20-nm diam buried in dielectric background (SiO2)with a finite-difference time-domain (FDTD) method in the three dimensions. The near-field components of the Gaussian incident beam were plasmonically transferred through the input end of a silver nanorod to reproduce the light distributions of the incident wave at the output end. The field distributions were calculated at the different sectional planes of the rods, and it was found that the spatial resolution was less than 40 nm given by the rod size, which is much beyond the diffraction limit of the conventional imaging system. The field intensity in the image plane was well resolved due to the collection of surface plasmon polaritons. The behaviors of the three components of field distribution at entrance and exit from the nanorod and the influences of the optical field distribution generated by some factors are also discussed in detail. The proposed structure possesses a deep transfer of superresolution image and can be used with image transfer. (C) 2007 Society of Photo-Optical Instrumentation Engineers.
The plasmon and distribution effects between incident light and active layer in PtOx-type super-resolution near-field structure
(2008-03-01)
Chau, Yuan-Fong
;
Tsai, Din Ping
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Shen, Lin-Fang
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Yang, Tzong-Jer
;
Sun, Yuh-Sien
The plasmon and distribution effects of collective localized surface plasmons between incident light and active layer of PtOx-type super resolution near-field structure (super-RENS) have been studied using finite-difference time-domain method. Four types of distribution of Pt nanoparticles, i.e., type A, B, C, and D in active layer are investigated. We find that type C and D in active layer can provide higher field intensity in a wider range of particle size when the particle sizes are varied, and the out-going filed emerging from the active layer exhibit smaller spot size than those of type A and B. Type B, C and D also provide the additional path longer than that of type A, and excite more evanescent field which located in the far edge of the bubble from the optical axis of the incident beam. Results show that the type C structure is the best choice in the view point of designing the PtOx-type super-RENS. This study provides new information to design a super-RENS with superior resolution as well as other applications in nano photonic devices. (C) 2007 Elsevier B.V. All rights reserved.
Time-resolved phase-change recording mark formation with zinc oxide near-field optical active layer
(2015-09-01)
Kao, Tsung Sheng
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Chen, Mu-Ku
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Chen, Jia-Wern
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Chen, Yi-Hao
;
Wu, Pei Ru
In this paper, an optical active thin film of zinc oxide (ZnOx) nano-composites exploited for the enhancement of optical signals in an ultra-high density recording scheme has been demonstrated. Via the electron microscope investigation, the results display randomly distributed crystalline nanograins in the ZnOx thin films. Optical disks with the ZnOx nanostructured thin films show that the carrier-to-noise ratio (CNR) above 25 dB can be obtained at the mark trains of 100 nm, while the optimal writing power is reduced as a function of the increasing thickness of the ZnOx films. Furthermore, by conducting a series of the optical pump-probe experiments, the optical responses of recording marks on as-deposited phase-change Ge2Sb2Te5 (as-GST) recording layers present that the highly contrast bright recording bits can be acquired with the existence of the ZnOx nanostructured thin films, providing prospective potentials in future data storage and optoelectronic devices. (C) 2015 The Japan Society of Applied Physics
Toward Omnidirectional Light Absorption by Plasmonic Effect for High-Efficiency Flexible Nonvacuum Cu(In,Ga)Se-2 Thin Film Solar Cells
(2014-09-01)
Chen, Shih-Chen
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Chen, Yi-Ju
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Chen, Wei Ting
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Yen, Yu-Ting
;
Kao, Tsung Sheng
We have successfully demonstrated a great advantage of plasmonic Au nanoparticles for efficient enhancement of Cu(In,Ga)Se-2(CIGS) flexible photovoltaic devices. The incorporation of Au NPs can eliminate obstacles in the way of developing ink-printing CIGS flexible thin film photovoltaics (TFPV), such as poor absorption at wavelengths in the high intensity region of solar spectrum, and that occurs significantly at large incident angle of solar irradiation. The enhancement of external quantum efficiency and photocurrent have been systematically analyzed via the calculated electromagnetic field distribution. Finally, the major benefits of the localized surface plasmon resonances (LSPR) in visible wavelength have been investigated by ultrabroadband pump-probe spectroscopy, providing a solid evidence on the strong absorption and reduction of surface recombination that increases electron hole generation and improves the carrier transportation in the vicinity of pn-juction.
Transferring the bendable substrateless GaN LED grown on a thin C-rich SiC buffer layer to flexible dielectric and metallic plates
(2017-01-21)
Cheng, Chih-Hsien
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Huang, Tzu-Wei
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Wu, Chung-Lun
;
Chen, Mu Ku
;
Chu, Cheng Hung
By growing an epitaxial GaN LED on C-rich a-SiC buffer deposited SiO2/Si substrate, the simplified transfer to versatile flexible metallic/dielectric membranes is demonstrated. Both the high growth temperature at 1000 degrees C and the slow deposition rate played important roles in the meticulous MOCVD growth of n-GaN along the surface normal of the a-SiC at the very beginning. High substrate temperature facilitated the refinement of C-rich SiC buffer from amorphous to partially crystalline with (0004)-orientation, which effectively reduces the lattice mismatch between n-GaN and SiC at the interface so as to gradually improve the crystalline n-GaN regrowth. The substrateless GaN LED transferred to flexible copper plates showed reduced turn-on voltage of 2.6 V, enhanced output power of 370 mW, enlarged power-to-current slope of 1.24 W A(-1), increased external quantum efficiency of 45%, and reduced efficiency droop of 15% under a bias of 300 mA. The thermal conductivity of the transferred substrate affected the EL peak wavelength shift of the substrateless GaN LED on SiC buffer. Heating the GaN LED on flexible copper plate to 65 degrees C only reduced its power by 10% and red-shifted its wavelength by 1 nm under a bias at 100 mA; the Auger effect resulted in a degraded EQE of 39.1% and an enlarged EQE droop of 8.5%. Bending the surface diameter of the curvature of the copper plate to 1.2 cm decayed the output power by 12% and red-shifted the EL peak by 5 nm because of the lattice strain induced quantum confined Stark effect (QCSE). Such a bendable substrateless GaN LED transferred to flexible membrane with superior heat dissipation and bending tolerance is a desired lighting element for green photonics in this era.
Twisted Surface Plasmons with Spin-Controlled Gold Surfaces
(2019-04-01)
Tsai, Wei-Yi
;
Sun, Quan
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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.