Browsing by Author "Chang, Kai-Hao"

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Efficient modulation of subwavelength focusing via meta-aperture-based plasmonic lens for multifunction applications
(2018-09-11)
Chang, Kai-Hao
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Chen, Yen-Chun
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Chang, Wen-Hao
;
Lee, Po-Tsung
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電子物理學系
Subwavelength focusing is crucial for many applications in photonics including super-resolution micro/nanoscopy, nanolithography, and optical trapping. However, most nanostructures exhibit poor ability to modulate focusing spot, which makes them hard to achieve ultra-small resolution. Here, we propose three kinds of plasmonic lens (PL) by utilizing different meta-aperture designs for efficient subwavelength focusing modulation. The shape of nanoaperture strongly influences the diffraction properties. Spatial modulation of focusing spot by employing a circular array of proposed nanoapertures is explored. The best focusing performance among these PLs is the design of T-shape nanoaperture, which has great resolution achieving ultra-small focusing spot of 0.14.2 and 0.20.2 (lambda = 633 nm) for simulation and experiment respectively, better than lots of focusing devices especially by using linear polarization. Multiple-object trapping can be realized by using T-shape nanoaperture-based PL. Our designed PLs with different nanoapertures demonstrate the capability to broaden and integrate different functionalities for on-chip nanotechnologies development.
Engineering surface lattice resonance of elliptical gold nanodisk array for enhanced strain sensing
(2018-12-10)
Chang, Kai-Hao
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Cheng, Jiunn-Shouh
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Lu, Tsan-Wen
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Lee, Po-Tsung
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光電工程學系
We demonstrate an elliptical gold nanodisk array (GNA) for engineering the spectral profile of surface lattice resonance (SLR). The nanodisk's shape has a great impact on SLR. A small linewidth of 20 mn at an aspect ratio of 1.17 and a large wavelength tuning of 64 nm within 4% strain via different orientations and polarizations is achieved experimentally. The enhanced wavelength response of 6.93 mu per 1% strain variation for elliptical GNA is 2.4 times better than that for general circular GNA. Furthermore, figure of merit of strain sensing for elliptical GNA approaches 5.7 times greater than that for circular GNA. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Plasmonic Properties and Biosensing of Gold Elliptical Nanoring Arrays
(2013)
Tsai, Chia-Yang
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Chang, Kai-Hao
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Wu, Che-Yao
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Lee, Po-Tsung
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光電工程學系
We investigate the optical properties and biosensing of gold elliptical nanoring (ENR) arrays with various aspect ratios. Gold ENRs with 1.58 high aspect ratio show a total wavelength shift of 35 nm for molecule sensing.
Subwavelength Focusing of Hybrid Ag-Au Plasmonic Lens with Variant Slit Widths
(2015)
Chen, Min-Hsiu
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Chang, Kai-Hao
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Lee, Po-Tsung
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光電工程學系
;
Department of Photonics
We design the hybrid Ag-Au double-layered structure as plasmonic lens. The subwavelength focusing can be achieved with focal length within 500 nm. Furthermore, the focusing properties can be tuned by the thickness ratio of Ag/Au. Finally, we find the best of focusing effect as the thickness ratio is 1.
The aspect ratio effect on plasmonic properties and biosensing of bonding mode in gold elliptical nanoring arrays
(2013-06-17)
Tsai, Chia-Yang
;
Chang, Kai-Hao
;
Wu, Che-Yao
;
Lee, Po-Tsung
;
光電工程學系
We investigate both numerically and experimentally the optical properties and biosensing of gold elliptical nanoring (ENR) arrays with various aspect ratios. The gold ENR exhibits a strong localized surface plasmon bonding mode in near-infrared region, whose peak wavelength is red-shifted as increasing the aspect ratio under longitudinal and transverse polarizations. Furthermore, the disk- and hole-like optical properties for longitudinal and transverse modes are observed, which cause different behaviors in field intensity enhancement. For biomolecule sensing, we find that both modes show increased surface sensitivities when enlarging the aspect ratio of gold ENR. (C) 2013 Optical Society of America
Three-Dimensional Resolvable Plasmonic Concentric Compound Lens: Approaching the Axial Resolution from Microscale to Nanoscale
(2018-03-01)
Chang, Kai-Hao
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Chen, Yen-Chun
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Chang, Wen-Hao
;
Lee, Po-Tsung
;
電機學院
We propose the design and working principle of a plasmonic concentric compound lens (CCL) comprising inner circular nanoslits and outer circular nanogrooves. Dual-wavelength operations have been achieved for 650 and 750 nm at nanoscale and microscale focal lengths along with their depth of focus (DOF). By tuning the arrangement of nanogrooves, the axial resolution can be modulated and the narrowest DOF is achieved by a design of gradually decreasing groove width. For the ultrahigh tunability of axial resolution, DOF over 400 nm for both working wavelengths is also achieved. We not only developed an approximate-perturbed-focus model for explaining the performance of DOF but also found an extraordinary way to improve the resolution. The enhanced resonance of central disk as nannoantenna in CCL also has great influence on nanofocusing with different deigns of outer nanogrooves. This work provides new sight of focusing ability governed by the general optical nanogrooves. The optimized CCL shows excellent focusing performance with a lateral resolution down to 0.32 lambda (lambda= 650 nm), which is the best resolving ability achieved thus far in the near field region with a long focal length up to 500 nm.