Browsing by Author "Chou, Bo-Tsun"

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Characteristic of UV Plasmonic Nanolasers with Different Spacer Thickness
(2016)
Chou, Yu-Hsun
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Chou, Bo-Tsun
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Lin, Sheng-Di
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Lin, Tzy-Rong
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Lin, Chien-Chung
We report on plasmonic lasers with ZnO nanowire lying on single-crystalline silver film with different SiO2 thickness spacer. Spacer thickness were optimized to adjust the surface plasmon dispersion curve and resulting different group index.
DESIGN OF A NEAR-INFRARED SURFACE-EMITTING METALLIC NANOCAVITY WITH MULTIPLE QUANTUM WELL
(2014-01-01)
Chou, Bo-Tsun
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Lin, Sheng-Di
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交大名義發表
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National Chiao Tung University
We design an electrically-injected surface-emitting laser with metallic nanocavity aiming for near infrared regime. Our calculation shows that threshold gain and effective mode volume of the TE01 mode could achieve 2711 cm(-1) and 0.014 lambda(3)(0), respectively.
Design of Bottom-Emitting Metallic Nanolasers Integrated With Silicon-On-Insulator Waveguides
(2015-05-15)
Chou, Bo-Tsun
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Lu, Tien-Chang
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Lin, Sheng-Di
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交大名義發表
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National Chiao Tung University
We propose and analyze a bottom-emitting metallic nanolaser with a cavity size smaller than one wavelength in three dimensions. We optimize the nanolaser performance by adjusting the thickness of SiNx insulator layer, pillar radius, p-cladding, and n-cladding layers. With a proper design, we can achieve the TE01 mode lasing with an extremely small effective mode volume of 0.135 (lambda(0) /n)(3) and an ultra low threshold gain of 247 cm(-1). The nanolaser is integrated with a silicon-on-insulator waveguide through a bottom-connected grating coupler. By properly modifying the grating coupler period, fill factor, shift position, and grating height, a high coupling efficiency of 88.5% can be acquired.
High-operation-temperature Aluminum-based SPP Nanolasers
(2016)
Chou, Yu-Hsun
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Hong, Kuo-Bin
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Chou, Bo-Tsun
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Wu, Yen-Mo
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Shih, Jheng-Hong
Metal-insulator-semiconductor structures has widely adopted in plasmonics lasers. However, we found that the insulator is not necessary if permittivity combination of laser structures is properly designed. Single-mode laser operation was demonstrate in devices without artificial insulator layers. Moreover, the operation temperature can achieve to 353 K.
High-Operation-Temperature Plasmonic Nanolasers on Single-Crystalline Aluminum
(2016-05)
Chou, Yu-Hsun
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Wu, Yen-Mo
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Hong, Kuo-Bin
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Chou, Bo-Tsun
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Shih, Jheng-Hong
The recent development of plasmonics has overcome the optical diffraction limit and fostered the development of several important components including nanolasers, low-operation-power modulators, and high-speed detectors. In particular, the advent of surface-plasmon-polariton (SPP) nanolasers has enabled the development of coherent emitters approaching the nanoscale. SPP nanolasers widely adopted metal insulator semiconductor structures because the presence of an insulator can prevent large metal loss. However, the insulator is not necessary if permittivity combination of laser structures is properly designed. Here, we experimentally demonstrate a SPP nanolaser with a ZnO nanowire on the as-grown single-crystalline aluminum. The average lasing threshold of this simple structure is 20 MW/cm(2), which is four-times lower than that of structures with additional insulator layers. Furthermore, single-mode laser operation can be sustained at temperatures up to 353 K. Our study represents a major step toward the practical realization of SPP nanolasers.
High-Performance Plasmonic Nanolasers with a Nanotrench Defect Cavity for Sensing Applications
(2018-07-01)
Cheng, Pi-Ju
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Huang, Zhen-Ting
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Li, Jhu-Hong
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Chou, Bo-Tsun
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Chou, Yu-Hsun
Recent developments in small footprint plasmonic nanolasers show promise for active optical sensing with potential applications in various fields, including real-time and label-free biochemical sensing, and gas detection. In this study, we demonstrate a novel hybrid plasmonic crystal nanolaser that features a ZnO nanowire placed on Al grating surfaces with a nanotrench defect nanocavity. The lasing action of gain-assisted defect nanocavity overcomes the ohmic loss parasitically in the plasmonic nanostructures. Therefore, the plasmonic nanolaser exhibits an extremely small mode volume, a narrow linewidth Delta lambda, and a high Purcell factor that can facilitate the strong interaction between light and matter. This can be used as a refractive index sensor and is highly sensitive to local changes in the refractive indices of ambient materials. By careful design, the near-ultraviolet nanolaser sensors have significant sensing performances of glucose solutions, revealing a high sensitivity of 249 nm/RIU and high resolution, with a figure of merit of 1132, at the resonant wavelength of 373 nm.
Metal for Plasmonic Ultraviolet Laser: Al or Ag?
(2017-11-01)
Chou, Yu-Hsun
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Hong, Kuo-Bin
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Chung, Yi-Cheng
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Chang, Chun-Tse
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Chou, Bo-Tsun
Surface plasmon polariton (SPP) nanolasers have recently emerged as promising candidates for generating a coherent light source in nanophotonic integration circuits. The properties of SPP nanolasers, such as group velocity, mode area, modulation speed, and threshold performance, can be manipulated using a dispersion relation. In this study, we investigated the characteristics of SPP nanolasers operated near and far from the SP frequency. Our results indicated that SPP nanolaser performance can be significantly influenced by manipulating the dispersion relation.
Realization of UV Plasmonic Nanolasers With Extremely Small Mode Volume
(2015-11-01)
Chou, Bo-Tsun
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Chou, Yu-Hsun
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Chiang, Chih-Kai
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Wu, Yen-Mo
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Lin, Tzy-Rong
It is difficult to operate plasmonic nanolasers on silver films in the ultraviolet regime owing to the bending-back effect of surface plasmon dispersion. In this paper, we report on plasmonic lasers comprised of a ZnO nanowire lying on a single-crystalline silver film with a SiO2 spacer layer. The silver can strongly shrink the mode volume, thereby boosting the Purcell factor. Meanwhile, the SiO2 spacer thickness is optimized to adjust the surface plasmon dispersion curve so that the lasing wavelength can be located at a large dispersion region, thereby achieving a large group index of 55, an ultra-small effective mode volume of 3.5 x 10(-3)lambda(3), and low-threshold of 11 MW/cm(2).
Single-crystalline aluminum film for ultraviolet plasmonic nanolasers
(2016-01-27)
Chou, Bo-Tsun
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Chou, Yu-Hsun
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Wu, Yen-Mo
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Chung, Yi-Cheng
;
Hsueh, Wei-Jen
Significant advances have been made in the development of plasmonic devices in the past decade. Plasmonic nanolasers, which display interesting properties, have come to play an important role in biomedicine, chemical sensors, information technology, and optical integrated circuits. However, nanoscale plasmonic devices, particularly those operating in the ultraviolet regime, are extremely sensitive to the metal and interface quality. Thus, these factors have a significant bearing on the development of ultraviolet plasmonic devices. Here, by addressing these material-related issues, we demonstrate a low-threshold, high-characteristic-temperature metal-oxide-semiconductor ZnO nanolaser that operates at room temperature. The template for the ZnO nanowires consists of a flat single-crystalline Al film grown by molecular beam epitaxy and an ultrasmooth Al2O3 spacer layer synthesized by atomic layer deposition. By effectively reducing the surface plasmon scattering and metal intrinsic absorption losses, the high-quality metal film and the sharp interfaces formed between the layers boost the device performance. This work should pave the way for the use of ultraviolet plasmonic nanolasers and related devices in a wider range of applications.
Single-Crystalline Aluminum Nanostructures on a Semiconducting GaAs Substrate for Ultraviolet to Near-Infrared Plasmonics
(2015-04-01)
Liu, Hsuan-Wei
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Lin, Fan-Cheng
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Lin, Shi-Wei
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Wu, Jau-Yang
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Chou, Bo-Tsun
Aluminum, as a metallic material for plasmonics, is of great interest because it extends the applications of surface plasmon resonance into the ultraviolet (UV) region and is superior to noble metals in natural abundance, cost, and compatibility with modern semiconductor fabrication processes. Ultrasmooth single-crystalline metallic films are beneficial for the fabrication of high-definition plasmonic nanostructures, especially complex integrated nanocircuits. The absence of surface corrugation and crystal boundaries also guarantees superior optical properties and applications in nanolasers. Here, we present UV to near-infrared plasmonic resonance of single-crystalline aluminum nanoslits and nanoholes. The high-definition nanostructures are fabricated with focused ion-beam milling into an ultrasmooth single-crystalline aluminum film grown on a semiconducting GaAs substrate with a molecular beam epitaxy method. The single-crystalline aluminum film shows improved reflectivity and reduced two-photon photoluminescence (TPPL) due to the ultrasmooth surface. Both linear scattering and nonlinear TPPL are studied in detail. The nanoslit arrays show clear Fano-like resonance, and the nanoholes are found to support both photonic modes and localized surface plasmon resonance. We also found that TPPL generation is more efficient when the excitation polarization is parallel rather than perpendicular to the edge of the aluminum film. Such a counterintuitive phenomenon is attributed to the high refractive index of the GaAs substrate. We show that the polarization of TPPL from aluminum preserves the excitation polarization and is independent of the crystal orientation of the film or substrate. Our study gains insight into the optical property of aluminum nanostructures on a high-index semiconducting GaAs substrate and illustrates a practical route to implement plasmonic devices onto semiconductors for future hybrid nanodevices.
Single-crystalline silver film grown on Si (100) substrate by using electron-gun evaporation and thermal treatment
(2014-05-01)
Chou, Bo-Tsun
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Lin, Sheng-Di
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Huang, Bo-Hao
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Lu, Tien-Chang
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電子工程學系及電子研究所
The authors demonstrate a simple method to fabricate ultrasmooth single-crystalline silver (Ag) films with high reflectivity and low plasmonic damping. The single-crystalline Ag thin film on the clean Si (100) substrate is first deposited by electron-gun evaporator and then treated by rapid thermal annealing (RTA) to improve its quality. The crystal structure and surface morphology are characterized by x-ray diffraction, transmission electron microscopy, and atomic force microscopy. Optical constants of the prepared films are extracted by fitting the measured reflectivity spectra with the Drude model. These results show that the Ag film with 340 degrees C RTA has the best film quality, including small surface roughness of 0.46 nm, a sharp x-ray diffraction peak with FWHM of 0.3 degrees, and lowest damping in the visible and near-infrared wavelength regime. Therefore, our method is not only cost-effective but also useful for fabricating metal-based plasmonic and nanophotonic devices. (C) 2014 American Vacuum Society.
Surface roughness effects on aluminium-based ultraviolet plasmonic nanolasers
(2017-01-03)
Chung, Yi-Cheng
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Cheng, Pi-Ju
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Chou, Yu-Hsun
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Chou, Bo-Tsun
;
Hong, Kuo-Bin
We systematically investigate the effects of surface roughness on the characteristics of ultraviolet zinc oxide plasmonic nanolasers fabricated on aluminium films with two different degrees of surface roughness. We demonstrate that the effective dielectric functions of aluminium interfaces with distinct roughness can be analysed from reflectivity measurements. By considering the scattering losses, including Rayleigh scattering, electron scattering, and grain boundary scattering, we adopt the modified Drude-Lorentz model to describe the scattering effect caused by surface roughness and obtain the effective dielectric functions of different Al samples. The sample with higher surface roughness induces more electron scattering and light scattering for SPP modes, leading to a higher threshold gain for the plasmonic nanolaser. By considering the pumping efficiency, our theoretical analysis shows that diminishing the detrimental optical losses caused by the roughness of the metallic interface could effectively lower (-33.1%) the pumping threshold of the plasmonic nanolasers, which is consistent with the experimental results.
Ultrastrong Mode Confinement in ZnO Surface Plasmon Nanolasers
(2015-04-01)
Chou, Yu-Hsun
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Chou, Bo-Tsun
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Chiang, Chih-Kai
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Lai, Ying-Yu
;
Yang, Chun-Ting
Nano lasers with an ultracompact footprint can provide high-intensity coherent light, which can be potentially applied to high-capacity signal processing, biosensing, and subwavelength imaging. Among various nanolasers, those with cavities surrounded by metals have been shown to have superior light emission properties because of the surface plasmon effect that provides enhanced field confinement capability and enables exotic light matter interaction. In this study, we demonstrated a robust ultraviolet ZnO nanolaser that can operate at room temperature by using silver to dramatically shrink the mode volume. The nanolaser shows several distinct features including an extremely small mode volume, a large Purcell factor, and a slow group velocity, which ensures strong interaction with the exciton in the nanowire.
Ultraviolet Lasing in a ZnO Plasmonic Nanolaser
(2014)
Chou, Yu-Hsun
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Chou, Bo-Tsun
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Lai, Ying-Yu
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Yang, Chun-Ting
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Chiang, Chih-Kai
We report on the demonstration of a sub-diffraction-limited plasmonic laser at UV region by using the ZnO nanowire based on the semiconductor-insulator-metal (SIM) structure. At 77K, the laser with a threshold power of about 76MW/cm(2) and the wavelength of 373 nm with an extremely small mode area below lambda(2)/1000 was realized.