Browsing by Author "Lu, Tien-chang"

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Characteristics of GaN-based photonic crystal surface emitting lasers
(2008-09-15)
Lu, Tien-chang
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Chen, Shih-Wei
;
Kao, Tsung-Ting
;
Liu, Tzu-Wei
;
光電工程學系
Characteristics of GaN-based photonic crystal surface emitting lasers (PCSELs) were investigated and analyzed. The GaN-based PCSEL emits a blue wavelength at 401.8 nm with a linewidth of 1.6 angstrom and shows a threshold energy density about 2.7 mJ/cm(2) under the optical pumping at room temperature. The lasing wavelength emitted from PCSELs with different lattice constants occurs at the calculated band edges showing different polarization angles due to the light diffracted in specific directions, corresponding exactly to Gamma, K, and M directions in the K-space. Furthermore, the PCSEL also shows a spontaneous emission coupling efficiency beta of about 5 X 10(-3) and a characteristic temperature of 148 K. (C) 2008 American Institute of Physics.
Emission Characteristics of InGaN/GaN Vertical-Cavity Surface-Emitting Lasers
(2007)
Chu, Jung-Tang
;
Lu, Tien-chang
;
Kuo, Hao-Chung
;
Wang, Shing-Chung
;
光電工程學系
Lasing characteristics of optically pumped GaN-based vertical-cavity surface-emitting lasers were investigated. The laser emission showed single and multiple spots emission patterns with spectral and spatial variation under different pumping conditions. (C) 2007 Optical Society of America
Graphene-Loaded Plasmonic Zirconium Nitride and Gold Nanogroove Arrays for Surface-Charge Modifications
(2020-06-26)
Yu, Min-Wen
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Ishii, Satoshi
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Ku, Ji-Ren
;
Yang, Jhen-Hong
;
Huang, Chih-Hsiang
Graphene-on-metal (G/M) heterostructures have gained considerable attention in recent years owing to their outstanding optical and electrical properties. In this study, the polarity of graphene doping to different metallic materials underneath graphene is analyzed for applications in surface-charge modifications. Kelvin probe force microscopy clearly reveals the charge-transfer effects of plasmonic zirconium nitride (ZrN) and gold (Au) on the formation of G/M heterostructures. In addition, both ZrN and Au nanogroove arrays are fabricated by focused ion beam to generate surface plasmon resonances. The charge-transfer effects influence the effective permittivities of ZrN and Au surfaces such that opposite plasmonic resonance shifts are demonstrated for the ZrN and Au nanogroove arrays. Our results show that the choice of metallic material is important for achieving a desired charge transfer in the loading of graphene onto metallic materials.
Inverted Octagonal Surface Defects in a-Plane AlGaN/GaN Multiple Quantum Wells
(2011)
Huang, Huei-min
;
Chang, Chiao-yun
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Lu, Tien-chang
;
Yang, Chi-chin
;
光電工程學系
The structural properties of a-plane AlGaN/GaN multiple quantum wells grown on the r-plane sapphire substrate have been characterized. The pentagonal and inverted octagonal surface pits, consisting of several non-polar and semi-polar crystalline facets, are clearly observed and distinguished. The Al incorporation efficiency of the non-polar and semi-polar facets of these special inverted octagonal surface pits has been verified in the order of (11 (2) under bar2) < (10<(12)under bar>) < (1<(1)under bar>00) approximate to (11 (2) under bar0) < (20<(2)under bar>1) by cathodoluminescence measurements at room temperature. The evolution of these inverted octagonal surface pits could be due to the results of interaction between different stacking faults. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3610990] All rights reserved.
Perfect Absorption by an Atomically Thin Crystal
(2020-08-05)
Horng, Jason
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Martin, Eric W.
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Chou, Yu-Hsun
;
Courtade, Emmanuel
;
Chang, Tsu-chi
Optical absorption is one of the most fundamental processes in light-matter interactions. The ability to achieve and control high absorption is crucial for a broad range of modern photonic technologies. In nanomaterials of length scales much smaller than a wavelength, optical absorption is typically a weak perturbation. To achieve high absorption, exquisite techniques and structures have been developed, such as coherent interference of multiple laser beams and plasmonic metasurfaces. Here, we show that a robust critical-coupling condition exists to allow perfect absorption of light by a subnanometer-thick two-dimensional semiconductor, when the radiative-decay rate of the exciton resonance balances with its loss rate. We measure an absorption up to 99.6% in a monomolecular MoSe2 crystal placed in front of a flat mirror. We furthermore demonstrate control of the perfect absorption by tuning the exciton-phonon, exciton-exciton, and exciton-photon interactions with temperature, pulsed laser excitation, and a movable mirror, respectively. Our work suggests a mechanism to achieve and control critical coupling in two-dimensional excitonic systems, enabling photonic applications including ultrafast low-power light modulators and sensitive optical sensing.
Photonic integrated multiwavelength laser arrays: Recent progress and perspectives
(2020-05-04)
Lee, San-Liang
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Lu, Tien-chang
;
Hung, Yung-, Jr.
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Chen, Lih-Ren
;
Huang, Zhen-Ting
With the significant technology advancement in photonic integration and the demands of compact light sources of multiple wavelengths, multiwavelength laser arrays (MWLAs) can play important roles in high-capacity optical signal transmission, photonic switching, and optical sensing. Manufacturing with semiconductor foundries and the integration with electronic integrated circuits bring not only advanced technologies but also new concepts for realizing MWLAs. This paper will first overview the existing technology development and then discuss the challenges and possible solutions for enabling photonic-integrated MWLAs. The overview will cover monolithically and hybrid-integrated MWLAs. The wavelength registration for both in-plane and vertical-cavity MWLAs will be discussed and compared.
Progress and prospects of GaN-based VCSEL from near UV to green emission
(2018-01-01)
Yu, Hsin-chieh
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Zheng, Zhi-wei
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Mei, Yang
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Xu, Rong-bin
;
Liu, Jian-ping
GaN is a great material for making optoelectronic devices in the blue, blue-violet and green bands. Vertical-cavity surface-emitting lasers (VCSELs) have many advantages including small footprint, circular symmetry of output beam, two-dimensional scalability and/or addressability, surface mount packaging, good price-performance ratio, and simple optics/alignment for output coupling. In this paper, we would like to (1) Review the design and fabrication of GaN-based VCSELs including some technology challenges, (2) Discuss the design and metalorganic chemical vapor deposition (MOCVD) growth of electrically pumped blue VCSELs and (3) Demonstrate world first green VCSEL using quantum dots (QDs) active region to overcome the 'green gap'.