Browsing by Author "Kuo, Hao-Chung"

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4 Tunability and Optimization of Coupling Efficiency in Tamm Plasmon Modes
(2015-07-01)
Chang, Che-Yuan
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Chen, Yi-Hsuan
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Tsai, Yu-Lin
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Kuo, Hao-Chung
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Chen, Kuo-Ping
A Tamm plasmon polariton is a plasmonic resonance excited at the boundary between a photonic crystal and a metal. In this paper, a novel approach based on admittance loci is proposed to demonstrate the relation between thin-film structures and the corresponding Tamm plasmon modes. The tunability of the resonance wavelength and optimization of coupling efficiency are demonstrated. In addition, by using different metals to couple Tamm plasmon modes in the visible spectrum, silver has 4.7 times larger Q-factor than gold and 84 times larger than aluminum at 700 nm. The near-field enhancement of silver Tamm plasmon modes could be up to eight times larger than incident EM waves.
4-Gbit/s visible light communication link based on 16-QAM OFDM transmission over remote phosphor-film converted white light by using blue laser diode
(2015-12-28)
Retamal, Jose Ramon Duran
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Oubei, Hassan Makine
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Janjua, Bilal
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Chi, Yu-Chieh
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Wang, Huai-Yung
Visible Light Communication (VLC) as a new technology for ultrahigh-speed communication is still limited when using slow modulation light-emitting diode (LED). Alternatively, we present a 4-Gbit/s VLC system using coherent blue-laser diode (LD) via 16-quadrature amplitude modulation orthogonal frequency division multiplexing. By changing the composition and the optical-configuration of a remote phosphor-film the generated white light is tuned from cool day to neutral, and the bit error rate is optimized from 1.9 x 10(-2) to 2.8 x 10(-5) in a blue filter-free link due to enhanced blue light transmission in forward direction. Briefly, blue-LD is an alternative to LED for generating white light and boosting the data rate of VLC. (C) 2015 Optical Society of America
4-Gbit/s visible light communication link based on 16-QAM OFDM transmission over remote phosphor-film converted white light by using blue laser diode
(2015-12-28)
Retamal, Jose Ramon Duran
;
Oubei, Hassan Makine
;
Janjua, Bilal
;
Chi, Yu-Chieh
;
Wang, Huai-Yung
Visible Light Communication (VLC) as a new technology for ultrahigh-speed communication is still limited when using slow modulation light-emitting diode (LED). Alternatively, we present a 4-Gbit/s VLC system using coherent blue-laser diode (LD) via 16-quadrature amplitude modulation orthogonal frequency division multiplexing. By changing the composition and the optical-configuration of a remote phosphor-film the generated white light is tuned from cool day to neutral, and the bit error rate is optimized from 1.9 x 10(-2) to 2.8 x 10(-5) in a blue filter-free link due to enhanced blue light transmission in forward direction. Briefly, blue-LD is an alternative to LED for generating white light and boosting the data rate of VLC. (C) 2015 Optical Society of America
4.8 Gbit/s 16-QAM-OFDM transmission based on compact 450-nm laser for underwater wireless optical communication
(2015-09-07)
Oubei, Hassan M.
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Duran, Jose R.
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Janjua, Bilal
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Wang, Huai-Yung
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Tsai, Cheng-Ting
We experimentally demonstrate an underwater wireless optical communications (UWOC) employing 450-nm TO-9 packaged and fiber-pigtailed laser diode (LD) directly encoded with an orthogonal frequency division multiplexed quadrature amplitude modulation (QAM-OFDM) data. A record data rate of up to 4.8 Gbit/s over 5.4-m transmission distance is achieved. By encoding the full 1.2-GHz bandwidth of the 450-nm LD with a 16-QAM-OFDM data, an error vector magnitude (EVM) of 16.5%, a signal-to-noise ratio (SNR) of 15.63 dB and a bit error rate (BER) of 2.6 x 10-3, well pass the forward error correction (FEC) criterion, were obtained. (C) 2015 Optical Society of America
450-nm GaN laser diode enables high-speed visible light communication with 9-Gbps QAM-OFDM
(2015-05-18)
Chi, Yu-Chieh
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Hsieh, Dan-Hua
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Tsai, Cheng-Ting
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Chen, Hsiang-Yu
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Kuo, Hao-Chung
A TO-38-can packaged Gallium nitride (GaN) blue laser diode (LD) based free-space visible light communication (VLC) with 64-quadrature amplitude modulation (QAM) and 32-subcarrier orthogonal frequency division multiplexing (OFDM) transmission at 9 Gbps is preliminarily demonstrated over a 5-m free-space link. The 3-dB analog modulation bandwidth of the TO-38-can packaged GaN blue LD biased at 65 mA and controlled at 25 degrees C is only 900 MHz, which can be extended to 1.5 GHz for OFDM encoding after throughput intensity optimization. When delivering the 4-Gbps 16-QAM OFDM data within 1-GHz bandwidth, the error vector magnitude (EVM), signal-to-noise ratio (SNR) and bit-error-rate (BER) of the received data are observed as 8.4%, 22.4 dB and 3.5 x 10(-8), respectively. By increasing the encoded bandwidth to 1.5 GHz, the TO-38-can packaged GaN blue LD enlarges its transmission capacity to 6 Gbps but degrades its transmitted BER to 1.7 x 10(-3). The same transmission capacity of 6 Gbps can also be achieved with a BER of 1 x 10(-6) by encoding 64-QAM OFDM data within 1-GHz bandwidth. Using the 1.5-GHz full bandwidth of the TO-38-can packaged GaN blue LD provides the 64-QAM OFDM transmission up to 9 Gbps, which successfully delivers data with an EVM of 5.1%, an SNR of 22 dB and a BER of 3.6 x 10(-3) passed the forward error correction (FEC) criterion. (C) 2015 Optical Society of America
850-nm VCSELs With p-Type delta-Doping in the Active Layers for Improved High-Speed and High-Temperature Performance
(2016-11)
Chi, Kai-Lun
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Hsieh, Dan-Hua
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Yen, Jia-Liang
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Chen, Xin-Nan
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Chen, Jason (Jyehong)
In this paper, we study the influence of p-type modulation doping on the dynamic/static performance of highspeed 850-nm VCSELs with highly strained multiple quantum wells. The studied device structure has a 3/2 lambda asymmetric cavity design, which can let the internal transit time of injected carriers be as short as that of 1/2 lambda cavity design and further improve its performance in terms of speed and output power for high single-mode operation. Our proposed VCSEL structure with p-type doping shows superior modulation speed with an output power comparable with that of the un-doped reference device under room temperature operation. Furthermore, when the operating temperature reaches 85 degrees C, there is a significant improvement in both the modulation speed and maximum power of the p-doped structures. According to our simulation, this can be attributed to the change in the quasi-Fermi levels of the injected carriers after the addition of p-doping in the active layers, which minimizes the electron leakage under high-temperature operation.
850/940-nm VCSEL for optical communication and 3D sensing
(2018-01-01)
Cheng, Chih-Hsien
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Shen, Chih-Chiang
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Kao, Hsuan-Yun
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Hsieh, Dan-Hua
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Wang, Huai-Yung
This paper is going to review the state-of-the-art of the high-speed 850/940-nm vertical cavity surface emitting laser (VCSEL), discussing the structural design, mode control and the related data transmission performance. InGaAs/AlGaAs multiple quantum well (MQW) was used to increase the differential gain and photon density in VCSEL. The multiple oxide layers and oxide-confined aperture were well designed in VCSEL to decrease the parasitic capacitance and generate single mode (SM) VCSEL. The maximal modulation bandwidth of 30 GHz was achieved with well-designed VCSEL structure. At the end of the paper, other applications of the near-infrared VCSELs are discussed.
A Comprehensive Study of One-Step Selenization Process for Cu(In1-xGax) Se-2 Thin Film Solar Cells
(2017-03-21)
Chen, Shih-Chen
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Wang, Sheng-Wen
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Kuo, Shou-Yi
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Juang, Jenh-Yih
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Lee, Po-Tsung
In this work, aiming at developing a rapid and environmental-friendly process for fabricating CuIn1-xGaxSe2 (CIGS) solar cells, we demonstrated the one-step selenization process by using selenium vapor as the atmospheric gas instead of the commonly used H2Se gas. The photoluminescence (PL) characteristics indicate that there exists an optimal location with superior crystalline quality in the CIGS thin films obtained by one-step selenization. The energy dispersive spectroscopy (EDS) reveals that the Ga lateral distribution in the one-step selenized CIGS thin film is intimately correlated to the blue-shifted PL spectra. The surface morphologies examined by scanning electron microscope (SEM) further suggested that voids and binary phase commonly existing in CIGS films could be successfully eliminated by the present one-step selenization process. The agglomeration phenomenon attributable to the formation of MoSe2 layer was also observed. Due to the significant microstructural improvement, the current-voltage (J-V) characteristics and external quantum efficiency (EQE) of the devices made of the present CIGS films have exhibited the remarkable carrier transportation characteristics and photon utilization at the optimal location, resulting in a high conversion efficiency of 11.28%. Correlations between the defect states and device performance of the one-step selenized CIGS thin film were convincingly delineated by femtosecond pump-probe spectroscopy.
A critical review on two-dimensional quantum dots (2D QDs): From synthesis toward applications in energy and optoelectronics
(2019-11-01)
Manikandan, Arumugam
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Chen, Yu-Ze
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Shen, Chih-Chiang
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Sher, Chin-Wei
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Kuo, Hao-Chung
Recent advances in the development of quantum dots (QDs) have offered new possibilities for the exploration of sensors, bio imaging, batteries, electrochemical water splitting and optoelectronic applications because of their intriguing optical, electrical, catalytic and electrochemical properties. Among QDs, atomically thin two-dimensional quantum dots (2D QDs) derived from graphene sheets, transition metal dichalcogenide (TMD) layers and phosphorene have been of considerable interest for the past few years. There have been several intensive studies of carbon QDs, but TMD QDs and heterostructures based on 2D QDs are rapidly advancing. Herein, the synthesis and properties of 2D QDs, particularly carbon and TMD QDs, are reviewed for the recent progress in their application toward electrochemical water splitting, photocatalytic wastewater treatment, supercapacitors, batteries and photodetectors. Moreover, the assembly of such 2D QDs to achieve industrial-scale production and boost their performance in widespread applications is emphasized.
A high quality liquid-type quantum dot white light-emitting diode
(2016-01-01)
Sher, Chin-Wei
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Lin, Chin-Hao
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Lin, Huang-Yu
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Lin, Chien-Chung
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Huang, Che-Hsuan
This study demonstrates a novel package design to store colloidal quantum dots in liquid format and integrate them with a standard LED. The high efficiency and high quality color performance at a neutral white correlated color temperature is demonstrated. The experimental results indicate that the liquid-type quantum dot white light-emitting diode (LQD WLED) is highly efficient and reliable. The luminous efficiency and color rendering index (CRI) of the LQD WLED can reach 271 lm W-op(-1) and 95, respectively. Moreover, a glass box is employed to prevent humidity and oxygen erosion. With this encapsulation design, our quantum dot box can survive over 1000 hours of storage time.
A high quality liquid-type quantum dot white light-emitting diode (vol 8, pg 1117, 2016)
(2018-04-07)
Sher, Chin-Wei
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Lin, Chih-Hao
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Lin, Huang-Yu
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Lin, Chien-Chung
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Huang, Che-Hsuan
A Highly Efficient Hybrid GaAs Solar Cell Based on Colloidal-Quantum-Dot-Sensitization
(2014-07-18)
Han, Hau-Vei
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Lin, Chien-Chung
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Tsai, Yu-Lin
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Chen, Hsin-Chu
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Chen, Kuo-Ju
This paper presents a hybrid design, featuring a traditional GaAs-based solar cell combined with various colloidal quantum dots. This hybrid design effectively boosts photon harvesting at long wavelengths while enhancing the collection of photogenerated carriers in the ultraviolet region. The merits of using highly efficient semiconductor solar cells and colloidal quantum dots were seamlessly combined to increase overall power conversion efficiency. Several photovoltaic parameters, including short-circuit current density, open circuit voltage, and external quantum efficiency, were measured and analyzed to investigate the performance of this hybrid device. Offering antireflective features at long wavelengths and luminescent downshifting for high-energy photons, the quantum dots effectively enhanced overall power conversion efficiency by as high as 24.65% compared with traditional GaAs-based devices. The evolution of weighted reflectance as a function of the dilution factor of QDs was investigated. Further analysis of the quantum efficiency response showed that the luminescent downshifting effect can be as much as 6.6% of the entire enhancement of photogenerated current.
A Light Guide Plate That Uses Asymmetric Intensity Distribution of Mini-LEDs for the Planar Illuminator
(2019-03-08)
Ye, Zhi-Ting
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Pai, Yung-Min
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Chen, Cheng-Huan
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Kuo, Hao-Chung
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Chen, Lung-Chien
Traditional backlights are designed with new dot patterns, and then injection molding, laser beam fabrication, or UV (Ultraviolet) roll-to-plate imprinting is used to apply dot patterns to a light guide plate-the process consumes considerable time and resources. Therefore, we propose a novel light guide design that does not use a dot pattern. We designed an asymmetric intensity distribution of mini-LEDs (Light Emitting Diode) and a light guide plate with a fully printed diffusion reflection on the bottom surface for a planar illuminator. The design rules for the proposed architecture are described in this paper. The archetype design with a 152.4 mm circular down-light has a diameter of 143 mm for the planar light source module. The experiment achieved a total efficiency of 85% and uniformity of 92.6%.
A look into the origin of shunt leakage current of Cu(In,Ga)Se-2 solar cells via experimental and simulation methods
(2013-10-01)
Liao, Yu-Kuang
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Kuo, Shou-Yi
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Hsieh, Ming-Yang
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Lai, Fang-I
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Kao, Ming-Hsuan
This study investigates how to apply space-charge-limited (SCL) current to describe shunt leakage current in a CIGS solar cell. Possible factors inducing SCL current have been observed through conductive atomic force microscopy (C-AFM), which supports the SCL current theory, describing the shunt current of a CIGS solar cell. In simulations derived from experimental data, deviation of dark IV curves is due to flaws in the real device. These flaws are absent in simulation, but investigation verifies the characteristics of SCL current component's experimental IV curves within shunt leakage current. A device with a metal/CIGS/metal structure could simulate SCL current and confirm its characteristics. Such a simulated structure, representing flaws inserted into a CIGS solar cell, generates the same dark-current behavior revealed in experimental dark IV curves. This study investigates the response of dark current to varying sizes of the flaw within the CIGS solar cell. (C) 2013 Elsevier B.V. All rights reserved.
A Novel Liquid Packaging Structure of Deep-Ultraviolet Light-Emitting Diodes to Enhance the Light-Extraction Efficiency
(2019-04-01)
Kang, Chieh-Yu
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Lin, Chih-Hao
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Wu, Tingzhu
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Lee, Po-Tsung
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Chen, Zhong
To realize high-efficiency, AlGaN-based, deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency and reducing thermal resistance is very crucial. We proposed a liquid packaging structure that could enhance optical power by 27.2% and 70.7% for flat type and lens type 281-nm DUV-LEDs, respectively. A significant improvement effect at different wavelengths, such as 268 nm and 310 nm, was also observed. Furthermore, using the liquid packaging structure, the thermal resistance was reduced by 30.3% compared to the conventional structure. Finally, the reliability of liquid packaging DUV-LEDs was tested. The light output maintenance of liquid packaging DUV-LEDs was compared to the conventional structure.
A pulsated weak-resonant-cavity laser diode with transient wavelength scanning and tracking for injection-locked RZ transmission
(2012-06-18)
Lin, Gong-Ru
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Chi, Yu-Chieh
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Liao, Yu-Sheng
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Kuo, Hao-Chung
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Liao, Zhi-Wang
By spectrally slicing a single longitudinal-mode from a master weak-resonant-cavity Fabry-Perot laser diode with transient wavelength scanning and tracking functions, the broadened self-injection-locking of a slave weak-resonant-cavity Fabry-Perot laser diode is demonstrated to achieve bi-directional transmission in a 200-GHz array-waveguide-grating channelized dense-wavelength-division-multiplexing passive optical network system. Both the down-and up-stream slave weak-resonant-cavity Fabry-Perot laser diodes are non-return-to-zero modulated below threshold and coherently injection-locked to deliver the pulsed carrier for 25-km bidirectional 2.5 Gbits/s return-to-zero transmission. The master weak-resonant-cavity Fabry-Perot laser diode is gain-switched at near threshold condition and delivers an optical coherent pulse-train with its mode linewidth broadened from 0.2 to 0.8 nm by transient wavelength scanning, which facilitates the broadband injection-locking of the slave weak-resonant-cavity Fabry-Perot laser diodes with a threshold current reducing by 10 mA. Such a transient wavelength scanning induced spectral broadening greatly releases the limitation on wavelength injection-locking range required for the slave weak-resonant-cavity Fabry-Perot laser diode. The theoretical modeling and numerical simulation on the wavelength scanning and tracking effects of the master and slave weak-resonant-cavity Fabry-Perot laser diodes are performed. The receiving power sensitivity for back-to-back transmission at bit-error-rate <10(-10) is -25.6 dBm, and the power penalty added after 25-km transmission is less than 2 dB for all 16 channels. (C) 2012 Optical Society of America
A simple model for cavity enhanced slow lights in vertical cavity surface emission lasers
(2008-04-01)
Chou, Chia-Sheng
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Lee, Ray-Kuang
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Peng, Peng-Chun
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Kuo, Hao-Chung
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Lin, Gray
We develop a simple model for the slow lights in vertical cavity surface emission lasers (VCSELs), with the combination of cavity and population pulsation effects. The dependences of probe signal power, injection bias current and wavelength detuning for the group delays are demonstrated numerically and experimentally. Up to 65 ps group delays and up to 10 GHz modulation frequency can be achieved at room temperature at a wavelength of 1.3 mu m. The most significant feature of our VCSEL device is that the thickness of the active region is only several micrometers long. Based on the experimental parameters of quantum dot VCSEL structures, we show that the resonance effect of the laser cavity plays a significant role in enhancing the group delays.
A Single InN Nanopillar Photodetector with Extended Infrared Response Grown by MOCVD
(2016)
Hsu, Lung-Hsing
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Kuo, Chien-Ting
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Cheng, Yuh-Jen
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Chen, Kuan-Chao
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Kuo, Hao-Chung
An extended infrared photoresponse is observed in a high quality InN pillar/p-GaN photodetector with self-assembly epitaxy grown by LP-MOCVD. The IR portion photocurrent as high as 14.2% can be measured via AM1.5G solar simulated spectra.
A Special Section on Flexible Solar Cells
(2017-08-01)
Chen, Lung-Chien
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Cheong, Kuan Yew
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Kuo, Hao-Chung
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Yang, Shengyi
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光電工程學系
A star-ring-bus architecture for WDM fiber-wireless system
(2006-01-01)
Chiou, Hung-Yu
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Peng, Peng-Chun
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Feng, Kai-Ming
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Peng, Wei-Ren
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Chen, JyeHong
A self-healing star-ring-bus architecture for high-capacity WDM fiber-wireless system is proposed and verified experimentally. This architecture can provide reliable, flexible, and robust characteristics for large radio terminals. (C) 2006 Optical Society of America.