Browsing by Author "Lee, Po-Tsung"

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1D photonic crystal strain sensors
(2018-07-01)
Lu, Tsan-Wen
;
Wu, Chia-Cheng
;
Lee, Po-Tsung
;
光電工程學系
;
Department of Photonics
We introduce a photonic crystal nanocavity consisting of one-dimensional periodic nanorods embedded in a deformable polydimethylsiloxane substrate, which exhibits a high-quality factor and a large wavelength response to the applied strain. By further investigating its wavelength response to nonaxial planar strains, we propose and experimentally demonstrate a sensor unit that can precisely identify different planar strains, including their application direction, type, and value. This sensor prototype with small footprint and feasible coupling with optical waveguides could provide additional flexibility for strain analysis in a wide range of fields.
850/940-nm VCSEL for optical communication and 3D sensing
(2018-01-01)
Cheng, Chih-Hsien
;
Shen, Chih-Chiang
;
Kao, Hsuan-Yun
;
Hsieh, Dan-Hua
;
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
;
Juang, Jenh-Yih
;
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 flexible organic pentacene nonvolatile memory based on high-kappa dielectric layers
(2008-12-08)
Chang, Ming-Feng
;
Lee, Po-Tsung
;
McAlister, S. P.
;
Chin, Albert
;
電子工程學系及電子研究所
We report a pentacene thin film transistor nonvolatile memory fabricated on a flexible polyimide substrate. This device shows a low program/erase voltage of 12 V, a speed of 1/100 ms, an initial memory window of 2.4 V, and a 0.78 V memory window after 48 h. This has been achieved by using a high-kappa dielectric as charge trapping, blocking, and tunneling gate insulator layers.
A Metal-Insulator-Semiconductor Solar Cell With High Open-Circuit Voltage Using a Stacking Structure
(2010-12-01)
Chang, Tzu-Yueh
;
Chang, Chun-Lung
;
Lee, Hsin-Yu
;
Lee, Po-Tsung
;
光電工程學系
A stacking metal-insulator-semiconductor (MIS) solar cell structure, which integrates an n-type MIS solar cell with a p-type MIS solar cell, is proposed to effectively enlarge the open-circuit voltage (V(oc)). The measured V(oc) is up to 0.71 V under simulated air mass 1.5 illumination (100 mW/cm(2)). This V(oc) is larger than those of the n-type or p-type MIS solar cells with or without surface passivation. In this letter, we successfully demonstrate the feasibility of the V(oc) enhancement of MIS solar cells by using a stacking structure.
A Novel Hybrid Plasmonic Rod-dimer/Ring Nanostructure for Sensing and Trapping
(2014)
Lin, Jia-Yu
;
Tsai, Chia-Yang
;
Lin, Pin-Tso
;
Hsu, Tse-En
;
Lee, Po-Tsung
We propose and investigate a novel hybrid plasmonic rod-dimer/ring (RDR) nanostructure with significantly enhanced near-field at the gap region for its potential on sensing and trapping applications.
A Novel Liquid Packaging Structure of Deep-Ultraviolet Light-Emitting Diodes to Enhance the Light-Extraction Efficiency
(2019-04-01)
Kang, Chieh-Yu
;
Lin, Chih-Hao
;
Wu, Tingzhu
;
Lee, Po-Tsung
;
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.
Advantages of Blue LEDs With Graded-Composition AlGaN/GaN Superlattice EBL
(2013-11-01)
Lin, Bing-Cheng
;
Chen, Kuo-Ju
;
Han, Hau-Vei
;
Lan, Yu-Pin
;
Chiu, Ching-Hsueh
InGaN/GaN light-emitting diodes (LEDs) with graded-composition AlGaN/GaN superlattice (SL) electron blocking layer (EBL) were designed and grown by metal-organic chemical vapor deposition. The simulation results demonstrated that the LED with a graded-composition AlGaN/GaN SL EBL have superior hole injection efficiency and lower electron leakage over the LED with a conventional AlGaN EBL or normal AlGaN/GaN SL EBL. Therefore, the efficiency droop can be alleviated to be similar to 20% from maximum at an injection current of 15-120 mA, which is smaller than that for conventional AlGaN EBL (30%). The corresponding experimental results also confirm that the use of a graded-composition AlGaN/GaN SL EBL can markedly enhance the light output power by 60%.
All-optical controllable trapping and transport of subwavelength particles on a tapered photonic crystal waveguide
(2011-02-01)
Lin, Pin-Tso
;
Lee, Po-Tsung
;
光電工程學系
;
Department of Photonics
We propose that a tapered photonic crystal waveguide design can unify optical trapping and transport functionalities to advance the controllability of optical manipulation. Subwavelength particles can be trapped by a resonance-enhanced field and transported to a specified position along the waveguide on demand by varying the input wavelength. A simulated transport ability as high as 148 (transport distance/wavelength variation) is obtained by the waveguide with 0.1 degrees tilted angle. Stable trapping of a 50 nm polystyrene particle can be achieved with input power of 7 mW. We anticipate that this design would be beneficial for future life science research and optomechanical applications. (C) 2011 Optical Society of America
Bioceramic Resonance Effect on Meridian Channels: A Pilot Study
(2015-01-01)
Leung, Ting-Kai
;
Chan, Wing P.
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Tai, Chen-Jei
;
Cho, Ting-Pin
;
Yang, Jen-Chang
Bioceramic is a kind of material which emits nonionizing radiation and luminescence, induced by visible light. Bioceramic also facilitates the breakup of large clusters of watermolecules by weakening hydrogen bonds. Hydrogen bond weakening, which allows watermolecules to act in diverse ways under different conditions, is one of the key mechanisms underlying the effects of Bioceramic on biophysical and physical-chemical processes. Herein, we used sound to amplify the effect of Bioceramic and further developed an experimental device for use in humans. Thirteen patients who suffered from various chronic and acute illnesses that severely affected their sleep patterns and life quality were enrolled in a trial of Bioceramic resonance (i.e., rhythmic 100-dB sound waves with frequency set at 10 Hz) applied to the skin surface of the anterior chest. According to preliminary data, a "Propagated Sensation along Meridians" (PSM) was experienced in all Bioceramic resonance-treated patients but not in any of the nine control patients. The device was believed to enhance microcirculation through a series of biomolecular and physiological processes and to subject the specific meridian channels of Traditional Chinese Medicine (TCM) to coherent vibration. This noninvasive technique may offer an alternative to needle acupuncture and other traditional medical practices with clinical benefits.
Boosting and Localizing Near-Field in Plasmonic Mirror-Image Nanoepsilon
(2018-02-01)
Lin, Jia-Yu
;
Lee, Po-Tsung
;
光電工程學系
;
Department of Photonics
A novel plasmonic mirror-image nanoepsilon (MINE) structure is studied to achieve significantly enhanced and localized near-field. It is well-known that the nanorod dimer is able to gain a high local field at the center of the structure by adjusting its rod width, rod length, and gap distance. When adopting an auxiliary nanoring structure electron reservoirs surrounding the nanorod-dimer to form the MINE structure, the local field can be further enhanced owing to a large amount of charges into sharp dimer structure which can confine the accumulation of charges to apexes. Thus, better synergistic interaction of gap effect and lightning-rod effect can be achieved for high field enhancement around nanoscale gap. The symmetric mode in the MINE structure enables strong near-field with a concentrated distribution around the gap. The influences of rod-tip angle and gap distance on the optical properties of plasmonic MINE structures are numerically investigated. With reducing the rod-tip angle and gap distance, considerable enhancements on the field intensities at the rod tips and the gap center can be attributed to the improved lightning-rod and gap effects. The near-field intensities at the rod tip and gap center are dramatically enlarged similar to 1.94 x 10(4) and similar to 1.41 x 10(4) times with the rod-tip angle of 41 degrees and gap distance of 10 nm, and the near-field is localized within an extremely small range. These features are very beneficial for various plasmonic applications.
Boron-doping effect on the super-high density Si quantum dot thin films utilizing a gradient Si-rich oxide multilayer structure
(2019-05-01)
Huang, Pin-Ruei
;
Chen, You-Cheng
;
Kuo, Kuang-Yang
;
Lee, Po-Tsung
;
光電工程學系
Boron (B)-doped gradient Si-rich oxide multilayer (GSRO-ML) structure is utilized to realize super-high density Si quantum dots (QDs) thin films with large carrier tunneling probability by co-sputtering. The B-doping effect on crystalline, optical, electrical and photovoltaic (PV) properties of Si QD thin films is investigated in this study. With increased B-doping concentration, the preserved high crystallinity of Si QDs and the reduced optical bandgap are observed. An optimized doping condition is found for the electrical and PV properties. Further increasing the doping concentration leads to increased inactive B atoms and interfacial over-diffusion. The issue of interfacial over-diffusion can be efficiently improved by inserting lowly B-doped GSRO-ML thin films. Our results show the feasibility and great potential for high efficiency Si-based solar cells integrating Si QDs by properly doped B atoms in GSRO-ML thin film structure.
Carbon attachment on the aluminum nitride gate dielectric in the pentacene-based organic thin-film transistors
(2009-03-15)
Zan, Hsiao-Wen
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Chou, Cheng-Wei
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Wang, Chung-Hwa
;
Song, Ho-Tsung
;
Hwang, Jenn-Chang
This study presents carbon attachment on an aluminum nitride (AlN) gate dielectric to improve the device performance of pentacene-based organic thin-film transistors (OTFTs). This approach produces high OTFT performance on an aged AlN surface. A high mobility of 0.67 cm(2)/V s was achieved on an AlN surface aged for 14 days, compared to a mobility of 0.05 cm(2)/V s on an as-deposited AlN surface. This improvement in device performance is correlated with carbon attachment on the AlN surface, which lowers surface energy. The lowered surface energy made the surface less polar, as measured by a contact angle instrument. The chemical composition of the aged AlN surface was analyzed using x-ray photoelectron spectroscopy before pentacene deposition. Enhanced C=C bonding at 284.5 eV was observed on the aged AlN surface. These enhanced C=C bonds favored the growth of large pentacene islands in the initial growth stage, which may improve OTFT device performance.
Characteristics of MIS Solar Cells Using Sputtering SiO(2) Insulating Layers
(2010-01-01)
Chang, Tzu-Yueh
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Chang, Chun-Lung
;
Lee, Hsin-Yu
;
Lee, Po-Tsung
;
光電工程學系
In this study, the characteristics of both p-type and n-ype Metal-Insulator-Semiconductor (MIS) solar cells with sputtering SiO(2) insulating layers fabricated by radio-frequency (RF) magnetron sputtering are investigated. The characteristics of MIS solar cells are considerably affected by the thickness of the SiO(2) insulating layer and a hydrogen (H(2)) annealing process. Moreover, the performance of MIS solar cells with sputtering SiO(2) insulating layer can be greatly enhanced by depositing a SiN(x) passivation layer on top. It suggests that a sputtering SiO(2) insulating layer is a good alternative insulating layer for MIS solar cells.
Characteristics of MIS Solar Cells Using Sputtering SiO2 Insulating Layers
(2010-01-01)
Chang, Tzu-Yueh
;
Chang, Chun-Lung
;
Lee, Hsin-Yu
;
Lee, Po-Tsung
;
光電工程學系
In this study, the characteristics of both p-type and n-ype Metal-Insulator-Semiconductor (MIS) solar cells with sputtering SiO2 insulating layers fabricated by radio-frequency (RF) magnetron sputtering are investigated. The characteristics of MIS solar cells are considerably affected by the thickness of the SiO2 insulating layer and a hydrogen (H-2) annealing process. Moreover, the performance of MIS solar cells with sputtering SiO2 insulating layer can be greatly enhanced by depositing a SiNx passivation layer on top. It suggests that a sputtering SiO2 insulating layer is a good alternative insulating layer for MIS solar cells.
Compact Tunable Laser With InGaAsP Photonic Crystal Nanorods for C-Band Communication
(2015-11-01)
Shih, Min-Hsiung
;
Hsu, Kung-Shu
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Lee, Kevin
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Lai, Kun-Ting
;
Lin, Chun-Ting
In this study, an ultracompact tunable laser with InGaAsP photonic crystal nanorods for optical communication was demonstrated within 10-mu m footprint. The square photonic crystal nanorods with the InGaAsP quantum wells were fabricated and embedded in a flexible polydimethylsiloxane substrate. The high-quality single mode lasing with low threshold around the symmetry point Gamma was achieved in experiments. The lasing wavelength can be linearly fine-tuned by varying the extension percentage of photonic crystals and the wavelength tunable range covers the whole conventional band communication ambit. The lasing wavelength shift is attributed to the PhC lattice distortion, and its tuning behavior agrees with the 3-D simulation results. This ultrasmall, wide-range wavelength tunable laser can function as a novel light source for the chip-scale photonic integrated circuits and optics communication system.
Compressible 1D photonic crystal nanolasers with wide wavelength tuning
(2017-06-15)
Lu, Tsan-Wen
;
Wu, Chia-Cheng
;
Wang, Chun
;
Lee, Po-Tsung
;
資訊工程學系
We propose and demonstrate a tunable photonic crystal nanolaser consisting of 1D periodic nanorods wrapped in deformable polydimethylsiloxane. In addition to low-threshold and long-term lasing stability, the nanolaser also displays reproducible and reliable wavelength tuning with a large tunability of 7.7 nm under 1% compression. By further associating with stretching, a very wide wavelength-tunable range of 155 nm that almost spans the entire S + C + L telecommunication bands is successfully demonstrated with a single nanolaser device. (C) 2017 Optical Society of America
Design and Fabrication of the Reliable GaN Based Vertical-Cavity Surface-Emitting Laser via Tunnel Junction
(2019-04-01)
Shen, Chih-Chiang
;
Lu, Yun-Ting
;
Yeh, Yen-Wei
;
Chen, Cheng-Yuan
;
Chen, Yu-Tzu
In this study, we theoretically designed and experimentally fabricated an InGaN vertical-cavity surface-emitting laser (VCSEL) with a tunnel junction (TJ) structure. From numerical simulation results, the optical loss of the device can be reduced by a TJ structure. Additionally, the leakage current of the VCSEL with TJ structure was much smaller than that of the VCSEL with an Indium-Tin-Oxide (ITO) layer. We have been demonstrated that laser output performance is improved by using the TJ structure when compared to the typical VCSEL structure of the ITO layer. The output power obtained at 2.1 mW was enhanced by a factor of 3.5 by the successful reduction of threshold current density (J(th)) from 12 to 8.5 kA/cm(2), and the enlarged slope efficiency was due to less absorption in VCSEL with a TJ structure. Finally, the samples passed the high temperature (70 degrees C) and high operation current (1.5 x J(th)) test for over 500 h.
Design, Modeling, and Fabrication of High-Speed VCSEL with Data Rate up to 50 Gb/s
(2019-08-14)
Shen, Chih-Chiang
;
Hsu, Tsung-Chi
;
Yeh, Yen-Wei
;
Kang, Chieh-Yu
;
Lu, Yun-Ting
We have studied the characteristics of frequency response at 850-nm GaAs high-speed vertical-cavity surface-emitting lasers (VCSELs) with different kinds of oxide aperture sizes and cavity length using the PICS3D simulation program. Using 5-mu m oxide aperture sizes, the frequency response behavior can be improved from 18.4 GHz and 15.5 GHz to 21.2 GHz and 19 GHz in a maximum of 3 dB at 25 degrees C and 85 degrees C, respectively. Numerical simulation results also suggest that the frequency response performances improved from 21.2 GHz and 19 GHz to 30.5 GHz and 24.5 GHz in a maximum of 3 dB at 25 degrees C and 85 degrees C due to the reduction of cavity length from 3 lambda/2 to lambda/2. Consequently, the high-speed VCSEL devices were fabricated on a modified structure and exhibited 50-Gb/s data rate at 85 degrees C.
Dielectric-Band Photonic Crystal Nanobeam Lasers
(2013-01-01)
Lee, Po-Tsung
;
Lu, Tsan-Wen
;
Chiu, Li-Hsun
;
交大名義發表
;
光電工程學系
We investigate a mode gap confined dielectric band laser via a 1-D photonic crystal (PhC) nanobeam (NB) nanocavity with lattice gradually shifted PhC mirror. Owing to different modal symmetries, different zeroth-order dielectric mode properties, including quality (Q) factors, mode volumes, lasing thresholds, and slope efficiencies, in nanocavities with two different cavity sizes are investigated. In experiments, single-mode lasing from dielectric bands with low effective lasing thresholds is obtained. Rising of the high-order modes is also observed when we increase the PhC mirror periods for high Q factor of the zeroth-order dielectric mode. In addition, we observe the bonding and antibonding modes in beamwidth mismatched coupled NB nanocavities and switch the dominant lasing mode via spatially nonuniform carrier injection.