Browsing by Author "Huang, Kai-Feng"

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Compact High-Peak-Power End-Pumped AlGaInAs Eye-Safe Laser With a Heat-Spreader Diamond Coated as a Cavity Mirror
(2015-01-01)
Wen, Chi-Ping
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Tuan, Pi-Hui
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Liang, Hsin-Chih
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Huang, Kai-Feng
;
Chen, Yung-Fu
We report on a high-peak-power end-pumped AlGaInAs laser at 1.52 mu m with a linear plane-parallel cavity. A high-reflective coated diamond is utilized not only as the heat spreader but also as the front mirror simultaneously to make the laser cavity to be extremely compact. The average output power and the corresponding peak power under this cavity configuration is found to be up to 2.58 and 516 W separately at a repetition rate of 100 kHz and a pump power of 12 W corresponding to a peak power of 2.4 kW. The experimental results assure the promising application of dielectric coated diamond as a multifunctional optics to fulfill a high performance and compact cavity design.
Conductivity study of nitrogen-doped calcium zinc oxide prepared by spray pyrolysis
(2016-01-15)
Hsu, Yu-Ting
;
Lan, Wen-How
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Huang, Kai-Feng
;
Lin, Jia-Ching
;
Chang, Kuo-Jen
In this study, the spray pyrolysis method was used to prepare unintentionally doped and nitrogen-doped calcium zinc oxide films by using zinc acetate, calcium nitrate precursor, and ammonium acetate precursor. Morphological and structural analyses were conducted using scanning electron microscopy and X-ray diffraction. The results indicated that film grain size decreased as the nitrogen doping was increased. Both calcium oxide and zinc oxide structures were identified in the unintentionally doped calcium zinc oxide. When nitrogen doping was introduced, the film mainly exhibited a zinc oxide structure with preferred (002) and (101) orientations. The concentration and mobility were investigated using a Hall measurement system. P-type films with a mobility and concentration of 10.6 cm(2) V-1 s(-1) and 2.8 x 10(17) cm(-3), respectively, were obtained. Moreover, according to a temperature-dependent conductivity analysis, an acceptor state with activation energy 0.266 eV dominated the p-type conduction for the unintentionally doped calcium zinc oxide. By contrast, a grain boundary with a barrier height of 0.274-0.292 eV dominated the hole conduction for the nitrogen-doped calcium zinc oxide films. (C) 2015 Elsevier B.V. All rights reserved.
Effects of Doping Ratio and Thermal Annealing on Structural and Electrical Properties of Boron-Doped ZnO Thin Films by Spray Pyrolysis
(2013-06-01)
Yu, Cheng-Chang
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Hsu, Yu-Ting
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Lee, Shao-Yi
;
Lan, Wen-How
;
Kuo, Hsin-Hui
Boron-doped zinc oxide (BZO) thin films have been fabricated by spray pyrolysis on a glass substrate. The morphology and electrical properties of the thin films were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were performed. It was found that [B]/[Zn] ratio altered both the microstructure and concentration of the BZO thin films. The film grain size was reduced by increasing the [B]/[Zn] ratio. The highest Hall mobility was 3.65 cm(2)V(-1)s(-1) for the undoped ZnO thin film, and the highest carrier concentration of 1.0 x 10(19) cm(-3) was achieved for the as-deposited BZO thin film with [B]/[Zn] = 1.5 at. %. Conductivity was determined at different measurement temperatures and shallow donors provided the dominate conduction mechanism for the as-deposited BZO thin films. After 600 degrees C annealing, shallow level reduction and donors with a high activation energy of 129 +/- 6 meV in the BZO thin films were characterized, and the shallow donors that dominate the carrier concentration for the as-deposited spray-pyrolized BZO thin film were eliminated. (C) 2013 The Japan Society of Applied Physics
Effects of UV illumination on oxygen detection for ZnO film prepared by thermally oxidized Zn on sapphire substrate
(2014)
Yu, Cheng-Chang
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Hsu, Yu-Ting
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Lan, Wen-How
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Shih, Ming-Chang
;
Hong, Jin-Hua
The ZnO thin film prepared after the 600 degrees C oxidation of thermally-evaporated Zn thin film on sapphire substrate was studied. A nano structured surface morphology was observed by scanning electron microscope. With following Ti/Au metallization, the metal-semiconductor-metal (MSM) device was formed. With ultra violate (UV) light illumination come from the mercury lamp with a short pass filter, the device resistance variation under oxygen atmosphere was investigated. The reduction of detection response time and recovery time for this device with UV light illumination were observed also. After discussion based on the grain boundary connected model, the observed resistance variation controlled by the nano texture was realized. The UV light illumination technology shows an effective method to enhance the gas detection response time for this ZnO MSM gas sensor. Keywords: ZnO, MSM,
Exploring the power scaling of the cryogenic 946 nm monolithic laser
(2018-08-01)
Cho, Chun-Yu
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Huang, Tzu-Lin
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Cheng, Hao-Ping
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Huang, Kai-Feng
;
Chen, Yung-Fu
The criterion for achieving power scaling of the cryogenically cooled monolithic 946 nm laser is investigated by varying crystal length. Theoretical analysis of the mode-to-pump size matching indicates that the optimal power can be obtained with a crystal length of 8 mm. Furthermore, the pump-wavelength dependence of the output power can be less sensitive when a longer crystal was employed. We demonstrate 946 nm monolithic lasers with various crystal lengths to verify the theoretical analysis. The highest output power (30.2 W) is obtained by using an 8 mm Nd:YAG crystal at 130 K. Moreover, the output power reduction ratio is found to be smaller than 15% with the pump wavelength fluctuating between +/- 1 nm.
Exploring the spatio-temporal dynamics of an optically pumped semiconductor laser with intracavity second harmonic generation
(2012-11-15)
Liang, Hsing-Chih
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Lee, Yi-Chun
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Tung, Jung-Chen
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Su, Kuan-Wei
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Huang, Kai-Feng
We experimentally observe an intriguing phenomenon of complex spatio-temporal dynamics in a commercial optically pumped semiconductor laser with intracavity second harmonic generation. We numerically verify that the experimental results come from the total mode locking of transverse electromagnetic modes (TEM00) and higher-order modes with significant astigmatism. The scenarios of the spatio-temporal dynamics are quite similar to the phenomena in soft-aperture Kerr-lens mode locked Ti:sapphire lasers. (C) 2012 Optical Society of America
Extracting photon periodic orbits from spontaneous emission spectra in laterally confined vertically emitted cavities
(2010-08-15)
Chen, Yung-Fu
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Yu, Yan-Ting
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Huang, Yu-Jen
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Chiang, Po-Yi
;
Su, Kuan-Wei
We report our observation of the signature of photon periodic orbits in the spontaneous emission spectra of large-aperture vertical-cavity surface-emitting lasers (VCSELs). The high-resolution measurement clearly demonstrates that over a thousand cavity modes with a narrow linewidth can be perfectly exhibited in the spontaneous emission spectrum just below the lasing threshold. The Fourier-transformed spectrum is analyzed to confirm that the spontaneous emission spectra of large-aperture VCSELs can be exploited to analogously investigate the energy spectra of the 2D quantum billiards. (C) 2010 Optical Society of America
Generating High-Order Transverse Patterns in Optically Pumped Semiconductor Lasers
(2019-11-01)
Tuan, Pi-Hui
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Hsieh, Yen-Hui
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Tu, Chin-Wei
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Lee, Chi-Chun
;
Tsou, Chia-Han
High-order pattern formation in an optically pumped semiconductor laser (OPSL) under a selective pumping with varying spatial overlap between the pump beam and transverse modes is explored. In contrast to transverse pattern generation by off-axis pumped solid-state lasers where the mode order can be flexibly increased, experimental results reveal that the selective pumping fails to realize high-order mode operation in OPSLs when the pump-to-mode size ratio and pump power are insufficiently large. On the other hand, several high-order patterns belonging to the Hermite-Laguerre-Gaussian (HLG) modes are observed when scanning a large-ratio pump beam to specific positions on the gain chip. These HLG modes are experimentally confirmed to mainly originate from the transverse non-uniformity of present OPSL chip, while their structural features cannot be simply correlated with the pump scanning positions. Nevertheless, it is believed that the first-time observation of pure HLG modes under the large-ratio pumping can offer useful insights into the high-order pattern manipulation in OPSLs.
Improved Output Power of Nitride-Based Light-Emitting Diodes With Convex-Patterned Sapphire Substrates
(2012-10-01)
Hsu, Yu-Ting
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Yu, Cheng-Chang
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Huang, Kai-Feng
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Lan, Wen-How
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Huang, Jing-En
Nitride-based light-emitting diodes (LEDs) grown on different convex-patterned sapphire substrates are proposed and fabricated. The electrical and optical properties of these LEDs are discussed in detail. It is found that the LED with a ball-shape patterned sapphire substrate has the best crystalline quality and I-V characteristic. On the other hand, on reducing total internal reflection, the LED with hexagonal-shape patterned sapphire substrate (HPSS) has the best performance on output power and external quantum efficiency. In comparison to the LED without patterned substrate, the LED with HPSS has 175% and 165% enhancement on output power and external quantum efficiency, respectively.
Improved Performance of InGaN/GaN Light-Emitting Diodes With Thin Intermediate Barriers
(2011-11-15)
Chen, Bo-Chun
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Chang, Chun-Yen
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Fu, Yi-Keng
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Huang, Kai-Feng
;
Lu, Yu-Hsuan
In this work, the performance of blue InGaN/GaN light-emitting diodes (LEDs) with thin intermediate barriers at high injection current is investigated. From the experimental results, it is found that the performance of LEDs with intermediate 5-nm-thick barriers is improved about 15% at 200 mA, compared with the sample with unique 9-nm-thick barriers. A numerical study is executed to analyze the hole distributions in the quantum wells. From the simulated results, it is found that the hole injection efficiency can be improved at high injection current. Hence, the effective recombination of electron and hole is also enhanced at high injection current.
Indium-Nitrogen Codoped Zinc Oxide Thin Film Deposited by Ultrasonic Spray Pyrolysis on n-(111) Si Substrate: The Effect of Film Thickness
(2014)
Yu, Cheng-Chang
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Lan, Wen-How
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Huang, Kai-Feng
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電子物理學系
;
Department of Electrophysics
Indium-nitrogen codoped zinc oxide (INZO) thin films were fabricated by spray pyrolysis deposition technique on n-(111) Si substrate with different film thicknesses at 450 degrees C using a precursor containing zinc acetate, ammonium acetate, and indium nitrate with 1 : 3 : 0.05 at.% concentration. The morphology and structure studies were carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The grain size of the films increased when increasing the film thickness. From XRD spectra, polycrystalline ZnO structure can be observed and the preferred orientation behavior varied from(002) to (101) as the film thickness increased. The concentration and mobility were investigated by Hall effect measurement. the p-type films with a hole mobility around 3 cm(2)V(-1)s(-1) and hole concentration around 3 x 10(19) cm(-3) can be achieved with film thickness less than 385 nm. The n-type conduction with concentration 1 x 10(20) cm(-3) is observed for film with thickness 1089 nm. The defect states were characterized by photoluminescence. With temperature-dependent conductivity analysis, acceptor state with activation energy 0.139 eV dominate the p type conduction for thin INZO film. And the Zn-related shallow donors with activation energy 0.029 eV dominate the n-type conduction for the thick INZO film.
Influence of High-Order Modes in Starting Self-Mode-Locked Optically Pumped Semiconductor Laser
(2013)
Liang, Hsing-Chih
;
Lee, Yi-Chun
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Tung, Jung-Chen
;
Su, Kuan-Wei
;
Chen, Yung-Fu
We explored the influence of pump-to-mode size ratios on optically pumped semiconductor laser. With a large pump-to-mode size ratio, the output beam was self-modelocked with 1.17 ps pulse duration at a repetition rate of 1.8GHz.
Investigation of the (Cu, Ga) InSe2 thin film with different pairs of CuGa/In sputtered layers
(2012)
Hsu, Yu-Ting
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Huang, Kai-Feng
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Tsai, Shang-I
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Lan, Wen-How
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Yueh, Ming
Thin film samples of (Cu,Ga) InSe2 (CIGS) were prepared by DC magnetron sputtering and the selenisation process onto soda lime glass substrates. All samples had the same deposition conditions, and the optimal sputtering thickness of samples with one CuGa/In pair and two CuGa/In pairs are also the same. After sample deposition, X-ray diffraction (XRD), scanning electron microscope (SEM) and Hall effect measurements were used to characterize the properties of these samples. From XRD measurement results, excepting an extra small CuSe peak existing in the samples with two CuGa/In pairs, the XRD peaks of all samples are perfectly matched with the phase diagram of CuGa0.3In0.7Se2 material. It was also found that the grain sizes of the samples with one CuGa/In pair are larger than those with two CuGa/In pairs from SEM images. All these observations on samples with two CuGa/In pairs can be attributed to the fact that the less In incorporation in CIGS films, which it has been proven that the sample with low In-to-CuGa ratio has stronger CuSe peak from XRD result. Furthermore, the p-type carrier characteristics can be observed for all samples from Hall measurement results. The carrier mobility and concentration of the samples with one CuGa/In pair can be achieved as high as 15.28 cm(2)/Vs and as low as 1.50x10(16) cm(-3), respectively, while the carrier mobility and concentration of the ones with two CuGa/In pairs can be achieved as 6.4 cm(2)/Vs and 6.27x10(17) cm(-3), respectively. The results of superior electrical properties of samples with one CuGa/In pair agree well with the observations form XRD and SEM results. In the final, the optimal value of In-to-CuGa ratio during CuGa/In layers deposition in this study is 0.625.
On the Nitrogen Doping in Erbium and Nitrogen Codoped Magnesium Zinc Oxide Diode by Spray Pyrolysis
(2020-01-01)
Chen, Chun-An
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Hsu, Yu-Ting
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Lan, Wen-How
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Huang, Kai-Feng
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Chang, Kuo-Jen
Diodes with an erbium and nitrogen codoped magnesium zinc oxide (MgZnO:Er,N) active layer were fabricated by spray pyrolysis on Si substrate with aqueous solutions including magnesium nitrate, zinc acetate, erbium acetate, ammonium acetate, and indium nitrate precursors. Diodes with different nitrogen content in their precursor were prepared and their properties were investigated. With scanning electron microscopy, film surface with mixed hexagonal flakes and tiny blocks was characterized for all samples. Certain morphologies varied for samples with different N contents. In the photoluminescence analyses, the intensity of the oxygen-related defects peak increased with the increasing of nitrogen content. The diodes were fabricated with an Au and In deposition on the top and backside. The diode current-voltage as well as capacitance-voltage characteristics were examined. An ununiformed n-type concentration distribution with high concentration near the interface in the MgZnO:Er,N layer was characterized for all samples. Diodes with high nitrogen content exhibit reduced breakdown voltage and higher interface concentration characteristics. Under reversed bias conditions with an injection current of 50 mA, a light spectrum with two distinct green emissions around wavelengths 532 and 553 nm was observed. A small spectrum variation was characterized for diodes prepared from different nitrogen content. The diode luminescence characteristics were examined and the diode prepared from N/Zn=1 in the precursor showed an optimal injection current-to-luminescence property. The current and luminescence properties of the diode were characterized and discussed.
Orthogonally Polarized Self-Mode-Locked Lasers With Repetition Rate Multiplication up to Hundreds of Gigahertz: Observation of Temporal Carpets
(2018-09-01)
Chen, Yung-Fu
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Chang, Ming-Ting
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Huang, Tzu-Lin
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Tung, Jung-Chen
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Huang, Kai-Feng
Mode-locked laser sources with high repetition rates in the range of 10-1000 GHz are of considerable interest in modern communications, optical metrology, and photonic applications. Currently, developed laser systems generally suffer from the hardware complexity and energy loss. Here, we demonstrate a compact robust scheme based on a self-mode-locked monolithic Yb:KGW laser with external feedback coupling to achieve numerous repetition rate multiplications in the range of 25-330 GHz. The output pulse train consists of two orthogonally polarized components to form a vector state that is beneficial to practical applications. More intriguing, the pulse train measured as a function of the distance of the coupling feedback reveals a feature of the fractional recurrence that is like the Talbot carpet. An analytic formula is derived to manifest the formation of the temporal carpets. The developed experiment and formula not only pave a useful way for generating ultrahigh-repetition-rate femtosecond lasers but also provide new perspectives in the fractional recurrences of coherent waves.
Photocatalytic study of Zinc Oxide with bismuth doping prepared by spray pyrolysis
(2015-09-01)
Lin, Tzu-Yang
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Hsu, Yu -Ting
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Lan, Wen-How
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Huang, Chien-Jung
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Chen, Lung-Chien
The unintentionally doped and bismuth (Bi) doped zinc oxide (ZnO) films were prepared by spray pyrolysis at 450 degrees C with zinc acetate and bismuth nitrate precursor. The n-type conduction with concentration 6.13 x10(16)cm(-3) can be observed for the unintentionally doped ZnO. With the increasing of bismuth nitrate concentration in precursor, the p-type conduction can be observed. The p-type concentration 4.44x10(17)cm(-3) can be achieved for the film with the Bi/Zn atomic ratio 5% in the precursor. The photoluminescence spectroscopy with HeCd laser light source was studied for films with different Bi doping. The photocatalytic activity for the unintentionally doped and Bi-doped ZnO films was studied through the photodegradation of Congo red under UV light illumination. The effects of different Bi contents on photocatalytic activity are studied and discussed. Results show that appropriate Bi doping in ZnO can increase photocatalytic activity.
Realizing High-Pulse-Energy Large-Angular-Momentum Beams by Astigmatic Transformation of Geometric Modes in an Nd:YAG/Cr4+:YAG Laser
(2018-09-01)
Tuan, Pi-Hui
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Liang, Hsin-Chih
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Huang, Kai-Feng
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Chen, Yung-Fu
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電子物理學系
An off-axis pumped Nd:YAG/Cr4+:YAG laser under different degenerate cavity conditions has been thoroughly studied to generate high-pulse-energy geometric modes for further beam transformation. Because of the employment of Nd:YAG gain crystal provides a flexible choice of cavity length to achieve efficient passively Q-switched (PQS) operation, various PQS geometric modes with stable spatial structures are generated. Moreover, it is experimentally confirmed that the output energy and peak power of the PQS geometric modes can easily reach up to over 100 mu J and 10 kW with fairly stable pulse trains in pure linear polarization. By using an astigmatic mode converter (AMC) to transform the planar geometric modes into the circular geometric modes, various high-energy vortex beams with large angular momentum and diverse phase structures are successfully realized to offer a promising light source for further application. The propagation evolution of the transformed geometric modes through the AMC was also analyzed theoretically to offer useful insights for the formation of the geometric vortex beams.
Study of InGaN-Based Light-Emitting Diodes on a Roughened Backside GaN Substrate by a Chemical Wet-Etching Process
(2011-10-01)
Fu, Yi-Keng
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Chen, Bo-Chun
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Fang, Yen-Hsiang
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Jiang, Ren-Hao
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Lu, Yu-Hsuan
The InGaN-based light-emitting diodes (LEDs) with a roughened backside on the N-face surface of GaN substrate were fabricated through a chemical wet-etching process to increase light-extraction efficiency. The stable crystallographic etching planes were formed as the GaN {10 (11) over bar} planes. When the near-ultraviolet and blue LED were operated as a forward current of 20 mA, the output power of LEDs was improved from 13.2 and 19.9 mW to 25.6 and 24.0 mW, respectively. The different enhanced ratio is attributed to the different transmittance as a function of wavelength is caused from hexagonal pyramid on N-face GaN substrate after wet-etching process.
The Influences of Boundary Shapes on Polarization Characteristics and Lasing Modes in Broad-Area Vertical-Cavity Surface-Emitting Lasers With Cryogenic Detuning: Regular Versus Chaotic Cavities
(2015-11-01)
Yu, Yan-Ting
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Tuan, Pi-Hui
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Chiang, Po-Yi
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Su, Kuan-Wei
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Huang, Kai-Feng
The broad-area rectangular-shaped and stadiumshaped VCSELs with nearly the same aspect ratio are designed to explore the influence of lateral boundary shapes on polarization states and lasing spectra with large detuning by cryogenic cooling. For the rectangular-shaped VCSEL, the lasing modes usually exhibit linearly polarized state and their far-field emissions mainly concentrate on four diagonal directions. On the other hand, the lasing modes of the stadium-shaped VCSEL generally display two orthogonally polarized states and their far-field emissions extensively spread on azimuthal directions. More intriguingly, the lasing spectra of the two devices clearly manifest the features of the energy-level distribution in regular and chaotic quantum billiards, respectively.
Thickness Study of Er-Doped Magnesium Zinc Oxide Diode by Spray Pyrolysis
(2018-12-01)
Hsu, Yu-Ting
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Lee, Che-Chi
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Lan, Wen-How
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Huang, Kai-Feng
;
Chang, Kuo-Jen
Erbium-doped magnesium zinc oxides were prepared through spray pyrolysis deposition at 450 degrees C with an aqueous solution containing magnesium nitrate, zinc acetate, erbium acetate, and indium nitrate precursors. Diodes with different erbium-doped magnesium zinc oxide thicknesses were fabricated. The effect of erbium-doped magnesium zinc oxide was investigated. The crystalline structure and surface morphology were analyzed using X-ray diffraction and scanning electron microscopy. The films exhibited a zinc oxide structure, with (002), (101), and (102) planes and tiny rods in a mixed hexagonal flakes surface morphology. With the photoluminescence analyses, defect states were identified. The diodes were fabricated via a metallization process in which the top contact was Au and the bottom contact was In. The current-voltage characteristics of these diodes were characterized. The structure resistance increased with the increase in erbium-doped magnesium zinc oxide thickness. With a reverse bias in excess of 8 V, the light spectrum, with two distinct green light emissions at wavelengths of 532 nm and 553 nm, was observed. The light intensity that resulted when using a different operation current of the diodes was investigated. The diode with an erbium-doped magnesium zinc oxide thickness of 230 nm shows high light intensity with an operational current of 80 mA. The emission spectrum with different injection currents for the diodes was characterized and the mechanism is discussed.