Browsing by Author "Lee, Chao-Kuei"

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Blue-light generating femtosecond wavelength-tunable non-collinear optical parametric amplifier
(2006-03-02)
Pan, Ci-Ling
;
Huang, J. Y.
;
Zhang, Jing-Yuan
;
Lee, Chao-Kuei
The present invention discloses a means of the generation of tunable femtosecond pulses from 380 nm to 465 nm near the degenerate point of a 405-nm pumped type-I BBO non-collinearly phase-matched optical parametric amplifier (NOPA). The tunable UV/blue radiation is obtained from sum frequency generation (SFG) between the OPA output and the residual fundamental beam at 810-nm and cascaded second harmonic generation (SHG) of OPA. With a pumping energy of 75 mJ at 405 nm, the optical conversion efficiency from the pump to the tunable SFG is more than 5% and the efficiency of SHG of the OPA is about 2%.
Carrier-Envelope-Phase Control of Ultrashort Periodic Pulses Synthesized from Raman Generated Combs
(2009-01-01)
Hsieh, Zhi-Ming
;
Lai, Chien-Jen
;
Chan, Han-Sung
;
Wu, Sih-Ying
;
Lee, Chao-Kuei
The carrier-envelope phase of Raman generated ultrashort pulses is controlled by driving the Raman coherence with a beam at near the raman resonance frequency and its second harmonic.
Catalytically solid-phase self-organization of nanoporous SnS with optical depolarizability
(2016)
Cheng, Chih-Hsien
;
Chi, Yu-Chieh
;
Wu, Chung-Lun
;
Lin, Chun-Jung
;
Tsai, Ling-Hsuan
The catalytic solid-phase synthesis of self-organized nanoporous tin sulfide (SnS) with enhanced absorption, manipulative transmittance and depolarization features is demonstrated. Using an ultralow radio-frequency (RF) sputtering power, the variation of the orientation angle between the anodized aluminum oxide (AAO) membrane and the axis of the sputtered ion beam detunes the catalytically synthesized SnS from nanorod to nanoporous morphology, along the sidewall of the AAO membrane. The ultraslow catalytic sputtering synthesis on the AAO at the RF plasma power of 20 W and the orientation angle of 0 degrees regulates the porosity and integrality of nanoporous SnS, with average pore diameter of 80-150 nm. When transferring from planar to nanoporous structure, the phase composition changes from SnS to SnS2-Sn2S3, and the optical bandgap shrinks from 1.43 to 1.16 eV, due to the preferred crystalline orientation, which also contributes to an ultralow reflectance of <1% at 200-500 nm when both the transmittance and the surface scattering remain at their maxima. The absorption coefficient is enhanced by nearly one order of magnitude with its minimum of >5 x 10(4) cm(-1) at the wavelength between 200 and 700 nm, due to the red-shifting of the absorption spectrum to at least 100 nm. The catalytically self-organized nanoporous SnS causes strong haze and beam divergence of 20 degrees-30 degrees by depolarized nonlinear scattering at the surface, which favors the solar energy conversion with reduced surface reflection and enhanced photon scattering under preserved transmittance.
Chirped-pulse control of carrier dynamics in low-temperature grown GaAs
(2011)
Lee, Chao-Kuei
;
Lin, Sung-Hui
;
Yang, C. S.
;
Pan, Ci-Ling
;
物理研究所
In this work, using chirped pulse excitation pump-probe technique, we present the results of a study of carrier dynamics modulation in low-temperature-grown GaAs. Increasing carrier relaxation times as varying the excitation chirped conditions from negative to positive is demonstrated and explained by spectral dependence of carrier dynamics in Shockley-Read Hall model. We also indicate that chirped pulse has the feasibility of controlling carrier dynamics in ultrafast optical devices.
Chirped-pulse manipulated carrier dynamics in low-temperature molecular-beam-epitaxy grown GaAs
(2014-04-28)
Lee, Chao-Kuei
;
Lin, Yuan-Yao
;
Lin, Sung-Hui
;
Lin, Gong-Ru
;
Pan, Ci-Ling
Chirped pulse controlled carrier dynamics in low-temperature molecular-beam-epitaxy grown GaAs are investigated by degenerate pump-probe technique. Varying the chirped condition of excited pulse from negative to positive increases the carrier relaxation time so as to modify the dispersion and reshape current pulse in time domain. The spectral dependence of carrier dynamics is analytically derived and explained by Shockley-Read Hall model. This observation enables the new feasibility of controlling carrier dynamics in ultrafast optical devices via the chirped pulse excitations. (C) 2014 AIP Publishing LLC.
Coherent multiple-stage optical rectification terahertz wave generator
(2010-08-26)
Pan, Ci-Ling
;
Huang, Jung Y.
;
Chang, Chen-Shiung
;
Chen, Ching-Wei
;
Lin, Yu-Shian
The present invention coherent multiple-stage optical rectification terahertz wave generator discloses the generation of single-cycle terahertz radiation with two-stage optical rectification in GaSe crystals. By adjusting the time delay between the pump pulses employed to excite the two stages, the terahertz radiation from the second GaSe crystal can constructively superpose with the seeding terahertz field from the first stage. The high mutual coherence between the two terahertz radiation fields is ensured with the coherent optical rectification process and can be further used to synthesize a desired spectral profile of output coherent THz radiation. The technique is also useful for generating high amplitude single-cycle terahertz pulses, not limited by the pulse walk-off effect from group velocity mismatch in the nonlinear optical crystal used.
Controlling the Carrier-Envelope Phase of Raman-Generated Periodic Waveforms
(2009-05-29)
Hsieh, Zhi-Ming
;
Lai, Chien-Jen
;
Chan, Han-Sung
;
Wu, Sih-Ying
;
Lee, Chao-Kuei
We demonstrate control of the carrier-envelope phase of ultrashort periodic waveforms that are synthesized from a Raman-generated optical frequency comb. We generated the comb by adiabatically driving a molecular vibrational coherence with a beam at a fundamental frequency plus its second harmonic. Heterodyne measurements show that full interpulse phase locking of the comb components is realized. The results set the stage for the synthesis of periodic arbitrary waveforms in the femtosecond and subfemtosecond regimes with full control.
Controlling the Light Waveform of Attosecond Pulse Train by Synthesized Multi-colored Laser Fields
(2012)
Chen, Wei-Jan
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Wang, Hong-Zhe
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Lin, Ruei-Yin
;
Lee, Chao-Kuei
;
Pan, Ci-Ling
We show a process to generate a high peak power and waveform controllable light source. The bandwidth is more than two octaves, so the electric field oscillation in the pulse envelope is close to half cycle. It is promising to apply to high-order harmonic generation by sub-cycle pulse.
Efficient wavelength conversion with low operation power in a Ta2O5-based micro-ring resonator
(2017-12-01)
Wu, Chung-Lun
;
Huang, Jen-Yang
;
Ou, Ding-Hsin
;
Liao, Ting-Wei
;
Chiu, Yi-Jen
The Ta2O5-based micro-ring resonator with an unloaded quality factor of 182,000 has been demonstrated to realize efficient nonlinear wavelength generation. The propagation loss of the resonator is 0.5 cm(-1), and the buildup factor of the ring resonator is estimated to be similar to 50. With a high buildup factor of the ring structure, the four-wave-mixing (FWM) conversion efficiency of -30 dB is achieved in the resonator with a pump power of 6 mW. Based on power-dependent FWM results, the nonlinear refractive index of Ta2O5 is estimated to be 1.4x10-14 cm(2)/W at a wavelength of similar to 1550 nm. The demonstration of an enhanced FWM process in the Ta(2)O(5-)based micro-ring cavity implies the possibility of realizing FWM-based optical parametric oscillation in a Ta2O5-based micro-ring resonator. (C) 2017 Optical Society of America
Enhancement of broadband Terahertz Radiation by carrier dynamics modulation with a single chirped optical pulse
(2008)
Lee, Chao-Kuei
;
Lin, Sung-Hui
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Pan, Ci-Ling
;
光電工程學系
;
Department of Photonics
Over 60% enhancement of broadband THz radiation and two-fold bandwidth broadening are demonstrated by a single positive chirped optical pulse. A model of carrier dynamics modulation is proposed to explain this phenomenon. (C) 2008 Optical Society of America
Full Control of the Carrier-Envelope Phase of Raman-Generated Single-Cycle Waveforms
(2009-01-01)
Hsieh, Zhi-Ming
;
Lai, Chien-Jen
;
Chan, Han-Sung
;
Wu, Sih-Ying
;
Lee, Chao-Kuei
Precise control of the carrier-envelope phase of Raman genearated ultrashort pulses is achieved by generating a Raman frequency comb using an infrared laser pulse and its second harmonic to drive the Raman coherence. (C) 2009 Optical Society of America
Gate Insulator Morphology-Dependent Reliability in Organic Thin-Film Transistors
(2016-02)
Chen, Hua-Mao
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Chang, Ting-Chang
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Tai, Ya-Hsiang
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Chiang, Hsiao-Cheng
;
Liu, Kuan-Hsien
In this letter, we investigated the gate insulator morphology affecting on the electric characteristic variation for organic thin-film transistors (OTFTs). From the transfer characteristics, there is a result with leakage current when the gate voltage is lower than the threshold voltage, which is due to the gate insulator thickness variation. Furthermore, regardless of whether the OTFT is operated under positive or negative bias stress, the more severe degradation happened in the hump region of transfer characteristics. Because a thinner gate insulator causes a high electric field, more charges are trapped in a gate dielectric stack.
Generation and spectral manipulation of coherent terahertz radiation with two-stage optical rectification
(2008-09-01)
Chen, Ching-Wei
;
Lin, Yu-Shian
;
Huang, Jung Y.
;
Chang, Chen-Shiung
;
Pan, Ci-Ling
We propose and experimentally demonstrate the generation of single-cycle terahertz radiation with two-stage optical rectification in GaSe crystals. By adjusting the time delay between the pump pulses employed to excite the two stages, the terahertz radiation from the second GaSe crystal can constructively superpose with the terahertz field injected from the first stage. The high mutual coherence between the two terahertz radiation fields is ensured with the coherent optical rectification process and can be further used to synthesize a desired spectral profile of coherent THz radiation. The technique is also potentially useful for generating high-power single-cycle terahertz pulses, usually limited by the pulse walk-off effect of the nonlinear optical crystal used. (c) 2008 Optical Society of America.
Growing GaN LEDs on amorphous SiC buffer with variable C/Si compositions
(2016-01-22)
Cheng, Chih-Hsien
;
Tzou, An-Jye
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Chang, Jung-Hung
;
Chi, Yu-Chieh
;
Lin, Yung-Hsiang
The epitaxy of high-power gallium nitride (GaN) light-emitting diode (LED) on amorphous silicon carbide (a-SixC1-x) buffer is demonstrated. The a-SixC1-x buffers with different nonstoichiometric C/Si composition ratios are synthesized on SiO2/Si substrate by using a low-temperature plasma enhanced chemical vapor deposition. The GaN LEDs on different SixC1-x buffers exhibit different EL and C-V characteristics because of the extended strain induced interfacial defects. The EL power decays when increasing the Si content of SixC1-x buffer. The C-rich SixC1-x favors the GaN epitaxy and enables the strain relaxation to suppress the probability of Auger recombination. When the SixC1-x buffer changes from Si-rich to C-rich condition, the EL peak wavelengh shifts from 446 nm to 450 nm. Moreover, the uniform distribution contour of EL intensity spreads between the anode and the cathode because the traping density of the interfacial defect gradually reduces. In comparison with the GaN LED grown on Sirich SixC1-x buffer, the device deposited on C-rich SixC1-x buffer shows a lower turn-on voltage, a higher output power, an external quantum efficiency, and an efficiency droop of 2.48 V, 106 mW, 42.3%, and 7%, respectively.
Improvements in the reliability of a-InGaZnO thin-film transistors with triple stacked gate insulator in flexible electronics applications
(2015-11-30)
Chen, Hua-Mao
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Chang, Ting-Chang
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Tai, Ya-Hsiang
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Chen, Kuan-Fu
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Chiang, Hsiao-Cheng
This study examined the impact of the low-temperature stacking gate insulator on the gate bias instability of a-InGaZnO thin film transistors in flexible electronics applications. Although the quality of SiNx at low process/deposition temperature is better than that of SiOx at similarly low process/deposition temperature, there is still a very large positive threshold voltage (V-th) shift of 9.4 V for devices with a single low-temperature SiNx gate insulator under positive gate bias stress. However, a suitable oxide-nitride-oxide-stacked gate insulator exhibits a Vth shift of only 0.23 V. This improvement results from the larger band offset and suitable gate insulator thickness that can effectively suppress carrier trapping behavior. (C) 2015 Elsevier B.V. All rights reserved.
Laminin modification subretinal bio-scaffold remodels retinal pigment epithelium-driven microenvironment in vitro and in vivo
(2016-10-04)
Peng, Chi-Hsien
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Chuang, Jen-Hua
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Wang, Mong-Lien
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Jhan, Yong-Yu
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Chien, Ke-Hung
Advanced age-related macular degeneration (AMD) may lead to geographic atrophy or fibrovascular scar at macular, dysfunctional retinal microenvironment, and cause profound visual loss. Recent clinical trials have implied the potential application of pluripotent cell-differentiated retinal pigment epithelial cells (dRPEs) and membranous scaffolds implantation in repairing the degenerated retina in AMD. However, the efficacy of implanted membrane in immobilization and supporting the viability and functions of dRPEs, as well as maintaining the retinal microenvironment is still unclear. Herein we generated a biomimetic scaffold mimicking subretinal Bruch\'s basement from plasma modified polydimethylsiloxane (PDMS) sheet with laminin coating (PDMS-PmL), and investigated its potential functions to provide a subretinal environment for dRPE-monolayer grown on it. Firstly, compared to non-modified PDMS, PDMS-PmL enhanced the attachment, proliferation, polarization, and maturation of dRPEs. Second, PDMS-PmL increased the polarized tight junction, PEDF secretion, melanosome pigment deposit, and phagocytotic-ability of dRPEs. Third, PDMS-PmL was able to carry a dRPEs/ photoreceptor-precursors multilayer retina tissue. Finally, the in vivo subretinal implantation of PDMS-PmL in porcine eyes showed well-biocompatibility up to 2-year follow-up. Notably, multifocal ERGs at 2-year follow-up revealed well preservation of macular function in PDMS-PmL, but not PDMS, transplanted porcine eyes. Trophic PEDF secretion of macular retina in PDMS-PmL group was also maintained to preserve retinal microenvironment in PDMS-PmL eyes at 2 year. Taken together, these data indicated that PDMS-PmL is able to sustain the physiological morphology and functions of polarized RPE monolayer, suggesting its potential of rescuing macular degeneration in vivo.
Lasing characteristics of a GaN photonic crystal nanocavity light source
(2007-07-23)
Lai, Chun-Feng
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Yu, Peichen
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Wang, Te-Chung
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Kuo, Hao-Chung
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Lu, Tien-Chang
Lasing characteristics from photonic crystal defects fabricated on bulk GaN are investigated. The device demonstrates multimode lasing with linewidths as narrow as 2-3 angstrom, and an enhanced spontaneous emission factor beta similar to 0.045. The emission spectra indicate that the laser emission is initiated horizontally in the defect nanocavity and then coupled to the vertical radiation, possibly via photonic crystal Bloch modes or by scattering.
Nonstoichiometric SiC Bus/Ring Waveguide Based All-Optical Data Format Follower and Inverter
(2016-05)
Su, Sheng-Pin
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Wu, Chung-Lun
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Cheng, Chih-Hsien
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Huang, Bo-Ji
;
Wang, Huai-Yung
Nonstoichiometric silicon carbide (SiC) bus/ring waveguide resonator based all-optical data-format follower and inverter is demonstrated to perform ultrafast dual functional wavelength and data-format conversion. The buried Si quantum dots (Si-Qps) with strong quantum confinement effect effectively result in a significant change on the nonlinear refractive index of 3.14 X 10(-1)3 cm(2)/W, which induces a red shift of 0.07 nm on the resonant wavelength comb of the nonstoichiometric SiC ring waveguide resonator. By injecting the 12 Gbit/s optical pulsed return-to-zero on-off keying (PRZ-OOK) data stream into the ring waveguide at a notched wavelength of 1551.08 nm, the induced red-shift on resonant wavelengths allows versatile all-optical data processing functions, including data wavelength conversion and data format following/inversion, on the data patterns transferred to the probe. The eye-opening diagram analysis at 12 Gbit/s reveals that the data transferred to the probe can provide a signal-to-noise ratio of 9.4 dB, and a receiving power penalty is degraded by 2.6 dB as compared to that of the pump data.
Pre-Chirped Pulse Excitation Enhanced Terahertz Radiation
(2016-03)
Lee, Chao-Kuei
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Lin, Yuan-Yao
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Lin, Gong-Ru
;
Wu, Chung-Lun
;
Wu, Tsung-Han
The enhanced broadband THz radiation excited by pre-chirping the femtosecond pumping laser pulse is explored from a photoconductive antenna made by the low-temperature molecular-beam-epitaxy (LT-MBE) grown Gallium Arsenide (GaAs). Nearly 3-dB enlargement on peak amplitude of THz radiation accompanied with broadened bandwidth is achieved with positively chirped pulse excitation. The laser with short pulsewidth assists the broadening of THz bandwidth, whereas the peak intensity of THz relies strictly on lengthened carrier lifetime. The enhancement of high-frequency radiation components at low pumping intensity also indicates the nature of power dependence in such a coherently controlled process. When photocurrent saturation occurs in the LT-MBE-grown GaAs under high-power pumping condition, the clipping effect on peak amplitude of current pulse lengthens the duration of current surge effect. Both the peak intensity and the frequency spectrum of the generated THz pulse concurrently declines. The physical mechanism related to pre-chirped pulse excitation dependent carrier dynamics is proposed to elucidate the spectral response as well as the power dependence in such a coherently controlled THz radiation process.
Robustness of a Topologically Protected Surface State in a Sb2Te2Se Single Crystal
(2016-11-18)
Lee, Chao-Kuei
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Cheng, Cheng-Maw
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Weng, Shih-Chang
;
Chen, Wei-Chuan
;
Tsuei, Ku-Ding
A topological insulator (TI) is a quantum material in a new class with attractive properties for physical and technological applications. Here we derive the electronic structure of highly crystalline Sb2Te2Se single crystals studied with angle-resolved photoemission spectra. The result of band mapping reveals that the Sb2Te2Se compound behaves as a p-type semiconductor and has an isolated Dirac cone of a topological surface state, which is highly favored for spintronic and thermoelectric devices because of the dissipation-less surface state and the decreased scattering from bulk bands. More importantly, the topological surface state and doping level in Sb2Te2Se are difficult to alter for a cleaved surface exposed to air; the robustness of the topological surface state defined in our data indicates that this Sb2Te2Se compound has a great potential for future atmospheric applications.