Browsing by Author "Hsu, YK"

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Design and implementation of a distributed monitor facility
(1997-01-01)
Yuan, SM
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Hsu, YK
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交大名義發表
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資訊工程學系
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National Chiao Tung University
There are four major drawbacks to use existing mechanisms, such as which are provided by Mach and Masscomp, etc., for designing monitors. (1) They cannot support fault-tolerance. (2) They are tailor-made for specific kernels. (3) They cannot directly be applied in distributed environments. (4) Users must have good backgrounds in handling light-weight processes. In this paper, we present a distributed monitor facility, called DISMON, that supports the mechanisms needed to design monitors and makes them fault tolerant to hardware failures. At the same time, monitors are constructed at the application level not kernel level such that they are portable and easily designed. In order to produce a monitor, the source monitor program, which makes use of a C-like language to code it in the DISMON, is pre-compiled by a monitor generation program, called MONGEN, to generate it. The monitor procedure calls are made entirely transparent by means of an agent based name server that helps callers to obtain the address of a monitor. The interface between callers and monitor are similar to the Sun's Remote Procedure Call (RPC) mechanism, but the RPC servers have been replaced by monitors.
Difference-frequency mixing of output waves from a periodically poled lithium niobate optical parametric oscillator in a GaSe crystal
(2002-08-01)
Haidar, S
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Hsu, YK
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Chang, CS
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Wang, SC
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Ito, H
We report on an optical parametric oscillator (OPO) based on periodically poled lithium niobate (PPLN) pumped by a Nd:YAG laser, and on extending its tuning range by difference-frequency mixing of OPO output waves in GaSe crystal. Maximum combined signal and idler pulse energy of 2.7 mJ and slope efficiency of 25% have been achieved. The tuning range is 1.71 to 1.98 mum for the signal wave and 2.81 to 2.30 mum for the idler wave, using a single set of mirrors. As an application of this PPLN OPO, the signal and the idler waves are difference-frequency-mixed in a GaSe crystal to produce tunable mid-IR from 4.35 to 14.25 mum. The efficiency of the mixing has been analyzed, considering the experimental results. (C) 2002 Society of Photo-optical Instrumentation Engineers.
Electrical properties of GaSe doped with Er
(2004-08-01)
Hsu, YK
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Chang, CS
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Huang, WC
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光電工程學系
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Department of Photonics
Measurements of the Hall effect and Er-related luminescence were made on Er-doped GaSe. Deep-level transient spectroscopy (DLTS) was also performed. Hall measurements show that hole concentrations of 0.2%, 0.5%, and 1% Er-doped GaSe samples are 1.5x10(17)-6x10(17) cm(-3) at room temperature, and that the mobility of these holes is in the range 22-34 cm(2)/V s. The temperature dependence of the hole concentration is explained using the two-acceptor model, in which one acceptor level is at around 65 meV above the valence band and the other one is at similar to158 meV. The DLTS measurements yield similar results. Furthermore, the shallow acceptor impurities contribute free hole carriers and act as radiative centers; the deep acceptor impurities are nonradiative centers, which are responsible for the quenching behavior of Er-related luminescence. The temperature dependence of the hole mobility can be understood as the combined scatterings of homopolar optical phonons and ionized impurities. (C) 2004 American Institute of Physics.
Erbium doped GaSe crystal for mid-IR applications
(2006-06-12)
Hsu, YK
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Chen, CW
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Huang, JY
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Pan, CL
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光電工程學系
We reported a type-I difference-frequency generator (DFG), based on erbium doped GaSe (Er: GaSe) crystals as a coherent infrared source tunable from 2.4 mu m to 28 mu m. The two mixing beams used for the DFG are a tunable near infrared output (1.1-1.8 mu m) from an optical parametric amplifier (OPA) and the fundamental beam of a picosecond Nd: YAG laser at 1.064 mu m. The system can produce a maximum output pulse energy of 5 mu J at wavelength of 3.5 mu m, corresponding to a photon conversion efficiency of 8% at a pump intensity of 1.7 GW/cm(2). The nonlinear coefficient (d(eff)) of 0.5 atom % erbium doped GaSe crystal was found to be 55.3 pm/V or 24 % higher than that of a pure GaSe crystal. The improvement of deff is attributed to the substitutive and interstitial doping of Er ion in GaSe unit cell. The optical properties of GaSe influenced by the erbium doping are also presented. (c) 2006 Optical Society of America.
Fabrication and optical property of GaSe thin films grown by pulsed laser deposition
(2003-08-01)
Lee, SH
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Hsu, YK
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Hsu, HC
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Chang, CS
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Hsieh, WF
The highly oriented (001) GaSe film on c-cut sapphire (0001) was successfully fabricated by pulsed laser deposition. As growth temperature decreases from 550degreesC to 375degreesC, the structure of films changes from cubic zinc-blende Ga2Se3 phase to GaSe phase. The growth temperature of the critical transition from Ga2Se3 phase to GaSe phase is around 500degreesC . From atomic force microscope (AFM) results, it is observed that the growth process of GaSe film is in the manner of layer plus island growth. Besides, the optimal growth conditions of as-grown GaSe film were obtained at a substrate temperature of 400degreesC and laser energy density of 11.7J/cm(2). When the thickness of films goes beyond 800 Angstrom, the stress will be released and the thickness of 1200 Angstrom results in an optimal GaSe film. Furthermore, the indirect bound exciton emission and the recombination via impurity levels or structural defects were observed from low-temperature photoluminescence measurement.
Intense picosecond infrared pulses tunable from 2.4-m to 38-m for nonlinear optics applications
(2005)
Chen, CW
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Hsu, YK
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Huang, JY
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Chang, CS
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Pan, CL
We report an intense picosecond infrared light source on microjoule energy level, widely tunable in the 2.4 - 38. m with pulse durations similar to 5ps by DFG in GaSe. The maximum photon conversion efficiency is greater than 43%.
Photoluminescence study of GaSe doped with Er
(2003-07-01)
Hsu, YK
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Chang, CS
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Hsieh, WF
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光電工程學系
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Department of Photonics
The Er-doped GaSe crystal has been investigated by using temperature dependent photoluminescence (TDPL), a Fourier-transform infrared spectrometer (FTIR), and Hall effect measurements. The Er-doped GaSe appears to be a p-type semiconductor. The impurity level at similar to2.064 eV is observed and located at similar to64 meV above the valence band in both the as-grown and the annealed Er doped GaSe crystal. Additionally, the infrared luminescence and transmission spectra which have arisen from the intracenter transitions 4I(9/2) --> 4I(15/2), 4I(11/2) --> 4I(15/2), and 4I(13/2) --> 4I(15/2) of erbium ions have been observed at similar to0.81, 0.99, and 1.54 mum, respectively. The annealing process under excess Se atmosphere at 600degreesC for 72 h can enhance the crystal to have more active erbium ions.
Synthesis of bulk beta-FeSi2 crystal
(2002-06-01)
Hsu, YK
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Wang, JJ
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Chang, CS
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Wang, SC
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光電工程學系
The feasibility of adopting two methods to synthesizing the bulk crystal of beta-FeSi2, was examined: one involving two-step Bridgmann growth with a three-zone furnace and another invoking melting growth with a single zone furnace, As-grown iron disilicides were annealed in the furnaces at different temperatures for various durations, Experimental result,; indicate that a larger beta-FeSi, crystal can be obtained using the two-step fast Bridgmann growth method kith post-annealing at 1073 K for 300h. Fast cooling and adding some copper impurities to the raw materials were found to promote the growth of beta-FeSi2. The iron disilicide crystal. with a large contribution from the 8 phase, supported a higher thermoelectric power. A thermoelectric power of 450 muV/K was obtained at 300-900 K for the sample with copper doping The energy hand gap of beta-FeSi2 samples was about 0.82-0.88 eV. determined by measuring the temperature-dependent resistivity.