Browsing by Author "CHANG, CS"

Now showing 1 - 14 of 14

BUILDUP DYNAMICS OF THE SPECTRUM AND THE AVERAGE OUTPUT POWER OF A HOMOGENEOUSLY BROADENED CONTINUOUS-WAVE TI-SAPPHIRE LASER
(1992-07-15)
PAN, CL
;
KUO, JC
;
HWANG, CD
;
SHIEH, JM
;
LAI, Y
The buildup dynamics of a homogeneously broadened continuous-wave Ti:sapphire laser is experimentally investigated for the first time to our knowledge. The average output power of the laser exhibits relaxation oscillation behavior initially and approaches the steady-state value in almost-equal-to 20-mu-s. Concurrently, the longitudinal-mode spectrum evolves from a multicluster spectral distribution (tentatively attributed to the spectral windowing effect of the Brewster-angle-cut Ti:sapphire crystal as a birefringent filter) to a single cluster at 787.5 nm. The spectral narrowing (which is due to gain competition in the homogeneously broadened medium), however, takes almost-equal-to 500-mu-s. Physical mechanisms that explain qualitatively the two distinctive time scales are presented.
BUILDUP OF STEADY-STATE PICOSECOND PULSES IN AN ACTIVELY MODE-LOCKED LASER-DIODE ARRAY
(1991-09-01)
KUO, JC
;
CHANG, CS
;
PAN, CL
;
交大名義發表
;
光電工程學系
We have studied experimentally the temporal and spectral characteristics of an actively mode-locked laser-diode array in an external cavity as it evolves to the steady state. It is found that the buildup time to steady-state picosecond pulses takes less than 45 round trips. The number of clusters of the longitudinal-mode spectrum reduces during the evolution and finally approaches a steady-state spectral distribution with the pulse energy mainly distributed among a few clusters near the line center.
DIAMOND FILM GROWTH ON CEMENTED TUNGSTEN CARBIDES STUDIED BY SEM, AES AND XPS
(1992-11-23)
CHEN, JL
;
HUANG, TH
;
PAN, FM
;
KUO, CT
;
CHANG, CS
Diamond films were deposited on cemented WC substrates using a hot filament chemical vapor deposition (CVD) system with a mixture of CH4 and H-2 as the source gases. The effect of the surface pretreatments of scratching the surface and etching to remove the surface Co from the substrate on diamond nucleation and growth was studied. The effect of CH4 Concentration on diamond growth was also examined. Scanning electron microscopy, Auger electron, X-ray photoelectron and energy dispersive spectroscopies were used to examine the film morphology, quality and compositions. The results show that a good diamond-crystal quality can be obtained by reducing the surface Co content in the substrate to below 1%. Co in the surface layer of the substrate inhibits both diamond nucleation and growth. Polishing and etching treatments to scratch the surface and to remove the surface Co of the substrates are essential to maintain the surface roughness in an appropriate range to obtain diamond films with a good quality and adhesion. A change in CH4 Concentration in the source gases from 0.5 to 0.15% can change the preferred orientation of the diamond films fro m the {100} to the {111} plane.
ELECTRICAL CHARACTERIZATION OF ARSENIC-ION-IMPLANTED SEMIINSULATING GAAS BY CURRENT-VOLTAGE MEASUREMENT
(1994-12-19)
LIN, GR
;
CHEN, WC
;
CHANG, CS
;
PAN, CL
;
光電工程學系
ELECTROOPTIC SAMPLING OF OPTOELECTRONICALLY PHASE-LOCKED 10.0 GHZ MICROWAVE SIGNALS USING SEMICONDUCTOR-LASER DIODES
(1991-08-29)
WU, HH
;
CHANG, CS
;
PAN, CL
;
光電工程學系
;
電信研究中心
10.0 GHz microwave signals optoelectronically phase locked by a laser-diode-based GaAs: Cr photoconductive harmonic mixer (lambda = 0.81-mu-m) have been measured noninvasively using the electro-optic sampling technique with a pin-switched InGaAsP laser diode (lambda = 1.3-mu-m).
LOW-TEMPERATURE EPITAXY OF GAAS BY METALORGANIC CHEMICAL-VAPOR-DEPOSITION
(1994-08-01)
CHEN, WK
;
CHANG, CS
;
CHEN, WC
;
電子物理學系
;
光電工程學系
The low-temperature (LT) epitaxial growth of high quality GaAs films is achieved by using triethylgallium and tertiarybutylarsine as the precursors. Without any external work, the deposition can be conducted at a temperature as low as 350-degrees-C in a conventional metalorganic chemical vapor deposition system. The full width at half-maximum of 77 K photoluminescence and X-ray rocking curve for a sample grown at 425-degrees-C are 8.2 meV and 14 arcsec, respectively. Materials with good electrical properties were also obtained. A Schottky diode formed on the LT CaAs epilayer shows a barrier height of 0.83 eV, and a reverse saturation current of 1.1 X 10(-7) A/cm2, comparable to that of a normal GaAs Schottky diode.
OPTOELECTRONIC PHASE-TRACKING AND WAVE-FORM DISPLAY OF MICROWAVE SIGNALS UP TO 8 GHZ USING GAIN-SWITCHED LASER-DIODES
(1994-05-15)
WU, HH
;
WANG, CL
;
LIN, GR
;
CHANG, CS
;
PAN, CL
We present a new, more versatile scheme for maintaining phase coherence between optical probe pulses and microwave signals under test in a laser-diode-based optoelectronic sampling system. This approach takes advantage of the relative ease of changing the repetition rate of the gain-switched laser diode (GSLD). The microwave signal to be sampled is used as the clock signal for phase-locking of a voltage controlled-oscillator (VCO) which drives the GSLD. Phase-tracking and display of waveforms at frequencies up to 8 GHz have been realized. It is also shown that lower phase noise sidebands for the phase-locked VCO can be realized by locking the higher harmonics of the laser pulse to the microwave clock.
OPTOELECTRONIC SYNCHRONIZATION OF DISTRIBUTED MICROWAVE-OSCILLATORS USING SEMICONDUCTOR-LASER DIODES
(1992-09-01)
WU, HH
;
CHANG, CS
;
PAN, CL
;
交大名義發表
;
光電工程學系
We report a laser-diode-based system for optoelectronic synchronization of two distributed microwave oscillators at 10-GHz. The relative phase between the 10-GHz signals can be continuously tuned over a complete cycle by an optical delay line. Phase-locking of the two oscillators with a frequency offset of 10 kHz is also demonstrated. This method can be used to synchronize millimeter-wave oscillators for distributed architectures via fiber-optic links in the future.
PULSE BUILDUP DYNAMICS OF AN ACTIVELY MODE-LOCKED LASER-DIODE ARRAY IN THE EXTERNAL-CAVITY
(1995-03-01)
WANG, CL
;
KUO, JC
;
CHANG, CS
;
PAN, CL
;
交大名義發表
Dynamic pulse evolution characteristics of an actively mode-locked laser diode array in the external cavity have been investigated, Numerical calculations based on modified traveling-wave rate equations reproduce experimentally observed pulse and spectral width evolution and show that the buildup time is about 45 round-trips, We have also performed a theoretical analysis to understand which of the laser operating parameters would affect the buildup dynamics, It is shown that either higher de bias current or larger radiative recombination coefficient (which is inversely proportional to the excited-state lifetime) will render the laser exhibiting shorter steady-state pulse width and faster evolution to the steady state, Other parameters affecting the buildup, but to a lesser extent, include the radio-frequency (RF) modulation current, spontaneous emission coefficient, and gain coefficient, The power reflectivities of the output mirror and the antireflection coated diode facet, on the other hand, have little effect on the pulse width and buildup time for single pulse generation.
PULSE-FORMING DYNAMICS OF A CW PASSIVELY MODE-LOCKED TI-SAPPHIRE DDI LASER
(1992-03-01)
KUO, JC
;
SHIEH, JM
;
HWANG, CD
;
CHANG, CS
;
PAN, CL
The dynamics of pulse formation in a cw passively mode-locked Ti:sapphire/DDI laser has been investigated. It is found that the time required for the circulating energy in the cavity to build up and bleach the dye absorber is approximately 140-mu-s. A further 230-mu-s is required for the buildup of steady-state picosecond pulses. Concurrently the laser output spectrum initially narrows in the cw regime, begins to broaden as the laser becomes modulated, and finally establishes the steady-state spectral distribution.
SUBPICOSECOND CARRIER LIFETIMES IN ARSENIC-ION-IMPLANTED GAAS
(1995-12-04)
GANIKHANOV, F
;
LIN, GR
;
CHEN, WC
;
CHANG, CS
;
PAN, CL
We have investigated photoexcited carrier lifetimes in arsenic-ion-implanted semi-insulating GaAs by time-resolved reflectivity measurements. Subpicosecond carrier lifetimes (220 to 550 fs) which do not exhibit apparent dosage dependence for samples bombarded with 200 keV arsenic ions at increasing dosages in the range of 10(12) and 10(16) ions/cm(2) are reported. The shortest carrier lifetime was observed for the sample irradiated at 10(13) ions/cm(-2). These are the shortest lifetimes ever observed for ion-damaged GaAs and comparable to those of low-temperature molecular beam epitaxially grown GaAs, which is also nonstoichiometric with excess-arsenic-related, deep-level defects. (C) 1995 American Institute of Physics.
TRIBOLOGICAL BEHAVIORS OF THE DIAMOND-COATED CEMENTED CARBIDE TOOLS WITH VARIOUS COBALT CONTENTS
(1992-04-15)
HUANG, TH
;
KUO, CT
;
CHANG, CS
;
KAO, CT
;
WEN, HY
VOLTAGE-CONTROLLED 3 TERMINAL GAAS NEGATIVE DIFFERENTIAL RESISTANCE DEVICE USING N+-I-P+-I-N+ STRUCTURE
(1990-06-01)
YARN, KF
;
WANG, YH
;
CHANG, CY
;
CHANG, CS
;
電控工程研究所
WEAR BEHAVIOR OF VARIOUS DIAMOND-COATED CUTTING TOOLS UNDER DIFFERENT DEPOSITION CONDITIONS
(1993-04-13)
HUANG, TH
;
KUO, CT
;
LIN, TS
;
CHANG, CS
;
材料科學與工程學系
A hot-filament-assisted chemical vapour deposition system was used to deposit diamond films on cemented carbide cutting tools with Co contents ranging from 6% to 22%. The surface roughness and friction coefficient of the films were measured under different deposition conditions. A block-on-ring tribotester and scanning electron microscopy were adopted to characterize the tribological behaviour and the film morphology. The results indicate that the cutting performance of the diamond-coated tools is closely related to the friction coefficient and surface roughness of the film and that the friction coefficient is a function of the surface roughness and film quality. For the 6% Co substrate the film deposited under 0.5% CH4 Concentration shows the best film quality and the lowest friction coefficient and its surface roughness is within the optimum range 0.06-0.25 mum; therefore it shows better cracking resistance and wear resistance.