Browsing by Author "HSIEH, WF"

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ANALYTICAL DESIGN OF SYMMETRICAL KERR-LENS MODE-LOCKING LASER CAVITIES
(1994-05-01)
LIN, KH
;
HSIEH, WF
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交大名義發表
;
光電工程學系
;
National Chiao Tung University
Analytical expressions for the spot size and the Kerr-lens mode-locking (KLM) strength can be represented as explicit functions of the Position in the cavity, the laser power, and the stability parameter for a four-mirror figure-Z laser resonator. The results indicate that the KLM strength achieves its maximum value at the edge of the stability range. Self-amplitude modulation and group-velocity dispersion compensation can be established by a prism pair. Simultaneously obtaining a large pumping efficiency and KLM is possible for this cavity.
CHARGE-COUPLED DEVICE POLARIMETRY AND ITS MEASUREMENT OF THE STOKES VECTOR OF LIGHT TRANSMITTED BY A POLYMER PLATE
(1991-10-01)
CHAO, YF
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HSIEH, WF
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交大名義發表
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光電工程學系
;
National Chiao Tung University
The Stokes vector of light transmitted by a polycarbonate plate is studied by a modified charge-coupled device polarimeter. A sheet polarizer is measured for comparison.
COMPLETELY SELF-STARTING PICOSECOND AND FEMTOSECOND KERR-LENS MODE-LOCKED TI-SAPPHIRE LASER
(1995-05-01)
SHIEH, JM
;
GANIKHANOV, F
;
LIN, KH
;
HSIEH, WF
;
PAN, CL
Completely self-starting and stable operation of a Kerr-lens mode-locked Ti:sapphire laser was realized in both picosecond and femtosecond regimes. The cavity has a symmetric X configuration with soft aperturing. Enhanced Kerr nonlinearity and reduced backscattering effects were thought to be key to obtaining stable self-starting self-mode-locked operation from 765 to 815 nm far the picosecond regime and from 770 to 835 nm for the femtosecond regime. The mode-locking starting time as measured by the onset of the second-harmonic signal ranged from 300 ms to 2 s, depending on cavity alignment. Preliminary data also suggest that intracavity intensity fluctuation necessary for the laser to evolve into stable mode locking could be as short as 10-40 ps.
HEURISTIC MODEL FOR THE GROWTH AND COUPLING OF NONLINEAR PROCESSES IN DROPLETS
(1992-06-01)
SERPENGUZEL, A
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CHEN, G
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CHANG, RK
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HSIEH, WF
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光電工程學系
Standard one-dimensional nonlinear-wave equations are modified to accommodate the growth and coupling of nonlinear waves in droplets. The propagation direction of the nonlinear waves along the length of an optical cell is changed so that it is along the droplet rim. The model includes radiation losses because of nonzero absorption, leakage from the droplet, and depletion in generating other nonlinear waves. For multimode-laser input, the growth and decay of the first- through fourth-order Stokes stimulated Raman scattering (SRS) are calculated as a function of the phase matching of the four-wave mixing process and the model-dependent Raman gain coefficient. The Raman gain coefficient determines the delay time of the first-order SRS, while the phase matching determines the correlated temporal profiles of the multiorder SRS. Both the Raman gain and the phase matching are found to be enhanced in the droplet. The spatial distribution of the internal input-laser intensity is calculated by using the Lorenz-Mie formalism. The temporal profile of the input-laser intensity used in the calculations is identical to the experimentally observed laser time profile. The delay time and the correlated growth and decay of nonlinear waves resulting from the numerical simulation compare favorably with those of the experimental observations. Similar calculations are made for single-mode-laser input for which the stimulated Brillouin scattering (SBS) achieves its threshold before the SRS does and subsequently pumps the SRS.
HIGH ORIENTATION CDS THIN-FILMS GROWN BY PULSED LASER AND THERMAL EVAPORATION
(1992-05-01)
DAI, CM
;
HORNG, L
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HSIEH, WF
;
SHIH, YT
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TSAI, CT
Undoped CdS films have been grown by pulsed laser evaporation (PLE) and thermal evaporation (TE) techniques on Corning's 7059 glass at a substrate temperature between room temperature and 250-degrees-C. The deposition rates are 0.07 angstrom/s for PLE and 60 angstrom/s for the TE technique. These as-deposited films have high (002) preferred orientation by both techniques even without preheating the substrate. However, films deposited by PLE have more preferred orientation and larger grain size. These features make the PLE films have sharper Raman peaks, smaller Raman shift of surface mode and more overtones of longitudinal optical phonon mode observed than those in TE films. The transparency of PLE or TE films for wavelengths which are larger than that of absorption edge is around 90% on average.
LASER-INDUCED RADIATION LEAKAGE FROM MICRODROPLETS
(1993-04-01)
CHEN, G
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CHOWDHURY, DQ
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CHANG, RK
;
HSIEH, WF
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光電工程學系
Intensity distributions on the droplet surface and within the droplet are calculated and found helpful in explaining the observed laser-induced radiation leakage from various locations on or within the droplet. In an attempt to distinguish various possible mechanisms for laser-induced perturbation of micrometer-sized droplets, two types of experiment are conducted, and the measured intensity distribution is compared with that predicted by theoretical computation. The observed extra-light leakage of dye-laser radiation trapped in the droplet can be grouped into quasi-instantaneous and cumulative effects. One set of experiments uses a variable number of 100-ps laser pulses because of the laser's low fluence at 0.1 GW/cm2. Quasi-instantaneous perturbations associated with an intensity-dependent index of refraction change are found to be important. Cumulative perturbations become evident as the number of 100-ps pulses increases. The second set of experiments uses one green laser beam and one near-IR laser beam, both with 7-ns duration, which because of the high fluence emphasize the electrostrictive- and temperature-related perturbations. Extra leakage from surface perturbations caused by the laser-induced temperature rise cannot be isolated but is found not to be dominant.
RAMAN INTENSITY ENHANCEMENT OF THE SI PEAK BY CDS THIN-FILMS
(1991-12-16)
DAI, CM
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CHUU, DS
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HSIEH, WF
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交大名義發表
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電子物理學系
A method, which utilizes interference enhanced Raman scattering and resonant Raman scattering techniques, is used to overcome the low efficiency of Raman methods to diagnose highly reflective materials. As applied to the p-type Si wafer, the enhanced gain is up to nearly a factor of 80 at 4880 angstrom excitation. Because of the strong absorption of the scattered light, it is recommended that the suitable deposited thickness of CdS films should not be thicker than 700 angstrom.
RAMAN INVESTIGATIONS OF THE SURFACE-MODES OF THE CRYSTALLITES IN CDS THIN-FILMS GROWN BY PULSED LASER AND THERMAL EVAPORATION
(1991-06-15)
CHUU, DS
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DAI, CM
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HSIEH, WF
;
TSAI, CT
;
電子物理學系
CdS films have been grown on Corning glass by pulsed laser evaporation (PLE) and thermal evaporation (TE) techniques at a substrate temperature between room temperature and 250-degrees-C. The quality of these films is investigated by resonance Raman scattering, x-ray diffraction and optical transmittance. Our results reveal that the Raman shifts of the surface phonon mode are observed with 300 and 297 cm-1 by PLE and TE techniques, respectively, and as many as four overtones are obtained by PLE method. The difference of Raman shift between these two techniques are caused by the discrepancy of crystallite sizes which is larger for PLE technique. The crystallite sizes are in the range of 200-500 angstrom in diameter. Highly oriented films have been grown by both of the techniques even when the substrate is at room temperature.
SIMPLE ANALYTICAL METHOD OF CAVITY DESIGN FOR ASTIGMATISM-COMPENSATED KERR-LENS MODE-LOCKED RING LASERS AND ITS APPLICATIONS
(1995-03-01)
LIN, KH
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LAI, YC
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HSIEH, WF
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交大名義發表
;
光電工程學系
An analytical method based on a renormalized q parameter for Gaussian-beam propagation and properly matched self-consistent complex q parameters is proposed to aid in the design of arbitrary-astigmatism-compensated Kerr-lens mode-locked ring cavity lasers. The q parameters throughout the ring cavity can be calculated by solution of an algebraically quadratic equation for an arbitrarily thick Kerr medium when the intracavity laser power is less than the self-trapping power. The Kerr-lens mode-locking strength at the curved mirror was calculated over the stable range. The results indicate that the astigmatism is best compensated so that the stable range of x and y directions have optimal overlapping. Although to maximize the hard-aperturing effect the curved mirror separation must be at the far edge of the stable range, pump and cavity field matching inside the Kerr medium is also necessary. In addition, the insertion of a vertical slit is more effective than insertion of a horizontal slit. A spiking phenomenon is found in the intracavity z scan curve, which can be observed only with thick Kerr materials and a high laser power.
THE INVESTIGATION OF ER-DOPED GLASSES BY 2-STEP HYDROLYSIS WITH N,N-DIMETHYL FORMAMIDE
(1994)
FRAN, YS
;
TSENG, TY
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HSIEH, WF
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
THE ROLE OF DRYING-CONTROL CHEMICAL ADDITIVES ON THE PREPARATION OF SOL-GEL DERIVED PLZT THIN-FILMS
(1993-12-15)
CHANG, DA
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CHOH, YH
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HSIEH, WF
;
LIN, P
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TSENG, TY
Films of Pbx/100La(x)/100(Zry/100 Tiz/100)1-x/400O3 with x = 8, y = 65 and z = 35 (PLZT(8/65/35)) with a single perovskite structural phase were successfully prepared by using drying-control chemical additives in sol-gel processing followed by rapid thermal annealing at 600-degrees-C for only 1 min on Si(Pt) substrates. The roles of the drying-control chemical additives ethylene glycol and formamide in the gel preparation were studied. The hysteresis loop of PLZT(8/65/35) thin film was measured. The remanent polarization and coercive field were found to be about 1.3 muC cm-2 and 15 kV cm-1, respectively.
TRANSIENT-RESPONSE OF A THRESHOLDLESS MICRODROPLET DYE-LASER
(1991-10-15)
LIN, KH
;
HSIEH, WF
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光電工程研究所
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Institute of EO Enginerring
Lasing in a cavity formed by a dye-doped micrometer-sized liquid droplet showed a new thresholdless steady-state behavior and a time-dependent response. The thresholdless behavior is associated with enhancement and inhibition of the spontaneous emission. The time-dependent response is related to various quality factors of the cavity modes and was determined to be 8 x 10(8).
TRANSIENT-RESPONSE OF A THRESHOLDLESS MICRODROPLET DYE-LASER
(1991-10-15)
LIN, KH
;
HSIEH, WF
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
Lasing in a cavity formed by a dye-doped micrometer-sized liquid droplet showed a new thresholdless steady-state behavior and a time-dependent response. The thresholdless behavior is associated with enhancement and inhibition of the spontaneous emission. The time-dependent response is related to various quality factors of the cavity modes and was determined to be 8 x 10(8).