Browsing by Author "SHIEH, JM"

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BIREFRINGENCE-INDUCED SPECTRAL FEATURES IN CONTINUOUS-WAVE AND PASSIVELY MODE-LOCKED TI-SAPPHIRE LASERS
(1992-11-01)
PAN, CL
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HWANG, CD
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KUO, JC
;
SHIEH, JM
;
WU, KH
We show that the transient spectrum of a continuous-wave Ti:sapphire laser during the initial stage of the buildup, which exhibits multiple clusters (of longitudinal modes), is due to the spectral windowing effect of the Brewster-angle-cut Ti:sapphire crystal, which acts as a birefringent filter in the laser cavity. This effect is also responsible for certain spectral features of a passively mode-locked Ti:sapphire/DDI laser.
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.
COMPLETELY SELF-STARTING PICOSECOND AND FEMTOSECOND KERR-LENS MODE-LOCKED TI-SAPPHIRE LASER
(1995-05-01)
SHIEH, JM
;
GANIKHANOV, F
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LIN, KH
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HSIEH, WF
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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.
DYNAMIC PULSE EVOLUTION IN SELF-STARTING PASSIVELY MODE-LOCKED TI-SAPPHIRE DDI LASERS
(1994)
PAN, CL
;
HWANG, CD
;
PU, NW
;
SHIEH, JM
;
光電工程學系
EFFECT OF DYE CONCENTRATION ON PICOSECOND AND FEMTOSECOND CW PASSIVELY MODE-LOCKED TI-SAPPHIRE DDI LASERS
(1992-10-15)
PAN, CL
;
HWANG, CD
;
KUO, JC
;
SHIEH, JM
;
WU, KH
The role of the saturable absorber dye DDI in the cw passively mode-locked Ti:sapphire/DDI laser both with and without compensation prisms is investigated. This laser self-starts when the concentration of the dye is greater than almost-equal-to 2 X 10(-4) M for both picosecond and femtosecond pulses. With the prism pair, the laser generates Gaussian pulses 150 fs in duration. The corresponding spectrum is sech2 in shape with a FWHM of 8 nm. These parameters are independent of the DDI concentration. Without the prism pair, the laser generates picosecond pulses with the FWHM decreasing from 8 to 3 ps as the dye concentration is increased from 2.5 x 10(-4) to 1 X 10(-3) M. Concurrently the pulse shape changes from a Lorentzian to a nearly symmetric two-sided exponential shape. The picosecond spectra for different dye concentrations are also presented.
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.
STARTING DYNAMICS OF A CW PASSIVELY MODE-LOCKED PICOSECOND TI SAPPHIRE DDI LASER
(1995-01-15)
PU, NW
;
SHIEH, JM
;
LAI, YC
;
PAN, CL
;
交大名義發表
We show that, for a cw passively mode-locked picosecond Ti:sapphire/DDI laser, the first autocorrelation trace with negligible cw background occurs at a delay time of 20 mus, or 1600 round trips from the first relaxation-oscillation peak. The trace suggests that the pulse consists of a primary pulse as short as 4.4 ps and of small secondary pulses that form a much wider pedestal of the trace, each containing almost-equal-to 50% of the photon energy. Nearly transform-limited almost-equal-to5-ps-wide Gaussian pulses were observed at a delay time of 40 mus. After 45 mus, the optical spectrum broadened considerably, and the time-bandwidth product increased to 4 in the steady state (after 60 mus).