Browsing by Author "Zhuang, W. Z."

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> 100-kW linearly polarized pulse fiber amplifier seeded by a compact efficient passively Q-switched Nd:YVO4 Laser
(2012-11-01)
Zhuang, W. Z.
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Huang, W. C.
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Cho, C. Y.
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Huang, Y. P.
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Huang, J. Y.
We thoroughly develop compact high-peak-power Nd:YVO4/Cr4+:YAG passively Q-switched lasers (PQS) as the seed source of the fiber amplifier. We exploit a nearly hemispherical cavity to reach the second threshold criterion and systematically consider the thermal lensing effect and the mode-size matching in the overall optimization. Employing a Cr4+:YAG absorber with 70% initial transmission, we obtain a 50-kHz seed pulse train with the pulse duration of 4.8 ns and the pulse energy of 22 mu J at a pump power of 5.4 W. Injecting this seed laser into a polarization maintained Yb-doped fiber, the pulse energy and peak power at a pump power of 16 W are enhanced up to 178 mu J and 37 kW, respectively. We also use an absorber with 40% initial transmission to generate a 25 kHz pulse train with the pulse duration of 1.6 ns and the pulse energy of 36 mu J at a pump power of 5.4 W. With this seed laser, we find that the surface damage of the fiber limits the maximum pulse energy and peak power to be 192 mu J and 120 kW, respectively.
Comparative studies for Cr(4+):YAG crystal and AlGaInAs semiconductor used as a saturable absorber in Q-switched Yb-doped fiber lasers
(2009-11-09)
Huang, J. Y.
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Zhuang, W. Z.
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Huang, W. C.
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Su, K. W.
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Hu, C.
We demonstrate comparative studies for Cr(4+):YAG crystal and AlGaInAs quantum-well (QW) used as a saturable absorbers in passively Q-switched Yb-doped fiber lasers. Both saturable absorbers were designed to be possessed of nearly the same initial transmission. Under a pump power of 24 W, the average output powers were up to 14.4 W and 13.8 W obtained with the AlGaInAs QWs and with the Cr(4+):YAG crystal, respectively. The maximum pulse energies obtained with the Cr(4+):YAG crystal and with the AlGaInAs QWs were found to be 0.35 mJ and 0.45 mJ, respectively. (C) 2009 Optical Society of America
Comparative studies for Cr4+:YAG crystal and AlGaInAs semiconductor used as a saturable absorber in Q-switched Yb-doped fiber lasers
(2009-11-09)
Huang, J. Y.
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Zhuang, W. Z.
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Huang, W. C.
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Su, K. W.
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Hu, C.
We demonstrate comparative studies for Cr4+:YAG crystal and AlGaInAs quantum-well (QW) used as a saturable absorbers in passively Q-switched Yb-doped fiber lasers. Both saturable absorbers were designed to be possessed of nearly the same initial transmission. Under a pump power of 24 W, the average output powers were up to 14.4 W and 13.8 W obtained with the AlGaInAs QWs and with the Cr4+:YAG crystal, respectively. The maximum pulse energies obtained with the Cr4+:YAG crystal and with the AlGaInAs QWs were found to be 0.35 mJ and 0.45 mJ, respectively. (C) 2009 Optical Society of America
Efficient continuous-wave self-Raman Yb:KGW laser with a shift of 89 cm(-1)
(2013-10-21)
Chang, M. T.
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Zhuang, W. Z.
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Su, K. W.
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Yu, Y. T.
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Chen, Y. F.
We demonstrated a continuous-wave (CW) self-Raman laser with high conversion efficiency by using Yb:KGW as the Raman crystal. The first Stokes line of wavelength centered at 1095.2 nm with spectral bandwidth of 8 nm and the cascaded Raman conversion wavelength at 1109.5 nm with spectral bandwidth of 3.4 nm were observed with a Raman shift of 89 cm(-1) with respect to the fundamental laser wavelength at 1085.0 nm with spectral bandwidth of 10 nm. The CW Raman output power of 1.7 W was attained under the diode pump power of 7.8 W which corresponds to the slope efficiency and the diode-to-Stokes optical conversion efficiency of 26.6% and 21.8%, respectively. (C)2013 Optical Society of America
Generation of large orbital angular momentum from superposed Bessel beams corresponding to resonant geometric modes
(2012-04-20)
Chen, Y. F.
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Lin, Y. C.
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Zhuang, W. Z.
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Liang, H. C.
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Su, K. W.
We theoretically verify that a coherent superposition of nearly degenerate Bessel beams characterizes the family of resonant geometric modes in circular billiards. With the ray-wave correspondence, we experimentally exploit a large-aperture cylindrical waveguide to generate the resonant geometric modes with large orbital angular momentum. Furthermore, the free-space propagation of the geometric modes emerging from the cylindrical waveguide is demonstrated to display the transient dynamics of the coherent states released from a circular quantum billiard.
Generation of sub-terahertz repetition rates from a monolithic self-mode-locked laser coupled with an external Fabry-Perot cavity
(2015-01-01)
Chen, Y. F.
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Chang, M. T.
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Zhuang, W. Z.
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Su, K. W.
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Huang, K. F.
A novel scheme to multiply the repetition rate of a monolithic self-mode-locked laser for generating sub-terahertz pulse sources is successfully demonstrated. A coated Yb:KGW crystal is designed to achieve a self-mode-locked operation at a repetition rate of 24 GHz with an average output power exceeding 1.0 W at a pump power of 4.8 W. A partially reflective mirror is utilized to combine with the output surface of the gain medium to constitute an external Fabry-Perot cavity. It is theoretically and experimentally verified that adjusting the external cavity length to satisfy the commensurate condition can lead to the frequency spacing to be various order harmonics of the mode spacing of the monolithic cavity. The maximum pulse repetition rate of the laser output can be up to 216 GHz and the pulse duration is as short as 330 fs. More importantly, the overall characteristics of the first-order temporal autocorrelation traces obtained by sequentially scanning the external cavity.length display an intriguing phenomenon of temporally fractional revivals, similar to the feature of spatial Talbot revivals.
High-power high-repetition-rate subpicosecond monolithic Yb:KGW laser with self-mode locking
(2013-07-15)
Zhuang, W. Z.
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Chang, M. T.
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Liang, H. C.
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Chen, Y. F.
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電子物理學系
We report on a high-power subpicosecond monolithic self-mode-locked Yb:KGW laser with the pulse repetition rate up to several tens of gigahertz. Experimental results reveal that not only the repetition rate but also the pulse width depend on the length of the laser crystal. Using a coated Yb:KGW crystal with a length of 3.36 mm, mode-locked pulses with pulse duration of 850 fs at the repetition rate of 22.4 GHz have been achieved. With an incident pump power of 10.5 W, an average output power of 3.6 W was achieved which corresponds to the optical conversion efficiency of 34.3%. (C) 2013 Optical Society of America
High-power subpicosecond harmonically mode-locked Yb:YAG laser with pulse repetition rate up to 240 GHz
(2013-01-01)
Chen, Y. F.
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Zhuang, W. Z.
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Liang, H. C.
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WHuang, G.
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Su, K. W.
We report on the operation of a high-power diode-pumped Yb:YAG self-mode-locked microchip laser with a pulse repetition rate of up to 240 GHz. The gain medium is coated to form a cavity mirror and to act as an etalon for achieving harmonic mode locking. A diamond heat spreader is employed to reduce the thermal effects for power scale-up. At an absorbed pump power of 8.3 W, an average output power of 4.6 W is achieved with a pulse duration of 630 fs and a repetition rate of 240 GHz.
High-power terahertz optical pulse generation with a dual-wavelength harmonically mode-locked Yb:YAG laser
(2013-07-01)
Zhuang, W. Z.
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Chang, M. T.
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Su, K. W.
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Huang, K. F.
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Chen, Y. F.
We report on high-power terahertz optical pulse generation with a dual-wavelength harmonically mode-locked Yb:YAG laser. A semiconductor saturable absorber mirror is developed to achieve synchronously mode-locked operation at two spectral bands centered at 1031.67 and 1049.42 nm with a pulse duration of 1.54 ps and a pulse repetition rate of 80.3 GHz. With a diamond heat spreader to improve the heat removal efficiency, the average output power can be up to 1.1 W at an absorbed pump power of 5.18 W. The autocorrelation traces reveal that the mode-locked pulse is modulated with a beat frequency of 4.92 THz and displays a modulation depth to be greater than 80%.
High-pulse-energy, passively Q-switched Yb-doped fiber laser with AlGaInAs quantum wells as a saturable absorber
(2009-08-01)
Huang, J. Y.
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Huang, W. C.
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Zhuang, W. Z.
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Su, K. W.
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Chen, Y. F.
We demonstrate an efficient, high-pulse-energy, passively Q-switched Yb-doped fiber laser with AlGaInAs quantum wells (QWs) as a saturable absorber. The AlGaInAs QW material is designed to provide a large modulation change and a quite-low nonsaturable loss. At an incident pump power of 7.6 W, an average output power of 3.8 W, pulse energy of 300 mu J, pulse repetition rate of 12.5 kHz, and pulse duration of 30 ns was obtained. (C) 2009 Optical Society of America
Hybrid Q-switched Yb-doped fiber laser
(2011-05-09)
Huang, J. Y.
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Zhuang, W. Z.
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Huang, W. C.
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Su, K. W.
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Huang, K. F.
We investigate the performance of a hybrid Q-switched (HQS) fiber laser that is constructed with a low RF-power driven acousto-optic (AO) Q-switch and an AlGaInAs semiconductor saturable absorber. Compared to a pure passively Q-switched (PQS) fiber laser, the ratio of timing jitter to pulse period can be significantly reduced from 2% to 0.3% in the regime of far above threshold. On the other hand, the prelasing effect in a pure actively Q-switched fiber laser can be considerably improved. More importantly, the maximum pulse energy of the HQS fiber laser can be increased approximately 25% in comparison with the result of the PQS fiber laser. At a pump power of 24 W, the highest pulse energy is up to 0.56 mJ with the pulse duration of 50 ns at the repetition rate of 23 kHz. (C) 2011 Optical Society of America
Improvement of stability and efficiency in diode-pumped passively Q-switched intracavity optical parametric oscillator with a monolithic cavity
(2012)
Huang, J. Y.
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Zhuang, W. Z.
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Huang, Y. P.
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Huang, Y. J.
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Su, K. W.
We improve the performance of intracavity optical parametric oscillator (IOPO) pumped by a diode-pumped Q-switched Nd:YVO4/Cr4+:YAG laser. The IOPO cavity is formed independently by a monolithic KTP crystal that the mirrors are directly deposited on top of the nonlinear crystal. We study the performances of this IOPO cavity with different reflectivity of the output coupler at 1.5 mu m (R-s) of 80 and 50%. The average power of 1.5 mu m is up to 3.3 W at the maximum pump power of 16.8Wfor both cases. The diode-to-signal conversion efficiency is up to 20%, which is the highest one for IOPOs to our best knowledge. At the maximum pump power, the pulse energies are 41 mu J with the pulse width of 3 ns at a pulse repetition rate (PRR) of 80 kHz for R-s = 80% and 51 mu J with the pulse width of 1.2 ns at a PRR of 65 kHz for R-s = 50%, respectively. The pulse amplitude fluctuations in standard deviation are 2.6% for R-s = 80% and 4% for R-s = 50%, respectively. [GRAPHICS] (C) 2012 by Astro, Ltd.
Investigating the temporal dynamics of continuously pumped Nd:YVO4 self-Raman lasers: observation of self-mode-locking
(2013-09-01)
Lin, Y. C.
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Lee, C. Y.
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Zhuang, W. Z.
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Su, K. W.
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Chen, Y. F.
We experimentally investigate the temporal dynamics of continuously pumped Nd:YVO4 self-Raman lasers. In the single-transverse-mode operation, it is found that the temporal behavior of the self-Raman laser exhibits a regular pulse train similar to the phenomenon of self-mode-locking. In the multi-transverse-mode operation, the average output power can be scaled up to 1.1 W and the temporal feature displays a complex dynamics that is numerically reconstructed with simultaneous longitudinal and transverse mode-locking.
Millijoule-level Yb-doped photonic crystal fiber laser passively Q-switched with AlGaInAs quantum wells
(2010-12-20)
Zhuang, W. Z.
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Huang, W. C.
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Chiang, P. Y.
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Su, K. W.
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Huang, K. F.
We report on a millijoule-level Yb-doped photonic crystal fiber (PCF) laser passively Q-switched with AlGaInAs quantum wells (QWs). Three types of AlGaInAs devices with different QW numbers are fabricated to investigate the performance. With 50 groups of three AlGaInAs QWs as a saturable absorber (SA), the PCF laser generates an average power of 7.1 W with a pulse repetition rate of 6.5 kHz at a pump power of 16 W, corresponding to the pulse energy of 1.1 mJ. The maximum peak power is up to 110 kW. (C) 2010 Optical Society of America
Passively Q-switched photonic crystal fiber laser and intracavity optical parametric oscillator
(2010-04-26)
Zhuang, W. Z.
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Huang, W. C.
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Huang, Y. P.
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Su, K. W.
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Chen, Y. F.
We report on a passively Q-switched photonic crystal fiber (PCF) laser with Cr(4+): YAG as a saturable absorber. Under a pump power of 14.2 W, the maximum pulse energy is up to 630 mu J with a pulse width of 36 ns at a repetition rate of 5.6 kHz. With an intracavity optical parametric oscillator, the passively Q-switched PCF laser is used to generate the signal wave at 1515 nm. The output pulse energy of the signal wave is found to be 140 mu J with a pulse width as short as 1.0 ns at a repetition rate of 3.3 kHz. The very short pulse width leads to the peak power up to 140 kW. (C) 2010 Optical Society of America
Performance enhancement of sub-nanosecond diode-pumped passively Q-switched Yb:YAG microchip laser with diamond surface cooling
(2012-09-24)
Zhuang, W. Z.
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Chen, Yi-Fan
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Su, K. W.
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Huang, K. F.
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Chen, Y. F.
We experimentally confirm that diamond surface cooling can significantly enhance the output performance of a sub-nanosecond diode-end-pumped passively Q-switched Yb:YAG laser. It is found that the pulse energy obtained with diamond cooling is approximately 1.5 times greater than that obtained without diamond cooling, where a Cr4+:YAG absorber with the initial transmission of 84% is employed. Furthermore, the standard deviation of the pulse amplitude peak-to-peak fluctuation is found to be approximately 3 times lower than that measured without diamond cooling. Under a pump power of 3.9 W, the passively Q-switched Yb: YAG laser can generate a pulse train of 3.3 kHz repetition rate with a pulse energy of 287 mu J and with a pulse width of 650 ps. (C)2012 Optical Society of America
Widely tunable eye-safe laser by a passively Q-switched photonic crystal fiber laser and an external-cavity optical parametric oscillator
(2011-09-01)
Chang, H. L.
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Zhuang, W. Z.
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Huang, W. C.
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Huang, J. Y.
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Huang, K. F.
We report on a widely tunable passively Q-switched photonic crystal fiber (PCF) laser with wavelength tuning range up to 80 nm. The PCF laser utilizes an AlGaInAs quantum well/barrier structure as a saturable absorber and incorporates an external-cavity optical parametric oscillator (OPO) to achieve wavelength conversion. Under a pump power of 13.1 W at 976 nm, the PCF laser generated 1029-nm radiation with maximum output energy of 750 mu J and was incident into an external-cavity OPO. The output energy and peak power of signal wave was found to be 138 mu J and 19 kW, respectively. By tuning the temperature of nonlinear crystal, periodically poled lithium niobate (PPLN), in the OPO, the signal wavelength in eye-safe regime from 1513 to 1593 nm was obtained. (C) 2011 by Astro Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA