Browsing by Author "Cheng, H. P."

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An energy adjustable linearly polarized passively Q-switched bulk laser with a wedged diffusion-bonded Nd:YAG/Cr4+:YAG crystal
(2015-03-23)
Cho, C. Y.
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Cheng, H. P.
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Chang, Y. C.
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Tang, C. Y.
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Chen, Y. F.
An energy adjustable passively Q-switched laser is demonstrated with a composite Nd:YAG/Cr4+:YAG crystal by applying a wedged interface inside the crystal. The theoretical model of the monolithic laser resonator is explored to show the energy adjustable feature with different initial transmissions of the saturable absorber at the horizontal axis. By adjusting the pump beam location across the Nd: YAG crystal, the output pulse energy can be flexibly changed from 10.9 mu J to 17.6 mu J while maintaining the same output efficiency. The polarization state of the laser output is found to be along with the polarization of the C-mount pump diode. Finally, the behavior of the multi-transverse-mode oscillation is also discussed for eliminating the instability of the pulse train. (C) 2015 Optical Society of America
Analysis of the optimal temperature for the cryogenic monolithic Nd:YAG laser at 946-nm
(2016-01-11)
Cho, C. Y.
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Huang, T. L.
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Cheng, H. P.
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Huang, K. F.
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Chen, Y. F.
The optimal temperature for the cryogenic monolithic Nd:YAG laser at 946-nm is theoretically and experimentally analyzed. It is clear that decreasing temperature can considerably eliminate the thermal population at the lower laser level to enhance the quantum efficiency. However, the narrowing of the absorption bandwidth for the gain medium leads to a reduction of the effective absorption efficiency as the temperature is decreased. Consequently, an optimal temperature for the maximum output power is found to be in the range of approximately 120 K to 140 K. It is experimentally verified that employing a pump source with a narrower emission spectrum linewidth contributes a more efficient output for the cryogenic laser. (C) 2016 Optical Society of America
Efficient high-power continuous-wave lasers at green-lime-yellow wavelengths by using a Nd:YVO4 self-Raman crystal
(2019-02-04)
Chen, Y. F.
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Pan, Y. Y.
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Liu, Y. C.
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Cheng, H. P.
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Tsou, C. H.
Efficient high-power continuous-wave Nd:YVO4 visible lasers at versatile wavelengths of 532 (green). 559 (lime). and 588 nm (yellow) are demonstrated to be achieved by using the identical cavity mirrors and gain medium. A dichroic coating is deposited on one end surface of the gain medium to gather the backward green-yellow emission. The green. lime. and yellow outputs are individually optimized by using different phase-matched lithium triborate (LBO) crystals for second harmonic generation (SHG) of the fundamental field, sum frequency generation (SFG) of the fundamental and the stimulated Raman fields. and SHG of the stimulated Raman field, respectively. At a pump power of 31.6 W, the output powers at 532, 559, and 588 nm can be up to 6.8. 5.4. and 3.1 W. The high efficient and compact Nd:YVO4 lasers at green-lime-yellow wavelengths can be potentially beneficial to future applications in retinal photocoagulation. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Efficient high-power dual-wavelength lime-green Nd:YVO4 lasers
(2019-03-15)
Chen, Y. F.
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Liu, Y. C.
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Pan, Y. Y.
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Gu, D. Y.
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Cheng, H. P.
An efficient high-power dual-wavelength lime-green Nd:YVO4 self-Raman laser is inventively developed by using two different lithium triborate (LBO) crystals. The first and second LBO crystals are employed to generate the 559 nm lime and 532 nm green lasers, respectively. The temperature of the first LBO crystal is fixed at the optimal phase matching, whereas the temperature of the second LBO crystal is tuned to flexibly control the relative strengths between the 532 and 559 nm waves. When the temperature of the second LBO crystal is set for the maximal total output power, the 532 and 559 nm output powers, respectively, are 7.1 and 2.9 W at a pump power of 31.6 W, corresponding to a conversion efficiency of 31.6%. When the temperature is controlled for the balanced output, the 532 and 559 nm powers, respectively, are 4.3 and 4.2 W at a pump power of 31.6 W, corresponding to a conversion efficiency of 26.9%. (C) 2019 Optical Society of America
Generation of orthogonally polarized self-mode-locked Nd:YAG lasers with tunable beat frequencies from the thermally induced birefringence
(2016-04-15)
Sung, C. L.
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Cheng, H. P.
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Lee, C. Y.
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Cho, C. Y.
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Liang, H. C.
The simultaneous self-mode-locking of two orthogonally polarized states in a Nd:YAG laser is demonstrated by using a short linear cavity. A total output power of 3.8 W can be obtained at an incident pump power of 8.2 W. The beat frequency Delta f(c) between two orthogonally polarized mode-locked components is observed and measured precisely. It is found that the beat frequency increases linearly with an increase in the absorbed pump power. The origin of the beat frequency can be utterly manifested by considering the thermally induced birefringence in the Nd: YAG crystal. The present result offers a promising approach to generate orthogonally polarized mode-locked lasers with tunable beat frequency. (C) 2016 Optical Society of America
High-power dual-color yellow-green solid-state self-Raman laser
(2019-07-01)
Chen, Y. F.
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Liu, Y. C.
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Gu, D. Y.
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Pan, Y. Y.
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Cheng, H. P.
A compact dual-color solid-state self-Raman laser with adjustable power-ratio between yellow and green emissions is demonstrated by using a specially coated Nd:YVO4 crystal. The Nd:YVO4 crystal is coated to replace a cavity mirror for minimizing the cavity losses and to reflect the backward green-yellow emission for avoiding the absorption. Two different lithium triborate (LBO) crystals are employed to produce the SHG of the 1176 nm Stokes field and the 1064 nm fundamental wave for the yellow and green emissions. The temperature of the LBO crystal for yellow generation is controlled at the optimal phase-matching to maximize the efficiency. The temperature of the LBO crystal for green generation is precisely varied to adjust the power-ratio between the yellow and green emissions. At the temperature for balanced emissions, both of 532 nm and 588 nm output powers can simultaneously achieve 4.0 W at a pump power of 31.6 W.
Monolithic dual-polarization self-mode-locked Nd: YAG 946-nm lasers: controlling beat frequency and observation of temporal chaos
(2016-10-17)
Cheng, H. P.
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Huang, T. L.
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Lee, C. Y.
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Sung, C. L.
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Cho, C. Y.
The self-mode-locked (SML) operation at 946 nm can be achieved with a monolithic Nd: YAG crystal when the pump power is above the threshold of the multiple-longitudinal-mode generation. The SML output is further found to include two orthogonal polarization components with a beat frequency coming from the birefringence effect in the laser crystal. The beat frequency can be widely adjusted in the range of 5-220 MHz by controlling the cooling temperature. The present experiment also confirms the theoretical prediction that the two-mode operation generally exhibits the chaotic dynamics when the frequency difference is sufficiently close to the relaxation frequency. (C) 2016 Optical Society of America
Orthogonally polarized self-mode-locked Nd:YAG laser with tunable beat frequencies
(2017-01-01)
Lee, C. Y.
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Sung, C. L.
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Cho, C. Y.
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Cheng, H. P.
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Chen, Y. F.
An orthogonally polarized self-mode-locked Nd: YAG laser is demonstrated in a short linear cavity. Under an incident pump power of 8.2 W, the average output power can be measured to be 3.8 W. The beat frequency.fc between two orthogonally polarized mode-locked components is observed and increases linearly with an increase in the incident pump power. The origin of the beat frequency is utterly confirmed to be caused by the thermal-stress-induced birefringence in the Nd: YAG crystal and is theoretically simulated. The present result provides a promising method to achieve orthogonally polarized mode-locked lasers with tunable beat frequency.
Synchronized self-mode-locked 1061-nm and 1064-nm monolithic Nd:YAG laser at cryogenic temperatures with two orthogonally polarized emissions: generation of 670 GHz beating
(2016-09-19)
Huang, T. L.
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Sung, C. L.
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Cheng, H. P.
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Cho, C. Y.
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Liang, H. C.
A dual-wavelength self-mode-locked monolithic Nd: YAG laser at 1061 and 1064 nm is realized at cryogenic temperatures. At an incident pump power of 5.5 W, the total output power can reach 2.5 W and the mode-locked pulse width is 29 ps at a pulse repetition rate of 7.75 GHz. The synchronization of the dual-wavelength emissions leads to a beat frequency of 670 GHz in the individual mode-locked pulse. It is further discovered that the laser output consists of two orthogonally polarized components with a central frequency difference of 127 MHz. The central frequency difference between two orthogonal polarizations mainly arises from the external mechanical stress introduced by the copper holder for the laser crystal. (C) 2016 Optical Society of America