Browsing by Author "Tsou, C. H."

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A high-power harmonically self- mode-locked Nd:YVO4 1.34-mu m laser with repetition rate up to 32.1 GHz
(2014-04-01)
Wu, T. W.
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Tsou, C. H.
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Tang, C. Y.
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Liang, H. C.
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Chen, Y. F.
We develop a practical method to achieve harmonically self-mode-locked operation in a Nd:YVO4 1.34-mu m laser for the generation of high-repetition-rate pulse trains. We exploit a gain medium with partial-reflection coating at the lasing wavelength to introduce effective mode selection. We numerically demonstrate that the coated gain medium can effectively modify the mode spacing of the laser cavity to be the harmonics of the free spectral range of the gain medium when the optical cavity length is adjusted to be commensurate with the optical length of the gain medium. We further employ a coated Nd: YVO4 crystal to realize harmonically mode-locked operation with a highest repetition rate of up to 32.1 GHz. At a pump power of 11.5 W, the average output power of 2.3 W is generated with a pulse duration as short as 5.7 ps. The locking range for the cavity length is also experimentally explored.
Compact efficient high-power triple-color Nd:YVO4 yellow-lime-green self-Raman lasers
(2020-03-01)
Liu, Y. C.
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Chen, C. M.
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Hsiao, J. Q.
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Pan, Y. Y.
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Tsou, C. H.
A novel, to the best of our knowledge, approach is developed to realize a high-power compact efficient yellow-lime-green triple-color Nd : YVO4 self-Raman laser. The 588 nm yellow laser, the 559 nm lime laser, and the 532 nm green laser are converted from the 1064 nm fundamental wave and the 1176 nm Stokes Raman field. The simultaneous three-color operation is accomplished with three stages to step-by-step generate the 588 nm, 559 nm, and 532 nm lasers by using three different lithium triborate (LBO) crystals. By tuning the temperature of each individual LBO crystal, the 588 nm, 559 nm, and 532 nm output powers can be nearly the same and concurrently up to 2.4W at the incident pump power of 30 W, corresponding to a conversion efficiency of 24% for the total output power. (C) 2020 Optical Society of America
Criterion for optimizing high-power acousto-optically Q-switched self-Raman yellow lasers with repetition rates up to 500 kHz
(2020-04-01)
Chen, Y. F.
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Chen, K. Y.
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Liu, Y. C.
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Chen, C. M.
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Tsou, C. H.
The criterion for optimizing the high-power acousto-optically Q-switched self-Raman yellow laser is originally explored for the repetition rate within 100-500 kHz. The minimum allowed value for the gate-open time is experimentally verified to be determined by the pulse buildup time. By using the minimum allowed gate-open time, the highest conversion efficiency can be achieved to raise the output power by approximately 20% in comparison with the conventional results. At a repetition rate of 200 kHz, the maximum output power at 588 nm can be up to 8.8 W at an incident pump power of 26 W. Furthermore, a practical formula is developed to accurately calculate the threshold pump power as a function of the gate-open time for a given repetition rate. (C) 2020 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
Experimental and theoretical explorations for optimizing high-power geometric modes in diode-pumped solid-state lasers
(2018-07-01)
Hsieh, Y. H.
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Lai, Y. H.
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Tsou, C. H.
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Liang, H. C.
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Huang, K. F.
The variation of transverse patterns on the cavity length is experimentally explored by using an off-axis pumped Nd:YVO4 laser to identify the range of the length for generating geometric modes (GMs). Using the inhomogeneous Helmholtz equation, it is theoretically confirmed that the stable range of the cavity length for generating GMs can be significantly enlarged by decreasing the output reflectance. Furthermore, experimental results reveal that the cavity length for scaling up the output power of GMs must be shortened due to the thermal lensing effect in the gain medium. Considering the balance between the output efficiency and the stable range of the cavity length, the optimal output reflectance is verified to be approximately 80%. With the optimal output reflectance, the average output power of GMs can be up to 6.33 W at a pump power of 12 W.
Exploiting a monolithic passively Q-switched Nd:YAG laser to mimic a single neuron cell under periodic stimulation
(2020-07-15)
Chen, Y. F.
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Lee, C. C.
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Hsiao, J. Q.
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Huang, H. Y.
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Tsou, C. H.
A monolithic passively Q-switched Nd:YAG laser under periodic pulse pumping is originally exploited to emulate the response of a single neuron cell stimulated by periodic pulse inputs. Experimental results reveal that the output characteristics of the monolithic passively Q-switched laser can analogously manifest not only the firing patterns but also the frequency-locked plateaus of the single neuron cell. Moreover, the sine circle map is innovatively used to generate the output pulse sequences that can exactly correspond to experimental firing patterns. The present exploration indicates that a monolithic passively Q-switched solid-state laser is highly feasible to be developed as a compact artificial neuron cell. (C) 2020 Optical Society of America
Exploring optical properties of Nd-doped vanadates with intracavity self-mode locking
(2013)
Liang, H. C.
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Tung, J. C.
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Tsou, C. H.
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Su, K. W.
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Chen, Y. F.
We employ an intracavity self-mode-locked laser to systematically measure the group refractive indices and the thermo-optic coefficients for Nd:GdVO4, Nd:YVO4 and Nd:LuVO4 crystals at 1064 nm. We further make a detailed comparison between the present results and those currently reported in the literature. All the experimental results can be found to be fairly consistent with the recent reported data
Exploring the influence of high order transverse modes on the temporal dynamics in an optically pumped mode-locked semiconductor disk laser
(2015-06-15)
Tsou, C. H.
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Liang, H. C.
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Wen, C. P.
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Su, K. W.
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Huang, K. F.
We quantitatively investigate the influence of high-order transverse modes on the self-mode locking (SML) in an optically pumped semiconductor laser (OPSL) with a nearly hemispherical cavity. A physical aperture is inserted into the cavity to manipulate the excitation of high-order transverse modes. Experimental measurements reveal that the laser is operated in a well-behaved SML state with the existence of the TEM0,0 mode and the first high-order transverse mode. While more high-order transverse modes are excited, it is found that the pulse train is modulated by more beating frequencies of transverse modes. The temporal behavior becomes the random dynamics when too many high-order transverse modes are excited. We observe that the temporal trace exhibits an intermittent mode-locked state in the absence of high-order transverse modes. (C) 2015 Optical Society of America
Flexible generation of optical beams with quasicrystalline structures via astigmatism induced by a tilted lens
(2012-12-01)
Tung, J. C.
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Liang, H. C.
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Tsou, C. H.
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Su, K. W.
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Chen, Y. F.
We theoretically show that a family of optical beams with vortex-lattice structures can be reliably generated by tilting the focal lens to introduce the relative phases between the interfering beams. We also experimentally generate the quasicrystal beams to confirm the theoretical analysis. With the analytical wave functions and experimental patterns, a variety of vortex-lattice structures are manifested.
Formation and recurrence of quasicrystalline patterns from quantum dynamics of suddenly released matter waves: Analogous manifestation of optical waves
(2012-07-01)
Liang, H. C.
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Tung, J. C.
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Wu, T. W.
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Tsou, C. H.
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Lin, Y. C.
We analytically and numerically verify that two-dimensional (2D) quasicrystalline matter waves can be formed from the free-time evolution of multiple Gaussian waves regularly distributed on a circular ring. We also demonstrate that an interesting recurrence phenomenon can be manifested by adding an extra Gaussian wave on the center of multiple Gaussian waves uniformly distributed on a ring. We finally employ an optical experiment for the coherent light passing through the mask to analogously illustrate the formation of 2D quasicrystalline patterns and the associated recurrence. Copyright (C) EPLA, 2012
Generation of pseudonondiffracting optical beams with superlattice structures
(2013-10-07)
Tsou, C. H.
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Wu, T. W.
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Tung, J. C.
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Liang, H. C.
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Tuan, P. H.
We demonstrate an approach to generate a class of pseudonondiffracting optical beams with the transverse shapes related to the superlattice structures. For constructing the superlattice waves, we consider a coherent superposition of two identical lattice waves with a specific relative angle in the azimuthal direction. We theoretically derive the general conditions of the relative angles for superlattice waves. In the experiment, a mask with multiple apertures which fulfill the conditions for superlattice structures is utilized to generate the pseudonondiffracting superlattice beams. With the analytical wave functions and experimental patterns, the pseudonondiffracting optical beams with a variety of structures can be generated systematically. (C) 2013 Optical Society of America
High-peak-power optically-pumped AlGaInAs eye-safe laser with a silicon wafer as an output coupler: comparison between the stack cavity and the separate cavity
(2015-11-30)
Wen, C. P.
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Tuan, P. H.
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Liang, H. C.
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Tsou, C. H.
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Su, K. W.
An intrinsic silicon wafer is exploited as an output coupler to develop a high-peak-power optically-pumped AlGaInAs laser at 1.52 mu m. The gain chip is sandwiched with the diamond heat spreader and the silicon wafer to a stack cavity. It is experimentally confirmed that not only the output stability but also the conversion efficiency are considerably enhanced in comparison with the separate cavity in which the silicon wafer is separated from other components. The average output power obtained with the stack cavity was 2.02 W under 11.5 W average pump power, corresponding to an overall optical-to-optical efficiency of 17.5%; the slope efficiency was 18.6%. The laser operated at 100 kHz repetition rate and the pulse peak power was 0.4 kW. (c) 2015 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.
;
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.
Observation of reflection feedback induced the formation of bright-dark pulse pairs in an optically pumped semiconductor laser
(2016-06-13)
Tsou, C. H.
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Liang, H. C.
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Huang, K. F.
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Chen, Y. F.
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電子物理學系
It is experimentally demonstrated that the tiny reflection feedback can lead the optically pumped semiconductor laser (OPSL) to be operated in a self-mod-locked state with a pulse train of bright-dark pulse pairs. A theoretical model based on the multiple reflections in a phase-locked multi-longitudinal-mode laser is developed to confirm the formation of bright-dark pulse pairs. The present finding can offer an important insight into the temporal dynamics in mode-locked OPSLs. (C)2016 Optical Society of America
Observation of self-mode-locking assisted by high-order transverse modes in optically pumped semiconductor lasers
(2014-10-01)
Liang, H. C.
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Tsou, C. H.
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Lee, Y. C.
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Huang, K. F.
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Chen, Y. F.
The criterion for achieving the self-mode-locking (SML) in an optically pumped semiconductor laser (OPSL) with a linear cavity is systematically explored. Experimental results reveal that the occurrence of SML can be assisted by the existence of high-order transverse modes. Numerical analysis is performed to confirm that the critical pump power for obtaining the SML operation agrees very well with the pump threshold for exciting TEM1,0 mode. The present finding offers an important insight into laser physics and a useful indication for obtaining the SML operation in OPSLs.
Total self-mode locking of multi-pass geometric modes in diode-pumped Nd:YVO4 lasers
(2013-10-01)
Liang, H. C.
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Wu, T. W.
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Tung, J. C.
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Tsou, C. H.
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Huang, K. F.
We report for the first time on simultaneously longitudinal and transverse self-mode locking in a diode-pumped Nd:YVO4 laser to achieve a pulse train traveling along the zigzag multi-pass trajectories in the degenerate cavity. At a pump power of 2.5 W, the average output powers in the mode-locked operation are 490 mW and 520 mW for the M-mode and Z-mode, respectively. The pulse widths are measured to be approximately 22.2 and 21.1 ps for the M-mode and Z-mode, respectively.
Various Phenomena of Self-mode-locked Operation in Optically Pumped Semiconductor Lasers
(2017-01-01)
Tsou, C. H.
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Liang, H. C.
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Huang, K. F.
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Chen, Y. F.
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電子物理學系
This work presents several optical experiments to investigate the phenomenon of self-mode locking (SML) in optically pumped semiconductor lasers (OPSLs). First of all, we systematically explore the influence of high-order transverse modes on the SML in an OPSL with a linear cavity. Experimental results reveal that the occurrence of SML can be assisted by the existence of the first high-order transverse mode, and the laser is operated in a well-behaved SML state with the existence of the TEM0,0 mode and the first high-order transverse mode. While more high-order transverse modes are excited, it is found that the pulse train is modulated by more beating frequencies of transverse modes. The temporal behavior becomes the random dynamics when too many high-order transverse modes are excited. We observe that the temporal trace exhibits an intermittent mode-locked state in the absence of high-order transverse modes. In addition to typical mode-locked pulses, we originally observe an intriguing phenomenon of SML in an OPSL related to the formation of bright-dark pulse pairs. We experimentally demonstrated that under the influence of the tiny reflection feedback, the phase locking between lasing longitudinal modes can be assisted to form bright-dark pulse pairs in the scale of round-trip time. A theoretical model based on the multiple reflections in a phase-locked multi-longitudinal-mode laser is developed to confirm the formation of bright-dark pulse pairs.