Browsing by Author "Cho, Chun Yu"

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Compact coupling scheme to achieve the synchronously dual self-mode-locked operation with a 35.2 THz optical beating
(2017-06-01)
Cheng, Hao Ping
;
Huang, Tzu Lin
;
Sung, Cheng Lin
;
Cho, Chun Yu
;
Liang, Hsing Chih
A synchronously dual self-mode-locked (SML) operation at 946 and 1064 nm is experimentally accomplished by using a compact coupling scheme to obtain the optical beating frequency up to 35.2 THz. The SML emissions at 946 and 1064 nm are established by a monolithic Nd:YAG cavity and a Nd: YVO4 crystal in a flat-flat cavity, respectively. Two gain media are butt adjoined to be longitudinally pumped by a single laser diode. The monolithic Nd: YAG crystal is used not only as the 946 nm laser cavity, but also as the output coupler of the Nd: YVO4 1064 nm laser. More importantly, the output surface of the monolithic Nd: YAG laser is coated to generate the optical feedback for the synchronization of the dual SML operation. At a pump power of 10.7 W, the output powers at 1064 and 946 nm can simultaneously reach 1.5 W by controlling the focal position of the pump waist. (C) 2017 Optical Society of America
Energy scale-up and mode-quality enhancement of the LED-pumped Nd:YAG Q-switched laser achieving a millijoule green pulse
(2019-07-01)
Cho, Chun Yu
;
Pu, Chi Chih
;
Chen, Yung Fu
;
Su, Kuan Wei
;
電子物理學系
An efficient LED pumping module is explored for the demonstration of energy scaling of passively Q-switched output to millijoule high-pulse-energy level. For the free-running operation at fundamental wavelength, the highest optical conversion efficiency of 23.7% is reached. By using a Cr4+:YAG crystal as the saturable absorber, the passively Q-switched output energy is up to 14.5 mJ in a compact setup. The laser resonator is further optimized to shorten the output pulse width and to obtain better mode quality. The pulse width of the Q-switched emission is as short as 25 ns, and the peak power is up to 0.7 MW. With such a highly efficient configuration, the extracavity second-harmonic generation at 532 nm can be achieved with 4.5 mJ pulse energy. (C) 2019 Optical Society of America
Exploring the DBR superlattice effect on the thermal performance of a VECSEL with the finite element method
(2019-01-15)
Huo, Yongjun
;
Cho, Chun Yu
;
Huang, Kai Feng
;
Chen, Yung Fu
;
Lee, Chin C.
The design criterion of thermal conductivity for the GaAs/AlAs distributed Bragg reflector (DBR) superlattice structure was thoroughly investigated to precisely analyze the thermal behaviors of the optically pumped vertically external cavity surface-emitting laser (VECSEL). A finite element model with detailed configuration of a VECSEL gain chip was constructed to fulfill the analysis. A 1060 nm VECSEL with different pump conditions was further demonstrated to verify the finite element analysis. At the VECSEL thermal rollover point, the analysis results show that the model with the superlattice property predicts more precise temperature values than that using a bulk composite property. It reveals that the accurate determination of the thermal conductivity of the DBR superlattice is significantly important for the VECSEL thermal analysis. (C) 2019 Optical Society of America
Exploring the self-mode locking of the 2 mu m Tm:YAG laser with suppression of the self-pulsing dynamic
(2017-12-15)
Cho, Chun Yu
;
Chen, Yung Fu
;
Zhang, Ge
;
Chen, Wei Dong
;
Liang, Hsing Chih
A continuous-wave (cw) self-mode-locked Tm:YAG laser at 2015 nm is successfully demonstrated by suppressing the self-pulsing behavior. By using rate equations to simulate the laser temporal dynamic, the theoretical analysis indicates that the reabsorption-induced self-pulsing for the Tm: YAG laser can be suppressed with sufficient pump power. It is experimentally confirmed that at absorbed powers higher than 6 W, the self-pulsing can be eliminated and a cw self-mode-locked pulse is generated instead of the Q-switched mode locking. At an absorbed power of 6.8 W, the output power of the self-mode-locked Tm: YAG laser reaches 1.22 W with corresponding pulse duration of 3 ps and a repetition rate of 3.376 GHz. (C) 2017 Optical Society of America
LED-side-pumped Nd:YAG laser with > 20% optical efficiency and the demonstration of an efficient passively Q-switched LED-pumped solid-state laser
(2017-06-15)
Cho, Chun Yu
;
Pu, Chi Chih
;
Su, Kuan Wei
;
Chen, Yung Fu
;
電子物理學系
A LED-array-pumped Nd:YAG laser with optical conversion efficiency up to 20.2% is demonstrated by direct side-pumping without a coupling lens. The 810-nm LED array with a full-width-half-maximum of 30 nm and an area fill factor of 50% is designed to attain high spectral absorption efficiency with a pump density of 151.8 W/cm(2). Furthermore, higher than 45% overall coupling efficiency is achieved by placing the LED array as close as possible to the side of the gain medium for overcoming the large pumped divergence. More importantly, by using the efficient pump scheme, the demonstration of a passively Q-switched LED-pumped laser is successfully realized with a pulsed energy of 1.42 mJ. (C) 2017 Optical Society of America