| Summary: | 博士 === 國立交通大學 === 電子物理系所 === 98 === The large third-order nonlinearities of Nd:YVO4 and Nd:GdVO4 are employed to realize the compact efficient self-mode-locking in the range of several GHz in solid-state lasers with a simple linear cavity. With a pump power of 2.5 W, the lasers produce greater than 0.7 W with the pulse width in the picosecond region at the operating wavelength of 1064 nm. Furthermore, we also have demonstrated the self-mode-locked Nd:YVO4 laser at 1342 nm. The average output power was up to 1.2 W at an incident pump power of 10.2 W. The pulse width was experimentally found to be less than 12ps.
In order to improve the stability of self-mode-locked lasers, we have demonstrate the control of Nd:YVO4 laser. The experimental results reveal that reducing the number of longitudinal lasing modes can diminish the fluctuation to effectively improve the pulse stability. Considering the spatial hole burning (SHB) effect, an analytical expression is derived to accurately estimate the maximum number of longitudinal lasing for a practical design guideline. Therefore, the stable self-mode-locked laser can induce a novel method to measure the refractive indexes and thermal optical coefficient of certain crystals. The experimental results are in good agreement with the results in texts.
Besides the fundamental mode self-mode-locked lasers, we have reported the self-mode- locked Hermite-Gaussian Nd:YVO4 lasers with an off-axis pumping scheme. With a pump power of 2.2 W, the average output power for 3.5 GHz mode-locked HG modes vary in the range of 350-780 mW for the TEM0,m modes from to . We also use simple astigmatic mode converters (AMC) to convert the mode-locked HG TEM0,m beams in to Laguerre-Gaussian (LG) modes for generating picosecond optical vortex pulses. Furthermore, the modulated pulse trains are observed as there are two adjacent transverse modes coupling. The modulated frequencies can apply to determination of thermal lens in mode-locked lasers.
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