| As a strong tool in the basic and applied science, ultra-short pulse plays an important role in several research fields. It has attracted many people’attention, which provide an important method to study the ultrafast processes of physics, biology, chemistry and spectroscopy, etc. Acoustic-optical mode-locked technique is belong to actively mode locking, which is characterized by high stability, high average output power and high repetition. It’s an important way to achieve ultra-short pulse, so developing a highly efficient and stable active acoustic-optical mode-locked laser is essential.This paper carried out in-depth research on the theory of mode-locked technique. Methods of mode-locked are also discussed. The back-reaction of the thermal dynamics to the laser are discussed. A few critical rules concerning the design of resonators used for high-power laser diode end-pumped CW solid-stated lasers were presented in this paper. Following this rules, we find out a series of fold cavity with the characteristic of a wide range of thermal stability, which also can be operated with low threshold pump power, high output power and high efficiency, by using the ABCD matrix method, also considering the thermal effect of the crystal. Matters should be noticed by using of acousto-optic modulator has been discussed and the way to choice Modulation frequency is provided. The thermal induced depolarization loss of Nd:YAG is analyzed, we put forward to insert a tunable diaphragm to inhibit higher order mode laser beams to reduce the influence of the depolarization loss. Output power of12W at a pulse repetition rate of100MHz is obtained in the acousto-optic mode-locking experimental of Nd:YAG. A tunable diaphragm is inserted into the cavity to ensure system running on the fundamental mode, thus improve the stability of average output power. The power fluctuation is less than3%per an hour. |
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