摘要
光拍频自1955年发现以来,尤其是1960年激光出现以来得到迅速的发展。但迄今为止,关于光拍频技术的研究主要集中在利用单纵模激光器所产生的单纵模脉冲上,而对于锁模激光器输出的ps锁模脉冲的研究还没有引起人们足够的重视。
本文主要对主被动锁模激光器输出的ps锁模脉冲拍频进行实验研究。在理论研究方面,分析了光拍频的基本原理,以及对拍频实验所用锁模光源的产生进行了讨论。同时对锁模技术的关键器件及其锁模机理进行了分析。对利用锁模脉冲拍频进行了理论计算,同时对拍频实验中关键器件声光移频器及其原理进行了讨论。
在实验研究方面,对主被动锁模激光器及锁模脉冲的拍频进行了实验研究。在主被动锁模激光器实验方面,首先,研究了Nd4+:YAG激光器的自由振荡,然后加声光锁模器实现主动锁模激光器运转,研究其脉冲激光输出特性,最后加Cr4+:YAG晶体实现被动锁模激光器运转,研究其脉冲激光输出特性。进而利用主动锁模脉冲,及声光移频器实现了不同频移下的拍频。最终实现了ps级主动锁模脉冲在声光移频器最佳工作频率80MHz条件下的拍频,此状态下拍频结果最为理想,误差最小。
Optical beat frequency, which has been found since 1955, especially since the emergence of the laser in 1960 has been developed rapidly. So far, mostly, the research of optical beat frequency has concentrated on the use of single-frequency pulse generated by single longitudinal mode laser. However, the study on the mode-locked pulse generated by ps mode-locked laser did not arouse enough attention.
This paper mainly concentrates on the Optical beat frequency of ps mode-locked pulse generated by avtively-passively mode-locked laser.
In theory, firstly this paper introduced the basic principle of beat frequency, and then, discussed the generation of light source for beat frequency. In the meantime, the key mode-locking device and its mode-locking mechanism was analyzed. Also, the theoretical calculation of beat frequency for mode-locked pulse was worked. Then, the paper discussed the the acousto-optic frequency shifter that is the key device and its working principle.
In experimental research, we carried out the experiments of actively- passively mode-locked laser and beat frequency for the mode-locked pulse. For the mode-locked lasers. First of all, we studyed the Nd4 +: YAG laser free vibration. And then added acousto-optic cell to achieve actively mode-locked operation, in the meantime, the laser output characteristics was studied. And finally we added Cr4 +: YAG crystal to achieve actively-passively mode-locked laser operation, and the characteristics of laser output is also studied. We achieved the beat frequencies under different frequency shift generated by acousto-optic frequency shifter. At last , when acousto-optic frequency shifter was under 80MHz that was its best working frequency, we achieved the best result of beat frequency. In this condition, the error of beat frequency for mode-locked pulse was the smallest.
引文
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