Upadhyaya B N, Chakravarty Usha, Kuruvilla A, Thyagarajan K, Shenoy M R, Oak S M
Opt Express. 2007 Sep 3;15(18):11576-88. doi: 10.1364/oe.15.011576.
The output pulse characteristics of Q-switched Yb-doped fiber lasers have been investigated experimentally. It has been observed that for any typical modulation frequency, the pump power and the modulator OFF-time govern the shape of the output Q-switched pulse. At a fixed modulation frequency, with a fine adjustment of acousto-optic modulation window ON-time, pump power and cavity mirror position, it was possible to obtain modulation free single-peak pulse, multi-peak pulse, mode-locked resembling pulse and multi-pulse structured pulse shapes in a Q-switched fiber laser output. These observations have been analyzed and explained. Our investigations show that multi-peak pulse output is due to onset of nonlinear phenomena like SBS and SRS. Similarly, we have found that the mode-locked resembling periodically modulated output pulse shape is due to mode beating between the zeroeth order and the first order diffracted beams of the intra-cavity acousto-optic Q-switch.
对调Q掺镱光纤激光器的输出脉冲特性进行了实验研究。据观察，对于任何典型的调制频率，泵浦功率和调制器关断时间决定了调Q输出脉冲的形状。在固定的调制频率下，通过精细调整声光调制窗口开启时间、泵浦功率和腔镜位置，可以在调Q光纤激光器输出中获得无调制的单峰脉冲、多峰脉冲、类锁模脉冲和多脉冲结构脉冲形状。对这些观察结果进行了分析和解释。我们的研究表明，多峰脉冲输出是由于受激布里渊散射（SBS）和受激拉曼散射（SRS）等非线性现象的出现。同样，我们发现类锁模的周期性调制输出脉冲形状是由于腔内声光Q开关的零阶和一阶衍射光束之间的模式拍频。
