光纤激光经过模清洁器后的强度噪声分析  

Intensity noise analysis of a fibre laser after passing through an optical mode cleaner

作　　者：邰朝阳 侯飞雁[1] 王盟盟[1,2] 权润爱[1] 刘涛[1] 张首刚[1] 董瑞芳[1] 

机构地区：[1]中国科学院国家授时中心,中国科学院时间频率基准重点实验室,西安710600 [2]中国科学院大学,北京100049

出　　处：《物理学报》2014年第19期107-112,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:Y133ZK1101;11174282;91336108);中科院"西部之光"计划重点项目(批准号:中科院人教字(2011)180号);科技创新"交叉与合作团队"项目(批准号:中科院人教字(2012)119号);中组部"青年拔尖人才支持计划"项目(批准号:组厅字[2013]33号)资助的课题~~

摘　　要：对1560 nm单频光纤激光光源通过一个光学模清洁器后的强度噪声进行了分析研究.实验观察到模清洁器虽然对于激光的高频强度噪声有明显的抑制作用,但强度噪声特性随频率呈一定周期变化,且在低频处模清洁器对强度噪声有放大作用.本文认为这是由于模清洁器具有类似于光纤延迟线的时延效应,将激光源的部分相位噪声转化为强度噪声.通过理论分析,由相位噪声转化的相对强度噪声幅度与激光相干时间、模清洁器的平均延时参数以及分析频率相关.分析结果与实验测量结果符合良好.此外,通过在光路中加入声光调制器进行反馈调制,激光的线宽从26 kHz压窄至16 kHz,模清洁器的锁定质量明显提高,经过模清洁器后的激光强度噪声有所减小,与理论相符.该结果进一步证实了由相位噪声转化而来的强度噪声与模清洁器的锁定质量无直接关系.通过该研究,完善了光学模清洁器对激光的噪声抑制模型.Theintensitynoiseina1560nmsinglefrequencyfiberlaserafterpassingthroughanopticalmodecleanerisanalyzed both theoretically and experimentally. Experimental measurement shows that in addition to the evident suppression of intensity noise by the mode cleaner, there exist induced observable periodic fluctuations in the analyzing frequency range of 2 to 12 MHz, as well as the amplification of the intensity noise at low frequencies. The above results cannot be explained by the present mode cleaner model for noise suppression. In this paper, we propose a new theoretical model, in which the mode cleaner is considered equivalent to a delay line and through it the phase-noise of the fiber laser is partially converted to the intensity noise. The phase-induced relative intensity noise（RIN） amplitude is jointly determined by the laser linewidth, the mode cleaner linewidth, and the analyzing frequency. The theoretical analysis shows a very good agreement with the experimental results. The noise suppression effect of the acoustic optical modulator is further analyzed by inserting it into the setup and providing a frequency modulation for it. We have observed an evident improvement of the mode cleaner locking, while the bandwidth of the laser is slightly suppressed from 26 to 16 kHz,and the degradation of the measured intensity noise after the mode cleaner is also moderate. The theoretical analysis according to our proposed model fits well with this result. This result further confirms that the phase-induced intensity noise has no direct connection to the mode cleaner locking quality. Through the above analysis, a complete theoretical mode for analyzing the noise suppression by a mode cleaner is built.

关 键 词：模清洁器 相位噪声转化 强度噪声 线宽 

分 类 号：O431.2[机械工程—光学工程]