利用20 W连续波掺Yb光纤激光器泵浦一段520 m长的高非线性光纤，在无谐振腔的简单结构中实现了四级级联拉曼激光输出，各阶斯托克斯波长分别为1121 nm、1178 nm、1247 nm和1319 nm，总的频移量为53 THz，最大输出功率达到3.2 W。实验中描述了斯托克斯光的转换过程，并进行了相应分析。无谐振腔结构中多级拉曼激光的产生被认为是基于瑞利散射效应的随机分布反馈，并且证实通过高非线性光纤作为拉曼增益介质可以缩短无谐振腔拉曼光纤激光器所需的光纤长度。
By using a 520-m-long highly nonlinear fiber (HNLF) pumped by a 20 W CW Yb-doped fiber laser, four Raman Stokes emissions are demonstrated in a simple cavity-free configuration. The Stokes wavelengths are 1121 nm, 1178 nm, 1247 nm and 1319 nm respectively with a total frequency shift of 53 THz, and the maximum output power is 3.2 W. The evolution of the multiple Raman Stokes emission is presented and analyzed. The generation of the multiple Stokes from the cavity-free configuration is attributed to the random distributed feedback based on Rayleigh scattering. It is also demonstrated that the fiber length of the cavity-free Raman fiber laser can be largely shortened by using a HNLF as the Raman gain medium.
%K 拉曼光纤激光器；多阶斯托克斯辐射；无谐振腔激光器；高非线性光纤