增益导引折射率反导引大模场光纤激光器特性分析

Characteristic analysis of gain guided index antiguided large-mode-area fiber lasers

为了研究增益导引折射率反导引光纤激光器的功率分布及输出特性,根据此类光纤的结构原理和特点,建立了端面抽运的增益导引折射率反导引光纤激光器的基模光速率方程,推导了避免激发高阶模的增益阈值判决条件,并运用弦切法和Runge-Kutta法数值求解了该速率方程,分析了光纤长度、腔镜反射率等参量对基模输出功率的影响。采用芯径为100μm、折射率差为-0.00094、掺杂Yb^(3+)浓度为5×10^(26)/m^3的增益导引折射率反导引光纤构建激光器时,要使得整段光纤不激发高阶模,需使光纤长为3cm、两腔镜反射率为0.98和0.3,当抽运功率为30W时,可获得2.42W的大模场单模输出,斜率效率约为8.1%。结果表明,优化设计腔镜反射率和光纤长度后,采用较短的大模场高掺杂增益导引折射率反导引光纤可获得一定效率的基模输出。

In order to study the power distribution and output characteristics of gain guided index antiguided （GG-IAG） fiber lasers, rate equations of basic model light of double-clad GG-IAG fiber lasers with end-pumping were established, based on the principle and structure characteristics of GG-IAG fibers. After solving the rate equations with tangential method and Runge- Kutta method, power distribution and output characteristics of basic model light were gained. The results show that parameters of fiber and laser cavity, such as fiber length, output lens reflectivity, have significant influence on gain distribution and output power of basic model light. When using a GG-IAG fiber with a radius of 100μm, index step -0. 00094 and concentration of ions 5×10^26/m^3 to construct a GG-IAG fiber laser, fiber length needs to be 3cm and output lens refleetivity is 0. 98 and 0. 3 respectively, in order to restrain LP, model, and while inputing a 30W pmnp-light, 2.42W single-mode laser with large-mode- area can be obtained. The analysis shows that by optimally designing cavity mirror reflectivity and fiber length, fundamental mode output with certain efficiency can be obtained in a short length large-mode-area highly doped GG-IAG fiber.