高功率金刚石拉曼激光器热效应数值模拟

Numerical simulation of thermal effects in high-power diamond Raman lasers

金刚石晶体不仅具有极佳的光学性质,同时也拥有极高的热导率和低的热膨胀系数,这使得金刚石激光器成为实现不受热影响高功率激光输出的重要路径。但随着激光功率的进一步提升,金刚石拉曼激光器中仍然存在不可忽视的热效应等问题,这对金刚石激光器性能提升提出了挑战。针对高功率运转情况下金刚石拉曼激光器的热效应进行了理论研究,根据热传导方程并采用有限元分析方法,模拟了金刚石温度、热应力以及热形变分布,分析了泵浦参数、晶体参数对金刚石温度、热应力、热形变的影响。此外,基于石墨片横向导热特性,设计了一种新型的用于金刚石晶体的热沉结构。与传统单一铜片散热方式相比,在泵浦功率800 W、束腰半径40μm条件下,金刚石中心温度下降了10.16 K,下表面平均应力降低了19.857 MPa,端面平均形变量减小了0.055μm。数值模拟结果表明,该方法对缓解金刚石激光的热效应,实现金刚石拉曼激光器输出功率的进一步提升和高光束质量激光输出具有重要指导意义。

Diamond crystals not only have excellent optical properties,but also have extremely high thermal conductivity and low thermal expansion coefficient,which makes diamond laser an important path to achieve high-power laser output without heat.However,with the further increase of laser power,thermal effects that cannot be ignored in diamond Raman lasers(DRLs),which poses a challenge to the performance improvement of diamond lasers.The thermal effect of the DRLs under high power operation was studied theoretically.Based on the thermal conduction equation and finite element analysis method,the temperature,thermal stress and thermal deformation distribution of diamond were simulated,and the effects of pump and crystal parameters on the above factors were analyzed.Moreover,a novel heat sink structure for diamond was designed based on the transverse thermal conductivity characteristics of graphite sheets.Compared with traditional heat dissipation methods of single copper-sheet,under the pump power of 800 W and waist radius of 40μm,the center temperature of the diamond was reduced by 10.16 K,the average stress on the lower surface was reduced by 19.857 MPa,and the average deformation of the end face was reduced by 0.055μm.The numerical simulation results show that this method has important guiding significance for mitigating the thermal effect of diamond laser,further enhancing the output power of DRLs and achieving high beam quality laser output.