-
激光介质热效应引起的谐振腔模场结构变化成为高功率涡旋激光器的一个关键问题。建立了环形光泵浦薄片激光晶体的温度场及热形变计算模型，将热效应像差作为谐振腔衍射积分方程的微扰，研究热效应对激光器模场结构的影响规律。研究了Nd:YAG、Nd:YLF和Nd:YVO4薄片涡旋激光器的模场结构随泵浦功率、晶体吸收系数、晶体厚度的变化规律。研究结果表明，热效应使涡旋激光器模谱产生径向展宽，模式纯净度下降。泵浦功率越大，高阶径向模式占比越大，模场结构越复杂。泵浦功率升高时，Nd:YVO4激光器的模谱展宽最大，Nd:YAG激光器的模谱展宽最小。晶体吸收系数越大，模谱展宽越严重；激光晶体厚度减小时，模谱展宽呈增宽趋势。Optical vortex beam has wide application prospect in areas such as optical communication, lidar detection and optical trapping. To increase the operating distance, a high-power vortex laser source is necessary in these applications. However, the purity of the output vortex beam decreases as the pump power increasing due to the thermal effect of the laser medium. Therefore, modal field degeneration induced by thermal effect of laser medium has become a critical issue in high-power vortex solid-state laser. To investigate this modal field degeneration, the heat transfer and thermal deformation model of an annular beam end pumped thin-disk vortex laser (Fig.(a)) is established. The phase difference of the thermal effect is calculated based on this model. Then, the quadratic term is separated from the phase difference. The non-quadratic term, as a small perturbation, is substituted into the diffraction integral equation of the laser cavity. The modal field structure is obtained by using the perturbation method. The variations of the modal structure with pump power, absorption coefficient and crystal thickness are investigated for three kinds of laser crystals, Nd:YAG, Nd:YLF and Nd:YVO4. The results show that the modal field under thermal effect presents obvious deviation from the ideal mode under high power, and the modal structure shows that it contains many higher-order radial modes, with the angular mode order unchanged. Hence, the radial modal spectrum is broadened by the thermal effect. For an ideal vortex laser without thermal effect operating on the radial mode order 0 and angular mode order 1, Fig.(b) shows the modal structure with thermal effect under different pump power with the laser crystal thickness of 1mm. The ratio of the higher-order modes increases and the modal structure becomes more and more complex as the pump power increasing. The ratio of the ideal mode is 0.99, 0.97, 0.90, 0.79 and 0.61, under the pump power of 10 W, 20 W, 40 W, 60 W and 100 W, respectively. Moreover, the Nd:YVO4 laser has the largest and the Nd:YAG laser has the smallest modal spectrum broadening under the same pump power. Fig.(c) shows the variation of the modal purity with the pump power. The modal purity of the Nd:YVO4 and the Nd:YLF laser decreases to 0.35 and 0.44 at the pump power of 100 W, respectively. We also investigated the modal structure under different absorption coefficients and crystal thicknesses. A larger absorption coefficient or a smaller crystal thickness leads to a larger radial modal spectrum broadening and a smaller modal purity. These results demonstrate that in the high-power thin-disk vortex laser design, the disk thickness and the absorption coefficient need to be comprehensively optimized with the modal spectrum broadening taken into consideration.
-
Keywords:
- solid-state laser /
- vortex beam /
- thermal effect /
- radial modal spectrum broadening
-
[1] Wang J, Yang J Y, Fazal I M, Ahmed N, Yan Y, Huang H, Ren Y X, Yue Y, Dolinar S, Tur M, Willner A E 2012 Nat. Photonics 6 488
[2] Gibson G, Courtial J, Padgett M J, Vasnetsov M, Pas’ko V, Barnett S M, Franke-Arnold S, 2004 Opt. Express 12 5448
[3] Willner A E, Zhao Z, Ren Y X, Li L, Xie G D, Song H Q, Liu C, Zhang R Z, Bao C J, Pang K 2018 Opt. Commun. 408 21
[4] Lavery M P J, Speirits F C, Barnett S M, Padgett M J 2013 Science 341 537
[5] Belmonte A, Rosales-Guzman C, Torres J P 2015 Optica 2 1002
[6] Yang W D, Qiu X D, Chen L X 2020 Chin. J. Lasers 47 0500013 (in Chinese) [杨伟东, 邱晓东, 陈理想 2020 中国激光 47 0500013]
[7] Yang S H, Liao Y Q, Lin X T, Liu X Y, Qi R Y, Hao Y 2021 Infrared Laser Eng. 50 20211040 (in Chinese) [杨苏辉,廖英琦,林学彤,刘欣宇,齐若伊,郝燕 2021 红外与激光工程 50 20211040]
[8] Jantzi A, Jemison W, Laux A, Mullen L, Cochenour B 2018 Opt. Express 26 2668
[9] Baghdady J, Miller K, Morgan K, Byrd M, Osler S, Ragusa R, Li W Z, Cochenour B M, Johnson E G 2016 Opt. Express 24 9794
[10] Shen Y J, Wang X J, Xie Z W, Min C J, Fu X, Liu Q, Gong M L, Yuan X C 2019 Light Sci. Appl. 8 90
[11] Liu Q, Pan J, Wan Z S, Shen Y J, Zhang H K, Fu X, Gong M L 2020 Chin. J. Lasers 47 0500006 (in Chinese) [柳强,潘婧,万震松,申艺杰,张恒康,付星,巩马理 2020 中国激光 47 0500006]
[12] Forbes A 2019 Laser Photonics Rev. 13 1900140
[13] Forbes A, Oliveira M D, Dennis M R 2021 Nat. Photonics 15 253
[14] Sun X B, Zhu Q H, Liu L Q, Huang W Q, Zhang Y, Wang W Y, Geng Y C 2017 Laser Optoelectron. P. 54 070001 (in Chinese) [孙喜博,朱启华,刘兰琴,黄晚晴,张颖,王文义,耿远超 2017 激光与光电子学进展 54 070001]
[15] Fu S Y, Gao C Q 2019 Acta Opt. Sin. 39 0126014 (in Chinese) [付时尧,高春清 2019 光学学报 39 0126014]
[16] Chang N, Jin L W, Gao W 2019 Acta Opt. Sin. 39 0319001 (in Chinese) [常宁,金立伟, 高玮 2019 光学学报 39 0319001]
[17] Zhao Y G, Chen B, Zheng C S, Jia D W, Dong J F, Guo J, Wang Z X, Yu H H, Zhang H J 2024 Laser Photonics Rev. 18 2301089
[18] Pan J, Shen Y J, Wan Z S, Fu X, Zhang H K, Liu Q 2020 Phys. Rev. Appl. 14 044048
[19] Zhao Y G, Wang L, Chen W D, Loiko P, Mateos X, Xu X D, Liu Y, Shen D Y, Wang Z P, Xu X G, Griebner U, Petrov V 2021 Photonics Res. 9 357
[20] Qiao Z, Xie G Q, Wu Y H, Yuan P, Ma J G, Qian L J, Fan D Y 2018 Laser Photonics Rev. 12 1800019
[21] Song X L, Li B B, Wang S Y, Cai D F, Wen J G, Guo Z 2008 Infrared Laser Eng. 37 73 (in Chinese) [宋小鹿,李兵斌,王石语,蔡德芳,文建国,过振 2008 红外与激光工程 37 73]
[22] Yao Y C, Liu D L, Huang C Y, Xu G W, Wang B 2016 Acta Photonica Sin. 45 131 (in Chinese) [姚育成,刘丹琳,黄楚云,徐国旺,王贝 2016 光子学报 45 131]
[23] Fang H L 2014 Optical Resonators and Gravitational Wave Detection (Beijing: Science Press) pp78—80 (in Chinese) [方洪烈 2014 光学谐振腔与引力波探测 (北京:科学出版社) 第78—80页]
[24] Koechner W 2005 Solid-State Laser Engineering(fifth edition), (Beijing: World Publishing Corporation) pp46—83
计量
- 文章访问数: 45
- PDF下载量: 2
- 被引次数: 0
下载:
