Jilin Provincial Key Laboratory of Solid Laser Technology and Application, School of Science, Changchun University of Science and Technology, Changchun 130022, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant Nos. 11974060, U20A20214) and the Young and Middle-aged Scientific and Technological Innovation Leaders and Team Project of Jilin Provincial Department of Science and Technology, China (Grant No. 20190101004JH)
Received Date:08 March 2021
Accepted Date:05 April 2021
Available Online:07 June 2021
Published Online:20 September 2021
Abstract:In this paper, an orthogonally polarized dual-wavelength laser based on dual-end pumped Nd3+ doped MgO:LiNbO3 is reported. Besides, the output wavelength of the orthogonally polarized dual-wavelength is regulated. According to the crystal character, the polarized fluorescence spectrum of the crystal is chosen as the starting point. The oscillation mechanism of the dual-wavelength Nd3+ doped MgO:LiNbO3 laser at 1084 nm and 1093 nm is analyzed theoretically. The relationship between the focal length of the crystal thermal lens and the stimulated emission cross-sectional ratio is established, and the effects of different temperatures on the output of single-wavelength Nd3+ doped MgO:LiNbO3 laser and on the output of dual-wavelength Nd3+ doped MgO:LiNbO3 laser are analyzed. In addition, The single-wavelength output region of 1084 nm and 1093 nm are derived respectively, and the mixed dual-wavelength working area at 1084 nm and 1093 nm are also given. The influences of different resonator parameters on the output dual-wavelength Nd3+ doped MgO:LiNbO3 laser are analyzed. It is worth mentioning that a method of adjusting the output of dual-wavelength laser by changing the resonant cavity structure is given. In the experiment, a-cut Nd:MgO:LiNbO3 crystal is double-end pumped by an semiconductor laser, of which the output wavelength is 813 nm. The output law of the two wavelengths of 1084 nm and 1093 nm is summarized. The output wavelength is regulated. When the laser cavity is not inserted by other optical elements, the maximum output power of 4.58 W at 1084 nm/1093 nm dual-wavelength laser under the pump power is 28 W and the pure single-wavelength laser maximum output power of 3.02 W at 1084 nm and 6.02 W at 1093 nm are obtained. The beam quality factor in the X- and Y-direction are $ M_X^2 $ = 1.70 and $ M_Y^2 $ = 1.81, respectively. The experimental results are in agreement with the theoretical analysis results. According to the change of the resonator parameters, the 1084 nm and 1093 nm pure single-wavelength laser alternate output and orthogonal polarization dual-wavelength laser synchronous output are achieved based on the Nd3+ doped MgO:LiNbO3 laser, thus establishing a theoretical and experimental foundation for the controllable output and application of orthogonal polarization dual-wavelength. It greatly expand the application range of dual-wavelength laser which can control the orthogonal polarization of 1084/1093 nm. Keywords:dual-wavelength of 1084 nm and 1093 nm/ Nd:MgO:LiNbO3/ orthogonal polarization/ regulating wavelength
图 4 腔长70 mm、输出镜曲率R = 300 mm时的双波长共振区间 Figure4. Dual-wavelength resonance range when the cavity length is 70 mm and the output mirror curvature R = 300 mm
图4中黑色线条代表1084 nm激光的稳定区间, 红色线条代表1093 nm激光的稳定区间. 可以看出, 随着泵浦注入功率的提升, 受激发射截面比开始发生变化, 1084 nm激光开始逐渐失稳. 当受激发射截面比大于0.60时, 1093 nm激光开始起振, 当受激发射截面比大于0.72时, 1084 nm激光振荡失稳, 仅为1093 nm单波长激光输出. 在此基础上, 继续使用表1中的谐振腔2和谐振腔3进行模拟, 模拟结果如图5和图6所示. 图 5 腔长100 mm、输出镜曲率R = 300 mm时的双波长共振区间 Figure5. Dual-wavelength resonance range when the cavity length is 100 mm and the output mirror curvature R = 300 mm.
图 6 腔长100 mm、输出镜曲率R = 150 mm时的双波长共振区间 Figure6. Dual-wavelength resonance range when the cavity length is 100 mm and the output mirror curvature R = 150 mm.
综合对比三种谐振腔模拟结果, 由图4和图5可知, 当M2曲率R = 300 mm, 谐振腔长度为70 mm时, 双波长共振的泵浦注入功率区间为15—38 W; 谐振腔长度为100 mm时, 双波长共振的泵浦注入功率区间为15—28 W. 由此可知, 当输出镜曲率不变, 谐振腔腔长度改变时, 双波长共振区间发生明显变化. 由图5与图6可知, 当谐振腔长度为100 mm, M2曲率由R = 300 mm改变为R = 150 mm时, 双波长共振区间的位置改变并不明显.
图 9 1084和1093 nm激光波长的偏振态 (a) 1084 nm偏振态; (b) 1093 nm偏振态 Figure9. Polarization states of 1084 and 1093 nm laser wavelengths: (a) Polarization states of 1084 nm; (b) polarization states of 1093 nm.