Regulation of orthogonally polarized dual­wavelength continuous wave laser based on double-end pumped Nd<sup>3+</sup> doped MgO:LiNbO<sub>3</sub>
Authors: Liu Hong-Zhi , Wang Yu-Heng , Zheng Hao , Zhao Yun-Feng , Yu Yong-Ji , Jin Guang-Yong ,   Jilin Provincial Key Laboratory of Solid Laser Technology and Application, School of Science, Changchun University of Science and Technology, Changchun 130022, China
Published: September 2021

In this paper, an orthogonally polarized dual-wavelength laser based on dual-end pumped Nd<sup>3+ </sup>doped MgO:LiNbO<sub>3</sub> 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 Nd<sup>3+ </sup>doped MgO:LiNbO<sub>3</sub> 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 Nd<sup>3+ </sup>doped MgO:LiNbO<sub>3</sub> laser and on the output of dual-wavelength Nd<sup>3+ </sup>doped MgO:LiNbO<sub>3</sub> 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 Nd<sup>3+ </sup>doped MgO:LiNbO<sub>3</sub> 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, <i>a</i>-cut Nd:MgO:LiNbO<sub>3</sub> 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 <i>X-</i> and <i>Y-</i>direction are <inline-formula><tex-math id="M3">\begin{document}$ M_X^2 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20210449_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20210449_M3.png"/></alternatives></inline-formula> = 1.70 and <inline-formula><tex-math id="M4">\begin{document}$ M_Y^2 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20210449_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20210449_M4.png"/></alternatives></inline-formula> = 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 Nd<sup>3+ </sup>doped MgO:LiNbO<sub>3</sub> 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.