光纤型宽带可调连续波差频产生中红外激光器转换效率的研究

以掺镱光纤激光器为抽运源、掺铒光纤激光器后接掺铒光纤放大器为信号源,利用周期极化掺镁铌酸锂晶体,研究了全光纤化差频产生中红外激光器的转换效率特性。结果表明,抽运光和信号光偏振态影响差频产生过程的转换效率,利用偏振控制器,可将抽运光和信号光偏振方向调节到与晶体光轴方向平行,以获得高的转换效率。抽运光和信号光的光束质量既影响差频产生过程的转换效率,又决定晶体纵向位置的容限,当聚焦系统由自聚焦透镜和焦距100mm平凸透镜组成时,相对转换效率达0.717mW-2,晶体纵向位置容限为44mm。此外,差频光在3126.36~3529.6nm范围内调谐时,转换效率基本保持不变。

Investigation of Conversion Efficiency of Widely Tunable Continuous-Wave Mid-IR Difference Frequency Generation Fiber-type Laser

The conversion efficiency properties of a widely tunable continuous wave Mid-IR fiber-type laser source based on difference frequency generation(DFG)process in a periodically poled MgO-doped LiNbO3(PPMgLN)crystal,which uses a ytterbium-doped fiber laser(YDFL)as the pump and an erbium-doped fiber laser(EDFL)cascaded by an erbium-doped fiber amplifier(EDFA)as the signal respectively,are investigated in this paper.Our results show that,the polarization states of pump and signal beams influence the conversion efficiency of the DFG process.By using polarization controllers(PCs),the polarization orientations of pump and signal beams may be respectively adjusted to be parallel to the principle optical axis of the crystal for obtaining high conversion efficiency.The beam quality of the pump and the signal not only influence on the conversion efficiency of the DFG process,but also determine the tolerance of the crystal position along the beams.For a focusing system formed by a fiber grin lens and a convex-plane lens with the focal length of 100mm,the conversion efficiency and the tolerance for the DFG source are 0.717 mW-2 and 44 mm,respectively.Moreover,the conversion efficiency of the DFG process changes very small when the idle light is tuned in the wavelength range between 3126.36 nm and 3529.6 nm.