利用重复频率为1 kHz,中心波长为800 nm,脉冲宽度为120 fs的飞秒激光在掺Yb3+磷酸盐玻璃中刻写光波导,测试了不同参数下刻写的波导的导光模式,研究了写入速度和写入脉冲能量对模场直径、波导折射率的影响,给出了波导形成的写入窗口范围,对比测试了激光作用区域和未作用区域的荧光光谱特性。实验结果表明,在采用20×显微物镜,写入速度为20 μm/s,写入脉冲能量为1.8 μJ时,所得到的光波导在976 nm波段模场直径为20 μm,波导区域折射率改变为2.7×10-4,飞秒激光作用区域的荧光光谱与基质的荧光光谱几乎完全重合,荧光特性在飞秒激光作用后保持良好。利用双色镜和2% 的输出耦合镜构成了法布里珀罗(F-P)腔掺Yb3+波导激光器,获得了波长为1031 nm的连续激光输出,激光功率为2.9 mW。
Femtosecond laser with repetition rate of 1 kHz, central wavelength of 800 nm and pulse width of 120 fs is used to write waveguides in Yb3+phosphate glass, then near-field modes of waveguide written by different laser parameters are measured. The refractive index changes in the written region and mode field diameter as functions of writing parameters (scanning speed and writing pulse energy) are obtained, which show the writing window of waveguide formation in Yb3+phosphate glass. The fluorescence spectra of the waveguide and the bulk material are tested and compared. Experimental results show that there is no difference in the fluorescence spectra of the waveguide and the bulk material with 20× objective lens, scanning speed of 20 μm/s and pulse energy of 1.8 μJ, the mode field diameter is 20 μm injected at 976 nm, the refractive index change is 2.7×10-4, and the fluorescence properities keep the same after femtoscecond laser effect. Stable and continuous wave (CW) Yb3+doped waveguide laser is achieved in a Fabry-Perot cavity configuration by using dichronic mirror and 2% output coupler. An output with power of 2.9 mW at a central wavelength of 1031 nm is obtained.