实验搭建了全保偏结构的掺镱皮秒脉冲光纤激光器, 采用级联放大结构及双包层保偏光子晶体光纤将种子脉冲能量提升至最高10 μJ, 重复频率0.05～20.00 MHz连续可调。主放大器中的纤芯/包层直径为14/135 μm保偏光子晶体光纤, 不仅可以实现与少模双包层光纤的直接熔接, 确保光纤放大器的全光纤结构, 而且有效降低了皮秒脉冲放大过程中的非线性效应, 较好的保持了输出脉冲的时频域特性。采用1 064 nm皮秒脉冲光源结合扫描电镜, 照射浸泡在蒸馏水中的二氧化钛(TiO2)粉末压片, 制备出TiO2纳米颗粒, 利用透射式电子显微镜(TEM)对TiO2纳米颗粒尺寸进行了测量。当采用在100 kHz的重复频率, 每脉冲能量为5 μJ, 脉冲串内3脉冲工作方式, 制备所得的粒子直径分布在50~350 nm之间。当脉冲串内的脉冲数从3个增加至5个后, 制备出纳米颗粒的平均直径从234 nm缩小为162 nm, 且产率从3.9 mg/h提升至5.5 mg/h。

An Ytterbium-doped picosecond pulse laser has been demonstrated based on all polarization-maintaining (PM) fibers, cascade amplifier and double clad polarization-maintaining photonic crystal fiber were used to increase seed pulse energy to a maximum of 10 μJ, with a tunable repetition rate from 0.05 MHz to 20.00 MHz. The Polarization-maintaining photonic crystal fiber (core/cladding diameter of 14/135 μm) used in the main-amplifier not only realize the direct welding of less-mode double clad fiber which ensure the all fiber architecture, but also reduced the nonlinear effects in the process of picosecond pulse amplification, better to keep the time and frequency domain characteristic of the output pulse. Then, using 1 064 nm picosecond pulse light source combined with scanning electron microscopy, Titanium dioxide (TiO2) nanoparticles were prepared by picosecond laser irradiate on TiO2 tablet soaked in distilled water. A transmission electron microscope (TEM) was used to measure and analyze the diameter of TiO2 nanoparticles. The results showed that the particle size distributed between 50 nm to 350 nm when using the repetition frequency of 100 kHz, per pulse energy of 5 μJ, pulse sequence within 3 pulse. As the pulse number increased from 3 to 5, the average diameter of TiO2 nanoparticles decreased from 234 nm to 162 nm, and the productivity increased from 3.9 mg/h to 5.5 mg/h.