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利用中心波长为1040nm、脉宽为190fs、重复频率在200～5000kHz之间可调的飞秒激光对熔融石英进行微加工。研究了烧蚀阈值随脉冲重复频率、扫描速度的变化规律,阐明不同参数下热扩散效应及热累积效应对烧蚀过程的主导作用。在最优化条件下,制作了双线波导,可以对1040nm激光实现圆形基模传输。进一步制作了椭圆晶胞的六角微结构波导,对1040nm激光可以输出近高斯强度分布的基模,模场面积达到247.48μm2。该微结构波导可实现单偏振传输,消光比达9.05,波导数值孔径约0.017。
The fused silica was microfabricated with a femtosecond laser with a center wavelength of 1040 nm, a pulse width of 190 fs and a repetition frequency between 200 and 5000 kHz. The variation rule of ablation threshold with pulse repetition frequency and scanning speed was studied. The effects of heat diffusion and heat accumulation under different parameters on the ablation process were clarified. Under the optimized conditions, a two-wire waveguide was fabricated, which can realize circular fundamental mode transmission to 1040nm laser. The hexagonal microstructure waveguide of elliptical cell was further fabricated. The fundamental mode with nearly Gaussian intensity distribution can be output to 1040nm laser and the area of mode field reaches 247.48μm2. The microstructured waveguide can achieve single polarization transmission with an extinction ratio of 9.05 and a waveguide numerical aperture of about 0.017.