飞秒激光在磁旋光玻璃中写入光波导的研究

Femtosecond-Laser-Written Waveguide in Magneto-Optical Glass

飞秒激光诱导折射率变化提供了一种灵活的三维光子器件制作方法。具有法拉第效应的磁旋光玻璃在集成光学中有广泛的应用前景。研究了1kHz重复频率的飞秒激光在磁旋光玻璃中刻写光波导的特征,测试了不同刻写参数下波导的导光模式,研究了写入速度和写入功率对波导折射率、模场直径的影响,给出了波导形成的写入窗口范围。实验结果表明,在采用10×显微物镜,写入速度40μm/s,写入功率3mW时,获得了980nm激光处模场直径为10μm,损耗为1.53dB/cm的波导,有利于实现波导和单模光纤之间的模式耦合,且波导区域费尔德系数只有轻微减小(约2.8%)。

Femtosecond-laser-induced refractive index modification has provided a flexible tool to fabricate three- dimensional photonic devices. Magneto-optical （MO） glass is widely used in integrated optics because of its Faraday rotation. Femtosecond laser at 1 kHz repetion rate is used to write waveguides in MO glass, then near-field modes of waveguides written by different focusing parameters are measured, and the refractive index changes in the written regions and mode field diameters as functions of writing parameters （scanning speed and writing power） are obtained, which show a writing window of waveguide formation in MO glass. Experimental results show that the Verdet constant in the written region only has a slight reduction （about 2.8 % ） under a special writing parameter set （10 X, objective scanning speed 40 μm/s, laser power 3 mW） ; the loss of the waveguide is 1.53 dB/cm, and its mode field diameter is 10 μm injected by 980 rim, so it is practicable to couple light from fiber into waveguide written by femtosecond laser.