飞秒激光调控非线性光学晶体和周期性纳米结构取向

Orientable Nonlinear Optical Crystals and Periodic Nanostructure by Femtosecond Laser Irradiation

通过高频(100~500 kHz)飞秒激光直写可在组成是Li_(2)O-Nb_(2)O_(5)-SiO_(2)的玻璃内部同时控制纳米非线性光学晶体和周期结构取向。该周期结构为发生纳米尺度相分离的晶态和非晶态交替结构,并可通过激光偏振方向来控制朝向。随着激光注入能量的增加出现了3个改性区间:低能量下改性非晶态,对氢氟酸(HF)的刻蚀速度高于玻璃基底;中能量下纳米晶体极轴趋向和激光偏振方向垂直,随着激光频率的提高,获得此区间的脉冲能量窗口急剧减小;高能量下微米晶粒,并且晶体的产生受写入模式影响(写入方向和激光偏振方向的夹角)。该研究发现有利于理解超快激光-物质相互作用和制备三维光器件。

Herein,we show the ability to control nonlinear optical nanocrystal orientation and nanostructure orientation at the same time in the Li_(2)O-Nb_(2)O_(5)-SiO_(2) glass by high repetition rate(100-500 kHz)femtosecond laser direct writing.A selforganized nanostructure with nanoscale phase separation,nonlinear optical nanocrystals embedded in an amorphous network,can be oriented by laser polarization.With the increase of laser power,three modified regimes are revealed.At low laser power,a modified amorphous structure is obtained and has higher HF etching rate than that of the glass substrate.At moderate laser power,polar axes of nanocrystals tend to be perpendicular to laser polarization direction.The range of pulse energy narrows dramatically with the increase of repetition rate.At high laser power,microcrystals are obtained and crystallization is very sensitive to writing mode(the angle between writing direction and laser polarization direction).These findings shed light on the comprehension of ultra-fast laser-matter interaction and provide a new path toward fabricating three-dimensional optical devices.