飞秒激光直写磁光玻璃波导研究  

Fabrication of magneto-optical glass waveguides by femtosecond laser direct writing

作　　者：郜向阳[1] 李玉栋[1] 孙骞[1] 田建国[1] 

机构地区：[1]南开大学物理科学学院,弱光非线性光子学教育部重点实验室,天津300071

出　　处：《光电子．激光》2015年第5期925-931,共7页Journal of Optoelectronics·Laser

基　　金：国家自然科学基金(61178004);国家重点基础研究专项基金(2011CB922003)资助项目

摘　　要：用飞秒激光在硼铝硅酸盐类磁光玻璃中直写光波导。对比了飞秒激光在TG20和TG28两种Tb3+浓度不同的硼铝硅酸盐玻璃中的磁光波导的效果,并研究了飞秒激光脉冲的能量和偏振对波导的模式以及Verdet常数的影响。实验结果表明,圆偏振光具有更低的阈值能量,且诱导的折射率增量高于同功率的线偏振光,首次在实验上证明飞秒直写加工硼铝硅酸盐磁光玻璃时,折射率的改变主要源于离子键的三或四光子吸收过程。磁光系数测量表明,飞秒激光的功率与偏振对TG28中波导Verdet常数的影响较弱,Verdet常数损失量小于体材料的15%,而在TG20中却可以达到70%。实验结果表明,TG28比TG20更适用于飞秒激光加工磁光微结构,即通过对磁光玻璃中掺杂离子浓度的选择,可以实现高磁光系数、高折射率调制的光学微结构的制备。In this work,we investigate the waveguide fabrication and the mechanism of femtosecond laser direct writing in borosilicate aluminum magneto-optical glass. We compare the characteristics of the magneto-optical waveguides fabricated in two kinds of glasses with different concentrations of Tb3＋ i ons,i, e. ,TG20 and TG28 glasses, and systematically study the dependence of the guiding modes and Verdet constant of waveguides on femtosecond laser pulsesr polarization and energy. The results show that the circularly polarized femtosecond pulses have lower fabrication threshold energy and can intro- duce larger increase in the refractive index change inside magneto-optical glass, compared with the linear ly polarized pulses. It confirms that the refractive index change in borosilicate aluminum glass mainly comes from the 3- or 4-photon absorption of ionic bonding. The magneto-optical coefficient measurement results prove that in TG28 glass, the power and polarization state of the incident pulses have small influ- ence on Verdet constant of waveguides. The decrease in Verdet constant of magneto-optical waveguide is less than 15~/~ of the value in bulk TG28 glass, whereas the decrease can reach 70% in TG20 glass. Therefore,TG28 glass is more appropriate to fabricate magneto-optical microstructures by using femto- second laser direct writing than TG20 glass. By careful selection of the dopant concentration in the mag neto-optical glass the optical microstruetures with high magneto-optical coefficient and high refractive in- dex modulation mav be fabricated.

关 键 词：飞秒激光 磁光效应 波导 磁光玻璃 

分 类 号：TN252[电子电信—物理电子学] O482.55[理学—固体物理]