飞秒激光诱导自组织纳米光栅偏振散射特性研究

Research on Polarized Scattering of Self-Organized Nanogratings Induced by Femtosecond Laser

实验证实飞秒激光在透明材料内部诱导的周期性纳米条纹具有特殊的光学特性。采用时域有限差分方法(FDTD)分别对单元纳米光栅和纳米光栅阵列的散射特性进行研究,分析结果显示纳米光栅的散射对入射激光的偏振方向敏感;散射强度与入射激光波长相关,波长越长、散射越弱。对于纳米光栅阵列,平行于纳米光栅的散射强度比垂直于纳米光栅的散射强度小两万倍。最后从理论上验证了Ⅱ类波导和纳米光栅偏振导光是由纳米光栅的散射引起的而不是双折射效应。

Experiments confirm that the femtosecond laser induced periodic nanogratings in a transparent material represents the novel optical properties. The scattering characteristics of nanogratings and nano-grating array are studied in detail by experiments and finite-difference time-domain （FDTD） respectively. Analysis result shows that scattering characteristics of nanogratings are sensitive to the polarization of the incident laser. For arrays of nanogratings, the scattering intensity in the laser polarization perpendicular to the nanograting is 20000 times larger than that in the laser polarization parallel to the nanograting. Morerover, the scattering intensity is dependent on the incident laser wavelength. The longer the wavelength is, the weaker the scattering intensity will be. The simulation results demonstrate that type II waveguide and the light polarized guide mechanism of nanograting are based on scattering characteristics of nanograting instead of birefringence effect theoretically.