【摘要】 用数值孔径为0.65的40倍显微透镜紧聚焦能量稍高于能量损伤阈值的200fs的钛宝石激光脉冲,分别在ZK6玻璃和K9玻璃内部导致局部折射率改变,在透明介质内部形成透射式相位衍射光栅.在635nm的HeNe激光照射下,通过对光栅衍射效率的数值拟合计算,得出了的光栅条纹宽度与实际测量基本吻合,这从侧面证明了折射率改变区域为超高斯型的假定.还对折射率改变区域的性质进行了分析.在实验上观察到脉冲间的相互影响将导致折射率改变区域范围的增大.从理论上给出了增加1级衍射效率的途径.更多还原

【Abstract】 The fabrication of an internal transmission diffraction grating with laser induced refractive index modification was demonstrated in ZK6 and K9 glasses respectively, using femtosecond (200 fs) Ti: sapphire laser with a energy that is near the energy threshold focused by 40× microscope objective with 0.65 NA. The diffraction efficiency of the grating was measured with a CW He Ne laser at 633 nm. The diffraction efficiency of the phase gratings was calculated with curve fitting. The width of the groove calculated with curve fitting accord with that was measured, it is confirmed the premise of the phase shift of each groove approximated by a supergaussian indirectly. It is observed that a groove is widened by multiple shot cumulative effect. A way increasing the diffraction efficiency is presented.更多还原