Xie Lingyun, Zhang Jinlong, Zhang Zhanyi, Ma Bin, Li Tongbao, Wang Zhanshan, Cheng Xinbin
Opt Express. 2021 Jan 18;29(2):2669-2678. doi: 10.1364/OE.415847.
Broadband multilayer dielectric gratings (MDGs) with rectangular HfO grating profile were realized for the first time using a novel fabrication process that combines laser interference lithography, nanoimprint, atomic layer deposition and reactive ion-beam etching. The laser-induced damage initiating at the grating ridge was mitigated for two reasons. First, the rectangular grating profile exhibits the minimum electric-field intensity (EFI) enhancement inside the grating pillar compared to other trapezoidal profiles. Second, our etching process did not create nano-absorbing defects at the edge of the HfO grating where the peak EFI locates, which is unavoidable in traditional fabrication process. The fabricated MDGs showed a high laser induced damage threshold of 0.59J/cm for a Ti-sapphire laser with pulse width of 40 fs and an excellent broadband diffraction spectrum with 95% efficiency over 150 nm in TE polarization.
首次采用一种新颖的制造工艺实现了具有矩形HfO光栅轮廓的宽带多层介质光栅（MDG），该工艺结合了激光干涉光刻、纳米压印、原子层沉积和反应离子束蚀刻。由于两个原因，减轻了在光栅脊处引发的激光损伤。首先，与其他梯形轮廓相比，矩形光栅轮廓在光栅柱内部表现出最小的电场强度（EFI）增强。其次，我们的蚀刻工艺没有在HfO光栅边缘（峰值EFI所在位置）产生纳米吸收缺陷，而这在传统制造工艺中是不可避免的。所制造的MDG对于脉宽为40 fs的钛宝石激光器显示出0.59J/cm的高激光诱导损伤阈值，并且在TE偏振下在150 nm范围内具有95%效率的出色宽带衍射光谱。
