飞秒laser烧蚀蓝宝石基宽带毫米波增透结构
Broadband, millimeter-wave anti-reflective structures on sapphire ablated with femto-second laser
摘要：
我们设计，制造和测量的抗反射涂层（ARC）的蓝宝石，具有116%的分数带宽和至少97%的毫米波波段的传输。ARC是基于图案化的类似于亚波长结构（SWS），使用烧蚀与15 W飞秒激光器在1030 nm下工作。两个圆盘的每一个的一侧用SWS制造，SWS具有0.54 mm的节距和2 mm的高度。平均消融体积去除率为1.6 mm $^{3}$ /min。两个圆盘夹层的测量显示在43和161 GHz之间的透射率高于97%。我们表征仪器极化（IP）所产生的差分传输由于不对称SWS。我们发现，与适当的对齐的两个光盘三明治RMS IP整个频带预计为0.07%，在正常的入射角，入射角小于0.6%，高达20度。这些结果表明，激光烧蚀蓝宝石和其他硬质材料（如氧化铝）上的慢波结构是制备宽带ARC的有效方法。
英文摘要：
We designed, fabricated, and measured anti-reflection coating (ARC) on sapphire that has 116% fractional bandwidth and transmission of at least 97% in the millimeter wave band. The ARC was based on patterning pyramid-like sub-wavelength structures (SWS) using ablation with a 15 W femto-second laser operating at 1030 nm. One side of each of two discs was fabricated with SWS that had a pitch of 0.54 mm and height of 2 mm. The average ablation volume removal rate was 1.6 mm$^{3}$/min. Measurements of the two-disc sandwich show transmission higher than 97% between 43 and 161 GHz. We characterize instrumental polarization (IP) arising from differential transmission due to asymmetric SWS. We find that with proper alignment of the two disc sandwich RMS IP across the band is predicted to be 0.07% at normal incidence, and less than 0.6% at incidence angles up to 20 degrees. These results indicate that laser ablation of SWS on sapphire and on other hard materials such as alumina is an effective way to fabricate broad-band ARC.
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