This paper describes two surface treatments for silicon dual-pillar dielectric laser accelerators (DLAs), which increase the laser-induced damage threshold (LIDT) and therefore the maximum achievable acceleration gradient. Hydrogen annealing reduces the surface roughness of the silicon pillars and mesa, making the LIDT less dependent on surface perturbations incurred during fabrication, as well as causing damage to occur at predictable locations. Hydrogen annealing decreases the range of the measured LIDT from $ 5.3 - 10\;{\rm mJ/cm^2} $ to $ 9.5 - 10.2\;{\rm mJ/cm^2} $ with 1960 nm 300 fs pulses. Additionally, 90 nm of low-stress silicon nitride film coating on the annealed DLA improves the damage fluence by 27%. Smoother interfaces, possibly combined with charge transfer from the pillars to the nitride coating, decrease the range of the LIDT and increase the damage fluence. The surface-treated DLAs accelerate 97 keV electrons with an acceleration gradient of $ 178 \pm 1.8\;{\rm MeV/m} $, an increase of 11% over the previous maximal gradient achieved with dual-pillar DLAs.

中文翻译：

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介电激光加速器的表面处理可增加激光引起的损伤阈值

本文介绍了硅双支柱介电激光加速器（DLA）的两种表面处理方法，它们提高了激光诱导的损伤阈值（LIDT），从而提高了可达到的最大加速度梯度。氢退火降低了硅柱和台面的表面粗糙度，使得LIDT较少地依赖于制造期间产生的表面扰动，并导致在可预测位置发生损坏。氢退火将测得的LIDT范围从$ 5.3-10 \; {\ rm mJ / cm ^ 2} $降低到$ 9.5-10.2 \; {\ rm mJ / cm ^ 2} $使用1960 nm 300 fs脉冲 此外，在退火的DLA上涂覆90 nm的低应力氮化硅膜可将损伤通量提高27％。较光滑的界面，可能与从柱子到氮化物涂层的电荷转移相结合，会减小LIDT的范围并增加损伤通量。经表面处理的DLA加速97 keV电子，加速梯度为$ 178 \ pm 1.8 \; {\ rm MeV / m} $，比以前使用双支柱DLA达到的最大梯度增加了11％。