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Full-silica metamaterial wave plate for high-intensity UV lasers
Optica ( IF 10.4 ) Pub Date : 2021-10-26 , DOI: 10.1364/optica.434662
Nicolas Bonod , Pierre Brianceau , Jérôme Neauport

Bringing light–matter interactions into novel standards of high-energy physics is a major scientific challenge that motivated the funding of ambitious international programs to build high-power laser facilities. The major issue to overcome is to avoid laser intensity heterogeneities over the target that weaken the light–matter interaction strength. Laser beam smoothing aims at homogenizing laser intensities by superimposing on the target laser speckle intensities produced by orthogonal left and right circularly polarized beams. Conventional wave plates based on anisotropic crystals cannot support the laser fluences of such lasers, and the challenge is now to design wave plates exhibiting a high laser induced damage threshold (LIDT). Fused silica exhibits high LIDT, but its isotropic dielectric permittivity prevents effects on polarization retardance. Metamaterials have been widely investigated to tailor the phase and polarization of light but with plasmonic or high-refractive-index materials, and applying this approach with silica is highly challenging due to the weak optical contrast between silica and air or vacuum. Here we design and fabricate a silica-based metasurface acting almost like a quarter-wave plate in the UV spectral range, fulfilling the numerous constraints inherent to high-power laser beamlines, in particular, high LIDT and large sizes. We numerically and experimentally demonstrate that fused silica etched by deep grooves with a period shorter than the wavelength at 351 nm operates the linear-to-quasi circular polarization conversion together with a high transmission efficiency and a high LIDT. The high aspect ratio of the grooves due to the short period imposed by the short wavelength and the deepness of the grooves required to overcome the weak optical contrast between silica and air is experimentally obtained through a CMOS compatible process.

中文翻译:

用于高强度紫外激光器的全二氧化硅超材料波片

将光与物质的相互作用纳入高能物理学的新标准是一项重大的科学挑战,它激发了雄心勃勃的国际计划以建造高功率激光设施的资金。要克服的主要问题是避免目标上的激光强度不均匀性削弱光-物质相互作用强度。激光光束平滑旨在通过叠加在由正交的左、右圆偏振光束产生的目标激光散斑强度上来均匀化激光强度。基于各向异性晶体的传统波片无法支持此类激光器的激光能量密度,现在的挑战是设计具有高激光诱导损伤阈值 (LIDT) 的波片。熔融石英具有高 LIDT,但其各向同性的介电常数可防止对偏振延迟的影响。超材料已被广泛研究以定制光的相位和偏振,但使用等离子体或高折射率材料,并且由于二氧化硅与空气或真空之间的弱光学对比度,将这种方法应用于二氧化硅非常具有挑战性。在这里,我们设计和制造了一个几乎像紫外光谱范围内的四分之一波片的二氧化硅基超表面,满足了高功率激光束线固有的众多限制,特别是高 LIDT 和大尺寸。我们通过数值和实验证明,由周期短于 351 nm 波长的深凹槽蚀刻的熔融石英可实现线性到准圆偏振转换,同时具有高传输效率和高 LIDT。由于短波长施加的短周期以及克服二氧化硅和空气之间弱光学对比度所需的凹槽深度,凹槽的高纵横比是通过CMOS兼容工艺实验获得的。
更新日期:2021-11-20
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