Nanograting fabricated with femtosecond laser pulses
Nanograting fabricated with femtosecond laser pulses
复制标题
用飞秒激光脉冲制造纳米光栅
DOI：
10.1117/2.1201210.004516
复制
发表时间：
2012
期刊：
影响因子：
--
通讯作者：
G. Miyaji and K. Miyazaki
中科院分区：
文献类型：
--
作者：
Atsushi Sugita;Yasuaki Sato;Kazuma Ito;Kenta Murakami;Yasuaki Tamaki;Nobuyuki Mase;Yoshimasa Kawata and Shigeru Tasaka;Kenji Tamasaku;G. Miyaji and K. Miyazaki
在各种材料的精密加工中，强飞秒激光脉冲是一种常见的工具，例如，在制造光电器件和微电子机械系统中需要这些材料。使用飞秒激光脉冲进行材料加工的优点是超快地将高密度能量沉积到靶上，从而抑制了光物质相互作用中不希望看到的热和机械效应。此外，在飞秒激光烧蚀实验中对自组织表面纳米结构形成的观察发现，这些结构的尺寸通常是激光波长的1/10-1/5，1-4，这表明飞秒激光有可能雕刻或“纳米加工”比衍射极限更小的结构。为了寻找飞秒激光纳米加工的新途径，我们将注意力集中在纳米尺度的、超快的光-物质相互作用对纳米结构的影响上。我们特别探索了低通量飞秒激光脉冲叠加多次的使用。我们对介质和半导体材料的初步研究表明，激光诱导的近场在波纹表面的纳米尺度烧蚀中起着基础性的作用，其周期性的起源可以归因于表面层中表面等离子体激元(SPP)的激发。7、8基于纳米结构模型，我们成功地在晶态氮化镓(GaN)表面制备了均匀周期的纳米晶。我们在空气中(而不是在真空中)进行了实验，使用了重复频率为10赫兹的钛宝石激光系统输出的线偏振800 nm、100-fs激光脉冲。在两步过程的第一步，我们将飞秒激光输出分成两束。如图1(A)所示，光束1通常入射到目标上，而光束2入射的角度与法线成一定角度。两束光束在靶面上重叠，在垂直于激光的方向上产生干涉条纹
Intense femtosecond laser pulses are a common tool in precision processing of a variety of materials, which are needed in the fabrication of, for example, electro-optical devices and microelectromechanical systems. The advantage of using femtosecond laser pulses for material processing is the ultrafast deposition of high-density energy onto the target and the resulting suppression of undesirable thermal and mechanical effects in the lightmatter interaction. In addition, observations of self-organized, surface nanostructure formations in femtosecond-laser ablation experiments have found the size of these structures is typically 1/10–1/5 of the laser wavelength, 1–4 which suggests that femtosecond lasers have the potential to sculpt, or ‘nanoprocess,’structures smaller than the diffraction limit. To find a new route to femtosecond-laser nano-processing, we focused our attention on the nanoscale, ultrafast light-matter interaction responsible for nanostructuring. We explored in particular the use of superimposed multiple shots of low-fluence femtosecond laser pulses. Our preliminary studies with dielectric and semiconductor materials have shown that the laserinduced near-field plays a fundamental role in the nanoscale ablation of a corrugated surface, 5, 6 and the origin of periodicity can be attributed to the excitation of surface plasmon polaritons (SPPs) in the surface layer. 7, 8Based on the model of nanostructuring, we successfully fabricated a nanograting with a uniform period on a crystalline gallium nitride (GaN) surface. We performed our experiment in air (as opposed to vacuum) using linearly polarized 800-nm, 100-fs laser pulses from a Ti: sapphire laser system operated at a repetition rate of 10Hz. In the first-step of a two-step process, we split the femtosecond laser output into two beams. As schematically illustrated in Figure 1 (a), Beam 1 is normally incident on the target while Beam 2 is incident at an angle  with respect to the normal. The two beams overlap on the target surface to create interference fringes in the direction perpendicular to the laser