Nano-dimple processing of silicon surfaces by femtosecond laser irradiation with dielectric particle templates in the Mie scattering domain
Nano-dimple processing of silicon surfaces by femtosecond laser irradiation with dielectric particle templates in the Mie scattering domain
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DOI：
10.1088/0022-3727/42/2/025502
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发表时间：
2009-01
期刊：
影响因子：
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通讯作者：
T. Sakai;T. Miyanishi;N. Nedyalkov;Y. Nishizawa;M. Obara
中科院分区：
文献类型：
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作者：
T. Sakai;T. Miyanishi;N. Nedyalkov;Y. Nishizawa;M. Obara
用800nm飞秒激光脉冲照射与硅衬底上光波长相当的介电粒子。利用这一介质粒子模板，得到了飞秒激光辐照的一种新颖而有趣的光强分布。这种光强分布的结果是在硅衬底上形成了独特的图案，这是由介电粒子的微透镜和Mie散射机制引起的。本文用时域有限微分法研究了由尺寸参数α = 2πr/λ（其中r为介电粒子半径，λ为入射激光波长）方程确定的粒子尺寸与光强分布的关系。尺寸参数的变化会引起粒子附近光强分布的显著变化。近场强度的分布是通过其在基底上的指纹来分析的，在基底上沉积颗粒并由飞秒激光脉冲照射。利用这种方法，我们定义了透镜效应和Mie散射贡献之间的边界。实验结果表明，在介电粒子的介导下，产生的近光强可以产生超过衍射极限的纳米孔。具体而言，在一定的边界条件下，加工后的纳米孔特征具有受入射光偏振控制的特征形状，其长轴垂直于入射光偏振的椭球形状。当介质颗粒小于入射波长时，透镜效应的贡献减小，光场强度分布主要由Mie散射机制决定。
Dielectric particles sized comparable to the wavelength of light mounted on silicon substrates are irradiated with 800 nm femtosecond laser pulses. From this template of dielectric particles, a novel and interesting optical intensity distribution of the femtosecond laser irradiation is obtained. A result of this optical intensity distribution is a distinct pattern on the silicon substrate, which stems from the micro-lens and Mie scattering mechanism by the dielectric particles. In this paper, we investigated the dependence of the particle size, determined by the equation for size parameter α = 2πr/λ where r is the radius of the dielectric particle and λ is the incident laser wavelength, on the optical intensity distribution using the finite differential time domain method. A change in the size parameter induces a significant change in the optical intensity distribution in the vicinity of the particle. The distribution of the near-field intensity is analysed by its fingerprint on a substrate where the particle is deposited and irradiated by the femtosecond laser pulse. Using this method, we define the boundary between the lens effect and the contribution from Mie scattering. The experimental results indicate that the generated near-optical intensity, mediated by the dielectric particles, can produce a nano-hole with a size that overcomes the diffraction limit. Specifically, given certain boundary conditions, the processed nano-hole features have a characteristic shape governed by the incident light polarization, which has an ellipsoidal shape with the long axis perpendicular to the polarization of the incident light. In the case of using dielectric particles smaller than the incident wavelength, the contribution of the lens effect diminishes and the optical field intensity distribution is determined predominantly by the Mie scattering mechanism.