Bai Shi, Li Zhaoxu, Obata Kotaro, Kawabata Shota, Sugioka Koji
Advanced Laser Processing Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Hebei Key Laboratory of Materials Near-Net-Forming Technology, School of Material Science and Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China.
Nanophotonics. 2023 Jan 16;12(8):1499-1510. doi: 10.1515/nanoph-2022-0657. eCollection 2023 Apr.
Fabrication of nanostructures with a feature size much smaller than the laser wavelength is challenging due to the optical diffraction limit. It's well known that the irradiation of polarized ultrafast laser generates periodic nanostructures, so called laser-induced periodic surface structures (LIPSS). Owing to the modulated field, the surface is periodically ablated to form specific patterns, which can be used for some photonic applications including surface-enhanced Raman scattering (SERS). In this paper, we investigate the morphologies of LIPSS on ZnO substrates by mask-less ultrafast laser processing. By adjusting the laser processing parameters, including fluence, pulse number, polarization, and pulse duration, the homogenous nanostrip array and nanopillar array are created. Furthermore, by adjusting the laser fluence, a single nanogroove with a width of ∼20 nm and a single nanocavity with a diameter of ∼24 nm are created. The gold nanoparticles are then coated on the ZnO nanopillar array for SERS application. We found that the concentration of defects in ZnO substrate is increased by the laser irradiation, which is beneficial for SERS performances to achieve an enhancement factor of SERS as high as 2.28 × 10.
由于光学衍射极限，制造特征尺寸远小于激光波长的纳米结构具有挑战性。众所周知，偏振超快激光的照射会产生周期性纳米结构，即所谓的激光诱导周期性表面结构（LIPSS）。由于调制场的作用，表面被周期性烧蚀以形成特定图案，这些图案可用于包括表面增强拉曼散射（SERS）在内的一些光子应用。在本文中，我们通过无掩膜超快激光加工研究了ZnO衬底上LIPSS的形貌。通过调整激光加工参数，包括能量密度、脉冲数、偏振和脉冲持续时间，制备了均匀的纳米条阵列和纳米柱阵列。此外，通过调整激光能量密度，制备了宽度约为20nm的单个纳米凹槽和直径约为24nm的单个纳米腔。然后将金纳米颗粒涂覆在ZnO纳米柱阵列上用于SERS应用。我们发现激光照射会增加ZnO衬底中的缺陷浓度，这有利于SERS性能，使SERS增强因子高达2.28×10。
