Generating Ultrabroadband Deep-UV Radiation and Sub-10 nm Gap by Hybrid-Morphology Gold Antennas.
Generating Ultrabroadband Deep-UV Radiation and Sub-10 nm Gap by Hybrid-Morphology Gold Antennas.
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DOI：
10.1021/acs.nanolett.9b02100
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发表时间：
2019-06
期刊：
影响因子：
10.8
通讯作者：
Liping Shi;J. Andrade;A. Tajalli;J. Geng;J. Yi;T. Heidenblut;F. Segerink;I. Babushkin;M. Kholodtsova;H. Merdji;B. Bastiaens;U. Morgner;M. Kovacev
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文献类型：
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作者：
Liping Shi;J. Andrade;A. Tajalli;J. Geng;J. Yi;T. Heidenblut;F. Segerink;I. Babushkin;M. Kholodtsova;H. Merdji;B. Bastiaens;U. Morgner;M. Kovacev
我们通过实验研究了混合形态金光学天线与几周期钛宝石激光器之间高达烧蚀强度的相互作用，展示了丰富的非线性等离子体效应以及在相干频率上转换和纳米加工技术中的有前景的应用。混合天线的二维阵列由椭圆形孔径和短轴上的蝴蝶结组成。领结的等离激元共振频率相对于激光中心频率发生红移，因此主要增强长波长的三次谐波光谱。两个相邻椭圆形孔径之间的金膜形成沙漏形结构，充当“等离子体透镜”，从而强烈增强小区域内的表面电流。这种增强的表面电流产生深深渗透到基板中的旋转磁场。在共振频率下，蝴蝶结进一步增强了磁场。沙漏的谐振频率相对于激光中心频率发生蓝移。因此，它显着地将三次谐波光谱向短波长延伸。由此产生的三次谐波信号范围为 230 至 300 nm，比蓝宝石晶体的发射范围宽得多。此外，沙漏天线颈部内的表面电流集中导致通过激光烧蚀进行结构修改，产生亚 10 nm 的尖锐金属间隙。此外，激光照射后，光场热点被印在天线周围，使我们能够确认电近场强度的亚波长增强。
We experimentally investigate the interaction between hybrid-morphology gold optical antennas and a few-cycle Ti:sapphire laser up to ablative intensities, demonstrating rich nonlinear plasmonic effects and promising applications in coherent frequency upconversion and nanofabrication technology. The two-dimensional array of hybrid antennas consists of elliptical apertures combined with bowties in its minor axis. The plasmonic resonance frequency of the bowties is red-shifted with respect to the laser central frequency and thus mainly enhances the third harmonic spectrum at long wavelengths. The gold film between two neighboring elliptical apertures forms an hourglass-shaped structure, which acts as a "plasmonic lens" and thus strongly reinforces surface currents into a small area. This enhanced surface current produces a rotating magnetic field that deeply penetrates into the substrate. At resonant frequency, the magnetic field is further intensified by the bowties. The resonant frequency of the hourglass is blueshifted with respect to the laser central frequency. Consequently, it spectacularly extends the third harmonic spectrum toward short wavelengths. The resultant third harmonic signal ranges from 230 to 300 nm, much broader than the emission from a sapphire crystal. In addition, the concentration of surface current within the neck of the hourglass antenna results in a structural modification through laser ablation, producing sub-10 nm sharp metallic gaps. Moreover, after laser illumination the optical field hotspots are imprinted around the antennas, allowing us to confirm the subwavelength enhancement of the electric near-field intensity.