Efficient Magnetic Resonance Amplification and Near-Field Enhancement from Gain-Assisted Silicon Nanospheres and Nanoshells

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• 作者：DaJian Wu ; HaiQun Yu ; Jie Yao ; QingYu Ma ; Ying Cheng ; XiaoJun Liu
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：June 23, 2016
• 年：2016
• 卷：120
• 期：24
• 页码：13227-13233
• 全文大小：578K
• 年卷期：0
• ISSN：1932-7455

文摘

Strong artificial magnetic responses play a pivotal role in the unique optical properties of metamaterials, such as cloaking, Fano resonance, and negative refraction. We investigate the magnetic resonances of gain-assisted Si nanospheres and SiO₂–Si nanoshells. It is found that the super-resonances occur successively at the octupole, quadrupole, and dipole magnetic modes of the active Si nanosphere or SiO₂–Si nanoshell by changing the gain coefficient. At the super-resonances, the magnetic scatterings and the local electric fields are all extremely enhanced. The corresponding surface-enhanced Raman spectroscopy (SERS) enhancement factors at the magnetic super-resonances could reach about 10¹⁰–10¹⁵, which are enough for single-molecule detection. In particular, the electric scatterings of the active Si nanosphere and SiO₂–Si nanoshell are all very weak at the super-resonances. Therefore, the active Si nanosphere and SiO₂–Si nanoshell should be excellent SERS substrates with weak background radiation. The extremely strong magnetic resonances also could be used for designing new metamaterials and devices.