School of Physics and Electronic Engineering, Guangzhou University , Guangzhou 510006, China.
Department of Electronic Engineering, College of Information Science and Technology, Jinan University , Guangzhou 510632, China.
Nano Lett. 2017 Aug 9;17(8):4853-4859. doi: 10.1021/acs.nanolett.7b01724. Epub 2017 Jul 12.
Significantly enhanced electric field in plasmonic hot spots can dramatically increase the linear and nonlinear absorption of light, leading to a high-temperature electron gas which radiates, through mainly intraband transition, a broadband luminescence quite similar to blackbody radiation. Here, we demonstrate that such hot-electron intraband luminescence (HEIL) can also be achieved by exploiting the significantly enhanced electric field at the magnetic dipole resonances of gallium arsenide (GaAs) nanospheres (NSs). We show that monocrystalline GaAs NSs with distinct electric and magnetic dipole (ED and MD) resonances can be obtained by using femtosecond laser ablation and annealing. Significantly enhanced second harmonic generation and broadband HEIL are observed when the MD resonances of such GaAs NSs are resonantly excited. The lifetime of the HEIL is found to be as short as ∼82 ps, indicating a significant enhancement in radiative intraband transition rate. We reveal that the slope extracted from the dependence of the HEIL intensity on the irradiance is linearly proportional to the energy of the emitted photon. The existence of distinct ED and MD resonances in combination with a direct bandgap makes GaAs NSs an attractive candidate for constructing novel all-dielectric metamaterials and active photonic devices.
在等离子体热点中，电场显著增强会极大地增加光的线性和非线性吸收，从而产生高温电子气体，这些电子气体主要通过内带跃迁辐射宽带发光，这种发光与黑体辐射非常相似。在这里，我们证明通过利用砷化镓（GaAs）纳米球（NS）的磁偶极共振处的电场显著增强，也可以实现这种热电子内带发光（HEIL）。我们表明，通过使用飞秒激光烧蚀和退火，可以获得具有明显电偶极子（ED）和磁偶极子（MD）共振的单晶 GaAs NS。当共振激发这些 GaAs NS 的 MD 共振时，观察到二次谐波生成和宽带 HEIL 的显著增强。发现 HEIL 的寿命短至约 82 ps，表明辐射内带跃迁速率有显著增强。我们揭示了从 HEIL 强度对辐照度的依赖性中提取的斜率与发射光子的能量呈线性比例关系。ED 和 MD 共振的存在以及直接带隙使 GaAs NS 成为构建新型全电介质超材料和有源光子器件的有吸引力的候选材料。
