New Strategy to Develop a Plasmonic Nanocavity Array for Second-Harmonic Generation
Plasmonic nanostructures are a type of metallic materials, which have attracted a lot of interest for decades. By localizing electromagnetic fields into volumes at subwavelength scales, they exhibit unique optical properties to manipulate linear and nonlinear optical processes.
As described as localized surface plasmon resonances (LSPR), the great enhancement of localized electromagnetic fields obtained in plasmonic nanostructures provides great opportunities for improved applications in ultrasensitive detection, light harvest and generation and optical forces.
Nonlinear optical processes arise from the broken-symmetry induced intrinsic nonlinearities on metal surface also benefit from the near-field enhancement of SPR, giving rise to the new research field called nonlinear plasmonics.
Recently, a research team led by Profs. LIU Xinfeng andZHANG Yong from the National Center for Nanoscience and Technology (NCNST) of the Chinese Academy of Sciences (CAS), reported a new strategy to develop inch-scale polarization-independent plasmonic nanocavity array for second-harmonic generation. The research was published on ACS Nano.
In this work, a solution-processed method instead of traditional high-cost processes was employed to fabricate the inch-scale second-harmonic generation (SHG) source. By assembling gold nanoparticles with porous anodic alumina templates, multi-resonance can be achieved in hexagonal plasmonic nanostructure arrays. Multi-resonance modes provide strong electric field enhancement at the gap region in both visible and near-infrared regions.
Owing to the in-plane isotropic characteristic of assembled unit, polarization-independence SHG radiation can been realized. The tilt-angle dependent and angle-resolved measurement also showed that wide-angle nonlinear response is achieved in this plasmonic nanostructure array. Because the gap geometry of ball-in-bowl nanostructure with nonlinear emission electric dipoles distributed on the concave surface. Wide-angle nonlinear response makes the plasmonic nanostructure array competitive in practical applications.
Collectively, this study not only makes it possible to produce uniform inch-scale nonlinear arrays through low-cost solution process; and also advances the understanding of the SHG radiation in plasmonic nanostructures.
The research is supported by Strategic Priority Research Program of Chinese Academy of Sciences, the Ministry of Science and Technology, National Natural Science Foundation of China, and Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum physics.
Figure: Schematic and characteristics of second harmonic generation in the plasmonic nanostructure array samples.
National Center for Nanoscience and Technology