Study of Nonlinear Plasmonic Scattering in Metallic Nanoparticles

Nonlinear optical effects play key roles to communication, sensing, imaging, and so on. Recently, nonlinear scattering (saturation and reverse saturation) was discovered in gold nanospheres, providing a novel approach to nonbleaching super-resolution microscopy. However, the nonlinearity was previously limited to green-orange plasmonic band. It is highly desirable to extend the applicable wavelength range. In this work, we demonstrated nonlinear scattering in near-infrared with gold nanorods and in blue-violet with silver nanospheres. Besides, the nonlinear mechanism is clarified via different material/geometry. By spectrally decoupling the contributions of plasmonic absorption/scattering and interband/intraband transitions, we have verified plasmonic absorption, and the subsequent thermal effects to be the dominating source of nonlinearity. Our work not only provides the physical mechanism of the nonlinear scattering, but also paves the way toward multicolor super-resolution imaging based on plasmonic scattering.