Plasmonics and Metamaterials for Extreme Light Manipulation

Plasmonics has become a very important branch in nano optics, focusing on the new physical phenomena and exciting applications associated with metallic nanostructures. Plasmonics allows us to concentrate, guide, and manipulate light at the deep subwavelength scale, promising enhanced light-matter interaction, sub-diffraction-limited imaging, efficient solar energy harvesting, and ultrasensitive biomedical detection. Furthermore, the assembly of metallic nanostructures can be used to construct optical metamaterials with exotic properties and functionalities, including artificial magnetism, negative refraction, and invisibility cloak.

In this talk, after the introduction of plasmonics and metamaterials, I will present some of my recent work on extreme light manipulation utilizing the two schemes. First, I will describe the design and demonstration of the first optical negative refraction in bulk metamaterials made of metallic nanowires, which exhibit low-loss, broad-band and all-angle advantages. Second, I will introduce a new concept of transformation plasmonics to mold near-field plasmon waves at the metal-dielectric interface in a prescribed manner. For instance, this approach enables surface plasmon waves to travel smoothly at uneven surfaces, where surface plasmons would normally suffer considerable scattering losses. Some plasmonic devices, such as a plasmonic bend and a plasmonic Luneburg lens, will also be presented. Finally, I will demonstrate a fully subwavelength and efficient nano-plasmonic source for unidirectional generation of surface plasmons, which is a key building block for the next generation of ultra-fast and ultra-compact integrated optical circuits. By tailoring the relative phase at resonance and the separation between two magnetic metamaterial resonators, surface plasmons can be steered to predominantly propagate along one specific direction. Such a device not only serves as a highly directional surface plasmon generator, but also could be useful for surface-plasmon-based nonlinear applications, active modulation and wireless communication.

Biography:
Yongmin Liu is currently a postdoctoral fellow at the University of California, Berkeley. He received his Ph.D. from UC-Berkeley in 2009, under the supervision of Prof. Xiang Zhang. Dr. Liu’s research interests include nano optics, nanoscale materials physics and engineering, interaction of light and composite media, nano optomechanics, biophotonics, near field optics and imaging. Part of his research findings have been published in leading journals such as Science, Nature, Nature Nanotechnology, Nature Communications, Physical Review Letters and Nano Letters. Dr. Liu’s recent honors include Chinese Government Award for Outstanding Students Abroad (2009), International Society for Optical Engineering (SPIE) Scholarship Award (2008), and Tse-Wei Liu Memorial Fellowship at UC-Berkeley (2008).