SF Bay Area Nanotechnology Council


Archive for August, 2012

Broadband Light Management Using Low-Q Whispering Gallery Modes in Spherical Nanoshells

Sunday, August 5th, 2012
  August 21, 2012 Noon-1PM Texas Instruments Auditorium E-1 2900 Semiconductor Drive. Santa Clara, CA       TITLE: Broadband light management using low-Q whispering gallery modes in spherical nanoshells SPEAKER: Jie Yao, Post-doctoral Researcher, Materials Science and Engineering, Stanford   ABSTRACT: Light trapping across a wide band of frequencies is important for applications such as solar cells and photodetectors. Here, we demonstrate a new approach to light management by forming whispering-gallery resonant modes inside a spherical nanoshell structure. The geometry of the structure gives rise to a low quality-factor, facilitating the coupling of light into the resonant modes and substantial enhancement of the light path in the active material, thus dramatically improving absorption. Using nanocrystalline silicon (nc-Si) as a model system, we observe broadband absorption enhancement across a large range of incident angles. The absorption of a single layer of 50-nm-thick spherical nanoshells is equivalent to a 1-μm-thick planar nc-Si film. This light-trapping structure could enable the manufacturing of high-throughput ultra-thin film absorbers in a variety of material systems that demand shorter deposition time, less material usage and transferability to flexible substrates. SPEAKER BIO: Dr. Jie Yao is a Post-doctoral Researcher in the Materials Science and Engineering Department at Stanford University. He works within the group of Professor Yi Cui which investigates a broad range of nanoscale properties including electronic, photonic, electrochemical, mechanical, catalytic and interfacial properties. His research interests include light management for energy conversion, material optical property tuning, metamaterials and optical nano-cavities. He has demonstrated non-resonant negative refraction in metamaterials, which is a milestone in the exploration of transformational optics. He also designed and demonstrated the world’s smallest three-dimensional indefinite optical cavities. He completed his PhD at UC Berkeley, his MS at the University of Southern California and BS at Nanjing University, China. AGENDA: Registration & light lunch 11:30am. Presentation & Q/A 12:00 to 1pm COST: IEEE Members and Students $5. Non-Members $10