Broadband light management using low-Q whispering gallery modes in spherical nanoshells

• Yan Yao,
• Jie Yao,
• Vijay Kris Narasimhan,
• Zhichao Ruan,
• Chong Xie,
• Shanhui Fan
• & Yi Cui

• Affiliations
• Contributions
• Corresponding author

Nature Communications

 

3,

 

Article number:

 

664

 

doi:10.1038/ncomms1664

Received

 

28 July 2011 

Accepted

 

03 January 2012 

Published

 

07 February 2012

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.