Whispering-Gallery Microresonators and Microlasers for Nanoscale Sensing: A New Technology for Aerosol Science
About the Presenter:
Lan Yang is the Edwin H. and Florence G. Skinner professor in the Preston M. Green Department of Electrical and Systems Engineering at Washington University. She received her Ph.D. in applied physics from Caltech in 2005. Her current research interests include novel photonic materials and nano/micro photonic devices for energy, biomedical research, optical communication, environmental monitoring and sensing. She received NSF CAREER Award in 2010 for her work on single nanoparticle detection and sizing using an on-chip optical resonator for the first time. She is also the recipient of the 2010 Presidential Early Career Award for Scientists and Engineers (PECASE).
Optical sensors based on Whispering-Gallery-Mode (WGM) resonators have emerged as front-runners for label-free, ultra-sensitive detection of nanoscale materials and structures due to their superior capability to significantly enhance the interactions of light with the sensing targets. A WGM resonator traps light in circular orbits in a way similar to a whisper, i.e., a sound wave, traveling along a circular wall, an effect found in the whispering gallery of St. Paul’s Cathedral in London. The basis for resonator sensors is that the physical associations and interactions of nanomaterials on the surface of a high-Q optical WGM resonator alter the trajectory and lifetime of photons in a way that can be measured and quantified. I will first present a laser-assisted processing method to create Si-chip based optical WGM microresonators with Q-factors in excess of 100 million. I will then present a recent discovery of using ultra-high-Q microresonators and microlasers for ultra-sensitive self-referencing detection and sizing of single virion, dielectric and metallic nanoparticles. A case study of characterization of hygroscopic growth of aerosol particles using the new technology will be presented. I will also discuss using optical gains in a microlaser to improve the detection limit beyond the reach of a passive microresonator. These recent advancements in WGM microresonators will enable a new class of ultra-sensitive and low-power sensors for investigating the properties and kinetic behaviors of nanomaterials, nanostructures, and nanoscale phenomena. It will provide a new route to study and analyze chemical and physical properties of aerosols.