Abstract: Microtoroid optical resonators, when combined with frequency locking, balanced detection, and data processing techniques, are capable of label-free single molecule detection at attomolar concentrations in under 30 seconds. We have developed such a system called FLOWER (frequency locked optical whispering evanescent resonator). We discuss the principles of FLOWER, including noise analysis, and how, at such low concentrations, we can achieve sensing times on the order of seconds. In addition, we discuss our ongoing work on using FLOWER for fundamental studies on taste, and a variety of applications including drug screening, medical diagnostics for ovarian cancer, and chemical threat sensing. We validate our technology against existing approaches and perform detection in complex biological fluids. Finally, we discuss our next generation sensing platforms, including how we combine FLOWER with frequency comb technology to enable simultaneous detection and absorption spectroscopy, our work on high sensitivity photothermal spectroscopy, and our work towards a robust, portable, translatable device. 

Bio: Judith Su is an Assistant Professor in Biomedical Engineering and an Assistant Professor in Optical Sciences at the University of Arizona. Judith received her B.S. and M.S. from MIT in Mechanical Engineering and her Ph.D. from Caltech in Biochemistry & Molecular Biophysics. Her background is in sensing, imaging, microfabrication, and optical instrument building for biological and medical applications. She is a recipient of an NIH R35 Outstanding Investigator Award and an American Society of Laser Surgery and Medicine Young Investigator Award. She was a Siegman International School on Lasers Lecturer and a Scialog: Chemical Machinery of the Cell Fellow. She is on the Board of Scientific Counselors for the National Institute for Occupational Safety and Health (NIOSH). She gave a keynote talk at SPIE Photonics West 2022 and is an incoming general chair for OSA’s 2023 Advanced Photonics Congress, Integrated Photonics Research (IPR) Conference.