This interdisciplinary book covers the fundamentals of optical whispering gallery mode (WGM) microcavities, light-matter interaction, and biomolecular structure with a focus on applications in biosensing. Novel biosensors based on the hybridization of WGM microcavities and localized surface plasmon resonances (LSPRs) in metal nanoparticles have emerged as the most sensitive microsystem biodetection technology that boasts single molecule detection capability without the need for amplification and labeling of the analyte. The book provides an ample survey of the physical mechanisms of WGMs and LSPRs for detecting affinity, concentration, size, shape and orientation of biomarkers, while informing the reader about different classes of biomolecules, their optical properties and their importance in label-free clinical diagnostics. This expanded and updated second edition features a new chapter that introduces the reader to advanced in vivo biosensing techniques using WGM microcavities, looking at photothermal sensing, methods for trapping neutral atoms around WGM microcavities, and practical aspects of optoplasmonic sensing. The second Edition now provides a comprehensive introduction to the use of WGM microcavities in physical sensing which includes measurements with frequency combs, macro and micro (one atom) lasers, gyroscopes, optomechanical and parity-time-symmetric sensor devices. Chapterend problems round out this comprehensive and fundamental textbook, inspiring a host of upandcoming physicists, bioengineers, and medical professionals to make their own breakthroughs in this blossoming new field. This textbook can be used for both introductory and advanced courses about the modern optics of optical microcavities.

Frank Vollmer is Professor in Biophysics at the University of Exeter, UK. He obtained his PhD in physics and biology from the Rockefeller University in NYC, USA, in 2004. He was Rowland Fellow at Harvard University from 2004 to 2009, Scholar-in-Residence at the Wyss Institute at Harvard in 2010, Group Leader (untenured Associate Professor) at the Max Planck Institute for the Science of Light in Germany from 2011-2016 and Instructor in Medicine at Brigham and Women's Hospital/Harvard Medical School where he directed a satellite laboratory from 2011-2016. Since 2016 he is Professor in Biophysics at the School of Physics, University of Exeter, UK. He received the Royal Society Wolfson Research Merit Award in 2017 and in 2021 the Rosalind Franklin Medal and Prize from the Institute of Physics (IoP). Since 2021 he is Fellow of the IoP. Deshui Yu is Research Fellow at the University of Exeter. He received his B.Eng. degree in electronic science and technology from the Shandong University, China, in 2004 and PhD in radio physics from the Peking University, China, in 2009. He subsequently worked as a postdoctoral research fellow at the University of Tokyo from 2009 to 2012, the University of Nottingham from 2013 to 2014, and the National University of Singapore from 2015 to 2018. Currently, he is a postdoctoral researcher at the University of Exeter since 2019. His research mainly focuses on the quantum optics theory in quantum metrology and sensing and superconducting quantum circuits.