1 Introduction

2 Whispering Gallery Mode Resonators

2.1 Quality factor of a whispering gallery mode

3 Different Types of Whispering Gallery Mode Resonators

3.1 Microring and microdisk resonators

3.2 Microtoroid resonators

3.3 Microsphere resonators

3.4 Microcapillary resonators

3.5 Microbottle and microbubble resonators

4 Sensing Principles

4.1 Reactive shift

4.2 Mode splitting and line broadening

5 Whispering Gallery Mode Resonator Sensors: Applications

5.1 Sensing of physical parameters

5.2 Gas and biological sensors

6 Conclusions and Outlook

7 Acknowledgments

References

Preface

Whispering gallery mode (WGM) resonators have enabled real-world sensing applications by measuring physical quantities, such as temperature, mass, and pressure, as well as chemical and biomedical parameters. In the latter context, important achievements, such as label-free detection of a single virus, single molecules, and large objects, such as bacteria, have been recorded. We try to provide a quick overview of the state of the art of WGM-based sensors. A summary of the fundamental principles, the mathematical theory, and the main properties of different types of such resonators is also given.

Giancarlo C. Righini
Silvia Soria
March 2017