Reverse Tuning of Whispering Gallery Mode Microresonators

WGM sensors are a class of optical sensors in which light is tightly confined due to optical resonance within a circular geometry. Expensive tunable diode lasers are typically used to excite resonance in a WGM device, which can be a cost limiting factor in developing economies. Herein, we developed a “reverse tuning” method that eliminates the need for such expensive laser sources. We show the microbubble resonator (MBR), a sub class of WGM devices, is ideally suited for the reverse tuning method by tuning with temperature, pressure and refractive index changes. Reducing the cost of the MBR platform, by utilizing less expensive laser sources with fixed wavelength, increases the practicality of these devices for use in low resource settings. We expect our methods to reduce the total cost of the sensing platform from thousands to a few hundred dollars.