Whispering Gallery Mode (WGM) microresonators are a class of optical sensors that have demonstrated enormous potential for the detection of single molecules and nano-particles. WGM based sensors can also detect a wide range of physical phenomenon such as magnetic and electric fields, temperature, and ultrasonic waves. Briefly, light is coupled into the resonator structure with an external waveguide. Under specific optical resonance conditions, light is trapped within the sensor, leading to an enormous signal amplification. Any localized change to the resonator (such as the binding of a biomolecule or changes in refractive index), changes the local optical environment, therefore changing the location of the resonant peak. By monitoring the change in resonance wavelength, we can quantitatively measure the amount of an analyte in real-time.
WGM microresonators come in a variety of geometries. Common geometries include, but are not limited to, microtoroids, microrings, and microbubble resonators (MBR). The key advantage of a MBR is fluidic integration. In this geometry, the inline capillary can be used to easily deliver small volumes (i.e., nL) of analytes in solution to the sensing area without the need to integrate external fluidic channels. MBRs, having unique fluidic handling capabilities, are well suited for several different sensing applications that are not easily achievable with other WGM platforms.
Although the whispering gallery mode microbubble resonator has been shown in a plethora of applications, there are still some roadblocks to bringing this sensor from the lab bench and out into the field. My research focuses on the optimization and applications of the whispering gallery mode microbubble resonators. Concentrating on improved fabrication and packaging methods to increase reproducibility and robustness of the devices. I’ll also show a method of “Reverse Tuning” the WGM field to get around the use of expensive and bulky tunable diode lasers, enabling the use of cheaper single wavelength sources. This research will conclude by showing a few novel applications of the platform for applications in bio-molecule sensing and pH sensing.
Washington University in St. Louis
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