Proceedings Article | 11 October 2013
Proc. SPIE. 8915, Photonics North 2013
KEYWORDS: Refractive index, Microresonators, Biosensing, Optical spheres, Resonators, Sensors, Molecules, Structured optical fibers, In vivo imaging, Micro optical fluidics
Whispering Gallery Modes (WGMs) have been widely studied for the past 20 years for various applications, including
biological sensing. While the different WGM-based sensing approaches reported in the literature enable useful sensor
characteristics, at present this technology is not yet mature, mainly for practical reasons. Our work has been focused on
developing a simple, yet efficient, WGM-based sensing platform capable of being used as a dip sensor for in-vivo
biosensing applications.
We recently demonstrated that a dye-doped polymer microresonator, supporting WGMs, positioned onto the tip of a
suspended core Microstructured Optical Fiber can be used as a dip sensor. In this architecture, the resonator is located
on an air hole next to the fiber core at the fiber’s tip, enabling a significant portion of the sphere to overlap with the
guided light emerging from the fiber tip. This architecture offers significant benefits that have never been reported in
the literature in terms of radiation efficiency, compared to the standard freestanding resonators, which arise from
breaking the symmetry of the resonator. In addition to providing the remote excitation and collection of the WGMs'
signal, the fiber also allows easy manipulation of the microresonator and the use this sensor in a dip sensing
architecture, alleviating the need for a complex microfluidic interface.
Here, we present our recent results on the microstructured fiber tip WGM-based sensor, including its lasing behavior
and enhancement of the radiation efficiency as a function of the position of the resonator on the fiber tip. We also show
that this platform can be used for clinical diagnostics and applying this technology to the detection of Troponin T, an
acute myocardial infarction biomarker, down to a concentration of 7.4 pg/mL.
