We report an integrated whispering gallery mode microresonator-based sensor probe for refractive index sensing. The probe was made by sealing a borosilicate glass microsphere into a thin-wall glass capillary pigtailed with a multimode optical fiber. The intensities of the resonant peaks were found decreasing exponentially (linearly in a log scale) with the increasing refractive index of the medium surrounding the capillary. The sensing capability of the integrated probe was tested using sucrose solutions of different concentrations and the resolution was estimated to be about 2.5 x 10-5 in the index range of 1.3458 to 1.3847. The integrated sensor probe may prove useful in many chemical and biological sensing applications where highly sensitive refractive index monitoring is needed.


Nuclear Engineering and Radiation Science

Second Department

Electrical and Computer Engineering


National Institutes of Health (U.S.)


This material was based upon work supported by NIH under contract R21GM104696.

Keywords and Phrases

Borosilicate glass; Microspheres; Multimode fibers; Optical fibers; Optical resonators; Probes; Refractive index; Refractometers; Thin walled structures; Chemical and biological sensing; Glass capillaries; Integrated sensors; Multimode optical fibers; Refractive index measurement; Refractive index sensing; Refractive index sensor; Thin walls; Whispering gallery modes; Thin wall capillary

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

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© 2016 SPIE, All rights reserved.

Publication Date

01 Jun 2016