Spatial refractive index sensor using whispering gallery modes in an optically trapped microsphere

P. Zijlstra, Peter Zijlstra, K.L. van der Molen, Allard Mosk

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The authors propose the use of an optically trapped, dye doped polystyrene microsphere for spatial probing of the refractive index at any position in a fluid. Using the dye embedded in the microsphere as an internal broadband excitation source the authors eliminated the need for a tunable excitation source. They measured the full width at half maximum and frequency spacing of the transverse electric and transverse magnetic resonances as a function of the refractive index of the immersion fluid. The authors achieved a sensitivity of 5×10−4 in refractive index, even when the exact size of the microsphere was not known.
Original languageUndefined
Pages (from-to)1-3
Number of pages3
JournalApplied physics letters
Issue number161101
Publication statusPublished - 2007


  • IR-74694
  • METIS-239793

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