Knight, J., Dubreuil, N., Sandoghdar, V., Hare, J., LefevreSeguin, V., Raimond, J., et al. (1996).
Characterizing whispering-gallery modes in microspheres by direct observation of the optical standing-wave pattern in the
near field. Optics Letters, 21, 698-700. doi:10.1364/OL.21.000698.