  Fiber based whispering-gallery-mode (WGM) microprobe, combining both the high
optical field enhancement of the WGMs and the practicability of the fiber
probe, is highly demanded in sensing and imaging. Here in this paper, we
experimentally report the efficient far-field coupling of WGMs by scattering
the focused laser beam through a nanotip. With the help of Purcell effect as
well as the two-step focusing technique, a WGM excitation efficiency as high as
16.8% has been achieved. Both the input and output of the probe light propagate
along the same fiber, which makes the whole coupling system a fiber based WGM
microprobe for sensing/imaging applications.
