  We discuss experimental studies of the interaction between a nanoscopic
object and a photonic crystal membrane resonator of quality factor Q=55000. By
controlled actuation of a glass fiber tip in the near-field of a photonic
crystal, we constructed a complete spatio-spectral map of the resonator mode
and its coupling with the fiber-tip. On the one hand, our findings demonstrate
that scanning probes can profoundly influence the optical characteristics and
the near-field images of photonic devices. On the other hand, we show that the
introduction of a nanoscopic object provides a low-loss method for on-command
tuning of a photonic crystal resonator frequency. Our results are in a very
good agreement with the predictions of a combined numerical/analytical theory.
