Effects produced by metal-coated near-field probes on the performance of silicon waveguides and resonators

We study the effects of metal-coated fiber near-field probes on the performance of nanophotonic devices. Employing a heterodyne near-field scanning optical microscope and analyzing transmission characteristics, we find that a metal-coated probe can typically introduce a $3\mathrm{dB}$ intensity loss and a $0.2\mathrm{rad}$ phase shift during characterization of a straight waveguide made in a silicon-on-insulator system. In resonant nanophotonic structures such as a $5\mu \mathrm{m}$ radius microring resonator, we demonstrate that the probe induces a $1\mathrm{nm}$ shift in resonant wavelength and decreases the resonator quality factor, Q, from 1100 to 480.