  Real-time characterization of microresonator dynamics is important for many
applications. In particular it is critical for near-field sensing and
understanding light-matter interactions. Here, we report camera-facilitated
imaging and analysis of standing wave patterns in optical ring resonators. The
standing wave pattern is generated through bi-directional pumping of a
microresonator and the scattered light from the microresonator is collected by
a short-wave infrared (SWIR) camera. The recorded scattering patterns are
wavelength dependent, and the scattered intensity exhibits a linear relation
with the circulating power within the microresonator. By modulating the
relative phase between the two pump waves, we can control the generated
standing waves movements and characterize the resonator with the SWIR camera.
The visualized standing wave enables subwavelength distance measurements of
scattering targets with nanometer-level accuracy. This work opens new avenues
for applications in on-chip near-field (bio-)sensing, real time
characterization of photonic integrated circuits and backscattering control in
telecom systems.
