  Optical parametric oscillation (OPO) with far-shifted frequency sidebands has
attracted significant interests in precision spectroscopy and quantum
information processing. Microresonator based OPO sources hold the advantages of
miniaturized footprint and versatile dispersion engineering. Here we
demonstrate large-frequency-shifted $\chi^{(3)}$-based OPO from crystalline
aluminum nitride microrings pumped at $\sim$2 $\mu$m in the normal dispersion
regime. OPO in the telecom and mid-infrared bands with a frequency separation
of 65.5 THz is achieved. The OPO frequency can be agilely tuned in the ranges
of 10, 1 and 0.1 THz respectively by tailoring the microring dimensions,
shifting the pump wavelength, and controlling the chip temperature. At high
intracavity pump powers, the OPO sidebands further evolve into localized
frequency comb lines. Such telecom to mid-infrared OPO with flexible wavelength
tunability will lead to enhanced chip-scale light sources.
