  The realization of ultrahigh quality (Q) resonators regardless of the
underpinning material platforms has been a ceaseless pursuit, because the high
Q resonators provide an extreme environment of storage of light to enable
observations of many unconventional nonlinear optical phenomenon with high
efficiencies. Here, we demonstrate an ultra-high Q factor (7.1*10^6)
microresonator on the 4H-silicon-carbide-on-insulator (4H-SiCOI) platform in
which both \c{hi}^(2) and \c{hi}^(3) nonlinear processes of high efficiencies
have been generated. Broadband frequency conversions, including second-,
third-, fourth-harmonic generation were observed. Cascaded Raman lasing was
demonstrated in the SiC microresonator for the first time to the best of our
knowledge. Broadband Kerr frequency combs covering from 1300 to 1700 nm were
achieved using a dispersion-engineered SiC microresonator. Our demonstration is
a significant milestone in the development of SiC photonic integrated devices.
