  We describe the generation of stable mode-locked pulse trains from on-chip
normal dispersion microresonators. The excitation of hyper-parametric
oscillation is facilitated by the local dispersion disruptions induced by mode
interactions. The system is then driven from hyper-parametric oscillation to
the mode-locked state with over 200 nm spectral width by controlled pump power
and detuning. With the continuous-wave driven nonlinearity, the pulses sit on a
pedestal, akin to a cavity soliton. We identify the importance of pump detuning
and wavelength-dependent quality factors in stabilizing and shaping the pulse
structure, to achieve a single pulse inside the cavity. We examine the mode
locking dynamics by numerically solving the master equation and provide
analytic solutions under appropriate approximations.
