  We demonstrate a novel approach to producing coherent, directional
supercontinuum via cascaded dispersive wave generation. By pumping in the
normal group-velocity dispersion regime, pulse compression of the first
dispersive wave results in the generation of a second dispersive wave,
resulting in an octave-spanning supercontinuum generated primarily to one side
of the pump spectrum. We theoretically investigate the dynamics and show that
the generated spectrum is highly coherent. We experimentally confirm this
dynamical behavior and the coherence properties in silicon nitride waveguides
by performing direct detection of the carrier-envelope-offset frequency of our
femtosecond pump source using an f-2f interferometer. Our technique offers a
path towards a stabilized, high-power, integrated supercontinuum source with
low noise and high coherence, with applications including direct comb
spectroscopy.
