  Fully integrated supercontinuum sources on-chip are critical to enabling
applications such as portable and mechanically-stable medical imaging devices,
chemical sensing and LiDAR. However, the low-efficiency of current
supercontinuum generation schemes prevent full on-chip integration. In this
letter, we present a scheme where the input energy requirements for integrated
supercontinuum generation is drastically lowered by orders of magnitude, for
bandwidth generation of the order of 500 to 1000 nm. Through sign-alternating
the dispersion in a CMOS compatible silicon nitride waveguide, we achieve an
efficiency enhancement by factors reaching 3800. We show that the pulse energy
requirement for large bandwidth supercontinuum generation at high spectral
energy (e.g., 1/e level) is lowered from nanojoules to 6 picojoules. The
lowered pulse energy requirements enables that chip-integrated laser sources,
such as mode-locked heterogeneously or hybrid integrated diode lasers, can be
used as a pump source, enabling fully integrated on-chip high-bandwidth
supercontinuum sources.
