  Supercontinuum generation (SCG) is an important nonlinear optical process
enabling broadband light sources for many applications, for which silicon
nitride(Si3N4) has emerged as a leading on-chip platform.To achieve suitable
group velocity dispersion and high confinement for broadband SCG the Si3N4
waveguide layer used is typically thick (>~700 nm), which can lead to high
stress and cracks unless specialized processing steps are used. Here, we report
on efficient octave spanning SCG in a thinner moderate-confinement 400-nm Si3N4
platform using a highly nonlinear tellurium oxide (TeO2) coating. An
octave-spanning supercontinuum is achieved at a low peak power of 258 W using a
100-fs laser centered at 1565 nm. Our numerical simulations agree well with the
experimental results showing an increase of waveguide's nonlinear parameter by
a factor of 2.5 when coating the Si3N4 waveguide with TeO2 film. This work
demonstrates highly efficient SCG via effective dispersion engineering and an
enhanced nonlinearity in a CMOS-compatible hybrid TeO2-Si3N4 waveguides and a
promising route to monolithically integrated nonlinear, linear, and active
functionalities on a single silicon photonic chip.
