  Stimulated Brillouin scattering (SBS), a coherent nonlinear effect coupling
acoustics and optics, can be used in a wide range of applications such as
Brillouin lasers and tunable narrowband RF filtering. Wide adoption of such
technologies however, would need a balance of strong Brillouin interaction and
low optical loss in a structure compatible with large scale fabrication.
Achieving these characteristics in scalable platforms such as silicon and
silicon nitride remains a challenge. Here, we investigate a scalable Brillouin
platform combining low loss Si$_3$N$_4$ and tellurium oxide (TeO$_2$)
exhibiting strong Brillouin response and enhanced acoustic confinement. In this
platform we measure a Brillouin gain coefficient of 8.5~m$^{-1}$W$^{-1}$,
exhibiting a twenty fold improvement over the largest previously reported
Brillouin gain in a Si$_3$N$_4$ platform. Further, we demonstrate cladding
engineering to control the strength of the Brillouin interaction. We utilized
the Brillouin gain and loss resonances in this waveguide for an RF photonic
filter with more than 15 dB rejection and 250 MHz linewidth. Finally, we
present a pathway by geometric optimization and cladding engineering to a
further enhancement of the gain coefficient to 155~m$^{-1}$W$^{-1}$, a
potential 400 times increase in the Brillouin gain coefficient.
