  The acousto-optic interaction known as stimulated Brillouin scattering (SBS)
has emerged as fundamental principles for realizing crucial components and
functionalities in integrated photonics. However, the main challenge of
integrated Brillouin devices is how to effectively confine both optical and
acoustic waves. Apart from that, the manufacturing processes for these devices
need to be compatible with standard fabrication platforms, and streamlined to
facilitate their large-scale integration. Here, we demonstrate a novel
suspended nanowire structure that can tightly confine photons and phonons.
Furthermore, tailored for this structure, we introduce a loading-effect-based
three-dimensional microfabrication technique, compatible with complementary
metal-oxide-semiconductor (CMOS) technology. This innovative technique allows
for the fabrication of the entire structure using a single-step lithography
exposure, significantly streamlining the fabrication process. Leveraging this
structure and fabrication scheme, we have achieved a Brillouin gain coefficient
of 1100 1/W/m on the silicon-on-insulator platform within a compact footprint.
It can support a Brillouin net gain over 4.1 dB with modest pump powers. We
believe that this structure can significantly advance the development of SBS on
chip, unlocking new opportunities for the large-scale integration of
Brillouin-based photonic devices.
