Brillouin-based radio frequency sources

High frequency, low-noise RF sources are of great importance for fundamental science as well as many applications ranging from sensing to communications and RADAR to name a few. This chapter describes the chronological development of radiofrequency sources harnessing photonics and highlights the role Brillouin scattering played in their evolution, starting with fiber-based approaches toward small footprint chip-based schemes. We will provide key performance metrics to provide the reader with enough context to follow the discussion and comparisons of the different schemes. At the end of the chapter, we give a perspective on current trends and future directions.