Characterization of a photonic integrated Brillouin laser for 88Sr+ clocks

Silicon-nitride-based integrated photonic systems are a promising alternative to the bulky, free space optics typically used to create stable, narrow linewidth lasers in the visible range. Such lasers are necessary to drive optical transitions in atomic clocks, sensors, and quantum computers. In particular, laser frequency noise suppression by stimulated Brillouin scattering in silicon nitride integrated photonics at 674 nm has recently been demonstrated to be sufficient to generate the clock laser of a 88Sr+ optical atomic clock. Here, we demonstrate a direct drive photonic integrated Brillouin laser and characterize the stimulated Brillouin scattering threshold, the temperature and vibration sensitivity, and the stability and linewidth of the Stokes-shifted light using a frequency comb. We also discuss potential architectures for fully integrated optical clock lasers.