Precision optical-frequency and phase synchronization over fibre is critical for a variety of applications, from timekeeping to quantum optics. Such applications utilize ultra-coherent sources based on stabilized table-top laser systems. Chip-scale versions of these systems may dramatically broaden the application landscape by reducing the cost, size and power of such exquisite sources. Links based on the required narrow-linewidth integrated lasers, compact reference cavities and control methodologies have not yet been presented. Here, we demonstrate an optically synchronized link that achieves an ultralow residual phase error variance of 3 × 10−4 rad2 at the receiver, using chip-scale stabilized lasers with laser linewidth of ~30 Hz and instability below 2 × 10−13 at 50 ms. This performance is made possible with integrated Brillouin lasers, compact reference cavities and a novel low-bandwidth optical-frequency-stabilized phase-locked loop. These results demonstrate a path towards low-power, precision applications including distributed atomic clocks, quantum links, database synchronization and digital-signal-processor-free coherent fibre interconnects.
Bibliographical noteFunding Information:
This research was supported by the OPEN 2018 Advanced Research Projects Agency– Energy (ARPA-E), US Department of Energy, under award no. DE-AR0001042. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing official policies of ARPA-E or the US Government.
© 2021, The Author(s), under exclusive licence to Springer Nature Limited.