A Flexible All-Digital Transfer Beat Implementation for Precision Frequency Metrology

SummaryUsing a frequency comb as a transfer oscillator, ‘virtual’ or ‘transfer’ beats between widely separated optical frequencies can be created. These real-time beats between a frequency and a rational fraction of a second optical frequency can be employed for comparing or phase-locking lasers, independent of fluctuations of the frequency comb. We demonstrate an all-digital FPGA-based implementation for the creation of a transfer beat which is simple to scale and can be reconfigured with high flexibility. The noise performance of this all-digital transfer beat implementation is at least on par with its analogue counterpart.