Heterodyne-based hybrid controller for wide dynamic range optoelectronic frequency synthesis

Chip scale optical frequency combs using microresonators can enable a wide variety of applications from metrology to telecommunications. While tremendous progress has been made in miniaturizing the optical components, sources of variability and drift due to ambient conditions often limit their performance. We describe the design and implementation of a mixed-signal controller for optoelectronic frequency synthesis with notable frequency stability by locking it to an RF reference. A C-band tunable laser is phase-locked using commercial off the shelf components and custom board-level designs. Utilizing several laser inputs, our hybrid control loop enables a 50 nm tuning range with less than 10 12 frequency instability for 1 second averaging. A heterodyne receiver overcomes poor SNR of the photonics, and also features a scan-and-lock algorithm to facilitate an extended acquisition range. We report > 500 GHz frequency steps in 4.4 ms. All of the frequency settings and loop stability dynamics are programmable in real-time via a custom Graphical User Interface. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement