A widely tunable laser frequency offset lock with digital counting

TL;DR

This paper presents a hybrid analog-digital electronic lock that stabilizes and tunes the frequency offset between two lasers over a wide range with high agility and low drift, suitable for laser cooling and trapping.

Contribution

It introduces a novel hybrid locking scheme with wide capture and tuning ranges, high frequency agility, and low drift, enabling precise referencing of multiple lasers to a stable master.

Findings

80 MHz capture range achieved

+/- 7 GHz tuning range demonstrated

Frequency drift less than 30 ppm over 1000 seconds

Abstract

We demonstrate a hybrid analog+digital electronic lock to stabilize a dynamically tunable rf offset between two lasers. Our method features an 80 MHz capture range, +/- 7 GHz tuning range, frequency agility of 1 MHz/microsecond, and low (<30 ppm) drift in the absolute optical frequency difference after ~1000 s. With this scheme, multiple slave lasers can easily be referenced to one stable master laser, while each remains rapidly and accurately tunable over the wide frequency ranges encountered in typical laser cooling and trapping experiments.