Laser frequency offset locking at 10-Hz-level instability using hybrid electronic filters

TL;DR

This paper introduces a laser frequency offset locking technique using hybrid electronic filters, achieving high stability and wide tuning range, suitable for precise scientific applications.

Contribution

The paper presents a novel offset locking method with hybrid electronic LC filters that decouples lock tightness from capture range, outperforming previous beat frequency discrimination methods.

Findings

Achieved <55 Hz frequency instability over 1000 s

Demonstrated 12 Hz minimum instability at 10 s

Provided a 190 MHz capture range and 1 GHz tuning range

Abstract

Lasers with well controlled relative frequencies are indispensable for many applications in science and technology. We present a frequency offset locking method for lasers based on beat frequency discrimination utilizing hybrid electronic LC filters. The method is specifically designed for decoupling the tightness of the lock from the broadness of its capture range. The presented demonstration locks two free running diode lasers at 780 nm with a 5.5 GHz offset. It displays an offset frequency instability below 55 Hz for timescales in excess of 1000 s and a minimum of 12 Hz at 10 s averaging, outperforming the best reported instabilities of methods based on beat frequency discrimination. The performance is complemented with a 190 MHz lock capture range, a tuning range of up to 1 GHz, and a frequency ramp agility of 200 kHz/$\mu$s.