Abstract

The transfer of the optical phase of a highly coherent master laser to a noisier slave laser by means of an optical phase-locked-loop is of great interest in many applications, from frequency transfer across long-haul fiber networks [1] to ultra-high resolution spectroscopy [2]. The control bandwidth of those loops seldom exceeds the limit of few MHz set by the frequency modulation response of the slave laser and by the propagation delay within the servo loop. Such limit is shown here to be straightforwardly brought to the hundreds of MHz level by use of a dual-parallel Mach-Zehnder modulator (MZM) operated as a single-sideband generator in a feed-forward control scheme [3]. The approach allows both cloning of the optical phase of the master oscillator with minimal residual phase error and fine tunability of the cloned laser by up to 40 GHz.

© 2015 IEEE