Comparison of two low-noise CEO frequency stabilization methods for an all-PM Yb:fiber NALM oscillator

Sarper Salman,Ingmar Hartl,Stefan Droste,Philip Pfäfflein,Christoph Mahnke,Oliver H Heckl,Thomas Südmeyer,Kutan Gürel,Stéphane Schilt,Aline S Mayer,Jakob Fellinger,Christoph M Heyl,Yuxuan Ma,Chen Li

doi:10.1364/osac.424340

Abstract

We present a comparison of two low-noise carrier-envelope offset (CEO) frequency stabilization methods studied using an ytterbium (Yb) fiber laser oscillator based on a nonlinear amplifying loop mirror. We first investigate the phase locking performance achieved with cross-gain modulation (XGM) via injection of an auxiliary low-power continuous-wave (CW) laser into the fiber gain medium. Amplification of the injected CW laser light cross-modulates the gain of the oscillator, resulting in an intra-cavity power modulation, thus providing control of the CEO frequency. The XGM method is then compared with the conventional pump-current modulation scheme. Both stabilization methods provide similar locking performances with sub-200-mrad of integrated residual carrier-envelope-phase (CEP) noise (10 Hz to 1 MHz), suitable for high-resolution comb spectroscopy applications.

Highlights

Over the last two decades we have witnessed a rapid advance in optical frequency comb technology
We present a comparison of two low-noise carrier-envelope offset (CEO) frequency stabilization methods studied using an ytterbium (Yb) fiber laser oscillator based on a nonlinear amplifying loop mirror
Amplification of the injected CW laser light cross-modulates the gain of the oscillator, resulting in an intra-cavity power modulation, providing control of the CEO frequency

Summary

Introduction

Over the last two decades we have witnessed a rapid advance in optical frequency comb technology. A more recent approach for f ceo stabilization relies on modulating the laser gain medium using an auxiliary laser Employing this scheme for an Er:Yb:glass diode-pumped solid-state laser (SESAM mode-locked, 100 MHz repetition rate), Karlen et al [24] demonstrated 120 mrad integrated phase noise (1 Hz to 1 MHz). Gürel et al [25] employed a similar cross-gain modulation (XGM) method for f ceo stabilization of a fiber laser (NPE mode-locked, 125 MHz repetition rate) reaching a 400-kHz modulation bandwidth using a low-power (< 1 mW) auxiliary CW laser, surpassing the locking performance achieved using the pump-modulation method. We compare the XGM method with the traditional pump modulation approach With both methods, sub-200-mrad integrated phase noise (10 Hz to 1 MHz) was achieved, enabling high-coherence frequency comb applications

Experimental setup

Experiments and results

Conclusion