Spectral shaping of an ultrafast modelocked Ytterbium fiber laser output through a passive intracavity optical filter; a simple and reliable route to sub-45 fs pulses

Abstract: Here we investigate the use of passive intracavity optical filters for controlling the laser output spectrum of a polarization-mode-locked, ultrafast Ytterbium fiber laser. With strategic placement of the filter cutoff frequency, the overall lasing bandwidth can be increased or extended. Overall laser performance, including pulse compression and intensity noise, is investigated for both shortpass and longpass filters with a range of cutoff frequencies, tuned by rotating the filters. We demonstrate the use of an intracavity filter not only shapes the output spectra, it provides a route for overall broader bandwidths and shorter pulses in Yb:fiber lasers. These results demonstrate that spectral shaping is a useful tool to routinely achieve sub-45 fs pulse durations in Yb:fiber lasers.