160W single-frequency laser based on active tapered double-clad fiber amplifier

Abstract

Summary form only given. The main factor limiting the output power of fiber lasers is the influence of nonlinear effects: stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS), etc. To obtain high power densities, it is proposed to sum coherently radiations from several sources. To this end, it is necessary to develop and implement a high-power single-frequency master oscillator, providing a sufficient coherence length. A generally accepted approach is to use a narrow-band master oscillator and several cascades of fiber amplifiers. In this study, we present a two stage high-power amplifier using ytterbium-doped GTWave fiber in the first stage and tapered ytterbium-doped fiber concept in the second stage. The T-DCF approach takes advantage of the large mode volume combined with good beam quality and utilizes cost-effective low-brightness end pumping. Furthermore, variation of the core diameter in the tapered fiber offers an efficient mechanism for SBS mitigation, and the non-reciprocity of the tapered structure results in increased losses for counter-propagating ASE due to the vignetting effect, improving the amplifier performance for forward signal.