Wavelength-stabilized figure-of-9 thulium-doped all-fiber laser emitting 560 fs pulses

Abstract We demonstrate a figure-of-9 all-fiber thulium-doped laser (TDFL) that generates 560 fs long pulses at 1948 nm wavelength. In order to achieve self-starting passive mode-locking, we utilize an in-fiber Faraday rotator to induce a nonreciprocal phase shift. To the best of our knowledge, this is the first all-fiber TDFL that combines an artificial saturable absorber (SA) with a chirped fiber Bragg grating (CFBG) as a wavelength-selective reflector. This cavity design is an excellent candidate to pump nonlinear processes such as supercontinuum and frequency comb generation since it does not require any SA material that degrades over time for mode-locking and could be made wavelength-tuneable via the CFBG.