Ultrafast mode-locked Ho-doped all-fiber laser operating at 2.05 pm

Summary form only given. Passively mode-locked, ultrafast and compact laser sources operating in the wavelength range beyond 2 μm have gained interest for several applications such as nonlinear frequency conversion into the mid-infrared and THz region, material processing, medicine etc. Typically, Ho-doped optical fibers (HDF) are used to directly address this spectral region in ultrafast mode-locked oscillators while Ho:YLF amplifier systems can boost the pulse energy to multi mJ-level, provided, the seed wavelength of the oscillator corresponds to the emission wavelength of the Ho:YLF crystal which is centered around 2051 nm with spectral bandwidth of about 5 nm.Recently, Peng Li et al. demonstrated a tunable soliton operation covering 2050 nm in a HDF oscillator mode-locked by nonlinear polarization evolution (NPE) [1]. However, the setup consisted of a free-space part resulting in an operation which is more liable to environmental influences. In [2] an all-fiber Ho-doped oscillator based on graphene saturable absorber has been presented by J. Sotor et al. with an unsuitable emission wavelength at 2067-2081 nm for Ho:YLF seeding. In this contribution, we present an ultrafast Holmium-doped laser operating at 2052 nm in an all-fiber linear cavity design mode-locked by means of a semiconductor saturable absorber mirror (SESAM). The laser generates soliton pulses at a repetition rate of 27.3 MHz with a spectral bandwidth of 4.3 nm which corresponds to Fourier-limited pulse duration of 1.16 ps.