Ultrafast thulium fiber laser operating at 1750 nm

Summary form only given. Passively mode-locked femtosecond fiber lasers operating in the telecom band around 1.5 μm are well discovered since many years. Thulium- and Holmium-based light sources in 2 μm region have greatly gained interest in recent years. Because of the absence of optical transitions in fibers doped with rare-earth ions, the gap between these two spectral regions, namely laser sources at wavelengths around 1750 nm, have hardly been investigated, even though this wavelength region has some interesting applications, such as multi-photon fluorescence imaging [1] or medical applications [2].Here, we present a purely intrinsic NPR modelocked Thulium based system at 1750 nm, operating in the fundamental soliton regime. The self-starting setup is shown in Fig. 1. The basic idea is to generate high losses at the Thulium peak emission wavelength around 1940 nm and take advantage of the broad emission cross section.