Passively mode-locked 354–1200 fs and continuous-wave 1044–1081 nm tunable operation of diode-pumped Nd,La:SrF2 laser

The fundamental spectroscopic properties of four Nd,La:SrF2 crystals with different $ \newcommand{\Nd}{\rm Nd^{3+}} \Nd$ and $ \newcommand{\La}{\rm La^{3+}} \La$ concentrations are described. The laser generation was successfully achieved with all crystals; the best results with the $0.5$ at.% $ \newcommand{\Nd}{\rm Nd^{3+}} \Nd$ , 8 at.% $ \newcommand{\La}{\rm La^{3+}} \La$ :$ \newcommand{\SrF}{\rm SrF_2} \newcommand{\Sr}{\rm Sr^{2+}} \SrF$ are presented. The laser output wavelength tuning properties were investigated, and were found to have continuous tuning range over 37 nm from 1044 to 1081 nm. Two different saturable absorbers were succesfully tested for the passively mode-locked regime, and the intracavity dispersion
compensation influence was studied. In the optimal set-up, a continuously
mode-locked train of pulses as short as 354 fs was generated at the repetition rate of $146.2$ MHz. The laser central wavelength was  ~1059 nm and the overall output power reached 300 mW in two beams with absorbed pump power of less than $1.8$ W.