Nd,Gd:SrF2 Laser Generating 600 fs Pulses at 0.9 W of Pump Power

Fluoride crystals (CaF
₂
, SrF
₂
) doped with neodymium Nd
³⁺
and codoped with non-active ions as Y
³⁺
, La
³⁺
, or Gd
³⁺
for breaking clusters of active ions, have become recently interesting active media for the diode-pumped mode-locked lasers. They possess broader emission spectra as well as longer fluorescence lifetime in comparison with widely used crystals such as Nd:YAG or Nd:YVO
₄
. The femtosecond Nd,Y:SrF
₂
laser generating 97 fs pulses was reported in the Ti:sapphire pumped system [1]. We have reported continuously mode-locked operation of this laser pumped by a 2 W multimode laser diode and mode-locked using a semiconductor saturable absorber generating pulses with the duration of 258 fs [2]. In laser systems with La
³⁺
codoped crystals, which have wider tunability than Y
³⁺
codoped crystals, passively mode-locked 354 to 1200 fs and continuous-wave 1044 to 1081 nm tunable operation was reported in the system pumped by 4 W laser diode [3]. Recently a new Nd,Gd:SrF
₂
crystal has been investigated and the dual wavelength mode-locked picosecond operation was reported for pump power higher than 3.8 W [4]. We reported femtosecond operation of laser with this crystal and obtained pulses as short as 228 fs with output power of 2 × 50 mW in system pumped by 2 W laser diode for absorbed pump power of 1320 mW [5].