Mode-locked and free running operation of Nd,Gd:CaF2 crystal fiber laser

Abstract

Fluoride crystals (CaF2, SrF2) doped with neodymium Nd 3+ and codoped with non-active ions such as Y 3+ , La 3+ , or Gd 3+ for breaking clusters of active ions, have become interesting active media for diode-pumped mode-locked lasers. They posses broad emission spectra and longer fluorescence lifetime in comparison with widely used crystals such as Nd:YAG or Nd:YVO4. The crystal fibers grown by several groups in recent years might be attractive for high power operation and possibility of beam guiding. We investigated Nd,Gd:CaF2 cylinders 10 mm long with diameter of 1.9 mm end pumped by 790 nm LD. In free running regime the wavelength tunability of 41 nm (1040-1081nm) was achieved. In continuously passively mode-locked regime using SESAM the pulses 1.3 ps long at 1065 nm with 2 nm spectral with were generated. The average output power was 200 mW for pump power of 1.6 W. Comparison with operation of standard bulk Nd,Gd:CaF2 active media is also presented.