Thermal, spectroscopic and laser properties of Yb3+,Na+:CaF2 single crystals

The effects of Na+ doping level on the thermal conductivities, absorption and emission spectra, and fluorescence lifetimes of Yb3+,Na+:CaF2 crystals were systematically studied. Sites structure, covalent force, and crystal field strength of Yb3+:CaF2 crystals were markedly varied by codoping Na+ as charge compensator. The 2.0 at% Yb3+ and 3.0 at% Na+-codoped CaF2 crystal was demonstrated to operate in diode-pumped passively mode-locking scheme. Transform-limited 1 ps laser pulses were obtained, showing the crystal capable of producing ultra-short laser pulses.