Lasing characteristics of the F-2(+) colour centres in LiF crystal

The LIF:F-2(+) colour centre laser was achieved by creating the F-2(+) cent res through the photoionization of the F-2 colour centres at room temperatu re using 532 nm laser radiation and simultaneously by exciting the produced F-2(+) centres with the same 532 nm radiation. Simultaneous laser oscillat ion due to the F-2 and F-2(+) colour centres was observed but the F-2 laser oscillation disappeared in about 100s during the pumping. It was observed that the F-2(+) laser intensity increases with a form given by P(F-2(+)) si milar to P-2, where P is the pump pulse energy, but it increases with a for m given by P(F-2(+)) similar to P-0.85 at P > 8 mJ. A discussion on the rea son for this deviation from the P-2 law is given.