Dual wavelength room temperature laser operation of colour centres in lithium fluoride

Tunable room-temperature laser operation has been achieved on two spectral bands from colour centres in a slab of LiF crystal pumped by the frequency-doubled output of a Q-switched Nd : YAG laser. An initial build-up of laser action in the red (∼715 nm) has been observed to be followed by a period during which the intensity of the red emission reached a peak and as it decreased a near infra-red (∼940 nm) lasing component evolved. The output at this longer wavelength emission increased to a relatively constant value and long-term stable laser operation was maintained.