Ca3(VO4)2:Tm3+-A new crystalline medium for 2-μm lasers

Calcium orthovanadate crystals doped with Tm3+ ions were successfully grown by Czochralski method. The value of anomalous birefringence did not exceed of 1.3 × 10−5 cm−1 for as-grown samples. The effective segregation coefficient of Tm3+ in a vacancy-compensated crystal was determined as 0.8. It was shown that the formation of the domain structure depends on the crystal composition, crystallization conditions, and annealing treatment. Polarized absorption spectra for heavily doped Ca3(VO4)2:Tm3+ crystal demonstrate a stronger absorption for the E⊥c case. The normalized fluorescence spectra for E⊥c and E||c cases showed about 1.5 times higher maximum fluorescence intensity for E⊥c. Lasing of the thulium doped Ca3(VO4)2 crystal was demonstrated for the first time. The oscillation spectrum was measured to be centered at about 1970 nm with about 20-nm width at half maximum.