CC BY
25LS-PS-3
Structural features and optical properties of Ca3(VO4)2:Mn laser crystals
L. Ivleva1, I. Voronina1, E. Dunaeva1, M. Doroshenko1, A. Papashvili1
1Prokhorov General Physics Institute of the Russian Academy of Sciences,
Laser Materials and Technology Research Center at GPI, Moscow, Russian Federation
The undoped calcium orthovanadate Ca3(VO4)2 with whitlockite-type structure has been investigated earlier for high-temperature ferroelectricity (Tc=1383 K), second-harmonic generation, and stimulated Raman (QR=854 cm-1) scattering, Ca3(VO4)2:Tm3+ was suggested as crystalline medium for 2-p.m lasers.
In this paper, the functional properties (fluorescent, laser) were studied in their connection with the fundamental characteristics (composition and structure) and depending on the background (composition of the initial charge, the method of introducing activators, growth conditions and post-processing) of Ca3(VO4)2 doped with manganese ions. Doped Ca3(VO4)2 crystals were grown by Czochralski method. Dopant ions were introduced into the melt in form of oxide (Mn2O3). Another method of activator introducing is diffusion annealing in special mixture. In this case maximal concentration of Mn ions in Ca3(VO4)2 was achieved. Absorption spectra measured at low (77K) and room temperature have shown characteristic absorption lines of Mn5+ ions peaking around 700 nm. Selective excitation into the absorption band at low (15K) temperature allowed to observe three different Mn5+ ions fluorescence spectra. Two narrow fluorescence spectra were to be quite similar in shape with small difference in position of 1176 nm and 1190 nm. Fluorescence lifetime measured for these two fluorescence maxima have shown about twice difference: 500 ms at 1176 nm and 260 ms at 1190 nm respectively and can be attributed to different Mn5+ electronic transitions. Additional broadband fluorescence of some new type of Mn5+ ions optical centers (FWHM of about 1000 nm at 15 K) was observed in Ca3(VO4)2:Mn5+ crystal for longer 768 nm excitation. This type of Mn5+ optical centers is characterized by much shorter fluorescence lifetime of 100 ms at 15 K and was not reported previously. Much broader fluorescence line of these optical centers allows to obtain oscillation wavelength tuning in the range of 1150-1500 nm which can be interesting for laser applications.
