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Single crystals of undoped and Co-doped β-Ga2O3 with different doping concentration have been grown using optical floating zone technique. The powder X-ray diffraction analysis shows no significant variation in lattice parameters on Co doping in the crystal. The absorption spectra shows a decrease in the absorption edge with Co-doping and a broad absorption band in the range 950-1700 nmdue to transitions in Co ions. The absorption analysis shows that both undoped and Co-doped β-Ga2O3 crystal possess indirect bandgap with band gap energy decreasing on increasing the Co-doping. Further, the Urbach energy has also been estimated which is found to increase with the increase in Co-doping. The observed absorption band can be utilized as a saturable to achieve passive Q-switching of near IR lasers. [ABSTRACT FROM AUTHOR]

Single crystals of Nd (0.6 at. %) doped GdVO4 were grown by optical floating zone technique with a typical dimension of ~ 5 mm in diameter and ~ 20-35 mm in length. The grown crystals were subjected to optical transmission and luminescence studies to investigate their absorption and emission characteristics. The absorption coefficient spectra depicted characteristic multiple Nd absorption peaks with highest absorption ~ 10 cm-1 at 594 nm and 9.35 cm-1 at 808 nm. The absorption coefficient at 880 nm is nearly half of absorption at 808 nm. The photoluminescence (PL) excitation spectra revealed higher emission at 1064 nm for 808 nm excitation wavelength. It was also observed that the PL emission at 1064 nm with 808 nm excitation is around two times stronger than the emission with 880 nm excitation. [ABSTRACT FROM AUTHOR]

Here issues related to the growth of doped YVO4 crystal by the optical floating zone (OFZ) technique have been discussed. Focus has been on the synthesis of the starting material, melt stability and the controllability of the oxidation state of Cr ion. It has been observed that the molten zone is more stable for the growth along [100] in comparison to growth along [001]. As a result crystals grown along [001] suffer from severe overflow problem. Spectroscopic parameters of absorption and emission characteristics for the Nd and Er doped crystals have been discussed in the light of Judd-Ofelt analysis. [ABSTRACT FROM AUTHOR]