Possible trends for the growth of low scattering Nd:YVO4 laser crystals; phase relations — growth techniques

Transparent and inclusion-free RE1−xLaxVO4 (RE=Gd, Y) single crystal fibers grown by LHPG technique

“…The major problem in the growth process of such crystals lies in the valence change of vanadium ions, from V 5+ to V 4+ or even V 3+ , at high temperature. This was pointed out as the cause of the black color or black inclusions inside the grown crystals, as described by Erdei et al [7] in the case of YVO 4 crystal fibers. Other difficulties related to the growth process of those compounds are: (1) the high melting point (41800 1C); (2) oxygen deficiency due to vanadium oxide dissociation and evaporation; and (3) a characteristic spiral growth in the case of gadolinium vanadates [10,11].…”

“…It has been demonstrate that the black color in the REVO 4 single crystals is associated to the changes in the vanadium ion valence [7]. For pure REVO 4 (RE ¼ Y and Gd), the effective segregation coefficient of the vanadium ionic species seems to behave as if they have similar values (k V 5þ eff % k V 4þ ;V 3þ eff ) [7] and only black color crystals and melt are obtained by LHPG technique in air atmosphere.…”

“…For pure REVO 4 (RE ¼ Y and Gd), the effective segregation coefficient of the vanadium ionic species seems to behave as if they have similar values (k V 5þ eff % k V 4þ ;V 3þ eff ) [7] and only black color crystals and melt are obtained by LHPG technique in air atmosphere. The composition and temperature measurements (Figs.…”

“…Of all the materials suitable for use as the active element with these types of lasers, the vanadate single crystals are very important due to the possibility of obtaining laser system with low threshold and high slope performance and efficiency [1,2]. However, the difficulties involved in the growth of high quality REVO 4 (RE ¼ Y, Gd) single crystals are limiting the production of these compact solid state laser systems [6][7][8][9]. The major problem in the growth process of such crystals lies in the valence change of vanadium ions, from V 5+ to V 4+ or even V 3+ , at high temperature.…”

Heat treatment and optical absorption studies on Nd:YVO4 crystal

“…Compared with the laser crystal Nd:YAG, Nd:YVO 4 crystal has a low pumping threshold, large emission section (2.7 times at 1.06 mm and 18 times at 1.34 mm), high absorption coefficient (4 times), wide absorptive area at 809 nm, strongly polarized laser output, and good mechanical physical and chemical properties [1][2][3][4]. Although the various growth techniques, such as Czochralski, Verneuil, floating zone, Bridgman, laser-heated pedestal growth (LHPG) and top seeded solution growth (TSSG) method, could be used to grow pure YVO 4 and rare earth-doped YVO 4 crystals, the Czochralski method is proved to be the most successful at present [5][6][7][8]. However, there are weak absorptions at 1064 nm in as-grown Nd:YVO 4 crystal, and have longer relaxation time.…”