SBIR-STTR Award

The growth of high optical quality crystals of YVO4:Yb for laser applications using the high temperature solution (HTS) method is proposed. The utilization of this technique permits crystallization at temperatures considerably below the high melting point of YVO4. This process will result in crystals with very low scattering losses, high composition uniformity and large size. This growth process has been utilized for KTP and KTA materials and routinely produces large, high optical quality crystals.

The growth of large high optical quality YV04:YB crystals by the high temperature solution technique will be investigated. Low temperature fluxes the potential if which was previously determined will be used. Since this technique permits growth at temperatures far below the melting pint of YV04, crystals with low defect concentration will be grown. Seeded growth will be used to determine optimum parameters such as seed loading or size, cooling rate, rotation rate and temperature gradient within the melt. Using these growth parameters, the process will be scaled up to allow growth of larger crystals. Crystals with Yb doping levels of 1,3,5 and 10 mole% large enough to accurately measure spectroscopic propertied relevant to lasing will be grown. Properties that will be measured include absorption spectra and absorption cross section, fluorescent lifetime, emission cross section and excitation spectra. Crystals with the optimum Yb doping level will be fabricated into rods and polished for laser studies. The potentially useful laser host crystal, GdV04, will be investigated with respect to ease of crystal growth and fundamental laser properties.

Benefits:
The technology developed in these program will permit the production of large high quality laser crystals of YV04:Yb for diode pumped solid state lasers. These lasers are expected to have advantages over YAG:Nd for certain applications in medical, industrial and military systems. Other dopants such as thulium and holmium in YV04 have potential as mid-infrared laser sources. Crystals of YV04 doped with other either Nd or Yb are ideal for microchip lasers because of their high emission cross section. Coupled with an efficient nonlinear crystal such as KTP efficient compact sources of green light can be made. Because of the lower growth temperature these crystals are expected to have much lower defect concentration than crystals grown by high temperature melt techniques.

Keywords:
Laser Crystals Yttrium Orthovanadat Ytterbium doping HTS growth method Crystal growth Fluorescence