High Efficiency Pentaphosphates for Miniaturized Laser Applications

Abstract : The requirement for low-threshold high-efficiency laser sources for miniaturized rangefinder and fiber optic communication applications has led to the study of rare earth pentaphosphate compounds. Neodymium pentaphosphate (NdPP) has recently emerged as a promising 1.05 micrometer laser material operating in pulsed and cw modes, with thresholds of the latter reported less than 1 milliwatt. In contrast to doped lasers such as Nd:YAG, NdPP is a stoichiometric compound (NdP5O14) which accommodates up to thirty times more Nd than YAG. The evaluation and testing of NdPP lasers in prototype components using transverse and longitudinal optical pumping has been hindered due to the limited size (several mm), availabilty, and quality of the single crystals. We have devised unique modifications of conventional solution growth techniques in order to control reaction kinetics and precipitation rates. The largest bulk single crystals (greater than 1 cm) of yttrium and lanthanum substituted NdPP presently available were grown by these modified techniques. We have observed laser action in as-grown 90% Nd 10% Y pentaphosphate crystals with dimensions typically 4.5x3 mm in diamond-shaped cross section by 2 mm thick.