Laser Ablation and Optical Analysis of Rare-earth Ion-doped NaYF4 and NaGaF4 crystals

D.N. Patel, M. Jumper, D.M. Wright III, S. Sarkisov
Oakwood University, US

Keywords: laser, ablation, rare-earth, colloids, crystals

Summary:

In this paper we investigate the pulverization and size analysis of bulk trivalent rare-earth ion doped crystals of NaYF4 and NaGaF4. These crystals were synthesized by using simple co-precipitation synthetic method. The initially prepared crystals had very weak or no fluorescence signals. The fluorescence intensity was significantly increased after the crystals were annealed at a temperature of 6000C. Nano-colloids of the crystals were obtained using polar solvents and they were utilized as laser filling medium in photonic crystal fibers. Under 980nm laser excitation holmium and ytterbium co-doped NaYF4 phosphor showed strong fluorescence signals and thulium and ytterbium co-doped NaYF4 phosphor showed strong fluorescence signals and the ytterbium and holmium co-doped NaGaF4 phosphor also showed strong fluorescence signals. We also present the log-log plot of laser intensity verses incident power for some of the fluorescence signals. Size analyses of the prepared nano-colloids were conducted using a dynamic light scattering instrument and atomic force microscope. Nano-colloids of the crystals are good candidates for fluorescent biosensing applications and also as a new laser filling medium in fiber lasers.