Jc. Fajardo et al., ELECTROCHEMICAL PURIFICATION OF HEAVY-METAL FLUORIDE GLASSES FOR LASER-INDUCED FLUORESCENT COOLING APPLICATIONS, Journal of non-crystalline solids, 213, 1997, pp. 95-100
An electrochemical purification stage has been incorporated into the c
onventional fabrication process of heavy metal fluoride glasses. This
change was undertaken to reduce the absorption losses associated with
residual transition metal impurities, particularly the Fe2+ band at 1.
0 mu m Purified samples doped with ytterbium exhibited net cooling due
to anti-stokes fluorescence and a relative cooling efficiency of abou
t 2% was observed via photothermal deflection spectroscopy. Pumping to
the lower Stark levels of the F-2(5/2) manifold, followed by populati
on redistribution across this manifold and fluorescence to the ground
state, results in net cooling. This cooling can be achieved only if en
ergy transfer and the extrinsic absorptive component of the host glass
are suppressed.