UPCONVERSION SPECTROSCOPY OF ERBIUM DOPED FLUORIDE CRYSTALS

Abstract
We study the red-to-green upconversion in Er³⁺ doped fluoride crystals. We show that the dominant upconversion process depends on the excitation wavelength : a two-step absorption between 631 and 634 nm and a two-ion interaction between 641 and 647 nm for an Er³⁺ doped cadmium fluoride at 77 K. An efficient IR (803 nm)-to-green upconversion via three-step absorption is also reported, for the fist time, in Er³⁺ doped strontium fluoride at 300 K. A selection of sites exhibiting two or three transitions which energetically coincide with an appropriate laser excitation wavelength could optimize the upconversion efficiencies.