MECHANISMS OF NEAR-INFRARED TO VISIBLE UP-CONVERSION IN CSCDBR3-HO3+

Crystals of CsCdBr3 doped with x% Ho3+ (x = 0.35, 2.25) were synthesiz ed and studied by high-resolution absorption, upconversion luminescenc e and excitation spectroscopy in the temperature range 295-4 K, The ti me evolution of the upconversion luminescence, within 1.5 ms of a puls ed excitation, was recorded. Two NIR to VIS upconversion mechanisms we re identified. Below 100 K upconversion occurs by energy transfer with in Ho3+ pairs. Above 100 K an excited-state absorption is dominant. It occurs whenever the energies of the ground- and excited-state absorpt ion steps coincide. At room temperature this latter process overall is 5 times more efficient than the energy-transfer process. (C) 1998 Els evier Science B.V. All rights reserved.