Near-infrared-to-visible photon upconversion process induced by exchange interactions in Yb3+-doped RbMnCl3 - art. no. 165102

Crystals of RbMnCl3 doped with Yb3+ exhibit a strong orange luminescence un der near-infrared Yb3+ excitation at 10 K. The broad emission band extendin g from 17 200 cm(-1) to 13 000 cm(-1) is identified as a T-4(1)--> (6)A(1) transition on Mn2+. Of the two inequivalent Yb3+ sites identified by site-s elective high-resolution spectroscopy, only one is able to induce efficient upconversion. Excitation with 10-ns pulses indicates that no energy transf er is involved, and the upconversion process consists of a sequence of grou nd-state absorption and excited-state absorption steps. One- and two-color excitation spectra confirm the occurrence of these two steps. The efficienc y of the upconversion process at 10 K and for an excitation power of 200 mW focused by a 53-mm lens is 2 percent. An upconversion mechanism based on e xchange interactions between the Yb3+ and Mn2+ ions is proposed to account for the observed behavior.