LAUSR

Abstract The efficient near infrared 2 F 5/2 → 2 F 7/2 downconversion emission of Yb 3+ was observed upon excitation of Gd 3 Al 5 O 12 :Yb 3+ nanocrystals in UV range. Its integrated intensity was measured as a function of excitation power in the range 1–30 mW and compared for a low and high concentration of Yb ions. The model of luminescence dependency on absorbed pump power was applied to investigate the emission mechanism. It was found that the N parameter of that model, interpreted as the order of the process, was dependent on concentration of Yb ions. Moreover, the presence of Yb 2+ has been confirmed. The mechanism of energy transfer processes leading to observed Yb 3+ emission was discussed in terms of a sequence of successive cross relaxations via a presence of divalent and trivalent Yb ions: Gd 3+ →Yb 2+ → (Yb 3+ ) * .