Abstract of Publication No. 489
Near-infrared (NIR) laser excitation into the Yb3+
2F5/2 absorption transition
around 10,200 cm−1 at 12 K leads to red and green upconversion
emission in MnCl2:Yb3+ and
Zn2SiO4:Yb3+; Mn2+, respectively.
The photon upconversion (UC) emission is centered around 15,240 cm−1
for MnCl2:Yb3+ and around 19,050 cm−1 for
Zn2SiO4:Yb3+; Mn2+ and is ascribed
to the Mn2+ 4T1
transition in both compounds. The shift of the Mn2+ emission energy
is due to the different coordination and ligand strength. Pulsed measurements
indicate a sequence of ground-state absorption (GSA) and excited-state
absorption (ESA) steps for the upconversion process. We conclude that the UC
process in both compounds occurs by an exchange mechanism involving
Yb3+ and Mn2+ ions.
Zn2SiO4:Yb3+; Mn2+ is the first
example of a Yb3+–Mn2+ upconversion system to show visible
(VIS) by eye Mn2+ UC emission at room temperature.