Journal of Luminescence 102–103 (2003) 737–743 Infrared to visible up-conversion in thulium and holmium doped lutetium aluminum garnet Ki-Soo Lim a, *, P. Babu a,1 , Sun-Kyun Lee a , Van-Thai Pham a , D.S. Hamilton b a Department of Physics, Chungbuk National University, 48 Gaesin-dong, Cheongju, Chungbuk 361-763, South Korea b Department of Physics, University of Connecticut, Storrs, CT 06268, USA Abstract We report on the up-converted emissions at 367, 458 and 483 nm in thulium doped lutetium aluminum garnet (LuAG) under infrared excitation in the range of 730–800 nm. We also observe blue and strong green emission in thulium and holmium codoped LuAG with near infrared excitation. Excitation spectra, power dependence, temporal behavior and temperature dependence of up-converted emissions were measured to explain the up-conversion mechanisms. Several cross-relaxation mechanisms and excited state absorption are found to be responsible for the observed up-conversion processes. r 2002 Elsevier Science B.V. All rights reserved. Keywords: Tm:LuAg; Tm; Ho:LuAG; Up-conversion; Energy transfer 1. Introduction Rare earth ion doped lutetium garnets, Lu 3 Al 5 O 12 (LuAG), are efficient materials in generating near-infrared laser radiation at room temperature [1]. In particular, Tm or Tm,Ho doped LuAG has been proven to be most promising for laser action around 2 mm [2–4]. While spectroscopic studies have been scarce in these materials, Patel et al. [5] reported the photon avalanche up- conversion in Tm 3+ :LuAG under 618 nm excita- tion. The same group reported the spectroscopic and up-conversion studies in Ho 3+ :LuAG [6]. So far most of the up-conversion studies in Tm doped materials were concerned with the excitation in the region 617–650nm [5,7] or dual wavelength pumping at 785 and 628–648nm [8,9] as they provide good energy matching for pumping mechanism. To our knowledge there is no report on the infrared to blue (483 and 458nm) up- conversion emission from 1 G 4 and 1 D 2 states in the Tm-doped materials with single wavelength ex- citation around 780nm. This wavelength matches with the strong ground state absorption of Tm 3+ ion. Here we report on the up-conversion in 4%Tm 3+ :LuAG with near infrared excitation in the range 750–800nm. The dynamics of up- conversion is explained by taking into account various cross-relaxation and excited state absorp- tion (ESA) processes. We also report on the blue– green visible up-conversion in 6%Tm,0.36%Ho co-doped LuAG using near infrared excitation. *Corresponding author. Tel.: +82-43-261-2239; fax: +82- 43-271-1653. E-mail address: kslim@trut.chungbuk.ac.kr (K.-S. Lim). 1 Permanent address: Department of Physics, Government Degree College for Men, Wanaparthy, 509 103, A.P., India. 0022-2313/02/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0022-2313(02)00635-X