Spectroscopic properties of Ho 3 ions doped in tellurite glass S.B. Rai *, Anant Kumar Singh, Shiv Kumar Singh Laser and Spectroscopy Laboratory, Department of Physics, Banaras Hindu University, Varanasi 221005, India Received 28 October 2002; accepted 17 December 2002 Abstract Spectroscopic properties of Ho 3 doped tellurite glass (1 mol.% of Ho 3 ) have been studied. The absorption and fluorescence spectra have been recorded and analysed using the Judd  /Offelt theory. The analysis indicates that Ho doped tellurite glasses can show lasing on the 5 F 4 ( 5 S 2 )  / 5 I 8 transition (548.0 nm). # 2003 Elsevier B.V. All rights reserved. Keywords: Ho 3 ; Tellurite glass; Fluorescence spectra; Absorption spectra; Lasing transitions 1. Introduction Glasses are increasingly used as host material for solid state lasers based on rare earth and transition metal ionic transitions. The advantages with glasses are the ease with which large homo- geneous pieces can be produced. The nonlinear refractive indices can be made low and the doping concentration can be large. It has been shown that the fluorescence intensity of rare earth ion are enhanced several fold when glass hosts with low phonon energies e.g. heavy metal fluoride, oxide, germinate, tellurite etc. [1  /3] are used. Recently the spectroscopic properties of Ho 3 in oxyfluor- oborate glass have been studied by us [4]. It was thought worthwhile to investigate the same ion in a tellurite glass and compare the results. Triply ionized holmium is known to lase at 2.1 and 0.55 mM [5] and a number of upconversion transitions are known [6]. The absorption and fluorescence spectra of Ho 3 ion in different hosts have been studied by several authors (see [7], for a good review). From these studies it has been concluded that Ho 3 has a 5 I 8 state and 5 I 7 , 5 I 6 , 5 I 5 , 5 I 4 , 5 F 5 , 5 F 4 , 5 F 3 etc. as low lying excited states. Several of these states are metastable and are suitable for laser transitions. Two hypersensitive transitions involving 5 G 6 and 3 G 6 states are also known. The energy levels for this ion are known upto 50 000/cm, but are well assigned upto 40 000/ cm. 2. Experimental We have used the following composition for preparation of the glass * Corresponding author. Tel.:  /91-542-2307308; fax:  /91- 542-368468. E-mail address: sbrai@banaras.ernet.in (S.B. Rai). Spectrochimica Acta Part A 59 (2003) 3221  /3226 www.elsevier.com/locate/saa 1386-1425/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/S1386-1425(03)00178-1