Tm 3þ :CaF 2 for 1.9 lm laser operation P. Camy, J.L. Doualan * , S. Renard, A. Braud, V. M enard, R. Moncorg e Centre Interdisciplinaire de Recherche Ions Lasers, UMR 6637, CEA-CNRS-ENSICAEN, Universit e de Caen, 6 Boulevard Mar echal Juin, 14050 Caen Cedex, France Received 3 February 2004; received in revised form 19 March 2004; accepted 19 March 2004 Abstract Tm 3þ doped CaF 2 single crystals have been grown and studied for their broadband absorption and emission properties. Tunable laser operation was demonstrated for the first time around 1.9 lm. Their spectroscopic investi- gation shows that rare-earth ions interactions occur at relatively low dopant concentrations, thus favoring 1.9 lm emission, more particularly. As a matter of fact, efficient, tunable, room temperature laser operation is reported around 1.9 lm with a 1.34% Tm 3þ doped sample. The crystal was pumped at about 767 nm and the emission wavelength was tuned between 1835 and 1970 nm. A slope efficiency of 41% is achieved with a 10% transmission output coupler. Ó 2004 Elsevier B.V. All rights reserved. PACS: 42.70.Hj; 78.20.)e Keywords: Solid state laser; Infrared laser; Spectroscopic properties; CaF 2 ; Tm 3þ 1. Introduction There is a continuing interest in the search and the development of new solid-state lasers operat- ing around 2 lm for various applications. Among these applications, one can mention first laser surgery, because of strong water absorption around 2 lm, then environmental sensing, which is based on the well-known LIDAR technique, for the detection, ranging and analysis of remote at- mospheric species. For these applications, solid-state lasers based on the 3 F 4 ! 3 H 6 emission transition of Tm 3þ ions in crystalline materials present a number of ad- vantages: (1) they can be directly pumped around 790 nm ( 3 H 6 ! 3 H 4 absorption transition) with the aid of commercially available high power AlGaAs laser diodes [1], (2) they can be very efficient, with laser efficiencies of the order of 40–50%, this being due to efficient cross-relaxation energy transfers occurring among the Tm 3þ ions at high dopant concentrations and giving rise to two excited ions in the 3 F 4 upper laser level for each absorbed * Corresponding author. Tel.: +33-02-31-45-25-61; fax: +33- 02-31-45-25-57. E-mail address: jean-louis.doualan@ismra.fr (J.L. Doua- lan). 0030-4018/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.optcom.2004.03.055 Optics Communications 236 (2004) 395–402 www.elsevier.com/locate/optcom