Absorption and photoluminescence studies of CdGa 2 S 4 :Cr M.B. Johnson a, * , S.B. Mirov a , V. Fedorov a , M.E. Zvanut a , J.G. Harrison a , V.V. Badikov b , G.S. Shevirdyaeva b a Department of Physics, The University of Alabama at Birmingham, 1300 University Boulevard, UAB Birmingham, AL 35294-1170, USA b Kuban State University, Krasnodar 350640, Russia Received 26 October 2003; received in revised form 11 January 2004; accepted 23 January 2004 Abstract The potential of using ternary defect chalcopyrites as laser active materials is investigated by performing absorption, photoluminescence, and EPR studies of as-grown and vacuum annealed Cr-doped CdGa 2 S 4 . Although no consistent affect of annealing is observed, an increased concentration of Cr in the melt during growth is shown to broaden an absorption band at 1288 nm. Several of the absorption bands could be attributed to multiple charge states of Cr thought to be present in the crystal. A broad fluorescence was observed at visible wavelengths; however, no emission was detected in the middle-infrared region, contrary to expectation. The lack of infrared fluorescence may be attributed to an exchange interaction involving Cr impurities. Ó 2004 Elsevier B.V. All rights reserved. PACS: 33.20.Ea; 33.50)j Keywords: Defect chalcopyrite; CdGa 2 S 4 ; CdGa 2 S 4 :Cr; Absorption; Optical studies; Photoluminescence 1. Introduction Divalent transition metals, particularly chro- mium, can be used in II–VI materials such as ZnSe and ZnS to produce broadly tunable continuous wave middle-infrared (mid-IR) lasers [1]. Recent investigations demonstrate that ternary com- pounds may also be used to create middle infrared lasers. For example, Nostrand and coworkers show that the Dy 3þ doped ternary compound CaGa 2 S 4 , an orthorhombic ternary compound with a space group of D 24 2h , lases from 4300 to 4400 nm at room temperature with a pump wavelength of 1319 nm [2]. Our work focuses on the potential of the CdGa 2 S 4 doped with Cr as a laser-active material. CdGa 2 S 4 has a space group of S 2 4 and is classified as a defect chalcopyrite, a material that is differentiated from the chalcopyrite structure by stoichiometric vacancies within the crystal lattice. Chalcopyrites and defect chalcopyrites are tetra- * Corresponding author. Tel.: +1-2563039351; fax: +1- 2059348042. E-mail address: mbj@uab.edu (M.B. Johnson). 0030-4018/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.optcom.2004.01.054 Optics Communications 233 (2004) 403–410 www.elsevier.com/locate/optcom