The UV-CHALLENGE project (duration of 36 months) is proposed by an academic-industrial consortium. The latter includes three academic French laboratories [Laboratoire de Chimie de la Matière Condensée (LCMCP) at Ecole Nationale Supérieure de Chimie de Paris (ENSCP), Laboratoire Charles Fabry (LCF) at Palaiseau and Laboratoire de Matériaux Optique, Photonique et Système (LMOPS) at Metz (University de Lorraine)], two French industrial partners [EOLITE Systems in Bordeaux and Cristal Laser (CLASER) in Nancy] and one German industrial partner [Forschungsinstitut für Edelsteine/Edelmetalle GmbH (FEE)] which is member of the consortium without any requested financial support from ANR. The main purpose of this project is to demonstrate the capabilities of new non linear optical (NLO) crystals for practical UV laser light generation. The generation of UV light by means of non linear optical (NLO) processes from an infrared fundamental beam is indeed a promising path to design all solid-state UV lasers. For this purpose, several non linear optical crystals have to be used, but there are only very few NLO crystals that can achieve the last stage of frequency conversion towards UV, especially when wavelengths below 270 nm are targeted. In this framework, the consortium involved in this project has already identified two families of crystals with real potentialities. They are based on YAl3(BO3)4 (YAB) and Ca5(BO3)3F (CBF). These crystals were identified in a previous project, called “UV-Borates” (2006-2010), and they have been developing to compete with the commercial crystals which are practically used today for UV conversion: LiB3O5 (LBO) for third harmonic generation (THG: 343 – 355 nm) and ß – BaB2O4 (ß – BBO) or CsLiB6O10 (CLBO) for fourth harmonic generation (FHG: 237 – 266 nm) by frequency doubling of green light. These commercial crystals have some severe drawbacks: they are hygroscopic (very critical for CLBO) and their lifetime in UV laser systems is unsatisfactory. YAB, CBF and some of their related compounds are proposed to solve these limitations and to increase the reliability and/or the efficiency of the THG and FHG processes. For deeper understanding of aging effect, this study will extend to the analysis of the behavior of commercial crystals like LBO and BBO. UV-CHALLENGE is a multidisciplinary project involving materials science, crystal growth and machining, linear and non linear optics, conversion efficiency and material aging studies. The consortium of the present project consists of 6 partners having more than 4 years of collaboration in the field of nonlinear optical materials. The first objective is first to optimize the crystal growth conditions leading to enhanced optical quality crystals for fabrication of NLO crystals oriented and polished for specific configurations. Second, the precise determination of the physical properties as well as the relationships between optical and structural properties (impurities, twinning, absorption spectroscopy, EPR and Raman spectroscopy, surface characterization) of the new NLO crystals proposed in this project will be emphasized. Finally, the nonlinear optical properties and the aging behavior of the crystals will be tested in practice and compared to commercial NLO crystals. Aging in particular is a key issue to any practical application of UV sources. The achievement of these objectives will require a large panel of basic optical measurements, the accurate machining of many crystals, and the direct evaluation of UV conversion performances. All these studies will be analyzed and provided as feedback to the crystal growth process.