Development of tetravalent chromium doped tunable solid state laser materials

In this thesis, we describe the development of novel tunable solid state laser materials and the characterization of these materials. Tunable solid-state lasers based on tetravalent chromium ion (Cr4+) are expected to cover the 1–2 μm range, which is an eye-safe range, and is of great importance for optical communications, remote sensing, lidar, scientific and various medical applications. First of all, chemical compounds with formula Cr4+:A+₄(Si, Ge)O₄, and A+₂M2+(Si, Ge)O₄, where A = Na, K, Li and M = Ca, Mg, Zn, Cd, were investigated in a search for potential crystalline hosts for Cr4+ doped tunable solid state lasers. Basic spectroscopic properties of the potential laser hosts were measured. Strong Cr4+ emission in near-infrared (1.1 to 1.6 μm) region has been observed in Cr-doped Li₂M2+X4+O ₄ (X=Si, Ge) crystalline media. In Li₂CaSiO₄ and Li₂CaGeO₄, two phases were identified by DTA. The phase transition point is 960°C and 950°C for Li₂CaGeO₄ and Li₂CaSiO₄ respectively, and the melting point is 1150°C and 1060°C for Li₂CaGeO₄ and Li ₂CaSiO₄ respectively. Pseudo-binary systems of Li₂CaSiO ₄ - LiF and Li₂CaGeO₄ - LiF/LiCl were investigated, and the solubility curve of Li₂CaSiO₄ - LiF was obtained.; Absorption and emission spectra of the crystals Li₂CaSiO ₄ and Ca₂GeO₄ were measured. Fluorescence spectra at room temperature and at liquid nitrogen temperature were also measured. In all the Cr4+ doped laser hosts, Cr4+ has been identified as the optically active center responsible for the near-informed emission in the 1100 to 1600 μm spectral range. The room-temperature lifetime of the Cr4+-emission in Li₂MgGeO₄ is about 90 μs, the longest lifetime observed up to now for Cr4+-doped laser systems.; Finally, the physical properties of the novel laser and the potential laser hosts were characterized. The DSC method was used to measure the heat capacity and TMA was used to investigate the thermal expansion coefficient. The samples for DSC and TMA include Ca₂GeO₄, Li ₂CaSiO₄ and LiScGeO₄. The MDSC technique was used in studying the thermal conductivity of Ca₂GeO₄. (Abstract shortened by UMI.)...