Rare-earth Dopant Concentration Research Articles

Computer modelling of defects and dopants in mixed metal fluorides

This paper describes a computer modelling study of rare earth doping in the mixed metal fluorides LiCaAlF 6 , LiSrAlF 6 and LiYF 4 . All these materials have potential technological applications, providing the motivation to improve understanding of their defect chemistry; in particular the energetics of doping and the sites occupied by dopant ions. Computer modelling is used to calculate the effect of rare earth dopant concentration on the structure of LiYF 4 , and to predict the sites occupied by rare earth dopants and the corresponding form of charge compensation, in LiCaAlF 6 and LiSrAlF 6 .

Patterns of glow peak movement in rare earth doped lanthanum fluoride

Low temperature thermoluminescence data from rare earth doped lanthanum fluoride is characterized by numerous glow peaks. These differ in temperature as a function of the substituted rare earth ion, dopant concentration and thermal annealing. Analysis of the component bands in terms of activation energy, frequency factor and kinetic order reveals simple patterns in which the movement of the glow peaks is related to the ionic radii of the rare earth ions. Models for the thermoluminescence signals resulting from close association of the dopant recombination sites and the charge traps are discussed. Further consideration of a preference for impurity clustering, in order to reduce lattice strain, is used to explain the concentration and annealing induced changes.

Rare earth-doped alumina thin films deposited by liquid source CVD processes

Two types of liquid-source CVD processes are proposed for the growth of rare earth-doped alumina thin films suitable as amplifying media for integrated optic applications. Amorphous, transparent, pure and erbium- or neodymium-doped alumina films were deposited between 573 and 833 K by atmospheric pressure aerosol CVD. The rare earth doping concentration increases by decreasing the deposition temperature. The refractive index of the alumina films increases as a function of the deposition temperature from 1.53 at 573 K to 1.61 at 813 K. Neodymium-doped films were also obtained at low pressure by liquid source injection CVD.

Low-loss rare earth doped single-mode fiber by sol-gel method

Using a sol-gel process for rare-earth ions doping, a minimum optical loss of less than 2 dB/km in the region of 1.15μm has been reproducibly achieved in Er 3+ doped Al 2O 3SiO 2 glass single-mode fibers. A wide range of rare earth doping concentrations was successfully introduced into fibers using this technique. In the sol-gel dipcoating to deposit a thick film, the key to achievement of low loss fiber was found to depend critically on a process capable of providing a consistently crack-free film.

Flash-condensation technique for the fabrication of high-phosphorus-content rare-earth-doped fibres

A novel technique for fabricating optical fibres with a uniformly high concentration of rare-earth dopants is described. Controllable doping of up to 17 mol% (33 wt%) P2O5 has been achieved in conjunction with up to 3 mol% (14 wt%) of rare-earth oxide. The performance of the fibres as fibre amplifiers is discussed.

Epitaxial growth of garnets for thin film lasers

Liquid phase epitaxial techniques have been developed for the preparation of thin films of optical materials. Heteroepitaxy of magnetic garnets on nonmagnetic garnet substrates by the dipping technique employs the phenomenon of stable supersaturation in the iron garnet-PbO:B2O3 system. Rare earth aluminum garnets in the same flux supersaturate to a lesser extent and precipitate readily upon substrate insertion. High quality films of YAG:Nd and YAG:Yb,Er,Tm,Ho on pure YAG as well as pure YAG on YAG:Nd have been prepared from a saturated PbO:B2O3+ flux using a transfer technique. Laser oscillation of Ho3+ at 2.1μm and Nd3+ at 1.06μm in single crystal epitaxial films prepared by the transfer technique have been reported by van der Ziel et al. Solute transfer has the advantage in optic garnet systems of uniform film growth at constant temperature without spontaneous nucleation. In addition, continuous solution of uniform composition nutrient maintains the rare earth dopant concentration in the melt. Pb incorporation results in a brown discoloration but can be eliminated by the proper choice of growth temperature. Deposition rates between 2 μm and 6 μm/hr. at ∼1O00°C have been found satisfactory. In this paper melt preparation, furnace design, the effect of impurities on threshold, and the effects of lattice mismatch and substrate orientation will be discussed.