[Characterization of Nd Doped Films Prepared by Femtosecond Pulsed Laser Deposition].

Thin films of Nd:YAG and Nd:Glass were prepared on Si(100) substrate by pulsed laser deposition technology. The morphology of film surface and cross section, composition, absorption spectrum and photoluminescence (PL) spectra of films were investigated by scanning electron microscope (SEM), energy disperse spectroscopy (EDS), Fourier transform infrared spectrometer (FTIR), optical parametric oscillator (OPO) and grating spectrometer. The results show that both Nd:YAG films and Nd:Glass films grown on the substrates at room temperature are amorphous. Nd:YAG films grown by PLD contain Nd element with 0.15 at. % stoichiometric proportion. The absorption spectrum of bulk Nd:YAG target rather than deposited films exhibit two absorption peaks at 750 and 808 nm. There are no evident peaks in the photoluminescence spectra curve of Nd:YAG films. However, the photoluminescence spectra of Nd:Glass films with two sharp peaks at the wavelength of 877 and 1064 nm are observed. It indicates that Nd is doped into glass host as optically active Nd(3+) ions when Nd:Glass films grow at room temperature. But for Nd:YAG films, Nd don't incorporate into YAG host as Nd(3+) ions.

[Spatial localized distribution of modes in two-dimension random medium].

Based on the time dependent theory, FDTD algorithm was used to numerically solve Maxwell's equations and rate equations. By dividing the two-dimension random medium, the emission spectra of different region under different pumping intensities were obtained. The calculated results show that the emission spectra of different region are different, the energy of emission is mainly distributed in some certain region, and the pumping efficiency is different. Also spatial extent overlap of modes is reproduced. With this method, the dependence of random distribution on lasing can be analyzed and it should be useful for the preparation of pseudo-random medium.