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Steady-state and time-resolved laser spectroscopies are used to investigate the energy transfer between Cr(super 3+) and Nd(super 3+) ions in Cr(super 3+), Nd(super3+):YAl3(BO3)(sub 4) (YAB) codoped crystals. The analysis has showed that 80% of the Cr(super 3+) forward arrow Nd(super 3+) energy transfer in YAB has taken place without the assistance of lattice phonons whereas almost 20% has taken place through multiphonon emission.

Spectroscopic measurements were used to undertaken a systematic optical characterization of the NdA13(BO)3 (NAB) crystal.

The spectroscopic and laser properties of neodymium-doped yttrium aluminium borate are examined.

Nd3+ doped Ca3Ga2Ge3O12 spectral and laser properties were studied for different Nd concentrations.

UV laser radiation is shown to be produced using Nd3+:YAB crystals and argon laser end-pumped cavities.

The impact of temperature on the controlling of the local devitrification process taking place in an oxyfluoride glass doped with [Er.sup.3+] ions under diode laser irradiation is analysed. The formation of nanocrystals due to the observed laser action is also discussed.

The thermal stability of both structural and optical micromodifications generated by ultrafast laser written filaments in sapphire crystals is reported. The results provide insight into the waveguides generated by the strain stress induced refractive index increment based on the dominant electronic polarizability enhancement.

The fabrication and microspectroscopy imaging of femtosecond laser written double-filament based [Nd.sup.3+]:MgO:LiNb[O.sub.3] optical waveguides is described. The lattice structural micromodifications at the origin of both waveguide formation and [Nd.sup.3+] fluorescence changes are examined by using confocal micro-Raman experiments.

The thermal diffusion of neodymium ions was used for the confocal microspectroscopic characterization of planar optical waveguides fabricated in yttrium vanadate (YV[O.sub.4]) crystals. The results obtained from the analysis of spatial dependence of the [Nd.sup.3+] fluorescence provide insight into the spatial distribution of the fluorescence quenching and spectral shift and the mechanism responsible for the refractive-index modification and waveguide formation.

The laser performance of poled and unpoled neodymium-doped strontium barium niobate crystals is analyzed and compared. The optical distortion effects induced by both poled and unpoled crystals have shown that the compensation effects taking place between adjacent microdomains inside the active volume are the origin of this improvement.

The anisotropic thermal lens (TL) effect is analyzed in [Nd.sup.3+] doped [Sr.sub.x][Ba.sub.1-x][Nb.sub.2][O.sub.6] crystals with two different stoichiometries. The results have shown a strong enhancement in the TL effect during the ferro-to-paraelectric phase transition and an inversion of the TL signal with the crystal stoichiometry.

The origin of the phase transition induced gain depression in diode pumped [Nd.sup.3+] doped [Sr.sub.0.6][Ba.sub.0.4][(Nb[O.sub.3]).sub.2] lasers is investigated. The mechanisms capable of intracavity beam distortions are discussed and evidence is provided for two effects, a phase transition induced polarization switching and an enhancement in the laser performance when phase transition is overcome.

The effects of femtosecond laser ablation in Nd:SBN crystals and the induced micromodifications are analyzed. The spatial extension of the luminescence inhibition is analyzed as a function of the laser fluence in order to elucidate the origin of the femtosecond laser induced material amorphization.

The depth-resolved micromodification of single-crystalline femtosecond laser irradiated [Nd.sup.3+] doped MgO:LiNb[O.sub.3] crystals are examined with the use of micro-Raman and microluminescence experiments. The analysis of Raman and fluorescence bandwidths has indicated that a slight lattice disorder and densification is induced by femtosecond laser irradiation.

The continuous-wave tunable laser light generation from a diode-pumped Nd(super 3+) - doped Ba2NaNb5O15 nonlinear crystal is presented. The characteristic cationic disorder of this system leads to a broad emission band allowing for continuous wavelength selection in the infrared and in the green through self-frequency doubling.

The spectral properties of Yb(super 3+) ions in Strontium barium niobate (SBN ) nonlinear crystal were investigated and compared ytterbium doped crystals. The obtained results make this crystal a promising candidate for tunable laser generation in the visible domain.

Low temperature site-selective laser spectroscopy analyzes the Neodyminium(super 3+) multicenter distribution in a Ca(sub 3)Sc(sub 2)Ge(sub 3)O(sub 12) garnet laser crystal. The effect of codoping the crystal with Magnesium oxide on the Neodyminium(super 3+) center distribution was investigated wherein three different centers were observed.

Quasiphase-matching second-harmonic-generation experiments are performed on the Nd(super 3+) doped strontium barium niobate multiself-frequency-converter nonlinear crystals. A broad distribution of domain sizes is obtained and this gives the possibility of broadband second-harmonic generation in the 800-1200 nm range.

Infrared laser gain experiments under diode pumping is performed on NCGC crystals with different ion concentrations. A combination of second harmonic and frequency mixing processes is used to explain the spectral and spatial characteristics of green radiation.

A full spectroscopic characterization of the Nd(super 3+) ion doped Ca3Ga2Ge3O12 garnet laser host for different ion concentrations is reported. The mode overlap formalism results show that the maximum output power is reached when the Nd(super 3+) concentration and crystal length are around 0.75 at.% and 0.6 mm, respectively.

Magneto-optic (MO) studies are performed on regular arrays of Fe(100) micrometric squares, where the elements are patterned with different sizes and separations. Nonspecular measurements serve to determine when the magnetization within the micro squares reaches a homogeneous distribution.