I. Iparraguirre

Laser action and upconversion of Nd3+ in lead–niobium–germanate bulk glass

Abstract Laser action together with upconversion processes which produce green, orange, and red emissions in Nd 3+ -doped lead–niobium–germanate bulk glass (60GeO 2 –25PbO–15Nb 2 O 5 ) have been investigated. The upconversion processes were conducted in such a way that the dynamics of the visible fluorescence was analyzed under lasing and non-lasing conditions. The features present in the time resolved upconverted emission show the existence of excited state absorption of both pump radiation and laser emission.

On the origin of bichromatic laser emission in Nd 3+ -doped fluoride glasses

In this work we present a detailed study about the influence of the host matrix in the spectroscopic and laser properties of Nd3+ in three different fluoride glasses. Site-selective time-resolved techniques have been used to investigate the crystal field changes felt by the Nd3+ ion as a consequence of glass inhomogeneity. Stimulated emission experiments performed under selective wavelength laser pumping show the existence of bichromatic emission from two distinguishable site distributions for Nd3+ in fluoride glasses. This result can be explained by the moderate inter-site energy transfer among Nd3+ ions found in these systems.

Nd3+ laser spectral dynamics in CaF2-YF3-NdF3 crystals

Abstract A spectral and dynamical study of the spontaneous and stimulated emissions of the yttrofluorite crystal CaF 2 –YF 3 (5%)–NdF 3 (2%) which proves the existence of two main sites for the rare earth ion is presented. Flash-lamp pumped laser experiments show the existence of two laser output lines centred at 1054 and 1063 nm which do not coincide with the spectral position of two of the resolved sites. The dependence of the time-resolved laser output energy and relative intensities of both lines on the pump energy suggests the existence of some kind of coupling among both emissions produced by the stimulated emission field itself.

Spectral study of the stimulated emission of Nd 3+ in fluorotellurite bulk glass

In this work we present, for the first time to our knowledge, laser emission under wavelength selective laser-pulsed pumping in Nd(3+)-doped TeO(2)-ZnO-ZnF(2) bulk glass for two different Nd(3+) concentrations. The fluorescence properties of Nd(3+) ions in this matrix which include, Judd-Ofelt calculation, stimulated emission cross-section of the laser transition and lifetimes are also presented. The site-selective emission and excitation spectra along the (4)I(9/2)→(4)F(3/2) absorption band show the inhomogeneous behaviour of the crystal field felt by Nd(3+) ions in this fluorotellurite glass which allows for spectral tuning of the laser output pulse as a function of the pumping wavelength. The emission cross-section obtained from the Judd-Ofelt analysis and spectral data (4.9x10(-20) cm(2)) is in fairly good agreement with the value obtained from the analysis of the laser threshold data (4x10(-20) cm(2)).

Random lasing in Nd:LuVO4 crystal powder

Room temperature random lasing action is demonstrated for the first time in a low concentrated neodymium doped vanadate crystal powder. Laser threshold and emission efficiency are comparable to the ones obtained in stoichiometric borate crystal powders. The present investigation provides a complete picture of the random lasing characteristics of Nd-doped vanadate powder both in the spectral and temporal domain, together with a simplified model which accounts for the most relevant features of the random laser.

Laser action in Nd 3+ -doped lanthanum oxysulfide powders

We have investigated the stimulated emission properties of Nd(3+) doped La(2)O(2)S powders at room temperature as a function of pumping energy density, excitation wavelength, and Nd(3+) ion concentration. The absolute stimulated emission energy has been measured. Expressions for the slope efficiencies and lasing thresholds as a function of rare earth concentration and pumping wavelengths, which qualitatively agree with experimental observations, are discussed.

Spontaneous and stimulated emission spectroscopy of a Nd 3+ -doped phosphate glass under wavelength selective pumping

The influence of the host matrix on the spectroscopic and laser properties of Nd(3+) in a K-Ba-Al phosphate glass has been investigated as a function of rare-earth concentration. Site-selective time resolved laser spectroscopy and stimulated emission experiments under selective wavelength laser pumping show the existence of a very complex crystal field site distribution of Nd(3+) ions in this glass. The peak of the broad stimulated (4)F(3/2)→(4)I(11/2) emission shifts in a non monotonous way up to 3 nm as a function of the excitation wavelength. This behavior can be explained by the relatively moderate inter-site energy transfer among Nd(3+) ions found in this system and measured by using fluorescence line narrowing spectroscopy. The best slope efficiency obtained for the laser emission was 40%.

Time resolved spectroscopy of laser output of Nd3+ doped calcium, niobium, gallium garnet

Abstract Stimulated emission experiments in the 4 F 3 2 → 4 I 11 2 transition of Nd3+ in Ca3(GaNb)3O12 show that two laser lines are emitted simultaneously and both independently. These experiments show the behaviour of the laser emission from two distinguishable subsets of Nd3+ sites. This behaviour has been modeled using a four-level spectral rate-equation laser model, assuming the existence of two kinds of Nd3+ populations with different emission spectra and a homogeneous line broadening at each site. The model explains the measured laser spectrum as well as the time delay between the emission of both laser lines.

Effects of pumping wavelength and pump density on the random laser performance of stoichiometric Nd crystal powders.

Laser slope and threshold properties have been investigated in Nd stoichiometric crystal powders as a function of pump wavelength and pump beam size. Above a given pumped area, the laser slope and the threshold pump energy per unit area are invariant and the known theoretical expressions are well fulfilled. Likewise, the size of the stimulated emission zone as a function of the pump beam area has been measured, also showing a different behavior above or below a given pumped area value which coincides with the one mentioned above. In conclusion, two different operating regimes with different performances are clearly observed as a function of the pump beam area.

On the temporal behavior of Nd 3+ random lasers

The temporal dynamics of random laser emission from Nd-doped crystal powders has been investigated by using an improved detection device. The precise conditions to detect high contrast, fast oscillations are described. The measured period is about one order of magnitude shorter than the one given in the literature for relaxation oscillations in these materials. The origin of these differences is discussed.