F. Cussó

Temperature Sensing with Up-Converting Submicron-Sized LiNbO3:Er3+/Yb3+ Particles

We present the temperature dependence of the green up-converted luminescence in submicron-sized LiNbO3:Er3+/Yb3+ particles in the range between 12 and 180 °C. It is shown that LiNbO3:Er3+/Yb3+ exhibits a very high sensitivity (S = 0.007/°C at physiological temperature and a maximum value of S = 0.014/°C at 350 °C) that surpasses those previously found for other materials based on Er3+/Yb3+ luminescence, indicating that LiNbO3:Er3+/Yb3+ is a suitable probe for optical temperature sensing through the fluorescence intensity ratio technique. This high sensitivity can be explained using the intrinsic spectroscopic parameters of Er3+ ions in this host.

Red, green, and blue simultaneous generation in aperiodically poled Zn-diffused LiNbO3:Er3+/Yb3+ nonlinear channel waveguides

In this work, continuous-wave broadly tunable simultaneous generation of red (650–690 nm), green (520–575 nm), and blue (425–495 nm) light in aperiodically poled Zn-diffused LiNbO3:Er3+/Yb3+ channel waveguides is reported after Ti:sapphire excitation in the 850–990 nm range. The red and green emissions arise from energy transfer and upconversion mechanisms between Yb3+ and Er3+ ions, while the blue light with a maximum efficiency of 0.04% W−1 cm−1 is produced by quasi-phase matching processes.

POLARIZATION EFFECTS ON THE LINE-STRENGTH CALCULATIONS OF ER3+-DOPED LINBO3

The polarized optical absorption of Er3+-doped LiNbO3 has been obtained and analyzed within the framework of the Judd-Ofelt theory including polarization dependences. These results are compared with those obtained under unpolarized conditions. Fluorescence lifetimes for different Er3+ concentrations have also been measured in the temperature range 10–300 K.

Yb3+ to Er3+ energy transfer in LiNbO3

The energy transfer between and ions in lithium niobate is investigated and modelled using the rate equation formalism. An efficient energy transfer from to is found and the transfer and back-transfer coefficients have been determined ( and , respectively). Using the rate equation formalism it is shown that population inversion of the level (upper laser level at ) is attainable at sufficiently low pumping levels, making this material suitable for laser applications. The effective transfer efficiency is also calculated, showing good agreement with the experimental values obtained from the increase of the emission.

Single polarized Tm3+ laser in Zn-diffused LiNbO3 channel waveguides

In this work, laser operation at 1.76μm in Tm3+:LiNbO3 Zn-diffused channel waveguides is reported. The laser emission is single polarized with the electric field parallel to the optic axis(π-polarization) and operates in continuous-wave regime, at room temperature. The threshold of laser oscillation is in the range of 40mW, the slope efficiency is around 1%, and both magnitudes are dependent on the channel width, in accordance with the mode overlap between the pump and signal modes within the waveguides.

Concentration Dependence of the 1.5 μm Emission Lifetime of Er3+ in LiNbO3 by Radiation Trapping

The lifetime of the 1.5 μm transition of Er 3+ doped LiNbO 3 has been measured for different doping concentrations and geometries of luminescence collection. It has been found that this emission suffers of a strong radiation trapping effect, which affects the measured lifetime depending on the concentration and the geometry adopted.

Site-selective spectroscopy of Nd3+ in LiNbO3:Nd and LiNbO3:Nd, Mg crystals

Site-selection spectroscopy techniques have been used to investigate the different Nd3+ crystal-field sites appearing in LiNbO3:Nd3+ and LiNbO3:Nd3+, Mg2+ crystals. Singly doped crystals show the presence of two nonequivalent sites for Nd3+ (here labelled as Nd-1 and Nd-2 sites). Codoping the crystals with Mg2+ ions induces the presence of a new Nd3+ site (labelled as Nd—Mg site) concomitant with fewer Nd-1 sites. These three crystal-field sites have been optically characterized by their highest-energy emission peak of the 4F3 → 4I92 transitions. The possible location for these sites is the host matrix is discussed.

Optical absorption and luminescence of Tm3+-doped LiNbO3 and LiNbO3 (MgO) crystals

The optical properties (absorption, luminescence and lifetime) of Tm3+-doped LiNbO3 and LiNbO3(MgO) have been measured. It has been found that the 1D2, 1G4, 3H4 and 3F4 levels decay radiatively having temperature-independent lifetimes. These results are compared with the radiative transition rates calculated by using the Judd-Ofelt theory. It has also been found that MgO-codoping affects very slightly the optical properties of Tm3+ ions, except for a general broadening of the spectra. Oscillator strenghts and Judd-Ofelt parameters are not affected by MgO codoping.

Europium-doped alkali halides as a selective ultraviolet dosimeter material in the actinic region

The NaCl:Eu2+ thermoluminescence characteristics after ultraviolet irradiation as well as solar exposure have been analyzed. The TL excitation spectra of this material is coincident with the actinic region and its sensibility limit is less than 0.2 μJ/cm2 for 240 nm wavelength irradation. A model for the thermoluminescence emission is provided.

Optical Detection of Ion Impurity Sites in Doped LiNbO3

In this work the site location of several M[sup 3+] (m[equals]Cr, Nd, Eu, Ho, Er, Tm) dopant ions in LiNbO[sub 3] has been investigated by using optical (absorption and site-selective fluorescence) techniques. Experimental results reveal that the regular cation sites, Li[sup +] and Nb[sup 5+], are occupied in all cases and can be characterized optically. Additional crystal field sites, for M[equals]Nd and M[equals]Eu, have been detected by site selective spectroscopy. The effects on the M[sup 3+] optical spectra of the stoichiometry and the codoping with MgO have been systematically investigated. The appearance of new sites for the M[sup 3+] ions, M[sup 3+] [minus]Mg[sup 2+], is ascertained for M[equals]Cr, Nd, Ho, Ho, and Tm.