J. J. Romero

Comparison of optical spectra of Nd3+ in NdAl3(BO3)4 (NAB), Nd:GdAl3(BO3)4 (NGAB) and Nd:Gd0.2Y0.8Al3(BO3)4 (NGYAB) crystals

A comparative study of the optical absorption and luminescence of crystals of NdAl3(BO3)4 (NAB), Nd:GdAl3(BO3)4 (NGAB) and Nd:Gd0.2Y0.8Al3(BO3)4 (NGYAB) is presented. The Judd-Ofelt theory is applied to the fitting of experimental absorption line strengths to obtain the intensity parameters Ωt (t = 2,4,6) with root mean square errors of 11.8%, 3.8% and 8.6% for NAB, NGAB and NGYAB respectively. The intensity parameters are used to calculate the radiative transition rates, branching ratios and radiative lifetimes of Nd3+ ions undergoing transitions from 4F3/2 to 4IJ manifolds. The relevant spectroscopic parameters for laser applications (quantum efficiency and emission cross section) are also estimated. The results are compared among the three samples and other borate crystals. It is concluded that NAB is a laser crystal with high gain and thus a promising candidate for microchip laser application, while NGAB (or NGYAB) can be used as an alternative to the celebrated nonlinear laser crystal NYAB.

Increase of the 800 nm excited Tm3+ blue upconversion emission in fluoroindate glasses by codoping with Yb3+ ions

Intense Tm3+ blue upconversion emission has been observed in Tm3+–Yb3+ codoped fluoroindate glasses under direct excitation into Tm3+ ions with a diode laser at 796 nm. The dependence of the intensity of this upconversion emission on the Tm3+ and Yb3+ concentration has been studied in order to determine the optimum ion concentrations and the involved mechanisms. The blue upconversion emission is highly increased with the Yb3+ concentration. For fixed Yb3+ concentrations, the maximum upconversion efficiency was obtained with Tm3+ concentration of about 0.5 mol%. For this optimum Tm3+ concentration, the upconversion emission intensity is increased by a factor about 100 by codoping with 2.25 mol% of Yb3+. The results are well explained by a proposed rate equation model.

Diffuse multiself-frequency conversion processes in the blue and green by quasicylindrical ferroelectric domains in Nd3+:Sr0.6Ba0.4(NbO3)2 laser crystal

In this letter we demonstrate continuous-wave blue and green diffuse laser light generation from a Nd3+-doped Sr0.6Ba0.4(NbO3)2 crystal located in an end-pumped laser cavity and operating at the 4F3/2→4I11/2 laser channel. The diffuse nature of the visible radiation is attributed to numerous ferroelectric cylindrical domains, which appear in the as-grown crystal. Green radiation is obtained by self-frequency doubling of the infrared radiation, whereas tunable blue radiation is generated by self-frequency sum mixing of infrared and pump radiations. The variety of visible colors is due to the spread in the domain sizes. Finally, we report on the spectral and spatial distribution of this visible radiation.

Simultaneous generation of coherent light in the three fundamental colors by quasicylindrical ferroelectric domains in Sr0.6Ba0.4(NbO3)2

Continuous-wave red, green, and blue coherent light has been simultaneously generated by quasiphase matching in a strontium barium niobate crystal used as an intracavity frequency converter of a Nd:YVO4 laser operating at 1.34 μm. The broad distribution of ferroelectric domain sizes (1–8 μm) provides the possibility of different simultaneous frequency conversion processes without requiring angle or temperature tuning. Blue and red colors were generated by second-harmonic generation of pump (0.88 μm) and infrared (1.34 μm) laser radiation, respectively. Green light was produced by sum frequency mixing of pump and laser radiations.

Spectroscopic and laser properties of Nd3+ in SBN

Abstract In this paper we report the main spectroscopic and laser properties of Nd 3+ -doped strontium barium niobate, Sr x Ba 1− x Nb 2 O 6 ( x =0.6). Broad luminescence bands have been observed as a result of the high disorder of the crystal, whose shape is insensitive to temperature. Continuous wave laser action has been demonstrated at 1.06xa0μm with a slope efficiency of 37%. In addition, intracavity diffuse green laser light has been generated from this crystal by self-frequency doubling the 1.06xa0μm infrared line of Nd 3+ ions.

Luminescence of trivalent rare earth ions in the yttrium aluminium borate non-linear laser crystal

Single crystals of YAl 3 (B0 3 ) 4 doped with the rare earth ions Sm 3+ , Eu 3+ , Tb 3 +, Dy 3+ ,Tm 3+ and Yb 3 * were grown using the flux growth technique. Luminescence spectra and decay curves were recorded in the visible range at room and low temperatures. The observed transitions were assigned and analysed on the basis of group theory for the D 3 point symmetry. Evidence for the presence of non-equivalent centres has been found for Yb 3+ and possibly for Sm 3+ and Dy 3+ doped crystals.

Influence of neodymium concentration on the cw laser properties of Nd doped Ca3Ga2Ge3O12 laser garnet crystal

Spectral and laser properties of Nd3+ doped Ca3Ga2Ge3O12 have been investigated for different Nd concentrations ranging from 0.1 to 16 atu200a%. The 4F3/2→4I11/2 emission spectrum is dominated by two main peaks at 1060 and 1065 nm whose stimulated emission cross sections change with Nd concentration. For concentrations above 0.5% luminescence quenching begins. Then, continuous wave laser gain experiments have been used to investigate the influence of these effects on the laser properties. The different factors (crystal losses and saturation intensity factor) contributing to the increase observed in the laser pump threshold with Nd concentration are discussed. Analysis of the laser spectra shows a double laser oscillation around 1060 and 1065 nm, which tends to disappear for high Nd concentrations.

Red and green fluorescence of Mn2+ in NaCl

Abstract The fluorescence (emission and excitation) spectrum of Mn 2+ ion in NaCl has been investigated for freshly quenched samples (diluted Mn 2+ ions) and as grown samples (Mn 2+ ions forming aggregates and/or precipitates). Two main emission bands are generally observed in as grown samples, peaking at 505 nm and around 610 nm. Both emission bands are related to different manganese precipitates. Quenched samples show only the red emission but peaking at 605 nm and with a different excitation spectrum to that of the as grown crystals. Thus, this crystal is suitable to operate as a double color (red and green) emitting phosphor where the red and green relative intensities can be controlled by a thermal treatment.

Multiwavelength laser action of Nd3+:YAlO3 single crystals grown by the laser heated pedestal growth method

Abstract We describe the growth of high quality transparent fibers of pure and Nd-doped YAlO3 from unreacted pedestals (green rods) by the laser heated pedestal growth technique. The X-ray diffraction analysis shows that the fibers are monocrystalline, with a distorted Pnma perovskite structure and grow along 〈0 1 0〉 direction (b axis). In this work, multi-wavelength laser action is demonstrated for these fibers in the two main laser channels of Nd3+ ions. In the 4F3/2xa0→xa04I11/2 laser transition, low threshold multi-wavelength laser emission is obtained at wavelengths of 1065, 1073 and 1081 nm. Additionally, for the first time in LHPG grown YAlO3 fibers, laser action in the 4F3/2xa0→xa04I13/2 transition is demonstrated at a wavelength of 1341 nm.

Stimulated emission, excited state absorption, and laser modeling of the Nd3+:Ca3Ga2Ge3O12 laser system

We report on a full spectroscopic characterization of the Nd3+ ion doped Ca3Ga2Ge3O12 garnet laser host for different ion concentrations ranging from 2.5×10−2 up to 2 at.u200a%. The Judd–Ofelt formalism has been applied, from which the stimulated emission cross section corresponding to the 4F3/2→4I11/2 laser channel has been determined. Excited state absorption cross section in the 1020–1090 nm region has been measured by using two beam spectroscopy, demonstrating that the 1060 and 1065 nm laser emissions are not affected by excited state absorptions. Finally, once the basic parameters are known, we have applied the mode overlap formalism in order to determine the Nd3+ concentration and crystal length which optimize the laser performance of an end diode pumped laser system. We have concluded that the maximum output power is reached when the Nd3+ concentration and crystal length are around 0.75 at.u200a% and 0.6 mm, respectively