M. Voda

Anti-Stokes laser cooling in Yb 3+ -doped KPb 2 Cl 5 crystal

We report internal laser cooling in Yb(3+) -doped KPb(2)Cl(5) . From the quantum efficiency values measured in the heating and cooling regions by use of the photothermal deflection technique, we have obtained a room-temperature cooling efficiency of 0.2% in a sample doped with ~5x10(19)ions/cm(3) . Excitation spectra obtained under high irradiation fluences show an excess of fluorescence with regard to those obtained at low fluences, which agrees with the prediction of a model based on photon-ion-phonon interaction.

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.

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.

Infrared to visible upconversion in Pr3+-doped KPb2Cl5 crystal

Abstract In this work we report the infrared to visible upconversion luminescence in the low phonon-energy host material KPb2Cl5 doped with Pr3+ ions. A strong orange luminescence from the 1D2 level, and less intense blue, green, and red emissions from the 3P0,1 levels have been observed under infrared excitation inside the 1G4 level and compared with those obtained under one photon excitation. The upconverted fluorescence from the 1D2 level shows a quadratic dependence on the pump power indicating a two photon process, whereas the pump power dependence of the blue fluorescence from level 3P0 is nearly cubic, which indicates a three photon mechanism. The possible excitation mechanisms responsible for these upconversion processes are discussed.

Laser properties of Nd3+ in K5Nd(MoO4)4 stoichiometric disordered crystal

Abstract The spectroscopic and laser properties of K5Nd(MoO4)4 crystal have been thoroughly investigated to show the relationship between the optical properties of Nd3+ ions and the crystal structure. High-resolution site-selective excitation spectroscopy performed at low temperature has demonstrated the existence of two broad crystal field site distributions for Nd3+. In agreement with this result, a broad laser emission has been observed. The shape and width of the laser line strongly depend on the polarization of the pump pulse. The temporal evolution of the laser spectrum shows remarkable changes in its spectral structure.

Self-frequency tuning in birefringent K5Nd(MoO4)4 laser crystal

Abstract In this paper we report an experimental demonstration of broadband wavelength self-tuning in K5Nd(MoO4)4 laser crystal (KNM) together with a theoretical treatment of the system based on its birefringence properties. The self-frequency tuning in KNM was obtained by inserting an a-cut plate inside the resonator at Brewster’s angle. At a given position of the crystal plate, when the wavelength of the oscillating mode corresponds to an integral number of full-wave retardation in the plate, the laser operates in the p polarization of the Brewster surface with no losses. The experimental self-frequency tuning of the laser emission along the free spectral range of the KNM crystal was obtained by rotating the birefringent gain plate in its own plane. To investigate the tuning characteristics of the spectral filter, we have used the Jones-vector formalism. The calculated wavelength-selective tuning matches very precisely the experimental observations. As far as we know this is the first time the grounds and operation of such a device is demonstrated.

Site-selective time-resolved laser spectroscopy of Eu3+ in K5Bi1−xEux (MoO4)4 crystals

Abstract Time-resolved resonant fluorescence line narrowed 5D0 → 7F0, 1, 2 emission spectra of Eu3+ in K5Bi1−xEux(MoO4)4 crystals show the existence of two broad crystal field site distributions for Eu3+ ions. The lifetime behaviour suggests the presence of a fast transfer process between Eu3+ ions.