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In this paper, we present an iterative method which merges experimental μ-Raman measurements and numerical simulations to describe femtosecond written waveguides in LiNbO3 crystals. This method is based on the deformation potential theory, and uses the finite element method to analyze elastic deformations after femtosecond laser micro-explosions in x-cut Mg:LiNbO3 crystals. The resultant strain and refractive index field after laser interaction were estimated and yielded similar values to those obtained in other works. The LiNbO3 Raman deformation potential constants were also estimated in this work. [ABSTRACT FROM AUTHOR]

We report on the thermal stability of both structural and optical micromodifications created by ultrafast laser written filaments in sapphire crystals. By using the Cr3+ traces as optical probes, we have concluded that the filaments are constituted by both reversible and nonreversible defects with very different spatial locations. The strain field measured from the analysis of R lines has been found to be erased at the same time when the reversible centers are recombined (∼1100 °C). This fact seems to indicate that these defects act as pinning centers for the induced stress. Furthermore, we have found that the waveguide generated in the proximity of the filament disappear for annealing temperatures above 1100 °C. This clearly supports the assumption that waveguiding is produced by the strain stress induced refractive index increment based on the dominant electronic polarizability enhancement. [ABSTRACT FROM AUTHOR]

We report on the confocal microspectroscopic characterization of planar optical waveguides fabricated in yttrium vanadate (YVO4) crystals by thermal diffusion of neodymium ions. We have found that the waveguide formation is accompanied by Nd3+ fluorescence quenching and by a redshift of the Nd3+ sub-Stark transitions. These effects have been explained in terms of the high Nd3+ concentrations achieved close to the diffusion surface, which lead to the appearance of nonradiative processes, as well as to a local compression in the surroundings of the indiffused Nd3+ ions. By comparing with previous works, we have estimated an equivalent residual stress of 0.1 GPa. The possible mechanisms at the origin of waveguide formation have been also discussed. [ABSTRACT FROM AUTHOR]

We report on femtosecond laser modification of Nd:SBN crystals. Basic properties such as the ablation threshold have been obtained from the analysis of the ablation depths at different laser fluences. The induced micromodifications have been investigated by optical microscopy as well as by microphotoluminescence and micro-Raman experiments. We have found that in the vicinity of the ablated volume material amorphization can be induced along different directions. Furthermore, we have found that this material amorphization is accompanied by a strong inhibition of the Nd3+ luminescence. The analysis of the spatial extension of the luminescence inhibition as a function of the laser fluence has been used to elucidate the origin of the femtosecond laser induced material amorphization. [ABSTRACT FROM AUTHOR]

In this work the origin of the phase transition induced gain depression in diode pumped Nd3+ doped Sr0.6Ba0.4(NbO3)2 lasers has been systematically investigated. The mechanisms capable of intracavity beam distortions are discussed and their relative contribution to the gain depression is investigated. We also provide evidence of two effects: a phase transition induced polarization switching and an enhancement in the laser performance when phase transition is overcome. [ABSTRACT FROM AUTHOR]

The temperature dependence of the Nd3+→Yb3+ energy-transfer rate in the YAl3(BO3)4 nonlinear laser crystal has been investigated from the analysis of fluorescence decay curves recorded in the 10–600 K range. Three different regimes, independent on the dopant concentration, have been observed in the thermal behavior of the Nd3+→Yb3+ energy-transfer rate. By comparing experimental results with theoretical predictions based on the Dexter model [J. Chem. Phys. 21, 836 (1953)], the origin of these different regimes has been explained. In addition, the influence of temperature and of both Nd3+ and Yb3+ concentrations on the Nd3+←Yb3+ energy back-transfer rate has been also investigated, concluding that it is a migration-assisted energy-transfer process. Finally, the populations of both Nd3+ and Yb3+ metastable states achieved after continuous-wave Nd3+ excitation have been calculated and measured and results have been explained in terms of the thermal behavior of both forward- and back-transfer rates. [ABSTRACT FROM AUTHOR]

A first spectroscopic characterization of Yb3+ ions in Sr0.6Ba0.4(NbO3)2 nonlinear crystal is presented. From low temperature emission and absorption spectra the energy level diagram of Yb3+ ions in this crystal has been built up. The ground state splitting has been found to be as high as 940 cm-1 allowing for potential quasi-four-level laser operation. In order to assess the ability of this system as a tunable solid state laser the main parameters of relevance in laser dynamics have been obtained and compared to those reported for other Yb3+ doped lasers. Optical microscopy has been used to study the ferroelectric domains appearing in the as-grown crystals. A relatively broad distribution of domain sizes (around 3 μm) will, in principle, allow for broadband noncritical second-harmonic generation of fundamental radiation by quasiphase matching. The obtained results make this crystal a promising candidate for tunable laser generation in the visible domain. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The Nd[sup 3+] multicenter distribution in a Ca[sub 3]Sc[sub 2]Ge[sub 3]O[sub 12] garnet laser crystal has been analyzed by low temperature site-selective laser spectroscopy. Two nonequivalent Nd[sup 3+] centers have been identified and characterized in this host lattice. The effect of codoping the crystal with MgO on the Nd[sup 3+] center distribution has also been investigated, since this codoping enables considerable enhancement of the doping levels of these crystals. Three different centers were observed in the codoped crystals, together with a reduction of inhomogeneous emission broadening. The nature of the optical centers present in both cases is discussed by considering the charge compensation mechanisms involved in accommodation of Nd[sup 3+] ions. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A diode-end-pumped intracavity frequency doubled Nd[sup 3+]:Ca[sub 3]Ga[sub 2]G[sub 3]O[sub 12]/KTiOPO[sub 4] green laser is demonstrated. The infrared laser output and pump-to-green conversion efficiency have been investigated as a function of crystal length and Nd[sup 3+] concentration. Results show that optimum ion concentration is around 2-3 at. %, in excellent agreement with theoretical predictions. Due to the broad absorption bands of this crystal, output power does not depend on diode temperature within a 12 °C range. The influence of Nd[sup 3+] concentration on the [sup 4]F[sub 3/2] quantum efficiency has been also analyzed. We have found that for optimum ion concentration quantum efficiency is as high as 0.7. Finally, the spectral distribution of green light is explained in terms of a combination of both second harmonic and frequency mixing processes between the two infrared oscillating lines. [ABSTRACT FROM AUTHOR]

We report on a full spectroscopic characterization of the Nd[sup 3+] ion doped Ca[sub 3]Ga[sub 2]Ge[sub 3]O[sub 12] garnet laser host for different ion concentrations ranging from 2.5×10[sup -2] up to 2 at. %. The Judd–Ofelt formalism has been applied, from which the stimulated emission cross section corresponding to the [sup 4]F[sub 3/2]→[sup 4]I[sub 11/2] 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 Nd[sup 3+] 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 Nd[sup 3+] concentration and crystal length are around 0.75 at. % and 0.6 mm, respectively © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Magneto-optic (MO) studies are performed on regular arrays of Fe(100) micrometric squares, where the elements are patterned with different sizes (2.5–10 μm) and separations (0.2–0.6 μm). When a laser beam is focused inside the patterned structure a Bragg diffraction pattern is produced allowing MO studies on both reflected and diffracted spots. The magnetic anisotropy has been analyzed by in-plane MO hysteresis loops finding that, for square sizes below 2.5 μm, it is not consistent with the Fe crystalline cubic anisotropy, presenting a uniaxial-like behavior. The magnitude of the corresponding anisotropy constants has been determined by analyzing the array response (on reflected and diffracted spots) to a rotational magnetic field in a magneto-optical torque setup. For square sizes of 10 μm the anisotropy induced by patterning is negligible whereas for the small squares (2.5 μm) the uniaxial magnetic constant has been found to be roughly 0.2 times the Fe cubic anisotropy constant. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this work a systematic optical characterization of the NdAl[sub 3](BO[sub 3])[sub 4] (NAB) crystal has been carried out by means of spectroscopic measurements. The energy levels (118) of the Nd[sup 3+] constituent ions have been identified and labeled by appropriate crystal field quantum numbers (μ=1/2 or μ=3/2). Laser site selective experiments revealed the presence of two nonequivalent environments for the Nd[sup 3+] ions. From room temperature absorption and emission spectra and using the Judd–Ofelt formalism the emission cross sections and quantum efficiency (η=0.1) of the metastable state [sup 4]F[sub 3/2] have been determined. By further modeling we have estimated the crystal length and output coupler transmittance which optimize laser efficiency of a diode pumped NAB laser. The optimum crystal length found in all cases is around 100 μm. Finally, the high laser efficiencies predicted (up to 61% and 45% for laser oscillation at 1.06 and 1.34 μm, respectively) make NAB an excellent candidate to be incorporated in a diode pumped microchip laser device. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which investigated the effects of pump heating on the spectroscopic and laser properties of neodymium-doped yttrium aluminum borate crystal. Experimental details; Temperature variation of optical bands; Results and discussion; Conclusions.

Presents information on a study which investigated the influence of neodymium (Nd) concentration on the spectroscopic and laser properties of Nd doped calcium gallium germanate garnet laser crystal. Methodology; Results and discussion; Conclusion.

In this work, we experimentally demonstrate continuous wave laser generation in the 330–380 nm range by intracavity self-frequency-sum-mixing processes in a Nd[sup 3+]:YAl[sub 3](BO[sub 3])[sub 4] crystal. Ultraviolet laser radiation has been obtained from a simple hemispherical linear cavity by nonlinear interaction between the pump radiation from an argon laser and the infrared laser radiations at 1.06 or 1.33 μm of Nd[sup 3+] ions. In nonoptimal preliminary experiments, up to 0.2 mW of ultraviolet laser power has been obtained at 250 mW of absorbed pump power. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Highlights: [•] We measure a two-dimensional Raman mapping of femtosecond laser written waveguides. [•] We proposed a numerical elastic model to correlate this measurement. [•] We measured the propagated modes in the waveguide. [•] We computed the numerical modes propagated in the model. [•] The model explains the characteristic of the Raman mapping and guided light. [ABSTRACT FROM AUTHOR]

Abstract: In this work we report on the ability of Er/Yb co-doped NaYF4 nano-crystals and CdTe Quantum Dots as two-photon excited fluorescent nano-thermometers. The basic physical phenomena causing the thermal sensitivity of the two-photon excited emission bands have been discussed and the maximum thermal resolution achievable in each case has been estimated. The practical application of both systems for thermal sensing at the micro-scale in biological systems is demonstrated. In particular, they have been used to evaluate the thermal loading induced by tightly focused laser beams in both living cells and fluids. [Copyright &y& Elsevier]

Abstract: Fifty years since the invention of the laser have been witness of the development of many different laser systems and designs. Among them, miniaturized versions of solid sate lasers based on rare-earth-doped dielectric materials have been proposed and demonstrated during the last 20years. They are based on confined radiation provided by optical waveguide structures. Although many materials and techniques have been studied for producing planar and channel waveguides, only a few of them have shown to be adequate routes for fabricating waveguide lasers. Here we summarize the theory and specific technologies developed for characterizing waveguide structures, and we present some common fabrication techniques already successfully applied to fabricate dielectric waveguide lasers, where relevant examples of demonstrated working devices are outlined. [Copyright &y& Elsevier]

Near-field-optical-microscopy has been used to study the micro-modifications caused by femtosecond laser pulses focused at the surface and in the volume of lithium niobate crystals. We have found experimental evidence of the existence, close to femtosecond ablation craters, of periodic modifications in the surface reflectivity. In addition, the potential application of near-field-optical microscopy for the spatial location of permanent modifications caused by femtosecond pulses focused inside lithium niobate crystals has been also demonstrated. [ABSTRACT FROM AUTHOR]

The luminescence properties of Neodymium ions in Zn diffused LiNbO3 channel waveguides have been studied with sub-micrometric spatial resolution. The analysis of the luminescence spectra suggests the existence of a local expansion and disordering associated to the presence of Zn in the LiNbO3 lattice after the diffusion process. By taking this cause–effect relation into account, it has been possible to determine both the in-depth and lateral Zn diffusion lengths, as well to elucidate the spatial location of the channel waveguide. [ABSTRACT FROM AUTHOR]

This work reports on the microstructural modifications produced by nanosecond ultraviolet ablation in neodymium doped lithium niobate crystals. The neodymium ions have been used as optical probes to determine the extension and nature of the modified bulk material. From micro-luminescence experiments we have been able to determine the spatial distribution of the UV ablation induced material densification, local disorder and defect creation. Results have been compared to those previously obtained from femtosecond irradiated lithium niobate crystals. [ABSTRACT FROM AUTHOR]

Abstract: We report on crystal growth and fluorescence characterization of Yb3+ doped NdPO4 single crystals. From the analysis of fluorescence decay curves, the temperature dependence of Nd3+ →Yb3+ and Nd3+ ←Yb3+ energy transfer processes has been obtained. We have found that the dominant process is strongly temperature dependent, this leading to a temperature induced luminescence switching from Yb3+ to Nd3+ ions. [Copyright &y& Elsevier]

Abstract: Czochralsky grown Nd3+-ion doped barium sodium niobate (Ba2NaNb5O12, “banana”) optical super-lattices have been characterized by a combination of chemical etching, optical microscopy, micro-Raman and micro-photoluminescence experiments. The presence of ferroelectric domains, induced during growth process, is accompanied by a periodic modulation of Nd3+-ion concentration as well as by a small lattice distortion. When Nd3+-ion laser action at ≈1.06μm is achieved under 0.808μm laser diode pumping, the singularities of refractive index caused by opposed ferroelectric domains lead to non-collinear intra-cavity propagation. [Copyright &y& Elsevier]

New results on the evolution of the emission of Nd 3 + doped Sr x Ba 1 - x Nb 2 O 5 crystal during the ferroelectric phase transition are presented and compared to those previously obtained for Cr 3 + and Yb 3 + doped Sr x Ba 1 - x Nb 2 O 5 . We have observed that Nd 3 + emission is insensitive to the structural changes suffered by the crystal during the phase transition, contrary to the observations obtained for the cases of the Cr 3 + and Yb 3 + doped crystals. The results are interpreted in terms of the different lattice sites occupied by the optically active ions in the Sr x Ba 1 - x Nb 2 O 5 crystal. [ABSTRACT FROM AUTHOR]

Abstract: Bi-functional laser and non-linear optical crystals (second and Raman third order optical non-linearity) lead to simple, compact and robust devices. Recent results of new self-frequency conversions from UV to infrared range of wavelengths are summarized. We review the relevant properties of the different crystals used, including growth methods. The interest of working out of the principal planes in bi-axial crystals is also pointed out. New crystals whose study is underway is additionally presented. [Copyright &y& Elsevier]

The infrared to visible luminescence of the Nd3+ ion in the NdAl3(BO3)4 (NAB) laser crystal has been investigated in the 730–840 nm excitation spectral range. Green, yellow and red up-converted emission bands centred at about 535, 595 and 675 nm are observed under excitation within the 4I9/2 → 4F5/2 transition. All these emissions have been attributed to the transitions 4G7/2 → 4I9/2 (green), 4G7/2 → 4I11/2 (yellow) and 4G7/2 → 4I13/2 (red). From luminescence measurements and using a simple ratio equation model to fit the experimental data, it can be inferred that the 4G7/2 excited state is populated mainly via energy transfer up-conversion between Nd3+ ions in the 4F3/2 metastable state. [Copyright &y& Elsevier]

Simultaneous generation of coherent radiation at the three fundamental colours from aperiodically poled Nd3+ doped non-linear crystals is reported. In these crystals a rich variety of non-linear processes involving both pump and infrared laser radiations is possible by means of the quasiphase matching (QPM) technique. The case of Nd3+ doped strontium barium niobate crystal (showing a random distribution of ferroelectric domains) is described in detail and its main properties are compared to those reported for other Nd3+ doped non-linear crystals in which broadband QPM is also possible. Finally, a compilation of the latest results on simultaneous multi-frequency visible light generation obtained from Neodymium doped Strontium Barium Niobate is given. [Copyright &y& Elsevier]

We show how non linear crystals activated with Yb 3+ or Nd 3+ ions can be used to develop diode pumped solid state lasers emitting in the visible region of the electromagnetic spectrum. For this purpose we have selected relevant examples of systems investigated in our laboratory. [ABSTRACT FROM AUTHOR]

Abstract. In this paper we show how the quantum efficiency of Nd[sup 3+]-doped laser crystals can be measured by means of a very simple method. This method is based on a multi-wavelength study of pump-induced crystal heating, and its major advantage is the simplicity of the required experimental set-up. It has been used to determine the quantum efficiency of the main infrared laser channel ([sup 4]F[sub 3/2] arrow right [sup 4]I[sub 11/2]) of the Nd[sup 3+]:Gd[sub 2](MoO[sub 4])[sub 3] non-linear laser crystal. The value obtained for the quantum efficiency (phi = 0.97) is in good agreement with that obtained from the Judd-Ofelt formalism (phi = 0.95). [ABSTRACT FROM AUTHOR]

Abstract. Red laser radiation at 693 nm has been obtained from a LiNbO:ZnO:Nd crystal by self-frequency-doubling its fundamental laser line at 1386 nm. Pumping was achieved by means of a Ti:sapphire laser. In preliminary experiments a red laser power of 2.3 mW has been obtained for a total absorbed pump power of 800 mW. External second-harmonic experiments (1386-693 nm) are used to investigate some basic non-linear properties such as phase-matching angle, angular and thermal acceptances of this process. [ABSTRACT FROM AUTHOR]

Abstract. This work reports for the first time continuouswave laser action at room temperature around 1.3 micro m in Nd[sup 3+] doped LiNbO[sub 3]:ZnO. Optical spectroscopy has been used to determine the main laser characteristics of [sup 4]F[sub 3/2] arrow right [sup 4]I[sub 13/2] channel, such as emission cross section and excited-state absorption cross section at laser wavelengths. Internal optical losses have been estimated from laser gain experiments. Under non-optimal conditions laser slope efficiencies of 30% have been obtained. PACS: 42.55.R; 42.65; 42.70 [ABSTRACT FROM AUTHOR]

We report the fabrication of buried optical channel waveguides in strontium barium niobate nonlinear ferroelectric crystals by direct ultrafast laser inscription. These waveguides are strongly polarized and can be reversibly switched on and off by changing the temperature of the crystal, a characteristic we attribute to the bistable enhancement of the electro-optic coefficients at the ferro to paraelectric phase transition. [ABSTRACT FROM AUTHOR]

We report on continuous wave laser oscillation of trivalent ytterbium ions in the frequency converter Yb3+:Sr0.6Ba0.4Nb2O6 ferroelectric laser crystal. Pump induced thermal loading has been used to drive the crystal from its ferroelectric to paraelectric phase. Stable laser radiation at 1070 nm was found in both phases while a bistable laser output is observed through phase transition. In addition, diffuse green (535 nm) radiation was generated by self-frequency doubling of the fundamental laser radiation because of the random distribution of microferroelectric domains existing in the ferroelectric as grown crystal. [ABSTRACT FROM AUTHOR]

The spatial variation of the spectroscopic properties of Nd3+ ions in oxygen implanted Nd:MgO:LiNbO3 channel waveguides have been investigated by scanning confocal microluminescence experiments. Although the radiative probabilities of Nd3+ ions were unaffected by the waveguide fabrication procedure, slight changes (in terms of spectral position and width of the emission lines) have been found in the electronic damage region. Raman spectra have been also analyzed in order to get a further understanding on the possible relation of these spectral changes with the micro-modifications induced during the waveguide formation. [ABSTRACT FROM AUTHOR]

Room temperature highly efficient laser action from an ytterbium-doped phosphate glass is demonstrated when end pumped by a 975 nm fiber-coupled laser diode. Laser slope efficiencies as high as 88% have been obtained, leading to pump-to-laser conversion efficiencies greater than 50%. From the analysis of pumping threshold and laser slope efficiencies the authors have determined both the optical losses and emission cross section at laser wavelength (1028 nm). [ABSTRACT FROM AUTHOR]

Direct intracavity thermal loading measurements have been performed on diode pumped Yb3+ doped LiNbO3:MgO laser crystals. The fractional thermal loading has been found to be strongly dependent on the Yb3+ concentration, decreasing more than 40% when the Yb3+ concentration increases from 0.5 to 2 at. %. From the analysis of the concentration dependence of the fractional thermal loading, the intrinsic fluorescence quantum efficiency (free of radiation trapping) of Yb3+ ions in LiNbO3:MgO crystals has been determined and the role of radiation trapping among Yb3+ ions is discussed. [ABSTRACT FROM AUTHOR]

We report on the polarization and temperature dependence of optical distortions of beams passing through a Nd3+-doped Sr0.61Ba0.39Nb2O6 laser crystal. For temperatures close to TC (≈70 ºC), a strong enhancement in the optical distortion of a nonabsorbed beam takes place, related to the temperature dependence of the r33 electro-optical coefficient during phase transition. From pump and probe experiments, we have concluded that the traditional 808 nm Nd3+ pumping radiation also causes optical distortions, especially for extraordinary polarized radiation. [ABSTRACT FROM AUTHOR]

A spectral switcher based on the Yb3+-doped Nd3BWO9 crystal has been demonstrated. This system switches its main luminescence peak from 980 nm (the characteristic luminescence of Yb3+ ions) to 1060 nm (the characteristic luminescence of Nd3+ ions) as the 808 nm pump intensity is increased from 0.4 up to 0.8 kW/cm2. The operation mechanism is based on the interplay between the Nd3+↔Yb3+ energy transfer processes and on the strong pump-induced thermal loading. The operation principles described in this letter allow for the tailoring of promising luminescent switchers operating at any desired spectral range by choosing the suitable sensitized host emitting crystal. [ABSTRACT FROM AUTHOR]

This work reports on room-temperature continuous-wave laser action at 929 nm from a Nd3+:LiNbO3 nonlinear laser crystal co-doped with ZnO. The spectroscopic parameters of the quasi-three-level 4F3/2→4I9/2 laser channel are discussed. In nonoptimal preliminary experiments, pump power at threshold was found to be as low as 105 mW. [ABSTRACT FROM AUTHOR]

The temperature dependence of the emission spectrum of Cr3+ ions in Sr0.6Ba0.4 (NbO3)2 has been systematically investigated around the ferroelectric phase transition of this crystal (≈370 K). In spite of the strong thermal quenching of the luminescence occurring at these temperatures, the emission spectrum is still clearly detectable and shows dramatic changes in both line shape and intensity when passing through the phase transition temperature. A redshift of about 6 nm occurs when the crystal is driven from the polar to the nonpolar phase. In addition, this shift displays a thermal hysteresis, then providing the possibility of realizing a bistable spectral system based on this material. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

An optimization of the laser action performance from a diode-pumped Yb[sup 3+]-doped LiNbO[sub 3]:MgO crystal has been carried out. In this sense, efficient laser action at 1.06 μm when pumping with a fiber-coupled laser diode at 980 nm has been demonstrated, achieving laser slope efficiencies as high as 74%. The influence of output mirror transmittance on both pumping threshold and laser slope efficiency has been investigated, and the parameters of relevance in laser dynamics (emission cross section and optical losses) have been determined. Under the experimental conditions leading to maximum slope efficiency, the pump power at threshold was 300 mW, and the pump-to-laser conversion efficiency was 40%. [ABSTRACT FROM AUTHOR]

We present an investigation in NdAl[sub 3](BO[sub 3])[sub 4] (NAB) crystal of the excited-state absorption (ESA) around the main laser lines (1060 and 1338 nm) by the so called excited-state excitation technique. The involved transitions are from the [sup 4]F[sub 3/2] level toward the [sup 4]G[sub 7/2]+[sup 4]G[sub 9/2]+[sup 2]K[sub 13/2] levels (1300–1400 nm range) or toward the [sup 2]G[sub 9/2]+[sup 4]G[sub 11/2]+[sup 2]D[sub 3/2]+[sup 2]K[sub 15/2] levels (1020–1100 nm range). We have performed the Judd–Ofelt analysis extended to anisotropic crystals in order to get the cross sections (cm[sup 2]). In each case, the ESA peaks do not coincide with the laser emission ones, but a reduction of the effective laser emission cross section is observed at 1338 nm. Finally, the values obtained from the application of the Judd–Ofelt formalism have been used to estimate the influence of ESA in the pumping domain on the laser performance. It has been found that its contribution is not significant, indicating that NAB is an excellent candidate for efficient high-power microchip lasers emitting at 1060 and 1338 nm. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

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:YVO[SUB4] 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. [ABSTRACT FROM AUTHOR]

Arrays of submicrometric Ni lines have been fabricated in superconducting Nb films by electron beam lithography. In the mixed state, these arrays induce strong anisotropy in the dissipation behavior. The dissipation is reduced several orders of magnitude, in the whole applied magnetic field range, when the vortex motion is perpendicular to the Ni lines (applied current parallel to them) in comparison with dissipation of vortices moving parallel to the lines. In addition, for the samples studied in this work, a change in the slope ofthe ρ(B) curves is observed when the vortices move perpendicular to the lines and the vortex lattice parameter matches the width of the Ni lines. [ABSTRACT FROM AUTHOR]

In this letter we demonstrate continuous-wave blue and green diffuse laser light generation from a Nd[sup 3+]-doped Sr[sub 0.6]Ba[sub 0.4](NbO[sub 3])[sub 2] crystal located in an end-pumped laser cavity and operating at the [sup 4]F[sub 3/2]→[sup 4]I[sub 11/2] 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. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Demonstrates the efficiency of continuous wave laser radiation at 1314 and 1386 nanometer in a LaBGeO[sub 5]:Nd[sup 3+] nonlinear crystal with stable operation at room temperature. Absorbed power threshold; Slope efficiency percentage for an 3% output coupling; Strategy to obtain visible red laser radiation.

Demonstrates the possibility of obtaining continuous wave blue and red laser radiation in yttrium aluminum borate crystal lasers. End pumping through self-sum frequency mixing to obtain blue and green color; Obtainment of red color by self-frequency doubling of the fundamental laser line; Pump radiation wavelength for green and blue colors.

Reports on continuous-wave red laser radiation from a self-frequency-doubled laser of YAl[sub 3](BO[sub 3])[sub 4]:Nd[sup 3+] operating at a fundamental wavelength in the [sup 4]F[sub 3/2]...[sup 4]I[sub 13/2] laser channel of Nd[sup 3+] ion. Investigation of the main laser characteristics at the fundamental wavelength and second harmonic generation properties.

Temperature control of the devitrification process in an erbium doped oxyfluoride glass under laser irradiation is reported. The green upconversion emissions around 525 and 545 nm originated from the thermalized 2H11/2 and 4S3/2 levels were studied when the glass structure changes to glass ceramic during irradiation with a laser beam. Power dependence of the fluorescence intensity ratio was used to determine the temperature of the irradiated zone. The transition from glass to glass ceramic takes place under 2300 mW of laser power with an estimated temperature around 783 K. This result agrees with the one obtained in the samples devitrified under conventional furnace treatment. Therefore, the estimation of the temperature of the irradiated zone through the fluorescence intensity ratio method allows a controlled devitrification. Moreover, an irradiated line has been written in the glass showing an important diffusion of the Pb2+ and F- ions. These results confirm that nanocrystals have been created due to the laser action. [ABSTRACT FROM AUTHOR]

In this work the anisotropic thermal lens (TL) effect was studied in Nd3+ doped SrxBa1-xNb2O6 crystals with two different stoichiometries (x=0.47 and 0.61). TL measurements were carried out as a function of temperature from 30 up to 140 °C so that the effect of phase transition was investigated. A strong enhancement in the TL effect during the ferro-to-paraelectric phase transition has been observed. Additionally, we have found an inversion of the TL signal with the crystal stoichiometry. This fact is explained in terms of a different thermal expansion along the c axis for both crystals, as measured by x-ray diffraction experiments. The obtained results open the possibility to tailor a crystal stoichiometry that minimizes the TL effects. [ABSTRACT FROM AUTHOR]