Cross Sections Of Nd Research Articles

Computation and Verification of Spatial Rate Equations for an Electro-Optically Q-Switched Laser-Diode Side-Pumped Nd:YAG Laser

In a side-pumped laser module, we simulate the pumping power distribution across the cross-section of Nd:YAG rods at varying diameters. The coupled rate equations with the spatial overlap efficiency for a four-level actively Q-switched side-pumped laser are considered complete. After a Q-switched pulse terminates, the expressions of laser output parameters are derived. We assess the single pulse energy, pulse width, and peak power using the analysis function. The 200 Hz Q-switched side-pumped Nd:YAG laser with a peak power of 103 kW and beam quality factors M2 = 1.67 is developed to the validity of theoretical models.

Optical properties of Nd,Th:LaAlO3 demonstrates its potential in high-energy pulsed laser

Report, to the best of our knowledge, the first laser operation of perovskite oxide LaAlO3 doped with 1 at.% Nd ions and 0.2 at.%Th (Nd,Th:LaAlO3). Optical properties of Nd,Th:LaAlO3 were demonstrated. We study the influence of Th dopants on the domain structure and spectroscopic properties of LaAlO3. Under 793 nm diode-pumped excitation, we achieve a continuous-wave laser output at 1080 nm with a slope efficiency of 36 % and an optical-to-optical efficiency of 34 % under a Toc = 5 % output coupler. The emission cross section of Nd,Th:LaAlO3 reaches 3.65 × 10−20 cm2 at 1080 nm, the saturation flux is 5 J/cm2. The fluorescence lifetime reaches 317 μs and the thermal conductivity is 10.3 W/m·K at 25 °C. Considering its excellent mechanical properties and thermal conductivity, Nd,Th:LaAlO3 is a promising high-energy pulsed laser material.

Structural disordered orthophosphate crystal Nd3+:YBa3(PO4)3 with cubic symmetry

A novel laser crystal Nd3+-doped yttrium barium phosphate (Nd:YBa3(PO4)3, hereafter Nd:YBP) with disordered crystal structure was reported. Single crystal growth, thermal, spectral and laser performances were investigated. The thermal conductivity at room temperature was found to be 1.35 W·m−1·K−1 and shown an increased tendency with increased temperature. The spontaneous transition probabilities, radiation lifetime and other parameters were evaluated by using the Judd-Ofelt (J-O) theory. The maximum absorption and emission cross sections for Nd:YBP crystal were obtained to be ∼ 2.32 × 10−20 cm2 (@ 804 nm) and 6.72 × 10−20 cm2 (@ 1056 nm), respectively. The measured fluorescence lifetime for Nd:YBP crystal was equal to 351 μs. Furthermore, diode-pumped continuous-wave laser operation was firstly realized near 1060 nm. The slope efficiency was found to be approximately 22% and the maximum output power for Nd:YBP crystal was 256 mW. Results reveal that the disordered crystal Nd:YBP might be further optimized for uses in laser field.

Structure and properties of new fluoro-sulfo-phosphate laser glasses

<p indent=0mm>Rare-earth-doped fluoro-sulfo-phosphate (FSP) glass is characterized by excellent spectroscopic properties and high thermal and chemical stabilities. Therefore, it is a potential candidate for laser glass and high-gain active optical fiber matrix. However, the underlying contributions of compositional variations to the structure and properties of FSP glass systems are still indistinct owing to their complex mixed-anion nature. Herein, the glass-forming region, structure, physical, and luminescent properties of several FSP glasses are characterized. The results show that FSP glasses possess the advantages of fluoro-phosphate glasses such as high rare-earth ion solubility, low refractive index and phonon density of states. Meanwhile, the mixed-anion structure improves the thermal and chemical stabilities, elastic modulus and spectroscopic parameters. The fabricated FSP samples have good glass-forming ability, low nonlinear refractive index (minimum: <sc>1.2×10⁻¹³ esu</sc>), good thermal stability (∆<italic>T</italic>_max=181°C), chemical stability (DR_min=<sc>0.7×10⁻⁷ g cm⁻² min⁻¹</sc>) and relatively high elastic modulus (<italic>E</italic>_max<sc>=68.8 GPa).</sc> The maximum emission cross-section of Nd³⁺:⁴F_3/2 →⁴I_11/2 is <sc>3.3×10⁻²⁰ cm²,</sc> effective linewidth is <sc>32.1 nm,</sc> lifetime is <sc>372 μs</sc>, and FOM and gain bandwidth are <sc>1.2×10⁻²³ s cm²</sc> and<sc>105.9×10⁻²⁷ cm³,</sc> respectively. These results are higher than those of phosphate or fluoro-phosphate laser glasses, indicating the broad application prospects of FSP glasses in laser glass, fiber lasers and amplifiers.

Effects of Sr2+ content on microstructure and spectroscopic properties of Nd3+ doped Ca1-xSrxF2 transparent ceramics

CaF2-SrF2 hosts with substitution disorder of Ca2+/Sr2+ sites in the lattice provide lower local symmetry for RE3+ ions compared with pure CaF2 or SrF2 hosts, thereby facilitating more efficient 4f → 4f transitions. Here we report a study of effects of Sr2+ content on microstructure and spectroscopic properties of Nd3+ doped Ca1-xSrxF2 transparent ceramic. Phase and microstructure analyses show that when x is in the range of 0–0.25, Nd: Ca1-xSrxF2 nanoparticles keep pure CaF2 phase with their size, morphology and agglomeration degree mildly changed. Increasing x from 0 to 0.2 significantly improves the luminescence intensity, emission lifetime and emission cross-section of Nd: Ca1-xSrxF2, however, hardly affects the concentration quenching. The luminescence intensities and emission lifetimes of x = 0.2 and 0.25 samples are very close, probably indicating SrF2 phase has already formed in x = 0.25 sample. Based on the spectroscopic properties, the optimal Sr2+ content is found to be x = 0.2.

60-W 946-nm cryogenically-cooled Nd:YAG laser

Detailed spectroscopic characterisation of the ^4I_{9/2} rightarrow ^4F_{3/2} absorption cross section of Nd:YAG at temperatures ranging from room temperature to liquid nitrogen temperature is reported. Exploiting this in-band pumping scheme, a novel volume-Bragg-grating-locked diode-laser array (DLA) operating at 869 nm was developed to end-pump a cryogenically cooled Nd:YAG crystal. As a result, the first 60-W cryogenically-cooled Nd:YAG laser operating at 946 nm is demonstrated with a slope, and optical-to-optical, efficiency of 52%.

Influence of an equimolar amount of aluminium and phosphorus on spectroscopic properties of neodymium under local phosphorus environment in silica glass

To exhibit large emission cross sections of Nd in silica glass, Nd surroundings were regulated in Al/P co-doped silica glass prepared by our multi-step method. The influence of an equimolar amount of Al and P on spectroscopic properties was studied under the local phosphorus coordination environment of Nd. The uniformity of composition distribution was characterized by energy dispersion spectra (EDS) and the coordination environment of Nd ions was characterized by the electron paramagnetic resonance (EPR) spectra. The results indicate that the composition distribution is of high uniformity and Nd has a stronger interaction with P atoms than Al atoms regardless of Al/P molar ratio. Local phosphorus coordination environment of Nd ions in silica glass is achieved. Large σem can be achieved when Al or P is excessive, and larger σem is more likely achieved when P is much more than Al. This work brings new possibilities for obtaining large stimulated cross sections of Nd in silica glass.

Designing Upconversion Nanocrystals Capable of 745 nm Sensitization and 803 nm Emission for Deep-Tissue Imaging.

A crystal design strategy is described that generates hexagonal-phased NaYF4 :Nd/Yb@NaYF4 :Yb/Tm luminescent nanocrystals with the ability to emit light at 803 nm when illuminated at 745 nm. This is accomplished by taking advantage of the large absorption cross-section of Nd(3+) between 720 and 760 nm plus efficient spatial energy transfer and migration through Nd(3+) →Yb(3+) →Yb(3+) →Tm(3+) . Mechanistic investigations suggest that a cascaded two-photon energy transfer upconversion process underlies the emission mechanism. This protocol enables deep-tissue imaging to be achieved while mitigating the attenuation effect associated with the visible emission and the overheating constraint imposed by conventional 980 nm excitation.

Measurements of the Cross Sections and A y for D(p, n) Inclusive Breakup Reaction at 170 MeV

The effects of three-nucleon force (3NF) has been actively studied by using the nucleon–deuteron (Nd) scattering states. The differential cross sections of the elastic Nd scattering at the energy below 150 MeV can be well reproduced by incorporating 3NF in the Faddeev calculation based on modern nucleon–nucleon (NN) interactions. On the other hand, the differential cross sections of Nd elastic and inelastic scatterings at 250 MeV show large discrepancies between the data and the Faddeev calculations with 3NF. It indicates the presence of the missing features of the three nucleon system at this energy region. For the systematic study about the energy dependence of this large discrepancies, we measured the differential cross sections and the vector analyzing power Ay for the 2H(p, n) inclusive breakup reaction at 170 MeV. The experiment was carried out at RCNP by detecting scattered neutrons by using the neutron detector NPOL3. The data was compared with the results of the Faddeev calculations with and without the 3NF.

Diode-pumped actively Q-switched Nd:GGG laser operating at 938 nm

The stimulated emission cross-section of Nd:GGG crystal in 938 nm transition was measured by the amplifier approach. It is 2.3×10 −20 cm 2. A quasi-continuous-wave diode pumped, actively Q-switched Nd:GGG laser operating at 938 nm was demonstrated. Pumped by laser diodes with 900 W peak power and 300 μs pulse duration, it generated 168 mJ energy in long pulse mode. The slope efficiency was 36%. Q-switched by a KD⁎P Pockels cell, 41 mJ output pulse energy was obtained. The pulse duration and peak power were 120 ns and 340 kW, respectively. The optical to optical efficiency was 7%.

Variation of the stimulated emission cross section in Nd:YAG caused by the structural changes of Russell-Saunders manifolds

It was experimentally found that electronic structures of Russell-Saunders manifolds in Nd:YAG depended on the Nd3+-doping concentration (CNd) and its fabrication process. Both of the bandwidth and the branching ratio in fluorescent transitions in Nd:YAG varied almost linearly depending on CNd, and a fabrication process has its own diluted limit of the bandwidth and the branching ratio. Also dependences of Stark splitting in Nd:YAG were also observed. Nd3+-doping causes 1.9% and 4.5% reduction in the stimulated emission cross section of Nd:YAG per 1at.% of CNd at 1.064 μm and 1.319 μm, respectively.

Photo-thermo-refractive glass co-doped with Nd 3+ as a new laser medium

Photo-thermo-refractive (PTR) glass demonstrates refractive index change after exposure to UV radiation followed by a thermal treatment that enables recording of high efficiency holographic optical elements. This work demonstrates feasibility of function of this material as a complex optical medium which posseses both photosensitive and luminescent properties and paves a way for creation of monolythic solid state lasers where resonator components can be holographically recorded inside of a laser medium. It was found, that incorporating of Nd 3+ ions in PTR glass does not affect photosensitivity required for hologram recording. It was demonstrated that emission wavelength, spectral width, and cross section of Nd 3+ luminescence in PTR glass are typical for silicate laser glasses and Nd-doped PTR glass can be considered as a promising laser medium for monolithic solid state lasers.

Temperature dependence of the emission cross section of Nd:YVO_4 around 1064 nm and consequences on laser operation

We propose an accurate measurement of the evolution of the emission cross section of Nd:YVO4 versus temperature around 1064&#x2009;nm. This was done by using two complementary methods involving spectrum acquisition and laser oscillator small signal gain measurement. We observed a 44% decrease of the peak emission cross section for a 64&#x2009;&#xB0;C temperature increase but also a shift of the peak emission cross section wavelength at a rate of 3&#x2009;pm/&#xB0;C. The influence of the crystal temperature on the performance of a laser oscillator in continuous wave was also investigated.

Dipole responses in Nd and Sm isotopes with shape transitions

Photoabsorption cross sections of Nd and Sm isotopes from spherical to deformed even nuclei are systematically investigated by means of the quasiparticle-random-phase approximation based on the Hartree-Fock-Bogoliubov ground states (HFB+QRPA) using the Skyrme energy density functional. The gradual onset of deformation in the ground states as increasing the neutron number leads to characteristic features of the shape phase transition. The calculation well reproduce the isotopic dependence of broadening and emergence of a double-peak structure in the cross sections without any adjustable parameter. We also find that the deformation plays a significant role for low-energy dipole strengths. The $E1$ strengths are fragmented and considerably lowered in energy. The summed $E1$ strength up to 10 MeV is enhanced by a factor of five or more.

Growth and spectroscopic properties of Nd 3+-doped Na 2Gd 4(MoO 4) 7 crystal

This paper reports the growth and spectral properties of Nd 3+:Na 2Gd 4(MoO 4) 7 crystals. An Nd 3+:Na 2Gd 4(MoO 4) 7 crystal with dimensions of Ø20 × 25 mm 3 has been grown by the Czochralski method. The spectroscopic properties of Nd 3+:Na 2Gd 4(MoO 4) 7 crystal were investigated. The Judd–Ofelt theory was applied to calculate the spectral parameters. The polarized absorption cross-sections of Nd 3+:Na 2Gd 4(MoO 4) 7 crystal are 4.25 × 10 −20 cm 2 with full width at half maximum (FWHM) of 14.6 nm for the π-polarization and 2.87 × 10 −20 cm 2 with FWHM of 16.2 nm for the σ-polarization, respectively. The emission cross-sections are 10.0 × 10 −20 cm 2 at 1060 nm for π-polarization and 13.6 × 10 −20 cm 2 at 1067 nm for σ-polarization, respectively. The fluorescence quantum efficiency has been estimated to be 90.0%. Nd 3+:Na 2Gd 4(MoO 4) 7 crystal may be considered as a potential laser gain medium for the diode laser pumping.

Segregation during crystal growth from melt and absorption cross section determination by optical absorption method

Segregation during crystal growth from melt under two conditions is studied by using crystal mass, which can be measured easily, as an independent variable, and a method to determine the effective segregation coefficient and absorption cross section of optical dopant is given. When the segregated solute disperses into the whole or just a part of melt homogenously, the concentration Cs in solid interface will change by different formulas. If the crystal growth interface is conical and segregated solute disperses into melt in total or part, the solute concentration at r = 2/3R, where r is the distance from the growth cross section center and R the crystal radius, is independent on the shape of the crystal growth interface, and its variation at r = 2/3R can be regarded as the result from crystal growth in flat interface. With Cs variation formula in solid and absorption cross section σ for optical dopant, the absorption coefficients along the crystal growth direction can be calculated, and the corresponding experimental value can be obtained through the crystal optical absorption spectra. By minimizing the half sum, whose independent variables are k, ΔW or σ, of the difference square between the calculated and experimental absorption coefficients from one or more absorption peaks along the crystal growth direction, k and σ, or k and ΔW, can be determined at the same time through the Levenberg-Marquardt iteration method. Finally, the effective segregation coefficient k, ΔW and absorption cross sections of Nd:GGG were determined, the results fitted by two formula gave more closed effective segregation coefficient, and the value ΔW also indicates that the segregated dopant had nearly dispersed into the whole melt. Experimental results show that the method to determine effective segregation coefficient k, ΔW and absorption cross sections σ is convenient and reliable, and the two segregation formulas can describe the segregation during the crystal growth from melt relatively commendably.

Spectroscopic properties of Nd 3+ doped transparent oxyfluoride glass ceramics

In this paper, the spectroscopic properties of Nd 3+ doped transparent oxyfluoride glass ceramics containing LaF 3 nano-crystals were systematically studied. The formation and distribution of LaF 3 nano-crystals in the glass matrix were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Based on Judd–Ofelt theory, the intensity parameters Ω t ( t = 2, 4, 6), spontaneous emission probability, radiative lifetime, radiative quantum efficiency, width of the emission line and stimulated emission cross-section of Nd 3+ were evaluated. Particularly, the effect of Nd 3+ doping level on them was discussed. With the increase of Nd 3+ concentration in the glass ceramic, the experimental luminescence lifetime, radiative quantum efficiency and stimulated emission cross-section vary from 353.4 μs, 78.3% and 1.86 × 10 −20 cm 2 to 214.7 μs, 39.9% and 1.52 × 10 −20 cm 2, respectively. The comparative study of Nd 3+ spectroscopic parameters in different hosts suggests that the investigated glass ceramic system is potentially applicable as laser materials for 1.06 μm emission.

Growth, thermal and spectral properties of Nd 3+-doped NaGd(MoO 4) 2 crystal

Nd 3+-doped NaGd(MoO 4) 2 crystal with dimensions Φ 21 × 42 mm 2 were grown by Czochralski method. Nd 3+:NaGd(MoO 4) 2 crystal melts at 1182 °C. The hardness of Nd 3+:NaGd(MoO 4) 2 crystal is 334 VDH. The specific heat is 72.6 cal/mol K. The thermal expansion coefficients are 2.38 × 1 0 - 5 K - 1 for c-axis and 1.49 × 1 0 - 5 K - 1 for a-axis, respectively. The absorption cross-sections of Nd 3+:NaGd(MoO 4) 2 crystal are 15.91 × 1 0 - 20 cm 2 with a FWHM of 9 nm at the 804 nm for π-polarization and 3.66 × 1 0 - 20 cm 2 with a FWHM of 17 nm at 807 nm for σ-polarization, respectively. The emission cross-section σ em are 1.73 × 1 0 - 20 cm 2 at 1063 nm for π-polarization and 1.94 × 1 0 - 20 at 1070 nm cm 2 for σ-polarization, respectively. The fluorescence lifetime τ f is 93.9 μs at room temperature.

Comparative study on the spectroscopic properties of Nd:GdVO/sub 4/ and Nd:YVO/sub 4/ with hybrid process

We have proposed a hybrid procedure for determining spectroscopic parameters for uniaxial solid-state laser crystals. Using our procedure, the spectroscopic properties of Nd:GdVO/sub 4/ were evaluated and compared to those of Nd:YVO/sub 4/. As a result, the peaks of absorption and stimulated emission cross sections of Nd:GdVO/sub 4/ in /spl pi/-polarization were determined to be 2.6 and 10.3/spl times/10/sup -19/ cm/sup 2/, respectively, and were smaller than those of Nd:YVO/sub 4/. On the other hand, the fluorescence lifetime of 1 at% Nd:GdVO/sub 4/ was evaluated to be 83.4 /spl mu/s, and was similar to 84.1 /spl mu/s of 1 at% Nd:YVO/sub 4/. Therefore, the product of stimulated emission cross section and fluorescence lifetime (/spl sigma//sub em//spl tau//sub f/ product) of Nd:GdVO/sub 4/ was smaller than that of Nd:YVO/sub 4/ under 1 at% of Nd/sup 3+/ doping concentration. The radiative lifetime of spontaneous emission of Nd:GdVO/sub 4/ was 168 /spl mu/s and was 1.9 times longer than that of Nd:YVO/sub 4/. Because of the low value of radiative quantum efficiency of Nd:GdVO/sub 4/ (50%), careful cavity design is required for creating a well performing solid-state laser with Nd:GdVO/sub 4/, based on the larger /spl sigma//sub em//spl tau//sub f/ product rather than the /spl sigma//sub em//spl tau//sub f/ product of Nd:YAG.

High-power Nd:GdVO 4 laser at 1.34 μm end-pumped by laser-diode-array

A diode-end-pumped high-power Nd:GdVO 4 laser operating at 1.34 μm has been demonstrated. The maximum continuous-wave output power of 4.62 W was obtained at the incident pump power of 14.75 W, with the corresponding optical conversion efficiency of 31.3% and the average slope efficiency of 33.1%. By using the experimentally measured threshold pump power and slope efficiency, the stimulated emission cross-section of Nd:GdVO 4 crystal at 1.34 μm was determined to be 1.78×10 −19 cm 2 .