Spectral study of the stimulated emission of Nd3+ in fluorotellurite bulk glass

Growth, Optical, and Spectroscopic Properties of Pure and Nd3+-Doped GdSr3(PO4)3 Crystals with Disordered Structure

Disordered crystals have attracted immense attention for the generation of ultrashort laser pulses due to their good thermomechanical characteristics and wide emission bandwidths. In this work, a Gd-based orthophosphate crystal, GdSr₃(PO₄)₃, (GSP), and a Nd³⁺-doped GdSr₃(PO₄)₃ crystal, (Nd:GSP), were obtained by the Czochralski method. The crystal structure, optical properties, electronic band structure, laser damage threshold, and hardness of the GSP crystal were comprehensively investigated. It exhibited a disordered structure due to the random distribution of Sr and Gd atoms in the same Wyckoff site, which caused inhomogeneous spectral broadening. Additionally, it exhibited a short UV absorption cutoff edge (<200 nm), a large band gap (5.81 eV), and a high laser damage threshold (∼1850 MW/cm²). The spectral properties and Judd-Ofelt calculations of the Nd:GSP crystals were analyzed. A wide absorption band at 803 nm, with a full width at half-maximum value of 20 nm, makes the Nd:GSP crystal suitable for the efficient pumping of AlGaAs laser diodes. Sub-100-fs pulses could be supported by its 25 nm emission bandwidth. Hence, the GSP crystal could be a promising disordered crystal laser matrix.

Nd doped CaYAl3O7: exploration and laser performance of a novel disordered laser crystal

A novel disordered structure crystal has drawn intense interest as a promising ultrafast laser crystal host for its broad absorption and emission bands.

Nd3+-doped transparent tellurite ceramics bulk lasers

We report on the laser emission of the polycrystalline ceramic obtained from the full and congruent crystallization of the parent glass 1Nd³⁺:75TeO₂-12.5Bi₂O₃-12.5Nb₂O₅ composition. In particular, the current work underlines the importance of carefully controlling the heat treatment in order to solely crystallize the Bi_0.8Nb_0.8Te_2.4O₈ cubic phase and consequently avoid the formation of the BiNbTe₂O₈ orthorhombic phase that would be detrimental for optical purpose. The structure, microstructure and photoluminescence properties of the resulting transparent tellurite ceramics are characterized. The continuous-wave and gain-switching laser performances reveal that the emission remains perfectly single transversal mode in the range of pump powers explored. The maximum output power achieved was ~28.5 mW, for a pump power threshold of ~67 mW, and with associated efficiency and slope efficiency of ~22.5% and ~50%, respectively. These data definitely stand among the best results obtained so far for bulk laser tellurite materials and thus demonstrate the potential of such polycrystalline transparent ceramics as optically active materials. Finally, the laser emission characteristics in pulsed regime, at low and high repetition rates, are also provided: more than 6.5 W of peak power at a repetition rate of 728 kHz can be obtained.

Spectroscopy and enhanced frequency upconversion in Nd3+-Yb3+ codoped TPO glasses: energy transfer and NIR to visible upconverter

TeO₂-Pb₃O₄ (TPO) glasses codoped with Nd³⁺ and Yb³⁺ ions have been fabricated by conventional melting technique. The absorption, emission and excitation spectra of the samples have been recorded. The optical band gap in both the doped/codoped glasses is found to be ∼3.31 eV. Judd-Ofelt analysis has been carried out by using the absorption spectrum of 0.8 mol% Nd³⁺ doped glass to determine the radiative properties viz radiative transition probabilities, branching ratios, radiative lifetimes, quality factor and emission cross sections of some emitting levels for Nd³⁺ ions. The radiative transition probability for the ⁴G_7/2 → ⁴I_9/2 transition (∼1926 Hz) is found to be maximum compared to other ⁴G_5/2 → ⁴I_9/2 (∼1622 Hz) and ⁴F_5/2 → ⁴I_9/2 (∼865 Hz) transitions. Upconversion (UC) luminescence of the samples has been examined by the 980 nm CW diode laser excitation. Effect of addition of Yb³⁺ ions in the Nd³⁺ doped glasses on UC emission intensity has been discussed. The UC emission intensity corresponding to the green, red and NIR bands in the codoped glass has been enhanced by ∼17, ∼12 and ∼42 times as compared to that of the Nd³⁺ singly doped glass. The quantum efficiency for the ⁴G_7/2 level is found to be ∼32%. The nephelauxetic ratio, bonding parameter and covalency of Nd³⁺ ions have been found positive which represents the covalent bonding between Nd³⁺ ion and oxygen atom. The colour tunability from yellowish-green to dominant green region has been obtained in the optimized codoped TPO glass.

Boosting the sensitivity of Nd(3+)-based luminescent nanothermometers

Luminescence thermal sensing and deep-tissue imaging using nanomaterials operating within the first biological window (ca. 700-980 nm) are of great interest, prompted by the ever-growing demands in the fields of nanotechnology and nanomedicine. Here, we show that (Gd1-xNdx)2O3 (x = 0.009, 0.024 and 0.049) nanorods exhibit one of the highest thermal sensitivity and temperature uncertainty reported so far (1.75 ± 0.04% K(-1) and 0.14 ± 0.05 K, respectively) for a nanothermometer operating in the first transparent near infrared window at temperatures in the physiological range. This sensitivity value is achieved using a common R928 photomultiplier tube that allows defining the thermometric parameter as the integrated intensity ratio between the (4)F5/2 → (4)I9/2 and (4)F3/2 → (4)I9/2 transitions (with an energy difference between the barycentres of the two transitions >1000 cm(-1)). Moreover, the measured sensitivity is one order of magnitude higher than the values reported so far for Nd(3+)-based nanothermometers enlarging, therefore, the potential of using Nd(3+) ions in luminescence thermal sensing and deep-tissue imaging.

Thermal and spectroscopic characteristics of disordered melilite Nd:BaLaGa3O7 crystal

1 at% Nd:BaLaGa₃O₇ disordered crystal has a large emission bandwidth of 32 nm at 1060 nm.

Optical properties of Nd3+ doped bismuth zinc borate glasses

Glasses with compositions of (100-x) (Bi2ZnOB2O6) -x Nd2O3 (where x=0.1, 0.3, 0.5, 1 and 2 mol%) were prepared by melt quenching method and characterized through optical absorption, emission and decay curve measurements. Optical absorption spectra have been analyzed using Judd-Ofelt theory. The emission spectra exhibit three peaks at 919, 1063 and 1337 nm corresponding to (4)F3/2 to (4)I9/2, (4)I11/2 and (4)I13/2 transitions in the near infrared region. The emission intensity of the (4)F3/2 to (4)I11/2 transition increases with increase of Nd(3+) concentration up to 1 mol% and then concentration quenching is observed for 2 mol% of Nd(3+) concentration. The lifetimes for the (4)F3/2 level are found to decrease with increase in Nd2O3 concentration in the glasses. The decay curves of the glass up to 0.3 mol% of Nd(3+) exhibit single exponential nature and thereafter the curves become nonexponential nature (0.5, 1 and 2 mol%). The nonexponential curve has been fitted to the Inokuti-Hirayama model to understand the nature of energy transfer process.