With the goal of developing new mid-IR lasers, Rare Earth doped low-phonon sulfide-based chalcogenide glasses are being explored for their potential as sources emitting at ~3-microns. Such low phonon energy materials are necessary to minimize competing non-radiative decay processes such as multi-phonon relaxation (MPR). This work presents the results of a comprehensive spectroscopic study comparing the 3-micron laser potential of three different RE ions (Dy3+, Ho3+, and Er3+) doped into sulfide-based chalcogenide glass. Spectroscopic results will focus on absorption, fluorescence, and decay characteristics. From these measurements, laser relevant parameters such as cross sections and radiative lifetimes are calculated.
We are exploring the potential of Praseodymium (Pr³+) as a dopant in low-phonon chloride hosts, CsCdCl3 and CsPbCl3. Pr3+ possesses favorable absorption bands (3H4 → 3F3,4) in the ~1.5 µm range, amendable to efficient laser diode or fiber laser pumping, as well as group of energy levels with energy gaps enabling mid-IR emissions in the 3-5 micron wavelength range of practical interest. In this work, spectroscopic investigation of Pr3+ aimed to also determine whether the “three-for-one” processes boosting the efficiency of mid-IR emission can be observed in these new materials. Detailed spectroscopic results including Judd-Ofelt analysis, transitions cross-sections, and fluorescence dynamics will be discussed and their potential for efficient mid-IR laser operation will be evaluated.
In this work, we present the results of our recent spectroscopic investigation on Dy3+-doped Ga2Ge5S13 (Dy:GGS) glass, aiming to explore its potential for mid-infrared (3-5 µm) laser applications. Under 910 nm excitation, the studied Dy:GGS glass displayed broad emission bands centered at ~2.9 µm and ~4.35 µm corresponding to 6H13/2 --> 6H15/2 and 6H11/2 --> 6H13/2, respectively. The measured fluorescence decay time of the 6H11/2 manifold (upper laser level for 4.35 µm laser transition) was found to be in the millisecond range, demonstrating similarity to other sulfide glasses doped with Dy3+. Spectroscopic results and data modeling including the temperature dependent emission and decay dynamics, concentration dependent studies, Judd-Ofelt analysis, and transition cross-sections, will be presented.
With the goal of developing new mid-IR laser sources, Rare-earth doped low-phonon crystals and sulfide-based chalcogenide glasses are being explored. Low maximum phonon energy materials are necessary to minimize competing non-radiative decay processes such as multi-phonon relaxation (MPR). This work presents the results of a comprehensive mid-IR spectroscopic study on Dy3+ doped sulfide-based chalcogenide glasses, as well as comparative results from similarly doped chloride and fluoride crystals. Spectroscopic results will focus on absorption, fluorescence, and decay characteristics. From these measurements, laser relevant parameters such as cross sections and radiative lifetimes are calculated.
All material types are being considered, from crystals to ceramics and glasses, with focus on those RE3+ hosts with low maximum energy. In this work, a comparative study was performed on the mid-IR (3-5 um) spectroscopic properties of erbium doped in low-phonon fluoride (BaF2) and chloride (CsCdCl3) crystals as well as sulphide (Ga2Ge5S13) glasses. Among the studied materials, Er3+:CsCdCl3 showed the longest 4I9/2 emission lifetime of ~11 ms whereas the ~ 46 us observed from Er3+:BaF2 was the shortest 4I9/2 lifetime. These results reflect the reduced nonradiative rates through multiphonon relaxation in chloride crystals. Spectroscopic results and data modeling including the temperature dependent emission and decay dynamics, Judd-Ofelt analysis, and transition cross-sections will be presented.
The development of mid-IR lasers faces some unique challenges when striving to achieve the highest efficiency and power output. Most critical among these challenges is luminescence quenching of the relatively closely-spaced upper and lower laser levels, usually occurring through the process of multi-phonon relaxation. This quenching can be mitigated by using gain materials with small maximum phonon energies. In this work, mid-IR spectroscopic characterization of RE3+ doped cesium cadmium chloride (CsCdCl3) crystals was performed. The transition probabilities of RE3+ ions using Judd-Ofelt analysis as well as the multiphonon non-radiative transition rates in RE3+:CsCdCl3 were estimated. Obtained experimental results, inclusive of temperature dependent absorption and fluorescence studies, transition cross-sections, and fluorescence dynamics, were interpreted from the standpoint of optimization for diode-pumped ~3-5 um laser development.
A large number of rare-earth (RE) activated materials have been investigated to develop new solid state infrared (IR) laser sources for potential applications in atmospheric sensing, material processing, laser remote sensing, medicine, and free space communications. RE3+-doped low-phonon chalcogenide glasses have shown efficient mid-IR emission as well as lasing at room temperature. In this work, we report the results of a comparative study of mid-IR spectroscopic properties of RE3+ doped chalcogenide glasses (e.g. GaGeX (X= S, Se)) aimed at exploring their potential for efficient mid-IR laser operation.
Extending solid-state laser technology to longer wavelengths is difficult because the transitions that lead to mid-IR emission experience strong competition from the multiphonon-relaxation (MPR) which reduces the emission quantum efficiency. In this work, a comparative study of mid-IR (3-5 μm) spectroscopic properties on RE3+ ions doped in various low-phonon fluoride and chloride based crystals were explored. Obtained experimental results, including temperature dependent absorption and fluorescence, transition cross-sections, and fluorescence dynamics are discussed and the potential for efficient laser operation is evaluated. Ultimately, the chloride materials demonstrated more favorable laser parameters than the fluoride materials, including significantly longer upper laser level lifetimes.
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