Investigation of Yb-doped LiLuF<sub>4</sub>single crystals for optical cooling

Volpi, Azzurra; Cittadino, Giovanni; Lieto, A. Di; Cassanho, A.; Jenssen, H. P.; Tonelli, M.

doi:10.1117/1.oe.56.1.011105

Cited by 13 publications

(10 citation statements)

References 14 publications

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“…Upconversion in Yb:YLF was already reported in [17,32,45], and the observed emission spectrum were also identified and the underlying transitions were mostly recovered. Comparing our measurements with the published spectral data in literature, we have noticed that our 25% Yb +3 -doped YLF sample also possesses fingerprints of Er +3 , Ho +3 , and Tm +3 ions.…”

Section: Room-temperature Upconversion Spectrum Of 25% Yb-doped Ylf Samplesupporting

confidence: 53%

“…These radiation traps are not always well-known [38]: but in the case of Yb:YLF, existence of trace amounts of rare earth impurities (e.g. Er, Tm, Ho) is shown to create radiation quenching channels [17,32,45]. The energy transfer from the excited Yb ion into these impurities creates a loss of useful inversion, and results in concentration quenching of the fluorescence lifetime [15].…”

Section: Introductionmentioning

confidence: 99%

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Temperature and doping dependence of fluorescence lifetime in Yb:YLF (role of impurities)

et al. 2021

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We have investigated temperature and doping dependence of fluorescence lifetime in Yb:YLF crystals in the 78-300 K range, for samples with Yb-doping levels of 0.5%, 1 % and 25%. Radiation-trapping prolonged fluorescence lifetimes are first measured to understand the pros and cons of this inevitable process on fractional thermal load and laser gain. Later, pinhole method was used to acquire ideally trapping free fluoresce lifetimes. For the lowly Yb-doped samples, fluorescence lifetime was measured to be 1.97 ms and 2.1 ms at 78 K and 300 K, respectively. For the 25% Yb-doped sample, strong upconversion emission due to the presence of Er, Tm and Ho impurities were observed. A doubleexponential decay behavior, combined with excitation intensity dependent decay profile was also revealed for this highly doped sample. Even with the pinhole method, the 300 K fluorescence lifetimes was measured as 4.5 ms, showing the difficulty to acquire radiation-trapping free signals at high doping levels. Time dynamics of upconverted emission in different spectral regions were also recorded, which provides hints on the energy transfer mechanisms between the Yb ion and the other rare-earth impurities.

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Section: Room-temperature Upconversion Spectrum Of 25% Yb-doped Ylf Samplesupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Temperature and doping dependence of fluorescence lifetime in Yb:YLF (role of impurities)

et al. 2021

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“…Figure B contrasts the energy manifolds for La 3+ and Dy 3+ centers depicting the accessible X-ray absorption pathways and optical emission channels. We observe that, upon X-ray excitation of core La 3+ electrons, the generated electron–hole pairs are thermalized, thereby populating not only the 4 F 9/2 state but also the 4 I 15/2 state of Dy 3+ ; luminescence emission from these states yields bands at 570 and 540 nm, respectively. , The observed emission from thermally populated state 4 I 15/2 suggests the annihilation of lattice phonons, which is a signature of optical cooling …”

mentioning

confidence: 82%

Structure-Dependent Accessibility of Phonon-Coupled Radiative Relaxation Pathways Probed by X-ray-Excited Optical Luminescence

Udayakantha

Perera

Davidson

et al. 2021

J. Phys. Chem. Lett.

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Rare-earth scheelites represent a diverse family of compounds with multiple degrees of freedom, which enables the incorporation of a wide range of lanthanide color centers. Precise positioning of quantum objects is attainable by the choice of alkali cations and lattice connectivity of polyanion units. Herein, we report the structure-dependent energy transfer and lattice coupling of optical transitions in La 3+ -and Dy 3+ -containing scheelite-type double and quadruple molybdates NaLa 1−x Dy x (MoO 4 ) 2 and Na 5 La 1−x Dy x (MoO 4 ) 4 . X-ray excitation of La 3+ core states generates excited-state electron−hole pairs, which, upon thermalizing across interconnected REO 8 polyhedra in double molybdates, activate a phononcoupled excited state of Dy 3+ . A pronounced luminescence band is observed corresponding to optical cooling of the lattice upon preferential radiative relaxation from a "hot" state. In contrast, combined X-ray absorption near-edge structure and X-ray-excited optical luminescence studies reveal that such a lattice coupling mechanism is inaccessible in quadruple molybdates with a greater separation of La 3+ −Dy 3+ centers.

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“…LiLuF 4 (LLF) offers an attractive alternative to YLF for Bridgman growth. First, laser cooling has already been observed in Czochralski-grown LLF:Yb; − however, it has not yet been reported for Bridgman-grown LLF:Yb. Second, the LLF crystal is isomorphic to YLF (Lu 3+ replacing Y 3+ ) and exhibits a congruent melting behavior that facilitates the Bridgman growth.…”

Section: Crystal Growth Of Llf:ybmentioning

confidence: 99%

Bridgman Growth of Laser-Cooling-Grade LiLuF₄:Yb³⁺ Single Crystals

Volpi

Krämer

Biner

et al. 2021

Crystal Growth & Design

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The first demonstration of solid-state laser cooling in fluoride crystals grown by the Bridgman method is reported. We present advances in the Bridgman crystal growth of Yb 3+ -doped LiLuF 4 (LLF:Yb) single crystals in a radio-frequencyheated furnace. COMSOL Multiphysics numerical simulations are used to investigate the thermal gradients within the crucible during the crystal growth. Optical spectroscopy and laser-cooling efficiency measurements of three LLF:Yb crystals as well as laser cooling of a LLF:5%Yb crystal in a double-pass geometry from room temperature to 195 K are reported. Solid-state laser cooling is only possible in materials having extremely high chemical purity and crystal quality. The vertical Bridgman method is well suited for the growth of high-quality crystals on the few gram scale, a quantity that is compatible with purification techniques that aim to exceed the 99.999−99.9999% purity that is typical of commercial precursor materials. The results demonstrate that the small-scale Bridgman growth of LLF:Yb in glassy-carbon crucibles is able to produce laser-coolinggrade crystals, opening a new route to produce high-performance materials for solid-state optical refrigerators and radiation-balanced lasers.

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Investigation of Yb-doped LiLuF₄single crystals for optical cooling

Cited by 13 publications

References 14 publications

Temperature and doping dependence of fluorescence lifetime in Yb:YLF (role of impurities)

Temperature and doping dependence of fluorescence lifetime in Yb:YLF (role of impurities)

Structure-Dependent Accessibility of Phonon-Coupled Radiative Relaxation Pathways Probed by X-ray-Excited Optical Luminescence

Bridgman Growth of Laser-Cooling-Grade LiLuF₄:Yb³⁺ Single Crystals

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Investigation of Yb-doped LiLuF4single crystals for optical cooling

Cited by 13 publications

References 14 publications

Temperature and doping dependence of fluorescence lifetime in Yb:YLF (role of impurities)

Temperature and doping dependence of fluorescence lifetime in Yb:YLF (role of impurities)

Structure-Dependent Accessibility of Phonon-Coupled Radiative Relaxation Pathways Probed by X-ray-Excited Optical Luminescence

Bridgman Growth of Laser-Cooling-Grade LiLuF4:Yb3+ Single Crystals

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Investigation of Yb-doped LiLuF₄single crystals for optical cooling

Bridgman Growth of Laser-Cooling-Grade LiLuF₄:Yb³⁺ Single Crystals