Electron–phonon coupling in Yb3+: LiNbO3 laser crystal

The enhanced laser cooling performance of rare-earth-ion-doped nanocrystalline powders is predicted, compared to the bulk material, using Yb 3+ :Y 2 O 3 as the model material. This is achieved by enhancing the off-resonance, phonon-assisted absorption, which is proportional to the three factors considered in this paper: the dopant concentration, the pumping field energy, and the excitation coefficient. Using the energy transfer theory for concentration quenching, the optimum concentration corresponding to the maximum cooling power is found to be considerably larger than the currently used value, suggesting noticeable enhancement effects for laser cooling. The pumping field energy is enhanced in random nanopowders compared with bulk crystals under the same irradiation, due to the multiple scattering of photons. Photons are thus localized in the medium and do not propagate through, increasing the photon absorption of the pumping beam ͑and it is shown that the reabsorption of the fluorescence is negligible͒. Using molecular dynamics simulations, the phonon density of states ͑DOS͒ of the nanopowder is calculated, and found to have broadened modes, and extended small tails at low and high frequencies. The second-order electronic transition rate for the anti-Stokes luminescence is calculated using the Fermi golden rule, which includes the influence of this phonon DOS, and is shown to have enhancement effects on the laser cooling efficiency using nanopowders. It is finally concluded that these three enhancement mechanisms are essentially to increase the population of the three participating carriers ͑electron, photon, and phonon͒ in the interacting volume, and this also points out directions for enhancing laser cooling performance in bulk materials.

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“…This result implies that the excitation spectra can be associated with the phonon spectra, as observed in Ref. 52…”

Section: ͑57͒supporting

confidence: 68%

Enhanced laser cooling of rare-earth-ion-doped nanocrystalline powders

Ruan

Kaviany

2006

Phys. Rev. B

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“…This structure can be related to vibronic transitions involving split components of the 2 F 5/2 excited state. As pointed out in most of Yb 3+ doped crystals, strong electron-phonon interaction takes place, and the electronic transitions are accompanied by vibronic sidebands which in some cases could exceed and mask the zero-phonon transitions probabilities [22][23][24]. Secondly, a clear doublet structure around 980 nm is observed in the spectra for both polarizations.…”

Section: Absorption Spectramentioning

confidence: 69%

Spectroscopic study of Y b³⁺centres in the Y Al₃(BO₃)₄nonlinear laser crystal

Ramı́rez

Bausá

Jaque

et al. 2003

J. Phys.: Condens. Matter

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A spectroscopic study of Y b3+ ions in Y Al3(BO3)4 laser crystals is presented. Polarized absorption and site selective spectroscopy experiments at low temperature have been used to determine the presence of two different Y b3+ centres in this host crystal in the concentration range 0.2–9 at.%. The contribution of these centres to the absorption spectra has been found to be dependent on the total Y b3+ concentration, and the Stark energy level diagrams corresponding to the different Y b3+ centres have been determined. The importance of electron–phonon coupling in the optical transitions of Y b3+ ions has been also pointed out.

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“…The 0Ј → 1,2,3 lines display a dominant homogeneous broadening because of a strong electronphonon interaction typical of ytterbium doped crystals. 28,29 On the contrary, the 0Ј → 0 band shows a dominant inhomogeneous broadening, which is larger than that usually observed for the majority of ytterbium doped crystals. 25 This inhomogeneous broadening is due to the previously described large lattice site disorder and, very likely, to the contribution of nonequivalent Yb 3+ centers.…”

Section: Low Temperature Spectra: Site Selective Spectroscopymentioning

confidence: 56%

Thermal hysteresis in the luminescence ofYb3+ions inSr0.6Ba0.4Nb2
Ramı́rez
¹
,
Bausá
²
,
Speghini
³

et al. 2006
Phys. Rev. B
31
0
22
0
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The optical spectra of Yb 3+ ions in congruent, Sr 0.6 Ba 0.4 Nb 2 O 6 ͑SBN͒ crystals have been systematically investigated in a broad temperature range ͑10-420 K͒. Laser site selective low temperature fluorescence spectra have shown that Yb 3+ ions enter in four different cationic lattice sites. A thermal hysteresis in both bandwidth and luminescence intensity of Yb 3+ ions has been detected in the temperature range ͑300-400 K͒ around the ferro to paraelectric phase transition. This behavior has been explained as a result of the local structural modifications that take place around the Yb 3+ ions when the crystal becomes nonpolar, which affect in a different way the luminescence of Yb 3+ ions located in the different sites. Off-congruent SBN crystals activated with Yb 3+ ions have been grown and investigated in order to examine the possibilities of extending the detected hysteretic behavior to other temperature ranges.

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Electron–phonon coupling in Yb3+: LiNbO3 laser crystal

Cited by 16 publications

References 18 publications

Enhanced laser cooling of rare-earth-ion-doped nanocrystalline powders

Enhanced laser cooling of rare-earth-ion-doped nanocrystalline powders

Spectroscopic study of Y b³⁺centres in the Y Al₃(BO₃)₄nonlinear laser crystal

Thermal hysteresis in the luminescence ofYb3+ions inSr0.6Ba0.4Nb2
Ramı́rez
¹
,
Bausá
²
,
Speghini
³

et al. 2006
Phys. Rev. B
31
0
22
0
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Electron–phonon coupling in Yb3+: LiNbO3 laser crystal

Cited by 16 publications

References 18 publications

Enhanced laser cooling of rare-earth-ion-doped nanocrystalline powders

Enhanced laser cooling of rare-earth-ion-doped nanocrystalline powders

Spectroscopic study of Y b3+centres in the Y Al3(BO3)4nonlinear laser crystal

Thermal hysteresis in the luminescence ofYb3+ions inSr0.6Ba0.4Nb2Ramı́rez1, Bausá2, Speghini3 et al. 2006Phys. Rev. B310220View full textAdd to dashboardCite

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Spectroscopic study of Y b³⁺centres in the Y Al₃(BO₃)₄nonlinear laser crystal

Thermal hysteresis in the luminescence ofYb3+ions inSr0.6Ba0.4Nb2
Ramı́rez
¹
,
Bausá
²
,
Speghini
³

et al. 2006
Phys. Rev. B
31
0
22
0
View full text Add to dashboard Cite