Laser induced cooling of solids

Kashyap, Raman; Nemova, Galina

doi:10.1002/pssc.201000769

Cited by 5 publications

(3 citation statements)

References 10 publications

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“…λ f = ∫λI f (λ)dλ/∫I f (λ)dλ is the external mean fluorescence wavelength, where I f (λ) is the spectral power density of the measured fluorescence 29 .…”

Section: Theory Of Laser Coolingmentioning

confidence: 99%

Direct measurement of laser cooling of Yb:YAG crystal at atmospheric pressure using a fiber Bragg grating

et al. 2014

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Although Yb:YAG has been cooled in a vacuum environment 1 , we report for the first time an experimental demonstration of optical cooling at atmospheric pressure. A Yb:YAG crystal is supported on thin silica fibers, inside a matt-black chamber with air at atmospheric pressure, and pumped at 1029 nm in the pulsed and CW regimes. Direct measurement of the crystal surface temperature during pumping was made possible by using a low thermal-mass, transparent fiber Bragg grating (FBG) sensor. The FBG interrogation system has sufficient sensitivity to measure the background absorption of the sample to below 10 -4 cm -1 , and bulk cooling at a pump power as low as 17 mW. The dynamical measurement of the temperature allows the determination of the overall heat transfer coefficient of the sample in the air, of 22 W.m -2 K -1 . A temperature drop of 8.8 K from the chamber temperature is observed in the Yb:YAG crystal in air when pumped with 4.2 W at 1029 nm, close to 8.9 K observed in vacuum 1 . A background absorption α b = 2.9×10 -4 cm -1 is estimated with a pump wavelength at 1550 nm. Simulations predict further cooling when the sample's cross sectional area and the pump power are optimized, including absorption saturation effects. The choice of an efficient geometry, the use of a readily available temperature sensor in less controlled environments should simplify implementation of laser cooling systems and the development of commercial devices.

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“…λ f = ∫λI f (λ)dλ/∫I f (λ)dλ is the external mean fluorescence wavelength, where I f (λ) is the spectral power density of the measured fluorescence 29 .…”

Section: Theory Of Laser Coolingmentioning

confidence: 99%

Direct measurement of laser cooling of Yb:YAG crystal at atmospheric pressure using a fiber Bragg grating

et al. 2014

Self Cite

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“…λ f is the mean fluorescence wavelength, which is the wavelength of the photon with energy corresponding to the average of the energy of emitted photons, and can be calculated from the emission spectrum, through the expression (2), where I f (λ) is the spectral power density of the measured fluorescence [16]. …”

Section: Theory Of Laser Coolingmentioning

confidence: 99%

Prospects of optical refrigeration in oxyfluoride glasses and glass-ceramics: experiments

Filho

Ledemi³

et al. 2015

SPIE Proceedings

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We report on the characterization of oxyfluoride glasses and glass ceramics for their application in optical refrigeration. Oxide glasses are chemically and mechanically stable and relatively ease to handle and fabricate, but their high maximum phonon energy leads to a nonradiative decay rate which is unacceptable for optical refrigeration. On the other hand, low-maximum phonon energy hosts such as fluorides lack the desirable mechanical and chemical stabilities to make them widely used. The combination of the high chemical and mechanical stability of oxides and the low maximum phonon energy of fluorides make oxyfluorides strong potential candidates for wide-spread use in optical refrigeration. Glasses and ultra-transparent glass-ceramics of molar composition 30SiO 2 -15Al 2 O 3 -(27-x)CdF 2 -22PbF 2 -4YF 3 -xYbF 3 , with x = (2, 5, 8, 12, 16 and 20) mol % are investigated. The absorption and photoluminescence spectra, as well as the lifetime and the external quantum efficiency of the photoluminescence for these samples using an integrating sphere are reported. The effects of reabsorption on the measured mean fluorescence wavelength are also reported. The cooling efficiencies of the samples were measured as a function of the pump wavelength using a calorimetric method with a Ti:Sapphire laser pump source and a fiber Bragg grating sensor for a direct temperature measurement. Impurities and background absorption are also investigated using different pump sources and the calorimetric method. From a comparison of the cooling/heating performance of the oxyfluoride glasses and glass-ceramics containing various Yb 3+ amounts, we developed a strategy to realize and enhance optical refrigeration in this class of material.

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“…were prepared by citrate combustion method. The preparation method for powders is similar to those already used for various ferrites, and explained in other studies [9,10]. Metal nitrates and oxides were used as starting materials.…”

Section: Introductionmentioning

confidence: 99%

Magnetic studies on spinel ferrite nanoparticles and bulk samples synthesized by citrate combustion route

Dimri

Khanduri

Agarwal³

et al. 2020

Dae Solid State Physics Symposium 2019

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We report structural, microstructural and magnetic studies of ZnFe2O4, MnFe2O4 and mixed Mn-Ni-Zn ferrites in nanoparticles and bulk forms. Polycrystalline samples were prepared by citrate combustion synthesis, which resulted in homogeneous and nanograin powders. Particle sizes estimated from the XRD and SEM were found to be below 100 nm for the calcined powders (600°C) and above 300 nm range for the sintered (1200°C) samples. Substitution of Ni and Zn for Mn enhanced the saturation magnetization and coercivity, because of the redistribution between octahedral and tetrahedral iron sites. Curie temperature were found to be higher for the calcined powders as compared to corresponding sintered samples due to particle size effects.

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Laser induced cooling of solids

Cited by 5 publications

References 10 publications

Direct measurement of laser cooling of Yb:YAG crystal at atmospheric pressure using a fiber Bragg grating

Direct measurement of laser cooling of Yb:YAG crystal at atmospheric pressure using a fiber Bragg grating

Prospects of optical refrigeration in oxyfluoride glasses and glass-ceramics: experiments

Magnetic studies on spinel ferrite nanoparticles and bulk samples synthesized by citrate combustion route

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