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The emerging field of photonic heat engines generally encompasses the science of manipulation of thermal state of matter using or involving electromagnetic and optical radiation. In particular, the field of laser cooling of solids (optical refrigeration) and the related areas of electroluminescence refrigeration and radiation-balanced lasers have been advancing at a rapid pace. Most recently, optical refrigeration in rare-earth-doped crystals has achieved sub-100K temperatures which has subsequently led to the demonstration of the world's first all-solid-state cryocooler. On the more fundamental side, optical refrigeration has been used to manipulate and investigate micro-mechanical systems and nano structures approaching their quantum-mechanical ground state. Mitigating and/or balancing the heat generated from quantum defects in solid-sate lasers by anti-Stokes fluorescence cooling has led to novel "athermal" or radiation-balanced lasers, which promises to eliminate thermal instabilities in high power solid-state lasers. In parallel, fundamental research on optical refrigeration and electroluminescence cooling in semiconductor structures has advanced immensely in recent years. In addition to direct applications of laser cooling, the related fields of thermophotonics and thermophotovoltaics exploit efficient harvesting of electro-and photo-luminescence in semiconductors for conversion of waste or solar heat into electricity.

We encourage the submission of papers dealing with experimental and theoretical studies as well as the applications of photonic heat engines including but not limited to the fields of optical and electroluminescence refrigeration, radiation balanced lasers, thermophotonics, thermophotovoltaics and optomechanical cooling.;
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Conference 12018

Photonic Heat Engines: Science and Applications IV

In person: 27 January 2022
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  • 1: Optical Cryocoolers
  • 2: Laser Cooling of Semiconductors
  • 3: Photonic Heat Engines
  • 4: Cooling and Radiation-Balanced Lasing in Yb:Silica Systems
  • 5: Laser Cooling of Rare-Earth Doped Nanocrystals


  • Submissions are accepted through 06-December
  • Notification of acceptance by 20-December

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Session 1: Optical Cryocoolers
Session Chair: Denis V. Seletskiy, Polytechnique Montréal (Canada)
Author(s): Umit Demirbas, Deutsches Elektronen-Synchrotron (Germany); Martin Kellert, Jelto Thesinga, Simon Reuter, Mikhail Pergament, Franz X. Kärtner, Ctr. for Free-Electron Laser Science (Germany)
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Yb:YLF crystal with near-unity quantum efficiency attracts the attention of researchers in high-power laser development and laser-cooling communities. Here, we will first present temperature dependence of important laser related parameters in Yb:YLF such as fluorescence lifetime, absorption cross section, emission cross section and gain in the 78-300 K range. We will then discuss the in situ optical temperature estimation methods that could be used to accurately estimate Yb:YLF crystal temperature. Later, we will review our recent lasing/amplification results with cryogenic Yb:YLF systems, where we have achieved output powers exceeding 500 W, pulse energies above 300 mJ with efficiencies above 70%.
Author(s): Mansoor Sheik-Bahae, Jackson Kock, The Univ. of New Mexico (United States)
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The effects of amplified spontaneous emission (ASE) as well as absorption saturation in cryogenic optical refrigeration in rare-earth doped materials are analyzed theoretically. It is seen that ASE may pose a limitation on power scaling under strong feedback conditions (i.e. in high finesse pump circulator cavities). Absorption saturation may have similar effect depending on the value of the background absorption.
Author(s): Hiroki Tanaka, Stefan Püschel, Felix Mauerhoff, Sascha Kalusniak, Christian Kränkel, Leibniz-Institut für Kristallzüchtung (Germany)
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Crystalline materials with suppressed impurity concentrations are essential elements for efficient solid-state laser cooling based on anti-Stokes fluorescence. So far, fluoride single crystals doped with rare earth ions have been demonstrated as efficient laser cooling media. We report on our growth activities on high purity rare-earth-doped fluoride single crystals for this specific application. We grew a variety of fluoride crystals doped with ytterbium by the Czochralski method. These crystals are studied by temperature-dependent spectroscopy to fully reveal their potential as laser cooling media. The cooling efficiency of the grown crystals is directly evaluated in a laser-induced cooling setup in vacuo.
Author(s): Francesco Caminati, Univ. di Pisa (Italy); Giovanni Cittadino, Eugenio Damiano, MEGA Materials s.r.l. (Italy), Univ. di Pisa (Italy); Alberto Di Lieto, Mauro Tonelli, Univ. di Pisa (Italy), MEGA Materials s.r.l. (Italy)
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To have a better understanding of the mechanisms that can reduce optical refrigeration efficiency, we highlight loss mechanisms that reduce the cooling performance of a Yb:YLF monocrystal as the presence of impurities and fluorescence reabsorption. We show how the presence of impurities can be inferred by measuring the mean lifetime of the Yb optical transition. We measure how trace amounts of other rare earth ions can increase the background absorption and be detrimental for optical refrigeration by exciting an Yb:YLF sample with two laser sources. We report the first practical demonstration of the negative effect of fluorescence reabsorption on the cooling performance.
Author(s): Jackson Kock, Azzurra Volpi, Alexander R. Albrecht, Duncan McGraw, The Univ. of New Mexico (United States); Richard I. Epstein, ThermoDynamic Films LLC (United States); Mansoor Sheik-Bahae, The Univ. of New Mexico (United States)
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Optical refrigeration of Yb:YLF is used to cool an arbitrary payload. An astigmatic Herriott cell enhances the total pump laser absorption by keeping the average pump intensity below the saturation while minimizing the leakage from the cavity. A spectrally-selective reflection coating mitigates the effects of amplified spontaneous emission and parasitic lasing, which limit the power scaling for temperatures <140 K. Direct cooling of the entire clamshell and shielding stray fluorescence prevents adverse heating of the crystal from its surroundings. Finally, an improved Differential Luminescence Thermometry (DLT) technique is used to measure the crystal temperature with higher accuracy and precision.
Session 2: Laser Cooling of Semiconductors
Session Chair: Peter J. Pauzauskie, Univ. of Washington (United States)
Author(s): A. Paul Alivisatos, Lawrence Berkeley National Lab. (United States)
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Lumophores that logarithmically approach unity quantum yield are important components for future energy conversion devices such as luminescent concentrators, optical refrigerators, and down converting solar greenhouses. This talk will review the potential for colloidal nanocrystal quantum dots to meet the requirements as lumophores for such demanding applications. The case of CdSe@CdS quantum dots will be contrasted with cesium lead halide perovskite nanocrystals. The new photothermal threshold quantum yield measurement technique will be introduced as well. This method can presently distinguish a part in 1000 deviation below unity quantum yield, and may soon be able to see parts in 10000. With these techniques, the influence of even one individual surface defect can be seen, and can provide a stringent test for the limits of nanocrystal lumophores.
Author(s): Mansoor Sheik-Bahae, The Univ. of New Mexico (United States)
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The feasibility of space-borne no-vibration optical cryocoolers based on GaAs for high precision petrology and optical clock applications will be discussed. In particular, theoretical analysis and reasonable estimations will be presented for a cryocooler device using GaAs at T=16.8K suitable for cooling the silicon reference cavity developed by NIST.
Author(s): Jacob B. Khurgin, Johns Hopkins Univ. (United States)
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The idea of Raman cooling of semiconductors has been around for quite some time, but no detailed analysis of what are the attainable cooling rates and temperature has been given. We provide such an analysis for the cases resonant Raman scattering with and without exciton effects and show that one cannot bring down the temperature to less than 250K under even the best conceivable conditions. At the same time, Raman it may be possible to operate a (Stokes) Raman laser that is cooled by Anti-Stokes scattering at around 300K
Author(s): Chaman Gupta, Anupum Pant, Xiaojing Xia, Greg Felsted, Univ. of Washington (United States); Katharina Senkalla, Univ. Ulm (Germany); Scott T. Dunham, Univ. of Washington (United States); Fedor Jelezko, Univ. Ulm (Germany); Peter J. Pauzauskie, Univ. of Washington (United States), Pacific Northwest National Lab. (United States)
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The H3 center in diamond has been shown to exhibit several promising characteristics for laser cooling applications including a neutral charge state, high radiative quantum yield, and efficient anti-Stokes photoluminescence. In this work, we show that upon excitation with a 532 nm laser, bulk diamond crystals doped with H3 centers emit efficient up-conversion photoluminescence and also show significantly reduced photothermal heating relative to crystals doped with NV centers. These results encourage future exploration of techniques for H3 enrichment in diamonds at high-pressure, high-temperature conditions for the simultaneous anti-Stokes fluorescence cooling and radiation balanced lasing in semiconductor materials.
Session 3: Photonic Heat Engines
Session Chair: Jacob B. Khurgin, Johns Hopkins Univ. (United States)
Author(s): Benoit Behaghel, Ivan Radevici, Alberto Casado, Ahmad Shahahmadi, Jani Oksanen, Aalto Univ. School of Science (Finland)
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Semiconductor light emitters and solar cells are approaching a stage where their reciprocity and thermodynamics reveal new possibilities for optical refrigeration and thermal energy harvesting. Our studies suggest that III-V materials already allow local cooling upon light emission. However, harnessing the effect for practical applications necessitates still better quantitative understanding of the material and device properties as well as new solutions for thermal insulation, current spreading and light management. Here, we overview the main possibilities for optical heat pumps and waste heat energy harvesting, and discuss selected challenges in developing the devices.
Session 4: Cooling and Radiation-Balanced Lasing in Yb:Silica Systems
Session Chair: Denis V. Seletskiy, Polytechnique Montréal (Canada)
Author(s): Michel J. F. Digonnet, Stanford Univ. (United States); Pierre-Baptiste Vigneron, Univ. Savoie Mont Blanc (France); John M. Ballato, Clemson Univ. (United States); Peter Dragic, Univ. of Illinois (United States)
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Author(s): Brian Topper, Mostafa Peysokhan, Alexander R. Albrecht, The Univ. of New Mexico (United States); Angel S. Flores, Air Force Research Lab. (United States); Stefan Kuhn, Denny Häßner, Sigrun Hein, Christian Hupel, Johannes Nold, Nicoletta Haarlammert, Thomas Schreiber, Fraunhofer-Institut für Angewandte Optik und Feinmechanik IOF (Germany); Mansoor Sheik-Bahae, Arash Mafi, The Univ. of New Mexico (United States)
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Record laser cooling of Yb-doped silica by 18.4 K and 6.3 K was observed in vacuum and atmospheric pressure conditions, respectively. We present a detailed investigation into the optical refrigeration of ytterbium doped silica glass for both in-air and in-vacuum conditions using various pump powers. Temperature measurements were made relative to the room temperature using thermal camera imaging and differential luminescence thermometry. Through analysis of the temporal behavior of the temperature differential at the start of the in-vacuum experiments, we find the cooling efficiency of the studied silicates to be 0.66 ± 0.07%.
Author(s): Azzurra Volpi, Alexander R. Albrecht, Jackson Kock, Mingyang Zhang, The Univ. of New Mexico (United States); Markus P. Hehlen, Los Alamos National Lab. (United States); Mansoor Sheik-Bahae, The Univ. of New Mexico (United States)
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In radiation-balanced lasers, anti-Stokes fluorescence is used to minimize heat generation in the gain medium due to optical pumping in presence of quantum defect and other nonradiative processes. Heat generation cause thermo-optic distortions that limit the scaling to high power with high brightness. Here, experimental data of radiation-balanced operation and beam area scaling in CW Yb:YLF disk lasers are presented. Multipass pumping and laser cavity design are discussed. A mirrored disk configuration is implemented to investigate active thermal management along the facets of the disk for mitigating large radial thermal gradients, that are expected for large beam area ( ~ 1cm2) required for high power (~ kW) operation, even with zero net heat generation.
Session 5: Laser Cooling of Rare-Earth Doped Nanocrystals
Session Chairs: Peter J. Pauzauskie, Univ. of Washington (United States), Masaru K. Kuno, Univ. of Notre Dame (United States)
Author(s): Daniel Jaque, Patricia Haro-González, Univ. Autónoma de Madrid (Spain)
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In this work we demonstrate laser cooling in liquids on a micrometric scale by using colloidal microparticles doped with ytterbium ions. These microparticles behave as cooling elements thanks to their anti-stokes luminescence. The novel point of our work is that laser radiation produces laser refrigeration and linear and angular transfer of momentum that allows cooling during remote particle manipulation and rotation. This dual function of laser radiation opens the door to new applications based on the use of portable micro-refrigerants. In addition, we demonstrate for the first time how analyzing rotation dynamics is a new and simpler way to determine, in real time, the magnitude of cooling. In other words, we show how laser light can heat, cool, move and rotate our particles simultaneously. All this without requiring complicated experimental systems.
Author(s): Yuebing Zheng, The Univ. of Texas at Austin (United States)
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Heat-mediated optical manipulation exploits tailorable opto-thermo-matter interactions and rich mass transport dynamics to enable versatile control of matter of various compositions, shapes, and sizes. I present our progress in developing and applying a series of heat-mediated optical manipulation techniques, which range from opto-refrigerative tweezers to opto-thermoelectric tweezers and machines.
Author(s): Greg Felsted, Anupum Pant, Alexander B. Bard, Xiaojing Xia, Univ. of Washington (United States); Danika R. Luntz-Martin, Siamak Dadras, Univ. of Rochester (United States); Shuai Zhang, Univ. of Washington (United States); Nick Vamivakas, Univ. of Rochester (United States); Peter J. Pauzauskie, Univ. of Washington (United States)
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Hexagonal sodium yttrium fluoride (β-NaYF) is a promising material for optical refrigeration due to the narrow crystal field splitting of the Yb(III) ion. However, growing single crystals of β-NaYF remains a challenge due to thermal expansion stresses during melt growth. We demonstrate a hydrothermal synthesis of β-NaYF with widely tunable aspect ratios that match computationally predicted cavity resonances. The β-NaYF microcrystals contain 10% Yb(III) cations and are used to build optomechanical laser-refrigeration cantilever devices. Laser refrigeration of these devices shows cooling up to 12.5°C, which is measured using the cantilever’s fundamental eigenfrequency and photoluminescence from the Yb(III) ions.
Author(s): Jyothis Thomas, Polytechnique Montréal (Canada); Thomas Meyneng, Univ. Laval (Canada); Patricia Manarazan, Jean-Sebastien Boisvert, Polytechnique Montréal (Canada); Steeve Morency, Nicolas Grégoire, Univ. Laval (Canada); Denis Seletskiy, Polytechnique Montréal (Canada); Younès Messaddeq, Univ. Laval (Canada); Raman Kashyap, Polytechnique Montréal (Canada)
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Ytterbium doped optical fibers have recently attracted great attention as a novel material candidate for optical refrigeration. In this study we report on the structural and optical properties of purified ytterbium doped silica optical fibers with different rare earth ion concentration with Y2O3 nanoparticles for laser cooling applications. The temperature dependent absorption spectra, photoluminescence spectra, quantum efficiency and lifetime are presented. The background absorption coefficient as well as pump wavelength dependent temperature change of the fibers are measured using a fiber Bragg grating sensor.
Author(s): Xiaojing Xia, Robert G. Felsted, Diwash Dhakal, Peter J. Pauzauskie, Univ. of Washington (United States)
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Heat engines for space applications and radiation balanced lasers need to withstand radiation damage. The lasere cooling function of Yb:YLF microcrystals after X-ray radiation was studied. F-centers stable at room temperature were induced after X-ray irradiation. Such point defects were confirmed with electron paramagnetic resonance spectroscopy and thermal luminescence. The cooling performance of the YLF microcrystals deteriorated after irradiation, which is caused by F-center induced increased background absorption and/or higher non-radiative relaxation rate. The absorption spectrum and Yb3+ excited state lifetime were measured to investigate the failure of optical refrigeration in X-ray irradiated Yb:YLF microcrystals.
Author(s): Arjun Senthil, Mark V. Reymatias, Shruti I. Gharde, Aadit Sharma, Rafael A. Castro, Ciara Murphy, Nathan J. Withers, Gennady A. Smolyakov, Alexander Neumann, The Univ. of New Mexico (United States); Sergei A. Ivanov, John D. Watt, Los Alamos National Lab. (United States); Dale L. Huber, Sandia National Labs. (United States); Marek Osinski, The Univ. of New Mexico (United States)
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We have successfully synthesized lithium yttrium lithium fluoride (YLF) nanocrystals doped with ytterbium. The Yb content was varied between 1% and 10%. TEM analysis shows a monodisperse size distribution, with the nanocrystal size of ~20 nm. The nanocrystals emit in near-infrared, with the emission spectrum extending from 960 nm to 1060 nm when excited with the 900 nm light. Strong anti-Stokes photoluminescence was observed when using excitation wavelengths ranging from 1010 nm to 1020 nm. The temperature-dependence of the anti-Stokes photoluminescence was measured over the range from 10 °C till 70 °C. These nanocrystals have a high potential to be used in optical cooling applications.
Conference Chair
Polytechnique Montréal (Canada)
Conference Chair
Univ. of Notre Dame (United States)
Conference Chair
Peter J. Pauzauskie
Univ. of Washington (United States)
Program Committee
Stanford Univ. (United States)
Program Committee
Univ. of Illinois (United States)
Program Committee
ThermoDynamic Films LLC (United States)
Program Committee
Fedor Jelezko
Univ. Ulm (Germany)
Program Committee
Polytechnique Montréal (Canada)
Program Committee
The Univ. of New Mexico (United States)
Program Committee
Ali Sayir
Air Force Office of Scientific Research (United States)
Program Committee
The Univ. of New Mexico (United States)
Program Committee
Univ. di Pisa (Italy)
Program Committee
Eli Yablonovitch
Univ. of California, Berkeley (United States)
Additional Information