3,253 research outputs found
Optical refrigeration progress: Cooling below NIST cryogenic temperature of 123K
No full textWe have achieved cryogenic optical refrigeration with a record low temperature in optical refrigeration by cooling 5% wt.Yb:YLF crystal to 119K ± 1K (∼-154 C) at l=1020 nm corresponding to its E4-E5 Stark manifold resonance with an estimated cooling power of 18 mW. This demonstration confirms the predicted minimum achievable temperature (MAT). Further cooling is achievable as shown by measurements of a doping study where a 10% wt. Yb:YLF crystal with reduced parasitic heating has predicted cooling below 100K (∼-173K). © 2013 SPIE
Self-referenced subcycle metrology of quantum fields
No full textWe propose and analyze a new time-domain method for subcycle metrology of
quantum electric fields using a combination of a 3rd order nonlinear optical
process and homodyne detection with a local oscillator (LO) field. The new
method enables isolation of intrinsically weak quantum noise contribution by
subtraction of the shot noise of the LO on a pulse-by-pulse basis. Together
with the centro-symmetric character of the nonlinearity, our method unlocks
novel opportunities toward terahertz and mid-infrared quantum field
metrologies
Contrasting activity profile of two distributed cortical networks as a function of attentional demands
No full textThe original publication is available at http://www.jneurosci.orgThis work was supported by R01 grant MH-073610 from the National Institutes of Health to Denis Paré
Influence of other rare earth ions on the optical refrigeration efficiency in Yb:YLF crystals
No full textWe investigated the effect of rare earth impurities on the cooling efficiency of Yb3+:LiYF4 (Yb:YLF). The refrigeration performance of two single crystals, doped with 5%-at. Yb and with identical history but with different amount of contaminations, have been compared by measuring the cooling efficiency curves. Spectroscopic and elemental analyses of the samples have been carried out to identify the contaminants, to quantify their concentrations and to understand their effect on the cooling efficiencies. A model of energy transfer processes between Yb and other rare earth ions is suggested, identifying Erbium and Holmium as elements that produce a detrimental effect on the cooling performance
Optical refrigeration to 119 K, below National Institute of Standards and Technology cryogenic temperature
No full textWe report on bulk optical refrigeration of Yb:YLF crystal to a temperature of ∼124 K, starting from the ambient. This
is achieved by pumping the E4-E5 Stark multiplet transition at ∼1020 nm. A lower temperature of 119 +/- 1 K
(∼ − 154C) with available cooling power of 18 mW is attained when the temperature of the surrounding crystal
is reduced to 210 K. This result is within only a few degrees of the minimum achievable temperature of our crystal
and signifies the bulk solid-state laser cooling below the National Institute of Standards and Technology (NIST)-
defined cryogenic temperature of 123 K. © 2013 Optical Society of Americ
Laser cooling of solids to cryogenic temperatures
No full textLaser radiation has been used to cool matter ranging from dilute gases to micromechanical oscillators. In Doppler cooling of gases, the translational energy of atoms is lowered through interaction with a laser field(1,2). Recently, cooling of a high-density gas through collisional redistribution of radiation has been demonstrated(3). In laser cooling of solids, heat is removed through the annihilation of lattice vibrations in the process of anti-Stokes fluorescence(4-6). Since its initial observation in 1995, research(7-15) has led to achieving a temperature of 208 K in ytterbium-doped glass(16). In this Letter, we report laser cooling of ytterbium-doped LiYF(4) crystal to a temperature of similar to 155 K starting from ambient, with a cooling power of 90 mW. This is achieved by making use of the Stark manifold resonance in a crystalline host, and demonstrates the lowest temperature achieved to date without the use of cryogens or mechanical refrigeration. Optical refrigeration has entered the cryogenic regime, surpassing the performance of multi-stage Peltier coolers
Laser cooling of a semiconductor load to 165 K
No full textWe demonstrate cooling of a 2 micron thick GaAs/InGaP double-heterostructure to 165 K from ambient using an all-solid-state optical refrigerator. Cooler is comprised of Yb(3+)-doped YLF crystal, utilizing 3.5 Watts of absorbed power near the E4-E5 Stark manifold transition. (C) 2010 Optical Society of Americ
Is Tolerance Political? An Interview with Denis Lacorne
No full textcontribution à un site webDenis Lacorne is the author of "The Limits of Tolerance. Enlightenment Values and Religious Fanaticism" (Columbia University Press, 2019), the English translation of "Les limites de la tolérance" (Gallimard, awarded the Prix Montyon by the Académie Française). In his book, which is intellectually very inspiring because of the many questions it addresses and raises, Denis Lacorne traces the emergence of the notion of tolerance from its early thinkers to the Age of Enlightenment and finally questions the notion and its various understandings through more recent events in France and the United States. What is tolerance? Is tolerance political? Interview by Miriam Périer, CER
Precise determination of minimum achievable temperature for solid-state optical refrigeration
No full textWe measure the minimum achievable temperature (MAT) as a function of excitation wavelength in anti-Stokes fluorescence cooling of high purity Yb3+-doped LiYF4 (Yb:YLF) crystal. Such measurements were obtained by developing a sensitive noncontact thermometry that is based on a two-band differential luminescence spectroscopy using balanced photo-detectors. These measurements are in excellent agreement with the prediction of the laser cooling model and identify MAT of 110 K at 1020 nm, corresponding to E4–E5 Stark manifold transition in Yb:YLF crystal
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