73 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
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
Paraxial Theory of Direct Electro-optic Sampling of the Quantum Vacuum
No full textDirect detection of vacuum fluctuations and analysis of subcycle quantum properties of the electric field are explored by a paraxial quantum theory of ultrafast electro-optic sampling. The feasibility of such experiments is demonstrated by realistic calculations adopting a thin ZnTe electro-optic crystal and stable few-femtosecond laser pulses. We show that nonlinear mixing of a short near-infrared probe pulse with the multiterahertz vacuum field leads to an increase of the signal variance with respect to the shot noise level. The vacuum contribution increases significantly for appropriate length of the nonlinear crystal, short pulse duration, tight focusing, and a sufficiently large number of photons per probe pulse. If the vacuum input is squeezed, the signal variance depends on the probe delay. Temporal positions with a noise level below the pure vacuum may be traced with subcycle resolution.
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
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
Local laser cooling of Yb:YLF to 110 K
No full textMinimum achievable temperature of similar to 110 K is measured in a 5% doped Yb:YLF crystal at lambda = 1020 nm, corresponding to E4-E5 resonance of Stark manifold. This measurement is in excellent agreement with the laser cooling model and was made possible by employing a novel and sensitive implementation of differential luminescence thermometry using balanced photo-detectors. (C) 2011 Optical Society of Americ
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
Direct sampling of electric-field vacuum fluctuations
No full textThe ground state of quantum systems is characterized by zero-point motion. Those vacuum fluctuations are generally deemed an elusive phenomenon that manifests itself only indirectly. Here, we report direct detection of the vacuum fluctuations of electromagnetic radiation in free space. The ground-state electric field variance is found to be inversely proportional to the four-dimensional space-time volume sampled electro-optically with tightly focused few-femtosecond laser pulses. Sub-cycle temporal readout and nonlinear coupling far from resonance provide signals from purely virtual photons without amplification. Our findings enable an extreme time-domain approach to quantum physics with nondestructive access to the quantum state of light. Operating at multi-terahertz frequencies, such techniques might also allow time-resolved studies of intrinsic fluctuations of elementary excitations in condensed matter.publishe
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