Anharmonic versus relaxational sound damping in glasses. II. Vitreous silica

Vacher, R.; Courtens, E.; Foret, Marie

doi:10.1103/physrevb.72.214205

Cited by 94 publications

(156 citation statements)

References 52 publications

(161 reference statements)

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“…In an amorphous solid, ultrasonic attenuations can occur through thermally activated relaxation processes for T bath > 10 K (ref. 29). Below 5 K, interactions of phonons with two-level tunnelling defects become important 30 .…”

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confidence: 99%

Resolved-sideband and cryogenic cooling of an optomechanical resonator

2009

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Cooling a mechanical oscillator to its quantum ground state enables the exploration of the quantum nature and the quantum-classical boundary of an otherwise classical system 1-7 . In analogy to laser cooling of trapped ions 8 , ground-state cooling of an optomechanical system can in principle be achieved by radiation-pressure cooling in the resolved-sideband limit where the cavity photon lifetime far exceeds the mechanical oscillation period 9-11 . Here, we report the experimental demonstration of an optomechanical system that combines both resolved-sideband and cryogenic cooling. Mechanical oscillations of a deformed silica microsphere are coupled to optical whispering-gallery modes that can be excited through free-space evanescent coupling 12,13 . By precooling the system to 1.4 K, a final average phonon occupation as low as 37 quanta, limited by ultrasonic attenuation in silica, is achieved. With diminishing ultrasonic attenuation, we anticipate that the ground-state cooling can be achieved when the resonator is precooled to a few hundred millikelvin in a 3 He cryostat.In an optomechanical system, mechanical vibrations induce changes in the intracavity field as well as in the cavity-resonance frequency. Dynamical backaction of the radiation pressure can either damp or amplify the mechanical motion, depending on the laser detuning 14,15 . Radiation-pressure cooling as well as activeoptical-feedback cooling has been demonstrated in a variety of optomechanical systems [16][17][18][19][20][21][22] . Resolved-sideband cooling has also been realized recently in a toroidal silica resonator 11 . There are, however, considerable challenges in combining resolved-sideband cooling with cryogenic precooling for most optomechanical resonators 23 . The lowest average phonon occupation achieved in optomechanical resonators thus far remains above 1,000 quanta. In comparison, electromechanical systems can be cryogenically cooled to temperatures in the millikelvin range in a dilution refrigerator enabling an average phonon occupation as low as 25 (ref. 24). Dynamical backaction cooling in these systems has also been demonstrated recently 24,25 .We have developed and explored the use of deformed silica microspheres as a special type of optomechanical resonator which are convenient for experimental studies in a cryogenic environment. Unlike whispering-gallery modes (WGMs) in conventional symmetric optical resonators such as spherical or toroidal resonators 26,27 , WGMs in deformed non-axisymmetric microspheres can be effectively excited in free space through a directional evanescent tunnelling process. In these deformed resonators, the angle of incidence is no longer conserved. For WGMs near the equatorial plane, the angle of incidence becomes closest to the critical angle in regions 45 • away from either the long or short axis. At relatively small deformation, directional evanescent escape of WGMs can take place in these regions because the evanescent decay length as well as the evanescent tunnelling rate increases exponentially...

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Resolved-sideband and cryogenic cooling of an optomechanical resonator

2009

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“…[26]. Fitting the temperature dependence of the thermal relaxation time with an appropriate function, one obtains a model for the anharmonic term of eq (3) is added to the dynamical terms, then a qualitatively good agreement between UV data and the model can be appreciated, as shown by the dash-dotted line in figure 5.…”

Section: Discussionmentioning

confidence: 90%

“…This supports the description of the Akhiezer mechanism in terms of equation (3) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 [12] and US, circles [9]. [15], HiResUv, full circles (present work) and full squares [16], BLS, crosses [26] and dots [20]. …”

Section: Discussionmentioning

confidence: 99%

“…[15], HiResUv, full circles (present work) and full squares [16], BLS, crosses [26] and dots [20]. [12]; stars: US, 748 MHz [29]; crosses [26] and points [20]: BLS, 35 GHz. The continuous lines are the best fitted functions to the five US data sets with the model of equation (2) GHz, circles (present work and [16]).…”

Section: Discussionmentioning

confidence: 99%

“…We have analysed the US data using the following model for the TAR contribution (see [26] and references therein):…”

Section: Discussionmentioning

confidence: 99%

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