Mode-dependent mechanical losses in disc resonators

Cagnoli, G.; Lorenzini, M.; Cesarini, E.; Piergiovanni, F.; Granata, M.; Heinert, D.; Martelli, F.; Nawrodt, R.; Amato, A.; Cassar, Quentin; Dickmann, Johannes; Kroker, Stefanie; Lumaca, D.; Malhaire, C.; Hurtado, Carol Bibiana Rojas

doi:10.1016/j.physleta.2017.05.065

Cited by 28 publications

(42 citation statements)

References 17 publications

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“…Further work is needed to quantify their effect on the bulk and shear loss angle results. In previous works [21], the mechanical quality factors of uncoated silica disks were found to be dependent and limited by loss mechanisms at the unpolished edge, and were also found to degrade over time. The silica disks used in this work have an optical quality polished edge, and the mechanical quality factors have been measured before the film deposition, to ensure a correct subtraction of the background due to the substrate.…”

Section: Loss Angle Analysismentioning

confidence: 84%

Method for the experimental measurement of bulk and shear loss angles in amorphous thin films

et al. 2020

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Brownian thermal noise is a limiting factor for the sensitivity of many high precision metrology applications, among other gravitational-wave detectors. The origin of Brownian noise can be traced down to internal friction in the amorphous materials that are used for the high reflection coatings. To properly characterize the internal friction in an amorphous material, one needs to consider separately the bulk and shear losses. In most of previous works the two loss angles were considered equal, although without any first principle motivation. In this work we present a method that can be used to extract the material bulk and shear loss angles, based on current state-of-the-art coating ring-down measurement systems. We also show that for titania-doped tantala, a material commonly used in gravitational-wave detector coatings, the experimental data strongly favor a model with two different and distinct loss angles, over the simpler case of one single loss angle. arXiv:1911.12277v2 [cond-mat.mtrl-sci]

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Section: Loss Angle Analysismentioning

confidence: 84%

Method for the experimental measurement of bulk and shear loss angles in amorphous thin films

et al. 2020

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“…where φ s_i is the measured loss of the bare substrate. D i is the so-called dilution factor, defined as the ratio of the elastic energy of the coating, E c , to the elastic energy of the coated disk, [27]. The best-fit parameters of each data set are listed in Table 1.…”

Section: Measurementmentioning

confidence: 99%

“…2 compares the internal friction of coating materials of Advanced LIGO, Advanced Virgo and KAGRA mirrors, Table 1 summarizes their mechanical properties; all data have been measured with our GeNS system. We used a power-law model φ c ( f ) = a f b to describe the observed frequency-dependent behavior of the coating internal friction [25][26][27]. Fig.…”

Section: Measurementmentioning

confidence: 99%

“…Internal friction of Ta 2 O 5 (top row) and SiO 2 (bottom row) coatings before (left column) and after (right column) 10-h in-air annealing at 500 • C, deposited by different coaters: GC, DIBS and SPECTOR; shaded regions represent uncertainties from fitting a frequency-dependent power-law loss model to each sample set: φ c ( f ) = a f b for Ta 2 O 5and φ c ( f ) = a f b + dφ e for SiO 2 , where the dφ e term is the spurious contribution of the coated edge of the sample[27]. The scale of each plot is adapted to highlight differences or similarities between different data sets.…”

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confidence: 99%

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Progress in the measurement and reduction of thermal noise in optical coatings for gravitational-wave detectors

et al. 2020

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Coating thermal noise is a fundamental limit for precision experiments based on optical and quantum transducers. In this review, after a brief overview of the techniques for coating thermal noise measurements, we present the latest world-wide research activity on low-noise coatings, with a focus on the results obtained at the Laboratoire des Matériaux Avancés. We report new updated values for the Ta 2 O 5 , Ta 2 O 5 -TiO 2 and SiO 2 coatings of the Advanced LIGO, Advanced Virgo and KAGRA detectors, and new results from sputtered Nb 2 O 5 , TiO 2 -Nb 2 O 5 , Ta 2 O 5 -ZrO 2 , MgF 2 , AlF 3 and silicon nitride coatings. Amorphous silicon, crystalline coatings, high-temperature deposition, multi-material coatings and composite layers are also briefly discussed, together with the latest developments of structural analyses and models. The issue of coating thermal noiseThe Laboratoire des Matériaux Avancés (LMA, now a division of the newly created Institut de Physique des 2 Infinis de Lyon) has provided the current high-reflection (HR) and anti-reflective (AR) coatings of the most critical optics of Advanced LIGO [1], Advanced Virgo [2] and KAGRA [3]. In these gravitational-wave (GW) interferometers, large and massive suspended mirrors (typically with ∅ = 35 cm, t = 20 cm, m = 40 kg) form the km-long resonant Fabry-Perot cavities where the astrophysical signals are embedded in the laser beam phase. Their HR coatings are Bragg reflectors of alternate layers of ion-beam-sputtered (IBS) low-and high-refractive index materials, which feature outstanding optical properties [4]. At the same time, these amorphous coatings are the source of coating thermal noise (CTN), which is a severe limitation to the detector sensitivity [1,2].In GW interferometers, thermal noise arises from fluctuations of the mirror surface under the random motion of particles in coatings and substrates [5,6]. Its power spectral density is determined by the amount of internal friction within the mirror materials, via the fluctuationdissipation theorem [7]: the higher the elastic energy loss, the higher the thermal noise level. As the coating loss is usually several orders of magnitude larger than that of the substrate [8,9], CTN is the dominant source of noise in the mirrors.More generally, CTN is a fundamental limit for precision experiments based on optical and quantum transducers, such as opto-mechanical resonators [10], frequency standards [11] and quantum computers [12]. In the last two decades, a considerable research effort has been committed to the measurement and the reduction of CTN.

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“…Zener solved the problem for a beam, in which two dimensions are neglected with respect to the beam length [11]. Cagnoli et al [12] presented results valid for a cylinder, that eventually assume a simpler form for a thin disc in which one of the three dimensions is negligible. The approach to compute the thermoelastic loss follows the derivation outlined by Zener, based on the evaluation of entropy variation.…”

Section: Thermoelastic Damping Calculationmentioning

confidence: 99%

The Virgo Coating Collaboration: a detailed study on thermoelasticity in crystalline materials and other research lines

Cesarini¹,

Lorenzini²,

Amato³

et al. 2018

Proceedings of Gravitational-Waves Science&Technology Symposium — PoS(GRASS2018)

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The visibility distance of interferometric gravitational wave detectors is limited by mirror thermal noise at mid-range frequency, where the first coalescence GW signals have been detected and where many others are expected in the next future. In particular, for enhanced second generation and third generation we need to increase the performance of the test mass multilayer reflective coatings. The Virgo collaboration is setting up a coating R&D group on many issues, including especially metrology (loss angle measurements, thermoelastic effect modeling), new materials (new oxides, nitrates, fluoride, new cosputtered mixing and nanolayered composites) completely characterized (optically, mechanically and morphologically), optimization of deposition parameters, with the aim of developing new coating materials and technologies for the AdVirgo upgrades and for future detectors. Another objective is to understand the losses in amorphous materials, framing coating research in the more general context of the physics of glasses and amorphous materials. One of the developed research lines is the study of thermoelastic damping in those crystalline materials that are promising candidates for cryogenic test masses and particularly suitable substrates for coating research. A detailed discussion on models, based on a semi-analytical calculation starting from the heat diffusion equation, for crystalline substrates will be reported. A new study on the changes in thermoelastic loss after coating deposition, with some preliminary results, will be also reported.

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Mode-dependent mechanical losses in disc resonators

Cited by 28 publications

References 17 publications

Method for the experimental measurement of bulk and shear loss angles in amorphous thin films

Method for the experimental measurement of bulk and shear loss angles in amorphous thin films

Progress in the measurement and reduction of thermal noise in optical coatings for gravitational-wave detectors

The Virgo Coating Collaboration: a detailed study on thermoelasticity in crystalline materials and other research lines

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