Silicon-Based Optical Mirror Coatings for Ultrahigh Precision Metrology and Sensing

Steinlechner, J.; Martin, I. W.; Bell, A. S.; Hough, J.; Fletcher, M.; Murray, P. G.; Robie, R.; Rowan, S.; Schnabel, R.

doi:10.1103/physrevlett.120.263602

Cited by 53 publications

(41 citation statements)

References 42 publications

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“…Therefore, in the absence of data for this coating at cryogenic temperatures, we have used the room-temperature value as a likely upper limit on the cryogenic loss. For the material presented in [29], the optimum heat-treatment temperature to minimize the optical absorption was 450 • C. There is evidence of a decrease of the mechanical loss of a-Si for slightly higher heat-treatment temperatures than 400 • C [30,49]. Therefore, an upper limit of 0.17 × 10 −4 for the loss is still valid.…”

Section: -7mentioning

confidence: 95%

“…The requirement that the optical absorption is <5 ppm makes development of suitable materials even more challenging. Materials with low mechanical loss such as a-Si [29,30] and silicon nitride (SiN) [30,31] are promising, but show too high optical absorption. Different options for doping low-absorbing Ta 2 O 5 are also under investigation [32,33], but so far could not match the thermal-noise requirements.…”

Section: Coating Thermal Noise In the Einstein Telescopementioning

confidence: 99%

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Thermal noise from icy mirrors in gravitational wave detectors

Steinlechner

Martin

2019

Phys. Rev. Research

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The detection of gravitational waves has established a new and very exciting field of astronomy in the past few years. To increase the number of detections and allow observation of a wider range of sources, several future gravitational wave detectors will operate at cryogenic temperatures. Recent investigations of a mirror in one of the cryostats of the Japanese KAGRA detector showed a decrease in reflectivity due to ice growth, induced by residual water molecules moving from the warm to the cold sections of the detector's vacuum system. Based on the optical measurements made in KAGRA, in this paper we calculate the implications of an ice layer on coating thermal noise for the planned European Einstein Telescope. We find coating thermal noise to oscillate, due to periodic reflectivity changes as the ice layer grows. The average coating thermal noise increases significantly over a time of one year with a larger increase at higher temperatures.

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Section: -7mentioning

confidence: 95%

Section: Coating Thermal Noise In the Einstein Telescopementioning

confidence: 99%

Thermal noise from icy mirrors in gravitational wave detectors

Steinlechner

Martin

2019

Phys. Rev. Research

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“…Recent results [35][36][37] have shown that coatings of amorphous silicon (aSi) deposited through various techniques (e-beam evaporation, reactive low-voltage ion plating, IBS) can feature very high refractive index (n ∼ 3.6) and very low internal friction (10 −5 < φ c < 10 −4 ); however, their optical absorption (10 −5 < k < 10 −4 , for 1064 < λ < 2000 nm and 20 < T < 290 K) is still larger than the requirements of GW interferometers. [31] and latest coating samples annealed in air at 900 • C for 10 hours, compared to current values of Ta 2 O 5 -TiO 2 coatings annealed in air at 500 • C for 10 hours (from Fig.…”

Section: Amorphous Siliconmentioning

confidence: 99%

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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“…For a semiconductor material such as silicon nitride and amorphous silicon, however, the optical absorption at cryogenic temperature is expected to be lower than that at room temperature owing to the reduced interband transition at low temperature. Experimental evidence showed that the absorption coefficient of an amorphous silicon film, which is also a potential high-refractive-index material for the mirror coatings of the next-generation laser interferometer gravitational wave detector, at cryogenic temperature was ≈ 3 times lower than that at room temperature [36]. The thermalrefractive effect, dn/dT, is positive for most of the optical materials.…”

Section: A Structures For the Qw Multilayer High Reflectorsmentioning

confidence: 99%

Silicon nitride and silica quarter-wave stacks for low-thermal-noise mirror coatings

et al. 2018

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This study investigated a multi-layer high reflector with new coating materials for nextgeneration laser interferometer gravitational wave detectors operated at cryogenic temperatures. We used the plasma-enhanced chemical vapor deposition method to deposit amorphous silicon nitride/silica quarter-wave high-reflector stacks and studied the properties pertinent to the coating thermal noise. Room-and cryogenic-temperature mechanical loss angles of the silicon nitride/silica quarter-wave bilayers were measured using the cantilever ring-down method. We showed, for the first time, that the bulk and shear loss angles of the coatings can be obtained from the cantilever ring-down measurement, and used the bulk and shear losses to calculate the coating thermal noise of silicon nitride/silica high-reflector coatings. The mechanical loss angle of the silicon nitride/silica bilayer is dispersive with a linear weakly positive frequency dependence, and hence, the coating thermal noise of the high reflectors showed a weakly positive frequency dependence in addition to the normal 1 / f dependence. The coating thermal noise of the silicon nitride/silica high-reflector stack is compared to the lower limit of the coating thermal noise of the end test mirrors of ET-LF, KAGRA, LIGO Voyager, and the directly measured coating thermal noise of the current coatings of Advanced LIGO. The optical absorption of the silicon nitride/silica high reflector at 1550 nm is 45.9 ppm. Using a multimaterial system composed of seven pairs of ion-beam-sputter deposited

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Silicon-Based Optical Mirror Coatings for Ultrahigh Precision Metrology and Sensing

Cited by 53 publications

References 42 publications

Thermal noise from icy mirrors in gravitational wave detectors

Thermal noise from icy mirrors in gravitational wave detectors

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

Silicon nitride and silica quarter-wave stacks for low-thermal-noise mirror coatings

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