Crystalline Mirror Solutions


Ultralow Brownian noise
High Finesse > 200,000

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    Center wavelength

    900 nm

    2000 nm

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    Optical absorption

    < 1 ppm

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    Optical scatter

    < 5 ppm

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    Radius of curvature

    > 10 cm



Typically >99.99%, >99.999% achievable
Loss angle
<4 × 10⁻⁵ at 300 K, <5 × 10⁻⁶ at 10 K
Temperature range
Cryogenic, room temperature, and high temperature solutions available
Coating material
Single-crystal GaAs/AlGaAs
Coating surface quality
1 Å RMS micro-roughness
Substrate material
Typically fused silica, other materials available
Substrate diameter
0.5 - 1 inch (12.7 - 25.4 mm), other sizes available
Surface flatness
<0.10 wave P-V measured @ 633 nm
Similar to fused silica, cleaning instructions provided on request
Copyright: Courtesy of the Ye group and Brad Baxley/JILA

Precise Atomic Clocks

Low-temperature optical reference cavities using crystalline mirror technology are currently being tested and represent a new world-record in frequency stability. The expected stability surpasses the previously unattainable level of Δf/f below 10¹⁷ in one of second integration time and will establish a new milestone in the performance of optical atomic clocks.

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Optical Reference Cavities

Crystalline mirror technology allows for a significant reduction in the size of optical reference cavities, while simultaneously maintaining excellent noise performance. As a consequence, compact, space-based optical reference cavities are currently being developed. This serves as a primer for future space-based navigation systems using optical reference standards.


Gravitational Wave Detection

Crystalline coatings allow, for the first time, for the operation of laser-based interferometric gravitational wave detectors at the ultimate (standard) quantum limit. This goes hand-in-hand with a significant increase in the volume of observed space in a gravitational wave observatory. At this stage, large area-diameter crystalline coatings are being employed both at the German 10 meter prototype detector and the Australian 80 meter prototype detector, and further noise tests are underway at LIGO.

Relevant publications

  • Technology for the next gravitational wave detectors

    Mitrofanov Valery P., Chao Shiuh, Pan Huang-Wei, Kuo Ling-Chi, Cole Garrett, Degallaix Jerome & Willke Benno

    Science China, Physics, Mechanics & Astronomy, vol. 58, no. 12: 120404, December 2015.

  • Mapping the optical absorption of a substrate-transferred crystalline AlGaAs coating at 1.5 µm

    J. Steinlechner, I. W. Martin, A. Bell, G. D. Cole, J. Hough, S. Penn, S. Rowan, S. Steinlechner

    Classical and Quantum Gravity, vol. 32, no. 10, 105008, 21 May 2015.

  • Sensing Earth rotation with a helium-neon ring laser operating at 1.15 µm

    K. U. Schreiber, R. J. Thirkettle, R. B. Hurst, D. Follman, G. D. Cole, M. Aspelmeyer, J.-P. R. Wells

    “Sensing Earth rotation with a helium-neon ring laser operating at 1.15 µm,” Optics Letters, vol. 40, no. 8, pp. 1705-1708, 15 April 2015.

  • Tenfold reduction of Brownian noise in high-reflectivity optical coatings

    G. D. Cole, W. Zhang, M. J. Martin, J. Ye, M. Aspelmeyer

    “Tenfold reduction of Brownian noise in high-reflectivity optical coatings,” Nature Photonics, vol. 7, no. 8, pp. 644-650, August 2013.

  • Cavity optomechanics with low-noise crystalline mirrors

    G. D. Cole

    SPIE Optics & Photonics, Optical Trapping and Optical Micromanipulation IX, San Diego, CA, USA, 8458-07, 12–16 August 2012.

  • Phonon tunneling dissipation in mechanical resonators

    G. D. Cole, I. Wilson-Rae, K. Werbach, M. R. Vanner, M. Aspelmeyer

    Phonon tunneling dissipation in mechanical resonators,” Nature Communications, vol. 2, article 231, 8 March 2011.