• Optical atomic clocks, N. Poli et al., arXiv:1401.2378v2 (2014)
• Optical atomic clocks, A.D. Ludlow et al., Reviews of modern physics 87 (2015)
• Fritz Riehle, Frequency Standards, WILEY-VCH Verlag GmbH & Co. KGaA, 2004

• Best Clock so far (Stand 11/2016) http://www.nature.com/nature/journal/v506/n7486/pdf/nature12941.pdf doi:10.1038/nature12941
• Systematic Evaluation for this http://www.nature.com/articles/ncomms7896.pdf
• Best Clock Comparison so far (Stand 11/2016) Comparison of Two Independent Sr Optical Clocks with 1×10−17 Stability at 10^3  s: physrevlett.109.230801.pdf

• Realization of a timescale with an accurate optical lattice clock: optica-3-6-563.pdf

Summary of the best cavities

• Making optical atomic clocks more stable with 10−16-level laser stabilization, V. Jiang et al.,Nature Photonics 5, 158–161 (2011)

• Vibration:
  • Simple vibration-insensitive cavity for laser stabilization at the 10^-16 level, J. Keller et al., Appl. Phys. B 116, 203–210 (2014)
• Thermal-Noise:
  • Thermal-Noise Limit in the Frequency Stabilization of Lasers with Rigid Cavities, K. Numata et al., PRL 93, 250602 (2004)
  • Thermal noise in optical cavities revisited, T. Kessler et al., J. Opt. Soc. Am. B Vol. 29, No. 1 (2012)
• Residual amplitude modulation:
  • Reduction of residual amplitude modulation to 1 × 10-6 for frequency modulation and laser stabilization, W. Zhang et al., Optics Letters Vol. 39, No. 7 (2014)
  • Investigation and cancellation of residual amplitude modulation in fiber electro-optic modulator based frequency modulation gas sensing technique, Z. Li et al., Sensors and Actuators B 196, 23–30 (2014)
  • Residual amplitude modulation in interferometric gravitational wave detector, K. Kokeyama et al., J. Opt. Soc. Am. A Vol. 31, No. 1 (2014)
    • Residual Amplitude Modulation in Interferometric Gravitational Wave Detectors, K. Kokeyama et al., aXiv:1309.4522v1 [gr-qc] 18 Sep 2013

• 7 cm:
  • Compact, thermal-noise-limited optical cavity for diode laser stabilization at 1×10−15, A. D. Ludlow et al., Optics Letters Vol. 32, Issue 6, pp. 641-643 (2007)

• 10 cm:
  • A compact, robust, and transportable ultra-stable laser with a fractional frequency instability of 1 × 10−15, Q. F. Chen et al., REVIEW OF SCIENTIFIC INSTRUMENTS 85, 113107 (2014)

• 48 cm:
  • 8  ×  10−17 fractional laser frequency instability with a long room-temperature cavity, S. Häfner et al., Optical Letters Vol. 40, No. 9 (2015)

• Crystaline coatings:
  • Tenfold reduction of Brownian noise in high-reflectivity optical coatings, Garrett D. Cole et al., Nature Photonics 7, 644–650 (2013)

• Cubic geometry:
  • Force-insensitive optical cavity, S. Webster et al., Optics Letters Vol. 36, Issue 18, pp. 3572-3574 (2011)
    • PTB took the NPL-design and updated it for a better longterm stability (see Häfner PHD-thesis, Chapter 4.2)

• Cryogenic single-crystal optical cavities:
  • Ultrastable laser with average fractional frequency drift rate below 5 × 10−19/s, C. Hagemann et al., Optics Letters Vol. 39, No. 17 (2014)
  • A sub-40-mHz-linewidth laser based on a silicon single-crystal optical cavity, T. Kessler et al., Nature Photonics Vol. 6, 687-692 (2012)

• Transfer of stability:
  • Providing 10−16 Short-Term Stability of a 1.5-μm Laser to Optical Clocks, C. Hagemann et. al., IEEE Transactions on instrumentation and measurement, VOL. 62, NO. 6 (2013)