This paper gives the 2010 self-consistent set of values of the basic constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for international use. The 2010 adjustment takes into account the data considered in the 2006 adjustment as well as the data that became available from 1 January 2007, after the closing date of that adjustment, until 31 December 2010, the closing date of the new adjustment. Further, it describes in detail the adjustment of the values of the constants, including the selection of the final set of input data based on the results of least-squares analyses. The 2010 set replaces the previously recommended 2006 CODATA set and may also be found on the World Wide Web at physics.nist.gov/constants.

/pdf/codata-recommended-values-of-the-fundamental-physical-4bsdant71c.pdf

CODATA Recommended Values of the Fundamental Physical Constants: 2006

The series of precisely spaced, sharp spectral lines that form an optical frequency comb is enabling unprecedented measurement capabilities and new applications in a wide range of topics that include precision spectroscopy, atomic clocks, ultracold gases, and molecular fingerprinting. A new optical frequency comb generation principle has emerged that uses parametric frequency conversion in high resonance quality factor (Q) microresonators. This approach provides access to high repetition rates in the range of 10 to 1000 gigahertz through compact, chip-scale integration, permitting an increased number of comb applications, such as in astronomy, microwave photonics, or telecommunications. We review this emerging area and discuss opportunities that it presents for novel technologies as well as for fundamental science.

http://science.sciencemag.org/content/sci/332/6029/555.full.pdf

Microresonator-Based Optical Frequency Combs

Time has always had a special status in physics because of its fundamental role in specifying the regularities of nature and because of the extraordinary precision with which it can be measured. This precision enables tests of fundamental physics and cosmology, as well as practical applications such as satellite navigation. Recently, a regime of operation for atomic clocks based on optical transitions has become possible, promising even higher performance. We report the frequency ratio of two optical atomic clocks with a fractional uncertainty of 5.2 × 10–17. The ratio of aluminum and mercury single-ion optical clock frequencies νAl+/νHg+ is 1.052871833148990438(55), where the uncertainty comprises a statistical measurement uncertainty of 4.3 × 10–17, and systematic uncertainties of 1.9 × 10–17 and 2.3 × 10–17 in the mercury and aluminum frequency standards, respectively. Repeated measurements during the past year yield a preliminary constraint on the temporal variation of the fine-structure constant α of ![Formula][1] .

 [1]: /embed/tex-math-1.gif

/pdf/frequency-ratio-of-al-and-hg-single-ion-optical-clocks-1cfze27xja.pdf

Frequency Ratio of Al+ and Hg+ Single-Ion Optical Clocks; Metrology at the 17th Decimal Place

The development of wave optics for light brought many new insights into our understanding of physics, driven by fundamental experiments like the ones by Young, Fizeau, Michelson-Morley and others. Quantum mechanics, and especially the de Broglie’s postulate relating the momentum p of a particle to the wave vector k of an matter wave: k = 2 λ = p/ℏ, suggested that wave optical experiments should be also possible with massive particles (see table 1), and over the last 40 years electron and neutron interferometers have demonstrated many fundamental aspects of quantum mechanics [1].

/pdf/optics-and-interferometry-with-atoms-and-molecules-1vnuwajb51.pdf

Optics and interferometry with atoms and molecules

Advances in atomic physics, such as cooling and trapping of atoms and molecules and developments in frequency metrology, have added orders of magnitude to the precision of atom-based clocks and sensors. Applications extend beyond atomic physics and this article reviews using these new techniques to address important challenges in physics and to look for variations in the fundamental constants, search for interactions beyond the standard model of particle physics, and test the principles of general relativity.

Search for New Physics with Atoms and Molecules

The most common time-domain measure of frequency stability, the Allan variance, is typically estimated using a frequency counter. Close examination of the operation of modern high-resolution frequency counters shows that they do not make measurements in the way commonly assumed. The consequence is that the results typically reported by many laboratories using these counters are not, in fact, the Allan variance, but a distorted representation. We elucidate the action of these counters by consideration of their operation in the Fourier domain, and demonstrate that the difference between the actual Allan variance and that delivered by these counters can be very significant for some types of oscillators. We also discuss ways to avoid, or account for, a distorted estimation of Allan variance

Considerations on the measurement of the stability of oscillators with frequency counters

The low-noise synthesis of a harmonic comb of microwave frequencies using a 1 GHz femtosecond-laser-based synthesiser that is referenced to a cavity-stabilised laser is demonstrated. The residual phase noise is /spl sim/-110 dBc/Hz at 1 Hz offset from the 10 GHz harmonic. Phase noise is measured with an interferometric measurement system having low sensitivity to AM.

/pdf/low-noise-synthesis-of-microwave-signals-from-an-optical-3jqg31vmpq.pdf

Low-noise synthesis of microwave signals from an optical source

We investigate the comb linewidths of self-referenced, fiber-laser-based frequency combs by measuring the heterodyne beat signal between two independent frequency combs that are phase locked to a common cw optical reference. We demonstrate that the optical comb lines can exhibit instrument-limited, subhertz relative linewidths across the comb spectra from 1200 to 1720 nm with a residual integrated optical phase jitter of ∼1 rad in a 60 mHz to 500 kHz bandwidth. The projected relative pulse timing jitter is ∼1 fs. This performance approaches that of Ti:sapphire frequency combs.

http://nlo.stanford.edu/system/files/swann_ol2006.pdf

Fiber-laser frequency combs with subhertz relative linewidths

The most common time-domain measure of frequency stability, the Allan variance, is typically estimated using a frequency counter. Close examination of the operation of modern high-resolution frequency counters shows that they do not make measurements in the way commonly assumed. The consequence is that the results typically reported by many laboratories using these counters are not, in fact, the Allan variance, but a distorted representation. We elucidate the action of these counters by consideration of their operation in the Fourier domain, and demonstrate that the difference between the actual Allan variance and that delivered by these counters can be very significant for some types of oscillators. We also discuss ways to avoid, or account for, a distorted estimation of Allan variance.

Considerations on the Measurement of the Stability of Oscillators with Frequency Counters

We discuss the origins and the suppression of the large frequency jitter on the carrier-envelope offset frequency (fceo) of fiber-laser frequency combs. While this frequency noise appears most prominently on fceo, its effects are felt across the frequency comb and it is a potential limiting factor in applications of fiber-laser frequency combs. Here we show that its origin lies in the white amplitude noise of the pump laser output. We dramatically reduce this noise by operating the pump laser in a lower-noise state, i.e. at higher pump current, and by more aggressively feeding back to the pump current with an optimal feedback network. We demonstrate instrument-limited fceo linewidths and an integrated fceo phase jitter of 1 rad.

/pdf/suppression-of-pump-induced-frequency-noise-in-fiber-laser-4y4yj7zt3h.pdf

John J. McFerran

Papers

Considerations on the measurement of the stability of oscillators with frequency counters

Low-noise synthesis of microwave signals from an optical source

Fiber-laser frequency combs with subhertz relative linewidths

Considerations on the Measurement of the Stability of Oscillators with Frequency Counters

Suppression of pump-induced frequency noise in fiber-laser frequency combs leading to sub-radian f ceo phase excursions