The frequencies of a cryogenic sapphire oscillator and a hydrogen maser are compared to set new constraints on a possible violation of Lorentz invariance. We give a detailed description of microwave resonators operating in Whispering Gallery modes and then apply it to derive explicit models for Lorentz violating effects in our experiment. Models are… (More)
We present measurements of cavity frequency pulling and collisional frequency shifts in a 87Rb fountain with a frequency resolution of 3x10(-16). Agreement with theory is found for the cavity pulling and the measured collisional shifts. The clock shift is found at least 50 times smaller than in 133Cs.
This paper describes advances in microwave frequency standards using laser-cooled atoms at BNM-SYRTE. First, recent improvements of the 133 Cs and 87 Rb atomic fountains are described. Thanks to the routine use of a cryogenic sapphire oscillator as an ultra-stable local frequency reference, a fountain frequency instability of 1.6 × 10 −14 τ −1/2 where τ is… (More)
We present a new evaluation of an 87 Sr optical lattice clock using spin polarized atoms. The frequency of the 1 S0 → 3 P0 clock transition is found to be 429 228 004 229 873.6 Hz with a fractional accuracy of 2.6 × 10 −15 , a value that is comparable to the frequency difference between the various primary standards throughout the world. This measurement is… (More)
We have developed external-cavity diode lasers, where the wavelength selection is assured by a low loss interference filter instead of the common diffraction grating. The filter allows a linear cavity design reducing the sensitivity of the wavelength and the external cavity feedback against misalignment. By separating the feedback and wavelength selection… (More)
Optical and radio frequency standards located in JILA and National Institute of Standards and Technology (NIST) laboratories have been connected through a 3.45-km optical fiber link. An optical frequency standard based on an iodine-stabilized Nd:YAG laser at 1064 nm (with an instability of ϳ4 ϫ 10 Ϫ14 at 1 s) has been transferred from JILA to NIST and… (More)
The frequencies of a cryogenic sapphire oscillator and a hydrogen maser are compared to set new constraints on a possible violation of Lorentz invariance. We determine the variation of the oscillator frequency as a function of its orientation (Michelson-Morley test) and of its velocity (Kennedy-Thorndike test) with respect to a preferred frame candidate. We… (More)
Testing the stability of fundamental constants with the 199 Hg + single-ion optical clock Over a two-year duration, we have compared the frequency of the 199 Hg + 5d 10 6s 2 S 1/2 (F = 0) ←→ 5d 9 6s 2 2 D 5/2 (F = 2) electric-quadrupole transition at 282 nm with the frequency of the ground-state hyperfine splitting in neutral 133 Cs. These measurements show… (More)