Observation and cancellation of a perturbing dc stark shift in strontium optical lattice clocks.

We report on the observation of a dc Stark frequency shift at the 10-(13) level by comparing two strontium optical lattice clocks. This frequency shift arises from the presence of electric charges trapped on dielectric surfaces placed under vacuum close to the atomic sample. We show that these charges can be eliminated by shining UV light on the dielectric surfaces, and characterize the residual dc Stark frequency shift on the clock transition at the 10-(18) level by applying an external electric field.

Coherent optical link through the turbulent atmosphere.

We describe the realization of a 5 km free-space coherent optical link through the turbulent atmosphere between a telescope and a ground target. We present the phase noise of the link, limited mainly by atmospheric turbulence and mechanical vibrations of the telescope and the target. We discuss the implications of our results for applications, with particular emphasis on optical Doppler ranging to satellites and long-distance frequency transfer.

An agile laser with ultra-low frequency noise and high sweep linearity.

We report on a fiber-stabilized agile laser with ultra-low frequency noise. The frequency noise power spectral density is comparable to that of an ultra-stable cavity stabilized laser at Fourier frequencies higher than 30 Hz. When it is chirped at a constant rate of approximately 40 MHz/s, the max non-linearity frequency error is about 50 Hz peak-to-peak over more than 600 MHz tuning range.

Minimizing the Dick effect in an optical lattice clock.

We discuss the minimization of the Dick effect in an optical lattice clock. We show that optimizing the time sequence of operation of the clock can lead to a significant reduction of the clock stability degradation by the frequency noise of the interrogation laser. By using a nondestructive detection of the atoms, we are able to recycle most of the atoms between cycles and consequently to strongly reduce the time spent capturing the atoms in each cycle.

Ultralow-frequency-noise stabilization of a laser by locking to an optical fiber-delay line.

We report the frequency stabilization of an erbium-doped fiber distributed-feedback laser using an all-fiber-based Michelson interferometer of large arm imbalance. The interferometer uses a 1 km SMF-28 optical fiber spool and an acousto-optic modulator allowing heterodyne detection. The frequency-noise power spectral density is reduced by more than 40 dB for Fourier frequencies ranging from 1 Hz to 10 kHz, corresponding to a level well below 1 Hz2/Hz over the entire range; it reaches 10(-2) Hz2/Hz at 1 kHz.

Accuracy evaluation of an optical lattice clock with bosonic atoms.

We report what we believe to be the first accuracy evaluation of an optical lattice clock based on the S01-->P03 transition of an alkaline earth boson, namely, Sr88 atoms. This transition has been enabled by using a static coupling magnetic field. The clock frequency is determined to be 429228066418009(32)Hz.

Accurate optical lattice clock with 87Sr atoms.

We report a frequency measurement of the 1S0-3P0 transition of 87Sr atoms in an optical lattice clock. The frequency is determined to be 429 228 004 229 879(5) Hz with a fractional uncertainty that is comparable to state-of-the-art optical clocks with neutral atoms in free fall. The two previous measurements of this transition were found to disagree by about 2 x 10(-13), i.

Hyperpolarizability effects in a Sr optical lattice clock.

We report the observation of a higher-order frequency shift due to the trapping field in a (87)Sr optical lattice clock. We show that, at the magic wavelength of the lattice, where the first-order term cancels, the higher-order shift will not constitute a limitation to the fractional accuracy of the clock at a level of 10(-18). This result is achieved by operating the clock at very high trapping intensity up to 400 kW/cm(2) and by a specific study of the effect of the two two-photon transitions near the magic wavelength.