C. Mandache

Ultrastable lasers based on vibration insensitive cavities

We present two ultrastable lasers based on two vibration insensitive cavity designs, one with vertical optical axis geometry, the other horizontal. Ultrastable cavities are constructed with fused silica mirror substrates, shown to decrease the thermal noise limit, in order to improve the frequency stability over previous designs. Vibration sensitivity components measured are equal to or better than

Doppler-free spectroscopy of the 1S0-3P0 optical clock transition in laser-cooled fermionic isotopes of neutral mercury.

1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}/\text{m}\text{ }{\text{s}}^{\ensuremath{-}2}

Cavity frequency pulling in cold atom fountains

for each spatial direction, which shows significant improvement over previous studies. We have tested the very low dependence on the position of the cavity support points, in order to establish that our designs eliminate the need for fine tuning to achieve extremely low vibration sensitivity. Relative frequency measurements show that at least one of the stabilized lasers has a stability better than

Laser locking to the 199 Hg 1 S 0 − 3 P 0 clock transition with 5.4 × 10 −15 /✓τ fractional frequency instability

5.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}

Laser locking to the 199Hg clock transition with 5.4x10^(-15)/sqrt(tau) fractional frequency instability

at 1 s, which is the best result obtained for this length of cavity.

Magneto-optical trap of neutral mercury for an optical lattice clock

We report direct laser spectroscopy of the 1S0-3P0 transition at 265.6 nm in fermionic isotopes of neutral mercury in a magneto-optical trap. Measurements of the frequency against the LNE-SYRTE primary reference using an optical frequency comb yield 1 128 575 290 808.4+/-5.6 kHz in 199Hg and 1 128 569 561 139.6+/-5.3 kHz in 201Hg. The uncertainty, allowed by the observation of the Doppler-free recoil doublet, is 4 orders of magnitude lower than previous indirect determinations. Mercury is a promising candidate for future optical lattice clocks due to its low sensitivity to blackbody radiation.

Ultra-stable optical cavities: Design and experiments at LNE-SYRTE

We present an analytical model and a numerical calculation of the cavity frequency pulling effect in cold atom fountains. We report the first measurement of this effect in a /sup 87/Rb fountain. We find a quantitative agreement with theory.

Towards an Optical Lattice Clock Based on Neutral Mercury

With 199Hg atoms confined in an optical lattice trap in the Lamb-Dicke regime, we obtain a spectral line at 265.6 nm for which the FWHM is ~15 Hz. Here we lock an ultrastable laser to this ultranarrow 1S0-3P0 clock transition and achieve a fractional frequency instability of 5.4×10(-15)/✓τ for τ ≤ 400 s. The highly stable laser light used for the atom probing is derived from a 1062.6 nm fiber laser locked to an ultrastable optical cavity that exhibits a mean drift rate of -6.0×10(-17) s(-1) (-16.9 mHz s(-1) at 282 THz) over a six month period. A comparison between two such lasers locked to independent optical cavities shows a flicker noise limited fractional frequency instability of 4×10(-16) per cavity.

Toward a mercury optical lattice clock: Spectroscopy of the clock transition in fermionic isotopes

With 199Hg atoms confined in an optical lattice trap in the Lamb-Dicke regime, we obtain a spectral line at 265.6 nm for which the FWHM is ~15 Hz. Here we lock an ultrastable laser to this ultranarrow 1S0-3P0 clock transition and achieve a fractional frequency instability of 5.4×10(-15)/✓τ for τ ≤ 400 s. The highly stable laser light used for the atom probing is derived from a 1062.6 nm fiber laser locked to an ultrastable optical cavity that exhibits a mean drift rate of -6.0×10(-17) s(-1) (-16.9 mHz s(-1) at 282 THz) over a six month period. A comparison between two such lasers locked to independent optical cavities shows a flicker noise limited fractional frequency instability of 4×10(-16) per cavity.

Measurement of the 87Rb ground-state hyperfine splitting in an atomic fountain

We report the cooling and trapping of neutral mercury in a vacuum chamber using the ¹S₀ - ³P₁ intercombination transition. We produce an atom cloud of a few million atoms with a trap loading time of 1.6 seconds. The atoms are prepared for the interrogation of the forbidden ¹S₀ - ³P₀ intercombination transition, using an ultra-stable UV source referenced to a vertically mounted Fabry-Perot cavity.