arXiv subjects

Michel Vedel

Publications and source records attributed to Michel Vedel.

4 recordsLinked to original sources

arXiv2005

Comment on "Prospect of optical frequency standard based on a 43Ca+ ion"

A recent evaluation of the frequency uncertainty expected for an optical frequency standard based on a single trapped $^{43}$Ca$^+$ ion was published in Phys. Rev. A {\bf 72} (2005) 043404. The paper contains some interesting information like systematic frequency shifts but fails to depict their uncertainty, leading to confuse accuracy and precision. The conclusions about the major contribution to the frequency shift are not consistent with the presented calculations and omit comparisons with data published previously.

physics.atom-ph↗

arXiv2005

Long-term stabilization of the length of an optical reference cavity

To obtain a high degree of long-term length stabilisation of an optical reference cavity, its free-spectral range is locked by means of an accurate and stable frequency synthesizer. The locking scheme is twofold: a laser is locked on the N$^{th}$ mode of a reference Fabry-Perot cavity and part of the laser light is shifted in frequency to be in resonance with the (N+1)$^{th}$ mode of the cavity. This shift is generated by an acousto-optical modulator (AOM) mounted in a double-pass scheme, matching half of the free spectral range of the reference cavity. The resulting absolute stabilization of the length of the cavity reaches the 10$^{-11}$ level per second, limited by the lock transfer properties and the frequency stability of the AOM control synthesizer.

physics.atom-ph↗

arXiv2004

Evaluation of the ultimate performances of a Ca+ single-ion frequency standard

We numerically evaluate the expected performances of an optical frequency standard at 729 nm based on a single calcium ion. The frequency stability is studied through the Allan deviation and its dependence on the excitation method (single Rabi pulse or two Ramsey pulses schemes) and the laser linewidth are discussed. The minimum Allan deviation that can be expected is estimated to $σ_y(τ) \approx 2.5\times 10^{-15}/\sqrtτ$ with $τ$ the integration time. The frequency shifts induced by the environmental conditions are evaluated to minimize the uncertainty of the proposed standard by chosing the most suited environment for the ion. If using the odd isotope $^{43}$Ca$^{+}$ and a vessel cooled to 77 K, the expected relative shift is $-2 \times 10^{-16}$ with an uncertainty of $\pm 4\times10^{-16}$, mainly due to the quadrupole shift induced by the unknown static electric field gradient .

physics.atom-ph↗

arXiv2004

Metastable level lifetimes from electron-shelving measurements with ion clouds and single ions

The lifetime of the 3d^2D_5/2-level in singly-ionized calcium has been measured by the electron-shelving technique on different samples of rf trapped ions. The metastable state has been directly populated by exciting the dipole-forbidden 4S_1/2 - 3D_5/2 transition. In ion clouds, the natural lifetime of this metastable level has been measured to be (1095+-27) ms. For the single-ion case, we determined a lifetime of (1152+-20) ms. The 1sigma-error bars at the 2%-level have different origins for the two kinds of experiments: data fitting methods for lifetime measurements in an ion cloud and control of experimental parameters for a single ion. De-shelving effects are extensively discussed. The influence of differing approaches for the processing of the single-ion quantum jump data on the lifetime values is shown. Comparison with recent measurements shows excellent agreement when evaluated from a given method.

physics.atom-ph↗