Ground state hyperfine structures of 43K and 44K measured by atomic beam magnetic resonance coupled with laser optical pumping

The ground state hyperfine structures of 43 K and 44K have been measured by an atomic beam magnetic resonance method in which the atoms are spin-polarized by laser optical pumping. The spectroscopic results are : Δv43( 2S1/2) = 192.648 4 (30) MHz and Δν44( 2S1/2) = - 946.718 (3) MHz. The sensitivity of our method is compared to the one achieved in classical ABMR apparatus

Développement de sources lasers à l'état solide pour la réalisation d'une horloge optique basée sur l'atome d'argent

Cette thèse s inscrit dans le projet du développement d une horloge optique basée sur une transition à deux photons de 661 nm de l atome d Ag. Pour profiter du facteur de qualité de la résonance, els atomes sont refroidis par un laser à 328 nm. Ce mémoire traite de la mise au point de sources lasers solides pour simplifier l expérience actuelle. Le laser de Nd :YLF, pompé par diode laser, permet d accéder aux longueurs d onde 1322 nm et 1312 nm. Avec une et deux étapes de doublage en fréquence, nous obtenons les ondes à 661 et 328 nm. Afin de dimensionner différentes configurations laser, un modèle théorique a été testé. L une d elles a donné des sources continues, monomodes, d environ 2 W dans l infrarouge et, après doublage intracavité, 400 mW dans le rouge. Les probabilités de transition de l atome d argent calculées à l aide des codes de Cowan ont permis de chiffrer l ordre de grandeur de la puissance laser nécessaire et d estimer la durée de vie du niveau métastable.This work deals with the development of a clock based on a two-photon transition in Ag at 661 nm. Laser-cooled atoms require a wavelength at 328 nm. This thesis describes the design and construction of solid-state allowing one to simplify the present apparatus. Diode-pumped Nd:YLF crystals enable one to generate both 1322 and 1312 nm. The second harmonic of the former will provide 661 nm while twice frequency doubling the later will yield 328 nm. We have developed a theoretical model in order to design several prototype configurations (linear, twisted mode and re-injected ring cavities). Using the last of these, we have built single-mode c.w. lasers at both 1312 and 1322 nm with outputs of up to 2 W. By intra-cavity frequency doubling therewith, we have obtained 440 mW at 661 nm and 340 mW at 656 nm. In addition, we have evaluated transition probabilities using the Cowan codes, both to estimate two-photon excitation rates and calculate the lifetime of the metastable.PARIS-CNAM (751032301) / SudocSudocFranceF

High accuracy velocity control method for the french moving-coil watt balance

International audienceWe describe a novel method of velocity control dedicated to the French moving-coil watt balance. In this project, a coil has to move in a magnetic field at a velocity of 2 mm s−1 with a relative uncertainty of 10−9 over 60 mm. Our method is based on the use of both a heterodyne Michelson's interferometer, a two-level translation stage, and a homemade high frequency phase-shifting electronic circuit. To quantify the stability of the velocity, the output of the interferometer is sent into a frequency counter and the Doppler frequency shift is recorded. The Allan standard deviation has been used to calculate the stability and a systd of about 2.2310−9 over 400 s has been obtained

Heterodyne interferometric technique for displacement control at the nanometric scale

International audienceWe propose a method of displacement control that addresses the measurement requirements of the nanotechnology community and provide a traceability to the definition of the me'ter at the nanometric scale. The method is based on the use of both a heterodyne Michelson's interferometer and a homemade high frequency electronic circuit. The system so established allows us to control the displacement of a translation stage with a known step of 4.945 nm. Intrinsic relative uncertainty on the step value is 1.631029. Controls of the period of repetition of these steps with a high-stability quartz oscillator permits to impose an uniform speed to the translation stage with the same accuracy. This property will be used for the watt balance project of the Bureau National de Me'trologie of France

Observation by two-photon laser spectroscopy of the 4d105s 2S1/2→4d95s2 2D5/2 clock transition in atomic silver

We report the observation of the very narrow 4d105s 2S1/2→4d95s2 2D5/2 transition in atomic silver. The frequencies of the hyperfine components in 107Ag and 109Ag have been measured using Doppler-free twophoton laser spectroscopy of a thermal beam and heterodyne calibration with respect to the a1 component of the 62P(4-5) line in molecular iodine near 661 nm. For the center of gravity of a mixture of natural abundance, we deduce the value 906 641 295.77(19) MHz. For the isotope shift, we obtain nu(109Ag)−nu(107Ag) =564.1537 MHz, from which we deduce the frequency and isotope shift of the 4d105s 2S1/2→4d106p 2P3/2 transition at 206 n

Polarimetric interferometer for nanoscale positioning applications

International audienceWe propose and demonstrate a displacement control method at the subnanometric scale based on a Michelson interferometer combined with a polarimeter and a phase-locked loop electronic board. Step by step displacements with a step value of 5 nm are presented. A repeatability of 0.47 nm is obtained from back and forth displacements over 1 m range. We show that a residual ellipticity of less than 10° on the polarization state leads to a positioning error of less than 1 nm. Such system could be used over millimeter range displacements in a controlled surrounding environment leading to numerous applications in nanometrology

A New Optical Wavelength Ratio Measurement Apparatus: The Fringe Counting Sigmameter

International audienceA new, compact and achromatic Michelson-type interferometer with a variable path difference is presented. This "fringe-counting" sigmameter allows measurement of optical wavelength ratios between a laser of unknown wavelength and a reference laser of known wavelength. This apparatus, maintained in a vacuum, measures interference order variations in two stages: integer counting of around 400 000 and fractional counting (also called "excess fraction") with an uncertainty of 10. From these measurements, this "sigmameter" can determine laser wavelength from 0.36 m to 1.5 m with an accuracy of 1.10 using a reference stabilized He-Ne laser

Generation of 656 nm coherent red-light by frequency-doubled Nd:YLiF4/β-BaB2O4 laser for a compact silver atoms optical clock

International audienceWe describe an efficient continuous-wave diode-pumped Nd:YLiF4 laser oscillating on theσ-polarized 4F3/2−4I13/2 transition at λω = 1312 nm. With a simple linear cavity laser, we reached anintracavity power of 310 W at λ = 1312 nm for 16 W of absorbed pump power (λp ∼ 806 nm). A 0.25 Wof tunable radiation (λ2ω = 656−658 nm) was obtained by intracavity second-harmonic generation (SHG)with a 5×5×7 mm3 β-BaB2O4 crystal. Up to 10 mW of tunable single-frequency operation was observedusing a 200 μm thin fused silica intracavity solid etalon. The optimal waist for a maximum conversionefficiency has been calculated theoretically using Boyd and Kleiman model. For the 1312−656 nm SHG,we found a walk-off parameter B = 8.99 and an optimal waist of 25 μm. Comparing to the experimentalmeasurement of the optimal waist, we found a relative discrepancy of 2.84 × 10−2. This laser is dedicatedto the spectroscopic study of silver atoms trapped in a buffer-gas-free paraffin coated Pyrex cell that willbe used in a compact atomic optical clock