Marc Himbert

Efficient cw operation of diode-pumped Nd:YLF lasers at 1312.0 and 1322.6 nm for a silver atom optical clock

Abstract We describe the efficient cw operation of two Nd:YLF lasers at 1312.0 and 1322.6 nm for the development of a silver atom optical clock. For a simple linear cavity laser configuration investigated at these wavelengths, we have obtained an output power of 3.6 W at 1312.0 nm for 13.8 W of absorbed pump power ( λ =806 nm) and 4.8 W output at 1322.6 nm with 16.3 W pump. At 1312.0 nm, using a twisted-mode cavity, a single-frequency output power of 750 mW has been obtained. Single-frequency operation (450 mW) at 1322.6 nm was achieved using an intra-cavity solid etalon.

Determination of the Boltzmann constant using a quasi-spherical acoustic resonator.

The paper reports a new experiment to determine the value of the Boltzmann constant, , with a relative standard uncertainty of 1.2 parts in 106. kB was deduced from measurements of the velocity of sound in argon, inside a closed quasi-spherical cavity at a temperature of the triple point of water. The shape of the cavity was achieved using an extremely accurate diamond turning process. The traceability of temperature measurements was ensured at the highest level of accuracy. The volume of the resonator was calculated from measurements of the resonance frequencies of microwave modes. The molar mass of the gas was determined by chemical and isotopic composition measurements with a mass spectrometer. Within combined uncertainties, our new value of kB is consistent with the 2006 Committee on Data for Science and Technology (CODATA) value: (knewB/kB_CODATA−1)=−1.96×10−6, where the relative uncertainties are and ur(kB_CODATA)=1.7×10−6. The new relative uncertainty approaches the target value of 1×10−6 set by the Consultative Committee on Thermometry as a precondition for redefining the unit of the thermodynamic temperature, the kelvin.

Transportable distance measurement system based on superheterodyne interferometry using two phase-locked frequency-doubled Nd:YAG lasers.

We describe a transportable distance measurement system based on synthetic wavelength interferometry. Two frequency-doubled Nd:yttrium aluminum garnet lasers at 532 nm are used to generate a synthetic wavelength of approximately 2.5 cm. A nonpolarizing interferometric system has been set up to eliminate polarization cross-talk issue. A superheterodyne detection was performed to measure the synthetic phase and to determine absolute distances. The capability to achieve fringe interpolation of 2pi/5600 has been demonstrated and an agreement in distance measurement at the 4 microm level has been achieved, compared to an optical interferometric 3 m long displacement bench.

Capacitive Sensor for Measuring the Filled of Post-Tensioned Ducts. Experimental Setup, Modeling and Signal Processing

This paper presents a newly developed system for bridges post-tensioned devices inspection. These devices are generally composed of cables placed inside a duct, the residual space being filled with a particular cement to avoid corrosion. The nondestructive experimental setup uses a capacitive sensor that gives some relevant information about the electrical properties of the materials located inside the duct. Then, using an original modeling of the interactions between the sensor and the post-tensioned device, a signal processing extracts useful information from the sensors data, like the thickness of an eventual air gap between the cement and the duct. Experimental and theoretical derivations and comparisons are presented in the different parts of this paper.

Transportable Distance Measurement System for Long-Range Applications

This paper describes a transportable distance measurement system based on synthetic wavelength interferometry using two frequency-doubled Nd:YAG lasers. A non-polarizing system has been setup to eliminate polarization cross-talk issue. A partly software-implemented superheterodyne detection was performed to measure the synthetic phase. A fringe interpolation of 2π/5600 is demonstrated and an accuracy of ∼4 µm is achieved over 3 m.

Two-wavelength, passive self-injection-controlled operation of diode-pumped cw Yb-doped crystal lasers

We demonstrate and investigate a peculiar mode of cw Yb3+-doped crystal laser operation when two emissions, at two independently tunable wavelengths, are simultaneously produced. Both emissions are generated from a single pumped volume and take place in either a single beam or spatially separated beams. The laser employs original two-channel cavities that use a passive self-injection-locking (PSIL) control to reduce intracavity loss. The advantages of the application of the PSIL technique and some limitations are shown. The conditions for two-wavelength multimode operation of the cw quasi-three-level diode-pumped Yb3+ lasers and the peculiarity of such an operation are carried out both theoretically and experimentally. The results reported are based on the example of a Yb3+:GGG laser but similar results are also obtained with a Yb3+:YAG laser. The laser operates in the 1023-1033-nm (1030-1040-nm) range with a total output power of 0.4 W. A two-wavelength, single longitudinal mode generation is also obtained.

Development of a quasi-adiabatic calorimeter for the determination of the water vapor pressure curve

Progress in the knowledge of the water saturation curve is required to improve the accuracy of the calibrations in humidity. In order to achieve this objective, the LNE-CETIAT and the LNE-CNAM have jointly built a facility dedicated to the measurement of the saturation vapor pressure and temperature of pure water. The principle is based on a static measurement of the pressure and the temperature of pure water in a closed, temperature-controlled thermostat, conceived like a quasi-adiabatic calorimeter. A copper cell containing pure water is placed inside a temperature-controlled copper shield, which is mounted in a vacuum-tight stainless steel vessel immersed in a thermostated bath. The temperature of the cell is measured with capsule-type standard platinum resistance thermometers, calibrated with uncertainties below the millikelvin. The vapor pressure is measured by calibrated pressure sensors connected to the cell through a pressure tube whose temperature is monitored at several points. The pressure gauges are installed in a thermostatic apparatus ensuring high stability of the pressure measurement and avoiding any condensation in the tubes. Thanks to the employment of several technical solutions, the thermal contribution to the overall uncertainty budget is reduced, and the remaining major part is mainly due to pressure measurements. This paper presents a full description of this facility and the preliminary results obtained for its characterization.

CAPACITIVE PROBE FOR NON DESTRUCTIVE INSPECTION OF EXTERNAL POST‐TENSIONED DUCTS: MODELLING BY DPSM TECHNIQUE

This paper presents both theoretical and experimental aspects of a measurement problem in the field of non‐destructive evaluation. The purpose of our work is to develop a capacitive probe devoted to post‐tensioned cable inspection, mainly for bridge monitoring applications. In this paper will successively be presented the industrial problem, the current probe in use, and an original modeling achieved for sensor design and signal processing. In a first step, we will compare the experimental and theoretical data obtained with different ’devices under test’ configurations. Then we will discuss about both capabilities of our direct model, on one hand to provide some help in sensor design improvements and on other hand to be inserted in an inverse problem scheme, to get an estimate of some interesting data of our problem from the measured signals.

New refractometer: toward an air wavelength reference

A new system, constituted of a double channel Fabry Perot etalon and laser diodes, is described and proposed to be used for air refractive index measurements. The principle of this refractometer is based only on frequencies measurements. It permits instantaneous measurements with a relative standard deviation in the range of 10-9. Some preliminary results on the stability of this systems are presented.

Improved apparatus to determine the Boltzmann constant using a large quasi-spherical acoustic resonator

There is currently great interest in a new definition of the SI unit of temperature based on a fixed value of the Boltzmann constant k. This paper describes work towards an improved determination of k from the measurement of the speed of sound in argon in a quasi-spherical resonator at constant temperature near 273.16 K. The speed is extracted from acoustic resonance frequencies extrapolated to ideal gas behavior while the dimensions of the resonator are determined from microwave resonance frequencies. We outline key aspects of the experiment namely thermometry and pressure measurement, acoustic and microwave resonances and gas handling.