ABSTRACT
A new in situ high temperature electrical calibration system was developed at Laboratoire National de Metrologie et d'Essais, Laboratoire Commun de Metrologie and integrated into a heat flux Calvet calorimeter in order to perform accurate and reliable measurements of enthalpy of fusion that are directly traceable to the International System of Units (SI). This system has been designed to enable the calibration of the calorimeter by electrical substitution (Joule effect) as well as the measurement of enthalpy of fusion in perfectly identical experimental conditions. The metrological features (repeatability, linearity, etc.) of the calorimeter have been evaluated with this system by investigating the influence of some parameters (level of energy, dissipation time, and temperature) on the determination of the sensitivity factor of its thermopiles. Two different procedures, for the calibration and the enthalpy measurements with this new electrical calibration system, have been implemented and tested by measuring the enthalpy of fusion of high purity 6N tin. The results obtained are in very good agreement with those measured by other National Metrology Institutes on the same material.
ABSTRACT
The paper reports a new experiment to determine the value of the Boltzmann constant, k(B)=1.3806477(17)×10(-23) J K(-1), with a relative standard uncertainty of 1.2 parts in 10(6). k(B) 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 k(B) is consistent with the 2006 Committee on Data for Science and Technology (CODATA) value: (k(B)(new)/k(B_CODATA)-1)=-1.96×10(-6), where the relative uncertainties are u(r)(k(B)(new))=1.2×10(-6) and u(r)(k(B_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.
ABSTRACT
We demonstrate an original solution to obtain a single-frequency ring laser coupled to an external passive nonresonant ring cavity, which plays the role of an optical diode. This system provides more output power than systems with an intracavity unidirectional device. To the best of our knowledge, this work marks the first demonstration of a unidirectional planar ring laser at 1.3 microm. Using 12 W at 797 nm to pump a Nd:YLF laser, combined with intracavity second-harmonic generation, we achieve yields of 440 mW at 661.3 nm and 340 mW at 656.0 nm.
ABSTRACT
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.
ABSTRACT
We describe single-frequency operation of a diode-pumped Nd:YLF laser in the range 1311.9-1317.2 nm. It can be used for the interrogation of the clock transition in calcium (1314.0 nm) or spectroscopy in hydrogen and metastable singly ionized helium (1312.6 nm). By using a twisted-mode cavity, we have obtained output powers of 830 and 970 mW at 1312.6 and 1314.0 nm, respectively, in a single longitudinal mode.
