Aide in decision-making: contribution to uncertainties in three-dimensional measurement

The authorities of the standards organization International Organization of Standardization (ISO) advocate mastering any uncertainties in all parts of the industrialization process. In the three-dimensional (3D) measurement process, uncertainty is usually obtained at the end of a battery of tests. It is defined as a whole because it includes several types of errors, known systematic components, unknown systematic components and random components. Automated calculations of uncertainty can be made based on statistics. This method is based on statistical concepts, which are in accordance with “The Guide to the expression of the uncertainty in measurement” (GUM). It also enables us to generate uncertainties on the verification of ISO specifications (or specs in the ISO directives). In the course of this article, a usage will be presented that takes the knowledge of uncertainties into account: this usage will help the operator to take a decision on the conformance of a mechanical part in reference to its conformance to geometric tolerance.     

Efficiency and mode discrimination of a linear array of square CO2 waveguide lasers phase-coupled by an intracavity spatialfilter

In this paper, we present a theoretical analysis of a linear array of square waveguide CO₂ lasers phase-coupled with an intracavity spatial filter. Using a Rigrod-like method, we calculate the efficiency of the device and analyze its capability to discriminate between the fundamental mode and the transverse modes of both the array and the individual square waveguide     

Thickness optimization of the composite gain medium for the oscillator and amplifier of the lucia laser

Using a theory of quasi-three-level laser ions, we obtained the optimum thickness of the gain medium of Yb:YAG. For the parameters of the oscillator and the amplifier of the diode-pumped Lucia laser (Lasers Ultra-Courts et Intense et Applications), which will deliver a 100 J, 10 Hz, 10 ns pulse train the optimum thicknesses are, respectively, 1.4 and 1.6 mm, with a concentration of 10 at. %. Simulations indicate that the bending of such a thin medium is great but can be eliminated by substitution of a composite gain medium. The optimum thickness of undoped YAG is related to that of Yb:YAG and is also dependent on cooling conditions. Results show that, for a small-aperture oscillator, we can obtain both minimum bending and optical distortion at several doping concentrations. However, greater doping (approximately 20 at. %) is preferred for a large-aperture amplifier. The results reported will be helpful for the design of gain media for high-average-power thin disk Yb:YAG lasers.     

Effect of diode wavelength broadening in a diode end-pumped solid-state amplifier

The effect of the spectral broadening in cw diode pumping and the wavelength shift in pulsed pumping of a solid-state laser is investigated theoretically. A very simple model allowing the computation of the reduction of the absorbed pump energy is developed. The results are applied to an ytterbium-doped solid-state laser and should be fruitful for amplifier and laser design.     

Theoretical study of cw to short pulse conversion in an active cw-injected ring cavity with a Yb3+:YAG amplifier

The short laser pulse generated from an active cw-injected ring cavity with Yb3+:YAG crystal, which is treated as the homogeneously broadened amplifier, is studied theoretically. Based on the derived results, the impacts of the amplifier length, the seeding laser intensity and frequency, the pump intensity, the efficiency of the acousto-optic modulator (AOM), and the frequency shift generated by the AOM on the performance of the laser pulse are analyzed.     

Homogenizer and multipass pump beam combination for quasi-longitudinally diode-pumped solid-state lasers

We present a new apparatus making possible both homogeneity and multipass pumping. It is made up of a square section kaleidoscope made of transparent medium on the terminal faces of which are set mirrors with transparent holes at the centers. The kaleidoscope homogenizes the beam. The pump power reflected by the amplifier medium returns in the kaleidoscope, and the mirrors reflect this pump light toward the amplifier medium.     

Quality follow-up of CMM via the measurement of microdefects

The use of CMM in industrial environments requires a surveillance of their state of quality. The implementation of the procedure which allows to ensure the quality of the measurement is often left to the user’s initiative, which is powerless in the face of the complexity of the problem. We are interested in a new type of deviation that we call microdefects. We propose indicators which characterize the microdefects. These indicators are intended to point out metrological failure of CMM axes. We propose indicators that will assess the procedure adapted to a use of CMM in an industrial environment within an integrated CMM global survey system. After an introduction of the microdefects we are interested in, we describe the quality indicators we have defined and the procedure chosen to evaluate them. We conclude with the perspective for these indicators.     

Generalized formula for continuous-wave end-pumped Yb-doped material amplifier gain and laser output power in various pumping configurations

We present a general formula fitted for computing the amplification and laser output power in a Yb-doped material under various quasi-end-pumping configurations. These configurations include single pass pumping, backreflection pumping in which the pump is reflected by a mirror set on the rear face of the amplifier medium, contrapropagation pumping where two pump beams are launched on both sides of the amplifier and, for every configuration, regenerative pumping in which the transmitted or reflected pump beam is recycled using the proper apparatus. We show that, with regenerative pumping, the efficiency is drastically improved and the optimum amplifier length leading to the maximum laser output power is shorter compared with the one obtained with conventional pumping. In this model, we do not take temperature effect into account.     

Theoretical modeling and design of a Tm, Ho:YLiF4 microchip laser

We present theoretical modeling that makes it possible to compute the output characteristics of a laser-pumped codoped Tm, Ho microchip laser and the experimental results already obtained with a Tm, Ho:YLiF(4) crystal. By taking into account the match of the pump beam to the self-induced eigenmode of the cavity, we find good agreement between theory and experiment when the pump beam size is properly adjusted relative to the absorbed pump power and the crystal characteristics.     

Numerical simulation of a high-average-power diode-pumped ytterbium-doped YAG laser with an unstable cavity and a super-Gaussian mirror

A numerical technique with which to compute the output characteristics of a solid-state laser with an unstable cavity and a super-Gaussian coupling mirror is proposed. This technique is applied to an Yb:YAG actively Q-switched laser. With this formalism, the mode formation for the fundamental mode is analyzed and the performance achievable by such a laser for various cavity parameters is determined. Then the results obtained with such a cavity are compared with those given for a stable cavity with graded phase output mirror that is also used for obtaining super-Gaussian mode.