Academic literature on the topic 'Spectroscopie par absorption laser'

Although the primarily phenomenological theory of absorption and refraction of light by matter, based on classical models as presented in Chapter 4, is very useful, it is incomplete and often inadequate. A more complete and accurate picture of electrodynamics is given by the theory of quantum optics, and that is the topic of this chapter. The models developed in this chapter are more detailed and therefore more complicated than the phenomenological models of Chapter 4. The most robust models, which are applied in Part II, are presented in this chapter. The quantum models accurately represent experimental data and allow extrapolation and interpolation of such data. Many practical computer based models concerning optical propagation are based on this theory. The theory of elastic scatter as presented in Chapter 4 is consistent with quantum optics and is not presented again. (However, inelastic scatter must address the quantum nature of the scattering medium.) Quantum optics is not completely covered in this chapter. Entire textbooks are devoted to this diverse and comprehensive topic covering optics (see Refs. 5.1–5.3). The emphasis of this book is on absorption and reflection spectroscopy. Now details of internal structure of the medium impacting light–matter interaction are examined. The classical oscillator model is upgraded by semiclassical radiation theory and a quantum oscillator model is developed. Semiclassical radiation theory is based on a quantized medium coupled to a classical field. It is often applied to laser theory, where near-line-center stimulated emission dominates. The quantum oscillator model again utilizes the quantized medium and classical field, but with more attention to detailed balance between absorption and emission. It satisfies causality and the fundamental symmetry relationships established in Chapter 2. These quantum optics models are more complete formalisms and provide solutions to the shortcomings of classical electrodynamics. Of particular interest to propagation in gaseous media is the line shape in the far wing. To achieve long path lengths, propagation near line center of a resonance must be avoided. Line shape models in quantum optics accurately represent much of the frequency and temperature dependence observed in experimental data.

In order to study the mechanism of mixed-convection and heat transfer when injecting hot water vapor into the containment, it is necessary to measure temperature distribution inside it. To overcome the shortcomings of traditional thermocouples technique during injection experiments of water vapor, a new temperature measurement method based on tunable diode laser absorption spectroscopy (TDLAS) was proposed in this paper. The TDLAS technique is based on the detection of H2O absorption lines with different energies of low levels, and the spectra can be recorded using a laser detector. The data o

Abstract Laser microchemical etching systems provide enhanced through-wafer IR viewing and provide access for focused ion beam (FIB) tools and e-beam testers on flip-chip packaged die [1]. In demanding applications, laser etching is directed at rates of 100,000 cubic micrometers per second and must be stopped within 10 to 15 micrometers (thickness remaining) of the active flip-chip circuit. In cases where the initial die thickness is known, the laser process is sufficiently reproducible and system depth of focus is sufficiently narrow to place the laseretched floor within an accuracy of about