For the example of the D 1 line of 87 Rb we analyze the experimental parameters that control the transient response of electromagnetically induced transparency. Quantum coherent free-induction decay is observed on time scales exceeding several milliseconds in a buffer-gas vapor cell. Numerical solutions of the quantum master equation and approximate analytical solutions are tested and absolute comparisons of the transient time scales, power broadening, resonance contrast, and frequency shifts are made. Two actively-phase-locked lasers are employed. The effects of laser phase noise that is not fully correlated are studied.
A near-resonant rf field pumping the hyperfine transition between the two ground states of a -shaped dark resonance leads to a resonance tripling, each component displaying electromagnetically induced transparency (EIT). We investigate the three resonances under high spectral and temporal resolution. The triplet formation is analogous to that of the Mollow triplet but distinct in that the role played by the spontaneous emission rate is now taken by the one-photon scattering rate of the optical Raman transition. Complex phase relations exist between the three em fields under EIT conditions. We explain our observations using numerical solutions of the quantum master equation as well as a simple analytical dressed-state model.
In this study, a method is presented to measure precisely the thickness of coated components based on laser-induced breakdown spectroscopy (LIBS). The thickness is determined by repetitively ablating the coating with ultrashort laser pulses, monitoring the spectrum of the generated plasma and calculating the coating thickness from the specific plasma signal in comparison to a reference measurement. We compare different pulse durations of the laser (290 fs, 10 ps, 6 ns) to extend the material analysis capabilities of LIBS to a real thickness measurement tool. The method is designed for production processes with known coating materials. Here, we show this for a nickel coating and a tungsten carbide coating on a copper sample with thicknesses from 5–30 µm.
We study the capability of nanosecond laser-induced breakdown spectroscopy (ns-LIBS) for depth-resolved concentration measurements of Li-Ion battery cathodes. With our system, which is optimized for quality control applications in the production line, we pursue the goal to unveil manufacturing faults and irregularities during the production process of cathodes as early as possible. Femtosecond laser-induced breakdown spectroscopy (fs-LIBS) is widely considered to be better suited for depth-resolved element analysis. Nevertheless, the small size and intensity of the plasma plume, non-thermal energy distribution in the plasma and high investment costs of fs-LIBS make ns-LIBS more attractive for inline application in the industrial surrounding. The system, presented here for the first time, is able to record quasi-depth-resolved relative concentration profiles for carbon, nickel, manganese, cobalt, lithium and aluminum which are the typical elements used in the binder/conductive additive, the active cathode material and the current collector. LIBS often causes high variations in signal intensity from pulse to pulse, so concentration determination is, in general, conducted on the average of many pulses. We show that the spot-to-spot variations we measure are governed by the microstructure of the cathode foil and are not an expression of the limited precision of the LIBS setup.
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