Narrow and broad band diode laser absorption spectrometry—concepts, limitations and applications

Implementation concepts as well as the fundamental aspects concerning the analytical capability of diode laser spectrometry with respect to narrow and broad band absorption are discussed. The applicability is illustrated by means of the element-selective analysis of flames or plasmas and the molecular analysis of liquids or turbid media. While in narrow band absorption one diode laser and different modulation techniques can be applied to obtain very low detection limits, two diode lasers and a double-beam scheme should be used when the absorption bands are very broad. The two-laser, double-beam method is demonstrated by means of absorption measurements in a turbid medium and by concentration analyses of liquid samples applying the surface plasmon resonances technique.