In the present work three different topics were dealt with, which serve to extend the light emission of existing laser systems to wavelength ranges previously unattained. The laser spectroscopy is intrinsically limited to existing laser systems with fixed wavelength ranges and the development of further wavelengths is especially interesting in the near infrared and short wavelength visible to UV range. Especially the telecom wavelengths, i.e. the range in which telecommunication fibers have their transmission minimum, is interesting for further development.So far, Ga(In,As) lasers on InP substrate have been used in this system. Therefore, complex electronic couplers have to be built, which connect the laser systems to existing silicon technology. Accordingly, it is desirable to manufacture laser systems directly on silicon substrate. The material Ga(N,As,P) investigated in this thesis offers the possibility of pseudomorphic growth on silicon. The object of this research was the characterization of the band offsets of different materials in Ga(N,As,P) heterostructures. These band offsets are important for both electronic and optical properties of this structure. In this thesis the relevant offsets between Ga(N,As,P) and its barrier layers GaP and (B,Ga)(As,P) were determined by two different methods. The first method, photoluminescence excitation spectroscopy, allows the determination of higher states in the quantum well. A specially developed series with varied Ga(N,As,P) quantum film thickness allows to determine the band offsets from the stress-induced displacements of the bands using photoluminescence excitation spectroscopy. However, a relatively high effort of theoretical preliminary consideration is necessary to determine the corresponding transition energies to the band offsets. Therefore, the offset was also determined directly by X-ray photoelectron spectroscopy. This approach provides not only the offsets of the active material, but also the offsets of all layers involved in the structure. A comparison with the photoluminescence excitation spectroscopy provides a rounded picture of the band offsets of the structures. It could be shown that the valence band offset of the structures is very low. These investigations thus contribute to the further optimization of the structures towards silicon-based laser systems.A second approach to extend the existing wavelength regimes is nonlinear optical effects. Due to high field strengths, as provided by today´s lasers, a frequency conversion of the light takes place in non-centrosymmetric materials. This makes it possible to open up wavelength ranges for which no laser system exists. Especially in the blue and UV range of the light spectrum these effects are used. The second part of this thesis deals with the investigation of such nonlinear optical effects. This is divided into the determination of the absolute efficiency of the second harmonic frequency generation in the material KNbO3 and the investigation of novel adamantine-like clusters for the generation of white light in the visible and near-infrared spectrum.
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