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The in-guide pump and probe analysis illustrated in this paper is useful for the characterisation of photoinduced phenomena in thin films that are already part of an optoelectronic device. Measurements were carried on a-Si:H/ZnO waveguiding multilayers designed for the telecommunication wavelength of 1.55 μm. Because of the waveguiding geometry, the probe beam propagates along the film under test, a configuration that allows two advantages. First, the underlying layers do not affect the acquisition, and therefore the use of a transparent substrate is not necessary. Second, a longer region is available for the interaction between the pump and probe beams with respect to normal incidence probe beam setups, a characteristic conferring a high sensitivity to the technique. An analysis of the experimental data is proposed to extract information on the material, independent, e.g., of the device geometry. As an example, we illustrate an analysis of the photoinduced absorption by starting from measures directly performed on the a-Si:H core of an operating waveguide. [ABSTRACT FROM AUTHOR]

The in-guide pump and probe analysis is used for the characterization of photoinduced phenomena in thin films that are already part of an optoelectronic device. An analysis of the experimental data is proposed to extract information on the material, and as an example, an analysis of the photoinduced absorption by starting from measures directly performed on the a-Si:H core of an operating waveguide is illustrated.

Abstract: The infrared (IR) absorption dependence on visible light illumination has been measured in doped and undoped hydrogenated amorphous silicon carbide (a-Si1−x C x :H) films grown by plasma enhanced chemical vapour deposition. The measurements were made by a highly sensitive technique which exploits properly designed a-Si1−x C x :H/ZnO test waveguides for lengthening the interaction region between the IR and visible (VIS) radiations in the material. Experimental data show that boron doping strongly enhances the VIS light induced variation of the IR absorption, whereas the increase in carbon content has a quenching effect on the phenomenon. The a-SiC:H films have been also characterized by photoluminescence measurements. The spectra are dominated by a photoluminescence band, ranging between 1.4eV and 1.9eV. This band is enhanced by the increase in carbon content, while is strongly quenched with increasing B-doping level. On the basis of these results, a correlation is found between the measurements of optical absorption, photo-induced absorption and photoluminescence. The type and the density of defects induced in the films by the different growth conditions have been recognized as the origin of the different behaviors observed. [Copyright &y& Elsevier]