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The present paper describes a novel implementation of the continuous phase shifting method (PSM), named heterodyne holography, in a scanning probe microscope configuration, able to retrieve the complex scattered field in on-axis configuration. This can be achieved by acquiring a continuous sequence of holograms at different wavelengths in just a single scan through the combination of scanning interference microscopy and a low-coherent signal acquired in the frequency domain. This method exploits the main advantages of the phase shifting technique and avoids some limits relative to off-axis holography in providing quantitative phase imaging.

This work aims to evaluate comparatively the environmental impact of solar photovoltaic and wind power plants. The conceptual design and the initial preliminary design steps in the material selection process were considered. The assessment was made using two different metrics, embodied energy (EE) and carbon footprint (CF). Five different configurations of wind power plants and a set of photovoltaic panels in a power plant were evaluated. In the wind power plants, the generator, the materials, the height, and the tower type were varied. For manufacturing the towers, the following parameters were considered: material, height, and generator power. The photovoltaic power station can provide up to 1.5 MW. The materials selected for embodied energy and carbon footprint assessment followed two criteria: the greatest mass percentage participation and the greatest value of embodied energy and carbon footprint of each material used. For the calculation of distances travelled from suppliers of raw materials and components used in the photovoltaic panels and wind power plants, the considered destination was the city of Viana do Castelo (north of Portugal), one of the regions with tradition in wind power production and installations. The result is favorable to the concrete column, which achieved the best result of EE and CF. The Oebels 1.5 MW tower with an 80-m concrete column showed an EE of 0.0150 kWh/kWh (19.71% a 3.0 MW 120-m concrete column) and a CF of 4.77 gCO2/kWh (21.90% of the Rocha 3.0 MW 120-m concrete column). Comparing the 1.5 MW photovoltaic plant with the concrete column 1.5 MW wind power, the result is favorable to the concrete column. Taking into account that the values of the photovoltaic power plant are EE of 0.0638 kWh/kWh and a CF of 16.21 gCO2/kWh, the concrete column 1.5 MW represents 23.51% of the EE and 29,43% of the CF. This advantage of the concrete towers repeats for the other columns. The results show that the best configuration is the wind power plant with a concrete column. For further studies, a comparison between concrete and truss tower at the same work conditions is suggested.

We investigate the accuracy and limits of validity of the two-wave approximation in the dynamical theory of electromagnetic scattering by periodic dielectric media. The errors ensuing from the approximation are estimated by applying the dynamical theory to a scattering problem for which an alternative exact electromagnetic solution is available and comparing results. The conditions for applying the approximate theory and its accuracy are discussed in terms of concepts peculiar to the classical dynamical theory of the scattering of X-rays in crystals, such as the Ewald sphere in the reciprocal space and the resonance error. After introducing the basic equations of the dynamical theory of electromagnetic scattering by three dimensional periodic dielectric media, the theory is applied to the scattering by one-dimensional periodic layered structures where a rigorous analytical solution is available. The analysis of the errors involved in the two-wave approximation indicates that, in the general case, the quality of the approximation cannot be quantified in terms of just the resonance error but it is also strongly affected by the dielectric contrast. Simple formulae are reported yielding a reliable error estimate in many practical cases. an extension of the results to the two and three dimensional case is also provided. Finally, it is suggested that a modification of the boundary conditions which are usually enforced in the dynamical theory when solving the propagation equation could improve its accuracy and extend the limits of validity of the two-wave approximation.

The mutual interference of light scattered inside an extrinsic Fabry–Perot microcavity, fed by a low-coherence light, is exploited to achieve infrared imaging in a liquid environment. The transverse field distribution inside a cavity is shaped by the effect of scattered interfering waves in a lens-free system. Reflectivity and contrast phase maps are extracted through the analysis of the cavity response in the time domain. This approach allows to conjugate noninvasivity, subdiffraction imaging, possible quantitative evaluation of dielectric constants and infrared spectroscopy, making it suitable for biological applications.

We investigate the accuracy and limits of validity of the two-wave approximation in the dynamical theory of electromagnetic scattering by periodic dielectric media. The errors ensuing from the approximation are estimated by applying the dynamical theory to a scattering problem for which an alternative exact electromagnetic solution is available and comparing results. The conditions for applying the approximate theory and its accuracy are discussed in terms of concepts peculiar to the classical dynamical theory of the scattering of X-rays in crystals, such as the Ewald sphere in the reciprocal space and the resonance error. After introducing the basic equations of the dynamical theory of electromagnetic scattering by three dimensional periodic dielectric media, the theory is applied to the scattering by one-dimensional periodic layered structures where a rigorous analytical solution is available. The analysis of the errors involved in the two-wave approximation indicates that, in the general case, the quality of the approximation cannot be quantified in terms of just the resonance error but it is also strongly affected by the dielectric contrast. Simple formulae are reported yielding a reliable error estimate in many practical cases. an extension of the results to the two and three dimensional case is also provided. Finally, it is suggested that a modification of the boundary conditions which are usually enforced in the dynamical theory when solving the propagation equation could improve its accuracy and extend the limits of validity of the two-wave approximation.