Calibration of the retardation inhomogeneity for the compensator-rotating imaging ellipsometer.

Owing to high accuracy in the whole measurement range, the compensator-rotating method is a main approach for the single-point ellipsometric measurement. The disadvantage of this method is the complexity resulting from the retardation calibration for the rotating compensator. The compensator-rotating imaging ellipsometer, a system combining the optical microscope and the single-point measurement ellipsometer, faces a similar issue. An important problem for the imaging ellipsometer is that the retardation of the compensator manifests inhomogeneity over the view field. Here, we propose a calibration method of the retardation of the compensator for the imaging ellipsometer. The approach was tested experimentally with a homebuilt imaging ellipsometer by generating maps of the ellipsometric parameters $\Delta$Δ and $\psi$ψ of samples of a Si wafer and an opaque Cr thin film.

Impact of Ag2O Content on the Optical and Spectroscopic Properties of Fluoro-Phosphate Glasses.

Glasses with the system (84.60-x) NaPO3-5 ZnO-(9.40-x) NaF-x Ag2O-1 Er2O3, (x = 0, 2, 4, and 6) (mol%) were synthesized by the conventional melt-quenching method. The impact of the addition of Ag2O on the physical, thermal, structural, and optical properties of the glasses is discussed. The Judd-Oflet analysis was used to evaluate the radiative properties of the emission transitions of the glasses. The enhancement of luminescence properties due to Ag2O is discussed in terms of consequent changes in the local electromagnetic field, symmetry, and the ligand field around the Er3+ ion. The heat treatment of the glass was performed in order to precipitate Ag nanoparticles (NPs), which form as a layer at the surface of the heat-treated glasses as confirmed using scanning electron microscopy (SEM). The Ag NPs were found to increase the intensity of the emission at 1.5 µm.

Extraction of polarization properties of the individual components of a layered system by using spectroscopic Mueller matrix analysis.

In semiconductor and optics fields, some devices are constructed with layered systems including two or three individual layers. Measurement of polarization properties of the individual components of these layered systems is often desired. In this paper, we present methods allowing the simultaneous extraction of the polarization parameters of the individual components by analyzing spectroscopic Mueller matrices (measured at two wavelengths). We have studied both retarder-retarder and retarder-polarizer-retarder systems. The validities of the methods were successfully tested using both simulations and real polarization systems.

Correction of large retardation window effect for ellipsometry measurements using quasi-Newton method.

Optical windows attached to the sample chamber for ellipsometry measurements often manifest stress-induced retardation. In reality, the retardation is not always small enough to be simplified with the small angle approximation, varies within the optical beam, and furthermore may change with the evolution of the environmental conditions of the chamber. Large retardations and retardation distributions result in complicated Mueller matrices of the input window-sample-output window system. Consequently, extensive computation is required to obtain the true ellipsometric parameters (Δ,Ψ) of the sample. In this paper, we show that the quasi-Newton method can be used to simultaneously obtain 14 unknown parameters (including ellipsometric parameters) from the Mueller matrix, with a single measurement under conditions of large and inhomogeneous window retardation. A limitation of the method is that it is valid only for isotropic samples. The validity of the method has been tested using a set of samples: a silicon substrate, a TiN-coated silicon wafer, and a thermally grown silicon dioxide film. Measurements were done under the window effect and corrected using the proposed method. The corrected results showed excellent agreement with ellipsometric parameters obtained without window effect.

Luminescence of mesoporous silicon powders treated by high-pressure water vapor annealing.

We have studied the photoluminescence of nanocrystalline silicon microparticle powders fabricated by fragmentation of PSi membranes. Several porosities were studied. Some powders have been subjected to further chemical etching in HF in order to reduce the size of the silicon skeleton and reach quantum sizes. High-pressure water vapor annealing was then used to enhance both the luminescence efficiency and stability. Two visible emission bands were observed. A red band characteristic of the emission of Si nanocrystals and a blue band related to localized centers in oxidized powders. The blue band included a long-lived component, with a lifetime exceeding 1 sec. Both emission bands depended strongly on the PSi initial porosity. The colors of the processed powders were tunable from brown to off-white, depending on the level of oxidation. The surface area and pore volume of some powders were also measured and discussed. The targeted applications are in cosmetics and medicine.

Polarization properties of scattered light from macrorough surfaces.

We have characterized macrorough surfaces by measuring angle-resolved Stokes parameters of scattering. The analysis of the parameters as a function of a virtual scattering angle shows that polarization properties of the scattering in the plane of incidence display a very strong dependence on the surface roughness. The method and results of this analysis have a significant impact on the application of light scattering to the inspection and process-evaluation industry.