Optical characterization in commercial paints helps to improve and optimize the fabrication process and to minimize the cost of the final product. The paint under study is elaborated with a polymer matrix and some amount of particulate inclusions, its main characteistics are good quality, homogeneity of white appearance and brightness. When dried it is transparent. We prepare echelled layers with different paint thickness deposited onto transparent and metallic substrates and measure its reflection and transmission for both colorimetric and angular variation of the incident light. The experimental results allow the determination of the refractive index and thickness. Correlation with the granular structure is treated with different models, the size and filling factor of the inclusions playing an important role.
The inherent temperature stability of a fiber voltage sensor is far from industrial requirements. Usually, a special channel for a temperature control is needed. Temperature- dependent birefringence of optical elements, such as a quarter-wave plate and a sensitive crystal, is the main source of temperature-induced drift of sensor parameters. To solve this problem we used a special back reflecting prism as a phase-retarding element, BTO crystal as a sensitive element, and a double-pass scheme. The double-pass scheme enables to diminish the negative role of the optical activity in the crystal, to increase an interaction length and, thus, to enhance the sensitivity of the sensor. The special back reflecting prism demonstrates temperature stability more than 20 times better, than a zero-order quartz quarter wave plate. This permits to decrease the temperature-induced drift of sensitivity. The sensor demonstrates temperature stability of (1.5% from -20 degrees Celsius to 60 degrees Celsius) and sensitivity of 0.145% per 1 V rms at 850 nm without using an additional temperature control channel.
The scattered light from a bi-layer system with a shallow random rough surface bounded by semi-infinite dissimilar optical media is calculated. Results are obtained by assuming a gaussian roughness spectrum for the random rough surface and the formalism is applied to simulate the scattering in the ATR-Kretschmann configuration, allowing the excitation of guided waves.
Photoluminescence (PL) from (Al, Ga)As quantum-wire arrays grown on vicinal (111)B GaAs substrates by molecular beam epitaxy is reported for the first time. A peak at 1.826 eV is attributed to excitonic recombination in the built-in quantum-wire array, and a peak at 1.759 eV and a low PL emission band also originate from the serpentine superlattice structure. For comparison, the epilayers were also deposited on (100) GaAs substrates simultaneously. But the PL results indicate that they are the alloy-well structures. We explain these PL results with a model and draw a conclusion that steps on (111)B surface can play a very important role in crystal growth.
The sensitivity of the attenuated total reflection (ATR) technique to surface modifications allows the study of biological or medical phenomena where solutions segregate to form a layer on the walls of the sample holder. We present an immunoassay study of IgG antigen reacting with specific antibodies in saline solution on an aluminum thin-film attached to a prism, forming the bottom of the container where the reaction takes place. During the reaction a layer is adsorbed on the aluminum film showing a resonant absorption peak in the reflected signal that shifts towards larger angles of incidence at every step of the reaction. These shifts are related to the optical properties and the thickness of the adsorbed layers and may be quantified. This work presents the experimental setup and qualitative results of this reaction.
The reflected and transmitted fields scattered from a layered structure, build up of N thin films with shallow rough interfaces and bounded by two semi-infinite media are determined to analyze the effects of roughness in the optical response of a given multilayer system. Each layer is assumed to be homogeneous, isotropic, local, linear and characterized by a frequency dependent complex dielectric function. All rough interfaces are modeled by using a stationary random process, and the Rayleigh criteria is used in the mathematical treatment because of the shallowness of the defined roughness. Two independent integral equations relating the reflected and transmitted fields to the incident wave are found. These will allow a recursive calculation of the overall optical responses. The solution involves Fourier coefficients of functions dependent on the roughness profiles. This treatment is shown to be valid for both TM(p) or TE(s) states of polarization. Numerical results are obtained for the case of a two layer system, with two of the interfaces present Gaussian roughnesses and compared to some experimental data.
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