We present an experimental and post-processing scheme that allows ultrasound surface wave detection by means of an unstabilized homodyne interferometric technique. We register interference signals for a set of uncalibrated phase shifts and, from them, we are able to retrieve the normal surface displacement of a thin aluminium plate. The results obtained with this technique are then compared to robust and more traditional phase recovery methods such as the Carré algorithm and the 11-step windowed discrete Fourier transform algorithm. For both algorithms, we found a correlation superior to 99.9%, when compared to the results of the proposed technique. This non-destructive testing scheme represents a simpler and less-expensive alternative to other existing laser ultrasonic techniques.

Abstract. Laser techniques for particle sizing are used in industrial as well as in scientific applications due to the direct connection between the measured quantities in light dispersion processes and particle properties. We have successfully implemented two light scattering techniques, adapted to function with a CCD camera as detector: the dynamic technique, studies the temporal correlation of the scattered light in a fixed direction (known as DLS for "Dynamic Light Scattering"); the static technique, retrieves the mean intensity distribution as a function of the scattering direction. We present experimental results on monodisperse and polidisperse solutions of latex spheres diffusing in water and compare the performance of these techniques. The statistical averaging over the CCD pixels allows significant reduction of measurement times.

Monochromatic plane waves allow the description of many of the properties of propagating, reflected and transmitted radiation through media of different optical properties. However, some of their characteristics only appear when considering limited beams. In this work we determine and analyse (to the second order) some characteristics of the transmission of beams (spatially limited) or pulses (limited in time), in both cases with Gaussian distribution. It is assumed that the transmission takes place through an isotropic planeparallel plate. If the beam is limited in space, we consider that the mean direction of the wave is perpendicular to the plate. On the other hand, when the beam is limited in time, we consider that all the plane waves impinge normally to the plate. We compare the non-geometric effects for both kinds of limited beams, for the cases where the plate is transparent, absorbing or with linear gain.

Piezoelectric devices are critical components in many different fields. They are often used as ultrasonic transducers, micro/nano positioners, and actuators. Electrical characterization of these devices can be performed by means of very well known techniques focused mainly on impedance measurements at different frequencies. However, since the measurement of mechanical properties corresponds to the determination of very small displacements, an optical interferometer is required. In this work, we propose the use of two coupled polarization interferometers for measuring the displacement of a mirror mounted in a piezoelectric device. The first one corresponds to a Michelson type interferometer with two orthogonally polarized branches. One of them is set as a reference, and the other changes its length as the piezoelectric under test is excited. Instead of forcing the interference of both branches with an analyzer, both signals are entered to a second polarization interferometer. This second interferometer consists mainly of a single birefringent crystal plate that provides a spatial interferogram. According to the phase change between reference and test signals, there is a uniform phase added to all of the points of the interferogram. We take advantage of this feature and of the stability of this second interferometer to recover the phase and the displacement of the mirror by means of very well known phase recovery methods.Resumen-Los dispositivos piezoeléctricos son componentes críticos en diversos campos. A menudo son usados como transductores ultrasónicos, micro/nano posicionadores y actuadores. La caracterización eléctrica de tales dispositivos puede ser realizada a través de diversas técnicas enfocadas primordialmente en la determinación de la impedancia a diferentes frecuencias. Sin embargo, la determinación de las propiedades mecánicas en general está asociada a la medición de desplazamientos muy pequeños. Por este motivo, se requiere un interferómetroóptico para realizar tales medidas. En este trabajo, proponemos el uso de dos interferómetros de polarización acoplados para medir el desplazamiento de un espejo montado en un dispositivo piezoeléctrico. El primero corresponde a un interferómetro de tipo Michelson con dos ramas polarizadas ortogonalmente. Una de ellas es tomada como referencia, mientras que la otra rama cambia su longitud acorde a la excitación que recibe el piezoeléctrico bajo estudio. Luego, en lugar de forzar la interferencia de las ramas utilizando un simple analizador, se interpone un segundo interferómetro de polarización. Este segundo interferómetro consiste principalmente en unaúnica lámina de cristal birrefringente que provee un interferograma espacial. Acorde al cambio de fase entre las ramas de referencia y de prueba, hay una fase uniforme añadida en todos los puntos del interferograma. De este modo, aprovechando tanto esta característica como la estabilidad del segundo interferómetro, podemos recuperar la fase y, consecuentemente, el desplazamiento del espejo por medio de métodos de r...

No abstract