RESUMO
We report on the theoretical analysis of a detector type influence on the normal deflection signal in photothermal experiments. Two cases are examined. In the first, the quadrant photodiode was considered as the detector; in the second the signal from the position detector, which measures the central moment displacement of the probe beam, was analyzed. Both analyses were carried out within the framework of the complex ray theory. The normal photodeflection signal was found to depend on the type of detector used in the photothermal deflection experiments for some parameters of its setup.
RESUMO
A comparison is made of three methods for modeling the interaction of a laser probe beam with the temperature field of a thermal wave. The three methods include: (1) a new method based on complex ray theory, which allows us to take into account the disturbance of the amplitude and phase of the electric field of the probe beam, (2) the ray deflection averaging theory of Aamodt and Murphy, and (3) the wave theory (WT) of Glazov and Muratikov. To carry out this comparison, it is necessary to reformulate the description of the photodeflection signal in either the WT or the ray deflection averaging theory. It is shown that the differences between calculated signals using the different theories are most pronounced when the radius of the probe beam is comparable with the length of the thermal wave in the region of their interaction. Predictions of the theories are compared with experimental results. A few parameters of the experimental setup are determined through multiparameter fitting of the theoretical curves to the experimental data. A least-squares procedure was chosen as a fitting method. The conclusion is that the calculation of the photodeflection signal in the framework of the complex ray theory is a more accurate approach than the ray deflection averaging theory or the wave one.
