The complex ray theory of photodeflection signal formation: Comparison with the ray theory and the experimental results

Abstract

A theoretical study of Gaussian probe beam interaction with thermal waves on the basis of the complex geometrical optics equations is presented. This method of describing probe beam propagation in a nonhomogeneous medium, called the complex ray theory, takes into account the influence of the thermal wave on both amplitude and phase of electric field in the probe Gaussian beam. A comparison between the complex ray theory and previously proposed theories is made. Adequate experimental data confirming the correctness of the presented theory are also given. The least-squares procedure was used in multiparameter fitting the theoretical results to the experimental data and some parameters of the experimental setup were determined. It is proven that the complex ray theory allows correct quantitative interpretation of the data obtained in photodeflection experiments.

Determination of Structural Parameters of Thin-Film Photocatalytic Materials by BDS

“…The change in the refractive index and its gradient deflects the probe beam and change its phase [9,14]. The deflection of the PB is expressed by the change in the coordinate of its trajectory as [9,14] …”

“…The experimental conditions are chosen in such a way that only the examined deposit is assumed to be an absorbing medium. In such a situation temperature oscillations (TO) obtained by solving the heat diffusion equation with the boundary condition of temperature and heat flux continuity at the fluid-sample-support interfaces, has the form [7][8][9],…”

“…The deflection of the PB results in the change of its divergence and thus in the change of the PB electric field amplitude A [9,14]. In the detector plane (z D ), the amplitude is expressed by [4,9] A…”

“…The goal of this work is to extract information, from beam deflection (BD) measurements, about structural properties of some photocatalytic materials by comparing the measured results with theoretical values obtained by the use of a theoretical description based on the complex geometrical optics equations [9], according to which the probe beam (PB) interaction with the field of ThW consists of two effects: its deflection and phase change. Deflection is a result of a refractive index gradient in the fluid above the sample surface that changes the trajectory and divergence, and thus the amplitude of the PB.…”

Photothermal methods for determination of thermal properties of bulk materials and thin films

“…A probing beam passes through the region in which the thermal wave is propagating and its deflection beam gives information about the amplitude and the phase of the thermal wave. Although detailed theoretical modelling of this detection method is quite complicated [22,23], the simplified single ray model for interpretation of experimental results is often acceptable [23].…”