Measurement of thermal diffusivity based on the photothermal displacement technique using the minimum phase method

Abstract

A method of measuring the thermal diffusivity of solid material at room temperature using photothermal displacement is proposed. The influence of the parameters, such as the radius and modulation frequency of the pump beam and the sample thickness, was studied. From the minimum position of phase of measured deflection with respect to the pump beam, the thermal diffusivity of the materials can be obtained. The position where phase has the minimum value is determined using multiparameter least-square regression fitting. The experimental values for different samples obtained by applying the method are in good agreement with the literature values.

Numerical study on visualization method for material distribution using photothermal effect

“…Further, Q i is described as a periodic heat source: (3) as a type of sine wave with a specific frequency to simulate the modulated pump beam [12,16,17]. Q i has a gaussian distribution in the x and y directions.…”

“…The heat flux and temperaturebalanced condition between air and the test sample were set. After the temperature fields for the three domains are calculated, the deflection angle of the probe beam can be calculated by integrating the gradient of the index of refraction with respect to the temperature in the front air region along the probe beam path parallel to the sample surface [12,16,17]:…”

“…1, when the test sample is irradiated by the modulated pump beam, the energy is absorbed by the photothermal effect, and the temperature increases [11]. Because the absorption coefficient of air is very small, the amount of energy from the modulated pump beam absorbed in the air layer can be neglected [12]. The absorbed energy is diffused in all directions by thermal diffusion, which changes the temperature of the test sample and forms a unique temperature distribution field that depends on the frequency of the modulated pump beam and the test sample's thermal diffusion coefficient distribution.…”

“…Because of this practical problem, in this study, the photothermal imaging technique is studied using photothermal deflection, which results from the photothermal effect [9,10]. Deflection is known to occur with a certain delay from the modulated pump beam because of the diffusion time, which has a unique value depending on the thermal properties of the material [11][12][13]. The basic concept of this research is that the material distribution can be reconstructed by analyzing the delay of the probe beam deflection from the modulated pump beam.…”

Feasibility of Novel Rear-Side Mirage Deflection Method for Thermal Conductivity Measurements

“…Ospal [ 29 , 30 ] and Jeon [ 31 ] conducted one-dimensional and three-dimensional theoretical analyses of the surface temperature and thermoelastic deformation. Lee [ 32 ] and Jeon [ 33 ] experimentally measured the thermal diffusivity. For the mirage deflection method, Salazar et al [ 16 ] established a thermal property measurement method for monolayer isotropic materials, and Jeon et al [ 34 , 35 ] studied the measurement of the thermal properties of monolayer anisotropic materials.…”