Basic methods of laser photothermal spectroscopy, which are used to study photoinduced absorption in various media, are briefly considered. Comparative analysis of these methods is per- formed and the latest results obtained in this field are discussed. Different schemes and examples of their practical implementation are considered.

https://iopscience.iop.org/article/10.1070/QE2013v043n01ABEH014912/pdf

Laser photothermal spectroscopy of light-induced absorption

A method and a device are used to analyze and measure by means of radiometry physical parameters of a layered material. These parameters include the absorptivity B, the diffusivity A of the surface layer and the thermal resistance R of the interface between the two layers. A sample of the material is excited by means of a flux of thermal energy amplitude modulated at a high frequency and a low frequency. The parameters are computed from the measured phase shift and amplitude of the resulting thermal signal. The method and the device are applicable to non-destructive testing of industrial products.

Method and device for analyzing and measuring physical parameters of a layered material by thermal radiometry

L'invention concerne un procede et un dispositif d'analyse et de mesure des parametres physiques d'un materiau (1) en couches (10,11), parametres tels que l'absorptivite B, la diffusivite A de la couche superficielle, et la resistance thermique R de l'interface entre les deux couches par radiometrie. The invention relates to a method and a device for analyzing and measuring physical parameters of a material (1) in layers (10,11), parameters such as absorptivity B, the diffusivity of the surface layer, and the thermal resistance R of the interface between the two layers by radiometry. L'echantillon est excite au moyen d'un flux d'energie thermique, module en amplitude a une frequence haute Fh et a une frequence basse Fb. The sample is excited by means of a thermal energy flow, amplitude modulated at a high frequency Fh and a low frequency Fb. Les parametres sont calcules a partir des mesures de phase et d'amplitude du signal thermique. The parameters are calculated from the phase and amplitude measurements of the thermal signal. Application au controle non destructif de produits industriels. Application to nondestructive testing of industrial products.

Method and device for the measurement and analysis of the physical parameters of a layered material using thermal radiometry

The specific features of contactless measurements of the body surface temperature by the method of repetitively pulsed laser photothermal radiometry are considered and the requirements to the parameters of the laser and measurement scheme are formulated. The sensitivity of the method is estimated. The advantages of laser photothermal radiometry over the conventional passive radiometric method are discussed.

http://iopscience.iop.org/article/10.1070/QE2003v033n12ABEH002564/pdf

Measurement of the body surface temperature by the method of laser photothermal radiometry

The knowledge of photoinduced absorption spectrum gives important information about the material defect structure, which largely determines its properties and practical application. This article reviews the developments and patent literature in the area of photothermal methods modified for measurement steady state and temporal behavior of light-induced (photoinduced) absorption in bulk materials and thin films. These noncontact methods are characterized with high sensitivity, temporal and spatial resolution and successfully expand traditional techniques. A number of various schemes of photothermal methods were modified for light-induced absorption measurement where compared. Every item has its advantages as well as disadvantages. The results of analysis show that existing photothermal technique is a promising solution to meet the size, simplicity of operation, inexpensiveness, possibilities, and cost requirements of this technique.

Light-Induced Absorption in Materials Studied by Photothermal Methods

A new method was developed for measuring weak absorption in bulk materials and coatings It is based on recording a change in the integrated thermal radiation flux from the surfaces of samples heated by periodic laser radiation pulses The possibility is discussed of making absolute measurements by simulation of surface heat sources in the materials investigated, and also by comparing them with standard samples The sensitivity of the method is estimated and the results of absorption measurements on a number of materials are presented Consideration is given to limitations imposed on the operating range of laser pulse repetition frequencies by the thickness of the layer of the substance emitting the thermal flux and by the increase in the transverse dimensions of the illuminated area arising on account of thermal diffusion

V N Lopatkin

Papers

Laser modulation photothermal radiometer—a new method for measuring weak absorption in bulk materials and coatings