COMPUTING METHOD FOR EVALUATING THE ABSORPTION-COEFFICIENT OF INFRARED OPTICAL-ELEMENTS

The paper presents a new computing method for the bulk absorption coef ficient of an optical component. The method is based on the general so lution of the heat diffusion equation calculated for the case where th e component is irradiated by a laser beam. From the practical point of view this new method simplifies the measuring process of the absorpti on coefficient because it requires, as input data, the value of the te mperature rise in a single point at one moment. To establish the most suitable moment and position for the measuring point in order to reduc e the errors, this method was numerically simulated on GaAs and ZnSe s amples irradiated with a TEM00 CO2 laser beam. An error analysis was c onducted to find the required precision for the experimental measureme nts to obtain accurate data. To experimentally test this method, an ex perimental setup, based on a laser calorimeter was developed and the a bsorption coefficient of four ZnSe samples was evaluated. The results were proved to be in good agreement to the results provided by the pul se and gradient method mentioned in ISO 11551, applied in the same exp erimental conditions as the proposed method. (C) 1998 Elsevier Science B,V. All rights reserved.