Calculation of Small Optical Absorption Coefficients from Calorimetric Experimental Data

The absorption coefficient α can be calculated from the equation: $${\mathrm{\alpha =[P}}_S{t}_{\mathrm{BR}}^2{\mathrm{/lP}}_{T^n}{\text{(1+r}}_{\mathrm{BR}}^2\mathrm{)]}$$ , where P_S and P_T are the power lost in the sample and the power transmitted, respectively; n and l are the index of refraction and the length of the material; t_BR²/n and r_BR² are the transmittance and reflectance of the exit end of the sample. It is assumed that the light impinges normally, and that the specimen has plane parallel entrance and exit faces.