Mirage detection applied to low thermal diffusivity measurements of weakly absorbing thermally thin plasma polymerized film

We have successfully measured the thermal diffusivity of plasma polymerized thin film sample of m-toluidine, which is optically transparent at the pump wavelength and is thermally thin at the modulation frequencies for which the experiment has been performed. The mirage signal is analysed using the phase method. Since to the best of our knowledge, the thermal diffusivity of the sample is determined for the first time, the result is verified using the amplitude method. In order to study whether there is any influence of coupling media to measurements, the experiments are carried out using two different coupling media namely carbontetrachloride and liquid paraffin. Both the measurements have yielded the same result showing that the thermal properties of the coupling media do not contribute to the mirage signal.