Joan Power

Associate Professor

B.Sc. (Concordia University, 1981)
Ph.D. (Concordia University, 1986)
NSERC Postdoctoral Fellow (University of Toronto, Dept. of Mechanical Engineering, 1986-87)

Email: Joan.Power [at] McGill.CA

Research Themes:


Research Description:

Thermal Wave Imaging: Research is ongoing into the development of spectroscopic imaging methods which detect optical absorption in thin film samples by measuring heat evolution in materials due to non-radiative decay processes accompanying light absorption.

At the surface of an optically inhomogeneous material which is irradiated with a pulsed radiation beam, an impulse temperature transient is established whose dependence is determined by the time required for heat conduction from absorbing features at variable depths in the sample to the sample surface, as well as the depth dependence of the sample's thermal properties. Inverse problem theory may then be used to obtain a quantitative map of the spectroscopic absorption in the sample, from the measured temperature time transient recovered in an experiment.

A variety of probes have been used in the laboratory to detect the surface temperature changes accompanying light absorption in the sample: by optical probing of refractive index gradients in a fluid layer above the surface (mirage effect), by contact temperature sensing using thin film calorimetric sensors (photopyroelectric effect), and more recently, by parallel thermal wave interferometry, in which the entire image field of a heated sample may be captured in parallel. Theoretical and experimental work in the group has established the depth profile methodologies on well characterised materials, and current research in inverse problem theory is enabling the recovery of depth dependent optical and thermal properties on materials of unknown characteristics. Areas of application to polymer science, are numerous, and include the evaluation of photodegradation and barrier properties of packaging materials, coatings, paints, plasticisers and their degradation mechanisms under environmental exposure.