Abstract

Homodyne laser photopyroelectric spectrometry (PPES) is a new photothermal detection scheme which uses electronic mixing to downshift a high-frequency swept wave photothermal response into a bandwidth of approximately one kilohertz. A rapid photopyroelectric impulse response is recovered from the downshifted component at high time resolution and is used, here, in two different geometries, to probe the thermal and interfacial properties of assemblies composed of submicron-thickness polymer films deposited on the metallized surface of a pyroelectric thin-film detector. In the thermal transmission mode geometry, the sample is excited by irradiation in a very thin opaque surface layer, and the transit time of a heat pulse through the sample to the pyroelectric transducer can be used to obtain a thickness or thermal diffusivity measurement. By the use of an inverse mode geometry, a metal/polymer interface is excited by irradiation of an optically transparent polymer thin-film sample attached to the metallized surface of the pyroelectric transducer. Heat flow at short distances from the bond interface can be monitored by the pyroelectric effect through the high time resolution of the homodyne photopyroelectric measurement. The combination of information obtained in these two geometries with an analysis of the thermal wave reflections which occur at interfaces between materials of dissimilar thermal effusivity can be used to evaluate relative interfacial adhesion between the metal and polymer layer.

Photopyroelectric spatially resolved imaging of thermal wave fields

Marek Mieszkowski and Andreas Mandelis
J. Opt. Soc. Am. A 7(4) 552-557 (1990)

Photothermal measurements on optical thin films

E. Welsch and D. Ristau
Appl. Opt. 34(31) 7239-7253 (1995)

Thermal diffusivity in thin films measured by noncontact single-ended pulsed-laser-induced thermal radiometry

Wing P. Leung and Andrew C. Tam
Opt. Lett. 9(3) 93-95 (1984)

Surface absorption measurements of thin films by cavity-enhanced photothermal spectroscopy

H. A. Schuessler, S. H. Chen, Z. Rong, and Z. C. Tang
Opt. Lett. 16(8) 608-610 (1991)

Photothermal behavior of an optical path adhesive used for photonics applications at 1550 nm

Michael DeRosa and Stephan Logunov
Appl. Opt. 40(36) 6611-6617 (2001)