Photothermal Measurement of Optical Coating Thermal Transport Properties

Abstract

We report the present status of a project to measure the thermal transport properties of optical coating materials in thin-film format. The measurement technique employs a noncontact nondestructive method based on thermal diffusion-wave interferometry. Initial results confirm the feasibility of the method. Data on nickel coatings show thin film transport parameters slightly smaller than corresponding bulk values, and in addition clearly display the effects of a nonideal thermal bond between the coating and the substrate.

<title>Thermal transport properties of optical thin films</title>

“…Finally, the product hx must be much less than one in order that thermal contact resistance effects of the coating-to-substrate interface to be negligible. Under these conditions, the functions cos x and cosh x approach unity, and the functions sin x and sinh x approach x in equations (1)(2)(3). In this case, the difference phase 4 approaches zero (thermally thin coating) and the front surface and rear surface phase 4fs and 4approach the following limit 4.…”

“…[1] and [3] respectively. The phase is generally shifted by +45°i n the plots because this yields a family of interference oscillations symmetrical about zero degrees in the solution of the heat diffusion equation in the one dimensional heat flow limit.…”

“…Analytical modelling for the one dimensional heat flow limit has been carried out using a generalization of the techniques presented in Ref. [1]. Fig.…”