A fundamentally new method for measuring optical coupling coefficients is described. A sample of a particular shape is subjected to a fixed tensile load and heated with pulsed optical radiation. The resulting peak tensile relaxation is proportional to the total absorbed energy; evolution of the coupling coefficient may thus be observed. A prototype system was constructed, and coupling coefficients were measured as a function of incident energy for CO2 laser pulses on bare and painted aluminum surfaces. With a sample of known absorptance and thermal properties, the system functions as a sensitive, fast-response, absolute-energy-measurement device.
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