Abstract
Frequency-modulation time-delay spectrometry (FM-TDS) has been implemented
in photopyroelectric measurements of thermal diffusivity, on a series
of well-characterized samples. The strategy of FM-TDS is sample excitation
by a fast linear frequency sweep, whose autocorrelation function
is mathematically equivalent to a Dirac delta function. The method
permits the fast recovery of high-quality frequency and impulse-response
information. Impulse responses recovered in the time-delay domain
showed good agreement with a Green's function model of transient
heat conduction. The present work demonstrates that the FM-TDS measurement
strategy yields photothermal information equivalent to that obtainable
from a pulsed laser system, with much lower excitation power.
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