Photopyroelectric thin-film instrumentation and impulse-response
detection. Part II: Methodology
Review of Scientific Instruments, 58 (11):
2024-2032 (1987)DOI: 10.1063/1.1139510
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.