Photopyroelectric thin-film instrumentation and impulse-response
detection. Part III: Performance and signal recovery techniques
Review of Scientific Instruments, 58 (11):
2033-2043 (1987)DOI: 10.1063/1.1139511
Abstract
Frequency-modulation time-delay spectrometry (FM-TDS) was compared
with stochastic excitation in photopyroelectric measurements on thin
solid samples. These methods involve broadband signal excitation
with simultaneous detection of all frequency components within the
response bandwidth of the photothermal system. Fast signal recovery
was achieved by FFT methods. Both FM-TDS and wideband random-noise
excitation were found to yield high-quality, band-limited impulse-response
information. Random noise measurements were found to be much less
susceptible to distortions and nonlinearities in the excitation wave
train. FM-TDS showed superior coherence and signal-to-noise ratio
(SNR) to random methods. The results of this work demonstrate a photopyroelectric
effect spectrometer capable of yielding fast, time-resolved information
equivalent to the response of a pulsed laser, with low peak power.
This important feature shows excellent potential for nondestructive
thickness, thermal diffusivity, and thermal conductivity measurements
on materials which are susceptible to optical damage.