Study of Piezoelectric Oscillations in Wideband Pyroelectric LiTaO3 Detectors

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Abstract
The use of freely suspended LiTaO3 pyroelectric detectors for wide‐band application is severely hampered by mechanical resonances of the detector (typically several hundred kHz) which are excited by the incident radiation. These resonances give rise to slowly decaying oscillatory piezoelectric signals superimposed on the pyroelectric signal. It is shown that by suitable mounting of the detector films these resonances can be entirely eliminated, thereby increasing the useful bandwidth of the devices to at least several hundred MHz. In addition, it is shown that when the incident radiation is modulated at a mechanical resonance frequency of a freely suspended LiTaO3 detector, considerable enhancement of the current and voltage response is obtained. The experimental results are found to be in reasonable agreement with results calculated for LiTaO3 by including thermal expansion in the equations of motion of a pyroelectric crystal.