Photopyroelectric thermal wave detection via contactless capacitive polyvinylidene fluoride (PVDF)-metal probe-tip coupling

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Abstract
In the past, thin‐film photopyroelectric detectors have provided a simple means of measuring thermal properties of solid samples. This article presents a theoretical model and experimental results demonstrating a new contactless capacitively coupled photopyroelectric detection technique. The photopyroelectric (P2E) effect with contactless capacitance PVDF‐metal probe‐tip coupling was demonstrated and used to obtain thermal information from a solid. Due to the small diameter of the probe, the local values of the thermal wave field in the solid were measured. The modulated photothermal source on the surface of the sample induces an oscillating temperature field in the pyroelectric material, which produces a displacement current proportional to the temperature change. The metalized surface of the pyroelectric thin film and a metal tip electrode facing the opposite unmetalized surface form a capacitor which is charged at the same frequency as the modulated light beam. The oscillating capacitive voltage provides a noncontact mechanism to extract photothermal information, since the electric field generated in the capacitor does not require plate contact with the PVDF element.