Passive Amplification Effect in Thin Pyroelectric Films

Abstract

Here we continue the description of the previously found passive amplification effect in thin pyroelectric films placed on a massive heat-conducting substrate. We show that in the definite modulation frequency range the amplification effect occurs i.e., a current generated by a thin pyroelectric film placed on substrate exceeds that in freely suspended film. The frequency dependence a pyroelectric current is illustrated by set of examples including achiral ferroelectric liquid crystals, ferroelectric polymers and polycrystalline compounds.

Longitudinal and transverse pyroelectric effects in a chiral ferroelectric liquid crystal

“…The low frequency branches of curves 1 and 2 describing the pyroelectric response have the univer sal form f 1/2 following from the solution to the heat conduction equation with the corresponding bound ary conditions [19,20]. The pyroelectric current in the high frequency range is independent of frequency [2][3][4]20], which is confirmed by the plateau on curve 2. The plateau on curve 1 is not exhibited due to the large time constant of the electric circuit: R load = 1 MΩ, C = 0.3 nF, and γ = 0.3 ms.…”

“…The main merit of pyroelectric detectors is a wide spectral interval of sensitivity. The spectral sensitivity per unit incident power in pyroelectric detectors depends only on the radiant emittance of the detecting surface, which can be close to the blackbody emittance (i.e., close to unity in a wide spectral interval from the visi ble to the far infrared ranges) [2,3]. In addition, the pyroelectric signal is proportional to the rate of tem perature variation, which can be higher than the space charge relaxation rate.…”

“…It should also be noted that although the pyroelec tric effect has been studied comprehensively, new fea tures of its manifestation have been reported in recent publications (e.g., passive enhancement of the effect in a pyroelectric film formed on a thick substrate [2,3] and the nonlinear pyroelectric effect [6]). In the former case, passive amplification of a sinusoidal sig nal as compared to the situation in a freely suspended sample can be attained in a certain frequency interval.…”