Abstract

There has been growing interest in the use of polymer pyroelectrics for IR detection. Vinylidenefluoride-trifluoroethylene (VDF/TrFE) copolymer is flexible, crystallizes naturally into a polar β form, and can be rendered pyroelectric without being stretched. We have developed a series of composite materials based on poly(VDF/TrFE):(70/30) containing different concentrations of the ceramics: BaTiO₃, PbZrO₃, LiTaO₃, and PbTiO₃. Infrared detectors were fabricated by direct deposition of the composite thin films (2–75µm thick) onto substrates preconnected to the readout electronics. Dielectric properties were measured both before and after the corona-poling procedure. The voltage and current responses to 10.6µm laser radiation were also studied as a function of the film fabrication method, composition, and modulation frequency. A voltage responsivity of 1.5 V/W (R_L = 2 × 10⁶ Ω) and a current responsivity of 5 µA/W at 6 Hz were obtained. The pyroelectric signal was a linear function of the incident power for power densities up to 16 W/cm². The time constant for some detectors was below 0.25 ms. A model for the numerical analysis of the response of composite film detectors was also developed.

© 1990 Optical Society of America