Sensing of pulsed radiation with Pyroelectric Detectors

In existing literature, the response of a Pyroelectric Detector (PED) has been modeled almost exclusively with slow varying excitation signals having the shape of either a square or sinusoidal wave. Their naturally slow thermal response (~1 second) is not favourable in view of their use in a variety of faster existing or emerging applications. Even so, PEDs are still good candidates for e.g. mid-infrared (IR) and Terahertz (THz) sensor systems operating under room-temperature conditions. In this paper we study the performance of PEDs using an original PED simulator. Finite Element Methods (FEMs) are used to obtain the temperature field in a LiTaO₃, pyroelectric crystal incorporated in a commercial detector, taking into account details from the manufacturer concerning its geometry, thermal specifications (materials) and the integrated electronics. The results from the finite element model are verified by the experimentally derived transient, obtained from the measured voltage response of the PED to a step change in illumination. Further, the bandwidth of the detector and frequency response of the detector is calculated with the PED simulator allowing performance analysis under noisy conditions. Signals resulting from pulse trains of varying duty cycle are modeled, down to 2ns pulses at 500kHz repetition rate, allowing decisions on the optimal signal processing for any particular case. The novelty is the complete performance model of a commercially available PED, capable to predict the transient response to a variety of input signals with adjustable parameters (i.e. duty cycle, frequency). The observed deviation of the sensitivity as a function of duty cycle, is not intuitive and needs to be accounted for at calibration.