Pyroelectric Detectors and Linear Arrays for THz Tomography

Efthymiou Spyros, Krikor B. Ozanyan

School of Electrical and Electronic Engineering, The University of Manchester, Manchester M13 9PL, United Kingdom

ABSTRACT

PED receivers are promising for THz tomography because of their high room temperature sensitivity, low cost, compactness, ease of operation and, most notably, comparatively modest overheads for the manufacture of linear arrays. The performance of PEDs has been studied in the case of sinusoidal or square wave input, but not for pulsed operation needed for Temperature THz Tomography. In this work, we develop 3D models of the evolution of the temperature field in a LiTaO3 crystal mounted in a commercial detector can. This allows insight into the thermal and electrical response of PEDs to short (~1ns) pulses. Considering the timing response of the detector as the major target, the thermal behaviour of the detector is studied by utilizing two methods: 3D finite­element method (FEM) numerical calculations and the traditional heat­balance equation are applied for a commercial PED (SPH­43 from Spectrum Detector), using the COMSOL Multiphysics environment and NI LabVIEW respectively.

Within the more accurate FEM model, we discuss the characteristics of the detector's response to a very narrow (~ns) Gaussian pulse of thermal radiation discussing how the thermal droop is affected due to the non­uniform temperature field distribution within the pyroelectric crystal. We also illustrate and discuss the possibility of thermal or electrical interference (crosstalk) between the elements in a linear array when exposed to radiation. We discuss the importance of the optimal choice of the modulation frequency directly related to the achievable bandwidth of the envelope, the overall choice of the signal detection scheme and the implications for the calibration of the PED array for use in a Tomography context.

Keywords Pyroelectric detectors, PED, pulsed response, modelling