Substrate optimization in multielement THz imaging systems

In the field of terahertz technologies (ν ~ 0.1 - 10 THz), much attention is paid to the design of uncooled efficient detectors, because of their potential importance for numerous applications in vision systems, spectroscopy, medicine, security, etc. The new generation of multielement focal plane arrays (FPA) will enable real-time imaging, increase an information capacity of the video system, reduce the scanning time and increase the reliability of the video system by eliminating mechanical scanning components. Silicon CMOS field-effect transistor FPA are one of the most promising elements for integrated imaging system design, due to the possibility of integral implementation of THz detection system with the matrix of readout integrated circuits (ROICs). It is desirable to use planar antennas due to their low cost and ease of manufacture. For imaging system, the sensitivity of elements in the array should be uniform, so the gain and the input impedance should be the same for all elements. One of the problems in the design of CMOS multi-element detectors based on FET is the heterogeneity of the element characteristics in matrix or linear arrays, even for small array with rather identical FET properties. As it might be expected for the finite-size substrate with high dielectric permittivity (ε_Si≈12), every antenna gain depends on the element position on the substrate. In the present work, we perform numerical simulation of the linear array of eight elements with modified bow-tie antennas on a finite-size substrate.