Folded-Dipole Antenna Geometrical Analysis for THz Microbolometer

To improve the responsivity of terahertz (THz) antenna-coupled bolometer, heater (load) resistance has to be increased to suppress the thermal conduction and realize larger temperature rise of the thermistor. Proper design of antenna is therefore essential to assure the impedance matching between antenna and heater. From this viewpoint, a high-impedance folded-dipole antenna (FDA) has been studied numerically by the finite element simulation. The effect of FDA structural parameters such as number of arms, antenna width, and arm spacing are discussed with the lumped port and resistive heater coupled to the antenna gap for the cases of radiating and receiving modes, respectively. The product of resonant resistance and area efficiency is used to predict the improvement made by FDA as a figure of merit (FOM) correlated to the bolometer responsivity. This study revealed that the optimum FOM in FDA-coupled bolometer operating at 1 THz was obtained with three arms, 1-
$\mu \text{m}$
antenna width and 4-
$\mu \text{m}$
arm spacing. A comparison was made with the result from a half-wave dipole antenna and revealed that FDA could enhance the bolometer responsivity by a factor of 15. This research demonstrated the effectiveness of the FDA to improve the performance of THz antenna-coupled bolometer for applications such as imaging for non-destructive inspection.