Design of a compact cylindrical micro-lens for efficient out-coupling and collimation of THz radiation from a photoconductive antenna

A compact cylindrical micro-lens is designed for efficient out-coupling and collimation of THz radiation from a photoconductive THz antenna placed on the backside of a semiconductor substrate. The full radiation pattern of the 3D lens-antenna system is calculated rigorously by using the Green's Function Volume Integral Equation Method in a form that exploits cylindrical symmetry. The lens is designed for an optimum amount of radiation emitted in a useful range of directions relative to the total emission taking into account the Purcell effect and radiation trapped in the semiconductor slab.