Design and analysis of a serrate-shaped fractal photoconductive antenna for terahertz applications

This paper presents the design and development of a fractal photoconductive antenna for efficient terahertz generation and detection that can be useful for sensing and imaging applications. The performance of the proposed serrate Sierpinski gasket terahertz photoconductive antenna is improved by leveraging the benefits of fractal ('space-filling' and 'self-similar') geometry. The photoconductive antenna performance is investigated by varying the sub-wavelength features inside the serrate electrodes and the number of serrate teeth while keeping its shape and length fixed. Several time- and temperature-dependent parameters are investigated, including carrier density, gap conductance, photocurrent, bandwidth, and optical-to-terahertz conversion efficiency, depending on the input ultrafast laser, carrier mobility, and photoconductive antenna's dimensions. Also, the proposed fractal-shaped designs are reformed up to fourth order, achieving similar to 39.22% increase in terahertz radiated power, and a bandwidth of 11 THz as compared to the rectangular interdigitated photoconductive antenna. The results of different dimensions of serrate photoconductive antennas are compared among themselves and with previously published photoconductive antennas. It is observed that the proposed photoconductive antenna overcomes the limitations of conventional bow-tie and dipole photoconductive antennas.