A Narrow Spectrum Terahertz Emitter Based on Graphene Photoconductive Antenna

Many terahertz applications such as sensing, imaging, and spectroscopy require coherent terahertz (THz) sources. A basic Ti-Au dipole antenna on GaAs substrate is designed initially and it is enhanced into a photoconductive antenna for terahertz emission. A spectral width of 120 GHz is obtained from the emission spectrum. In order to compare the spectral characteristics, a graphene dipole antenna is designed on the same substrate. It is observed that graphene dipole yields a narrower spectral width of 70 GHz, due to its high Q factor. Spectral width of the graphene dipole antenna is further made narrow to 25 GHz, by incorporating a λ/4 stub on the stripline to produce a filtering operation. The antenna provides a directivity of 6.14 dBi with stub which shows an improvement of 0.3 dB when compared with an antenna without stub.