Split Bull’s Eye Antenna for High-Speed Photodetector in the Range of Visible to Mid-Infrared

Split bull’s eye (SBE) antenna was developed to efficiently concentrate electromagnetic energy into an ultra-small area, and thereby enhanced the responsivity of high-speed near-infrared photodetectors. Here, we extend the investigation over a wider spectral range, and analyze the enhancement mechanisms based on finite-difference time-domain simulations. The SBE antenna exhibits far greater transmission enhancement than bull’s eye antenna, especially at mid-infrared wavelengths, substantially due to the change in transmission mode from evanescent to propagating and also the induced Fabry–Perot resonances in the central slit. Our results illustrate the SBE antenna is a promising candidate for high-speed photodetection ranging from visible to mid-infrared.