Modified bow-tie antenna with strong broadband field enhancement for RF photonic applications

We present a novel design of a subwavelength modified bow-tie antenna that is capable of generating strong broadband field enhancement in its extended feed gap. This modified bow-tie antenna is comprised of a conventional bow-tie antenna with capacitive extended bars attached to the apex points of the bow-tie. The feed gap between the two capacitive bars is separated with a deep subwavelength width for the generation of enhanced local electrical field. Three-dimensional finite element method model is utilized to systematically explore the properties of this antenna design. Through adjusting the bow-tie geometry and the substrate properties, the antenna structure is optimized with a central resonant frequency at 100 GHz. Highly enhanced electrical field is created between the extended bar under radio frequency (RF) illumination. With the optimized design, numerical simulations show that a uniform field enhancement of more than 200 through the entire feed gap with a bandwidth of 40 GHz can be achieved. The strongly enhanced RF field within the gap can be applied to directly modulate guided optical wave propagating in a waveguide embedded in the substrate underneath the feed gap. This work builds up a bridge between devices in the RF and optical frequency regimes that may find many potential applications in RF photonic devices and systems.