We propose and analyze a new type of plasmonic bow-tie nano-antenna based on fractal geometry with grid. The optical properties of the first-, second- and third-iteration of the proposed fractal nano-antennas including absorption spectra, gap enhancement, electric field distribution and charge density are numerically investigated by means of finite-difference time-domain (FDTD) method. We demonstrate the bonding and anti-bonding modes arising from the plasmon hybridization modes of the proposed fractal nano-antennas. Our simulation results show that these nano-antennas can be tuned by changing the refractive index of the surrounding medium or antenna thickness. We also observe a strong electric field hotspot inside the gap region as the fractal iteration increases. Accordingly, the gap enhancement of the third-iteration is achieved up to 144.5 v/m within the nano-antenna gap. We find that the proposed second- and third-iteration bow-tie fractal nano-antennas are good candidates for strong electric field localization and tunable broadband applications.

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