Butterfly plasmon: a plasmon capable of diverse focus modulation

In this Letter, we propose a class of plasmon that exhibits properties such as autofocusing and self-bending. In a butterfly plasmon, several new dimensions of focus modulation are introduced. By adjusting its initial phase, the position, the length, the intensity, and the bending direction of the plasmonic focus can be precisely controlled, demonstrating a high degree of tunability. Additionally, the interference of two butterfly plasmons has been explored, proposing a new method for controlling the position of the interference focal spot. Finite-difference time-domain (FDTD) numerical solutions are employed to further validate the correctness of the theory.