Merging bands of polarization convertors by suppressing Fano resonance

Abstract

In this letter, we propose to extend the bandwidth of polarization conversion (PC) by merging the bands of different polarization converters. Intuitively, it is quite natural that the bands of two polarization converters be merged if they are close enough. Unfortunately, there is always a narrow band with low efficiency between the two bands, which results from Fano resonance. We establish a theoretical model to analyze the underlying mechanism of the Fano resonance. We find that the Fano resonance can be suppressed by reducing the resonant frequency of the converter operating at a higher frequency band. In this way, the anti-symmetric surface current can be eliminated and the two PC bands can be merged as a wide band. We designed, fabricated, and measured a prototype. Both the simulation and experimental results verify this method. This work provides an effective alternative to the design of wide-band or even ultra-wideband polarization converters.