Efficient Second Harmonic Generation With Polarization Conversion in Diode-Bridge-Assisted Chiral Structure

While most works focus on either second harmonic generation (SHG) or polarization conversion, only a few involve polarization-converted SHG. In this paper, we propose a different mechanism in realizing polarization-converted SHG. It is achieved by a diode-bridge-assisted chiral structure, in which the SHG is obtained by rectifying the oscillating currents using the diode bridge and the polarization conversion is obtained by the chiral structure. We explain the underlying mechanism and demonstrate the polarization-converted SHG with an atom design. In addition, we show that the realized polarization-converted SHG is efficient and nonreciprocal. The SHG efficiency is 0.87%, higher than that of other approaches. Furthermore, the mechanism can be expanded to achieve polarization-conserved SHG by simply rotating the SRR structure. The proposed mechanism for achieving polarization-converted SHG expands the toolkit of multifunctional metamaterials and may facilitate the development and application of unidirectional frequency conversion and transmission devices.