Second Harmonic Generation in Microwave Regime

Second harmonic generation (SHG), a fundamental and widely-studied phenomenon in nonlinear optics, has attracted significant attention for its ability to convert fundamental frequencies into their second harmonics. While the dominant SHG research has been focused on the optical and infrared regimes, its investigation in the microwave range presents challenges due to the requirements of materials with higher nonlinear coefficients and high-power microwave sources. Here, we provide an overview of methods together with underlying mechanisms for SHG in microwave frequencies, and discuss prospects and insights into the future developments of SHG-based technologies. The discussions on both numerical analyses and experimental studies will offer guidance for further SHG research and communication advancements in microwave regime.