Parametric metasurfaces for amplified upconversion of electromagnetic waves

Spatiotemporal metasurfaces, characterized by dynamic variations in both space and time, enable functionalities unattainable with passive metasurfaces. In this study, we propose a concept of parametric metasurfaces capable of performing frequency upconversion and amplification of free-space electromagnetic waves. This functionality is realized through the modulation of variable capacitances embedded in specially designed dual split-ring resonators. We explore various combinations of the pump and incident wave frequencies and investigate different operational regimes of the proposed parametric system. Our theoretical analysis reveals high upconversion efficiency, with amplification levels exceeding 20 dB through a cascaded process, surpassing the limits set by the Manley–Rowe relations. Moreover, precise control over the phase of the upconverted waves is achieved by tuning the pump phase, paving the way for advanced manipulation of electromagnetic waves. This approach is applicable in the microwave and subterahertz ranges, with potential scalability to higher frequencies through ultrafast modulation techniques.