High‐Fidelity Frequency Converter in High‐Dimensional Spaces

Abstract High‐dimensional frequency converter provides an enticing promise for establishing frequency interfaces to connect various physical systems toward the next generation of high‐capacity optical communication. The constant pursuit of high fidelity accompanied by multi‐dimensional information coding is restricted by the inherent fundamental nature of the degrees of freedom. Here, a high‐dimensional frequency converter is theoretically proposed and experimentally demonstrated, which builds a high‐fidelity interface between near‐infrared and blue‐violet wavelength. The perfect Poincaré beam exploiting the mutual orthogonality and transverse structure‐invariance of perfect vortex beam, accesses high‐dimensional spaces from spatial amplitude, phase, and polarization, and realizes the fidelity above 99% for arbitrary Poincaré states. Additionally, the trans‐spectral multiplexing utilizing the radial degree of freedom endows a superior capability in further increasing the system capacity. This proof‐of‐principle demonstration represents a key step toward the lossless transmission between different frequency domains, and has great prospects for constructing high‐capacity optical communication networks.