High-Dimensional Photonic Orbital-Angular-Momentum Frequency Interface

Frequency interface, namely, converting the colors of photons while retaining their other features, is indispensable for numerous applications ranging from up-conversion imaging to the multimode quantum network. However, limited by the nonuniform nonlinear frequency-conversion efficiency, constructing the frequency interface for high-dimensional spatial modes is still challenging. Here, to break this fundamen-tal barrier, we construct a high-dimensional (HD) orbital-angular-momentum (OAM) frequency interface via conducting sum-frequency generation between HD OAM states to be converted and a radial structured pump. Specifically, by replacing the conventional Gaussian pump with an optimized coherent superposi-tion of HD Laguerre-Gaussian radial modes (i.e., its azimuthal number is zero), we experimentally achieve the OAM frequency interface in nine dimensions with a record fidelity up to 90.38 %. Additionally, by increasing the number of radial modes, our scheme can be flexibly extended to higher dimension. Such a high-dimensional frequency interface could find potential applications in the high-capacity free-space optical communication and would also pave the way for constructing high-dimensional quantum networks.

Automated summary

Frequency interface is crucial for various applications, but constructing it for high-dimensional spatial modes is challenging due to the nonuniform nonlinear frequency-conversion efficiency. In this study, we propose a high-dimensional orbital-angular-momentum (OAM) frequency interface by conducting sum-frequency generation between HD OAM states and a radial structured pump. By replacing the conventional Gaussian pump with an optimized coherent superposition of HD Laguerre-Gaussian radial modes, we achieved the OAM frequency interface in nine dimensions with a fidelity up to 90.38%. This high-dimensional frequency interface could be used in free-space optical communication and high-dimensional quantum networks.