Synthetic space in photonics is of great interest and attracts many attentions recently, [Refer to the review article “Optica 5, 1396 (2018)”]. The internal degree of freedom of light, such as the frequency and the orbital angular momentum, has been individually suggested to generate an extra dimension in addition to spatial dimensions.

LEFT: 2D Synthetic space including the frequency and the orbital angular momentum axes of light; RIGHT: Topologically-protected edge states in synthetic space

Our work, for the first time, suggests a 2D synthetic space including the frequency and the orbital angular momentum axes of light simultaneously in a single optical cavity. Importantly, no spatial dimension is required to create the 2D synthetic space. In this synthetic space, we generate a 2D photonic gauge potential, which gives the effective magnetic field for light. The system hence exhibits non-reciprocal one-way edge states, and suggests a topologically-protected manipulation protocol for entangled photons. The synthetic space in a “0D” spatial structure involves multiple degrees of freedom of light, holds potential applications for quantum optical communications. The paper has been published in Physical Review Letters with the title “Photonic gauge potential in one cavity with synthetic frequency and orbital angular momentum dimensions”.

Link: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.083903