Recently, a significant research milestone has been achieved and published in Physical Review Letters, a preeminent physics journal in the United States. This groundbreaking study, carried out by a collaborative team from Shanghai Jiao Tong University, Nanjing University, and the National University of Singapore, has proposed the development of chiral waveguides featuring Archimedean spiral cross-sections within photonic chips. For the first time, this innovation has realized a 'one-to-one correspondence' or 'synchronization' between the orbital angular momentum (OAM) and linear momentum of light.

This breakthrough effectively tackles the challenge of selective excitation, which arises from the degeneracy of positive and negative topological charge (±ℓ) modes in photonic chips. By leveraging chiral structures to break symmetry, the direction of light propagation now uniquely dictates the sign of its carried OAM. In the experiment, femtosecond laser direct writing technology was employed to fabricate these spiral waveguides. The results confirmed the high robustness of the system, generating ℓ=+1 vortices upon forward incidence and ℓ=-1 vortices upon backward incidence. The purity of the target mode reached an impressive 70–90%, while non-target modes were suppressed to below 5–10%.

This achievement paves the way for a novel platform in high-dimensional on-chip communication and quantum information processing. It fills a critical gap by exploring a new type of interaction, distinct from the well-known spin-momentum locking, in the field of chiral photonics.