Analogous Optical Activity in Free Space Using a Single Pancharatnam–Berry Phase Element

It is commonly believed that optical activity (OA) is manifested mainly in chiral media, but rare in non‐chiral structures. Here, an analog of OA in free space is experimentally demonstrated by using a single liquid‐crystal Pancharatnam–Berry phase element (PBPE), for which the mechanism is highly consistent with that of the traditional OA. The specifically designed PBPE supports the direction‐dependent polarization rotation of a Bessel beam with controllable “rotatory power.” Such a polarization rotation can be revoked by another PBPE with the same structure. Unlike in a chiral medium, this scheme shows simultaneous realization of equivalent leverotation and dextorotation merely by switching the optical element orientation, promising for applications non‐magnetic optical devices such as optical isolators. An analog of optical activity is demonstrated in free space by using liquid‐crystal Pancharatnam–Berry‐phase plates, which supports the direction‐dependent polarization rotation (leverotation and dextorotation) of a Bessel beam with controllable “rotatory power.” Such a polarization rotation can be revoked by another plate with the same structure, promising for applications non‐magnetic optical devices such as optical isolators.