Optical mode conversion via modulated atomic samples

Atomic systems are appealing in large part for the tunability of their parameters, such as energy levels. In this talk, I explore the conversion of photons between optical modes of a twisted cavity enabled by spatiotemporal modulation of a cloud of ⁸⁷Rb atoms. This modulation is induced by a varying Stark shift which “carves out” an effective, rotating optic from the atomic cloud, coupling transverse modes of the twisted cavity. We observe conversion between angular momentum modes and achieve the maximum theoretical conversion efficiency, demonstrating the versatility of atomic samples and prospects for engineering couplings between arbitrary modes.