Spin‐to‐Orbital Angular Momentum Conversion with Quasi‐Continuous Spatial Phase Response

Abstract Vortex beams carrying orbital angular momentum have captivated great interest in the past few decades due to the inspiring application potential in both optical and microwave fields. More recently, assisted by Pancharatnam–Berry (PB) phase‐based meta‐atom, achieving spin–orbit‐converter becomes an encouraging topic. Commonly, however, spin–orbital‐converters are based on discontinuous phase distribution, which inevitably deteriorates their overall performance. To overcome this difficulty, here a paradigm of spin–orbital‐converter made of spirally arranged metastrip that can produce quasi‐continuously rotated phase profile with high‐efficiency is simulated and experimentally demonstrated in microwave regime. Using dispersion engineering, a meta‐atom capable of exciting spoof surface plasmon polaritons mode is designed to achieve PB phases. The metastrip consisting of a series of identical meta‐atoms is arranged along a proposed Archimedean spiral to obtain the rotated phase distribution of 4π. Near‐field performances reveal that the vortex electric distribution with topological charges of l = ± 2 can be generated. Significantly, this effort provides a strategy of achieving spin‐to‐orbital angular momentum conversion with phase continuity that may find applications in the fields of holography and communication systems.