Orbital Angular Momentum Utilization in Electromagnetic Systems

In recent years, the exploitation of orbital angular momentum in electromagnetic waves has emerged as a potent avenue to expand the functional capacity of communication, imaging and sensing systems. Unlike spin angular momentum linked to polarisation, OAM arises from a helical phase front characterised by an integer topological charge. This additional degree of freedom enables multiplexing of orthogonal modes on a single carrier, promising significant increases in spectral efficiency. Methods to generate and manipulate OAM span from passive optical elements such as spiral phase plates and metasurfaces to active antenna arrays in the radio and millimetre-wave bands. Concurrently, advances in detection schemes, including holographic interfaces and plasmonic photodiodes, have facilitated precise discrimination of OAM states. Practical realisations have demonstrated enhanced wireless link capacity, non-diffractive beam propagation for long-range transmission and chip-scale photonic integration for on-chip communications. The global significance of these developments is reflected in their applicability to next-generation wireless networks, high-resolution microscopy and quantum information protocols, underpinned by a rapidly maturing toolkit of design, fabrication and measurement techniques.

Research from Nature Portfolio

Recent studies have demonstrated holographic plasmonic interfaces integrated into silicon photodiodes capable of selective detection of OAM states, enabling precise discrimination of topological charges in free-space beams. Further advances in millimetre-wave communications have produced dual-mode antennas that reliably generate and multiplex two coaxial OAM channels at 60 GHz with high isolation, pointing toward capacity enhancements in wireless links. Compact metasurface arrays of elliptical nanoholes have been designed to convert circular polarisation into cross-polarised vortex beams and to facilitate on-chip generation and measurement of OAM, promising integration into chip-scale photonic devices.

Orbital Angular Momentum Utilization in Electromagnetic Systems publication trend

The graph below shows the total number of articles in orbital angular momentum utilization in electromagnetic systems across all publications each year (not limited to Nature Index journals).

Technical terms

Orbital Angular Momentum (OAM): The component of angular momentum in an electromagnetic wave associated with its helical phase front and carrying quantised topological charge.

Topological charge: An integer indicating the number of 2π azimuthal phase rotations around the beam axis in an OAM mode.

Metasurface: A planar assembly of subwavelength scatterers designed to engineer abrupt phase, amplitude or polarisation transformations of incident electromagnetic waves.

Pancharatnam–Berry phase: A geometric phase acquired by a wave upon spatially varying the orientation of anisotropic elements, enabling spin-to-orbital angular momentum conversion.

References

1. Holographic detection of the orbital angular momentum of light with plasmonic photodiodes. Nature Communications (2012).
2. Multiplexed Millimeter Wave Communication with Dual Orbital Angular Momentum (OAM) Mode Antennas. Scientific Reports (2015).
3. Generation and detection of orbital angular momentum via metasurface. Scientific Reports (2016).
4. Encoding many channels on the same frequency through radio vorticity: first experimental test. New Journal of Physics (2012).
5. Phase-engineered metalenses to generate converging and non-diffractive vortex beam carrying orbital angular momentum in microwave region.. Optics Express (2018).
6. Achromatic electromagnetic metasurface for generating a vortex wave with orbital angular momentum (OAM).. Optics Express (2018).