It is well known that the spin angular momentum of light, and therefore that of photons, is directly related to their circular polaris ation. Naturally, for totally unpolarised light, polarisation is undefined and the spin vanishes. However, for nonparaxial light, the recently discovered transverse spin component, orthogonal to the main propagation direction, is largely independent of the polarisation state of the wave. Here we demonstrate, both theoretically and experimentally, that this transverse spin survives even in nonparaxial fields (e.g., focused or evanescent) generated from totally unpolarised paraxial light. This counterintuitive phenomenon is closely related to the fundamental difference between the meaning of ‘full depolarisation’ for 2D paraxial and 3D nonparaxial fields . Our results open an avenue for studies of spin-related phenomena and optical manipulation using unpolarised light.
Original languageEnglish
JournalNature Photonics
Early online date21 Dec 2020
Publication statusE-pub ahead of print - 21 Dec 2020


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