Reviewed by Lexie CornerFeb 24 2025
Photonics researchers from Tampere University in Finland and Kastler-Brossel Laboratory in France have demonstrated that the long-known phenomenon of light self-imaging can be applied to cylindrical systems. This approach enables precise control over light’s structure, with potential applications in advanced optical communication. The study was published in Nature Photonics.
Illustration of the generalized self-imaging of light in angular position and the related orbital angular momentum, utilizing a ring-shaped optical fiber and phase masks. Image Credit: Matias Eriksson, Tampere University
In 1836, Henry F. Talbot observed a phenomenon in which light patterns naturally reappeared after a certain propagation distance without the use of lenses or imaging optics. This self-imaging effect is now known as the Talbot effect.
Researchers from the Experimental Quantum Optics Group at Tampere University and the Complex Media Optics Group at Kastler-Brossel Laboratory, École Normale Supérieure, investigated the application of the Talbot effect in cylindrical systems.
Exploring the Effect of Self-Imaging in Cylindrical Geometries
As light propagates through a ring-core fiber, it undergoes a self-imaging process in the angular domain.
As light enters the fiber at a specific angular position of the ring-like fiber core, it first spreads around the entire cylindrical core and then perfectly recombines to form the original field via the self-imaging process.
Matias Eriksson, Doctoral researcher and Study Lead Author, Tampere University
The self-imaging phenomenon in cylindrical geometries is not limited to angular positions. A related optical property, orbital angular momentum (OAM), enables light to rotate particles around the optical axis or cause them to orbit along a ring-like path. OAM also exhibits a similar interference effect.
Angular position and orbital angular momentum are complementary variables, meaning that precisely defining one results in increased uncertainty in the other.
For the first time in a single experiment, the research team combined orbital angular momentum with self-imaging in the angular domain, enabling precise control over the spatial structure of light. The study also examines the relationship between this effect and the time domain, demonstrating its potential application in optical communication.
Bridging Two Popular Fields in Optics
The concept of space-time duality in optics states that many phenomena observed in the spatial domain also have counterparts in the temporal structure of light.
According to this principle, a periodic train of optical pulses and its associated frequency comb—light consisting of discrete, uniformly spaced frequencies—undergo generalized self-imaging in time.
By demonstrating the relationship between angular position/orbital angular momentum and time/frequency, the researchers identify a new form of space-time duality.
This means that the physical phenomena observed in these two fields are broadly connected, and the processing techniques from one may be used for the other.
Jianqi Hu, Study Lead Author and Postdoc Fellow, Kastler Brossel Laboratory
Jianqi Hu is a researcher at École Polytechnique Fédérale de Lausanne, Switzerland.
Fundamental Effect Triggers Application in Optical Communication
The researchers also demonstrate a potential application for optical communication by utilizing their understanding of self-imaging and its advanced modulation capabilities.
As light enters the fiber at a specific angular position of the ring-like fiber core, it first spreads around the entire cylindrical core and then perfectly recombines to form the original field via the self-imaging process.
Matias Eriksson, Doctoral researcher and Study Lead Author, Tampere University
The study confirms that the theoretical potential for lossless and crosstalk-free operation at significantly higher data rates is achievable, which could substantially impact the future of optical telecommunications.
Journal Reference:
Hu, J., et al. (2025) Generalized angle–orbital angular momentum Talbot effect and modulo mode sorting. Nature Photonics. doi.org/10.1038/s41566-025-01622-3.