en.Wedoany.com Reported - Researchers at the Faculty of Physics of Vilnius University in Lithuania have developed a theoretical model that enables the reshaping of laser beams carrying twist and polarization using only light, by "pre-programming" atoms. The study, conducted by master's student Dharma Prasetya Permana together with Dr. Mažena Mackoit-Sinkevičienė, Dr. Julius Ruseckas, and Dr. Hamid Reza Hamedi from the Institute of Theoretical Physics and Astronomy, opens new pathways for magnetic-free control of structured light in quantum technologies. The findings have been published in the journal Physical Review A.
The team's research focuses on optical vortices, a special type of light beam whose structure twists during propagation. Unlike material vortices, such as water swirling in a whirlpool, optical vortices are distortions in the wave structure of light, where the wavefront forms a helical shape. The light intensity at the beam's center drops to zero, leaving a small dark core whose size is determined by a quantity called the topological charge, which indicates the number of complete twists the wavefront makes around the beam axis. A topological charge of zero means no twist; increasing the charge makes the structure more pronounced, with higher charges resulting in tighter twists. Theoretically, the topological charge can take any integer value, positive or negative, making optical vortices attractive for encoding information, potentially creating up to ten thousand different states. Researchers have already begun using these light vortices to build advanced quantum communication channels. Unlike qubits, which only hold two states, optical vortices allow information to be encoded in higher-dimensional quantum states, known as qudits, thereby vastly increasing the amount of data carried by a single photon.
Light propagation involves two forms of manipulation: polarization and vorticity. Polarization describes the direction of wave oscillation, while vorticity describes the overall shape of the beam. When scientists combine these two concepts, they obtain vector vortices—beams that simultaneously possess a structured pattern and an oscillation mode. To manipulate vector vortices and use them for advanced information processing, the researchers studied how these beams interact with atomic gases, selecting a three-level atomic medium. The theoretical model developed by the researchers demonstrates how these atoms can be "pre-programmed" to modify the shape of optical vector vortices. When such light passes through the prepared atomic medium, the atoms respond in a highly structured manner, inheriting the light's spatial pattern and forming regions of strong absorption and near transparency. This establishes a feedback mechanism between light and matter: the light shapes the atomic response, and the atomic response reshapes the light. As the beam propagates, it transforms from a simple ring-shaped intensity distribution into a petal-like pattern, with light concentrated in several bright lobes arranged around a center, while the beam's polarization structure also evolves.
This study positions pre-programmed atoms as a powerful tool for manipulating light, with potential implications for quantum computing and high-density data transmission. Previously, controlling structured light in this way required complex and expensive external magnetic field equipment, limiting system integration. This method is entirely optical, eliminating the need for magnetic fields by using light itself to "program" the atoms, offering a more flexible and scalable way to control light-matter interactions. It lays the foundation for faster quantum processors, highly secure quantum communication networks, and extremely precise optical sensors.
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