AI-rewritten: This is a summary of an article from Phys.org, rewritten by AI (Qwen, running locally) to make it easier to read. The facts come from the original article – read it for the full story.

---

An international team of physicists has developed a new method to determine the precise color of laser light using a single rotating image. Led by Professor Sonja Franke-Arnold at the University of Glasgow, the researchers published their findings in the journal Optica. Their approach involves passing two types of laser beams through a gas of rubidium atoms held in a glass cell. One beam is a standard laser with uniform polarization, while the second uses structured light known as a vector beam, which has a ring-shaped intensity profile and changing polarization around the ring.

As the first beam travels through the rubidium atoms, it aligns them into a specific quantum state. This alignment affects how the atoms respond to the second beam traveling in the opposite direction. The interaction between the light and the atoms changes as the laser’s frequency shifts closer to or further from the atoms’ natural resonance. The team captures this effect by separating the emerging light into different polarization components and photographing it.

The resulting image displays bright ‘lobes’ of light around the ring shape. As the laser frequency changes, these lobes rotate around the ring and vary in brightness. Professor Franke-Arnold explained that atoms respond to light at very specific frequencies, a property used for absolute accuracy in atomic clocks. Currently, most frequency measurements read a single trace on a detector, but this new method uses an image containing far more information. A shift of one megahertz in frequency produced a rotation of almost six degrees in the image.

While less precise than current methods that detect changes down to the kilohertz level, the team is working to improve accuracy beyond the sub-megahertz level shown in their paper. The technique is also sensitive to magnetic field changes, which could lead to new magnetometers capable of mapping three-dimensional magnetic fields from a single image or creating storage media for quantum networks. Researchers note that normally spatial light patterns should not be affected by frequency or magnetic fields, but this correlation provides a powerful new tool for measurement.