Physicists at the University of Bonn and the University of Kaiserslautern-Landau have conducted an experiment to create a one-dimensional gas out of light, enabling them to test theoretical predictions about this exotic state of matter for the first time. By concentrating photons in a confined space and cooling them simultaneously, the researchers were able to study quantum effects using this method. The results of the experiment were published in the journal “Nature Physics.”
In their experiment, the researchers filled a container with a dye solution and used a laser to excite the photons, which then bounced back and forth between reflective walls. When the photons collided with a dye molecule, they were cooled and eventually condensed into a photon gas. By modifying the surface of the reflective surfaces with microscopically small protrusions, the dimensionality of the gas could be influenced. This allowed the researchers to trap the photons in one or two dimensions and condense them, similar to how a wave is created in a narrow gutter.
Unlike in two dimensions where there is a precise temperature limit for condensation to occur, creating a one-dimensional gas caused thermal fluctuations that smeared out the condensation point. Although the properties of the system are governed by quantum physics, the phase transition in one-dimensional gases is not as precisely defined as in two-dimensional gases. The researchers were able to observe this behavior at the transition from a two-dimensional to a one-dimensional photon gas for the first time, shedding light on the unique characteristics of these systems.
By making small changes to the polymer structures on the reflective surfaces, the researchers can now investigate phenomena that occur at the transition between different dimensionalities in great detail. This basic research, funded by the European Research Council and the German Research Foundation, may open up new opportunities for exploring quantum optical effects in the future. The study involved collaboration between the IAP at the University of Bonn, the Fraunhofer Institute for Industrial Mathematics, and the University of Kaiserslautern-Landau, furthering our understanding of photon gases and their potential applications in quantum physics.