The interacting laser circle is a new laser pointer model that can be used to explore topological defects and disordered structures in seemingly unrelated systems. If the molten iron is cooled slowly, the spins of the electrons can gradually be aligned in the same direction, thereby generating a strong magnetic field. However, rapid cooling of the molten iron will produce magnetic domains arranged in all directions, known as “topological defects”. The universe cools quickly after the Big Bang, and a similar phenomenon may occur. In order to study the formation of topological defects without temperature control in the laboratory, Nir Davidson and colleagues at the Weizmann Institute in Israel have now developed an experimental model of interacting laser beams. The imaging of the laser intensity allows them to measure a series of parameters that are likely to form topological defects.
To create their experimental model, Davidson and his colleagues placed a disc containing 10 to 30 holes arranged in a circle in the laser cavity. This “mask” generates a set of laser beams, each of which emits from a different hole and leaks a portion of its light into its two adjacent laser beams, thereby interacting. These interactions cause the phase difference between the beams to change with time. The interaction is evolving very quickly, and the research team can only observe the final state by recording the generated laser intensity pattern.
This final state represents the combined effect of approximately 1,000 different laser longitudinal modes in the cavity. It is basically equivalent to 1000 independent experiments running at the same time, each independent experiment has a different initial phase relationship between the lasers. In many cases, the laser beam can quickly synchronize its phase, but for some initial phase relationship, the red laser pointer beam will be “stuck” with each laser beam away from its adjacent laser beam in a fixed phase state. The team showed that when ten lasers were used, the state of these topological defects was exactly eight.
The researchers measured the possibility of topological defects by analyzing the laser intensity pattern, such as changing the number of lasers and the power of the laser in the cavity. They found that as the laser power increased, the topological defects became larger and larger. The team explained the results through simulations, showing that when the laser power is high, the intensity change between the beams drops rapidly, and the low power is related to the slower intensity balance. They claim that a slower equilibrium is equivalent to a slower cooling rate, so the possibility of topological defects is low.