An atom laser flowing from top to bottom makes a "caustic" pattern like that made by light as it encounters an obstacle. Credit: Washington State University.
Cooled to almost absolute zero, atoms can move in waves like light and can be focused into shapes called caustics, similar to the reflecting patterns light makes on the bottom of a swimming pool or through a curved wine glass.
Scientists at Washington State University have developed a method to see caustic matter by placing obstacles in the path of a cold atom laser. The researchers describe the results in a paper for Nature Communications.
These caustics have the potential to be used for highly precise measurement or timing devices.
The paper's senior author, Peter Engels, said that it was a beautiful demonstration of how we can manipulate matter waves in a way that is very similar to how one would manipulate light. An atom is accelerated by gravity, so we can mimic effects that would be difficult to see with light. Since atoms respond to many different things, we can potentially exploit this for new types of sensors that are particularly good at detecting magnetic fields, electric fields or gravity.
To achieve these effects, the scientists had to create a place that was one of the lowest on Earth. The optical lasers were used to take energy out of the atomic cloud inside the vacuum chamber, which was very close to absolute zero.
The cold makes atoms behave in ways that are very different from nature's laws. The atoms move like waves in these conditions. The Bose-Einstein condensates are named after Albert Einstein and Satyendra Bose, the two physicists who first predicted the state of matter.
In the process of exploring these condensates, the researchers at the University of Washington created a cold atom laser, which means wave-like atoms started lining up in a column and moving together.
The paper's first author, Maren Mossman, is now the assistant professor at the University of Washington. The atoms are like one object. We decided to see what would happen if we poked this.
The researchers put optical obstacles in the way of the atom laser, shining specific wavelength of laser lights onto the atoms. One obstacle repelled the atoms and made caustics in downward fold shapes, while another attracted them to make caustics in upward shapes.
The system can be changed in a number of ways, the researchers said.
Caustics in atom lasers have never been studied with this flexibility.
The co-authors include Michael Forbes, an associate professor in the Department of Physics and Astronomy at Washington State University, and Thomas Bersano, a former post-doc at Los Alamos National Laboratory.
There is more information about caustics in an atom laser. There is a DOI titled " 10.1038/s41467-021-27555-3".
Nature Communications is a journal.
The atom laser creates reflective patterns similar to light.
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