A new breakthrough has allowed physicists to create a beam of atoms that behaves in the same way as a laser, and could theoretically last “forever”.
This could finally mean that the technology is on its way to practical application, although there are significant limitations that still apply.
However, this is a huge step forward for what is known as an “atomic laser” – a single wave beam made of atoms that could one day be used to test fundamental physical constants and micro-engineering technology.
The corn laser has been around for a minute. The first atomic laser was created by a team from MIT Physicists in 1996. The concept seems pretty simple: just as traditional light-based lasers consist of photons that move with their waves in sync, lasers made of atoms require their wave-like nature to align before they are mixed as a beam.
However, as with many things in science, it is easier to visualize concepts than to perceive. In the laser atom root is a state of matter called Bose-Einstein condenseror BEC.
BEC is generated by cloud cooling from bosons to just a fraction above absolute zero. At such low temperatures, the atoms sink to the lowest possible energy state without stopping completely.
When they reach these low energies, the quantum properties of the particles cannot interfere with each other; They get close enough to each other to cause some kind of interference, which results in a high-density cloud of atoms that behaves like a single “super atom” or matter wave.
However, BECs are a bit of a contradiction. It is very fragile. Even light can destroy BEC. Given that the atoms in BEC are Cooled by optical laserthis usually means that a BEC is ephemeral.
The atomic laser that scientists have been able to achieve so far has been pulsed, not versatile; It involves only one pulse being fired before a new BEC needs to be created.
In order to create a continuous BEC, a team of researchers at the University of Amsterdam in the Netherlands realized something needed to change.
“In previous experiments, the gradual cooling of the atoms was done in one place. In our setup, we decided to propagate the cooling steps not over time, but in space: We make the atoms move as they progress through successive cooling steps,” Physicist Florian Schreck explained.
“Eventually, the ultra-cold atoms get to the heart of the experiment, where they can be used to form coherent matter waves in the BEC. But while using these atoms, the new atoms are already on the way to replenishing the BEC. In this way, we can keep the process going – essentially to forever.”
This “heart of the experiment” is the trap that protects the BEC from light, a tank that can be continually replenished for the duration of the experiment.
However, protecting BEC from light from cooling lasers, while simple in theory, was again more difficult in practice. There were not only technical obstacles, but also bureaucratic and administrative obstacles.
“On moving to Amsterdam in 2013, we started with a leap of faith, borrowed money, an empty room, and a fully funded team of personal grants,” Physicist Chun Chia-chen said:who led the search.
“Six years later, in the early hours of Christmas morning 2019, the experiment was finally up to the mark. We had the idea of adding an extra laser beam to solve one last technical problem, and instantly every picture we took showed BEC, the first continuous wave BEC.”
Now that the first part of the continuous atom laser – the “continuous atom” part – has been achieved, the team said the next step is to maintain a steady atomic beam. They can achieve this by moving the atoms into an unconfined state, thus extracting a diffuse matter wave.
They said that they used strontium atoms, a popular choice for BECs, the possibility opening up exciting opportunities. Atomic interferometry with strontium BECs can be used, for example, to make investigations in relativity and quantum mechanics, or to detect gravitational waves.
“Our experiment is the material wave analogue of a continuous wave optical laser with fully reflective cavity mirrors,” The researchers wrote in their paper.
“This proof-of-principle demonstration provides a hitherto missing new piece of atom optics, enabling the construction of coherent continuous wave devices.”
The search was published in temper nature.
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