Georgia Tech Researchers Shrink Atomic Beam Collimators to Fit on a Fingertip

A commoner may think that an “atomic beam collimator” is similar to a phaser that fires mystical particles. It may not be a bad analogy to present a technology that has been miniaturized by scientists now, rendering it more possible to make it to handheld devices someday.

At present, atomic beam collimators are predominantly used in physics labs, shooting out atoms in a beam that creates strange quantum phenomena and possessing properties that could be useful in precision technologies. Scientists from the Georgia Institute of Technology have shrunk the size of the collimators from that of a small appliance to fit on a fingertip and intend to make the technology accessible to engineers who develop devices such as atomic accelerometers or clocks, a component found in smartphones.

A typical device you might make out of this is a next-generation gyroscope for a precision navigation system that is independent of GPS and can be used when you’re out of satellite range in a remote region or traveling in space.

Chandra Raman, Associate Professor, School of Physics, Georgia Institute of Technology.

Raman is also a co-principal investigator of the study. The Office of Navy Research funded the study. The scientists reported their outcomes in the Nature Communications journal on April 23^rd, 2019.

The study describes a collimator, discusses certain quantum potentials of atomic beams, and ways in which the miniature collimator format could help atomic beams shape newer generations of technology.

Pocket Atomic Shotgun

Collimated atomic beams have been around for decades. But currently, collimators must be large in order to be precise.

Chandra Raman, Associate Professor, School of Physics, Georgia Institute of Technology.

To start with, the atomic beam is radiated from a box full of atoms, usually rubidium atoms, heated to a vapor such that the atoms oscillate about erratically. When a tube taps into the box, random atoms that have the correct trajectory shoot into the tube similar to pellets that enter the barrel of a shotgun.

Similar to pellets that leave the shotgun, the atoms come out from the end of the tube, shooting fairly straight as well as with a random spray of atomic shot flying at skewed angles. In the case of an atomic beam, that spray generates signal noise, and the optimized collimator-on-a-chip removes a major portion of it to generate a highly precise, almost perfect parallel beam of atoms.

The beam is considerably more focused and pure compared to beams that emerge from current collimators. The scientists would also intend their collimator to allow experimental physicists to produce complex quantum states in a more convenient manner.

Unwavering Inertia Machine

However, more instantly, the collimator establishes Newtonian mechanics that could be tweaked for practical use.

The optimized beams are streams of unwavering inertia since, in contrast to a laser beam composed of massless photons, atoms have mass and thus inertia and momentum. This renders their beams prospectively perfect reference points in beam-driven gyroscopes that assist in tracking motion and variations in location.

Existing gyroscopes in GPS-free navigation devices are accurate in the short run but not the long run, indicating that they have to be replaced or recalibrated quite often, making them less convenient, for instance, on Mars or on the moon.

Conventional chip-scale instruments based on MEMS (microelectromechanical systems) technology suffer from drift over time from various stresses. To eliminate that drift, you need an absolutely stable mechanism. This atomic beam creates that kind of reference on a chip.

Farrokh Ayazi, Ken Byers Professor, School of Electrical and Computer Engineering, Georgia Institute of Technology.

Ayazi is also the co-principal investigator of the study.

Quantum Entanglement Beam

It is also possible to transform heat-excited atoms in a beam into Rydberg atoms, which offer a plethora of quantum properties.

Upon sufficiently energizing an atom, its outermost orbiting electron orbits out so far that the size of the atom increases. Since the outermost electron orbits very far with considerably more energy, it acts similar to the lone electron in a hydrogen atom, and the Rydberg atom behaves as if it had only a single proton.

“You can engineer certain kinds of multi-atom quantum entanglement by using Rydberg states because the atoms interact with each other much more strongly than two atoms in the ground state,” stated Raman.

“Rydberg atoms could also advance future sensor technologies because they’re sensitive to fluxes in force or in electronic fields smaller than an electron in scale,” stated Ayazi. “They could also be used in quantum information processing.”

Lithographed Silicon Grooves

The scientists developed an astonishingly simple method for making the new collimator, which might inspire manufacturers to use it: Extremely narrow, long channels were cut through a silicon wafer that ran parallel to its flat surface. The channels were similar to shotgun barrels lined up beside each other to emit an array of atomic beams.

Silicon is an extremely smooth material for the atoms to fly through and is also used in a number of prevalent microelectronic and computing technologies. This opens the way for integrating these technologies on a chip with the new miniature collimator. Lithography, which is applied for etching prevalent chip technology, was used to accurately cut the channels of the collimator.

The biggest innovation of the scientists considerably decreased the shotgun-like spray, that is, the signal noise. They formed an aligned cascade of three sets of parallel barrel arrays by slicing two gaps in the channels.

Atoms that fly at skewed angles are ejected out of the channels at the gaps; by contrast, those that fly fairly parallel in the first array of channels move on to the next one. This process gets repeated from the second into the third array of channels, providing the atomic beams of the new collimator with their excellent straightness.