Atom Trap Grabs Magnetic Atoms
A new trapping technique developed at NIST raises the possibility of using erbium and similar complex lanthanide elements for unique nanoscale magnetic field detectors, atomic resolution metrology, and optical and quantum computing systems.
Alexander E. Braun, Senior Editor -- Semiconductor International, 7/30/2008 9:00:00 AM
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| A laser beam slows erbium atoms (the purple beam traveling right to left) emerging from an oven at >1300°C in preparation for trapping and cooling. This capability to trap erbium atoms could lead to novel applications for semiconductors and metrology. (Source: NIST) |
Previously, the MOT technique had been applied to atoms that were barely magnetic and exhibited relatively simple energy structures that lent themselves to use in the cooling process. It was not until two years ago that a NIST group, led by principal investigator Jabez McClelland, demonstrated that far more complex atomic energy structures, such as that of strongly magnetic erbium, could also be manipulated for laser cooling.
The researchers heated erbium to >1300°C, creating an atom stream. The original MOT setup consisted of magnetic fields and six counter-propagating purple laser beams that were then used to cool and trap over one million atoms in a space ~100 µm in diameter. According to Andrew Berglund, a lead researcher at NIST, “This is an important step forward, because it might open a whole new range of applications. For example, cold trapped erbium might be used for producing single photons at wavelengths used in telecommunications.”
Another important application also being considered is the use of these trapped atoms to very precisely dope semiconductors and delicately tailor their properties, allowing the resulting devices to keep on track with Moore’s Law. “This is a major step toward the capability not just of capturing and cooling erbium atoms, but also manipulating them,” Berglund said. “This is an element with unique properties that could be used to produce extremely sensitive nanoscale force and magnetic sensors as well.”
Because a traditional MOT setup tends to become unstable in the presence of strongly magnetic atoms, such as erbium, the researchers turned the process upside down. “Instead of shifting the laser frequency toward the spectrum’s red end [to affect fast, high-temperature atoms more than the slower cold ones], we shifted it toward the blue side to take advantage of the magnetic fields on the highly magnetic erbium,” Berglund said. Magnetism holds the atoms stably trapped while the lasers gently push them — herding them like mavericks — against the field while extracting energy and cooling them to about two millionths of a degree above absolute zero. The technique developed by the team can cool and trap atoms by using only one laser beam instead of the usual six, considerably simplifying the procedure.
A new trapping technique developed at NIST raises the possibility of using erbium and similar complex lanthanide elements for unique nanoscale magnetic field detectors, atomic resolution metrology, and optical and quantum computing systems.
