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03 Mar 2006
A new concave pyramidal mirror could provide an alternative method of trapping atoms.
Researchers in the UK have devised new micromachined concave pyramidal mirrors to hold atoms in magneto-optical traps (MOTs) and control their motion on atom chips. According to the team from Imperial College, London, and Southampton University, the mirrors could benefit MOEMS (micro-opto-electro-mechanical systems) and could also help the development of quantum computers. (Applied Physics Letters 88, 071116)
"The mirrors are created by etching along a crystal plane of the silicon wafer, making their surface almost atomically smooth," Michael Trupke, one of the lead researchers, told Optics.org. "The maximum size of each mirror is limited only by the thickness of the silicon wafer and we estimate that high-quality micro-mirrors of this type can be produced at sizes reaching down to a few microns."
Firstly, the team hollowed out the 30 micron concave square pyramids from the silicon substrate, using potassium hydroxide. Next, researchers spluttered a 100 nm layer of gold on the silicon surface to improve the pyramids' reflective properties and form a mirrored structure.
Once fabricated, the group assessed the the quality of the mirror by projecting a 1 mm diameter laser beam normal to the silicon surface onto the apex and four corners of the pyramid. The scientists then compared the pattern and the intensity of the resulting reflections with theoretical calculations.
In order to test the atom trapping potential of the pyramid, the researchers built macroscopic MOTs, since the 30 micron, gold-spluttered pyramid did not have the correct geometry for trapping atoms. The macroscopic model, with base length of 16.3 mm, coated with aluminium, successfully trapped a cloud of atoms.
In the microscopic version, the group anticipates using pyramids with a 200 micron base to develop MOTs that can collect as many as 1000 or as few as 1 atom. "Our goal is to reduce the number of atoms in each trap to one, so as to create large arrays of single atoms trapped in precisely defined positions," said Trupke. "This is of interest in the context of quantum information processing."
The Imperial team intends to integrate pyramidal micro-mirrors with such current-carrying wires to form an array of MOTs on an atom chip. Atom chips have micro-structured surfaces to control the state, position and temperature of atoms with, for example, current-carrying wires on silicon that create electric and magnetic fields.
Via quantum computing, the controlled manipulation of individual atoms on atom chips may one day lead to far greater computing power than today's conventional computers.
Author
Darius Nikbin is Science/Technology Reporter on Optics.org and Opto & Laser Europe magazine.
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