Measuring twist with light

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A device that uses light to measure torsion — the amount of twist — of an object at the nanometre scale improves on the sensitivity of previous techniques.

Measuring torsion is key to studies of a wide range of forces, from gravity to electromagnetism. John Davis at the University of Alberta in Edmonton, Canada, and his colleagues have built a torsion detector consisting of a pair of paddles placed next to an optical cavity. Because the paddles' refractive index is higher than that in the cavity, their movement distorts light waves that are trapped within it. By measuring this distortion, the researchers were able to detect subtle torsional shifts in the paddle's positions with roughly 100-times greater sensitivity than other techniques that do not use light.

The researchers suggest that the technique could be useful for studying magnetic materials at the nanoscale.

Appl. Phys. Lett. 102, 053102 (2013)

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