Engineers at Oxford were doing research around getting the highest possible resolution from telescopes, and compensating for fluctuations in the atmosphere.
And this turns out to produce answers that also apply to focusing lasers on targets that are very small.
So marks as small as one-thousandth of a millimetre can be made 0.15mm below a diamond's surface in a trillionth of a second. The extremely high speed keeps the laser burst from heating up the stone.
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