Chemistry · the experiment
Mend the crystal
Crystals a few tens of micrometres wide, a microscope tip, a crack that disappears. Four questions, from beginner to expert, on what healing gives back to the crystal, and what it does not.
1 · Spot what the crack switches off
Beginner
At the crack in the resonator crystal, what disappears, then comes back after healing?
2 · Compare the two indentations
Under the same load, about 45 micronewtons, the diamond tip sinks 95 nanometres into the intact zone and 115 nanometres into the healed zone.
Intermediate
How much deeper does the tip sink into the healed zone?
3 · Explain the spread between the guides
Across six light-guiding crystals, cracked then healed, the healing efficiency ranges from 32% to 99%. It compares the guided light collected at the far end, before the crack and after healing.
Expert
Where does this spread mainly come from, according to the authors?
4 · Predict the modes of a thinner crystal
In these resonators, the top and bottom faces of the crystal act as mirrors. The crystal studied, 1.8 micrometres thick, shows resonances spaced 17.8 nanometres apart in wavelength.
Expert
What would that spacing become in a thinner crystal of the same compound?
Crystal mended
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