The wavelength of the laser light can be tuned to interfere only with u-235 and "excite" the molecules, raising their energy level.

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This is made possible by the fact that Blu-ray uses a 405nm laser to read its 0.1mm deep info layer, while HD DVD uses the same blue laser wavelength at the depth of 0.6mm.

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"It is not trivial to make the necessary amount of laser light at a specific wavelength, " Robicheaux said.

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To activate the altered neurons, they usually use a laser tuned to the proper wavelength and pipe the beam through a fiber-optic cable implanted in the brain tissue.

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In the case of Dr Sweeney's fibre laser, the beam will have a wavelength of 1.5 microns, making it part of the infra-red spectrum.

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The laser Mr Hansen uses emits light with a wavelength of 2, 940 nanometres, which is primarily absorbed by water.

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