To discover more about this new technology, please read on. DVD uses similar laser technology to CD, but several advances in technology have greatly increased the capacity and speed. This allows DVD-RAM drives to burn smaller, more tightly packed pits in tracks that are closer together. The next stage of DVD phase-change recording will use blue lasers, which have an even shorter wavelength than the red lasers. The laser beam focuses on them by shining at different intensities through a dual-focus hologram lens.
Access times are much faster as a result.
On an unwritten disc, the structure of the DVD surface is crystalline. During recording, a high-energy laser heats the recording layer and turns the crystal structure liquid. Because it cools very quickly, the structure does not re-crystallize and an amorphous recording mark is left. When the data is erased, the laser heats the recorded marks at a lower intensity and re-liquefies them. The cooling process takes place more slowly, allowing the recording surface to change back into a crystalline state.