How come you can get so much more information on a blue-ray than on a regular DVD?

Answer

Dear Anneleen,

“Thinner” isn’t really the right term. Actually you have to say that the wavelength of a blue laser is much shorter (namely 405nm or 0.000405mm) than that of a red laser used in a DVD player (650nm) or a CD player (780nm). You can read what a wavelength is correct at http://nl.wikipedia.org/wiki/Wavelength.

Information is stored on an optical carrier (Blu-ray, DVD, CD) by making small pits in the disc. To get more information on a disc of the same size, you have to make sure that you can make as many pits as possible, as close to each other as possible. Because a blue laser has a shorter wavelength, you can focus the beam much better and write much finer pits and therefore store much more information on a blue-ray disc than on a DVD. This is represented in the attached image.

How do you make a blue laser? Well, by an accumulation of very thin layers of semiconductor material. If the layers are neatly placed on top of each other and have the right thickness, it is possible to stimulate electrons in one of those layers to collectively emit (laser) light. The electronic properties of the materials used determine the wavelength of the laser light. These properties can more or less be set by choosing the right ‘mix’ of atoms.

I’ve added a few more interesting links, although some details are of course very technical. If I wasn’t completely clear or if you have any questions, don’t hesitate to ask!

Greetings,
Jurgen.