Joe is right....
if u have studied mecanic like at did for years, u will know each material has his own cutspeed.
cutspeed depend of the tool ur use(Hardmetal, titanium,diamants,water spray(yes, yes, u can even cut with water under pressure)...), in this case a laser, the material u cut, and the cooling process(air, injected air, soap water,...).
if u "cut" ur dvd at the wrong speed, and u look ur dvd with a microscope, u will probably see that is is not cut, but ripped.
BTW, where can I find closeup pictures of DVD...????