solvent takes place the final result is a layer 2 having a uniform thickness of 200 nm u00b1 30 nm layer 2 is exposed to laser light the direction indicated by arrow 3 the laser light beam is pulsated modulated in conformity with the information to be recorded the efm eight out of fourteen modulation system being used the modulation system also forms the basis of cds compact discs the laser light beam according to arrow 3 issues from a semiconductor laser of the sharp lt 015 md type having an emission wavelength of 830 nm the laser has a power of 2 5 mw on the disc more in general 1 5 4 mw the laser light beam is focused to layer 2 by means of an objective not shown having a numerical aperture of 0 6 u00d7 0 4 as a result thereof the write spot diameter of the beam on the surface of layer 2 has an elliptical shape it is alternatively possible to use an objective having a numerical aperture of 0 5 in which case a circular read spot is obtained as a result of exposure to the modulated laser light beam information pits bits 4 are formed in layer 2 said pits are formed because in the exposed areas the laser light energy is absorbed by a dye sqs and converted into heat the temperature rises thereby causing the nitrocellulose binder to chemically decompose the decomposition reaction is exothermal so that additional energy is released the decomposition may even take.