The recording mechanism of a so-called CD-Recordable is reported; the disc consists of a pregrooved polycarbonate substrate, a dye, a metal reflector and an overcoat. After recording, bumps on the pregrooved substrate and pits at the dye/metal interface are observed. A method to determine the complex refractive index of a dye is explained and it will be shown how to obtain both a high reflection and a high modulation. From optical and thermal calculations and from recording experiments it is shown that two threshold temperatures are involved, associated with the softening of polycarbonate at 170°C and with a transition of the dye at 265°C.

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Preparation, measurement, and calculation methods are discussed for the determination of the complex index of refraction, the layer thickness, and induced volume changes of thin layers (due to a phase change, for example). The principle of the calculation is fitting a curve in the reflectance-transmittance plane measured on a range of layer thicknesses, instead of fitting the reflectance and transmittance as a function of independently measured layer thicknesses. This general method is applied to thin films of GaSb and InSb, in which a laser-induced amorphous-to-crystalline transition can be used in optical recording. The information essential for optical recording applications is measured quickly by making use of a stepwise prepared layer thickness distribution, while the complex refractive index and the layer thicknesses can also be calculated unambiguously.