We study the issue of reflectivity in interactions of laser beams with condensed matter substrates. In particular, we discuss the effect that the reflectivity has on the melting of silicon. The theory of the laserhyphen;solid interaction expresses the properties of the hot zone that forms in the solid in terms of the beam parameters, such as the power and the spatial profile. The value of the reflectivity determines the actual value of the deposited power, and hence greatly influences the properties of the hot zone. The reflectivity is temperature dependent, and hence it constantly varies during the period in which the laser power rises to its maximum value. Therefore, a meaningful model is required in order to properly account for its effects. We have developed such a dynamical model for the reflectivity. The results of this model compare well with relevant experimental measurements.
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