Parametric instabilities of two kind of millimeter waves and multiplication of frequency in GaAs semiconductors

This paper deals, at first, with the non-linear parametric effects on both space charge and electromagnetic waves in GaAs semiconductors. If an extern al electric field is applied, at the critical field value, the mobility cha nges its sign and becomes negative, as a result, non-linear instabilities o f the interactions are obtained. At the optimal value of electric field, E- opt, all non-linear processes are very effectives. The second point is the multiplication of the wave frequency, which is also effective thanks to the non-linearity. This process is used for earring waves into millimeter rang e instead of generation process, which in this range is non-effective. The Multiplication effect is based on the using space charge waves.