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Terahertz emission from semiconductor surfaces illuminated by femtosecond laser pulses

We describe the investigations on terahertz radiation emission from surfaces of several semiconductors illuminated by femtosecond Ti:sapphire laser pulses. This radiation is caused by numerous physical mechanisms, therefore in-deep analysis of its causes can give valuable information about the properties of the material. It is demonstrated that, e.g., in the case of InAs important contribution to the terahertz emission comes from the nonlinear-optical rectification effect induced by the electric field in the surface inversion layer, whereas in CdHgTe alloys this emission is solely caused by the photo-Dember effect. Femtosecond laser pulse absorption in Ge is accompanied by intense electron redistribution between different conduction band valleys. Efficient terahertz emission was, for the first time, observed also from femtosecond laser illuminated thin layers of CuInSe2.