Generation of terahertz electromagnetic pulses from quantum-well structures

Terahertz generation from semiconductor quantum-well structures pumped by a femtosecond optical pulse is studied. We propose a three-level model for the electrons and holes in the quantum wells. We then solve the coupled optical Bloch equations directly using a Runge-Kutta method and calculate the terahertz radiation field. We study optical rectification and quantum beats caused by charge oscillations in 1) a coupled quantum well in which quantum beats occur between two electron states of the coupled system and 2) a single-quantum-well structure in which quantum beats occur between light-hole and heavy-hole excitons. Our theoretical results agree very well with the experimentally measured terahertz data.<
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