Terahertz optical gain based on intersubband transitions in optically pumped semiconductor quantum wells: Coherent pump-probe interactions

Optically pumped semiconductor quantum wells (QW) are investigated based on terahertz optical gain due to intersubband transitions. The pump-field-induced nonequilibrium distribution function is computed from a set of rate equations, including both intrasubband and intersubband relaxation processes, for each subband of the QW system. Terahertz optical gain is computed in a unified manner from pump-light-induced population inversion and stimulated Raman processes. This terahertz gain is significantly affected by the coherent pump and signal wave interactions.