Terahertz gain in optically excited biased semiconductor superlattices

Zhang, Aizhen; Wang, Dawei; Dignam, M. M.
April 2005
Applied Physics Letters;4/25/2005, Vol. 86 Issue 17, p171110
Academic Journal
We investigate the terahertz-driven dynamics of excitons in an undoped optically excited biased semiconductor superlattice, including exciton-LO phonon scattering. We calculate the THz gain spectrum for a 820 fs THz pulse when the superlattice is excited by a 590 fs optical pulse. The gain arises because, in contrast to the single-electron case, the excitonic Wannier-Stark ladder is asymmetric with respect to absorption and emission. We find that gain coefficients greater than 100 cm-1 can be achieved at excitation densities for which domain formation should not occur.


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