Optical precursors with tunneling-induced transparency in asymmetric quantum wells

Abstract

A scheme for separating optical precursors from a square-modulated laser pulse through an asymmetric double ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}$As/GaAs quantum-well structure via resonant tunneling is proposed. Destructive interference inhibits linear absorption, and a tunneling-induced transparency (TIT) window appears with normal dispersion, which delays the main pulse; then optical precursors are obtained. Due to resonant tunneling, constructive interference for nonlinear susceptibility is created. The enhanced dispersion in a narrow TIT window is about one order of magnitude larger than that of the linear case. In this case, the main pulse is much delayed and the precursor signals are easier to obtain. Moreover, the main pulse builds up due to the gain introduced by the enhanced cross-nonlinearity.