We predict, on the basis of a model calculation, that Fano interference effects may be observed in type-II quantum-well structures resulting in pronounced nonreciprocal absorption and emission profiles and interference narrowing due to overlapping resonances.
Based on full quantum mechanical theory,physical mechanism is systematically analyzed for realization of optical gain without population inversion in type-Ⅱ semiconductor quantum well,as well as spectrum of coherent Fano states composed of Γ -valley in the well layer conduction band and X -valley in barrier layer conduction band.The effect of this physical mechanism on Fano quantum interference of optical absorption probabitity is presented,followed by description of the impact of spontaneous emisson resulted from Fano spectrum structure and quantum fluctuation in vacuum field on excited optical gain.The mechanism affords theoretical foundation for the development of semiconductor quantum well laser without population inversion.
Strong-field manipulation of autoionizing states is a crucial aspect of electronic quantum control. Recent measurements of the attosecond transient absorption spectrum of helium dressed by a few-cycle visible pulse [Ott et al., arXiv:1205.0519[physics.atom-ph] ] provide evidence of novel ultrafast resonant phenomena, namely, two-photon Rabi oscillations between doubly-excited states and the inversion of Fano profiles. Here we present the results of accurate \emph{ab-initio} calculations that agree with these observations and in addition predict that (i) inversion of Fano profiles is actually periodic in the coupling laser intensity and (ii) the supposedly dark 2p2 {1S} state also appears in the spectrum. Closer inspection of the experimental data confirms the latter prediction.