Collective Excitations in Bose
A. Mysyrowicz, Daniele Hulin, A. Antonetti +6 more
us with the opportunity to address the specific issue of the role of intervalence band coherences. Figure 2 shows the observed coherently coupled lh-exciton Stark shift together with the conventional hh-exciton Stark shift measured with 0’ and d probe pulses, respectively. Our theoretical analysis is based on a thirdorder expansion of the dynamics-controlled truncation formalism.1° Other than the restriction to 1s-excitons, no further approximations are made.” In Figure 3 we show results with and without intervalence band coherences. In the limit of large detunings, the semiconductor response approaches that of a three-level system, in which case the coherently-coupled lh-exciton Stark shift vanishes in the absence of the Raman coherence. Clearly, the experimental observations can only be understood in the presence of the Raman coherence. The fact that the observed hhlh shift ratio increases at small detunings can be attributed to and simulated with the assumption of an optically induced decay of the Raman coherence, which is likely to be most effective at smaller than at large detunings. We acknowledge support by NSF, JSOP and COEDIP.
•Jan 1, 2001•0 citations