Radiative coupling of excitons in ZnSe double quantum wells

The radiative coupling between heavy-hole excitons in ZnSe double quantum wells is investigated experimentally and theoretically. The double quantum wells have a distance of half or quarter the wavelength (λ/2, λ/4) of the light resonant to the excitonic transition. The exciton energy splitting is tuned via a quantum well thickness gradient to control the radiative coupling. While in the λ/2 case a superradiant mode is observed, in the λ/4 case an anti-splitting is found. The results are compared with theoretical predictions using transfer matrix calculations. The residual disorder-induced inhomogeneous broadening, which is smaller than the radiative broadening of a single quantum well, significantly reduces the radiative coupling effects