Electrooptic effects in GaAs-AlGaAs narrow coupled quantum wells

The linear and quadratic electrooptic coefficients in narrow single and strongly coupled GaAs-Al/sub x/Ga/sub 1-x/As quantum wells have been measured. The quadratic electrooptic effect is enhanced over that of conventional square quantum wells for both TE and TM polarization in all the structures considered, by up to six times in the case of 2-nm-wide GaAs-Al/sub 0.2/Ga/sub 0.8/As strongly coupled quantum wells. The origin of the enhanced quadratic electrooptic effect was found to correlate with a larger red shift in the absorption edge exciton and strong Coulombic coupling of the bound exciton states with the quasi-continua.