The authors report significantly improved performances of a symmetric self-electrooptic-effect device (S-SEED), with high on-off contrast ratio (>30:l) and large optical bistability loop widths ( Delta P=44%) at an applied bias of V/sub a/=0 V, i.e., with no power supply. The S-SEED is made of extremely shallow quantum wells (ESQWs) in an asymmetric Fabry-Perot (AFP) cavity structure. At V/sub a/=5 V Delta P increased by up to 95%, preserving the high contrast ratio. The reflectivity changes at V/sub a/=0 and 5 V were about 15% and 30%, respectively. These are believed to be the largest values ever reported for such structures. >