We report on the reduction of the operating voltage of a GaAs/AlGaAs multiple-quantum-well asymmetric Fabry-Perot modulator to approximately 4.2 V for a high-contrast (approximately 15 dB), low-insertion-loss (approximately 3 dB) device. This improvement on modulator performance makes the device suitable for a practical system and has been accomplished by an increase of the front reflectivity to approximately 43%. We discuss general design issues and show that the higher finesse cavity does not have to lead to low fabrication and environmental tolerances.