Electric-field-induced refractive index changes in InGaAs-InAlAsasymmetric coupled quantum wells

Two kinds of InGaAs-InAlAs asymmetric coupled quantum wells (QW's) were numerically analyzed in an effort to enhance change in the refractive index (Δn) at longer wavelengths where absorption coefficient is small. The analysis reveals the operating voltage, Δn, chirp parameter, Δn/Δk, (Δk: change in the extinction coefficient) and figure of merit, Δn/α, (α: absorption coefficient) can be improved by these two kinds of the QW's. This improvement is caused by an abrupt electric-field-induced increase or decrease in the oscillator strength for the lowest heavy hole exciton