Relating the chirp parameter to the number of quantum wells in GaAs/AlGaAs waveguide modulators

摘要

For wavelengths near the quantum well absorption edge it is found that fewer quantum wells favor ideal phase modulation in GaAs/AlGaAs waveguide modulators. This is due to the dominance of the linear electrohyphen;optic effect over quantum absorption effects in the separate confinement waveguide. For TE polarization, it is found that the chirp parameter varies from 1 to 10 at minus;5 V and lgr;=0.89 mgr;m in actual devices depending on the number of wells. The data fit estimates from theory. For TM polarization no dependence was observed as expected. For an integrated laser/phase modulator (with different absorption edges) a 4hyphen;well structure may be near optimum to maximize the modulation efficiency and to still have low laser threshold current.