Mid-infrared phase modulation via Stark effect on intersubband transitions in GaAs/GaAlAs quantum wells

Mid-infrared (~10 μm) electrorefractive effects of intersubband transitions in step GaAs/GaAlAs quantum wells are experimentally analyzed. A method for studying infrared electrorefraction of a two-dimensional structure via the Stark effect is used. The anomalous dispersion is measured over the entire spectral range of the transition and is found to be consistent with the Kramers-Kronig relations in the case of a Lorentzian absorption shape. A solution of Maxwell´s equations in the multiquantum well structure is detailed and leads to a good agreement with experimental data. A standard interferometer and a lock-in technique allow a quasi-direct determination of phase and amplitude modulation with very good sensitivity. A theoretical approach based on a Lorentzian model and the solution of Maxwell´s equations for a multiple QW (quantum well) structure agreed well with the data