Grating coupled infrared modulator at normal incidence based on intersubband transitions

An infrared modulator based on intersubband transitions in GaAs/AlGaAs quantum wells and working at normal incidence has been fabricated. The coupling is provided by a diffraction grating and the modulation is observed in the nondiffracted order transmitted by the modulator. Modulation depths are increased by a factor of 3 compared to the same structure used without grating at Brewster angle. The results are in excellent agreement with our calculations of near field diffraction in an anisotropic quantum well region. (C) 1997 American institute of Physics.