Influence of optical interference on quantum well infrared photodetectors in a 45 deg waveguide geometry

Standing light waves caused by the interference of incident and reflected beams lead to a spatial modulation of the electromagnetic field within the active region of a quantum well infrared photodetector (QWIP). The optical excitation-determined by the electric field component perpendicular to the quantum well plane-is thus inhomogeneous, influencing the QWIP responsivity and its voltage dependence. The inhomogeneity can be suppressed by using mesa photodetectors where only half of the top contact is covered with metal.