Linear and nonlinear optical properties of Bragg and off-Bragg periodic quantum well structures

To study the intrinsic behavior of periodic quantum wells in linear and nonlinear experiments, the authors grew a series of multiple quantum well structures containing up to 200 85-angstrom thick In0.04Ga0.96As quantum wells embedded in GaAs barriers. The superradiant mode is responsible for special optical properties: Reflection measurements reveal the formation of a photonic bandgap, its width growing linearly with the number of quantum wells. Poor absorption accompanies this feature. Off-Bragg, all N normal modes become optically active, each characterized by its own radiative width and eigenenergy. Nonlinear measurements show poor luminescence at Bragg periodicity after excitation into the free electron-hole continuum.