Fast recovery of excitonic absorption bleaching in tunneling Bi‐quantum well

Excitons in a quantum well of a semiconductor exhibit large optical nonlinearity. Therefore, a quantum well of a semiconductor is regarded as a key to realizing a device which can control light using light. However, the lifetime of excitons, which are generated optically, is several nanoseconds to several tens nanoseconds. Therefore, the nonlinear optical effect including absorption saturation continues for the lifetime of the excitons. To shorten the lifetime of the excitons without disturbing the optical nonlinearity, a new superlattice structure is proposed called the “tunneling bi‐quantum well.” This structure uses the tunneling effect and measures the absorption recovery time. As a result, it was found that in a tunneling bi‐quantum well in a GaAs/AlGaAs system with a barrier width of 1.7 nm, the absorption recovery time was as short as 1 ps.