X-ray detection using the quantum-well exciton nonlinearity

Two related schemes for detecting X-rays based on (1) the scattering and (2) the reflection of a pulsed optical probe beam by carriers produced by the absorption of a single energetic X-ray photon are described. The detection method is based on the strong carrier density dependence of the (complex) index of refraction of the exciton absorption lines in a GaAs/AlGaAs multiple-quantum-well structure. These schemes can be used to construct a class of very sensitive gated X-ray detectors with micron spatial resolution and temporal resolution in the 10-30-ps regime.