Electromagnetically induced grating and parity-time symmetry in coupled quantum wells

An asymmetric coupled three well system has been shown to exhibit PT-symmetry and electromagnetically induced grating (EIG), owing to electromagnetic induced transparency under the application of standing wave control and pump fields. The detuning of the probe and the uniform amplitudes of the standing wave control and pump fields could be used to tune the PT-symmetry. The probe beam is asymmetrically diffracted by the EIG either in positive or negative diffraction angles owing to the PT symmetry. The angle of diffraction can be controlled by the interaction length, probe detuning, and the uniform amplitudes of the standing wave control and pump fields.