Linear and Nonlinear Optical Responses in Double Quantum Wells with Field Induced Quantum Coherence and Interference

New results of quantum coherence and interference effects in linear and nonlinear optical responses in double quantum wells are presented. Three-subband model in which two upper tunneling-split subbands are coupled by a dc-field is studied. We show the importance of the dc-field in establishing the quantum coherence and interference which introduces into the lasing without inversion and enhances the optical nonlinearity in the system. The optimal threshold dc-field can achieve as low as 4 kV/cm in our model. The Coulomb renormalization of electron kinetic energy is included. The many-body theory is employed to calculate both the linear and nonlinear optical responses.

The Dressed State Picture in Quantum Coherence and Interference

We investigate the advantageous description of driven multi-level systems in the dressed state representation. A demonstration is given for the cases of subnatural line narrowing and lasing without inversion.