Tunable Infrared Semiconductor Lasers Based on Electromagnetically Induced Optical Defects

We propose tunable midinfrared laser systems based on dynamic formation of electromagnetically induced optical defect sites. Such defects occur in a waveguide structure having a uniformly corrugated quantum well structure in the absence of any structural defect or phase slip. In the absence of a control laser field, such a corrugated structure causes a uniform perturbation of refractive index along the waveguide. However, when a relatively small region of such a waveguide structure is illuminated from the side by the control laser field, electromagnetically induced transparency occurs in this region while its refractive index corrugation is removed. We also show that such a coherently induced defect can be dynamically moved along the waveguide structure by just steering the control laser beam to illuminate different locations. We utilize the fact that the phase associated with this defect site can be adjusted via changing the length of the illuminated region to present a tunable distributed feedback laser where its lasing wavelength can be continuously varied within the stop-band. We study the case where two coherently induced defect sites happen along the waveguide structure and discuss the impacts of illumination of the whole waveguide structure with the control laser field. We show that the latter can either make the waveguide coherently transparent by destroying its refractive index perturbation and stop-band, or generate a gain-without-inversion grating. Formation of such a grating allows the waveguide to act as a tunable partly gain-coupled distributed feedback laser.