Spatial Modulation of Electromagnetically Induced Transparency in Quantum Wells Using Monolayer Growth Islands

In this paper, quantum interference effects and atomically flat monolayer thickness fluctuations (growth islands) have been used in quantum well (QW) structures to propose a method to spatially modulate their refractive indexes and absorption/gain. The interference effects are caused by an infrared (IR) laser field, near resonantly driving the conduction intersubband transitions of an n-doped QW. The growth islands, on the other hand, laterally modulate these effects along the QW plane. It is shown that, when such a QW structure is properly designed, one can utilize these features to generate submicrometer regions (isles) of electromagnetically induced transparency (EIT) in the plane of the QW. This process occurs as the refractive indexes of these regions are coherently enhanced. The same laser field, in other regions of this plane, generates a large amount of gain or absorption with smaller refractive indexes. It is also shown that by varying the intensity and wavelength of the IR laser, one can dynamically switch over the EIT process from the lateral regions associated with a specific type of growth islands to other regions associated with either different types of islands or the nominal region of the QW. In the absence of this laser, such submicrometer-scale photonic structures do not exist, and the QW is transparent with a laterally uniform refractive index. These results can introduce a new trend for the generation of active photonic lattices, planar integrated optical circuits, and active photonic nanostructures