Spatial effects in nonlinear resonant reflection from the boundary of a dense semi-infinite two-level medium: Normal incidence

We study the nonlinear resonant reflection of an intense linearly polarized plane wave from a vacuum-dense two-level-medium interface under normal-incidence conditions. A domain of parameters is specially selected for which one needs to take into account strong atom-field coupling, which results in the appearance of a gap in the spectrum of mixed states (polaritons). For the linear problem, the presence of the gap causes a strong reflection of an incident signal with a frequency within the gap. The near-zone dipole-dipole interaction is also included within the framework of the local-field approach. By performing the time-domain analysis of the reflectivity at different spectral points, we observe certain peculiarities, such as the possibility of a steady-state high-contrast optical snitching with low-level operation, stable and unstable hysteresis loops, and an auto-oscillation regime of reflectivity for a certain range of the parameters driving the evolution of the system. (C) 1997 Optical Society of America.