Abstract

For noninteracting two-level systems, the spectral shift resulting from making the ro~ ta ting-wave approximation (RWA), known as the Bloch-Siegert shift, is negligible at optical frequencies. In dense collections of two-level atoms and in a two-band semiconductor model, the Bloch-like equations of motion incorporate a parameter ε that represents the strength of the dipole-dipole interaction or the coherent Coulombexchange effects. Here, we discuss the resonance fluorescence spectra of dense collections of two-level atoms and the two-band semiconductor model and demonstrate that spectral shifts resulting from making the rotating-wave approximation can be substantial.

© 1995 Optical Society of America