COHERENT ATOMIC EXCITATION IN A CAVITY .1. LOW-DENSITY

We present a procedure for treating coherent selective excitation (and subsequent ionization) of atomic vapour in a radiation-filled cavity. Specifically, we describe a technique for solving the coupled Maxwell–Bloch equations for atoms in a one-dimensional cavity by means of a spatial quasi- Fourier expansion that introduces a sequence of increasing spatial harmonics for atomic populations and coherences. We discuss the resulting coupled equations and present examples of solutions for a simple model of stationary and moving two-state atoms in the limit of very low density. The atomic excitation exhibits a travelling wave behaviour, but with significant modulation. These examples illustrate both the usefulness and the limitations of spatial quasi-Fourier expansion techniques. In particular, the examples presented here show the importance of retaining a succession of spatial harmonics when the excitation is coherent (as evidenced by Rabi oscillations). © 1990 Taylor & Francis Ltd.