Quantum Optics

In Chapter 13 we saw how the optical properties of a two-level system can be modified by the application of an additional strong coherent field. For example, the absorption of light by a two-level system depends on the strength and frequency of the driving field. Figure 13.5 showed that in certain frequency regions we can amplify a probe beam. We assumed in Chapter 13 that the coherent light beam was acting on the same optical transition as the weak probe beam. However, the atomic/molecular systems have many energy levels and we can take advantage of this to produce a variety of ways of controlling the optical properties. This would offer much more flexibility as different optical transitions would have different frequencies and hence one could use a variety of sources. In this chapter we present results for the optical properties of a multilevel system. We show that coherent control can make an opaque medium transparent. We also show that the dispersive properties, which are important for the linear and nonlinear propagation of light, can be manipulated by light fields [1–3].