Abstract
We report on experimental measurements of transition strengths for spectral components associated with a driven two-level atom. The measurements involve time- and frequency-domain techniques and are performed in nuclear magnetic transitions of a nitrogen-vacancy colour centre in diamond using the optical Raman heterodyne method. The transition strengths are shown to depend on the characteristics of the driving field in a way readily accounted for by the dressed state formalism and the data provide an experimental confirmation of some elementary expressions frequently used for dressed states.