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As an extension of the Robinson-Trautman solutions of D = 4 general relativity, we investigate higher dimensional spacetimes which admit a hypersurface orthogonal, non-shearing and expanding geodesic null congruence. Einstein's field equations with an arbitrary cosmological constant and possibly an aligned pure radiation are fully integrated so that the complete family is presented in a closed explicit form. As a distinctive feature of higher dimensions, the transverse spatial part of the general line element must be a Riemannian Einstein space, but it is otherwise arbitrary. On the other hand, the remaining part of the metric is-perhaps surprisingly-not so rich as in the standard D = 4 case, and the corresponding Weyl tensor is necessarily of algebraic type D. While the general family contains (generalized) static Schwarzschild-Kottler-Tangherlini black holes and extensions of the Vaidya metric, there is no analogue of important solutions such as the C-metric.

We suggest several cascade lasing schemes: (1) cascade of laser transitions between atom (ion) excited levels when the lower laser level of one laser transition is simultaneously the upper laser level of another transition located below; (2) successive lasing, first, on ion transitions, then after ion recombination on atom transitions; (3) while using multicomponent mixtures, successive lasing on atoms (ions) of separate components. These possibilities are discussed in terms of specific lasers, some of which have been studied experimentally.