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We investigate the efficacy of boosting the nonlinear-optical response byusing novel systems such as those in an excited state or with a degenerateground state. By applying the Three Level Ansatz (TLA) and using theThomas-Reiche-Kuhn (TRK) sum rules as constraints, we find the electricpolarizability and first hyperpolarizability of excited state systems to bebounded, but larger than those derived for a system in the ground state. It isshown that a system with a degenerate ground state can have divergent intrinsicpolarizabilities and that such divergences are real and not relics of apathology in the perturbation theory. Furthermore, we demonstrate that thesedivergences only occur on time scales short compared to the relaxation time ofthe population difference to an equilibrium value. Such systems provide a wayto get ultra-large nonlinear optical response. We discuss examples of hugeenhancements in molecules and double quantum dots using a double quantum wellas a model.

Using excited states and degeneracies to enhance the electric polarizability and first hyperpolarizability