Domain formation and self-sustained oscillations in quantum cascade lasers

We study oscillations in quantum cascade lasers due to traveling electric field domains, which are observed both in simulations and experiments. These oscillations occur in a range of negative differential resistance and we clarify the condition determining whether the boundary between domains of different electric field can become stationary.
Comment: 6 pages. Accepted manuscript for publication in The European Physical Journal B Topical issue: Non-Linear and Complex Dynamics in Semiconductors and Related Materials