Quantum cascade laser with relaxation-stabilized injection

1. Field of the Invention An optical gain medium has first and second active layers and an injector layer interposed between the first and second active layers. The active layers have upper minibands and lower minibands. The injector layer has a miniband that transports charge carriers from the lower miniband of the first active layer to an excited state in the upper miniband of the second active layer in response to application of a voltage across the optical gain medium.