title: Circumventing the Manley-Rowe quantum efficiency limit in an optically pumped terahertz quantum-cascade amplifier.
abstract: Using a microscopic theory based on the Maxwell-semiconductor Bloch equations, we investigate the feasibility of an optically pumped electrically driven terahertz (THz) quantum-cascade laser as a pathway to room-temperature THz generation. In optical conversion schemes the power conversion efficiency is limited by the Manley-Rowe relation. We circumvent this constraint by incorporating an electrical bias in a four level intersubband scheme, thereby allowing coherent recovery of the optical pump energy. The observed THz radiation is generated through both stimulated emission and automatically phase-matched quantum coherence contributions--making the proposed approach both a promising source for THz radiation and a model system for quantum coherence effects such as lasing without inversion and electromagnetically induced transparency.
authors.affiliation: Sandia National Laboratories, Albuquerque, New Mexico 87185-1086, USA. iwaldmu@sandia.gov
authors.forename: Inès
authors.initials: I
authors.lastname: Waldmueller
authors.forename: Michael C
authors.initials: MC
authors.lastname: Wanke
authors.forename: Weng W
authors.initials: WW
authors.lastname: Chow