Novel schemes and prospects of superradiant lasing in heterostructures
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The phenomenon of collective recombination (superfluorescence or superradiance) of electrons and holes in semiconductor heterostructures of all possible dimensions, D = 0, 1, 2, 3 is analyzed. We show that, at the current level of technology, superradiant recombination can be realized most easily in quantum-well and quantum-dot laser structures and that it leads to the spontaneous generation of coherent radiation pulses whose duration is shorter than incoherent relaxation times. We analyze a novel superradiant regime for the ultrafast operation of heterolasers, in which a quasiperiodic sequence of femtosecond pulses is emitted under continuous pumping (injection or optical). According to our calculations for different types of semiconductor active media, coherent optical pulses with a duration up to 100 fs and an extreme peak intensity up to 100 MW/cm2 can be generated in a cavity of length 10 m, even at room temperature. On this basis, we propose a way to obtain ultrashort optical oscillations in semiconductor materials for which lasing was not realized or was characterized by very low quantum efficiency. In particular, lasing at 1.3-1.5 m direct transition in indirect band-gap GeSi/Ge heterostructures is especially promising for applications in optoelectronics and fiber optics. Various schemes and regimes of superradiant laser generation are discussed, and their prospects are outlined.