Quasi-periodic superradiant regime of femtosecond pulse generation in quantum-well and quantum-dot semiconductor

We propose a new type of accessible sources of ultrashort pulses based on the phenomenon of collective coherent recombination (superradiance) of electrons and holes in semiconductor heterostructures. We find and analyze a novel regime of an ultrafast operation of quantum-well or quantum-dot semiconductor lasers in which a quasiperiodic sequence of femtosecond superradiant pulses is emitted under quasi-stationary pumping. According to our calculations for AlGaAs-GaAs heterostructures, the coherent optical pulses of duration greater than or similar to 30 fs and peak intensity greater than or similar to 100 MW/cm(2) can be generated in a low-Q cavity of length similar to 10 - 30 mu m. It is shown that the santa process of femtosecond superradiant recombination can be used for the room-temperature generation of optical coherent emission in multiple quantum-well or quantum dot GeSi/Ge structures employing direct radiative transitions from the Gamma-valley.