Nonlinear regimes of coherent optical phonon generation in quantum wells under electric current pumping

We present an analysis of nonlinear regimes of the coherent optical phonon generation under the electron drift in quantum wells. The phonon and electron subsystems are treated self-consistently. This allows us to find the steady-state generation regimes with macroscopic populations of optical phonon modes and the electron transport controlled in part by the generated phonons. The generation regimes demonstrate a pronounced threshold character. At high electric fields above the threshold, practically single-mode generation occurs and the current-voltage characteristic is considerably changed. We demonstrate high efficiency generation of the coherent optical phonons by the electric current. The coherent macroscopic optical displacements and the amplitudes of oscillating electrostatic fields are evaluated. The proposed model based on the electron nonlinearities predicts a range of the pumping electric fields under which the steady state phonon generation is realized. Our results suggest that the phonon avalanche occurs beyond this field range.