Electron diffusion and harmonic generation in super-lattices

There are many works devoted to current harmonic generation in one-dimensional superlattices (SL) (Bass, Bulgakov, Tetervov, 1989; Feise, Citrin, 1999; Pavlovich, Epshtein, 1976; Romanov, Romanova, 2001; Romanov, Romanova, 2004).The second harmonic generation (SHG) occurs in presence of DC electric field or other cause breaking initial inversion symmetry. In present work, we investigate SHG in SL under presence of the carrier density gradient ( V n ) We show that the SH intensity can be comparable with that of the current fundamental harmonic in that case.