A giant controllable gap in the optical spectrum of a semiconductor laser subject to intense feedback with rotated polarization

A semiconductor laser subject to delayed optical feedback is investigated in the limit of extremely intense feedback power. In a range of feedback polarization rotation angles the emission spectra of the laser reveal a giant gap with width of more than a terahertz. The position of the gap and its width are shown to be regulated by means of feedback polarization rotation angle. We demonstrate that a theoretical approach, based on carrier density grating induced potential, explains our experimental results.