Possibility of optical bistability due to resonant intersubband excitation in stepped modulation-doped quantum wells

Abstract

We propose the use of a novel doped, stepped semiconductor quantum well structure as an optical nonlinear element. The large nonlinearity results from the change of many-body effects on resonant excitation of electrons from the ground to the first excited subband. Self-consistent calculations showed that the intersubband energy separation can be increased by up to 7 meV on intense illumination, compared to 1 meV for a conventional, square quantum well. We estimate that optical switching at powers below 1 W are feasible in an optimized structure, with switching times of about 1 ps.