Spin relaxation and all optical polarization switching at 1.52 micrometres in InGaAs(P)/InGaAsP multiple quantum wells

The spin relaxation times of electrons in InGaAs(P)/InGaAsP multiple quantum wells have been directly measured as a function of well width using an ultrashort pulse colour centre laser. The times measured range from 20 to 5 ps, considerably faster than previously determined in GaAs quantum wells. In addition, a fast, all-optical polarization switch based on a spin-sensitive optical nonlinearity is demonstrated at a wavelength of 1.52 mu m. This operating wavelength and the observed switch recovery time of 5.5 ps make it a potentially useful element for future all-optical soliton communication systems.