Picosecond all-optical polarization switching in InGaAsP MQW's at 1.52 μm

An all-optical switch operating at a wavelength of 1.52 μm is demonstrated. The switch makes use of electron spin polarization in a multiple-quantum-well semiconductor structure. The polarization change of a signal beam was observed to recover with a time constant of 20 ps determined by the spin relaxation time.