IMPACT OF AMPLIFIED SPONTANEOUS EMISSION ON CARRIER DENSITY FOR MEASUREMENT OF OPTICAL NONLINEARITIES IN GAAS/ALGAAS MULTIPLE-QUANTUM WELLS

Amplified spontaneous emission (ASE) affects the measurement of nonlinear optical properties in semiconductors through its reduction of the excess carrier density. When the optical excitation area is large, lateral ASE may reduce the carriers within a much shorter period of time than the normal carrier lifetime. The time-integrated surface photoluminescence may be used as a measure of the carrier density just after ASE is over, which is the carrier density experienced by a ns probe in ps pump experiments. When the excited carrier density is at 10(20) cm-3 surface ASE is also possible and observed, even with small spot sizes.