Skip to Main Content
Summary form only given. Recently there has been considerable interest in ultrafast gain and refractive index nonlinearities in InGaAsP semiconductor amplifiers at wavelengths around 1.5 /spl mu/m. In particular, when an amplifier is biased at transparency such that a pulse propagating through it experiences no net gain or absorption, a large non-linearity having a recovery time of a few picoseconds has been measured. In this paper measurements of the transparency using the pump-probe method were compared to the optoelectronic signal method. Some discrepancies were observed and these are discussed together with the implications of the intensity-dependent transparency current for all-optical switching.