Ultrafast switching dynamics of Mach-Zehnder interferometer switches

We present results of cross-gain and cross-phase modulation experiments on InGaAsP-based semiconductor optical amplifiers and Mach-Zehnder interferome ter (MZI) switches. For 150-fs input pulses, we observe strong spectral and pulse shape distortions of the signal pulse, especially in the pulse overl ap regime. These pulse deteriorations are induced by subpicosecond gain and refractive index nonlinearities, In consequence, the ON-OFF ratio of the M ZI switch is drastically reduced for subpicosecond switching windows. In th e copropagation arrangement, the switching window with maximum transmission is shown to be limited to about 1.5 ps.