Ultrafast 168 GHz 1.5 ps 1 fJ Symmetric-Mach-Zehnder-Type All-Optical Semiconductor Switch

We report on the ultrahigh-repetition all-optical switching of a semiconductor-optical-amplifier-based symmetric-Mach-Zehnder-type switch. Record high 168 GHz, 1.5-ps-wide, 10-dB-extinction switch windows were observed. This repetition rate is ten times higher than the semiconductor optical amplifier's cutoff frequency. The control optical pulse energy used was a record low 1 fJ (average power=170 µW). Clearly isolated 168 GHz components were also observed in the output pulses' optical spectrum, which was in contrast to the continuum-like spectrum of the input pulses.