Record low-power all-optical semiconductor switch operation at ultrafast repetition rates above the carrier cutoff frequency

The switch repetition-rate limit of all-optical semiconductor switches, for which the dynamic extinction ratio decreases with increasing repetition rate, is examined and overcome. The extinction ratio is improved by optimization of the interferometer phase bias, which has previously been set to pi. The extinction-ratio increase accompanies a drastic change in the output pulse spectrum. Both the output pulse profiles and the spectra, before and after optimization, are successfully reproduced by simulation. As a result, switch repetition of 42 GHz (2.5 times higher than the semiconductor-carrier cutoff frequency) is achieved by use of 5-ps, 1548-nm pump pulses. What are believed to be record low input pump-pulse energies of 750 aJ (peak power, 140microW) at 10 GHz and 6 fJ (1.1 mW) at 42 GHz are used.