Abstract

An ultrafast demultiplexer is important for achieving ultrahigh-speed time-division-multiplexed (TDM) transmission. Optoelectronic demultiplexers with photoconductive AND gates^1-3 have the advantages of being polarization free, small, and integratable with electronic devices. However, the operating speed and the contrast ratio between the on and off states of the AND gates have been restricted to 5 Gbit/s and 6 dB, respectively. This is due to severe signal leakage through switch capacitance (signal feedthrough) and to a long tail in the turn-off operation of photoconductive switches.² We describe a novel differential photoconductive AND gate that reduces the signal feedthrough. The and gate is fabricated by using low-temperature-grown Be-doped InGaAs/InAlAs multiple quantum well metal-semiconductor-metal PDs (MQW MSM-PDs) with a short carrier lifetime.⁴ Twenty-gigabit-per- second AND operation has been successfully achieved.

© 1995 Optical Society of America