Characterization of metal-semiconductor point-contact diodes around 1.55 mu m for optical-fiber communications

GaSb point-contact diodes have been characterized around 1550 nm for the first time, and their sensitivity and mixing properties have been investigated. Beat signals between two optical carriers with frequency differences of up to 144 GHz have been observed using a 72-GHz Gunn microwave source to downconvert the beat frequency. This demonstrates that such diodes can be employed to analyze the spectrum of the ultrafast signals used in modern optical communications. We also studied GaSb-diode responsivity in the time domain, and we show that this device might, in principle, be used both as a phase comparator measuring the relative time-delay between two independent optical pulse trains and as an optical sampler