SUPERLATTICE SURFACE-NORMAL ASYMMETRIC FABRY-PEROT REFLECTION MODULATORS - OPTICAL MODULATION AND SWITCHING

We have investigated surface-normal asymmetric Fabry-Perot reflection modulators based on the electroabsorption stemming from the effective absorption edge blue shift caused by Wannier-Stark localization in superlattices. Very large contrast ratios (> 100) in these normally off resonator-type modulators have been achieved although there is a tradeoff between contrast ratio and insertion loss because of the relatively low contrast ratios between high and low absorption. Due to the modulators' normally off characteristics at the Fabry-Perot resonance, they also exhibit negative differential photoconductivity. When the modulator is connected to a similar modulator or a simple photodiode the negative differential photo-conductance at resonance enables the modulator to operate as a self-electrooptic effect device (SEED) that shows clear bistable loops and also has very large on-off ratios at its output. Modulators and SEED's based on these kinds of resonators are very important for optical interconnection and photonic switching systems. In this paper, we will discuss the operating principle of these modulators and SEED's, their characteristics and their sensitivity to variations of operating wavelength, layer thickness and composition, and temperature.