Analytical aspects of electroabsorption modulators

The analytical aspects of a Franz-Keldysh electroabsorption modulator are presented for two geometries, one in which light is propagating in a waveguide junction (in particular a GaAs double heterostructure) and one in wihch light is transverse to the junction. Optimum transmission and electroabsorption attenuation of radiation through a double-heterostructure waveguide will occur for net donor concentrations 1015/cm3 or less. Electroabsorption light attenuation 20 dB or larger with reverse-bias voltages less than 10 V can be achieved. For net donor concentrations 1015 cm−3 or larger, large light attenuation in the transverse geometry can only occur under avalanche conditions within the junction.