50-dB integratable self-aligned Stark-ladder electroabsorption waveguide modulator

A GaAs/AlGaAs-superlattice rib-waveguide optical modulator that was fabricated with a single mask and a self-aligned electrode is described. The modulators uses the Stark-ladder transitions in the 775-810-nm wavelength range. for which the GaAs substrate is opaque. A modulation of 25 dB and modulation slope of 17 dB/V-mm was achieved at 777 nm with a -2-V bias in a 2.2-mm-long waveguide. A 50-dB modulation was achieved near 785 nm for a 6.2-V applied bias. Incorporation of additional passive superlattices into the structure resulted in an unbiased planar-waveguide loss of 1 cm/sup -1/ or less for wavelengths longer than 795 nm, making this waveguide structure suitable for interconnect waveguides and device integration without further material regrowth or diffusion processing. >