OPTIMIZATION OF OPTICAL WAVE-GUIDE MODULATORS BASED ON WANNIER-STARK LOCALIZATION - AN EXPERIMENTAL-STUDY

We present optical waveguide modulation results obtained using Wannier-Stark localization in InGaAs-InAlAs superlattices grown by molecular beam epitaxy on InP substrates. We show that our results are in good agreement with a previously reported wavefunction model. We experimentally investigate the modulation behavior as a function of the electroabsorptive superlattice thickness. For this purpose we introduce the extinction ratio per unit waveguide length and per unit electric field as a relevant figure of merit that is broadly applicable to any electroabsorptive waveguide modulator. We show that inhomogeneous broadening imposes an optimum thickness for the electroabsorptive superlattice. Using a 20 period 65 angstrom InGaAs-20 angstrom InAlAs superlattice located in the core of an optical waveguide, we obtain a 14 dB extinction ratio by applying a drive voltage as low as 0.6 V to a 320-mu-m long waveguide device operating at 1.57-mu-m incident light wavelength under TE-polarization mode.