Design of Waveguide Integrated Ge-Quantum-Well Electro-Absorption Modulators

We present two designs for a waveguide Ge-quantum-well electro-absorption modulator. In our designs, the strip SOI waveguides are butt-coupled and evanescent-coupled to the modulator, respectively. The proposed Ge-quantum-well electro-absorption modulator is based on quantum-confined Stark effect (QCSE), having a 3-dB bandwidth above 50 GHz, as well as a low switching power (around 60 fJ/bit at 1435 nm). In the butt-coupled design, the optimized extinction ratio is up to 11.4 dB, while the insertion loss is only 6.74 dB. For the second one, which utilizes evanescent coupling, the extinction ratio and insertion loss are 9.18 dB and 6.72 dB, respectively.