The monolithic integration of a SiGe/Si rib waveguide modulator and multiple quantum well photodetector prepared by molecular beam epitaxy is achieved. The low dark current of 49.8 nA at -5 V reverse bias is measured and a modulation depth of 90% at 2.8 V modulation bias is obtained. The external quantum efficiency at λ=1.55μm is estimated to be 18.2%.

A symmetrical digital photonic splitting switch with a low insertion loss and a low driving voltage is developed using carrier injection in a silicon-germanium material for optical communication systems and networks at a wavelength of 1.55 μm. The switch structure has been improved based on a traditional 1×2 Y−shaped configuration by using two widened carrier injection regions. The switch has a threshold voltage of 1.0 V and a corresponding threshold current of 85 mA on one of the two output waveguide arms. The calculated driving current density is 5.7 kA/cm2 and the calculated power consumption is 85 mW at the 85 mA of threshold current. The measured insertion loss and the crosstalk are 5.2 dB and −9.6 dB, respectively, at driving voltage over 2V.