The improved performance of computer systems has been realized by downscaling the integrated circuit minimum feature sizes. However, interconnection through wires is becoming increasingly difficult such that the signal I/O rate cannot keep up with the growth of computational performance. Optical interconnects provide a promising solution to this on-chip interconnect bottleneck. To meet the energy requirement, a system with an off-chip laser and Si-compatible on-chip modulators and detectors appears to be the most probable approach. Among Si compatible modulators, Ge/SiGe quantum-confined Stark effect (QCSE) modulators are the best approach to meet both the speed and power targets. This thesis proposed and investigated a 3-dimensional (3D) taper design for Ge/SiGe quantum well waveguide modulators on a Si waveguide to improve the coupling efficiency between the Si bus waveguide and the SiGe devices. We showed by simulations the superiority of the 3D tapers for coupling due to its better maintenance of the fundamental mode. We then demonstrated the fabrication of 3D tapers through grayscale lithography using a Heidelberg Maskless Aligner. When comparing the performance of modulators coupled by 3D tapers and 2D tapers, we showed that 3D tapers can lead to a coupling enhancement by a factor of 4. These 3D tapers combined with the Ge/SiGe QCSE waveguide modulators pave the way to on-chip, integrated modulators and detectors for optical interconnects.