Adiabatic mode coupling between SiGe photonic devices and SOI waveguides

Area of Science:

• Photonics and Optical Engineering
• Semiconductor Device Physics
• Materials Science

Background:

• Efficient optical coupling is crucial for silicon-on-insulator (SOI) photonic devices.
• Germanium/silicon-germanium (Ge/SiGe) quantum wells are used in modulators.
• Adiabatic tapering is a common technique for mode matching between different waveguide structures.

Purpose of the Study:

• To investigate the coupling between SOI waveguides and Ge/SiGe quantum well modulators.
• To analyze the role of laterally tapered epitaxial layers in adiabatic optical coupling.
• To optimize taper profiles for reduced device length and improved performance.

Main Methods:

• Eigenmode expansion method was employed to model optical mode coupling.
• Analysis of laterally tapered Ge/SiGe structures for adiabatic coupling.
• Identification of critical width ranges and taper angles for optimal performance.

Main Results:

• A critical width range of 200-300 nm for the Ge/SiGe structure was identified for efficient coupling.
• Minimizing the taper angle within this critical width range is essential.
• Optimized taper profiles reduced adiabatic taper length from 250 μm to 40 μm for 1-μm-wide waveguides.

Conclusions:

• Optimized adiabatic tapers significantly enhance optical coupling efficiency between SOI waveguides and Ge/SiGe modulators.
• The findings provide a pathway to miniaturize photonic devices by reducing component lengths.
• This research contributes to the development of more compact and efficient integrated optical circuits.