Compact 90 degrees trench-based splitter for silicon-on-insulator rib waveguides

Area of Science:

• Photonics
• Integrated Optics
• Semiconductor Devices

Background:

• Silicon-on-insulator (SOI) technology is crucial for integrated photonic circuits.
• Waveguide splitters are fundamental components in optical signal processing.
• Miniaturization of optical components is a key challenge in photonic integration.

Purpose of the Study:

• To design and experimentally demonstrate ultra-compact 90-degree waveguide splitters on SOI.
• To investigate the impact of trench width and refractive index on splitter performance.
• To validate simulation results with experimental measurements.

Main Methods:

• Design of rib waveguide splitters utilizing high-aspect ratio trenches.
• Experimental fabrication and characterization of the splitters.
• Three-dimensional (3D) finite difference time domain (FDTD) simulations for optical performance analysis.
• Investigation using three trench fill materials: air (n=1.0), SU8 (n=1.57), and index matching fluid (n=1.733).

Main Results:

• Demonstration of 11 µm x 11 µm compact SOI rib waveguide splitters.
• Optical performance is sensitive to trench width and refractive index of the fill material.
• Good agreement observed between 3D FDTD simulations and experimental measurements.
• A splitting ratio of 49/51 (reflection/transmission) achieved with an 82nm wide, index fluid-filled trench.

Conclusions:

• Ultra-compact SOI waveguide splitters can be realized using narrow, high-aspect ratio trenches.
• The choice of trench fill material significantly influences splitter performance.
• The demonstrated devices show potential for advanced photonic integrated circuits.