Design for beam splitting components employing silicon-on-insulator rib waveguide structures.

Area of Science:

• Photonics and Waveguide Technology
• Integrated Optics
• Semiconductor Device Fabrication

Background:

• Conventional beam splitting components often suffer from high excess loss and large footprints.
• Silicon-on-insulator (SOI) rib waveguides are widely used but can exhibit performance limitations due to mode field spreading.
• Improving the efficiency and miniaturization of optical splitters is crucial for advanced photonic integrated circuits.

Purpose of the Study:

• To introduce a new SOI rib waveguide design for enhanced beam splitting components.
• To reduce wave field dispersive tails in the slab section for better mode confinement.
• To improve the performance metrics of y-branches and multimode interference couplers (MMICs).

Main Methods:

• Fabrication of SOI rib waveguide structures with a deposited high-index thin-film layer in the rib section.
• Numerical simulation and experimental characterization of optical performance.
• Comparison of the new design with conventional rib waveguide structures.

Main Results:

• The new design significantly reduces excess loss: 0.43 dB for a 1x2 y-branch splitter (vs. 1.28 dB conventionally).
• For a 1x2 MMIC, excess loss is reduced to 0.064 dB (TE) and 0.046 dB (TM) with negligible non-uniformity.
• Conventional MMICs require dimensions >70 µm x 5650 µm for similar low excess loss, whereas the new design achieves this in 30 µm x 1040 µm.

Conclusions:

• The high-index thin-film layer effectively confines the mode field, enhancing beam splitter performance.
• The new design offers substantial improvements in excess loss and compactness for optical splitters.
• This advancement is beneficial for developing more efficient and smaller photonic integrated devices.