Vertically integrated spot-size converter in AlGaAs-GaAs

Area of Science:

• Photonics and Optical Engineering
• Semiconductor Materials Science

Background:

• Monolithic photonic integration requires efficient coupling between different waveguide types.
• Existing methods for fiber-to-chip coupling can be complex and lossy.
• GaAs-based photonics are crucial for high-speed optical communication.

Purpose of the Study:

• To demonstrate a novel spot size converter (SSC) for monolithic photonic integration.
• To achieve efficient light coupling between a high refractive index contrast waveguide and a single-mode fiber.
• To validate the performance of the SSC at a wavelength of 850 nm on a GaAs substrate.

Main Methods:

• Design and fabrication of a dual-waveguide AlGaAs chip.
• Incorporation of a vertical spot size converter (SSC) to bridge two waveguide layers.
• Characterization of the SSC conversion efficiency for the TE mode at 850 nm.

Main Results:

• A dual-waveguide structure was successfully fabricated on a GaAs substrate.
• The spot size converter (SSC) achieved a conversion efficiency of 91% (-0.4 dB).
• Efficient coupling was demonstrated between upper and lower waveguide layers at 850 nm for the TE mode.

Conclusions:

• The demonstrated spot size converter (SSC) enables efficient monolithic photonic integration.
• The GaAs-based AlGaAs chip design facilitates effective fiber-to-chip coupling.
• This technology is promising for advancing high-performance optical communication systems.