Highly compact polarization-independent grating coupler

Area of Science:

• Photonics and Optical Engineering
• Materials Science for Integrated Optics

Background:

• Grating couplers are essential for interfacing optical fibers with integrated photonic circuits.
• Achieving high efficiency and polarization independence in grating couplers remains a significant challenge.
• Existing designs often require complex structures or larger footprints.

Purpose of the Study:

• To design and demonstrate a compact, polarization-independent output grating coupler.
• To achieve high coupling efficiency across a broad wavelength range for silicon-on-insulator (SOI) platforms.
• To minimize polarization-dependent loss for robust optical communication systems.

Main Methods:

• Proposed a novel grating coupler design featuring T-shaped grooves.
• Fabricated the device on a silicon-on-insulator wafer with a 260nm top silicon layer.
• Characterized the output coupling efficiency and polarization-dependent loss across the 1480-1580nm wavelength range.

Main Results:

• Achieved output coupling efficiencies greater than 50% for both TE and TM modes within the 1480-1580nm range.
• Observed peak efficiencies of approximately 58% around 1550nm.
• Demonstrated polarization-dependent loss within 0.05dB for the 1510-1580nm range.

Conclusions:

• The proposed T-shaped groove grating coupler offers a compact and efficient solution for fiber-to-chip coupling.
• The device exhibits excellent polarization-independent performance, crucial for telecommunication applications.
• This design advances the development of practical silicon photonic integrated circuits.