Broadband high coupling efficiency edge coupler with low polarization-dependence on the silicon-nitride platform

Area of Science:

• Photonics and Optical Engineering
• Materials Science

Background:

• Edge couplers are critical components in photonic integrated circuits for coupling light between optical fibers and waveguides.
• Existing single-tip couplers often suffer from polarization-dependent losses and limited bandwidth, especially when used with high numerical aperture (NA) fibers.

Purpose of the Study:

• To design and demonstrate an ultra-broadband double-tip edge coupler with high and polarization-insensitive coupling efficiencies.
• To enable efficient light coupling for high NA fibers on a silicon nitride platform.

Main Methods:

• Utilized silicon nitride photonics platform for device fabrication.
• Employed advanced optical simulations to predict coupling performance.
• Conducted experimental measurements to validate simulated results across various wavelengths and polarizations.

Main Results:

• Achieved simulated coupling efficiencies above 90% for both TE and TM polarizations from 1000-2000 nm.
• Predicted ultra-high TE mode coupling efficiency (>95%) over a 760 nm bandwidth.
• Experimentally measured peak coupling efficiencies of 97.1% (double-tip) and 95.7% (single-tip).
• Demonstrated polarization insensitivity with >90% efficiency across 1450-1640 nm.
• Confirmed broad bandwidth with 94% efficiency at 1280 nm.

Conclusions:

• The double-tip edge coupler significantly outperforms conventional single-tip designs in terms of efficiency and bandwidth.
• The demonstrated polarization insensitivity and broad bandwidth make it suitable for demanding photonic applications.
• This technology offers a promising foundation for developing compact and efficient photonic devices.