Beam shaping for ultra-compact waveguide crossings on monolithic silicon photonics platform

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Silicon Photonics

Background:

• Waveguide crossings are essential components in integrated photonic circuits.
• Achieving high performance (low loss, low crosstalk) in compact footprints remains a challenge.

Purpose of the Study:

• To implement a beam shaping approach for high-performance waveguide crossings.
• To fabricate and characterize these devices on a commercial silicon photonics platform.

Main Methods:

• Utilized cosine tapers for beam shaping in waveguide crossings.
• Fabricated devices on the GLOBALFOUNDRIES 45 nm monolithic silicon photonics platform (45 CLO technology).
• Performed optical characterization including insertion loss and crosstalk measurements.

Main Results:

• Achieved compact device footprint (4.7µm×4.7µm).
• Demonstrated near wavelength independence (±0.035dB for 1260nm-1360nm).
• Obtained low insertion loss (∼0.2dB) and excellent crosstalk (-35dB).
• Measured insertion loss stability across eight chips (0.197±0.017dB at 1310nm).
• Results align with 3D finite-difference time-domain simulations.

Conclusions:

• The beam shaping approach effectively realizes high-performance waveguide crossings.
• The fabricated devices are suitable for integrated photonic applications due to their compact size and robust performance.
• The cosine taper design offers a stable and efficient solution for silicon photonics.