On-chip Y-junction with adaptive power splitting toward ultrabroad bandwidth

Area of Science:

• Photonics and Optical Communications
• Materials Science and Engineering
• Integrated Optics

Background:

• Silicon photonics are crucial for optical communication, but waveguide dispersion limits device bandwidth.
• Emerging 2-µm wavelength bands require components with broader operational ranges than traditional silicon photonics offer.
• Existing silicon photonic devices struggle to cover both the C-band and the 2-µm band due to dispersion.

Purpose of the Study:

• To introduce a novel topology-optimized Y-junction designed to counteract silicon waveguide dispersion.
• To demonstrate a Y-junction capable of adaptive power splitting over a wide spectral range.
• To enable silicon photonic components to operate across both the C-band and the emerging 2-µm wave band.

Main Methods:

• Utilized topology optimization to design a Y-junction with a specific shallow-etched trench feature.
• Fabricated the Y-junction with a compact footprint (3 µm × 1.64 µm).
• Characterized the device performance across the 1400 nm to 2200 nm spectral range, including C-band and 2-µm bands.

Main Results:

• The topology-optimized Y-junction effectively reverses detrimental dispersion effects.
• Achieved a 0.2-dB bandwidth exceeding 800 nm, covering 1400 nm to 2200 nm.
• Demonstrated a measured excess loss below 0.4 dB for the power splitter, confirming proof-of-concept viability.

Conclusions:

• The developed Y-junction offers a solution for broadband silicon photonic devices.
• The shallow-etched trench design enables adaptive splitting, crucial for future optical communication bands.
• This technology paves the way for silicon photonic components operating from the C-band to the 2-µm band.