Silicon photonic add-drop filter based on a grating-assisted co-directionally coupled vertical hybrid structure.

Area of Science:

• Photonics
• Optical Engineering
• Materials Science

Background:

• Add-drop filters (ADFs) are crucial for dense wavelength-division multiplexing (DWDM) optical interconnections.
• Existing silicon photonic ADFs primarily use contra-directional coupling, with limited exploration of grating-assisted co-directional coupling (GACC).

Purpose of the Study:

• To report the first study of an ADF based on GACC in a vertical hybrid structure (VHS).
• To demonstrate a novel, easily fabricated ADF with performance comparable to existing technologies.

Main Methods:

• Designed and analyzed a GACC-based ADF utilizing a VHS with width-modulated silicon strip waveguides and a silicon nitride waveguide.
• Investigated the device's optical characteristics, including 3-dB bandwidth and grating length.
• Incorporated an optical phase change material for nonvolatile switchable functionality.

Main Results:

• Achieved a narrow 3-dB bandwidth of 1.16 nm and a short grating length of 1.13 mm.
• Demonstrated a nonvolatile switchable ADF with an extinction ratio exceeding 30 dB.
• The GACC-based ADF offers advantages in fabrication ease compared to contra-directional coupling ADFs.

Conclusions:

• The GACC-based ADF in a VHS is a viable and advantageous alternative for optical interconnections.
• This technology simplifies fabrication by avoiding close waveguide proximity and high-resolution lithography.
• The developed ADF is poised to be significant for DWDM optical interconnections.