High-efficiency mid-infrared on-chip silicon grating couplers for perfectly vertical coupling

Area of Science:

• Photonics
• Integrated Optics
• Nanotechnology

Background:

• On-chip optical coupling is crucial for integrated photonic circuits.
• Minimizing backreflection and maximizing directionality are key challenges.

Purpose of the Study:

• To experimentally demonstrate novel on-chip gratings for vertical coupling.
• To achieve efficient and robust optical coupling at specific infrared wavelengths.

Main Methods:

• Design and fabrication of two on-chip gratings with anti-backreflection units and binary-approximated blazed structures.
• Utilizing a 500-nm thick silicon film with interleaved etched slots.
• Applying physical theoretical analysis for apodization and optimization.

Main Results:

• First experimental demonstration of vertical coupling gratings at 3350nm and 3550nm.
• Achieved predicted directionality of approximately 80% with strong backreflection elimination.
• Measured coupling efficiencies of -5.58 dB and -4.34 dB, with 3-dB bandwidths of 87 nm and 210 nm, respectively.

Conclusions:

• The developed gratings offer efficient and robust vertical coupling solutions for integrated photonics.
• The design approach enhances optimization reliability and fabrication robustness.
• Demonstrated gratings are suitable for applications requiring precise light manipulation at specific infrared wavelengths.