Toward compact high-efficiency grating couplers for visible wavelength photonics

Area of Science:

• Integrated photonics
• Optoelectronics
• Materials science

Background:

• Grating couplers are standard for silicon photonics but underperform at visible wavelengths in moderate index contrast platforms like silicon nitride.
• Index contrast directly impacts diffraction efficiency and coupler length, necessitating performance improvements.

Purpose of the Study:

• To enhance grating coupler performance at visible wavelengths for silicon nitride photonic integrated circuits.
• To develop methods for increasing diffraction efficiency and reducing the footprint of grating couplers.

Main Methods:

• Developed a dielectric grating design that utilizes multiple optical modes to boost output intensity.
• Engineered an embedded metal grating to increase refractive index contrast and enable a smaller on-chip size.

Main Results:

• Demonstrated experimental results for compact and efficient visible wavelength grating couplers.
• Achieved enhanced performance suitable for applications requiring small footprints and high efficiency.

Conclusions:

• The developed dielectric and embedded metal gratings offer a pathway to efficient visible wavelength photonic interconnects.
• These advancements are particularly relevant for space-constrained cryogenic deployments in quantum photonics.