Ultrashort and efficient adiabatic waveguide taper based on thin flat focusing lenses

Area of Science:

• Photonics
• Nanotechnology
• Optical Engineering

Background:

• Waveguide structures are crucial for integrated photonics.
• Achieving efficient light manipulation and coupling in compact devices remains a challenge.
• Traditional tapers for waveguide width conversion are often too long for dense integration.

Purpose of the Study:

• To introduce a novel flat lens structure for plane wave focusing.
• To demonstrate an ultrashort grating coupler utilizing this flat lens.
• To enhance the integration capabilities of photonic integrated circuits.

Main Methods:

• Fabrication of a flat lens using silicon subwavelength slits with variable widths.
• Integration of the flat lens into a grating coupler design.
• Numerical simulation to evaluate focusing performance and transmission efficiency.

Main Results:

• The flat lens achieves effective plane wave focusing with high power gain.
• An ultrashort grating coupler (22.5-μm) was demonstrated, reducing length by 95% compared to traditional designs.
• Near-perfect numerical transmission (95.4%) was achieved in the communication band.

Conclusions:

• The proposed flat lens design enables efficient light focusing and ultrashort tapers.
• This technology significantly improves the integration density of photonic integrated circuits.
• It offers a viable solution for compact micro/nano optical devices.