Ultralong waveguide grating antenna enabled by evanescent field modulation.

Area of Science:

• Photonics
• Integrated Optics
• Nanophotonics

Background:

• Waveguide grating antennas (WGAs) are crucial for on-chip optical phased arrays.
• Achieving low divergence angles requires long WGAs (millimeters).
• High-index-contrast platforms like silicon-on-insulator (SOI) face challenges with feature sizes below 10 nm for long WGAs.

Purpose of the Study:

• To demonstrate a novel strategy for fabricating long WGAs on SOI platforms.
• To overcome the limitation of critical feature sizes below 10 nm.
• To enable the development of compact optical phased arrays with improved beam characteristics.

Main Methods:

• Proposed a new method involving periodic modulation of the evanescent field using subwavelength blocks.
• Implemented a single-etched waveguide grating antenna (WGA).
• Utilized a conventional 220 nm silicon-on-insulator (SOI) platform.

Main Results:

• Successfully fabricated a 1-mm-long WGA.
• Achieved a weak grating strength while maintaining a minimum feature size of 100 nm.
• Demonstrated a far-field divergence angle of 0.095°.
• Measured a wavelength scanning sensitivity of 0.168°/nm.

Conclusions:

• The proposed subwavelength block strategy is a viable method for implementing long WGAs on SOI.
• This approach overcomes fabrication challenges associated with sub-10 nm feature sizes.
• Enables the creation of high-performance on-chip optical phased arrays with narrow beam divergence.