Broadband nanostructured fiber mode convertors enabled by inverse design

Area of Science:

• Photonics and optical engineering
• Materials science

Background:

• Mode conversion in optical fibers is crucial for advanced optical communication systems.
• Existing methods for mode conversion often suffer from limited bandwidth, low purity, or complex fabrication.
• Nanophotonic fibers offer a potential platform for novel light manipulation functionalities.

Purpose of the Study:

• To propose and numerically validate novel nanostructured fiber devices for efficient mode conversion.
• To demonstrate high-purity mode conversion from the fundamental mode to higher-order modes (up to 3 orders).
• To achieve ultra-wideband operation for these mode converters.

Main Methods:

• Utilizing inverse design algorithms to optimize intra-fiber nanostructures.
• Designing nanophotonic fibers capable of converting between arbitrary fiber modes.
• Numerical validation of proposed device designs.

Main Results:

• Demonstrated high-purity conversion (up to 98%) from the fundamental mode to higher-order modes (LP and OAM).
• Achieved ultra-wide operation bandwidth exceeding 400 nm around telecom wavelengths.
• Validated designs suitable for fabrication via thermal drawing of assembled preforms.

Conclusions:

• Nanostructured fiber devices offer a promising solution for on-chip mode conversion.
• The demonstrated devices exhibit excellent performance in terms of purity and bandwidth.
• The proposed fabrication method facilitates mass production, enabling practical applications.