Submillimeter-length single-helix chiral grating in high-NA fiber for robust third-order OAM generation

Area of Science:

• Photonics and Optical Engineering
• Nanotechnology
• Materials Science

Background:

• Orbital angular momentum (OAM) generation is crucial for advanced optical communication and sensing.
• Existing fiber-based OAM generators often suffer from large footprints and low efficiencies.
• High-numerical-aperture single-mode fibers (HNA-SMFs) offer potential for miniaturized optical devices.

Purpose of the Study:

• To design and demonstrate a submillimeter-length chiral grating for efficient OAM mode generation.
• To investigate the mechanisms enabling enhanced coupling of higher azimuthal modes.
• To evaluate the device's performance and robustness for practical applications.

Main Methods:

• Fabrication of a single-helix chiral grating embedded in an HNA-SMF.
• Utilizing geometric perturbations and elasto-optic effects for mode coupling.
• Characterization of device length, resonance dip, conversion efficiency, and environmental responsivity.

Main Results:

• Achieved a submillimeter device length of 0.88 mm, the shortest reported for fiber grating OAM generators.
• Demonstrated high conversion efficiency of 99.8% with a resonance dip of -28 dB.
• Exhibited excellent robustness with low responsivities to torsion, strain, and temperature.

Conclusions:

• The developed submillimeter chiral grating is a highly efficient and compact OAM generator.
• Its robustness and performance make it suitable for OAM-based particle sensing and chiral compound manipulation.
• This technology represents a significant advancement in miniaturized OAM generation for specialized applications.