Multi-order orbital angular momentum mode generators based on integrated long-period fiber gratings

Area of Science:

• Photonics and Optical Engineering
• Fiber Optics Technology
• Laser Fabrication Techniques

Background:

• Orbital Angular Momentum (OAM) modes offer unique properties for advanced optical applications.
• Generating multi-channel and multi-order OAM modes efficiently remains a challenge.
• Few-mode fibers (FMF) are crucial for supporting OAM modes.

Purpose of the Study:

• To propose and demonstrate an integrated multi-channel, multi-order orbital angular momentum (OAM) mode generator.
• To utilize CO2 laser fabrication for creating long-period fiber gratings (LPFGs) on FMFs.
• To enable flexible control over OAM generation for diverse applications.

Main Methods:

• Fabrication of integrated long-period fiber gratings (LPFGs) on few-mode fibers (FMF) using a CO2 laser.
• Inscribing LPFGs on multiple surfaces of the FMF by controlled fiber rotation (e.g., 43 degrees).
• Adjusting the rotation angle to control the number of integrated LPFGs and grating period.

Main Results:

• Successfully integrated up to nine LPFGs on the FMF, enabling nine channels for first-order OAM mode conversion.
• Demonstrated flexible design of channel spacing by controlling the number of integrated LPFGs.
• Achieved simultaneous generation of multi-channel second-order and third-order OAM modes by selecting the grating period.

Conclusions:

• The proposed CO2 laser-based LPFG fabrication method provides a flexible approach for multi-channel OAM mode generation.
• The integrated LPFGs enable precise control over OAM order and channel count.
• This technology holds significant potential for optical communication multiplexing and OAM sensing systems.