Generation of orbital angular momentum light based on mechanically induced long-period fiber gratings using 3D printing technique

Abstract

• An OAM beam generator was proposed with broadband and tunable operation wavelength. • OAM generation was achieved by employing 3D-printed mechanically induced few-mode fiber gratings. • By adjusting applied pressures and inclination angle of few-mode fibers, the operation wavelength can be tuned. • The operational bandwidth can be broadened by employing cascaded few-mode fiber gratings. We propose and experimentally demonstrate an orbital angular momentum (OAM) beam generation method based on mechanically induced few-mode fiber gratings fabricated using 3D printing technique. Experimental results indicate that the transmission depth at resonance wavelength of few-mode fiber gratings with axially uniform refractive index could be adjusted when different lateral pressures are applied onto the few-mode fibers, and hence mode coupling efficiency between the fundamental core mode and LP 11 mode could be controlled in this way. In addition, by changing the inclination angle of the few-mode fibers with respect to direction perpendicular to the mask grooves, the resonance wavelength of the few-mode grating could be changed as well. Besides uniform fiber gratings, we have also investigated the spectral broadening property of the few-mode cascaded fiber grating, and a 10-dB spectral bandwidth up to 114 nm is obtained experimentally. Our proposed OAM light generation method based on mechanically induced fiber gratings using 3D printing technique possesses several desirable merits such as low cost, ease of operation, flexibility in grating structure and no damage to fiber medium, which is anticipated to provide low lost and flexible solution to generation of broadband OAM light for future OAM-based communication systems.