Design of a Trench-Assisted Optical Fiber for Generating Bessel Beams With Different Shapes

We have designed a trench-assisted optical fiber that can generate Bessel beams with different shapes in the fundamental mode. The trench-assisted structure is nested by rings with different refractive indexes on the cross-section. The fundamental mode field properties of the trench-assisted fiber are analyzed by using the finite element method. For the wavelengths from 400 nm to 2500 nm, the fundamental modes appear as Bessel beams with different shapes. The zero-order Bessel beams exhibit at the longer wavelength region, and the higher-order Bessel beams show at the shorter wavelength region. The Bessel beams’ shape can also be adjusted by tuning the structure parameters on the cross-section of the designed trench-assisted fiber.