Generating Bessel Beams with Different Shapes by the Designed Trench-assisted Optical Fiber

TLDR: In this paper , a trench-assisted optical fiber is designed to generate Bessel beams with different shapes by using finite element method and electromagnetic field theory, which can improve the synchronous scanning rate.

Abstract: We have designed a trench-assisted optical fiber which can generate Bessel beams with different shapes by using finite element method and electromagnetic field theory. The trench-assisted structure is nested by rings with different refractive indexes. In the designed optical fiber, the HE11 mode fields are calculated with wavelengths ranging from 400 nm to 1500 nm. At the shorter wavelength, more energy is concentrated in the high refractive index ring region. When the wavelength increases from 400 nm to 2500 nm, the energy ratio in the high refractive index ring decreases from 98.1 % to 46.75 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">%</sup> , and the higher-order Bessel beam is converted to zero-order Bessel beam. Furthermore, the Bessel beams' shape can also be adjusted by tuning the structure parameters on the cross-section of the designed trench-assisted fiber. Eventually, a trench-assisted 16- core fiber is designed to generate multiple Bessel beams, which is beneficial to improve the synchronous scanning rate.