Generation of long-distance stably propagating Bessel beams

We put forward a new optical system, which is composed of an existing axicon doublet and a newly proposed amplitude filter. The axicon doublet consists of a positive axicon and a negative axicon with high and low refractive indices, respectively. The Bessel beam generated by the axicon doublet propagates as far as more than 200 meters, owing to a small refractive index difference between the double axicons. The newly proposed amplitude filter is used to flatten the axial intensity distribution. Numerical results calculated by the complete Rayleigh-Sommerfeld method demonstrate that the generated Bessel beam propagates stably within a very long axial range. The proposed optical system is expected to have practical applications in tracking far-distance moving targets.