The transformation of the 0th order Bessel beam into the 2nd order Bessel vortex beam is experimentally investigated. A c-cut lithium niobate crystal with a thickness of 514μm was used to convert the beams. It is shown that for a diffractive axicon with a period of 3.5μm illuminated by semiconductor laser (λ=639 nm), the output beam is a 2nd order Bessel vortex beam. It is shown that for a diffractive axicon with a period of 4μm illuminated by heliumneon laser (λ=632.8 nm), the output beam is a superposition of Bessel beams of the 0th and 2nd orders. The experimental results are in good accordance with mathematical modeling.
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