Transformation of Bessel Beams in <Emphasis Type="Italic">C</Emphasis>-Cuts of Uniaxial Crystals by Varying the Emission Source Wavelength

We investigate experimentally the transformation of zero-order Bessel beams to a second-order Bessel eam in a c-cut of a CaCO₃ crystal. We show that the output-beam shape can be controlled by varying the emission-source wavelength and using a diffractive axicon. Beams were converted nearly totally at a wavelength change of Δλ = 1.5 nm and an initial wavelength λ = 637.5 nm of a CaCO₃ crystal, 15 mm in length, and a diffractive axicon with a period of 2 μm. We estimate the required wavelength variation Δλ = 1.7 nm, which is consistent with the experimental results.