Abstract
We report the creation of white-light, achromatic Bessel beams using a spatial light modulator and a prism to compensate for the dispersion. Unlike the Bessel beam created by a refractive axicon, this achromatic beam has a radial wavevector and hence an intensity cross-section which is independent of wavelength. The technique also lends itself to the generation of higher order Bessel beams with an on-axis optical vortex and associated orbital angular momentum.
Highlights
Spatial light modulators (SLMs) are widely being used as diffractive optical components for the generation of exotic beams
We report the creation of white-light, achromatic Bessel beams using a spatial light modulator and a prism to compensate for the dispersion
The technique lends itself to the generation of higher order Bessel beams with an on-axis optical vortex and associated orbital angular momentum
Summary
Spatial light modulators (SLMs) are widely being used as diffractive optical components for the generation of exotic beams. R, the interference pattern is only maintained over the region for which the plane waves overlap This distance Zmax is set by a combination of the cone angle and beam aperture, and approximated by Z max ≈ R k0 kr , where kr is the radial component of the wavevector k0 = 2π λ and equates to a cone half-angle in the k -space distribution of plane waves of sin −1 (kr k0 ). The spacing between the rings and approximate size of the centre spot is given by λ 2kr These Bessel beams are frequently created using an optical element called an axicon, a circularly symmetric glass cone of refractive index n and exterior-angle α, giving a cone semi-angle for the interfering plane waves of (n −1)α = kr k0 , i.e. kr = α(n −1)k0. The refractive axicon produces a Bessel beam where both size of the centre spot and radii of surrounding rings are proportional to wavelength and if used with a white-light will produce a beam with wavelength independent Zmax but where the rings in particular are spectrally dispersed [11]
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