Generating superpositions of higher–order Bessel beams

Abstract

We report the first experimental generation of the superposition of higher-order Bessel beams, by means of a spatial light modulator (SLM) and a ring slit aperture. We present illuminating a ring slit aperture with light which has an azimuthal phase dependence, such that the field produced is a superposition of two or more higher-order Bessel beams. The experimentally produced fields are in good agreement with those calculated theoretically. The significance of these fields is that even though one is able to generate fields which carry zero orbital angular momentum, a rotation in the field's intensity profile as it propagates is observed.

Measuring the orbital angular momentum density for a superposition of Bessel beams

“…A HeNe laser (λ ~ 633 nm) was expanded through a 6× telescope and directed onto the liquid crystal display (LCD) of a SLM. The first SLM (denoted as LCD 1) was programmed to produce various superposition fields using the concept of Durnin's ring-slit [14], but implemented digitally [15].…”

Detecting Bessel beams

“…Such beams have been generated using annular ring-slits in the far field, 7,8 axicons in the near field, 9,10 as well as the digital equivalent of both. [11][12][13][14] These beams have been further explored by generating their superpositions, 15 and converting them into vector BG beams. An emerging area of research is optical communication with the spatial modes of light, where Bessel beams are also mooted to play a role.…”

Formation and propagation of Bessel beams: practical considerations

“…These techniques include the employment of axicon lenses [13,14], ring slit apertures [14,15], binary ring gratings [16], tandem systems with introduced controlled aberrations [17,18], and blazed holograms [19,20]. Additional refinements to Bessel beam axial intensity distributions can be achieved by employing a lens with controlled positive and negative spherical aberrations [21], by preceding an axicon with a negative lens [22], or by a computer-controlled diffractive optical element [23].…”