3D shaped light beams
Arbitrary 3D shaped light beams
A classical light beam propagates along a straight line and does not bend unless in a medium of variable refractive index. It is well known that by modifying the wavefront in a certain manner, the light intensity can be turned into a certain shape. Examples are optical lenses or Fresnel Zone Plates for focusing an incident wave to a point at the focal plane. Another example are Airy beams  created by modifying the phase distribution of the wavefront into an Airy function resulting in a bending of the light intensity while propagating (figure 1). A further example is holography, where the phase of the wavefront passing through a hologram is changed to mimic the object wavefront, thus providing the illusion that the original object is present in space. However, all these known techniques allow for limited light modifications: focusing within a limited region in space (holography), shaping into a certain class of parametric curves along the optical axis, or bending described by a quadratic-dependent deflection (Airy beams).
I showed that light beam can be turned into an arbitrary three-dimensionally (3D) curved light beam (figure 2). To create an arbitrary 3D beam of intensity, the beam trajectory is represented as a sequence of closely packed individual point-like absorbers thus giving a 3D object, and a hologram of this 3D object is simulated. When such a hologram is illuminated, the object in form of 3D curve made of dark points is reconstructed. When the contrast of the hologram is inverted, the object in form of 3D curve made of bright points is reconstructed, thus creating a 3D curved light beam .
1. T. Latychevskaia, D. Schachtler, H. -W. Fink, Creating Airy beams employing a transmissive spatial light modulator, Appl. Opt. 55, (22), 6095–6101 (2016).
2. T. Latychevskaia, H.-W. Fink, Inverted Gabor holography principle for tailoring arbitrary shaped three-dimensional beams. Sci. Rep. 6, 26312 (2016).