vortexphotonics

[vortexphotonics]

Various manufacturers sell either custom optics or custom optical assemblies and structures, e.g., with extra-high precision or unique properties. Such solutions are often costlier compared with stock optics.

[vortexphotonics]

If you are interested in custom optical lenses, this is the ultimate guide short guide you need!

[vortexphotonics]

The Uses of Vortex Optical Components in Day-To-Day Tasks

An optical vortex is a single of a zero of an electromagnetic field; a position of zero degrees in which the propagation of electric and optical waves are stopped. The word is also used to define a straight beam of light which has such a zero degree in it. In other words, it is a position where light rays have no interaction with each other. It is like a light beam travelling along straight and parallel roads. The optical vortex describes the curve of a light wave as it propagates through a medium.

Let us see how this works on a simplified example, the so-called Bell experiment. The Bell experimented with the effect of a shock wave on the surface of an electric conductor, the thickness of which is determined. The theory of the Bell was that if the source is placed at a point, say a head, then a portion of the waves will be incident on the conductor and will create an induced impulse on the surface of the rod; this impulse will produce a variation in the thickness of the rod that is caused by the change in the angle of reflection and transmission. This deviation from the mean path of the electric field, due to the change in angle of transmission and reflection, produces a deviation from the zero degree of the field and the optical vortex phase plate.

This is how it works on a more complicated example; let us presume we take a spherical surface, say disc, as our spherical vortices. We can treat the disc as a collection of grains of different sizes which each can be deformed into a different shape, say a flat disc. Now assume that the number of grains n is constant. To get the vortex structure, we introduce a thin, flat disc as a collimating lens, letting it focus on the disc to form a virtual screen where the image n of the virtual screen can be seen on the surface of the disc. If we now change the focus of the lens and make it smaller, we have effectively introduced a modulation in the topology of the surface of the disc, which will alter the shape of the surface and thus produce a variation in the topological charge of the object.

Here is another way to understand the optical vortex. Assuming a two-dimensional disc as our sphere of operation, we can rotate the arrangement of the disc by hand, or by an electric motor (like the kind you see on television). Suppose we move the central area of the disc, say the area we determined earlier, to the right, and the peripheral areas to the left. We must also suppose that the inner and outer areas of the disc have different angular Momentum densities, which will result in a net change in the angular momentum of the system.

The simplest model for the generation of a vortex, assuming the non-rotating axis of symmetry, is the one-dimensional curve of constant helical beam profiles. The central region will radiate radial thrust into the neighboring regions, creating a net force inside the particle. Although the radial force may be complicated depending on the shapes of the shapes inside the system, this method is more accurate than the previous model because it takes into account the effects of tumbling.

Another example of how optical vortices can be used in practice is in the study of charged pairs of particles. In a situation where a pair of particles is charged at opposite poles, the two will come very close together if they are placed at the focus of an optical field. In this case, the momentum of the system is not conserved, but instead, the wave action produces an attractive curvature, just like in the earlier model for the production of helical waves. When the orientation of the charged particles changes, the wave-field comes into play, causing the electron to bump into the photons.

There are other uses for optical vortex, such as the application of ultrasound power. In this case, the momentum of the system, along with the strength and angle of modulation, are used to drive helical beams through fluid. For instance, ultrasound technicians use a machine to create an ultrasound beam that travels through a tube. Inside this tube are two hollow cylinders, one filled with water and the other with air. The air cylinder is filled with varying volumes of water, while the water cylinder has an inner ring of air that forms a tubular shape as it spirals around the outer ring.

When the inner ring of air and the outer ring of air to form a U shape, the result is an energy dipole moment, which can be measured in terms of the scattering of electromagnetic radiation. A dynamic holographic optical vortex device, which uses the principle of optical vortices, can measure the time it takes for this energy to reach the ends of the tubes. This information is important in designing materials such as lenses and membranes, as well as in manufacturing machinery for such things as printing presses. Without such measurements, manufacturers would know little about the materials they use in their day-to-day tasks.

[vortexphotonics]

The vortex lens, which is also known as a spiral phase plate or a vortex phase plate, transforms an incident Gaussian laser beam profile to a doughnut shaped beam profile or so colled optical vortex. Most important properties of a vortex lens are: accordance to the wavelength, topological charge and amout of steps. Our vortex lenses show a very small deviation from the theoretical height (usually ± 2nm), which leads to a high correspondence with the applicable laser wavelength. The topological charge effects the orbital momentum of the resulting doughnut beam. We cover topological charges in a range of 1 to 16 (higher topological charches are also possible). A higher amount of steps of a vortex lens result in a darker center region of the doughnut beam, this parameter is crucial for several applications of the vortex lens, such as STED and optical manipulations. Our vortex lenses posess 64 steps and we plan to build stepless spiral phase paltes in near future.

[vortexphotonics]

Phase plates with linearly shaped phase steps are commonly used as mode converters and allow to transform Laguerre-Gaussian Modes from TEM00 to higher modes TEM01, TEM11 etc. Such transformations are applied for example in the field of optical cavities and resonators, optical tweezers, atom and molecule excitation. Those phase plates have a physical step on the surface with a height corresponding to a phase shift of π/2. This difference in the optical path leads to a destructive interference in the step region and resulting zero intensity in the beam profile.