Axicon lens, also known as a rotationally symmetric prism, is a lens that features one conical surface and one plano surface. They are commonly used to create a beam with a Bessel intensity profile or a conical, non-diverging beam. When converting a collimated beam into a ring, the plano side of the axicon should face the collimated source.
One application of axicons is in telescopes, where the usual spherical objective is replaced by an axicon. Such a telescope can be simultaneously in focus for targets at distances from less than a meter to infinity, without making any adjustments. It can be used to simultaneously view two or more small sources placed along the line of sight.
Axicons can be used in laser eye surgery. Their ability to focus a laser beam into a ring is useful in surgery for smoothing and ablating corneal tissue. Using a combination of positive and negative axicons, the diameter of the ring of light can be adjusted to obtain the best performance.
Axicons are also used in optical trapping. The ring of light creates attractive and repulsive forces which can trap and hold microparticles and cells in the center of the ring.
Single axicons are usually used to generate an annular light distribution which is laterally constant along the optical axis over a certain range.
This special feature results from the generation of (non-diffracting) Bessel-like beams with properties mainly determined by the Axicon angle α.
There are two areas of interest for a variety of applications: a long range with an almost constant intensity distribution (a) and a ring-shaped distant field intensity distribution (b). The distance (a) depends on the angle α of the Axicon and the diameter (ØEP) of the incident beam. The diameter of the annular distant field intensity distribution (b) is proportional to the length l. The width of the ring is about half the diameter of the incident beam.
Fig 1: Diagram of Axicon and resulting Bessel Beam