Axicon Bessel Beam

Bessel beam features of an axicon.

Axicon bessel beam.

Axicon bessel beams are used in a variety of laser applications where the focus media is transparent at the laser wavelength. Although a true bessel beam would require an infinite amount of energy to create an axicon generates a close approximation with nearly non diffracting properties within the axicon s depth of focus dof. This is in contrast to the usual behavior of light which spreads out after being focused down to a small spot. An axicon also known as a rotationally symmetric prism is a lens that features one conical surface and one plano surface.

Bessel beams are also self healing meaning that the beam can be partially obstructed. The axicon is primarily used in the field of beam shaping and in various laser ap pli ca tions. One such field is laser glass cutting often done with single mode ultrashort pulse lasers in the ir and green wavelengths. A bessel beam is a wave whose amplitude is described by a bessel function of the first kind.

This special feature results from the generation of non diffracting bessel like beams with properties mainly determined by the axicon angle α. Unlike a gaussian beam which deteriorates over distance a bessel beam is non diffracting maintaining an unchanged transversal distribution as it propagates. This means that as it propagates it does not diffract and spread out. They are typically generated from axicons.

Bessel beams due to their non diffracting property are drawing attentions for different applications. When converting a collimated beam into a ring the plano side of the axicon should face the collimated source. A par tic u lar use is also the gen er a tion of non dif frac tive bessel like beams. Electromagnetic acoustic gravitational and matter waves can all be in the form of bessel beams.

They are commonly used to create a beam with a bessel intensity profile or a conical non diverging beam. Express 16 12688 12700 2008. Bessel beam generation from round tip axicon we model the generation of bessel beams with an axicon with a round tip and investigate how the round tip may influence the bessel beam evolution. In this example we investigate the effect of the round tip on the generated bessel beams following the research work in o.

The bessel beam side lobes show an interfer ence pattern with a shallower radial intensity gradient than in the gaussian case. Single axicons are usually used to generate an annular light distribution which is laterally constant along the optical axis over a certain range. Brzobohatý et al opt. Generating bessel beams for micro processing canunda axicon is an off axis reflective axicon that generates high quality bessel beams for glass processing with an ultra short pulse laser.

Here the bessel beam center exhibits the typical sub diffractive intensity spot with a full width at half maximum fhwm of 0 32λ and the first intensity mini mum at 0 26λ. An ideal axicon with infinite tip does not exist and in practice an axicon comes with a rounded tip.