Bessel Beam Axicon

The analytical field of the focal ring is used with a fourier transform lens to generate a bessel beam.

Bessel beam axicon.

An area with almost constant intensity dis tri b u tion the length of which is defined by the angle and diameter of the axicon is of interest here. Brzobohatý et al opt. Bessel beams due to their non diffracting property are drawing attentions for different applications. Single axicons are usually used to generate an annular light distribution which is laterally constant along the optical axis over a certain range.

Special features and bessel beam shaping. Unlike a gaussian beam which deteriorates over distance a bessel beam is non diffracting maintaining an unchanged transversal distribution as it propagates. Technically a bessel beam cannot be created as it requires infinite energy. One such field is laser glass cutting often done with single mode ultrashort pulse lasers in the ir and green wavelengths.

This means that as it propagates it does not diffract and spread out. A beam closely resembling a bessel distribution can be generated by passing a gaussian beam through an axicon and taking the projection of the beam close to the axicon s conical surface. The axicon is primarily used in the field of beam shaping and in various laser ap pli ca tions. An ideal axicon with infinite tip does not exist and in practice an axicon comes with a rounded tip.

Axicon bessel beams are used in a variety of laser applications where the focus media is transparent at the laser wavelength. They are typically generated from axicons. A comparative analysis between the use of an illuminated annular aperture an axicon and a toric lens to generate a bessel beam is performed and the benefits and drawbacks of each are discussed. 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.

A true bessel beam is non diffractive. A bessel beam is a wave whose amplitude is described by a bessel function of the first kind. 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. Electromagnetic acoustic gravitational and matter waves can all be in the form of bessel beams.

In this example we investigate the effect of the round tip on the generated bessel beams following the research work in o. Bessel beams are also self healing meaning that the beam can be partially obstructed. 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. A bessel beam is a non diffracting beam of concentric rings each having the same power as the central ring.

The bessel beam side lobes show an interfer ence pattern with a shallower radial intensity gradient than in the gaussian case. A par tic u lar use is also the gen er a tion of non dif frac tive bessel like beams. This special feature results from the generation of non diffracting bessel like beams with properties mainly determined by the axicon angle α. This is in contrast to the usual behavior of light which spreads out after being focused down to a small spot.