High quality quasi-Bessel beam generated by round-tip axicon

Area of Science:

• Optics and Photonics
• Beam Propagation
• Diffractive Optics

Background:

• Axicons generate quasi-Bessel beams with unique propagation characteristics.
• A rounded tip on axicons causes beam distortion due to interference.
• Undesired intensity modulation disrupts the stable lateral and on-axis intensity profiles of quasi-Bessel beams.

Purpose of the Study:

• To analyze the spatial intensity distribution of zero-order Bessel beams produced by axicons with rounded tips.
• To investigate the interference effects caused by the rounded tip and their impact on beam quality.
• To demonstrate a method for improving the spatial beam distribution and mitigating modulation.

Main Methods:

• Theoretical study and experimental investigation of beam propagation.
• Numerical simulation using Hankel transformations to model beam propagation and filtration.
• Experimental measurement of beam intensity distribution in various lateral planes.
• Spatial filtration in the Fourier plane to remove intensity modulation.

Main Results:

• The rounded tip of the axicon generates a refracted beam that interferes with the quasi-Bessel beam.
• This interference leads to significant intensity modulation, degrading beam properties.
• Spatial filtration effectively removes the undesired modulation, improving the beam's spatial distribution.
• Excellent agreement was found between computed and experimentally measured beam distributions.

Conclusions:

• The spatial intensity modulation in Bessel beams from rounded-tip axicons can be effectively suppressed.
• Spatial filtration in the Fourier plane is a viable technique for beam quality restoration.
• The study validates the numerical methods used for simulating beam propagation and filtration.