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- Title
Influence of the Nonideality of the Axicon and Input Gaussian Beam on the Quality Parameters and Fourier Spectrum of the Generated Bessel Light Beam.
- Authors
Balykin, I. V.; Ryzhevich, A. A.; Kazak, N. S.
- Abstract
The influence of three factors on the formation of a Bessel light beam (BLB) in the scheme of transforming a Gaussian beam by an axicon were investigated using Fourier optics via numerical simulation. The factors were the ellipticity of the incident light beam, the ellipticity of the axicon, and the presence of a round tip on the axicon. The results of the influence of each factor on the structure and quality parameters kc, kr, and ⟨R2⟩. of the formed BLB and its Fourier spectrum (FSBLB) are shown. The quality parameters of the FSBLB kIs, kws, and krs, which characterized the spread of the amplitude, half-width, and average frequency of the conical component of the FSBLB, and the parameter η, which determined the ratio of the energy in the conical component to the total energy of the beam, were introduced to analyze the quality of the FSBLB. The ellipticity of the Gaussian beam incident on the axicon led to a reduction in the length of the BLB region of existence. However, all quality parameters decreased, with the coefficient of constancy kc dropping most quickly, as the longitudinal coordinate increased. FSBLB quality parameters kIs and kws, which characterized the spread of the intensity and half-width of the conical component of the beam, decreased with increasing eccentricity of the Gaussian beam half-width εb. The ellipticity of the axicon affected all BLB quality parameters, most clearly the coefficient of constancy kc and the average value of R2, which decreased with an increase in the axicon eccentricity εa. This happened because of oscillations in the ring closest to the BLB axis. The shape of the FSBLB also changed with increasing εa, transitioning from circular to elliptical and causing the coefficient of constancy of the conical component spectral frequency to decrease. Regularities in the transverse intensity distributions of BLBs formed by azimuthal modulation of the cone angle were considered for the case where the number N of complete oscillation periods of the cone angle were >2. The number of intensity minima in the paraxial ring for a small axicon base angle modulation amplitude B (≤ 0.05) was equal to N for odd N and equal to 2N for even N. The number of minima in the paraxial ring of the beam was equal to 2N for large B values (>0.05) for both even and odd N. A spherical tip of an otherwise conical axicon led to the formation of a separate non-conical component in the spectrum. A hyperbolic axicon broadened the conical component of the spectrum in the direction of low spatial frequencies. The results could be used to form special light fields and to assess the quality of manufactured axicons and the ellipticity of a beam incident on an axicon.
- Subjects
BESSEL beams; GAUSSIAN beams; FOURIER transform optics; AMPLITUDE modulation; OSCILLATIONS; FACTOR structure
- Publication
Journal of Applied Spectroscopy, 2024, Vol 90, Issue 6, p1297
- ISSN
0021-9037
- Publication type
Article
- DOI
10.1007/s10812-024-01667-2