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Quasi-Bessel beams from asymmetric and astigmatic illumination sources

: Müller, A.; Wapler, M.C.; Schwarz, U.T.; Reisacher, M.; Holc, K.; Ambacher, O.; Wallrabe, U.

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Optics Express 24 (2016), No.15, pp.17433-17452
ISSN: 1094-4087
Journal Article, Electronic Publication
Fraunhofer IAF ()
wave propagation; geometric optic; laser beam characterization; diffraction theory; scattering; propagation

We study the spatial intensity distribution and the self-reconstruction of quasi-Bessel beams produced from refractive axicon lenses with edge emitting laser diodes as asymmetric and astigmatic illumination sources. Comparing these to a symmetric mono-mode fiber source, we find that the asymmetry results in a transition of a quasi-Bessel beam into a bow-tie shaped pattern and eventually to a line shaped profile at a larger distance along the optical axis. Furthermore, we analytically estimate and discuss the effects of astigmatism, substrate modes and non-perfect axicons. We find a good agreement between experiment, simulation and analytic considerations. Results include the derivation of a maximal axicon angle related to astigmatism of the illuminating beam, impact of laser diode beam profile imperfections like substrate modes and a longitudinal oscillation of the core intensity and radius caused by a rounded axicon tip.