Zusammenfassung
We have studied the evolution of the phase front of an apertured first-order Bessel beam (J(1)) generated by a diffractive axicon during free-space propagation and its transformation in a Raman-resonant four-wave mixing process in hydrogen gas. It is demonstrated that the order of the phase singularity (vortex) of a Bessel beam can easily be detected by interferometry at the boundaries of the ...
Zusammenfassung
We have studied the evolution of the phase front of an apertured first-order Bessel beam (J(1)) generated by a diffractive axicon during free-space propagation and its transformation in a Raman-resonant four-wave mixing process in hydrogen gas. It is demonstrated that the order of the phase singularity (vortex) of a Bessel beam can easily be detected by interferometry at the boundaries of the beam propagation range. With a J(1) beam and a Gaussian beam at the Stokes and the pump frequencies and vice versa, anti-Stokes light is generated as a singular, conical beam. In both cases the observed phase front agrees with theoretical predictions. In particular, the transformation of the topological charge is consistent with the conservation of angular momentum. (C) 2001 Optical Society of America.
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