Analysis of multi-photon absorption: z-scan using ultra-short Gaussian vortex beam

Abstract

We present a detailed theoretical investigation of the Gaussian vortex beam zscan to look over multiphoton absorption. For a fixed optical pump power, the material shows less optical limiting nature in the presence of a Gaussian vortex beam as compared with a conventional Gaussian beam. In the presence of ultrashort laser pulses, the central dark core of a Gaussian vortex beam can provide a stable and accurate zscan profile preventing thermal degradation of the sample and the contribution of other nonlinear optical phenomena. The large cross sectional area at the beam waist with the large divergence of the Gaussian vortex beam can be used for the zscan in the short range of propagation. Though discussed for multiphoton absorption, it may extend to singlephoton absorption in the presence of multiple energy levels participating in the absorption process.

A conceptual review on Bessel beams

“…The optical axis of the BB coincides with the axis of the axicon, and the far-field distribution is an annular shape. Any arbitrary order BB can be generated by pumping a suitable order collimated Gaussian vortex given by equation (3.14) [94] to the axicon. While the azimuthal phase variation of BB is provided by Gaussian vortex mode, its radial phase variation is attributed to the axicon.…”