Techniques to sort Bessel beams

Abstract

In this work we will present two techniques for the measurement of superimposed higher-order Bessel beams. In the first technique we will outline a simple approach using only a spatial light modulator and a Fourier transforming lens to decompose the OAM spectrum of an optical field. We test this approach on symmetric and non-symmetric superpositions of non-diffracting higher-order Bessel beams. Our second procedure consists of two refractive optical elements which perform a Cartesian to log-polar coordinate transformation, translating helically phased beams into a transverse phase gradient. By introducing two cylindrical lenses we can focus each of the azimuthal modes associated with each Bessel beam to a different lateral position in the Fourier plane, while separating the radial wave-vectors in the image-plane.

Quantitative orbital angular momentum measurement of perfect vortex beams

“…PVs with OAM have been extensively created [12][13][14][15][16][17][18][19] and applied [20][21][22][23][24][25], but measurement techniques are still in their infancy [26]. In contrast, OAM has been measured qualitatively using mode sorters for Laguerre-Gaussian and helical beams [27][28][29][30], extended to radial modes [31,32], with adapted approaches to find the mode indices for Bessel-Gaussian [33][34][35] and Hermite-Gaussian modes [36]. This detects the mode but cannot return the full information of the field.…”