Generation and Propagation of Partially Coherent Power-Exponent-Phase Vortex Beam

Abstract

We report on a partially coherent power-exponent-phase vortex beam (PC-PEPV), whose spatial coherence is controllable and the initial phase exhibits a periodic power exponential change. The PC-PEPV beam was generated experimentally with various spatial coherence widths, and its propagation properties were studied both numerically and experimentally. By modulating the topological charge (TC) and power order of the PC-PEPV beam, the structure of the vortex beam can be adjusted from circular to elliptic, triangular, quadrangle, and pentagon. When the power order is odd, the PC-PEPV beam with a negative TC can be generated, and the profiles of the PC-PEPV beam can be precisely controlled via adjusting the value of the power order. For the case of high spatial coherence width, the number of the dark cores in the polygonal intensity array of the PC-PEPV beam equals the magnitude of the TC. However, when decreasing the spatial coherence width, the dark cores vanish and the intensity gradually transforms into a polygonal light spot. Fortunately, from the modulus and phase distributions of the cross-spectral density (CSD), both the magnitude and sign of the TC can be determined. In the experiment, the modulus and phase distribution of the CSD are verified by the phase perturbation method. This study has potential applications in beam shaping, micro-particle trapping, and optical tweezers.

Effect of azimuthal phase gradient variation on optical spiral vortex

“…These include composite beams achieved through multi-channel superposition 18,19 , generation and manipulation of vortices using metasurfaces 20,21 , and other approaches. Recently, unconventional OV configurations have gained attention, such as power-exponent-phase vortex (PEPV) [22][23][24] , multiplexed generalized vortex beams 25,26 , and the generation of multiple twisted beams through azimuthal shift factors 27 . Some studies have also investigated the optical forces generated by phase gradients 28 .…”

Superposing and modulating heterogeneous optical vortices of high-order orbital angular momentum

“…The spiral intensity of these beams is modulated by the exponential phase term, resulting in an uneven spiral phase gradient [26,27]. The phase of the beam specifically exhibits an exponential increase along a closed path near the central point [28]. Recent studies have explored the propagation of the power index phase vortex of a Gaussian beam within a paraxial ABCD system [23].…”

Optical spiral vortex from azimuthally increasing/decreasing exponential phase gradients

“…Various modulation methods have been explored for OV carrying OAM, such as using multi-channel superposition to obtain composite beams [19,20] , metasurface generation, and manipulation of vortices [21,22] . Recently, some more unconventional vortex beams have been proposed, such as the powerexponent-phase vortex (PEPV) beams [23][24][25] , multiplexed generalized vortex beams [26,27] , and the generation of multi-twisted beams via azimuthal shift factors [28] . Although some studies have demonstrated that phase gradients (PGs) can generate optical force [29] , research on the unique effects of different PG directions on vortex beams is severely limited.…”