The propagation properties of Helical Ince-Gaussian (HIG) beams in oceanic turbulence are analyzed using the random phase screen method. A comparative analysis of the spot centroid wander and the scintillation indices of different order HIG modes as a function of propagation distance has been performed. A comparative analysis of the spot centroid wander and the scintillation indices of different order HIG modes as a function of propagation distance has been performed. The results indicate that compared to the LG0,1 mode, the HIG mode with order p=m⪆1 has a smaller standard deviation of spot centroid wander and scintillation index during propagation. Especially, the standard deviation of the spot centroid wander decreases with the increase of the HIG mode’s order, while the scintillation indices of odd-order HIGm,m beams are generally higher than those of even-order HIGm,m modes. In addition, the scintillation index of the odd-order HIGm,m beam decreases with the increase of the ellipticity parameter, while that of the even-order HIGm,m beam increases. Finally, we conclude that under the influence of oceanic turbulence, the HIG mode has a lower scintillation index than the IG mode at the same propagation distance. The results have significant implications for the oceanic applications of the HIG modes.
Aiming at tightly focusing vector polarized partially coherent vortex laser beams, this paper introduced a new kind of vortex beams, named radially polarized multi-Gaussian Schell-model (MGSM) power-exponent-phase vortex beam (PEPVB). Based on the vectorial diffraction theory, this work theoretically and numerically investigated the tight focusing properties of radially polarized MGSMPEPVB passing through a high numerical aperture objective lens. Thus, we analyzed the impact of topological charge, power exponent, beam index and coherence length on the intensity of focal zone. We discovered that by increasing beam index, the intensity distribution of focal plane gradually changed from Gaussian to flat-top. Especially, when the power exponent was a non-negative fraction close to 1, regardless of whether the topological charge was an integer or not, the circular symmetry of the focused spot at focal plane would be destroyed, showing a non-uniform and asymmetric central dark core optical intensity distribution. Besides, the value of the fractional part of the topological charge would make the hollow structure of the central dark core fully open due to the introduction of power-exponent phase, which is an improvement over the tight focusing properties of radially polarized MGSM vortex beams. This work has clearly demonstrated that by changing the values of topological charge, power exponent, beam index and coherence length, the special focal spot structures with different intensity distributions including flat-top beam and irregular hollow beam can be obtained, which have many potential applications in laser machining and particle capturing such as manipulation of certain irregular microparticles.
Polarization selective devices are commonly utilized as rear mirrors to generate high power cylindrical vector (CV) beams in the resonators. The modes of these polarization sensitive resonators are very significant for the generation and application of CV beams. Upon the scalar eigenvector method, a vectorial eigenvector method (VEM) was used to compute the CV modes of polarization-selective resonators. Then, different polarization dependent resonators were simulated with the VEM. We can find that both mode TE01* and mode TEM00 are the eigen modes of polarization sensitive symmetric confocal sphere resonator and when Rte=0.99 and Rtm=0.93, TE01* most possibly appears in the cavity with polarization sensitivity due to its lowest loss. In addition, the VEM was used to guide our design of a 45-degree three-fold cavity structure for high power radially polarized laser. The axicon mirrors with azimuthal polarization selection and four λ/4 phase shifters are used to obtain the output of radially polarized light.