New type of vortex laser beams: Squared Laguerre-Gaussian beam

In this paper, we present new type of optical vortex called the squared Laguerre-Gaussian (LG)2 vortex beam. It is theoretically, numerically, and experimentally proved that these beams are Fourier-invariant and retain their structure at the focus of a spherical lens. In the Fresnel diffraction zone, such a beam is transformed into a superposition of conventional LG beams, the number of which is equal to the number of rings in the (LG)2 beam. The presented beams are structurally stable in the case of one intensity ring. A more general beam, calculated as a “product” of two LG beams, is also investigated. This beam is Fourier-invariant if the numbers of rings in two LG beams of the “product” coincide to each other. The considered beams supplement the basis of LG modes.