Topological Charge of Multi-Color Optical Vortices

The topological charge of an optical vortex is a quantity rather stable against phase distortions, for example, turbulence. This makes the attractive communications, but many structured beams it unknown. Here, we derive (TC) coaxial superposition spatially coherent Laguerre–Gaussian with different colors, each beam its own wavelength and TC. It turns out that TC such equals LG longer wavelength, regardless weight coefficient this in interesting instantaneous conserved on propagation, whereas time-averaged intensity distribution colored changes gamut; if, near field, colors light rings arrange along radius according to their TCs from lower greater, then, space cross-section are arranged reverse order greater We also demonstrate that, by choosing appropriate wavelengths (blue, green, red) three-color single-ringed beams, possible generate, at some propagation distance, ring white color. If all have same TC, then there single nearly initial plane. Then, space, acquire radii: smaller shorter wavelength.