Wavelength and topological charge management along the axis of propagation of multichromatic non-diffracting beams

Wavelength is a fundamental property of light that dictates its linear momentum and thus remains unchanged under unguided free-space propagation. Similarly, light’s orbital angular momentum is another strictly conserved property determined by light’s quantized topological charge. Here, using a superposition of co-propagating Bessel beams with different wavenumbers, wavelengths, and topological charges, we construct a new class of non-diffracting multichromatic optical beams in which the wavelength (linear momentum) and the topological charge (orbital angular momentum) can be managed locally along the axis of propagation via controlled beating. Engineering light structures with customized longitudinal profiles of wavelength and charge can offer new degrees of freedom in materials processing, optical trapping, imaging, and dense data communications.