Supercontinuum laser beam propagation in free space through atmospheric turbulence.

Abstract

We present a theoretical and experimental study of supercontinuum (SC) laser beam propagation through weak atmospheric turbulence, introducing a broadband extension of the Born-Rytov framework that generalizes discrete multiwavelength Rytov approaches to a continuous spectrum. The scintillation index is derived in the space-frequency domain, with the cross-spectral density expressed as the product of a turbulence-dependent term and a spectral term modeled by a multi-Gaussian ansatz over the full SC bandwidth. This formulation reduces the mean irradiance and its second moment to numerically tractable integrals weighted by the second-order statistics of refractive-index fluctuations, thereby establishing a unified framework bridging the coherence theory of broadband optical fields and atmospheric scintillation theory. Experimental measurements performed with a calibrated laboratory turbulence generator for six values of Cn2 provide a limited proof-of-principle validation of the model within the investigated turbulence regime. The measured SC scintillation index falls an order of magnitude below that of monochromatic Gaussian beams at visible wavelengths, consistent with spectral averaging across the broadband emission. This advantage reverses in the short-wave infrared for the present source, indicating that mid-infrared SC sources would restore the benefit for free-space optical propagation.