0000000000852015
AUTHOR
D. Ceoldo
Second harmonic generation and beam cleaning in optically poled multimode graded-index fibers
Recent experimental results have confirmed that nonlinear effects in multimode graded-index (MM-GRIN) fibers lead to a wealth of observable spatiotemporal effects. In spite of the large number of modes supported by the fiber, by increasing the input power the transverse profile evolves in a clean bell-shaped beam [1, 2]. Next, the input laser line experiences a strong spectral broadening and Geometric Parametric Instability (GPl) peaks are observed [3].
Second harmonic generation in multimode graded-index fibers: spatial beam cleaning and multiple harmonic sideband generation
We study experimentally and numerically the spectral and spatial dynamics of second harmonic generation in an all-optically poled multimode graded-index fiber. In contrast with poled single-mode fibers, in a multimode graded-index fiber a pump can generate a series of sharp sidebands around its second harmonic (SH) that originate from the sub-millimetric periodic evolution of the intensity at the fundamental frequency. The mutual interaction between the fundamental and its SH may also strongly affect the spatial distribution of guided light for both colors: when increasing the pump power, both fundamental and SH output beams evolve from disordered multimode speckles into two bell-shaped bea…