  The combinations of artificial intelligence and lasers provide powerful ways
to form smart light sources with ground-breaking functions. Here, a Raman fiber
laser (RFL) with reconfigurable and programmable spectra in an ultra-wide
bandwidth is developed based on spectral-spatial manipulation of light in
multimode fiber (MMF). The proposed fiber laser uses nonlinear gain from
cascaded stimulated Raman scattering, random distributed feedback from Rayleigh
scattering, and point feedback from an MMF-based smart spectral filter. Through
wavefront shaping controlled by a genetic algorithm, light of selective
wavelength(s) can be focused in the MMF, forming the filter that, together with
the active part of the laser, actively shape the output spectrum with a high
degree of freedom. We achieved arbitrary spectral shaping of the cascaded RFL
(e.g., continuously tunable single-wavelength and multi-wavelength laser with
customizable linewidth, mode separation, and power distribution) from the 1st-
to the 3rd-order Stokes emission by adjusting the pump power and
auto-optimization of the smart filter. Our research uses
artificial-intelligence controlled light manipulation in a fiber platform with
multi-eigenmodes and nonlinear gain, mapping the spatial control into the
spectral domain as well as extending the linear control of light in MMF to
active light emission, which is of great significance for applications in
optical communication, sensing, and spectroscopy.
