Device for generating a polychromatic beam of photons and substantially constant energy

A generation device (DG) comprises: • a pulse laser source (SL) supplying primary photons having at least one wavelength in pulses having a temporal asymmetry, • shaping means (MM) acting on the primary photons for providing an input beam (FE) focused and having a selected polarization, and • an optical fiber (FO) in which the primary photons induce secondary photons having different wavelengths resulting from Raman conversions cascade and forming an output beam (FS), broad spectrum substantially constant energy.