OSMOSIS

The recent use of multimode fibers in ultrafast optics has unveiled a rising paradigm, where nonlinear processes, such as beam self-cleaning, can overcome the adverse effects of the intermodal dispersion. This inspires the development of the next generation of ultrashort fiber lasers, which should have a larger versatility in terms of pulse profile, spectral coverage, and energy scalability, thus meeting an extended range of applications. However, the field of multimode nonlinear optics is still in its infancy, with its potential to extend the spectral coverage of coherent sources clearly underused. In the OSMOSIS project, we shall demonstrate a new laser source able to self-generate both fundamental and harmonic waves in the ultrashort-pulse regime. To achieve this, we will use optical poling to write an innovative second-harmonic generation (SHG) function directly within a multimode optical fiber. This special SHG fiber will be inserted in a versatile fiber laser cavity featuring extensive control over temporal, spectral and spatial degrees of freedom, to select phase matched nonlinear processes along with spatiotemporal mode-locking. The major asset of the OSMOSIS project is the complementarity between ICB and XLIM partners, at the state-of-the-art concerning nonlinear processes in multimode fibers (XLIM) and ultrafast laser dynamics and characterization (ICB). Fulfilling this ambitious objective will have far reaching impacts. In fundamental physics, we shall demonstrate the existence of a novel solitary wave: a (FF + SH) soliton arising from both second order and third order nonlinearities, which we call an octave soliton, and represents a spectral and spatiotemporal generalization of dissipative solitons. Concerning potential applications, our novel source will pave the way for a robust self-referenced frequency comb sources spanning over an octave, which will also benefit from the power scaling potential of multimode fibers.