At the threshold of distributed Kerr-lens mode-locking in a Cr:ZnS waveguide laser

Abstract

We demonstrate feasibility of spatiotemporal mode-locking in a mid-IR Cr:ZnS waveguide laser based on the nonlinear spatial mode coupling. The experiment shows efficient power scaling with the excitation of intramode beatings, causing a pronounced 𝑄-switching, which could result in nonlinear mode-coupling. The contribution of such multimode beatings and resulting 𝑄-switching is confirmed numerically. We suggest that a particularly high nonlinearity in Cr:ZnS combined with multimode waveguide leads to a soft aperture induced by a pump beam. The numerical simulations demonstrate that such an aperture could provide an effective spatial mode control in a nonlinear multimode waveguide, which, thereby, opens the way to the birth of a spatiotemporal dissipative soliton, or light bullet, formation, thus forming the basis for the future distributed Kerr-lens mode locking in the energy-scalable solid-state waveguide (or yet unrealized fiber) laser.