Monolithic Coherent Laser Array in Multicore Fiber

A world-record 250 Watt multicore fiber laser will be demonstrated with a single, diffraction-limited lobe both in the near field and in the far field. The coherent coupling of the independent cores will be achieved using a monolithic Self-Fourier (SF) cavity which will be directly fusion-spliced onto the output end of the multicore fiber. The phase locking of the multiple cores occurs naturally due to the common feedback and infinite supermode discrimination provided by the SF cavity. A simple experiment will be performed using low-power Thulium fiber lasers to demonstrate the applicability of this technology at eye-safe wavelengths. The SF technology is, to our knowledge, the only technology that can be directly scaled to a weapon-class system using commercially available fiber lasers with a full-scale weapon system demonstration achievable in less than 5 years. This project will demonstrate the full potential of this technology in a single monolithic structure consisting of a multicore fiber laser fused to the Self-Fourier cavity. This Phase proposal is written assuming the continuation of our Phase I project using Yb-doped fiber lasers (wavelength ~ 1 micron). However, the technology can be modified in a straightforward manner to utilize eyesafe Tm-doped fibers (wavelength ~ 2 microns). At the beginning of the program, a decision will be made in accord with our sponsor as to which type of fiber we will be using, which will affect certain performance criteria as well as schedule and budget.