Scalable Coherent Array of Fiber Optic Laser Devices (SCAFOLD)

Power and brightness scaling of single-fiber lasers is limited by intrafiber damage intensity. Hence, scaling to kW levels requires designs which coherently integrate the output of multiple fibers while, at the same time, avoiding nonlinear effects (suchas SBS) which limit the output power from a single fiber. We have devised a technique whereby multiple fiber sources can be combined coherently to produce an output with an N-fold increase in power and with an N2-fold increase in brightness. The specifictechnique involves a spectrally-tailored seed signal which feeds an array of equi-length fiber amplifiers. By feeding all amplifiers from a common master, both synchronism in operating frequency and temporal coherence is achieved. Each fiber amplifierincorporates a control element for precise control of the phase at its output; thereby allowing for synthesis of the required spatial phase front and, hence, the desired far-field beam profile. Our approach toward achieving multi-kilowatt powers islargely insensitive to variation in fiber parameters, eliminates the need for precise control of multiple oscillators, suppresses parasitic nonlinear effects, and is infinitely scalable by virtue of its modularity.