This Small Business Innovation Research (SBIR) Phase I project is aimed for manufacturing high-density phase-locked fiber laser arrays that can be made with extremely high precision and quality that will be free from mechanically induced defects. The company has developed a novel technique for coherent power-combining a specially structured group of phase-locked fiber lasers in a common cladding so that their phases are synchronized in favor of the fundamental in-phase mode through strong evanescent wave interaction. It has been shown that the output of phase locked fiber lasers and amplifiers can provide extremely high power (multi-kW) with a good beam quality (M2 < 1.5) in a compact package. Such a laser is very desirable for material processing and precision manufacturing and offers many attractive features, such as maintainability, transportability, and affordability. The Company has developed an efficient side-pumping technique by which a uniform gain can be established over a long fiber length far exceeding the absorption length. Combining a defect-free multi-core fiber with this side pumping technique, it will be possible to realistically scale the output power of a phase-locked fiber laser array up to multi-kW in a spot size of about 50 micron in diameter (equivalent to a laser intensity greater than 10 MW/cm2) without encountering catastrophic failure. Under Phase I, efforts will be focused on designing and experimenting with a defect-free phase-locked fiber array. In addition, experiments will be performed to verify the power-scaling law that is proportional to not only the fiber core area but also the length. Results will be used to formulate the prototype for the Phase II. Commercially, because fiber laser efficiency is at least 4 times higher than the solid-state laser and operates at a more desirable wavelength than the CO2 laser, it will have a much better chance to succeed in the market place to replace the existing solid-state and CO2 lasers, which have been used extensively as precision machine tools for present-day manufacturing in aerospace, automotive, ship-building, refractory metals, graphite, and composite materials industries. With these technological advancements, a multi-kW fiber laser with a highbrightness beam can be manufactured economically and reliably and can offer an order of magnitude increase in speed and high-resolution for precision manufacturing.
