SBIR-STTR Award

Three key enabling components are critically needed for advancing high power fiber lasers. They are the double clad, multicore fibers; high brightness diode laser pumps; and optical coupling between the pump and the fiber. This proposal is focused on the most neglected component, the coupling between the pump and fiber laser. Material damage thresholds eliminate end pumping as a viable way to achieve multiple kilowatt outputs from a double clad fiber laser system. Side pumping the entire surface of a double clad system has not shown promise due to excessive losses that are artifacts inherent in the design. The aim of this proposal is to develop a reliable optical coupling technique by distributing the pump power at various strategic locations along the length of the double clad fiber without compromising the fiber integrity. The design of our proposed coupling scheme takes into account the effective absorption of the fiber cores along the propagation length of the fiber. The pump power from a multimode fiber is injected into the inner cladding at an angle exceeding the critical angle. With this approach it may be possible to couple several kilowatts of pump power into the fiber without exceeding the material damage threshold. This proposal describes an approach and presents the necessary steps to demonstrate the practicality of our proposed coupling scheme. If the results of this Phase I prove successful a Phase II will be proposed to develop a prototype which will be delivered to the Air Force for demonstration. High power diode-pumped multicore fiber lasers can be very competitive in the market place as compared to high power diode-pumped solid-state lasers and C02 lasers presently employed by automotive, aerospace and ship-building industries for precision drilling, high-speed cutting and welding of metals and composition materia

This Phase II SBIR Proposal presents detailed description of a KW fiber laser, which is comprised of three key enabling components: (1) a properly configured phase locked fiber laser array with 19 Yb-doped cores, presently being developed under an on-going AF Phase II SBIR, (2) low-cost, pigtailed diode laser pumps, that have been selected and can be well fitted into the system with a proper design, and (3) very efficient couplers for side-pumping of the fiber laser, which is also being developed under an on-going AF Phase I SBIR. Under this proposed project, these components will be custom-made, qualified and integrated into a system, which will be used to demonstrate its performance targeted by the LITE project. This study will provide useful information regarding to power damage, output beam quality, and system packaging issues. Results will provide the guideline for establishing a reliable power scaling law for future high energy laser systems. This prototype will be packaged and functionally tested and delivered to the Air Force at the end of the project, along with testing results for characterizing the performance of this laser.

Benefits:
High power diode-pumped multicore fiber lasers can be very competitive in the market place as compared to high power solid-state lasers and CO2 lasers presently employed by automotive, aerospace and submarine industries for precision drilling, high speed cutting and welding of metals and composite materials.