ONYX OPTICS, INC. — Department of Defense SBIR Phase II: Yb:YAG crystalline fiber lasers can have a 9 times higher power limit (16.9 kW vs 1.89 kW)

Description

Yb:YAG crystalline fiber lasers can have a 9 times higher power limit (16.9 kW vs 1.89 kW) for narrowband lasers than a Yb-silica fiber laser due to the higher thermal conductivity (10.7 vs 1.38 W/m C) and the reduced SBS (stimulated Brillouin scattering) gain coefficient (10**(-15) to 10**(-12) vs 10**(-11) m/W). Thus, there are many efforts underway to develop crystalline fibers using laser media such as YAG. One of the difficulties of the technique appears to consist of attaining optical quality and accurate diameter control on fiber drawing or consolidation of the green ceramic fibers. Onyx Optics proposes producing doubled-clad true crystalline fibers and planar guides from Er-doped and Yb-doped single crystal YAG by employing Onyx Optics"manufacturing technology (Adhesive-Free Bond (AFB)). A scalable manufacturing process for designs to multi-kilowatt operation is the principal objective of the proposed work. Femtosecond inscribed waveguides will be investigated. Deliverables to ARL include double clad planar and crystal fibers of various lengths. Optical and mechanical properties, including scattering and absorption losses and refractive index difference evaluations will be performed. Special pump couplers intended for acceptance of high power from diode bar stacks and/or other large pump module formats will be designed, fabricated and tested.