High Energy, Multi-Component, Optical Isolator for 2 Micron Fiber Lasers

Aqwest proposes to develop innovative fiber-coupled isolators (FCI) that can handle high-average and peak powers in 2 µm pulsed fiber amplifiers now being developed by the U.S. Air Force (USAF) as a part of an all-fiber pulsed laser system. The FCI design will support the inclusion of common fiber components such as fiber tap couplers, mode field adapters, and spectral filters. Our FCI concept offers 1) Drastic reduction in thermal lensing and birefringence, 2) Commercially available Faraday material, 3) Active cooling to remove heat deposited by the laser beam, 4) Reduced likelihood of optical damage, and 5) Active temperature control to optimize optical isolation. The proposed project will leverage Aqwest earlier work in optical isolators (OI) and extensive 2 µm laser testing capabilities.In the Phase I project, we conducted analytical and experimental validation of our innovative FCI concept and showed by analysis and experiments that the FCI can provide the capabilities targeted by the USAF.  In particular, we developed and tested with our 2 µm lasers a full-scale yet very compact FCI unit traceable to the prototype unit deliverable in Phase II. A fiber-to-fiber coupling through the Prototype 1 was established. In Phase II, we will refine Aqwest’s FCI design to meet all objective requirements, perform validation of the design, develop assembly processes consistent with volume production of the FCI, validate the FCI producibility, deliver a batch of protype FCI units to AFRL/RDLT for assessment and testing, and work toward transitioning / licensing future production to a commercial manufacturer.In Phase III, Aqwest will work with AFRL/RDLT and industry partners to make their isolator design available to the DoD customer base, DoD industrial partners, and qualified commercial users.