Compact, Light-weight, High Power Handling Fiber Coupled Optical Isolator

Fiber optic isolators are critical to prevent deleterious back-reflection effects in high power optical fiber laser systems. To address coherent beam combining (CBC) and other high optical power DoD applications, a compact and power scalable fiber coupled in-line isolator is currently needed that can operate at 1064 nm at forward optical power levels over 100 W, with optical loss less than 0.2 dB and isolation greater than 45 dB. Broadband optical power handling in the reverse direction must be greater than 50 W. To meet DoD needs, this proposal develops an innovative fiber optic isolator that is compact and magnetless, thereby reducing size weight and power. Locking technology is implemented to ensure that high isolation is maintained over a large range of operating conditions. The isolator material is ultra low loss and is mode matched to standard double clad fibers. Modeling and simulation of the optical properties will be used to optimize the device geometry to maintain both high power handling as well as low loss. Device testing will focus on validating the isolation efficiency as well as confirm high power handling capability. Other efforts will focus on demonstrating ultra low optical loss < 0.2 dB. Approved for Public Release | 18-MDA-9817 (23 Oct 18)