New, High Performance, Free Space, 3 kW Faraday Isolators
Applications such as Directed Energy and Materials Processing in the >1 kW regime are now exceeding the limits of current Faraday isolator technology. Such applications often utilize coherent beam combining from fiber lasers or high aspect ratio Nd slab lasers.
At >1 kW, existing Faraday isolators can exhibit both high levels of depolarization due to thermal birefringence resulting in low isolation as well as thermal lensing due to thermal gradients resulting in degradation of M2 values.. Back reflections can result in damage to the faces of the fiber in such lasers or, in some cases, couple into the fiber resulting in damage to the laser itself.
To address these problems, EOT now offers a Faraday isolator that exhibits both minimal thermal lens focal shift and minimal depolarization at powers up to 3 kW. To minimize the thermal lens focal shift, EOT is utilizing a proprietary Faraday rotator material that has significantly reduced absorption relative to TGG. The result is a Faraday isolator that typically exhibits minimal thermal lens focal shift.
To address the problem of depolarization, EOT utilizes birefringence compensation. Birefringence compensation effectively improves the extinction of a Faraday isolator, thus greatly increasing the level of isolation that a Faraday isolator can provide at higher power levels. EOT’s high extinction thin film polarizers are available and ideally suited for 3 kW isolators.