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New approach to fabrication of a Faraday isolator for high power laser applications

: Rothhardt, Carolin; Rekas, Miroslaw; Kalkowski, Gerhard; Eberhardt, Ramona; Tünnermann, Andreas


Honea, Eric C. (Ed.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Fiber Lasers IX: Technology, Systems, and Applications : San Francisco, California, USA, January 2012
Bellingham, WA: SPIE, 2012 (Proceedings of SPIE 8237)
ISBN: 978-0-8194-8880-0
Paper 82373Z
Conference "Fiber Lasers - Technology, Systems, and Applications" <9, 2012, San Francisco/Calif.>
Fraunhofer IOF ()
direct crystal bonding; terbium gallium garnet; sapphire; Faraday isolator; fiber laser application

We report on investigations of direct bonding of mono-crystalline Terbium Gallium Garnet (TGG) to sapphire for use as Faraday isolator in high power fiber laser applications. The technology of direct bonding allows joining of inorganic crystalline and non-crystalline materials without any auxiliary materials at high bonding strength. Lack of additional joining material and related absorption is very promising for high power laser applications. The ability to join different materials allows inserting sapphire as a heat spreader into the beam path for TGG cooling to avoid thermal lensing. All samples were subjected to extensive chemical cleaning and subsequent low temperature plasma activation before bonding. Bonding was performed under compressive forces in a high vacuum environment at moderate temperature. Optically transparent bonds with a very low fraction of defects were obtained. The size of the bonded area depends significantly on the samples' flatness.