Modelling of photodarkening in Yb glass

Photodarkening can typically reduce the output power of a fiber laser with about 10% over 1000 hours. 

Acreo and Crystal Fibre A/S have carried out a joint research project to determine the nature of photodarkening, and on a longer perspective minimize the effect by optimizing fiber design and material composition. Several mechanisms related to the formation of induced color centers were identified in the project.

Please refer to the publications below for project results. A 'popular' summary can be found in Aperturen.  The project was concluded with the dissertation of Magnus Engholm in May 2008.

Publications

	Engholm, M., Materials Optimization for Optical Fiber Amplifiers and Fiber Lasers. PhD thesis. Mid Sweden University, Sundsvall, Sweden, 2008.  abstract
	Engholm, M. and Norin, L., "The role of charge transfer processes for the induced optical losses in ytterbium-doped fiber lasers ". Photonics West, Laser Source Engineering. SPIE, San Jose, USA. January 2009.
	Engholm, M. and Norin, L., "Preventing photodarkening in ytterbium-doped high power fiber lasers; correlation to the UV-transparency of the core glass.", Optics Express, 16, 1260–1268. 2008. abstract
	Engholm, M. and Norin, L., Comment on: "Photodarkening in Yb-doped aluminosilicate fibers induced by 488 nm irradiation". Optics Letters, 33(11), 1216-1216, 2008. abstract
	Engholm, M. and Norin, L., "Reduction of Photodarkening in High Power Fiber Lasers". Photonics West, Proc. SPIE, San Jose, USA. January 2008.
	Engholm, M. and Norin, L., "Materials Optimization for Ytterbium-Doped High Power Fiber Lasers", Conference on Lasers and Elecrooptics (CLEO 2008), San Jose, May 2008.
	Engholm, M., Norin, L., and D. Åberg. "Strong UV-absorption and visible luminescence in ytterbium-doped aluminosilicate glass under UV-excitation.", Optics Letters, 32, 3352–3354. 2007. abstract
	Engholm, M., and Norin, L., "Divalent Ytterbium in Ytterbium Doped Aluminosilicate Glass: Aspects on Photodarkening in Fiber Lasers", poster, Conference on Lasers and Electro-Optics (CLEO), Baltimore, Maryland, USA, May 2007.
	Engholm, M., Norin, L., "Materials design for high power lasers", poster, Optik i Sverige, Skellefteå, Sweden, November 2007.

Partners:	Acreo, Crystal Fibre A/S, Mid Sweden University
Funding:	Acreo, Fiber Optic Valley, Länsstyrelsen i Gävleborg, Mål2 Norra, NKT Academy
Contact:	Lars Norin, Acreo Fiber Photonics