Fiber lenses

For many applications in communication engineering and medical technology, the collimation and beam shaping at the end of optical fiber systems has a big impact on system performance. The increase of the coupling efficiency between light sources, fibers and detectors, the adaptation of the radiation characteristics of endoscopic instruments as well as the improvement of the properties of fiber optical sensors are results of the integration of micro optics. The combination of external optical components on the fiber tip or directly in front of the fiber exit needs high alignment accuracy and small mounting tolerances. A promising alternative is the manufacturing of micro lenses directly onto the fiber ending. The reduction of the number of optical interfaces reduces optical losses and eases alignment of the system. Adhesion problems caused by thermal or mechanical stress are eliminated.

Fiber lens, sapphire	Fiber lens, fused silica

The direct shaping of the fiber ending can be performed by F₂-laser ablation using a mask projection method with irradiation perpendicular to the fiber axis. The shape and the size of the lens on the fiber ending are given by the appropriate choice of the mask and are therefore tunable in a wide range. Another method is laser ablation perpendicular to the fiber end face. The laser beam is controlled in circular traces across the surface. The beam diameter and scan velocity of the beam relatively to the fiber define the lens parameters. This method enables the realization of nearly arbitrary, user-defined lens shapes.

Further information:

Flyer „Micro-lens machining on optical fibers”

T. Fricke-Begemann, J. Li, J. Dou, J. Ihlemann, P.R. Herman, G. Marowsky
Laser machining of micro-lenses on the end face of optical fibers
Proc. LIM 2005, p. 733

J. Zinn, M. Schütte, J. Meinertz, J. Ihlemann
F₂-laser fabrication of fiber-integrated optical elements
Journal of Laser Micro/Nanoengineering 5, 6 (2010)