LIGA-based flexible microstructures for fiber-chip coupling

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Abstract
Moveable and flexible microstructures can be fabricated by a combination of the LIGA process and sacrificial layer techniques. A promising application of such flexible structures can be seen in the field of integrated optics, where the problem of precisely coupling fibers to integrated optical chips still demands a satisfactory solution. In the LIGA structure the fibers are guided by precisely positioned stop faces and then precisely located and prefixed by integrated spring elements. The fabrication of these spring-element arrays by the LIGA process has several advantages: the thermal expansion coefficient of the substrate can be matched to the optical chip material; the use of spring elements for prefixing simplifies the handling; and adhesives and related problems can be avoided. Additionally, a small center spacing of the fibers can be reached with a curved parabolic profile of the spring elements using the LIGA advantage of unrestricted design in the cross-sectional shape. First measurements of load deformation on the spring elements show that the values for the modulus of elasticity and for tensile strength found in literature for bulk nickel can be used for electrodeposited nickel too.