Three-dimensional micropositioning device for optical fiber guided by a piezoelectric tube

This paper describes the principle function and the possible applications of a new micropositioning device for the optical fiber, which aligns it precisely to a light source, with a resolution better than 100 nm. One end of an optical fiber is fixed to one end of a piezoelectric tube. The electrical voltage applied to the 5 external electrodes around the piezoelectric tube will create transverse motion (up till +/- 20 mum) and longitudinal motion (of 1 to 2 mum) and the optical fiber fixed to this tube will make the same motion. The other end of the optical fiber passing through the tube fixed to a support is connected to a photometer,, which measures the light intensity. The measure allows determining the best voltage for the command of the 5 electrodes with a help of programmed algorithms. Small dimension and very short time response of this device would allow multiple applications for the light injection in a wave-guide. The first application is related to the guide to guide light coupling, for the automatic centering of two optical fibers, and a fiber to the input of an integrated optics beam combiner. The second application concerns pupil's fragmentation and second generation VLTI instruments. The alignment of height optical fibers with an object of the sky, coming from height telescopes or height sub-pupils of one telescope, could be controlled independently and in real time. The light coupling into every fiber and the optical length path are micro-adjusted in an optimal way, in spite of atmospheric turbulence effects.