Microtube Laser Forming for Precision Component Alignment

A micro-actuator for precision alignment, using laser forming of a tube, is presented. Such an actuator can be used to align components after assembly. The positioning of an optical fiber with respect to a waveguide chip is used as a test case, where a submicron lateral alignment accuracy is required. A stainless steel tube with an outer diameter of 635 μm was used as a simple and compact actuator, where the fiber is mounted concentrically in the tube. An experimental setup has been developed to measure the fiber displacement in real time with a resolution better than 0.1 μm. In addition, this setup allows the axial and radial positioning of the laser spot over the surface of the tube. Several tube samples were (de)formed to move a fiber to a predefined position, using a laser with a wavelength of 1080 nm, a pulse length of 200 ms, and a power between 4 W and 10 W. On average of 18 laser pulses were required to reach the targeted position of the fiber with an accuracy of 0.1 μm. It has been found that increasing the laser power not only results in a larger bending angle but also in a larger uncertainty of this angle. The opposite is true for the radial bending direction, where the uncertainty decreases with increasing laser power.