Laser forming for sub-micron adjustment: with application to optical fiber assembly

Laser forming is a method to deform a material by controlled local laser heating. In combination with a dedicated actuator topology, those deformations can be used for high precision alignment of components. This thesis applies this method to the alignment of optical fibers with respect to the waveguides on photonic integrated circuit chips. Recent advances in optical waveguide technology on these chips allow for wavelengths from UV to the visible range. However, the connection and assembly of the fibers requires an alignment accuracy of about 0.1 µm, which cannot be achieved using passive alignment. A fiber alignment actuator was developed that consists of a stainless steel tube. The tube can be bent locally by laser forming, resulting in a translation of the fiber tip. It has been found that there exists significant scattering of the magnitude and direction of the bending. Therefore, an alignment algorithm was developed that sets the optimal process parameters to iteratively converge to the optimal position with a minimum number of bending steps. Simulations and experiments using this algorithm show that the fiber tip reaches the target position within 15 steps, with an accuracy of 0.1 µm