Imaging micro lens array beam integrator system design for fiber injection

Abstract

This paper documents the design, analysis and testing of Micro Lens Array (MLA) beam integrator systems for the investigation of the injection of a single mode laser into square and round fibers (two sizes each), and a rectangular fiber. This research focused on methods that could enhance the development of a uniform speckle pattern at the output end of the fiber, the injection systems are designed to fill the modes of the fiber (as much as practicable) and match the NA of the fiber. The designs for the square and rectangular fibers are based on lenslet array components available from off-the-shelf fabricators. It can be argued that the number of modes injected into the fiber is proportional to the number of lenslets in the input beam. Evaluation at the design phase leaned towards lenslet arrays with small lenslet sizes. However, diffraction limits how small the lenslet arrays can be. For this reason the final designs were configured using a micro lens array (MLA) based imaging integrator approach. An overview and tests results will be presented to evaluate the benefits and limitations of such fiber injection techniques.