Laser to single-mode fiber coupling in the laboratory

Abstract

All the information necessary to achieve reasonably efficient coupling of semiconductor lasers to single-mode fibers is collected from the literature, derived when necessary, and presented in mainly tabular form. Formulas for determining the laser beam waist radius and the fiber-mode radius are given. Imaging relations connecting these values with the object and the image distances, including thick-lens correction factors, are given for three types of lenses: ball, hemisphere, and graded index. Sources for these lenses are indicated, and a discussion is also given about ways of reducing feedback effects and about the use of wedge-ended fibers.