A Simple Technique to Determine the Far Field Intensity Pattern of Laser Diodes and its Influence on Coupling Efficiency

Abstract

Both the far field intensity pattern (FFIP) of a laser diode and the fiber electric field profile play an important role in determining the coupling efficiency between laser diodes (LDs) and optical fibers. In this paper, we have introduced a novel model for the FFIP of laser diodes, which is based on the non-linear regression technique. The advantage of this new model compared to that of previous FFIP models is that, the later requires laser diode parameters such as the thickness, effective index and relative refractive index to generate the theoretical far field intensity pattern. Manufacturers of commercial laser diodes normally do not provide these parameters and thus researchers have been using Gaussian approximation in the analysis of FFIP. In this work, we would show that the proposed new model reflects a more accurate representation of the far field intensity pattern compared to the Gaussian model, thus enabling a better estimation of the spot size of the LD. Based on this model and the actual electric field distribution of the single-mode fiber we have analysed the coupling efficiency between a LD and a conically lensed fiber. The obtained results are in better agreement with the experiment, for example we have obtained 56% as the maximum theoretical value for the coupling efficiency using this new proposed model which is very close to the experimental result of 55%).