Designs of fiber coupling without collimation based on photonic crystal laser diodes

Abstract

We have designed a fiber coupling method based on the spatial beam combining of the Photonic Crystal (PC) Laser Diode (LD). The PC LD with a small fast-axis divergence angle makes it possible to reduce the requirements for the numerical aperture and the processing precision of the optical elements, increase the alignment tolerance of components, reduce the difficulty of shaping, and improve the product yield. In the module, there is no need for the collimation of the fast-axis and slow-axis beams, which can be simultaneously focused into the optical fiber through an aspheric cylindrical lens. The simulated results, obtained by the ray tracing method, have shown a coupling efficiency of around 91.4% when the PC LD is coupled into a fiber with a core diameter of 105 μm and the numerical aperture of 0.22. Then, we have performed the experiments, and the coupling efficiency of 71.5% has been achieved. By analyzing the deviation of the simulated and experimental coupling efficiency, we have proposed several solutions. Finally, according to the strategy of this beam shaping, we also list several promising arrangements, which further prove that the beam shaping method possesses broad application prospects.