Laser diode to single-mode circular core dispersion-shifted/dispersion-flattened fiber excitation via hyperbolic microlens on the fiber tip: Prediction of coupling efficiency by ABCD matrix formalism

The formulated ABCD matrix formalism is employed to prescribe analytical expression of coupling efficiency of a laser diode to single-mode circular core dispersion-shifted as well as dispersion-flattened fiber via hyperbolic microlens on the tip of the fiber. We assume that field distribution in case of both the source and the fiber is one parameter Gaussian type. For maximum excitation efficiency, it is required that the lens transmitted spot size of the source should match with the spot size of the fiber. Further, as regards the spot size of the fiber, we use Petermann II spot size in order to take care of non Gaussian nature of field of such fibers and to make the estimations more realistic thereby. The investigations are carried out for two different wavelengths 1.3 and 1.5 μm. Our simple method predicts the concerned coupling optics excellently and the necessary evaluations require little computations. This simple but accurate technique is expected to benefit the system designers who work in the field of optical technology.