Misalignment Considerations in Laser Diode to Single-mode Fiber Excitation via Hemispherical Lens on the Fiber Tip

We report the theoretical investigation of the excitation efficiency of a laser diode to a single-mode fiber via a hemispherical lens on the fiber tip in presence of possible transverse and angular misalignments. The analysis takes care of the allowable aperture provided by the hemispherical lens. By employing ABCD matrix for refraction of paraxial rays by a hemispherical lens, we present analytical expressions of such coupling efficiencies and calculate the corresponding losses involving very little computations or even a pocket calculator. The results seem to be useful in the design of optimum launch optics to get maximum coupling efficiency.

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