Abstract
Based on the prescribed ABCD matrix for refraction by hemispherical lens under paraxial approximation, we formulate an analytical expression of coupling efficiency of a laser diode to a single mode circular core graded index fiber via a hemispherical lens on the tip of the fiber. The analysis involves Gaussian field distribution for both the source and the fiber and consideration of allowable aperture provided by the hemispherical lens. In order to find out the suitable refractive index profile for maximum coupling efficiency, we investigate the coupling optics for different profile exponents in graded index refractive index profile. In this context two different laser diodes emitting wavelengths 1.3 μm and 1.5 μm are employed for the concerned study. It is found that the graded index fiber having triangular refractive index profile is the most efficient one for the said two wavelengths of practical importance. Our formalism is simple and executable with little computation. The results found should be of tremendous importance to the designer of such coupling in the field of optimum launch optics.
©2012 by Walter de Gruyter Berlin Boston
