Beam-shaping and fiber coupling

Using anamorphic optics to increase coupling efficiency

Optical scheme

A circular beam profile is  preferred over the elliptical profile usually provided by laser diodes LD or by tapered amplifiers TA when coupling into single-mode fibers in order to increase the coupling efficiency. Due to the different collimated beam diameters in the two elliptical axes the calculated optimum focal lengths are different for the two axis and a compromise must be found by doing the calculation for the optimum focal length with an effective beam diameter.

Anamorphic optics act one-dimensionally on the elliptical profile of the colli­mated beam and adjust the larger beam diameter to the dimension of the smaller one, producing a radially symmetric beam. The focal length of the laser beam coupler can then be chosen optimally for a circular beam resulting in an increased coupling efficiency.