Use of gradient light guides in semiconductor lasers

A gradient light guide (glass fiber) with a parabolic distribution of the refractive index was used in a semiconductor laser resonator and as a collimator. A fiber 19 mm long of 0.8 mm radius and with a refractive index fall of 3X10^–10 was brought into direct contact with a laser and produced a light beam of 10–14 mrad divergence. It was found that a fiber with a silvered end influenced the spectrum and the intensity of the laser radiation.