Chromatic aberration of a nonlinear graded-index-rod lens

Abstract

It is well known that the use of graded index (GRIN) rod lenses provides many advantages over the use of conventional lenses. A nonlinear (intensity-dependent) GRIN rod lens may be the logical evolution of the linear (intensity-independent) GRIN rod lens. With the development of laser technology, nonlinear fiber optics, and nonlinear optical material, researches on nonlinear GRIN rod lenses are clearly needed. A nonlinear GRIN rod lens, for example, an erbium doped GRIN fiber lens, may be fabricated by the current technology. From the reference1, it is expected that the nonlinear coefficient in such lenses may reach 7 × 10-15m2/W or above. This means that low beam power may produce large nonlinear effects in the lenses. Recently, we have studied some properties (imaging and ray path) of nonlinear GRIN rod lenses.2-4 However, to our knowledge, properties of chromatic aberration in such lenses have not been published before. Chromatic aberration is dominant in the imaging system. Our numerical results show that properties of chromatics aberration in a nonlinear GRIN lens are strongly dependent on the beam power and the incident beam waist, which has no counterpart in the linear case and under the geometrical optics approximation.