Compensation of the wavelength dependence in diffractive star couplers

Abstract

Optical systems are described that compensate for the wavelength dispersion that arises in a diffractive fan-out star coupler. Two approaches are investigated, a space-variant one and a space-invariant one. In the space-variant approach an array of diffractive optical elements corrects the wave fronts. In the space-invariant approach a combination of refractive and diffractive lenses compensates for the chromatic focus shifts that are caused by the fan-out element. Examples for such compensating optical systems are presented, along with simulated results. The detailed design for an optimized space-invariant system is described.