Fresnel zones in tapered gradient-index media.
The free propagation of a wave front in an inhomogeneous medium with parabolic refractive-index profile and the division of the wave front into Fresnel zones are studied. We determine the radius and the area of each zone as well as the zone contribution to the total wave at an observation point inside the medium. We find the condition that the optical path must fulfill from each zone to that point so that the disturbance due to successive zones will be in phase opposition. Once this condition is settled the concept of zone plate in gradient-index media is introduced.
Rivas-Moscoso
José Manuel
JM
Departamento de Física Aplicada, Facultade de Física, Escola de Optica e Optometria, Universidade de Santiago de Compostela, Spain.
Gómez-Reino
Carlos
C
Pérez
María Victoria
MV