Figure 3
(a) Ray-tracing illustration of focusing a collimated incident beam using an elliptical surface. The focal distance is F = 1000 cm and the lens diameter is 50 µm. All rays, including paraxial (magenta) and marginal (blue), are focused at the same position. (b) Evolution of the beam dimension (r.m.s.) for the elliptical interface (black) and an approximated parabolic interface (green). |