Fabrication and properties of refractive micro-optical profiles for lenses, lens arrays, and beam-shaping elements

Abstract

An interesting scope in micro optics is the transformation of an arbitrary incoming wave front into another arbitrary intensity distribution. This task includes simple focusing as well as the sophisticated control of the propagation properties of the illumination wave. For the reasons of wave length independence and high efficiency, it is necessary to use refractive elements. The design of these beam shaping elements is made by well-known numerical methods based on wave optics. One technology for the fabrication of refractive micro optical elements is gray tone lithography which is capable of the realization of continuous surface profiles with a total height of up to 65 μm. With the use of gray tone lithography on a preform, even higher profiles are capable of being produced. We fabricated high quality lens arrays and different beam shaping elements. The generation of top-hat intensity distributions with different (non separable) shapes or a line of constant intensity are examples of application. We used a single mode fiber as well as a laser diode and a multi mode fiber as light sources. The illumination waves are Gaussian or Gaussian-like beams.