Axial Beam Shaping with Nonspherical Microoptics

Thin film technologies have been used to fabricate special types of continuous-relief microoptical arrays with extremely nonspherical phase functions for axial beam shaping. Microlenses with Gaussian and double-parabolic profiles are found to generate extended or axially oscillating foci and have also been found to be much less sensitive to the axial position and tilt in comparison with parabolic lenses. The optical properties have been determined in improved experiments. The focusing behavior of the small bifocal microlenses with short focal distances has been investigated with a scanning near-field optical microscope (SNOM). The results of excimer laser drilling of holes in glass using microlenses with two axially separated focal zones are presented. Applications for mode-selection in micro-lasers and axial scanning and switching are proposed.