Approximation of refractive micro-optical profiles by minimal surfaces

The fabrication of refractive optical elements faces the demand of an absolute accuracy of the profile which depends on the wavelength of light. Analogue lithography is a suitable technology for the fabrication of such smooth profiles up to a profile depth of about 10 micrometers . The realization of larger profile depths requires new fabrication techniques. Our approach to solve this problem is to use the similarity of refractive optical surface profiles and certain minimal surfaces. The objective of this paper is to describe design and fabrication of optical profiles which can be realized by combining minimum surfaces and analogue lithography. As a result, with refractive beam shaping elements a wavelength independent conversion efficiency of more than 99% was realized.