Franz Mayerhofer

Binary and multilevel diffractive lenses with submicrometer feature sizes

Binary and multilevel diffractive lenses with submicrometer feature sizes are realized on silicon and galliumphosphide wafers using CAD methods, direct write e-beam lithography, reactive ion etching, antireflection coating, and wafer dicing. Measurements prove aberration-free imaging and maximum diftraction efficiencies of 70% for lenses with high numerical aperture (NA) of 0.5. Comparisons to other miniature and micro-optical elements are carried out with respect to laser-to-single-mode-fiber coupling and show the competitive performance of the diffractive lenses. Arrays for 18-channel parallel receiver modules are fabricated in on-axis and off-axis versions. Optical crosstalk is estimated.

Design and fabrication of synthetic lenses in silicon

We report on the design, calculation, and fabrication of binary and multilevel synthetic lenses realized in silicon. The diffractive patterns of the lenses are computer generated, direct E-beam written, and dry etched into the surface of silicon wafers. This paper describes the fabrication tools used and the techniques applied for the lens fabrication. The data processing as well as the efforts necessary for the electron beam writing are emphasized. Binary as well as multilevel elements are fabricated. First results are given for the performance of binary lenses in terms of diffraction efficiency, the efficiency of laser diode to fiber coupling, and the image quality of lenses.

Efficiency enhancement of diffractive optical elements by variable relief profiling

Diffractive optical elements (DOEs) are realized with various reliefs using e-beam lithography and existing methodes for the production of microelectronic components. Depending on the 3D-profile, diffraction efficiencies of more than 70% for DOEs with high numerical aperture of 0.5 were measured and aberration-free imaging was observed. In order to enhance the diffraction efficiency we present different methods for a flexible 3D-shaping of the resist mask for the dry etching process.

Binary and Multilevel Diffractive Elements with Submicron Feature Sizes

Diffractive elements may be identified as miniaturised or micro optical components which affect an incoming beam of light by the laws of diffraction. In contrast to other micro optical components like refractive ball lenses and micro calottes or graded index lenses diffractive optics can be attributed as flat and in general aspheric optical elements which can perform multiple optical functions simultaneously.