We report a novel process technology of hemispherical shaped microlenses, using isotropic wet etching of silicon in an acid solution to produce the microlenses molds. Governed by process parameters such as temperature and etchant concentration, the isotropic wet etching is controlled to minimize various defects that appear during the molding creation. From the molds, microlenses are fabricated in polymer by conventional replication techniques such as hot embossing and UV-molding. The characterization of molds and measurements of replicated microlenses demonstrate high smoothness of the surfaces, excellent repeatability of mold fabrication and good optical properties. Using the proposed method, a wide range of lens geometries and lens arrays can be achieved.

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Many fields of industry are looking for growth from miniaturisation. Because competition is increasing, costs are becoming more important in mass production. These are the driving forces for improving and developing micro injection moulding and replication technologies. This experimental study was carried out to replicate sub-micrometre features using the micro injection moulding technique. For the experiments, polycarbonate (PC) was selected because of its flow properties. The effects of processing parameters on the replication properties were observed. The best replication results were achieved when a small injection piston diameter and large shot size were used in micro injection moulding.

The concept of the fabrication process of glass microlenses integrated with silicon and polymer replicas is presented. These kinds of microlenses are formed using a silicon master which is wet etched in alkaline solutions (anisotropic etching) and/or in acid solutions (isotropic etching). The control of the times and the selection of the solutions, joined with the designs of the mask for conventional photolithography and the quality of the silicon wafers are the key for obtaining the desired shapes and sizes. The fabricated moulds are used to replicate microlenses in polymer by the standard well known replication technologies and also to fabricate glass microlenses integrated on a silicon frame.

An extensive study of the single-step replication of form-birefringent quarter-wave plates is presented. Using rigorous diffraction theory, the fabrication parameters and tolerances are carefully studied in order to obtain ideal conditions for successful replication. The design considerations are then applied to fabricate a master element by electron-beam lithography, and to replicate quarter-wave plates using the UV-moulding process. The measurements show that the replicas behave as high-performance quarter-wave plates for the design wavelength.