Micro-optical bench technology using ultra-precision milling

There is a strongly growing market in the field of optical and electro-optical modules, which generates a high demand for module superstructures in the coming years in the field of tele- and data communication, lighting, measurement technology, and material machining. Recent processes for the manufacture of carrier substances for opto-electronic components and micro-optics, like used in telecommunications for the setup of photonic modules (for instance transmitters, receivers, filters, amplifiers, dampers, and MOEMS) are based on processes of the semiconductor industry like wet chemical anisotropic etching in mono-crystalline silicon or dry etching processes in glass or silicon. Since a cost-efficient production requires a passive alignment of micro-optical components, tolerances in the range of 0.5 µm to 1.0 µm have to be guaranteed. Furthermore, metallically structured carriers are necessary to thermally discharge high performance densities. For prototyping of optical subassemblies (OSA) and special module sub-mounts a new concept has been developed and proved. In the preparation of the mass production of semiconductor modules, the manufacture of function-prototypes is an indispensable step towards the assessment of the future functionality. With the help of ultra precision machining, components and sub-systems can be manufactured in small batch sizes. A redesign is possible by changing the CAD data and can immediately be realized on the machine. Thus, costs in the engineering phase are considerably reduced (Rapid Prototyping). This technology allows manufacturing of structures such as V-grooves, as well as cavities with conical, pyramid, or square transverse sections with a geometrical accuracy of sub-micrometers and, if necessary, with an optical surface quality, allowing optical functions. This technology is also suitable for the manufacture of small batches to some 10 pieces. For some application (medicine, sensor, security) there is a demand for such small quantities but special properties, for example high power laser sub-mounts to allow very efficient heat dissipation by means of other materials then silicon or ceramics. Materials used are metals such as brass, German silver, but also semiconductor materials, ceramics, and glass. This paper presents the results of milling operations with mono-crystalline diamonds in copper, German silver, and silicon. Furthermore the micro-packaging concept and functional results for a Transmitter-Prototype are presented and discussed.