Silicon-based micro-optic modulators

Micro-optical modulators allow for temporal and spatial modulation of electromagnetic waves. Requirements for increased modulation bandwidth as well as the need for miniaturization can be met by silicon based modulators. Sophisticated fabrication technologies using advanced materials, designs and actuation principles enable the development of modulators e. g. for microlithography, adaptive optics, endoscopes and projection displays. Two basic fabrication technologies are presented. Starting with a high voltage CMOS process the active backplane is fabricated. Then, a surface micromachining process allows us to generate an array of deflectable micro mirrors with extremely high planarity. Current designs comprise up to 1 million independently addressable mirrors. The properties of the devices which are used as programmable mask for microlithography as well as in adaptive optics are presented. A bulk micromachining technology based on BSOI wafers is presented which allows fabricating 1D and 2D scanning mirrors with an in-plane electrode comb for resonant excitation. The properties of the devices are presented and discussed by means of selected applications. In particular, this is a laser micro camera for endoscope applications with a tip diameter of 8 mm and a highly compact laser projector to display images with a repetition rate of 50 Hz with VGA resolution.