Optical Networking Best Practices Handbook

7.2. CORNER-CUBE RETROREFLECTORS

Free-space optical communication has attracted considerable attention for a variety of applications, such as metropolitan network extensions, last-mile Internet access, and intersatellite communication [2]. In most free-space systems, the transmitter light source is intensity-modulated to encode digital signals. Researchers have proposed that a microfabricated CCR be used as a free-space optical transmitter [2]. An ideal CCR consists of three mutually orthogonal mirrors that form a concave corner. Light incident on an ideal CCR (within an appropriate range of angles) is reflected back to the source. By misaligning one of the three mirrors, an on–off-keyed digital signal can be transmitted back to the interrogating light source. Such a CCR has been termed a "passive optical transmitter" because it can transmit without incorporating a light source. An electrostatically actuated CCR transmitter offers the advantages of small size, excellent optical performance, low power consumption, and convenient integration with solar cells, sensors, and complementary metal oxide semiconductor (CMOS) control circuits. CCR transmitters have been employed in miniature, autonomous sensor nodes ("dust motes") in a Smart Dust project [2,6].

Fabrication of three-dimensional structures with precisely positioned out-of-plane elements poses challenges to current MEMS technologies. One way to achieve three-dimensional structures is to rotate parts of out-of-plane elements ...