This chapter first discusses the development of an SOI–SOI wafer bonding process to design and fabricate two-axis scanning mirrors with excellent performance. These mirrors are used to steer laser beams in free-space optical communication between UAVs. In other words, one- and two-axis scanning micromirrors have been fabricated in an SOI–SOI wafer bonding process, which shows great promise in meeting the specifications required for secure and reliable free-space optical communication [1].

Second, the chapter covers the fabrication of submillimeter-sized quad CCRs for free-space optical communication. Each quad CCR structure comprises three mirrors micromachined from SOI wafers, and is designed to facilitate manual assembly with accurate angular alignment. Assembled CCRs exhibit mirror nonflatness less than 50 nm, mirror roughness less than 2 nm, and mirror misalignment less than 1 mrad, leading to near-ideal optical performance. The quad CCR incorporates a gap-closing actuator to deflect a base mirror common to the four CCRs, thus allowing their reflectivity to be modulated up to 7 kbps by a drive voltage less than 5 V. This chapter also discusses the demonstration by researchers of a 180-m free-space optical communication link using a CCR as a passive optical transmitter. Quad CCRs have been integrated into miniature, autonomous nodes that constitute a distributed wireless sensor network. The researchers presented an analysis of the SNR of CCR-based ...

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