Fast 10-µs Microelectromechanical Optical Switch inside Planar Hollow Waveguide (PHW)
A new concept for a 1 × 2 micromechanical optical switch with 10 μs of switching speed, 29 dB of ON/OFF ratio, and insertion loss of −7.22 dB for λ = 1550 nm and −4.96 dB for λ = 635 nm is presented. The idea is to insert a micromechanical switching mechanism composed of a vertical silicon cantilever beam inside a hollow planar optical waveguide structured in a silicon- on-insulator (SOI) wafer. The switching beam in the Y hollow waveguide is electrostatically actuated, which makes it deflect to one side or the other in order to redirect light in one of the two outputs. Switching times of less than 10 μs weremeasured with the produced devices. Compared to classical microelectromechanical systems (MEMS) switches, the concept presents the advantage to decrease the risks of misalignment between the mirror and the optical waveguide, as the two elements are defined in the same process step, and as the mirror position is less critical than for classical MEMS switches. It also limits the optical losses due to beam spreading that occurs in free-space configuration. Three different optical surfaces for the hollow waveguides were studied—a gold coating, an antiresonant reflecting optical waveguide (ARROW) optical coating, and bare hollow silicon.