MEMS cantilever controls a guided-wave optical switch

Jan 1st, 2001
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Yvonne Carts-Powell

A microelectromechanical systems (MEMS) switch that could replace movable mirror switches for telecommuni- cations applications was described by Ivan Shubin and Patrick LiKamWa at the IEEE LEOS Conference in Rio Grande, Puerto Rico (Nov. 13-16, 2000).

The researchers developed a MEMS-actuated integrated optic switch fabricated on a silicon substrate. The switching action is based on electrostatic bending of a cantilever arm containing two vertically aligned waveguides (see figure). A fixed inner-cladding layer separates the waveguides. When a voltage is applied between the silicon substrate and a 100-nm-thick, 500 × 400-µm-wide chromium electrode, sandwiched between the waveguides, the tip of the cantilever bends down. In this position, light from the lower input waveguide is transferred to the upper output waveguide.

The waveguides are slabs deposited on the silicon dioxide film. Part of the silicon dioxide film is etched to create the cavity below the cantilever. The cantilever beam in the current device is 500 µm long, 80 µm wide, and 6 µm thick.

The pull-in voltage of the device is 25 V. This can be significantly reduced by modifying the cantilever design or by reducing the distance between the electrode and the silicon substrate.

The switch insertion loss is mostly due to the separation between the waveguides. "We used index matching liquid and 4-µm separation to reduce insertion loss to 4 dB," said Shubin.

The switch`s response time is 90 µs. In lifetime tests, the switch has undergone 300 million cycles with no observable functional degradation.

For more information, contact Ivan Shubin at shubin@mail.creol.ucf.edu.

Yvonne Carts-Powell is a freelance science writer based in Belmont, MA.

A 1 × 2 optomechanical switch is shown in the unswitched or parallel state (top) and the switched or crossed state (bottom). (The figure is not drawn to scale.) The length of the cantilever is 500 µm, and its vertical displacement is 3 to 4 µm.

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