A 2D MEMS grating based CMOS compatible poly-SiGe variable optical attenuator

A variable optical attenuator based on a 2D MEMS grating is described. The device is a perforated and suspended poly-SiGe membrane with fixed islands within the perforations. It specularly reflects light in the non-actuated state, whereas after actuation the membrane deflects downwards forming a grating which diffracts light in higher orders reducing the intensity of the specular reflection. Using a laser of 400 nm wavelength, we could obtain an attenuation level of 20 dB with 0.11 dB of polarization dependent loss. A close match was obtained between the experimental and simulated mechanical behavior of the device showing the possibility of efficiently extending its use in the NIR regime. Additionally, as the device is made of poly-SiGe deposited at low temperature, it can be monolithically integrated with CMOS in the future.

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► Novel CMOS compatible poly-SiGe variable optical attenuator.
► Possibility of monolithically integrating the devices directly on top of CMOS.
► Very low polarization dependent loss of 0.11 dB at an attenuation of 20 dB.
► Fast switching speed (∼3.3 μs).
► The first 2D MEMS based grating to be discussed in literature to our knowledge.