In-plane MEMS-based nano-g accelerometer with sub-wavelength optical resonant sensor

We have successfully demonstrated a series of results that push the limits of optical sensing, acceleration sensing and lithography. Previously, we built some of the most sensitive displacement sensors with displacement sensitivities as low as 12 fm/root Hz at 1 kHz. Using reference detection circuitry in conjunction with correlated double sampling methods, we lowered the 1/f noise floor to 10 mHz, hence improving the detection limit at low frequencies (10 mHz) by 77 dB to 50 fm/root Hz. We converted these highly sensitive displacement sensors to highly sensitive acceleration sensors through a direct mass integration processes. Our accelerometers have resonant frequencies as low as 36 Hz and thermal noise floors as low as 8 nG/root Hz (where 1G = 9.8 m/s(2)). We have pushed the limits of shaker table experiments to independently verify acceleration measurements as low as 10 mu G/root Hz. Direct measurements with our integrated sub-wavelength optical nano-grating accelerometers have shown device sensitivities of 590 V/G and noise floors corresponding to 17 nG/root Hz (at 1 Hz). (C) 2008 Elsevier B.V. All rights reserved.