High sensitivity optomechanical reference accelerometer over 10 kHz

Abstract

We present an optically-detected mechanical accelerometer that achieves a sensitivity of 100 ng/rtHz over a bandwidth of 10kHz and is traceable. We have incorporated a Fabry-Perot fiber-optic micro-cavity that is currently capable of measuring the test-mass displacement with sensitivities of 200 am/rtHz, and whose length determination enables traceability to the International System of Units (SI). The compact size and high mQ-product achieved combined with the high sensitivity and simplicity of the implemented optical detection scheme highlight our device and this category of accelerometers, outlining a path for high sensitivity reference acceleration measurements and observations in seismology and gravimetry

Applications of cavity optomechanics

“…They have already exhibited a sensitivity of a few 100 ng=Hz 1=2 with a bandwidth greater than 10 kHz, in compact form-factors. 48,49 First, a team at Caltech and the University of Rochester 48 used an on-chip lithographically defined optomechanical "zipper cavity" to measure the motion of a large suspended Si 3 N 4 membrane proof mass (see Figure 4(a)). The "zipper cavity" 28 consists of two parallel suspended Si 3 N 4 doubly clamped mechanical beams, which are a few 10s lm long, less than 1 lm wide, and have a separation of around 100 nm.…”

“…A comparison of the sensitivity vs bandwidth of commercially available accelerometers (see product sheets: MEMS, 93,94 fiber grating, 95 capacitive, [96][97][98] and piezoelectric 99,100 ) and published optomechanical results (purple triangles). 48,49 The semi-transparent halo around the markers has an area which is proportional to typical device sizes obtainable with each technology. For example, the optical fiber-Bragg-grating accelerometer's halo represents approximately 8 cm 3 .…”

“…[37][38][39] Apart from radiation pressure feedback discussed above, [5][6][7]17,24,30 many other feedback mechanisms have been explored such as the photothermal effect, 23 the optical gradient force, 28,29,32,40 stimulated-Brillouin-scattering (SBS), 25,31 electron-hole generation, 41 and non-optical methods such as quantum backaction 42 and coupling to two-level systems. [43][44][45][46] While several high-quality reviews on the background and physics of cavity optomechanics exist in the literature, 1-4 this review instead focuses on exciting emerging practical applications such as high bandwidth and ultra-sensitive accelerometers, [47][48][49] force sensors for magnetometry, 50,51 atomic force microscopy (AFM), 52 testing of gravitational theories, 53,54 low phase noise x-band microwave oscillators, 31,55,56 and optical signal processing such as long on-chip delay lines, [11][12][13] efficient optical wavelength conversion between arbitrary wavelengths, 57-59 optomechanical light storage 60 and tunable optical filters. 29,40,61 Cavity optomechanics is a rapidly evolving field with new applications appearing frequently and hence this review will not attempt to cover every application in detail; but will focus instead on the most promising avenues to-date, which have the highest possibility of finding niche markets outside the laboratory.…”

Highly compact fiber Fabry-Perot interferometer: A new instrument design

“…The focus of this study is the use of EFPI for position or displacement sensors. Applications of this sensing method include atomic force probes [1, 2, 3], accelerometers [4], and, more recently, longer-range displacement interferometry for measuring motion of translation stages [5, 6, 7]. In the absence of focusing or collimating optics, the beam emerging from the fiber will diffract, resulting in angular dispersion of the optical beam with distance from the end of the fiber.…”

A Wideband, Low-Noise Accelerometer for Sonar Wave Detection

“…The noise level of the accelerometer was measured to be 10ng/√Hz at full bandwidth of 200Hz with a dynamic range of 120dB. A wide bandwidth along with sub-μg/√Hz noise floor was reported for an opto-mechanical accelerometer which was developed by Cervantes et al [16]. This optical accelerometer is a combination of a mechanical fused-silica oscillator and fiberoptic micro-mirror cavities.…”