Factors affecting the performance of micromachined sensors based on Fabry–Perot interferometry

The noise and performance limitations of optical sensors that utilize Fabry–Perot interferometry detection are investigated. A Fabry–Perot interferometer consists of two partially transparent parallel plates with reflective inner surfaces. The plates form a cavity with an optical resonance that depends on the distance between them. At resonant wavelengths, the incident light energy is transmitted through the sensor and intensity peaks occur. The distance between the plates can be obtained by detecting the wavelength of the transmitted light. Various sensors can be based on Fabry–Perot interferometry, e.g. accelerometers, pressure sensors, and microphones. This paper considers factors affecting the performance of this type of sensor, including mechanical–thermal noise, contribution of noise in the detection system, and effects of reflectivity, surface roughness and parallelism of the mirrors. The presented experimental data support the results of the analysis. (Some figures in this article are in colour only in the electronic version)