15 March 1998 Fiber optic MEMS pressure sensors based on evanescent field interaction
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Abstract
Micro-opto-electro-mechanical sensors (MOEMS) where optics are integrated with micro-electro-mechanical systems are logical candidates for sensing flow properties in high temperature and pressure applications. MOEMS offer high frequency response, small size, immunity to electromagnetic interference, and resistance to degradation from exposure to harsh environments. Interfacing MEMS sensors with fiber optics is quite challenging. We are investigating novel transduction and coupling methods based on evanescent field interaction and fiber bending methods. An evanescent field, created when total internal reflection between two dielectric media occurs, is an electromagnetic field in the lower index medium. In the case of fiber optics, the evanescent field decays exponentially away from the fiber core/cladding interface. The decay length depends on refractive indices and incident angles inside the fiber. Bringing a foreign object close to the exposed core introduces a change in the effective index and as a result, the transmitted light output is modified. Sensors can also be designed based on the `touching' and `bending' of the fiber optic. In this case, the output light is affected in a linear manner as opposed to the evanescent mode interaction where the sensitivity is exponential. Experimental results obtained regarding pressure sensors for both of these methods are discussed in terms of sensitivity, temperature effect, design parameters, and fabrication techniques.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Massood Tabib-Azar, Massood Tabib-Azar, Boonsong Sutapun, Boonsong Sutapun, Diana Glawe, Diana Glawe, } "Fiber optic MEMS pressure sensors based on evanescent field interaction", Proc. SPIE 3276, Miniaturized Systems with Micro-Optics and Micromechanics III, (15 March 1998); doi: 10.1117/12.302407; https://doi.org/10.1117/12.302407
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