Optically interrogated micromachined silicon cantilever beam sensor

Silicon micromachining technology has been used to fabricate a silicon cantilever beam vibration sensor. The sensor is optically interrogated using multimode optical fibers which gives the device the added advantages of optical fiber sensors along with those associated with silicon micromachined sensors. The cantilever beam incorporates a channel waveguide which carries the light down the length of the beam. Light exiting the end of cantilever beam travels across an airgap and is recoupled into another optical fiber. As the cantilever is deflected, the amount of coupling changes and is therefore proportional to the amount of force applied to the beam. Modeling of the sensor using both theoretical and computer simulations with commercially available software programs is presented. Also presented are the different fabrication designs and techniques used to build the sensor. Problems encountered in the various steps of the fabrication and solutions chosen are also given. Response of the device to a constant deflection force applied by a probe tip is shown. Measurements of the device's response to vibrations from a shaker table driven by a sinusoidal function with constant amplitude and changing frequency or varying amplitude and constant frequency are also presented.