An optical trapping based microfiber vibration sensor

Abstract

A novel microfiber vibration sensor based on optical trapping mechanism is proposed. In the vibration sensor, a polystyrene microsphere with a diameter of 10μm is used as the mass block. The polystyrene microsphere is enclosed in a sensing cavity filled with refractive index matching liquid. The sensing cavity is composed of a quartz capillary with an inner diameter of 40μm whose two ends are inserted with two optical fibers with an outer diameter of about 40μm. The end surface of the each fiber is fabricated to be a concave tip to generate scattering and gradient forces for trapping the mass block. By adjusting light power outgoing from the two concave tips, the mass block can be suspended at center of the sensing cavity. When a vibration is applied on the sensing cavity, the location of the microsphere will change with the vibration, which results the light power from one tip collected by the other tip also varies with the vibration. The response of the vibration sensor is experimentally demonstrated at frequency range from 15Hz to 1000Hz. The vibration sensor has advantages of simple configuration, small size, light weight as well as good vibration response.