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Sensors 2011, 11(1), 1078-1087; doi:10.3390/s110101078

A Miniature Fiber Optic Refractive Index Sensor Built in a MEMS-Based Microchannel

1,* , 1
1 Department of Electrical and Computer Engineering, University of Massachusetts Lowell, One University Ave., Lowell, MA 01854, USA 2 Biomedical Engineering and Biotechnology Doctoral Program, University of Massachusetts Lowell, One University Ave., Lowell, MA 01854, USA
* Authors to whom correspondence should be addressed.
Received: 23 December 2010 / Revised: 10 January 2011 / Accepted: 12 January 2011 / Published: 19 January 2011
(This article belongs to the Special Issue Optical Resonant Microsensors)
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A small, highly sensitive, and electromagnetic interference (EMI)-immune refractive index (RI) sensor based on the Fabry-Perot (FP) interferometer is presented. The sensor’s FP cavity was fabricated by aligning two metal-deposited, single-mode optical fiber endfaces inside a microchannel on a silicon chip. The mirrors on the fiber endfaces were made of thermal-deposited metal films, which provided the high finesse necessary to produce a highly sensitive sensor. Microelectromechanical systems (MEMS) fabrication techniques, specifically photolithography and deep dry etching, were used to precisely control the profile and depth of the microchannel on the silicon chip with an accuracy of 2 μm. The RI change within the FP cavity was determined by demodulating the transmission spectrum phase shift. The sensitivity and finesse of the transmission spectrum were controlled by adjusting the cavity length and the thickness of the deposited metal. Our experimental results showed that the sensor’s sensitivity was 665.90 nm/RIU (RI Unit), and the limit of detection was 6 × 10−6 RIU. Using MEMS fabrication techniques to fabricate these sensors could make high yield mass production a real possibility. Multiple sensors could be integrated on a single small silicon chip to simultaneously measure RI, temperature, and biomolecule targets.
Keywords: Fabry-Perot; optical fiber sensor; refractive index; MEMS Fabry-Perot; optical fiber sensor; refractive index; MEMS
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Tian, Y.; Wang, W.; Wu, N.; Zou, X.; Guthy, C.; Wang, X. A Miniature Fiber Optic Refractive Index Sensor Built in a MEMS-Based Microchannel. Sensors 2011, 11, 1078-1087.

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