A Miniaturized Sensor Consisting of Concentric Metallic Nanorings on the End Facet of an Optical Fiber

Institute of Information Photonics Technology and College of Applied Sciences, Beijing University of Technology, Beijing 100124, P.R. China.
Small (Impact Factor: 8.37). 06/2012; 8(12):1937-44. DOI: 10.1002/smll.201102290
Source: PubMed


A polarization-independent optical sensor is created by fabricating a concentric gold ring grating with a period of 900 nm on the end facet of an optical fiber. The sensing function of this miniaturized device is realized by sending white light as a probe to the gold rings and collecting the response signal in the back-reflection through the optical fiber. A pronounced peak due to the Rayleigh anomaly of the gold ring grating is observed in the reflection spectrum, the center wavelength of which is sensitive to the change in the environmental refractive index of the fiber end facet. Theoretical analysis not only shows excellent agreement with the experimental results, but also gives insights into the mechanisms of this kind of sensor. Using the center position of the Rayleigh peak as the response signal, a high sensitivity dλ/dn of 900 nm per unity refractive index is realized for this sensor and a resolution of Δn/n ≈ 1% is demonstrated in preliminary experiments. The sensitivity is solely determined by the period of the grating.

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    • "Many works have been done to promote the combination of nanostructures and optical fibers. For instance, fabricating gold ring grating on multimode fiber's end facet to realize refractive index sensing by a pronounced peak caused by Rayleigh anomaly of the ring grating [4], [5]; proposing and demonstrating a flexible optical probe for photonic integrated circuits, which is based on a single-mode optical fiber with a subwavelength-period gold grating on its facet [6]; and fabricating periodic metal dots or nanostructures on fiber facet to form a surfaceenhanced Raman spectroscopy probe or a refractive index sensor [7]–[10]. All of these designs are interesting and attractive, but most of them are based on expensive and low productivity nanofabrication techniques, which make these designs far from practical applications. "
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