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

Abstract

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.

Surface vs. bulk sensitivity of sensors based on Rayleigh anomalies in metallic nanogratings

“…[7,8] In this paper, we demonstrate that the figures of merit predicted by Feng et al [6] are strictly valid only when a bulk RI change is considered as surrounding medium. This aspect is crucial in order to assess the real applicability of RAs to label-free chemical or biological optical sensors since, in typical scenarios of practical interest, the RI changes are mainly restricted to surface modifications occurring at the sensor interface (e.g., due to the binding of a biological layer, physical or chemical adsorption of analyte molecules).…”

“…Based on the observation that the Rayleigh wavelengths in (1) are sensitive to changes of the surrounding ambient RI, in a recent work, Feng et al [6] proposed a novel sensing scheme based on the monitoring of the wavelength shift of a reflection peak associated with a RA of a concentric gold ring nanograting laid on the end facet of an optical fiber. Among the potential advantages of this type of sensors, the authors highlight the polarization insensitivity (due to the rotational symmetry of the grating), the linear relationship between the RA-peak wavelength and the ambient RI (cf.…”

Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface

“…Such extraordinary beam-steering effect is different from those beam forming or redirecting methods based on active transducer array 25,26 or passive materials 27 (including metamaterials 28,29 ). Potential applications include acoustic switching and surface wave sensing 30 . It is also worth noting that in the non-local regime (the right side of the blue region in Fig.…”

Direct Transfer of Metallic Photonic Structures Onto End Facets of Optical Fibers

“…Nanoimprinting lithography [11,12] and capping with mechanical contact [13,14] are some typical methods for fiber-end-based nanotransferring techniques. We have also demonstrated nano-structuring techniques for sensing and lasing devices [15,16].…”