Abstract
Novel surface plasmonic optical fiber sensors have been fabricated using multiple coatings deposited on a lapped section of a single mode fiber. UV laser irradiation processing with a phase mask produces a nano-scaled surface relief grating structure resembling nano-wires. The resulting individual corrugations produced by material compaction are approximately 20 μm long with an average width at half maximum of 100 nm and generate localized surface plasmons. Experimental data are presented that show changes in the spectral characteristics after UV processing, coupled with an overall increase in the sensitivity of the devices to surrounding refractive index. Evidence is presented that there is an optimum UV dosage (48 joules) over which no significant additional optical change is observed. The devices are characterized with regards to change in refractive index, where significantly high spectral sensitivities in the aqueous index regime are found, ranging up to 4000 nm/RIU for wavelength and 800 dB/RIU for intensity.
Highlights
Surface plasmon resonance (SPR) has been investigated since the mid-twentieth century using bulk optical components, in particular using the Ottoman Kretschmann apparatus [1]
The majority of the work undertaken in the past relates to two specific types of surface plasmons: the long range surface plasmon (LRSP) [4] and the short range surface plasmon (SRSP) [9]
We report on the fabrication and characterization of SPR fiber devices that use a lapped, D-shaped single-mode optical fiber on which is deposited multiple thin film layers of materials consisting of metals, semiconductors and oxides
Summary
Surface plasmon resonance (SPR) has been investigated since the mid-twentieth century using bulk optical components, in particular using the Ottoman Kretschmann apparatus [1]. It is well known that SPR generation is very sensitive to the polarization of the illuminating light, its wavelength and its angle of incidence on the metal surface. Localized surface plasmons (LSP) display a more complex behavior than LRSP as there are several dependencies, for example on the size, topology and geometries of the plasmonsupporting nanostructures. There is a considerable body of published research relating to optical fibre devices for refractive index sensing [15] with SPR fiber optic sensors being one of the types being investigated [6] due to their high spectral sensitivity to refractive index change in the aqueous index regime [12]. In this paper we provide experimental data of the changing spectral transmission characteristics of the fiber during the generation of nano-scale surface relief corrugation as part of the fabrication process. We illustrate the polarization dependence of these devices and that the plasmon resonances can be tuned using polarization over a wavelength range from the visible to 2 μm
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