Abstract
We proposed a differential fiber-optic refractive index sensor based on coupled plasmon waveguide resonance (CPWR) in the C-band. The sensor head is a BK7 prism coated with ITO/Au/ITO/TiO2 film. CPWR is excited on the film by the S-polarized components of an incident light. The narrow absorption peak of CPWR makes it possible to realize dual-wavelength differential intensity (DI) interrogation by using only one incident point. To implement DI interrogation, we used a DWDM component to sample the lights with central wavelengths of 1529.55 and 1561.42 nm from the lights reflected back by the sensor head. The intensities of the dual-wavelength lights varied oppositely within the measurement range of refractive index, thus, a steep slope was produced as the refractive index of the sample increased. The experimental results show that the sensitivity is 32.15/RIUs within the measurement range from 1.3584 to 1.3689 and the resolution reaches 9.3 × 10−6 RIUs. Benefiting from the single incident point scheme, the proposed sensor would be easier to calibrate in bio-chemical sensing applications. Moreover, this sensing method is expected to be applied to retro-reflecting SPR sensors with tapered fiber tip to achieve better resolution than wavelength interrogation.
Highlights
We proposed a differential fiber-optic refractive index sensor based on coupled plasmon waveguide resonance (CPWR) in the C-band
We presented a differential fiber-optic refractive index sensor based on film, which can excite CPWR utilizing S-polarized components of an incident light
The bandwidth of CPWR is suitable for differential intensity (DI) interrogation using only a single incident point and dual-wavelength lights
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Aiming to realize DI interrogation using a scheme with a single incident point in the C-band, two different wavelengths of light are needed, and the resonant spectrum should be narrow enough. Compared with the CSPR and WCSPR, the CPWR exhibits a narrower resonant spectrum, which could improve the detection resolution, but for us, the narrow spectrum makes it possible to realize dual-wavelength DI interrogation in the C-band using a single incident point. The sensor head is a BK7 prism coated with ITO/Au/ITO/TiO2 film, enabling CPWR of S-polarized components of an incident light. The experimental results show that the intensities of the dual-wavelength lights vary oppositely within the measurement range from 1.3584 to 1.3689, which demonstrates that it is feasible to use a single incident point to implement DI interrogation in the C-band
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