Detection of glucose in water solution for several different concentrations has been performed with the purpose to determine the sensitivity of Near Infrared Bloch Surface Waves (lambda = 1.55microm) upon refractive index variations of the outer medium. TE-polarized electromagnetic surface waves are excited by a prism on a silicon nitride multilayer, according to the Kretschmann configuration. The real-time reflectance changes induced by discrete variations in glucose concentration has been revealed and analyzed. Without using any particular averaging strategy during the measurements, we pushed the device detection limit down to a glucose concentration of 2.5mg/dL, corresponding to a minimum detectable refractive index variation of the water solution as low as 3.8.10(-6).
"It is now known that there are surface states on PCs. These surface states were recognized only recently  , and their use in applications is even more recent       . In these states, the electromagnetic energy is trapped on the surface. "
[Show abstract][Hide abstract] ABSTRACT: During the past decade the interactions of fluorophores with metallic particles and surfaces has become an active area of research. These near-field interactions of fluorophores with surface plasmons have resulted in increased brightness and directional emission. However, using metals provide some disadvantages, like quenching at short fluorophore-metal distances, increased rates of energy dissipation due to lossy metals. These unfavorable effects are not expected in dielectrics. In this paper we describe the interactions of fluorophores with one-dimensional (1D) photonic crystals (PCs), which have alternating layers of dielectrics with dimensions that create a photonic bandgap (PBG). Freely propagating light at the PBG wavelength will be reflected. However, similar with metals, we show that fluorophores within near-field distances of the 1DPC interacts with the structure. Our results demonstrated that these fluorophores can interact with both Internal Modes (IM) and Bloch Surface Waves (BSW) of the 1DPC. For fluorophores on the surface of the 1DPC the emission dominantly occurs through the 1DPC and into the substrate. We refer to these two phenomena together as Bragg Grating-Coupled Emission (BGCE). Here we describe our preliminary results on BGCE. 1DPCs are simple to fabricate and can be handled and reused without damage. We believe BGCE provide opportunities for new formats for fluorescence detection and sensing.
[Show abstract][Hide abstract] ABSTRACT: A novel hybrid plasmonic waveguide based on a guided Bloch surface polariton structure is proposed and investigated. This hybrid waveguide overcomes the weak confinement in the Bloch surface polariton structure caused by the diffraction limitation. By introducing a metal stripe near the dielectric ridge located on the periodic multilayer structure that is designed to support a TM polarized Bloch surface polariton, a sub-wavelength scale electric field confinement is realized. The coupling of the Bloch surface polariton and the surface plasmon polariton results in a strong field distribution within the gap between the metal stripe and the dielectric ridge. The variation of the characteristic of the hybrid mode is revealed via tuning the height of the ridge and the coupling distance. Sub-wavelength scale mode size is realized as well as a propagation length of about 100 μm.
[Show abstract][Hide abstract] ABSTRACT: We report on the direct experimental comparison of the sensitivity and figure of merit of biosensors based either on surface plasmon polaritons on metal layers or on Bloch surface waves on one dimensional photonic crystals. The comparison was carried out by making use of a commercial surface plasmon resonance platform that was slightly adapted for these experiments. Although the experimental conditions are not optimized for Bloch surface waves, our experiments demonstrate that both types of biosensors show a similar figure of merit for biochips deposited on low cost molded plastic substrates. For glass substrates with better optical quality, the increased homogeneity of the photonic crystals results in the Bloch surface wave sensors outperforming the surface plasmon polariton sensors by a factor 1.7 in terms of figure of merit. Considerations on the illumination bandwidth indicate options to further increase such a factor.
Sensors and Actuators B Chemical 11/2012; 174:292–298. DOI:10.1016/j.snb.2012.07.015 · 4.10 Impact Factor
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